atmospheric Vs. plumbed back in wastegate..anyone dyno'd the diff?

[turboglenn]

wondering if anyone has dyno'd the difference in HP between an atmospheric wastegate and one that's routed back into the down pipe? the reason i ask, is that i've been running an "open dump" on mine for years and lately for the cause of being able to hear what the motor is doing more, i've thought about routing it back into the DP..

anyone got any SOLID evidence on this? i've heard it's good for up to 3 - 5 extra HP to have it atmospheric, but haven't seen any evidence to support it

 

[bpestilence]

3-5 horsepower? Dynos aren't even that precise. There is no evidence because there is no reason you should make different horsepower one way or the other, assuming that in both cases the boost is the same. The only way there would be a power difference is if the exhaust is so restrictive that the small decrease in exhaust flow when the WG is open would have an effect.

 

[turboglenn]

3-5 horsepower? Dynos aren't even that precise. There is no evidence because there is no reason you should make different horsepower one way or the other, assuming that in both cases the boost is the same. The only way there would be a power difference is if the exhaust is so restrictive that the small decrease in exhaust flow when the WG is open would have an effect.

like i sai, this is only what i've heard, i have nothing to back it up, but am just wondering before i make the swap

 

[daren_p]

I haven't done back to back dyno testing when I had my external dumped vs recirculated but I do have before & after logs & I can say if there was a difference, it was too small to notice. I had it recirculated back into the downpipe & as far as spool goes, same thing if there was a difference, it was too small to notice.

 

[goodbye]

The previous owner of my car and myself used to have this discussion all the time. He said he could definitely feel the difference going back and forth, and his butt dyno was well tuned. I didn't like the open WG after I bought it and routed it back in. I couldn't tell a difference. I think the way you route it along with size of turbo and engine are all going to affect the difference. I routed mine back in 12" down the downpipe at an angle almost parallel to the downpipe. The cheap O2 housings that dump in 2" down at a 90 degree angle would in theory cause more exhaust backpressure and hurt power or spoolup. Of course these are all theories we argued over beers with no basis in scientific fact (dyno sheets), so I can't really be of much help to the original question.