Just curious if anyone has actual proof or a proven theory as to how much gain or loss of hp/tq (if any) there is in dumping your wastegate to atmosphere, or routing it back into your dp.

At the moment I have my wastegate dumping to atmosphere and made great dyno numbers, but I want to start smoothing the car out from all angles.

I searched (although quick) and didn't come up with anything credible.

 

I've always heard if you plumb it back into your exhaust correctly then it is a very minimal hp loss. If done wrong then it can rob some serious hp.

 

it makes a decent difference check out my thread.

https://www.rx7club.com/single-turbo-rx-7s-23/re-routed-wg-vs-atmo-wg-some-final-proof-657974/

 

It's also application dependant.
Wastegate size, downpipe/exhaust diameter and turbine A/R's just to name a few would effect the difference. Back pressure plays a major roll. Even the way it's routed back into the system have an effect.
Personaly for a street driven vechicle I would sacrifice the little power lost vs the noise. Too each their own I guess.

 

Even though my car is street driven... my dumped wastegate sounds just way to amazing to dump it back into the DP. So im kind of stuck on this also.

 

Ah I see, Thanks for the added info. I'm just dumping mine for now to see how it sounds, probably will keep it that way as everytime I hear sound clips with it dumped it sounds great!

 

If you are dumping to atmo, does it matter where you aim the pipe?

 

I got the Apexi kit which dumps to the atmosphere. Initially intended on plumbing back into the MP but the bend was going to have to be too sharp. Then I went and got addicted to the noise. I giggle like a little girl every time a punk wants to street race, sun visor turned sideways hanging out of his window. A quick wastegate blast usually takes the fight right out of them....

Similarly to Unseen's question. Do any of you guys track your car? I've noticed that during a track session my transmission seems to be overheating, judging from the fact it will start to grind gears a little, when normally it's fine. And I'm VERY easy on my transmission when it comes to shifting. My theory is that all the heat from the open wastegate right beside the transmission is causing it to get a lot hotter than it normally would. I wouldn't expect that due to the high speeds, but aerodynamics are a tricky thing and there could well be a negative pressure bubble in there somewhere causing the heat to build up. I know the area around the transmission on the inside of the car can get too hot to touch during the summer. Just curious if you guys have noticed anything like that.

Excellent post, smg944. I would have never expected it to be a 20hp/tq gain.

 

I am working on a different setup all together. I don't want the added attention, or noise, from dumping mine into the atmosphere so I am working on a separate muffler system just for the wastegate. Like a stock GSXR muffler or some thing similar. I'm hoping this will keep the HP numbers up but quiet it down as well. My TII was scary loud! So what do you guys think??? Mike

 

Thank you for all the input. I do agree with crispeed when he says results are always dependent on specific variables, therefore I'm only going to take smg944's dyno graph into consideration and not as a proven theory. Thank you again though for your dyno graph's and input. Anyone else have something valuable to add?

 

yes crispeed is right. if you have a bigger dp/ bigger a/r turbine etc. the loss will be less. on my setup everything was the same size except for the wg plumming.

 

I think it really does boil down to the noise more than the horsepower. Some of us like the sound and can get away with it, some don't/can't. I did hear a guy at VIR a while back that had a separate muffler for his downpipe. Had a very distinct sound. Unfortunately I don't know who it was or if they're on here. Seems like it might be the best of both worlds though. Though you probably have to be careful about heat since from what I understand rotary exhaust temps are a lot higher than piston engines.

At one autocross they had a decibel meter and mine chimed in at 115db (don't think I was WOT when I went by them either)... Definitely loud, but the kid in me can't help but cheese every time I do that under and overpass......

 

I run open wastegate also. There is just something about running 17psi wide open that I love. The spring in mine doesn't open until 12 psi. So, during normal driving, it's not a big attention getting car (3 mufflers). At the drag strip, it gets awefully noisy though!

Josh

 

This is exactly what I`m going to try, let me know how it goes as I`m not there just yet

 

I'll keep you posted on the progress.

 

Some earlier Porsche cars had a seperate cat and muffler for the wastegate from factory.

 

This is the one I'm going to use. Might be a tad long - but its going to sound mean when the wastegate starts modulating at WOT...

I should be able to tuck it up along the driveshaft.

http://store.summitracing.com/partde...DH3011&FROM=MG

EDIT: and yeah - its got glass guts, but I figure for 28 bucks (using the mighty Canadian dollar ) I'll run it till it blows out and then see what it sounds like hehe. Plus its not under as constant a pressure/temp as a standard placed muffler so I estimate the glass should stand up proportionally longer.

 

correct me if im wrong but couldnt you just run a bigger exhaust and not worry about the recirculated wastegate killing performance?

 

like stated above, there are many considerations, and this is just one of them...angle of re-entry of exhaust gases (IE: perpendicular to flow, vs 15~20 degrees of parralell) size of wastegate, exhaust wheel size, distance from turbine flange, EX. housing A/R also figures in.

way to many variable to just make a blanket statement. I have a 50mm wastegate, and mine is plumbed back into the down pipe approximately 19 inches from the turbo flange, my angle of re-entry is fortunate in that it is about 15 degrees and come into the downpipe at a very slight angle, this all helps immensely.

18" or greater form flange = exhaust gasses are already dropping in tempature and velocity, wastegate's low angle of re-entry does not cause as much turbulance.
you have a border area within a couple of mm's of the pipe wall where the exaust gasses eddy and tumble. the farther away from the wall you go, the smoother the flow becomes, anything that interferes with this smooth flow is bad for HP but once the flow starts to slow down due to cooling etc. it has less of an effect on the engines horsepower.

while I have not dynoed it with and w/out I am confident that my system loses very little HP in relation to a straight dump

Kenn