Is this normal???

[volleykinginnc]

Ok I just picked up my 97 GST Spyder from 3SX performance (a DSM only reputable shop here in town). I put on a Walboro 255, 680 inj, FPR, EvoII, GT Headers, SAFC Neo and had them dyno tune it with their wideband. It pulled a pathetic 217 whp at 15psi. They disconnected the exhuast and it jumped up by about 60HP. So we put on a highflow cat and brought my grand total to a whopping 241whp. They thought they could safely boost it another 3-5psi with a new muffler. I have 3" exhaust all the way to the muffler and a @#$ shop welded on a 2.5 muffler.

My question is this....Does this sound extremely low? I can't imagine that putting on a FMIC/3" muffler and boosting another 5psi should make a 80-100WHP difference as that what looks like most people are getting.

Any ideas??

 

[talon20g]

Don't think 80-100whp increase is likely but a fmic would be a very good idea. As far as the 3'' muffler well... I don't know if that would help much with that evo 3 but every little bit counts. But 300whp with another 5 psi and a fmic is obtainable with a good tuner and all supporting mods. Notice the good tuner part. Tuning is the key but just poping some new parts on and uping the boost might get you close but again tuning is the key and saves motors.

 

[romeen]

Your story demonstrates just how important a free flowing exhaust is in a turbocharged car. Switching to a 3" muffler to match the rest of the exhaust will definitely help. It is never a good idea to go from a larger size to a smaller size in the exhaust stream as this creates not only backpressure but also turbulence.

If you are still on the stock SMIC then you may have experienced heat soak during the dyno run. The higher intake temps may have caused excessive knock causing timing to be pulled, thus the unexpectedly low power figures.

Frankly it sounds like the shop gave you very reasonable advice. Given your fuel system you have plenty of room to turn the boost up. They probably could have gone a little higher than 15 psi but then again maybe they had good reason to keep it modest based on data that they were seeing. Since you have already come this far I would take the shop's advice regarding the IC and muffler. Then have them turn up the boost and tune, tune, tune. Like talon20g said, tuning really is key. If done properly then yes, 100 extra whp is possible.

 

[spyderturbo007]

Sounds low to me if you already have a cat back. My dyno results were back when I was pushing about 17psi on the EVO III and with the stock cat-back.

Might be easier if you filled out your vehicle profile. Is that the complete list of mods or have you upgraded the UICP, BOV, etc?

Oh, and just so you know, I'm pushing 21psi now, with pretty much the same mods you have, minus the cat back. So I don't see why you can't be pushing 20psi with your mods. What AFR were you running on the Dyno? Also, all brands of dynos are different, which did they use?

 

[volleykinginnc]

Ok I updated my profile. I am not 100% sure what the brand dyno they were running but it was a AWD set up so I don't know if that had anything to do with it. Is there a rule of thumb as far as PSI vs HP when I crank the boost up? It seems like I will gain at most 25-30 HP with a higher flowing muffler (what kind do you have) which still only puts me at 270. So would raising boost to 20 make a 35-40HP difference?

 

[spyderturbo007]

You could make a generalization about the correlation between HP and boost pressure, but it's really dependant on your car. You can make a much better correlation between flow (lbs/min) and HP. It's about 10HP for every 1lbs/min increase in flow. I am still running the stock catback which includes the stock muffler.

As for upping the boost, you don't want to just go cranking down on the MBC and then making a pull. What are you using to tune your injectors? Do you have a logger?

So by your mod list, I assume you are still running the stock UICP and don't have an AFPR for you 255lph pump? Also, I see in your mod list "k/n".....Does that mean that you have upgraded the intake???

 

[volleykinginnc]

I have a K/N air filter but not the intake piping. I guess that should be my next mod along with the muffler. I do have the AFPR for the 255 pump but no logger as they tuned it on the dyno.

I see in your profile that you are running almost exactly my HP or at least you used to. What uncorked the greatest gains??? What are you running now? That muffler I have on there must be extremely restrictive.