Downpipe and 02 sensor housing

[GreddySpyder]

I already have a Greddy EVO exhaust, Greddy intercooler piping, Greddy BOV, and a K&N air filter on my 97 GS-T spyder that i recently bought. To you experienced tuners out there, I have a few questions:

1. about how much flywheel horsepower do you think i have right now,

2. and how much would i gain with an aftermarket 3" downpipe and O2 sensor housing?

3. Also, in regards to the BOV, I haven't adjusted the screw on it that is labeled soft to hard. If this setting was too far to the soft side, could that have anything to do with the fact that my boost gauge never goes all the way to the top line where the + sign is, or is that just to do with the fact that the stock gauge sucks?

4. If i install a manual boost controller (after getting an aftermarket boost gauge of course), how much boost can i safely run on 93 octane?

5. Last, when I upgrade to a larger turbo, i know that i will need to upgrade the fuel system to raise the boost very much, but will a larger turbo make more power at the same boost pressure as a smaller turbo?

Thanks for looking

 

[Ludachris]

1. Way too difficult to tell. With turbo cars, this question is very hard to answer without knowing many, many details about the car. Your best bet is to have the car dynoed.

2. Again, have the car dynoed. Guessing how much hp one part will add makes little sense with turbo cars. It's easier to do with N/A cars.

3. Couldn't tell you.

4. I believe 15-16psi would be all your injectors/fuel pump could handle. I'd stay in the 14-15psi range.

5. Yes.

 

[98 TSi AWD]

on the crappy t25 I ran 17psi on pump gas,, no bad egt's and a/f was good,, but I never logged it. anything over 15 psi on the t25 just heats up so much its not really worh it, (ran better times on 15psi)

yes you will make loads more HP w/ a larger turbo because the temp will be cooler so you will be flowing more air at the same boost.

 

[GreddySpyder]

thanks for the feedback, by the way, what is the stock psi? about how much does an aftermarket exhaust like i have and a BOV raise the pressure?

 

[GreddySpyder]

oh yeah, also, i've seen so many possible turbo sizes and combos that i don't even know where to start making a decision on a turbo upgrade. I want the usual i guess you could say, a turbo that makes a lot of streetable power. I'll take my car to the drag strip every once in a while, but most of all i want a street beast, I want to be able to get into the mid to low 13s in the 1/4 mile, possibly 12s, I know this will take some building, but i just want an idea of what turbo can get me to this goal with some other upgrades and still be streetable. What would be an advisable turbo size for this use?

 

[Turbo Guru]

Originally posted by Ludachris
1. Way too difficult to tell. With turbo cars, this question is very hard to answer without knowing many, many details about the car. Your best bet is to have the car dynoed.

2. Again, have the car dynoed. Guessing how much hp one part will add makes little sense with turbo cars. It's easier to do with N/A cars.

3. Couldn't tell you.

4. I believe 15-16psi would be all your injectors/fuel pump could handle. I'd stay in the 14-15psi range.

5. Yes.

I couldn't have said it better myself!

 

[doug]

GreddySpyder, your VERY NEXT mod needs to be an aftermarket boost gauge!!! The stock boost gauge is just a toy. With the Greddy BOV you already have, you have no idea how much boost you're running now. If you upgrade anything else in the intake path (boost controller, turbo, etc.) before you get a real gauge, you're asking for lots of trouble.

 

[LandoAWD]

GreddySpyder, your VERY NEXT mod needs to be an aftermarket boost gauge!!!

 

[Powerboarder]

Originally posted by GreddySpyder
thanks for the feedback, by the way, what is the stock psi? about how much does an aftermarket exhaust like i have and a BOV raise the pressure?

I believe the stock psi is between 11 & 12. You should look up the thresh-hold or psi rating on your BOV, probably 18-20 psi, I'm not sure, but the BOV will not add pressure it just holds that amount (relative to creep). The stock 2G BOV holds around 13 psi at most, the 1G BOV will hold 15 psi or more if crushed.
Exhaust helps the turbo spool and "breath" and might add there. You will get more hp out of it, but not as to psi.