How to make your JZX90 faster than a stock turbo supra.

[BlakeNZ]

my definition of "faster" is a quicker time over the quarter mile.
Right, how do we make a 2.5 litre sedan faster than a 3 litre sports car?
Well , the JZX90 has some raw ingredients that lend itself to be a real contender down the strip.
Firstly, the average jzx90 is listed at 1450kg, which is 60kg lighter than the average jza80 twin turbo. This small weight saving actually translates to approx 0.15 sec over the quarter mile.
Secondly, and this is a real key at the strip... wheelbase. Have you ever noticed how supras with road tires wheelspin and axle tramp at the drags? Whereas the Soarers and aristos just squat down on their luxury factory suspension and say 'see you later'.
Some of it is in the suspension, some of it is weight transfer. The Supra wheelbase is 2.55m. The Soarer (also a coupe) is a surprising 14cm longer in wheelbase (2.69m). The JZX90 is even longer again, at 2.73 metres.
Now, if you want to spank cars down the strip, if you have an auto, you are in luck. The auto trans and stall convertor absorb a lot of the shock loading of launch, so no axle tramping. If you want to reduce your quarter mile time, get a shift kitted valve body installed in the trans. This will eliminate the luxury,slow, slurred gear change, and is worth 0.3 secs down the strip.
Each time a manual gear box car has a gear change, boost drops off momentarily. But in an auto, once you have full boost , it stays at full boost for the rest of the run. Also, a manual car has 3 gear changes to make(possibly 4 if you are racing a six speed supra) whereas the auto car only uses 1st, 2nd, and third gears, so only two gear changes, both of which are near instant if you have the upgraded valve body.
From my experience, the JZGTE motors can yield about 30rwkW with a most excellent exhaust upgrade. My testing has shown that the Brian Crower 264 camshafts can yield 26rwkW, with another 4-5rwkW available by tuning adjustable cam wheels.
The stock fuel system runs out of injector at around 245-250rwkW, so a cheap upgrade is the straight fit 2jzgte injectors(Jap spec 430cc ones) which, in theory will give you an extra 13% head room. So the combination of big exhaust and camshafts yield an extra 1000rpm of usable power (you know how people used to say the stock turbo JZ cars feel breathless after 6000rpm?)
The ceramic CT12A turbos love to breathe, and a good feed of air into the factory airbox , with a upgraded panel filter can yield some decent results. Not much gain on the dyno, but out on the street or at the strip, the air being forced into the motor by a well designed cold air feed can yield up to 25 horsepower on a JZ motor (as measured by a G-tech meter).
Now you added all this power, you go to the strip, and the car runs fast on the first run, but then gets slower and slower, losing mph each run. What's up? The big power robber, and enemy of JZGTE motors, is HEATSOAK. The big, thick walled inlet plenum is a massive heat sink, and the air intake sensor is buried deep in the middle of it, so the ECU is taking timing out all the way down the strip, despite the masses of cold air being forced in at 100km/h onwards. So how do we manage this? Two options really. After market engine management allows a Air Intake Sensor to be placed in the pipe prior to the throttle body, which will allow the ECU to at least see actual air temps. Or the cheaper option, which i employed prior to my record run, I paid special attention to minimising intake temps. Firstly, i kept the bonnet up to help heat get away. when in the staging lanes, i kept my idling to a minimum. I had two bags of ice, one resting on the inlet plenum, the other spent time on the underbonnet air pipes and on the intercooler. The ice came off only about one or two mins prior to the run.
Once you have decent power, you will likely need sticky tyres, otherwise you just get frustrating wheelspin.
So at this stage, your car is pretty darn quick, but looks almost entirely stock. Sweet!
As i said earlier, the turbos love to breathe,and at these power levels the pipes to each turbo are restrictive, so if you can afford it, twin intakes are a worthy upgrade. My car has a 3" intake to each turbo, and a bell mouth/trumpet shape attached to the front of each turbo. It also has a 3" down pipe off each turbo. I have stock cams.
As a point of interest, as far as i know, the fastest a jza80 with stock turbos has done a quarter mile in NZ is 12.3 secs.

[Brett7777]

This is an excellent write-up.
I like the prospect of beating fast n furious supras.
It also encourages me to keep the stock twin turbos instead of going steel wheeled.

[BlakeNZ]

Another good idea to apply to our motors is to look at the ignition system. The systems are very good quality from factory, but over time(like 20 years) the coils can develop cracks in them, so you lose spark energy. It's likely that at stock boost levels, you won't even know, but once you crank the boost to 14 psi or more, the engine may develop a "miss".( No, NOT the pretty blonde kind, sadly. I know you were thinking it)
So, removing the coils is best done when the engine is not hot, (10mm socket allows you to remove the three steel frames that each hold two coils) don't lose the bolts.
Remove the blue rubber boot off the end of the coil, and look carefully for hairline cracks in the area that is covered by the boot. If you have cracks, you can buy the red coloured replacement ones from trademe, sometimes called Superspark, sometimes no brand name at all, but are all made in the same chinese factory, and may last quite a while, or one or more may fail quickly. Buying new from Toyota is an option, but can set you back a grand, which is expensive, but you do know they will likely last another 20 years. A cheap fix is to wrap the tip with electrical tape(2-3 layers) then squeeze the rubber boot back on over the top. A longer term fix, is to scratch out the cracks to be a bit wider, so you can squeeze two pack araldite into them. Wait till it hardens, then sand the araldite smoother so the rubber boot fits over nicely, then reinstall. Sometimes a coil can develop an actual fault(rather than a crack), and will need replacing.
I suggest for boost levels 14-20psi, to replace your factory platinum spark plugs (expensive at $20 each) with normal copper/ steel plugs, one range colder. The factory ones are equivalent to NGK heat range 6, so one range colder in steel is NGK BKR 7 ES. In NGK, the "7" is a higher number, which is colder, but in Champion plugs, the numbering system is reversed, so you would need to drop down one number. The factory plugs are gapped at 1.1mm, and I suggest gapping down to around .7- .75mm if you are running higher boost. The platinum plugs can retain heat in their tips and cause detonation when racing.
You can use iridium plugs too (NGK BKR7E IX or the Denso IK22.)

[Brett7777]

This is excellent info. Thanks.

[Brett7777]

this is my JZX90 beating a MkIV Supra, thought it was relevant to the thread he got a a faster time but my launch and reaction time was quicker so i beat him down the strip. this is with catback, cat delete, and pod, other mods coming next month
EuNeM9qtzVE

[Brett7777]

Best time this season was 13.2secs at 110mph.
Hybrid twins, full exhaust, pod, fmic, 2j injectors. Stock ecu. Westlake semis.
Next season I wanna try shift kit and better tyres with R compound to try for 12's.