When I purchased my car it had already BHG
(Blown Head Gasket) It was not severe case, not noticeable at all when driving at stock boost
pressure. The only sign of BHG was slightly higher coolant level in overflow
reservoir and accordingly lower level in radiator because exhaust gas was
leaking past head gasket pushing water out of cooling system into the overflow
reservoir. After I learned what is
shimmed wastegate mod I increased boost pressure to 0.7-0.8bar and situation was
getting worse. 7MGTE was plagued by BHG since Toyota released this motor in
1986. To cure this problem for people who wish to stay on stock boost it was
sufficient to retorque stock head bolts to 75-80 ft-lb. It works provided stock
gasket was not trashed already. The best was of course to use MHG (Metal Head
Gasket) in combination with ARP head bolts or studs (studs are preferable, but
if studs used due to tight firewall clearance it is very difficult or impossible to remove
and
install cylinder head if engine is still in the car). This
mod opens ways to future power upgrades.
In 2001 I did my first engine rebuild. The shop where it was done was not
performance oriented and they did not know about MHG and block and head surface
preparation requirements when using it. I decided to use stock gasket with ARP
bolts torqued to 80ft-lb, it was proven to hold 1.0-1.2bar of boost. I had to go
+0.5mm stock pistons because some bores were scored. I changed also all
bearings, oil pump and water pump. Head was skimmed 0.22mm and block 0.04mm. To
retain close to stock CR machinist removed the same amount from the top of the
piston crown.
After this rebuild my car was well equipped to run higher boost level, I had
Lexus AFM / 550cc injectors (well known Lexus/Riemer upgrade), APEXi AVCR and SAFC, stage 3 turbo from Suprasport
and Spearco intercooler with 2" hardpipes. I was trying
to limit myself by 1.0-1.1bar boost pressure and felt very bad about it, every
normal person who got bitten by boost bug wants some more of it. By that time I
knew there were quite few shops and machinists here who can handle MHG job. I
decided to do another rebuild.
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When
my ship was in Yokohama I bought HKS 2.0mm Stopper MHG. At the same time I
ordered from Suprasport set of JE pistons and rings, +0.020" oversized and Fidanza
lightweight flywheel. I also ordered RPS 3200lb 6-puck disc clutch but by
error I was sent Sport series clutch which I sold to another local Supra
owner. The same spring 2003 I ordered aluminium driveshaft from Titan
Motorsports, again by error they sent me 300ZX shaft. I had to ship it back to
TMS, then added another $100 and they sent me carbon fiber driveshaft. It was
good deal :)
In June 2003 motor was rebuilt with all these goodies. At the same time I
machined off A/C belt groove from the stock crank damper. Later I learned that
it was not so good idea, but back then I wanted something lighter fitted on my crank and this was
something in between stock damper reliability and going stupid with solid undampened aluminium pulley a-la Unorthodox Racing. My intake manifold was port
matched to the head, CR after rebuild was 8.0:1.
In attempt to clean up engine bay and make the car lighter I removed and
scrapped a lot of useless (and not so useless) stuff like A/C, cruise control, EGR, various vacuum lines and VSV, etc.
I regret I did not use ARP rod bolts, I would feel now safer when revving it to
6900rpm. So far 6980rpm is maximum what I saw on my datalog, I set rev limiter
on 6700rpm. In plans is motor rebuild with Pauter connecting
rods, crank scraper, ARP main studs and flywheel bolts. It opens the way to run
safely higher rpm limiter, in the range 7500-8000rpm. I have no intention to rev
it really high, high rpm kill engines pretty quick.
In summer 2005 I ordered lightweight crank damper from ATI. It took long 7 months to get it at my door. ATI dampers are among the best in the performance engines world. I ordered it without A/C pulley, in fact now I use only one belt
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to drive alternator, my mechanical water pump, A/C and power steering are gone. Damper can be ordered with removable A/C pulley, timing marks are an option. It is good substitute for my bastardized OEM pulley and weighs less. Damper rated at 600 continuous hp or 800hp for drag racing use. For higher horsepower goals damper diameter has to be increased. My damper had small interference issue with timing belt cover, can be fixed in few minutes with die grinder.
Stock 7MGTE oil system which you can view on the pdf. file on the left is horrible even for stock power levels. Some people report temperatures as high as 100C when cruising at cold weather. Imagine how high it can be at hot weather. Stock system incorporates 2 relieve valves - one on the pump, another integrated into the stock oil filter bracket. I never saw proven data at what pressure these relieve valves open and my guess is pressure setting of oil filter bracket relieve valve is lower than the setting of oil pump relieve valve. If you look closely at the 7MGTE oil system you will realise that oil is passing through the stock oil cooler only when pressure exceeds setting pressure of relieve valve on the oil filter bracket, around 40 - 50 psi (not sure about that). It happens only at 4000rpm or higher if oil is hot. Now think what happen when you drive your car hard and then slow it down. There will be no flow through the oil cooler because at low rpm oil pressure is too low to overcome pressure relieve valve on the filter bracket. This system is really stupid. Below you can find few ideas about improving 7M oil system. Info is gathered mainly from Supramania and Supraforums. It concerns only stock oil system, not dry sump or other exotics.
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Let's start from down - from the oil pick-up. Oil strainer located quite high, 30 - 35 mm from the bottom of oil pan, to improve it pick-up pipe can be bent down about 10 - 15mm to reduce chance of oil starvation during acceleration, deceleration or cornering. Pick-up pipe generously sized, no complains about it. You can see how it is done on the picture above on the right, this is stroked 7MGTE of Adjuster from Supramania. Nice motor... Next come oil pump. 7M oil system is high flow low pressure system. There are two ways to increase oil pressure in the system. First is to restrict flow somewhere, of course we are not going to do this. Though some people recommend to spot weld oil holes in the stock connecting rods (anyway aftermarket rods don't have them) or to blind piston oil squirters to give more oil to the bearings. I would not do it because they help to cool down pistons. Second way to increase oil pressure is to increase flow, this is the way we should consider. Would be nice to have higher flowing oil pump, but so far there is no real substitute for stock pump. I am not talking here going external oil pump and dry sump, it is another subject. So called "high flow Toga oil pump" for 7M is actually the same stock pump made by Aisin and sold for $60 more. My suggestion is to open up your stock oil pump and measure as per TSRM body clearance and side (axial) clearance. If these clearances too high oil is going to bypass gears from discharge to suction side causing drop of pump production. Body clearance specified as 0.105 - 0.175mm, if it is too high there is nothing you can do about it. Next is side clearance specified as 0.03 - 0.09mm. Here, if clearance is on the higher side we can lap first pump cover to make it ideally flat and then machine or lap on the face plate pump body to bring clearance down to 0.03 - 0.04mm. It helps to increase pump flow and subsequently oil pressure. Exploded view of oil pump is on the picture above in the middle. Now let's look at the oil pump outlet pipe, it is connected to the oil pump by banjo bolt, this is major restriction. Solution is to replace it with -10AN hose using high flowing fittings. You can see it on the picture above on the left, contributed by flubyux 2 from Supraforums
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Now, when you are done inside the crankcase, you need following
things to further improve oil system:
Oil filter relocation kit
Oil temperature thermostat
Oil cooler
-10AN hose and fittings
Installation is pretty straightforward, use sketch above. I saved it some time
ago from one of the oil system topics on Supramania, don't remember who is the
author. Other 2 pictures above taken from amazing
IJ rebuild thread on
MKIII Tech. This is baffled magnesium
Group A mk3 oil pan, a must for serious g-machines. It's a pity it is too rare.
Another step in the same direction is installation of oil pressure accumulator,
it helps to restore oil pressure in the system if pump loses suction under high
lateral and longitudial g-loads.
I collected all components to upgrade oil system more than 1.5 years ago, last summer I dumped pathetic OEM cooler and modified the system. Now my setup is like on the diagram above. Used Earl's oil filter relocation kit, B&M cooler
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and 180°F (82°C) thermostat, Toyota filter,
part #90915-200004, it is nearly twice bigger in size to compare with stock
filter. I skimped on Earl's fittings and stainless steel braided hose, barbed
fittings and hose clamps will do the same job just fine. Thermostat has no
fitting bracket attached, I had to zip tie it. Now oil system holds close to 6.5
ltr of oil, oil temperature is always steady 85-87°C measured on the engine
inlet. I noticed my oil pressure is up 0.1-0.2 bar at idle, probably with the
past stock configuration it was closer to 100°C. I use Castrol oil, either RS
0w40, or SLX 0w30.
Stock cooling system in decent condition is absolutely adequate for 400-500
or more hp. In fact I purchased my Fluidyne
only because upper tank of my stock radiator cracked and I decided better to
buy performance radiator rather then trying to repair old and tired OEM.
Stock viscous clutch fan moves a lot of air, it's biggest disadvantage is
production drop at idle rpm. After driving car hard coolant temperature spikes
if you get stuck in the traffic. Another factor contributing to such behaviour
is pumping rate drop at idle of stock belt driven water pump, similar in fashion
to clutch fan. Very popular solution to cure it partly is to scrap clutch fan
and install electric fan. I did it quite long time ago, had Permacool 14" fan,
then accidentally broke it and now use 2 junk yard fans of unknown origin. They
cost me $20 (thanks to SOARA) fit very well to stock or Fluidyne
radiator and move a lot of air. It saves you couple of horsepower as well by
removing coupling's parasitic loss. Next step was to do
something about stock water pump. I first time read about Craig Davis EWP
(electric water pump) few years ago and decided that I
definitely need it. For me main advantage was possibility to quickly cool down
engine between runs, with stock system it takes longer time and if cylinder head
temperature goes up performance suffer. I can't guarantee the following is true,
but I remember reading
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some time ago that 10 deg.C increase of coolant
temperature requires increase of RON for about 2 - 4 points. If opposite is true
then running colder coolant temperature means more power. I use 84C thermostat
and my temperatures always steady 84-86C. It hurts fuel mileage though, the best
for fuel economy and emission is when coolant temperature maintained at 94-96C. In summer 2005 I purchased Meziere 20 gph universal
water pump (thanks to Oleg Coupe for help). Bolt-on Meziere EWP for mk4 Supra is
20gph as well, so if it is good for mk4 it should be good for mk3. Later I
learned that this pump's life expectancy 2-3 years, When it dies my next pump
will be more reliable Craig Davis, it is also twice lighter to compare with Meziere.
Employment of EWP requires relocation of turbocharger coolant line to the
suction side of the EWP. You can see the barbed nipple for this line on the
picture above in the middle. Pump itself installed into the lower radiator hose.
Stock pump was removed and aluminium blank plate installed. For those driving
their Supras in the cold climate there is one drawback - stock heater return
line connected to the back side of the stock water pump housing. To have good
coolant flow through the heater you need to reroute this line to the suction
side of EWP. It is not easy task and I did not do it. I don't drive my car in
winter, and besides it still provides enough warm air to feel comfortable when
ambient temperature around zero C.
As a side benefit EWP adds few hp to the wheels. I should mention that EWP is of
advantage in stop and go traffic and for short power blasts, like in drag
racing. It is nowhere close to stock mechanical pump in flow rate and not
suitable for prolonged high speed run, like road racing or driving at 130mph+ on
highway at high ambient temperature.
To further improve cooling I use Sard 1.3 bar radiator cap and 30/70 mix of
antifreeze plus Red Line Water Wetter. High pressure radiator cap increases
coolant boiling temperature, it prevents formation of tiny steam bubbles in hot
spots, and Water Wetter enhances heat transfer ability of coolant
And last but not least - I have vented hood, one huge vent over the radiator and
two smaller vents on the sides. It helps to keep things cool as well.
Some basic reading can be found here:
Cooling system
tutorial from Meziere
7MGTE ignition system is stout enough to support 600-700 whp, you can check out 7MPower and see that many high horsepower guys are on stock ignition. Make sure your ignition wires up to task, simple $60 NGK wires will do the job. My choice of wires is Magnecor KV85 and I use NGK copper BCPR7ES plugs, they are one step colder than stock. I don't believe in iridium sparks hype, they claim to require less arc-over voltage and at the same time more spark power. Spark power is directly proportional to the square of arc-over voltage and I better stick to copper here. Copper plugs dissipate heat better than platinum or iridium and more suitable for highly boosted hot running motors. They wear out quickly, but they are cheap and I don't mind to change them every 5K miles or so. Many people very happy with Autolite 3923 copper plugs, they seem like one step colder (not confirmed) and cost only $1.15 from Walmart. I purchased a set and want to try it this summer. On very powerful cars (800hp and higher) copper plugs last one or two quarter mile runs and I know most of heavily modified mk4 run iridium plugs because of better durability. Stock spark plug gap is 0.8 mm, if you are runing more than 15 psi boost gap has to be reduced to 0.7 mm, even further down to 0.6 mm for 30 or so psi. Possibly your idle will be slightly rough at too low plug gap, but this is tradeoff for the ability to run high boost without miss. Though I have seen reports from some mk3 owners running 30 psi boost on stock gap 0.8 mm with stock ignition. Here I can only advice to try what works best for you - run with stock gap and reduce it gradually if misfire experienced. Another negative effect of too low gap is possible decrease of gas mileage. In off-boost situation you want gap to be on the higher side, around 0.8 mm for better throttle response and gas mileage. Unfortunately there are no variable gap spark plugs on the market and we have to find compromise between power and high gas mileage. Modern CDI (Capacitive Discharge Ignition) boxes offer some advantages in both areas. They fire multiple sparks at lower rpm range (up to 3500 rpm, at higher rpm it simply has no time for multispark) and produce far more powerful spark when engine runs at full load. I purchased AEM 4-channel C2DI (2 stands for twin capacitor) 2 years ago to cure my misfire problem at high boost with water injection. After installing it I was not able to fire up the motor. When I contacted AEM tech support they told me that stock Toyota ECU is looking for verification of coil firing signal IGT which is not present when CDI employed. It's not an issue with aftermarket EMS, but if you want to run any ignition box I suggest to contact manufacturer first on the subject of compatibility with your particular motor. Later, when I installed AEM EMS I found that AEM CDI works, but old and tired stock coils create huge arcing between coil bodies and valve covers. CDI produce more than 500v primary voltage, 40 times higher than OEM. Now I want to buy new OEM coilpacks and see how it works. AEM CDI was known to fail on many users' cars, even after few hours of work. Though some guys run them without problems and I hope my CDI won't fail, but to be on the safe side I don't want to go too far from stock configuration. Not yet...
Last summer I tried AEM CDI with brand new
OEM coils, it worked well, no arcing at all. One month later I found strange
miss at around 2000-3000rpm range, sometimes it was present at idle speed. After
bypassing CDI things went back to normal. I switched few times from CDI to stock
and back to CDI, this miss was definitely related to CDI. I removed it
completely from my car, it was known to fail without warning on some cars and I
feel very unsafe when think what happens if my motor suddenly dies on the road.
I tried also Autolite 3923 copper plugs. They seem like stock heat range because
they don't foul even at bumper to bumper traffic. One thing I don't like about
them - they are sold pregapped to more than 1mm. To gap them to 0.7-0.75mm requires
a lot of bending of side electrode. When gapped to 0.7mm electrode looks like "?"
, too much bending can cause it to break and can cost me broken valves or turbo.
From this point of view NGK plugs are better, they are pregapped to 0.8mm and
sold in different heat ranges. Autolite 3923 upper ceramic part is about 3mm
shorter than stock size and it can prevent wires from proper
engagement. Best solution here is to get rid of spark plug cover.
Some useful links
http://www.driftmotion.com/driftmotionignition.bmp -
wiring diagram of 1JZ coils on 7MGTE conversion, discussed
also here