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Discussion Starter · #1 ·
Hello all, after searching the forum for a couple of hours for answers, I thought I'd just come out and ask for a little advice from those "in the know".

In my 2JZ swapped 71 Datsun 240z, I was running a stock 2JZGTE longblock with HKS 272's, stock intake manifold, 7x lb injectors, GReddy T88H header and a GT42 Garrett hybrid turbo (GT42 compressor wheel in a T04 compressor housing with a P-trim turbine wheel with an .81 a/r), 3" exhaust and TH400 with 4200 stall. Footbraking, I was able to build all the boost I wanted at the line for launch (10+ psi).
OK, here is my dilema. After installing my built motor, I am unable to build more than 3400 rpm's and 2-3 psi of boost before the rpm's plateau. I added timing and leaned the mixture further which helped some, but not enough. I cannot find any vacuum leaks, so I am convinced that it is due to the extensive port work in the head (primarily on the intake side), the oversize valves, 282 cams, etc, which have slowed the air speed through the head. On a positive note, I am making the same trap speeds (141-142) with the new motor at 3psi less boost than I was with the 272'd stocker and the boost doesn't come on until I am about 100' off the line, so a good launch would probably raise that as well. :)

Anyway, I am about to go to a 76GTS (further slowing my spool I would imagine), and was hoping for some suggestions on stall RPM. I was leaning toward something in the 4800 rpm range. I am trying to be able to run the car without spray and do not want to install a transbrake as the 87 Z31 LSD and CV's would not stand a chance without the preload of the footbrake!!
As for the car's use, I drive it around town when the weather is nice, back and forth to the track (~30 minutes), with an occasonal 200-300 mile trip.

I think I covered the most important specs and would appreciate any suggestions you all may have before Isend out my converter for a restall. :rolleyes:
Thanks in advance,
Mike Gadwaw
Orlando, Fl
 

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Boost Junkie
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I'm with Jason. Spray it until it hits 20psi or so and then use a hobbs switch to shut it off. You'll be able to run a much tighter stall by doing so.


Steve K.
 

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If you raise the stall too much, your trap speeds will suffer. What is your true stall now, not foot brake stall? If it is pretty high already.....a 75 shot would be a better choice for you.
 

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King of the NA-T's
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Get the converter to stall around 3000 rpm on motor only, then hit it with spray as everyone else is saying. We just changed to a tighter converter on Sat and we picked up 5 mph trap speed without any other changes.
 

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Discussion Starter · #6 ·
Thank you all for the input. I don't want to have my traps suffer.
It sounds like spraying may be my best choice.
I have not previously used nitrous, so I have a few questons.
What would be the best choice for a kit? NOS, ZEX, etc?
Would you recommend a wet or dry shot?
Where should it be plummed ... into the manifold or before the throttlebody?
Regards, Mike
 

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Get NX, one of the best brands and quality products out there today! Also, recommed a wet shot of course. Put the nozzle about 8-12" in front of the throttle body.

now

GIT-R-DUN! :)
 

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I talked to Carl at Rossler Transmissions for a while this morning regarding this. We talked about the easy stage, nitrous and such. He feels that nitrous is the best option if rules allow it. I say go for it :)


Justin
 

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You usually have a microswitch on the throttle stop so it only turns on at 100%TPS.

You can also have it wired though an aftermarket ecu so you can say that it turns on <99%TPS, <20psi boost, <4000rpm etc.

What I want to know is when using nitrous only up to a certain point, 20psi being the example given, how is the tune of the car? I think that tuning this with a wet shot would be easier because it is just jetting. On a dry n2o shot, you have to have the ecu adjust the fuel and timing map when it comes on so if you had say an extra 20% fuel when n2o was activated and then it switches off at 21psi and 20% fuel is also taken out, I would imagine that it would be difficult to keep a flat AFR.

Also, with a wet setup AFAIK you have a limitation as to when you can use it (low revs) because of the mix pooling in the intake manifold. This is why a tuner here recommended a dry shot for me but not to have it switch on and off, just leave it on the whole time when you are racing.
 

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chris davey said:
What I want to know is when using nitrous only up to a certain point, 20psi being the example given, how is the tune of the car?
In most cases, the turbo is spooled within 30-40', so the NOS is on for like one second! You just tune the car without the NOS.

Al
 
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