| 1993-'98 Supra Twin Turbo FAQ's |
|
| This FAQ is based on the one
at MKIV.com,
the best source for Supra info online. The original
FAQ is very informative, but there were some things I noticed that could used touched up.
I will add to some of the FAQ's, and create new
ones as well. Text with a dark background is original
text from the MKIV FAQ that I haven't rewritten
yet. You will notice that much of this new FAQ will
be VERY different from the one at MKIV as I touch
it up. |
1.
my tt is currently stock, but i want to improve
its performance. what should i do?
the
twin turbo (tt) responds very well to the following
list of basic performance upgrades (bpu). these
four upgrades are proven to have a high degree of
reproducibility from caar to car:
- Cat-back
exhaust system - this all of the exhaust piping
coming from the downpipe, and includes the muffler
and tip. some brands have a 'silencer' (which
is basically a 1-chamber muffler) sitting about
half way back. most of the major brand name
exhausts are fine, and there are many styles
and sounds out there.
- Downpipe
- this pipe connects the turbo collector piping (which
is a 2 into 1 pipe coming from the turbos' turbine
housings) to the cat-back exhaust system. It contains
2 catalytic convertors from the factory which are VERY restrictive.
Downpipes are available with or without high-flow
catalytic convertors; preferrably without the
'cats' for max hp and spool.
- Boost
controller - either a manual bleeder, ball-and-spring,
or eletronic version will work. You do not
electronic boost controllers w/ fuzzy logic
(e.g.. profec a and hks evc) with sequential
turbos. Most people run either a GReddy PRofec
B (my favorite, has hi/low boost buttons) or
HKS EVC-EZ.
- Fuel
cut controller - GReddy BCC (boost cut contoller
- same thing) tuned to 4.3V is the BEST mod to prevent fuel cut at 14.7psi of boost. HKS's FCD is basically the same
thing as the FFCD (free fuel cut defenser),
which is simply capping off the hose coming
from the turbo pressure sensor...however this
is not recommeded because it TOTALLY blocks
off the signal from the turbo pressure sensor
which affects other engine functions as well.
with
the bpu installed, you can expect to obtain approximately
375-425 rear wheel horsepower (rwhp). you gotta
love the supra tt!!
you will also want to install a boost gauge to monitor
how much boost you are running. obviously running
more boost is going to decrease the life of your
turbos more than low boost, so you will want to
watch this. the #2 turbo quickly comes online from
a slow spin to peak boost (starting around 3800rpm's,)
which can eventually lead to the shaft between the
turbine and compressor wheel becoming warped and
cause the turbo not to boost, make a howling sound
(aka death whine), and spit out oil. some people's
turbos don't last long at all at higher than stock
boost levels, but most seem to take the increased
boost just fine. most people think the best trade
off is no more than 18 psi on a daily basis, although
some have had success and longevity with higher
boost. a conservative number would be to run 15
psi low boost with occasional runs to 17 psi if
you get an ebc that is easily adjustable on the
fly. i have heard of people hitting 29psi max boost
on the stock twins with the hose from the vsv to
the actuator pulled...i hit 28psi twice on a long
straight away in my first 6-speed (with the t-bleeder
still on) one night when I lived at sea level with
air temps around 25 degrees; sideways thru 3rd gear
is pretty insane for stock turbos :) the heavily
boosted #2 turbo died several days later. even with
a supra, you gotta be willing to pay to play...
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2.
how much will bpu cost me?
around
~$2k if you go for the electronic boost controller
instead of using a manual boost controller or a
bleeder valve. not bad, huh? try to get that kind
of serious hp for the money in any other performance
ride!!
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3.
i have a '96-'98 mkiv with the obdii computer. can
i still do bpu?
yes,
they work just fine with the obdii computer. however,
when you install the dp you will get the 'check
engine' light continuously because you are disconnecting
the second oxygen sensor from the catalytic converter. however,
that second sensor has no effect on performance. click
here for how to clear the 'check engine' light. a
dp with high flow cat will accommodate the obdii
o2 sensors and will not alert the mil. alternatively,
you can purchase an
o2 simulator that will trick the computer into
thinking the catalytic converter is still there.
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4.
what is the free fuel cut defenser (ffcd)?
*read
why the greddy bcc is better then the ffcd mod
here
& here.
The free
fcd is basically a low-buck way to bypass the
computer's fuel cut control. this is critical to
maximizing your hp output when your boost levels
go over say, 14-15 lbs of boost. here's how you
do it within 5 minutes and for less than a dollar!! this
modification requires no soldering or tapping into
the harness and is reversible within minutes. please
be aware though that with this mod, you have no
fuel cut. you need to ensure you don't boost too
high! to install the "free" fcd, completely remove
the 4-inch vacuum line that connects the pressure
sensor switch to the "y" connector. (you'll find
the pressure sensor switch on the passenger side
of the intake air manifold on the throttle body
towards the top. the correct sensor is marked "sensor
turbo pressure" in green.) notice that the vacuum
line is attached to the bottom of the sensor switch. leave
the wire connector attached. cap the bottom of the
switch with a 1/8-inch cap. cap off where the 4-inch
hose connected at the "y" with another 1/8-inch
cap. (note: when you slip the cap onto the sensor
turbo pressure, you must make sure not to trap too
much air in the cap. one tt owner had some difficulties
because the sensor thought it "saw" high boost all
the time. just a warning.)
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5. i didn't do the bcc, and now
my check engine light has come on. what can i do?
you need to reset your ecu. see
the faq entry on that topic for details
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6. since i'm upgrading, should
i replace the air intake as well?
dyno results show that mkiv supras with the bpu
and no intake system dyno about the same as those
with either a k&n or a hks super mega flow (the
gain is minimal). higher horsepower cars will benefit
more from the installation of an air intake system. if
you must upgrade, the max air airbox with intake
has been given high praise by several list members. one
upside for some if you get a cone filter upgrade
is you will hear a lot of new noises from your engine
if you like that sort of thing.
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| apu
- advanced performance upgrade |
1. what about the stock fuel
system in the tt? does it need to be upgraded as
well?
the stock 2jzgte twin turbo fuel system is a remarkably
good system straight from the factory. the in-tank
pump, fuel filter, fuel pulsation damper, injectors,
and boost dependent fuel pressure regulator are
all capable of high fuel flow. toyota did its homework
here, as the tt's fuel pump and injectors both max-out
at about the same fuel flow.
fuel
pump:
the stock pump is a denso unit, capable of supporting
up to 450 rear-wheel horsepower (rwhp) reliably. push
it up to 500 rwhp, and you start gambling. go past
500 rwhp, and you are flirting with disaster! the
pump is controlled by the fuel pump electronic control
unit (ecu) located under the plastic panel just
behind the rear driver-side shock tower. the ecu
controls the pump at two different speeds based
on engine load. at low engine loads, the pump is
operating at reduced capacity due to reduced voltage
from the ecu. once you floor it, however, the fuel
pump operates at full capacity. also, the fuel pump
ecu is equipped with a fuel pump system diagnostic
function.
fuel
filter, lines and the "mysterious" fuel pressure
pulsation damper:
the stock fuel lines are a decent size compared
to other cars. there is no need to go to larger
lines unless you plan on making over 500 rwhp, at
which time you will need to rework the whole system
anyway. the stock fuel filter is as good as any
after-market unit. the fuel pressure pulsation damper
is really no mystery. it is simply designed to minimize
the "water hammer" effect in the fuel caused by
the fuel pump's mechanical action and the opening
and closing of the injectors. the damper acts to
absorb these pressure waves in an attempt to extend
fuel pump and injector life. the necessity of this
device, however, is questionable. people have reliably
run up to 500 rwhp on the stock fuel system after
removing this restriction and making sure the rest
of the system is in top shape.
fuel
rail and injectors:
the stock fuel rail and injectors are quality units,
capable of supporting the same HP as the stock fuel
pump. the injectors are rated at 540 cc/min at 41.2
psi of fuel pressure (~550 cc/min at 43.5 psi),
and are a two-hole, side-feed, low resistance design. these
injectors enable the hot injector to be cooled by
its fuel supply, increasing both hot starting and
drivability. push your power past 475 rwhp, however,
and your exhaust gas temperatures (egts) may climb
due to a leaning-out condition. those pushing the
limits of the stock system will need to keep a close
eye on this. it would be a good idea to have your
injector cleaned and balanced if you plan on pushing
500 rwhp on the stock system.
fuel
pressure regulator and fuel tank:
the fuel pressure regulator is a boost-dependent
style. the regulator controls fuel pressure at around
36 PSI above manifold pressure. so as boost pressure
rises, so does fuel pressure. this ensures a nice
consistent differential pressure across the injector
tip which optimizes spray pattern. the fuel pressure
regulator directs all of the excess fuel through
the return lines on back to the fuel tank. the fuel
tank contains both a main fuel tank and a subtank. this
subtank (along with an internal baffle-type design
feature called the "jet pump system") prevents fuel
sloshing, and assists the fuel return flow in providing
an uninterrupted supply of fuel during high-speed
turns and low fuel level conditions, as fuel shifts
from one side of the fuel tank to the other.
fuel
system options:
most people who upgrade their fuel systems are using
either the paxton "signature" series, paxton "kamikaze",
or walbro high pressure fuel pump, depending on
hp goals. couple one of these pumps with a paxton
or earl's fuel filter,-8 or -10 (an size) stainless
braided lines and fittings (earl's, aeroquip), 720-cc
injectors (hks, greddy, rc engineering), and adjustable
fuel pressure regulator (aeroquip, paxton, sx),
and you end up with a monster fuel system capable
of supporting up to 700 rwhp!
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4.
which single/twin turbo kits fits my supra best? their
potential?
take
a look at steve v's turbo
page for great information on a lot (if not all)
of the different turbos out there that can be used
on the 2jz.
RPS
Kits:
TS04:
Most common housings for this turbo are 0.58 and
0.70, it makes about 450 rwhp in the former and
500 rwhp in the latter, spools slightly slower than
stock, and can commonly be used on the stock fuel
system. This is a good turbo if you have an automatic,
and can be daily driven.
T61: Somewhat bigger than the TS04, this
turbo can make 550-600 rwhp. It requires an upgraded
fuel system. This doesn't lag too much, a T61 car
lags a bit more than stock, but is streetable, if
not particularly responsive, could be used for road
racing, not sure if I would recommend this turbo
for a daily driver.
T66: Capable of making 600-675 rwhp, the
T66 is a bigger turbo yet, this is probably as big
a turbo as I would recommend for the street, it
makes full boost right around 4250 rpm on most cars,
a significant amount of lag, but not horrendous...
(full boost being 1.5-1.6 bar) This is a very common
turbo, and a nice setup for drag racing with some
street driving.
T70: Slightly bigger than the T66, the
T70 is probably not a streetable turbo. Lag is a
couple hundred rpm more than the T66, power output
ranges from 650-750 rwhp... perhaps a bit more with
headwork... This is a nice turbo for drag racing.
T72+: These turbos are only good for drag
cars for the most part, lag is far more than smaller
turbos, power outputs are from 750-1000 rwhp.
Twin turbo kit: Using T25/28 ball bearing
turbos, this kit will make slightly more than 500
rwhp, while spooling faster than the TS04 0.70...
very good choice for a street car that needs more
power than BPU.
HKS:
GT2540: These twin turbos are used on the
UPRD supra, and used in single form on quite a few
different cars. Nice turbos, not enormous lag,
maybe slightly more lag than their brethren the
2835s, but they spool a little faster too...I'm
told that car makes power in the 900 rwhp range
on turbo alone, but this could be just a rumor.
GT2835: Probably the most common twin turbos
used on supras, this kit is large, and the turbos
have a fair amount of lag, they make full boost
in the 5000 rpm range, perhaps a bit higher. Very
nice top end on this system, and I've seen power
output in the 700-800 rwhp range fairly consistently
with the right fuel support.
T04R: A fairly large single turbo, this
comes with a pretty big exhaust A/R stock, 0.96...
I would have thought it would be laggy, but my experience
with it shows otherwise... it spools a touch faster
than a T66, but has a bit more power output capability...
it has made power in the 675-750 rwhp range, and
is becoming fairly popular because of this.
T51R: This is HKS's biggest single turbo
that is commonly sold, although it isn't THAT much
bigger than the T04R. Probably in between the T66
and T70 in size, the T04R makes full boost in the
5k range, and none has really been able to realize
its full power potential... I wouldn't be surprised
at seeing 800+ rwhp from a T51R under the right
circumstances... very strong turbo but I wouldn't
use it on a street car personally.
Greddy:
T67: The T67 isn't used on supras very
often, its a TD07-25g turbo, more commonly used
on MR2s... its capable of right around 600 rwhp,
and spools similarly to a T66, so most people choose
to go with either the T66 or T61. Again, on the
upper limit of streetability.
T78: This is one of the more common turbos
used on supras... it makes full boost somewhat past
5000 rpm, but has the potential to make 750+ rwhp...
nice turbo, very good top end once it gets spooled...
lots of drag cars use it, and its fairly inexpensive
now.
T88: Somewhat bigger than the T78, the
T88 has close to 1000 rwhp capability, although
I would imagine it makes full boost close to 6000
rpm, so a built motor is almost a certainty with
this turbo... not too expensive but its not too
usable on most supras so...
Blitz:
Single: The blitz single turbo uses a
K27 turbo and is capable of right around 600-650
rwhp... spools somewhat faster than a T66, and the
kit is well made, but you need to modify it to work
on the US spec supra, pain in the ass to do.
Twins: Supposedly capable of right around
700 rwhp with about as much lag as the single, haven't
really heard too much about it to corroborate this,
but I wouldn't doubt it... kind of expensive, and
this needs heavy modification to work on a US spec
supra.
Others:
TPC: This turbo supposedly has 625-750
rwhp capability with faster spool up than a T66...
don't know enough about it to really say, but the
dyno charts seem to show full boost at right around
4500-5000 rpm, which isn't TOO bad for a turbo with
its power capabilities... not enough people use
it to really say.
Fastrax: Fastrax makes all sorts of custom
turbos... my experience with them is that they make
somewhat more power and spool somewhat faster than
the turbos they were built off of... Fastrax has
allot of experience in the drag racing scene, and
they make high quality products. My Fastrax turbo
supposedly has 750-800 rwhp capability while spooling
slightly faster than a T66... it certainly spools
faster than a T66 in my experience, we'll have to
see how much it puts down on the dyno.
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to start
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5.
what exactly is a/r of a turbo?
a/r
stands for area / radius on the turbine side of
a turbo. area being the area of the turbine inlet
and radius being the distance from the center of
the turbine shaft to the center of the turbine inlet.
this picture explains it perfectly. changing this
property affects the spool-up and overall flow of
a turbo. lower a/r generally reduces spool-up and
maximum flow of a turbo.
|
| engine |
general
description
the 2jz-Gte is a high performance 3.0 liter, inline
6 cylinder engine. it features dual overhead camshafts
(dohc), 4 valves per cylinder, twin sequential water-jacketed
turbochargers with a common charge air cooler (air
to air intercooler). it is a "square" configuration
with equal bore and stroke dimensions. it is also
designed as a non-interference type engine and both
camshafts are driven from a common toothed drive
belt.
its mate, the 2jz-ge, or naturally aspirated (na)
version of the engine, shares the same block casting,
but is fitted with higher compression pistons. the
two head castings are similar as they both must
fit on a common block, but are cast and machined
differently to suit the design requirements of the
two models. the real differences between the two
engines are found in the ancillary systems such
as fuel, ignition, intake/exhaust, cooling, and
of course the turbochargers and their control system.
where similarities or commonality exists between
the gte and the ge engine, they will be mentioned,
otherwise the descriptions below are for the gte
engine.
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1.
what is the difference between an i-6 engine and
a v-6?
the
i-6 Supra engine has all six cylinders "inline". the
camry's and other models in the toyota lineup use
a six-cylinder engine with its cylinders arranged
in a "v" like an american v-8. the supra engine
is a superior design for smoothness, high performance
potential, and ease of modification. sadly, toyota
has decided to phase out their i-6 engines in favor
of the v-6, for economic and space reasons.
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2.
what is meant by "...designed as a non-interference
engine"?
by
definition, if the design of the paths of the valves
and piston causes them to intersect at any point,
regardless of the timing, the engine is an interference
engine. in practical terms this means that if the
camshaft drive system (timing belt) breaks in an
interference engine, and several valves are left
open or partially open, chances are there will be
damaged valves, pistons, and perhaps other components. in
a non-interference engine, if the timing belt breaks,
the engine will simply stop running, but there will
be no damage to it. some honda and dsm engine designs
are the interference type.
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3.
i sometimes hear slight detonation when boosting.
if this is consistent with any type of readily available
fuel, you are probably running too much boost.
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4.
what causes knocking, pinging, detonation, and pre-ignition?
detonation and pre-ignition are about the same thing,
they just happen at different times in the compression
cycle. pre-ignition is either caused by hot spots
that pre-ignite the fuel before the spark plug goes
off or the actual compression of the air/fuel igniting
the mix. remember, when you compress a gas, you
heat it up. that's why too much boost can cause
extra high cylinder temperatures and subsequent
pre-ignition. a lot of people call this detonation,
but it isn't. you can feel pre-ignition, it will
feel like rough power. detonation occurs after the
spark. if the air/fuel ratio is too lean, you don't
get a nice progression of the flame front from the
spark plug towards the bottom of the cylinder. the
burn will be uneven, and you will develop many different
flame fronts going in many different directions. as
these flame fronts collide, they make noise and
you hear the knocking and pinging. more importantly,
the oxygen is going to react with something. better
it react with gas than metal. both of these will
lead to high EGTs. now hesitation can be caused
by both lean and rich conditions. usually by too
rich conditions. you basically flood out the spark
and it doesn't light off the air/fuel mixture. this
will lead to black smoke out the tail pipe and low
EGTs. if you run too lean to get a hesitation, you
will be way past the point that your EGTs should
be sky high. another thing to check is make sure
all injectors are firing. you should be able to
do this at idle by putting a screwdriver on the
injector and the other end butted up against your
ear. or, you can sometimes feel them by putting
the tip of your finger nail on the injector and
pushing a little hard. the vibration is carried
through the bone and you feel it.
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specifications
bore
& stroke of the engine are both 86mm (3.39") giving
a true displacement of 2997cm3 (183in3). The turbocharged
(gte) engine has a compression ratio of 8.5:1, while
the na (ge) engine is raised to 10.0:1 using different
pistons and head configuration. the engine is internally
balanced, has a firing order of 1-5-3-6-2-4, and
produces a maximum horsepower of 320 (sae net) @
5600 rpm, with 315 ft-lbf peak torque @ 4000 rpm.
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1.
i want to have the motor bored & stroked like my
chevy. what's available?
interesting
idea, but there are no big bore kits available,
nor can the engine be bored any significant amount. there
are only two stroker kits (jun and crower), and
these cost in excess of $5000 and only increase
the displacement by approximately 10%. this is very
expensive horsepower...
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features
the engine has an advanced dis type cop (coil on
plug) ignition
system which is crank and camshaft triggered. no
external ignition timing adjustments are available
or necessary. all timing adjustment is made electronically
by the engine management system (ems) according
to internal 3d ignition maps. two knock sensors
are provided and timing is retarded by the EMS when
knock is sensed.
fuel delivery is by a sfi
system with both pulse rate and fuel pressure
adjusted according to load demand by the engine
management system.
intake air is measured before the turbochargers
by a hot-wire type, mass
airflow (maf) meter. this measurement is then
compensated for temperature & barometric pressure
(altitude) in the engine management system.
all systems are controlled by an integrated engine
management system consisting of a main engine
control module (ecm) and several peripheral
electronic control units (ecu) for the ancillary
systems.
all aforementioned systems are described/discussed
in more detail in later sections of this faq.
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1.
what spark plugs should i use?
stock vehicles respond very nicely to factory toyota
plugs, gapped to toyota specs. of .043". if you
have a tt or single-turbo Supra and run higher than
stock boost, or if you notice a high-rpm miss, you
may want to consider reducing your plug gaps until
the miss goes away. there is still debate about
whether to switch to another plug at bpu levels,
but single-turbo supras will probably benefit from
a plug one heat range cooler than stock. many bpu
owners have switched to plugs one heat range cooler
than stock also such as NGK 3330, 1095, 6097, and
1283. these four are described below.
to begin with...stock plugs on the supra are the
NGK BKR6EP-11, which is defined as:
BKR6EP-11: B = thread diameter of 14mm, K = construction
type: hex size 5/8" w/ ISO projection tip, R = resistor
type plug, 6 = heat range #6, E = 19mm (3/4") thread
reach, P = platinum-type plug, -11 = x/10 - 1.1mm
pre-gap (0.044")
now keeping that in mind, (in what the car calls
for, and specs it requires) now lets compare the
BCPR7ES(-11) 1095/3330 and the BKR7E(-11) 1283/6097 plugs:
(1095) BCPR7ES-11: B = thread diameter of 14mm,
CP = hex size 5/8" w/ projected insulator (which
is out-of-spec), R = resistor, 7 = heat range #7, ES
= standard 3/4" thread reach w/ 2.5mm diameter center
electrode (which is prone to misfires), -11 = x/10
- 1.1mm pre-gap (0.044")
3330 is simply the BCPR7ES w/out the 1.1mm pregap
(therefore gapped at 0.0315")
(1283) BKR7E-11: B = thread diameter of 14mm, K
= construction type: hex size 5/8" w/ ISO projection
tip, R = resistor type plug, 7 = heat range #7,
E (stand-alone digit) = v-grooved center electrode
w/ 1.5mm diameter electrode.
6097 is also the BKR7E w/out the 1.1mm pregap (0.0315")
the 1283/6097 (BKRxE) plugs are pretty much the
same specs as stock, but one heat range Colder,
as well as non-platinum in a copper-core form. the
center electrode, as compared to the 1095/3330 is
also 1mm smaller in diameter as well as have a v-groove. the
smaller the diameter of the center electrode, the
better the spark flow. (less chances of misfire) think
of the spark traveling through the center electrode
as a water traveling through a small/steady stream,
as opposed to some wide stream w/ wild rapids and uncontrollable
tides. the v-groove also furthermore helps the spark
by directing the sparks toward the edges of the
electrode, closer to the a/f mixture for the best
ignition possible.
if you ever have the chance, try laying down a oem-spec
plug... along side with the 1095/3330, and you'll
notice the physical difference. although they "may"
work, it is not the correct plug for the car. the
BKR-construction plugs are the way to go on the
supras (and not the BCP-construction plugs, which
are designed more towards Hondas which require a
longer insulator), and brian weaver at ngk tech
will also agree with me.
the main reason people on this list use 1095's (and
also 3330's) is that they are more readily available
to the public. many napas, and even pep boys stock
them and can also get a hold of them if necessary. the
1283 and 6097's on the other hand, wont even show
up on many stores' ngk parts list! the only means
of obtaining these plugs would be through NGK directly,
or by calling their main distributor (monarch) at:
888-800-9629 (outside california) or 909-672-8501
(within california).
now that you've read all about those plugs, you
might also want to try denso iridiums. they are
pretty expensive, though. but they are also a platinum
tipped plug and won't need changing every 3k-6k
miles. they seem to work well for many in both bpu
and higher hp applications.
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2.
i'm using stock plugs, and my car isn't running
quite right.
one of the reasons that stock plugs sometimes do
not respond well to the added cylinder temperatures
created under higher boost conditions is the fact
that the plugs were designed to run with longer
spark plug noses and longer ground strap. a longer
ground strap dissipates heat slower and therefore
can contribute to detonation. typically the missing
that many experience on higher boost is not because
of the heat range of the plug, but because the gap
is too wide. it should be noted that denso and ngk
plugs such as those supplied with oem cars are designed
to operate with a specific gap width (or length),
and not smaller gaps. you may need to reduce the
gap on your stock plugs or switch to a colder plug. see
question 1 above
for a list of ngk plugs people have had success
with.
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3.
i want to replace the spark plugs on my supra tt.
what are the steps?
- buy
6 new spark plugs from toyota (toyota part number
# 90919-01178) or by choosing from section 1
above. also buy 2 crankcase hoses, toyota part
number 12263-46010 & 12264-46010 (if needed)
- with
allen wrench (5mm) remove top cover of engine,10
screws.
- remove
the two crankcase vent hoses that run between
the valve covers.
- using
small screwdriver, release the wiring harness
clips.
- unbolt
the ignition coils (coil packs). there is a
10mm bolt on each side. there are 3 coil packs.
- disconnect
wiring from the coil packs. two connectors per
pack.
- lift
out coil pack.
- use
deep well 5/8th socket to remove plugs.
- gap
(if needed) and install the new plugs (torque
it to 13 ft/lbs). stock plug gap is .043 or
1.1mm, for bpu try stock gap or a lower setting
like .035 if your engine is missing.
- install
coil packs... make sure you have a good seal
on the plug.
- connect
wiring and re-clip wiring harness(2) to clip. make
sure each harness routes *below* the crankcase
vent.
- install
crankcase hoses that you bought (or previous
ones if they are not cracked).
- re-install
cover.
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4.
how can i read my sparkplugs?
this is covered in the tech section. click
here to go directly there.
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5.
the engine misses at high boost.
try re-gapping original plugs or new plugs at .026"-.035". start
high and work your way down until it stops missing.
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6.
how do i check the engine trouble codes?
for cars with obd1 (93.5 - 95)
turn the ignition switch on. connect a wire between
te1 and e1 in the diagnostic
connector. supras have two diagnostic ports. one
inside the car under the dash (driver side), and
one under
the hood. if everything is okay the light will
flash on and off steadily. if there is a problem
it will flash in a sequence that will decipher to
a number that relates to a specific fault. for more
information about reading these codes click
here.
for cars with odb2 (96 - 98)
use an obd2 scanner to read the code. the connector
is located under the dash by the left knee of the
driver.
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cylinder
head & valvetrain
the cylinder head is a single casting of aluminum
alloy with two camshaft/valve covers and a central
coil/plug cover. combustion chambers are pentroof
design with valves angled at 45 degrees away from
each other. the spark plugs are mounted near the
centers of the chambers.
both intake and exhaust valves are made of tempered
steel with nitrided stems and valve faces which
have been bonded with cobalt alloy for good wear. the
valves run in replaceable guide bushings and have
replaceable stem seals. single valve springs are
employed which are held in place by split keepers
and steel retainers, steel spring seats are also
provided. valve lash adjustment is by "bucket and
shim" type lifters fitted between the valve stems
and camshafts. the intake valves are 33.5mm (1.32")
in diameter and are lifted 8.25mm (0.325") by their
camshaft. exhaust valves are 29.0mm (1.14") in diameter
and are lifted 8.40mm (0.331") by their camshaft.
the intake camshaft is fitted with special timing
lobes for the dis ignition and sfi systems. the
intake camshaft opens the valves 3 degrees btdc
and closes them 50 degrees abdc. the exhaust camshaft
opens its valves 52 degrees bbdc and closes them
4 degrees atdc. each camshaft is held in place by
seven heat-treated, unbushed bearing caps.
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1.
what does dis
mean? is it an abbreviation for distributor?
dis is an acronym for "direct ignition system" and
generally means a distributorless, crank triggered
ignition.
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2.
how about sfi?
sequential fuel injection. some electronic fuel
injection systems called mfi cut corners by injecting
into multiple cylinders (3 groups of 2 cylinders)
simultaneously - the mkiii supra used such a system. the
mkiv supra on the other hand, "can" control fuel
into each cylinder individually.
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3.
how can i do a cylinder leak-down (clt) test?
- basically,
a cylinder leak-down test consists of pressurizing
a cylinder with shop air and listening for leaks. fashion
an adapter from an old sparkplug so you can
hook up an air hose from your air compressor. rotate
the engine until the cylinder to be tested is
at tdc compression. be sure to get it exactly
on tdc. next slowly turn up the air pressure
regulator on your air compressor or slowly open
the supply valve to pressurize the cylinder. go
slow because the engine may try to spin - keep
hands and tools clear of belts, etc. once the
cylinder is fully pressurized listen for air
leaks. do not confuse a "seashell" sound for
a leak. air leaks will be very distinct sound
and you may even feel a rush of air. open the
throttle and put your ear next to the intake
opening. a rush of air indicates a leaking intake
valve (bent valve? misadjusted or sticking?). next
put your ear to the tailpipe opening, air rushing
out means a leaking exhaust valve (bent, misadjusted,
sticking, or burnt?). listen at the oil filler
cap. you will hear a slight hiss of air. this
is normal 'blow-by' leakage. how much is normal? well,
many clt tools have a flow meter to measure
how much air is coming by the piston rings and
out thru the oil filler cap. usually less than
15%. you probably don't have an air flow meter
to hook in-line with your air hose, so instead
try to remember what each cylinder sounded like
and compare them to one another. engines with
good compression and good rings will sound even,
slightly louder than a 'seashell' and you will
not feel any air rush. lastly, take the radiator
cap off and look for bubbles. bubbles indicate
a blown head gasket or maybe a cracked cylinder
head. doing a clt along with a compression test
will tell you a lot about an engine's condition.
-
a number
of people have asked "What is a LEAK DOWN
test?" and "Can I do it myself?". first, let
me explain the concept. we already use a compression
test to determine an engines condition. The
problem with this test is that there are too
many variables. it can only be used to check
engine condition by comparing cylinders to
each other or a past norm. variables such
as cam profile, engine cranking speed etc,
will affect the readings.
a leak down
tester uses air from a compressor and measures
the rate at which it leaks through the engine. this
is done with the engine not running and the
beauty of this is that toy can find the source
of the leakage by listening for the escaped
air. internal leakage is found by air bubbles
in the cooling system. tools need are a leak
down tester and an air compressor. the tester
is available from Milton at about $60.00. compressor
should be at least 2hp and deliver 90psi.
procedure:
remove spark plugs. set engine to tdc #1. calibrate
test gauge per the instructions. Lock engine
so it can not turn. connect hose to spark
plug hole. connect pressurized gauge to hose
connection. read leakage. if looking for coolant
leaks and nothing obvious shows up, bypass
gauge and connect shop air direct to cylinder. open
radiator cap before this. if coolant sprays
out, you have a head problem. do same test
on rest of cylinders. remember to set tdc
of each piston for compression stroke. this
test is also great for air cooled head leaks
and valve problems. note that all engines
will have some leakage past the rings. i always
do full pressure test when i suspect a problem. make
sure engine is secured with full pressure
test. it will spin violently. with gauge connected,
you can rock crankshaft to see if leakage
changes. if so, this is a sign that the ring
lands are wearing, new engines will also do
this until the rings are seated.
i know these
instructions are kind of flaky, but I hope
this gives some insight as to this type of
test. if having a mechanic work on your vehicle,
he should be familiar with the leak down test. i
would be concerned if he isn't. this is a
basic troubleshooting tool that all fleets
use. especially on diesels.
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block
the cylinder block is a single iron casting without
lined cylinders. it has seven massive main journals
with two bolt main caps. accessory bosses have been
cast into the block to allow direct mounting of
the alternator, starter, A/C compressor, and other
accessories. with only minor machining differences,
both the GE and GTE engines share a common block
casting.
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1.
i thought the supra was a
high performance engine. why doesn't it have four
bolt mains like a camaro?
first reason is that the main journals in the 2jz
engine are absolutely massive. they are some of
the biggest mains you'll ever see in an automotive
engine, so block flex is not an issue as it is with
domestic blocks. second reason is that the 2jz crankshaft
is already a precision balanced component with twelve
counterweights. as such, it does not require extra
restraint or externally balancers. third reason
is that with the inline configuration of this engine
there are seven main journals taking the load, not
just five as there are with domestic v-8 engines. in
summary, the box stock lower end of the 2jz engine
is nearly indestructible and is capable of delivering
well over 900 horsepower reliably to the rest of
the powertrain. it was "designed" as a high performance
engine, not modified to be one.
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pistons
& rods
pistons are an aluminum alloy and have two compression
rings and one oil control ring. the first compression
ring and the oil control ring lands have been
nitrided for durability. the second compression
ring has been chrome plated and the piston skirt
has been resin coated to reduce cylinder abrasion. an
oil gallery has been cast into the piston and
as oil from the oil jets is sprayed onto the underside
of the crown, oil circulates within this gallery
and cools the piston.
the same forged connecting rods are used in both
the ge and gte engines, employing press fit pins
with retainers on the small ends and replaceable
rod bearings on the crank end. oil jets are provided
on the large end for directing oil onto the underside
of the piston crown for better cooling.
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1.
are aftermarket forged
pistons and rods a good idea?
the sellers of these components think they're
an excellent idea! in reality, the stock supra
pistons are as advanced a design as any aftermarket
piston, and the rods are already forged. the stock
reciprocating assembly "can" hang together just
fine up to 8000-8500 rpm (although we're rev limited
to 6900-7200) and can produce insane power levels. however,
to be fair to the aftermarket, there are some
weight savings and strength increases to be gained
with aftermarket rods and pistons, but these become
advantageous only when the engine is being prepped
as a full race engine.
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crankshaft
& torsional damper
the forged steel crankshaft incorporates twelve
counterweights and seven main journals; the main
and rod journals are induction hardened. replaceable
aluminum alloy main bearings are used.
a dual mode torsional damper is fitted to the
front of the crankshaft. this is NOT an external
balancer, as the crankshaft is fully balanced,
rather it dampens both the axial twisting couples
produced by the firing pulses, and the radial
bending moment from the accessory drive belt.
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1.
can I pull the harmonic balancer
off, replace it with an underdrive pulley and pick
up 10-15 horsepower?
first, it's not a "harmonic balancer". it's a torsional
damper. second, it is NOT a good idea to replace
it with a solid underdrive pulley.
torsional analysis of a reciprocating engine is
an extremely complex, computerised study and design
of a system to smoothly and safely transfer 20,000
explosions per minute into useable torque without
destroying the engine or drivetrain. oh, and do
it for the life of the car. without exception, every
reciprocating engine, pump, or compressor can benefit
from torsional damping, but getting it right is
an extremely complex process, and the consequences
of getting it wrong are broken crankshafts and/or
ruined drivetrain components. so in summary, this
is NOT a good area to try to pick up cheap horsepower
on the supra unless you are prepping a full race
engine and plan to rebuild the engine and drivetrain
on a semi-regular basis.
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lubrication
system
the engine lubrication system consists of a wet
sump, pressurized system with a crankshaft driven
gear type pump, spin-on oil filter, and a water
jacketed lube oil cooler which is built into the
oil filter adaptor housing. the engine oil pan is
actually two pans, an upper and lower unit, neither
of which can be easily removed without either lifting
the engine from its mounts, or removing it entirely
from the car. there are dual oil supply galleries
in the engine which supply the cylinder head, crankshaft,
piston oil jets, and the turbochargers with pressurized
oil. pressure relief valves are fitted to the oil
pump, filter and oil cooler. if oil pressure at
the discharge of the pump is too high, its pressure
relief will open and relieve pressure back to the
suction side of the pump. if either the oil filter
or the oil cooler become plugged, their pressure
relief valves will open and allow oil to bypass
around them. in this way, the system is both protected
against overly high pressure, and oil flow is always
assured to the main gallery.
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1.
which type/brand of oil
and filter should i use for the mkiv tt engine?
turbocharged car owners generally favor pure synthetic
or synthetic blend oils over dino oils. synthetics'
shear and anticoking properties at high temperatures
are ideal for protecting turbocharged engines. any
synthetic of the proper weight will do. don't
get hung up on brand names. if your tt has a new
engine or fresh short block, allow 5,000 miles
for break-in with dinosaur (mineral) oil before
changing over to synthetic oil. the "dino oil"
helps seat rings, seals, etc. generally stick
with toyota's specification of 10w-30. however
in cold climates, a change to 5w-30 may be warranted
during the winter. be aware if you have a high
mileage supra and switch to synthetic, your oil
consumption will probably increase. despite synthetics'
other very desirable qualities, some supra owners
have found that certain brands of synthetic are
not as friendly to valve stem seals as dino oil,
and may actually accelerate wear in this area!
toyota make an excellent stock filter for the
supra, and an even larger capacity filter is available
with the same construction for the land cruiser
or lexus, and these are good upgrades for the
supra - the toyota p/n for these is 90915-20004.
In the aftermarket, Amsoil make a very good filter,
as do k&n. stay away from the bargain store brands
that are on sale for only two or three dollars. this
is not a good area to save money.
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2.
how often should i change
my oil?
the critical question that has no hard & fast answer. it
just depends.... how often is the car driven, and
"how" is it driven? is the engine modified, is the
car raced, etc. the best answer is "somewhere" between
2500 miles and 10000 miles per oil change. 2500
miles if the car is raced, and/or does lots of stop
& go driving or quick trips to the grocery store,
or if you operate the engine in a very hot or dusty
climate. if, however, you clock a hundred miles
of driving each day at freeway speeds, and the engine
is running at normal operating temperatures and
NOT at peak output for several hours, extended oil
changes are certainly possible with synthetic oil
AND regular oil analysis. in summary, frequent oil
changes are sometimes seen as a waste of good oil,
but they're a good insurance policy for you and
your engine if you don't have an established oil
analysis program and don't know exactly what's going
on with your oil.
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3.
is it difficult
to change the oil? how long should it take?
it isn't difficult, but the first time you do
it, set aside a couple of hours to complete the
task and be prepared to get messy. after you have
done it once or twice, it should only take about
20 minutes and you'll have figured out how to
do it with less mess. while you have the car up
on stands, it's a good opportunity to check over
the entire undercarriage and check the torque
on the suspension mounting points both front and
rear.
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4.
what specification and oil
weight should i use?
the list members have personal preferences. for
fastest turbo spooling and maximum horsepower, stay
with the recommended 10w-30. heavier oils can be
used, but they will make the engine warm up slower,
run hotter, and lose more horsepower to fluid friction. in
very cold climates, a switch to the same oil in
a lighter range, such as 5w-30 will improve starting
in the winter.
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5.
aren't all engine oils basically
the same?
no! conventional and synthetic oils are as different
as day and night in performance. you can't beat
any pure synthetic with a conventional (mineral)
or conventional/synthetic blended oil. the pure
synthetic wins, hands down, in any performance comparison
except price.
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6.
how can i know if my oil
is not performing?
the old mechanics' practice is to wipe the inside
of the oil filler cap with a clean rag. if there
is a visible brown deposit on the metal surface,
they'll say it's time for an oil change. this isn't
really a valid test, but no one has ever ruined
an engine with too frequent oil changes, where the
opposite is certainly true! the best way to know
about your oil's performance is to establish a regular
oil analysis program, which involves taking samples
of the oil periodically to an oil analysis lab,
and they'll tell you exactly how the oil is performing.
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7.
how important is it for my
turbos/engine to use the right oil?
superheated oil exiting the turbo bearings sometimes
looks like a chocolate mousse. this is why the turbos
have a water jacket to help cool them. a turbocharger
puts extreme stress on oil, and the oil is the only
thing in your engine separating metal-to-metal disaster. again,
bargain basement or generic brand oil is not a wise
idea.
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8.
when to switch to synthetic? what
kind?
you can switch to synthetic as soon as break-in
of the engine is complete. ordinarily this will
be somewhere between 2,000 and 4,000 miles. if you
have taken the engine to maximum load (top speed
for more than 15 seconds), regardless of mileage,
break in is complete. list members have varying
experience with mobil 1, sastrol syntec, redline,
and amsoil. they are all very good, some have advantages
over the others in terms of availability, price,
and small performance differences.
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9.
what is the best way to change
the oil on my mkiv?
to change the oil, first get the engine to normal
operating temperature by going for at least a 20-30
minute drive. when you get home, put the car up
on ramps or stands, make sure it's in park or in
gear, and the emergency brake is set, open the hood,
remove the oil fill cap, and then get underneath
and remove the drain plug. it goes without saying
that you should anticipate which way the oil is
going to pour out and have your drain pan positioned
and NOT have your hands, arms or face anywhere near! after
the hot oil has drained out, replace the seal washer
on the drain plug with a new one and tighten it
snugly, but be careful not to overtighten. although
the lower pan is steel, it's also thin. now to remove
the filter, for the '93-'95 models, if you're removing
the filter from underneath, it's sometimes necessary
to remove the suspension strut that attaches to
the lower a-arm, and the plate that is mounted just
above it. if you're a contortionist and have small
arms and hands and the proper tools, it's "just"
possible to remove the filter from above. next,
put some kind of catch towel up underneath the oil
filter to catch the oil that is going to spill when
you first start to remove the filter. then, using
a filter wrench that fits over the end of the filter,
remove the old oil filter. if you have some time
to spare, it's usually better to let the engine
cool for a half hour or so before you do this to
avoid burning your arm with hot engine oil. wipe
the filter mounting surface and block sealing surfaces
with an oily rag, and spin it on and tighten snugly
by hand. now, fill the crankcase with 5 u.s. quarts
of oil. start the engine and watch the check lights
to make sure you have oil pressure, then check for
leaks around the filter. if everything is ok, then
check your oil level and adjust it to indicate at
least halfway between the f and l marks on the dipstick.
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10.
a "quickie lube" place changed
my oil and wanted to put in an additive. they said
my engine would get 30% better gas mileage and make
at least 20% more power.
oil additives are the "snake oil remedies" of the
automotive world. many additives are available with
very extravagant claims. there are numerous reputable
articles available on additive performance, and
they are all negative. in short, it is not recommended
to add anything to your oil; as competitive as motor
oil sales are, if a worthwhile additive were developed
and became available, the major oil companies would
be scrambling to include it in their products.
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11.
where can i learn more about
oil?
there are many technical articles on oil available
on the web, see the mkiv tech references for some
of the better ones.
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12.
why does my oil look dirty
when i check my oil level?
all automotive motor oil contains detergent and
dispersant additives which will hold oil degradation
and by-products of fuel combustion in suspension. in
short, a dirty oil is doing its job. the oil is
designed this way to prevent these contaminants
from depositing on engine surfaces where they can
cause piston rings to stick and plug oil pump screens. the
oil works in conjunction with the filter to remove
these contaminants
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13.
my front crank seal blew out. why?
neither the root problem nor the solution is known.
(the crank seal blows on some cars with stock rev
limiters.) but one possible cause/solution that
has been theorized and tried is that at higher than
stock rev limits, the stock oil pump cannot relieve
enough pressure as it spins faster. as a result,
oil pressure rises too much and blows out the seal.
modification to the stock oil pump is required to
ensure that it won’t happen again.
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cooling
system
the engine uses a sealed and pressurized, forced
circulation cooling system, consisting of a belt
driven pump, radiator and a cooling fan which is
fluid coupled to the pump. coolant temperature is
controlled at the inlet side of the pump by an integral
wax element thermostat. the thermostat modulates
coolant flow between a bypass line and coolant coming
from the bottom tank of the radiator. when the engine
is cold, the thermostat blocks the passage from
the bottom tank and coolant circulates in a loop
through the engine and bypass line only; it does
not circulate through the radiator. as the engine
warms up and reaches the thermostat temperature,
the thermostat opens and allows coolant from the
radiator bottom tank to mix with hotter coolant
from the bypass line. by modulating between these
two lines, the thermostat controls the temperature
of the coolant going into the engine. once inside
the block, the coolant flow splits and part circulates
through the block and the rest goes into the cylinder
head and ancillary systems. coolant return from
the block splits again and goes into both the heater
system, the oil cooler, and thereafter back to the
pump suction. coolant return from the cylinder head
splits and goes to both the throttle body and the
turbochargers, and from there it returns to the
pump suction.
while the actual flow rates of the pump are not
known, adequate flow is provided at all RPMs and
normal loads to limit temperature rise out of the
engine to an ideal 10-12 degrees F under normal
conditions. the stock radiator is adequate for casual
driving at stock power output, but at higher engine
outputs and/or extended high speed racing in warmer
climates, the stock radiator cannot cope with the
increased load and should be upgraded.
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1.
how do i know if my coolant
needs changing?
use a voltmeter, and attach the ground lead to the
battery negative or the engine. then put the positive
lead in the coolant at the radiator cap. it should
measure less than 0.500 vdc, and ideally should
be 0.100 vdc. more than 0.500 vdc is very bad and
the coolant should be changed immediately.
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2.
which coolant should i use?
toyota's red coolant is best, in a mix that is proper
for your climate. "green" coolant usually has silicate
additives which were formerly promoted as helping
cooling efficiency. this is not so, and these additives
will reduce cooling efficiency in our engine, and
in extreme cases may plug small coolant passages.
only use toyota's red, or other reputable ethylene
glycol coolant "without" silicates or other additives.
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3.
what's the proper mix of coolant and water?
some owners in very mild climates use as little
as 15% coolant to 85% distilled water with a bottle
of redline's water wetter to help reduce cylinder
head temperatures and provide water pump seal lubrication.
water-wetter is highly recommended. it has helped
produce measurable increases in gas mileage with
reformulated gasoline. reduction of cylinder head
temps allows more ignition advance before onset
of knock, and more ignition advance is conducive
to better fuel economy.
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4.
why distilled water?
tap water contains varying amounts of minerals and
ions, as well as chlorine and sometimes heavy metals.
also the pH of tap water may vary from acidic to
very base. the minerals in the water will deposit
themselves in the cooling passages of the engine
and radiator, and eventually build up and reduce
the efficiency of the system. worse than this however,
the minerals and ions may react chemically and electrically
with the aluminum and copper components in the cooling
system, and set up an electrochemical process known
as bimetallic corrosion which will actually accelerate
the failure of these components. this process can
be detected with the voltmeter test described above,
and if a voltage higher than 0.500 VDC is detected,
a very damaging bimetallic corrosion process is
at work eating away your cooling system! distilled
and deionized water contains no minerals, heavy
metals or chlorine, and has a neutral pH, so it
is the best fluid for your system.
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5.
why is such a low concentration
of coolant recommended? i always thought that a
50/50 mix of coolant and water was the best protection
for my cooling system.
maybe it's the best protection if you want to store
or drive your supra safely at -40 degrees fahrenheit,
but it's not the best mix to help your cooling system
get rid of the engine's heat. first, understand
that water is absolutely the best heat transfer
fluid commonly available - bar none. all other heat
transfer fluids can "carry" only fractions of the
heat that pure water can. the effectiveness of a
fluid's ability to "carry" heat is called its "specific
heat capacity". for example pure water has a specific
heat capacity of 1.0 and pure glycol (coolant) has
a specific heat of 0.6. mix them in equal proportions
(50/50 mix) and you have a fluid that will perform
only about 80% as well as pure water in carrying
heat away from the engine to the radiator. a 15/85
mix will perform 94% as well as pure water, or to
put it another way, about 14% better than the 50/50
mix.
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6.
doh, i didn't
sign up for a course in heat transfer. just tell
me the right proportion of coolant and water to
put in my system.
okay, here's just the facts: run the "least" amount
of coolant you can in your system that will provide
freeze and boil over protection "for your climate",
throw in a bottle of Redline water wetter too,
and fill the system the rest of the way with "pure
distilled" water. here's a table that's pretty
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