I have an inlinePRO turbo kit with a GT30R turbo. The dump tube that comes with this kit is designed such that the gases are vented externally. This is a fairly noisy setup and my goal is to make my S2000 as quiet as possible. So, I decided to have a local fabrication shop modify my dump tube so that it is connected to my down pipe. Here are some pics:






My S2000 is so much quieter now and I am very happy with the results. I haven't noticed any difference in performance. I am going back to the dyno on January 20th to have a re-tune done (to resolve some outstanding tuning issues). Do you think this setup will cause a loss in power?

 

I dont remember the exact details, but I remember it being discussed that connecting your dump tube back to your down pipe can cause erratic boost behavior... The waste gate doesn't control boost as well because instead of venting out to the atmosphere, now its venting to another location where there is pressure. The pressure on the dump tube end of the wastegate then prevents it from releasing pressure as easily so it tends to allow boost to creep and/or spike (dont remember which one exactly).

I don't know the specifics of how it works so hopefully someone can chime in and correct/update what i said.

 

You might be correct, but the shop that did the custom fabrication, along with the tuner that I use, stated that there shouldn't be any decrease in performance. I posted this thread to simply get more opinions on the matter.

 

You will overboost if it enters at or near a 90* angle. My wastegate has a 6 psi spring in it but always boosted to 8psi. As soon as I made it a atmosphere dump the boost dropped to 6psi. Not a big deal. But you will have a decrease in performance depending on your exhaust and HP levels.

 

Thanks for the info. Like i mentioned in my initial post, I am heading back to the dyno on January 20th. If there is any decrease in performance, I won't be able to attribute it soley to this mod because I now have a T1R 70R Sparrow exhaust and when I firsted dyno'd I had a T1R 70RT.

 

Ah ok, makes sense. Thanks.

 

nice setup. I would do the same thing if I go turbo since I want to keep the car sounding stock and looking stock from the outside. I think the more downstream the wastegate gases come back into the exhaust the better. And as mentioned before, coming in at a 90 angle isn't going to flow as well as possible. In the end the proof is in the pudding and you won't really know until you dyno and how your boost behaves in general. Good to see someone do this to add info about a non vented WG.

 

Boost creep occurs when the wastegate can't vent enough exhaust flow to hold boost pressure down. It is actually an increase in power, but IMO a performance problem.

Total exhaust flow = Turbine flow + WG flow
So if you increase WG flow, you decrease turbine flow (and thus boost). WG is controlling boost pressure by subtracting from the normal exhaust flow to the turbine.

So the issue with BC is too little flow through the wastegate. The parameters associated with flow through the wastegate (or any valve or orifice) are pressure differential across valve, flow area (sq in) of the valve, and fluid properties (viscosity, etc.).

Redirecting WG outlet back into exhaust (which has more backpressure than atmospheric dump) means less differential pressure across valve, so less flow. Since you can't really control the fluid properties of the exhaust, the only remaining variable is flow area.

In this situation, just get a larger WG to prevent boost creep.

 

You are ****edd, prepare for erratic boost and possible compressor surge, why o why in the hell did they do it so close to the hot side and on a 90.

Not only is that going to blow down your downpipe, it is going to blow right back into your exhaust housing on your turbo

 

I agree that a farther back placement and a Y fitting instead of a T would be better. Both would mean less backpressure for WG to dump into. Do you already have low backpressure exhaust?