SONIC TECH NOTE SERIES:
JZA-80 TT Basic Performance Upgrade (BPU) and Road Racing
So my experience has led me in a different upgrade path than most of the notes on the BPU upgrade path talked about on the Internet. Keep in mind we are road racing, some drag during One Lap events that call for it but overall its all road racing. We run out on the road race track until we need fuel or are flagged in. The JZA-80 is a very good road race platform, more in its true design realm than as a drag race car.
See the following two old email threads from 1996
Hi Guys. I don't want to start a mad panic with this text. There is no reason to worry or loose faith with the Mk 4, they are very good cars with fantastic engines, finding the outer limits of this engine will take years.
However, this year our One Lap Supra had the rear turbo fail three months after we ran the car in the One Lap! At our local road race track the #two turbo started making a wicked whooooooing sound when it was called into duty. In two simple words it was POOCHED OUT.
Keep in mind this was after many days of high boost runs, road racing. The car had about 68,000kms to be exact when the turbo popped its guts. There was no visible engine damage and the hot oil pressure was well over 70 psig.
I feel that this failure was in no way the fault of the engine or any bad design on the part of Toyota. From the results of the autopsy on the #two turbo evidently the failure was due to running the car at plenty of high rpm duty at higher than stock boost pressures. It was just a classic case of whipped & clobbered turbocharger syndrome.
When one looks at the size of the turbo's on the 2JZ-GTE engine you would be amazed to see how small they really are! They are both the same size and given the extreme RPM (up to and over 200,000 rpm) they spin under normal operation, let alone when the boost is turned up past the stock boost pressures. It's not hard for me to understand how the odd one would be packing it in. It's really just amazing that they make as much HP at they do.
I have always said that the claims of 22psi and so on with the stock turbo was BUNK, running this much boost will destroy a nice set of turbo's in a short time. I knew Toyota was concerned with the EGT temps around the center area of the head around cylinder #3. This was easy to see by looking at the funky cooling scoop duct on the engine that feeds air from near the hood line to between the #3 & #4 cylinders exhaust ports. Leak down tests confirmed that the center area was running very hot due to the added boost pressure. We were already seeing ring degradation in cylinder 3 and 4 leak downs were 3, 4, 12, 14, 5, 7 %.
My Toyota contacts say that the early pre production test mule cars did not have this funky air grabber on the engine, but when the cars shipped as production cars they had the funky grabber installed. They must have leaned something in mule testing. Another clue is also seen on the European market JZA-80 TT that are sold in countries where the cars would be run on the autobahn, these cars are equipped with the cool air hood scoop as well as even more funky air grabber feeding cylinders #3 & #4. Toyota wanted the extra COOL air for the center of the engine not for COOL looks.
I had kept this info in the back of my mind before I pulled our 2JZ-GTE' poached twin turbo system off to prepare for the installation of the HKS Single Turbo Upgrade. When the turbo's were removed, I noticed that the engine had a small 1" long crack in the aluminum exhaust port flighting on the cylinder head. The crack starts at the lower edge of the header flange on the #three port just below and forward of the funky air grabber air discharge, hmm, very interesting.
This must be one of the first soft spots to show up on the 2JZ-GTE. As the end of this crack is a safe distance away from the meat of the 2JZ's head, I deemed that the crack as not that big a deal and its off to the races as she sits. Our car would now be equipped with the huge HKS Garrett T45S turbo and the SS header. This turbo setup allows for much more air circulation around the cylinder head and engine, as well the header also moves the heat up and away from the cylinder head to other parts of the engine bay. This makes it hotter for other items and cooler for the engine. The ABS and other systems will need to be protected for this extra heat on the exhaust side of the engine bay.
One option that may be a good idea for all you members with tweaked
up JZA-80 TT is an under car or hood mounted fresh air duct system dumping
lots of cool air under the heat shield for the 2JZ twin turbo's for cylinder
#3 & #4.
>>To Reg Riemer
This is the best setup for your car; Don't change the Stock IC but do change the following;
HKS VPC for stock injectors (Run only 1.0 bar with stock injectors HP
450 RWHP @ 80% Duty Cycle)
When you budget allows (best if you do it from the start) would be HKS 720 cc injectors rail and Cosmo pump, VPC prom, HKS GCC
This setup will give you a very fast Supra, safer than cranking on the stock twin's. We ran this configuration on the One Lap car in 1996. Hp at 16psi boost is in the range of +400 at the rear wheels this is the max for the stock injectors if you are on a road race track, 14.7 PSI is better. See dyno pulls on the SONiC FTP site.
Stock turbo's will run 17 to 19 psi but life expectancy of the turbo's is much reduced. Also some reliability problems can develop with the engine do to the extreme heat of the small turbo's running at high pressure and over 200,000 RPM, read attached text bellow. Its really amazing that they last at all if you think about it.
Supra Owners Network In Canada FROM THE HOME OF THE SUPRA GTE Information provided is given free of charge in good faith without prejudice Visit my Supra Page at http://suprasonic.org Calgary Alberta Canada. Office#1-403-259-3106