The threads I remember reading were GT3582R (so like EFR 8374 size) turbos around 400rwhp losing 25-30hp, but I didn't find those with a quick search.

I found this one which lost 17rwhp on back to back dyno around 15psi boost (pic of chart no longer showing up, so IDK power).

https://www.rx7club.com/single-turbo...-proof-657974/

I found this one that still has the pic of the chart working that lost 20rwhp from 345rwhp with open vented WG. Also back to back on same dyno and same day.

https://www.rx7club.com/single-turbo...uffler-994766/

 

Well i dont mind the noise my car makes with the dual wastegates. It is not a daily driver. The loss of power and trying to regain that power by adding more boost for me is a no go. I like a reliable rx7 not a high hp unreliable car. I make my car faster by reducing weight,cooler intake temps, tuning and improving the ignition system. I guess i will just need a better tune for that fuel smell. Just dont want to lean the engine trying to do it. I guess there is always race fuel. Oh that cherry smell from that fuel i can do that for sure.

 

I switched to this from a dump:



I don't really care what it cost me for power lol, few things sound as raunchy as a open dump 13B. I also built a small wastegate muffler but couldn't fit it. Ended up using it on my brother's car, it seems to be a nice balance between the two extremes.

 

A muffler vs a dump hmm. I wounder it this would cause a loss of power.

 

Doubt it. With the muffler on, his setup will hold spring pressure within 0.25 psi without any PID or DC corrections.


Not a 13B and you have to turn the volume way up but you can get a bit of an idea. On the dyno, there is no audible change in sound when the gate opens.

Open dump:

Recirc:
https://www.youtube.com/watch?v=6sXtm1gLpic

 

Ah, gotcha.... It threw me off because when I went from an atmospheric dump to re-routing my WG I also moved from a 3" DP to a 4" DP. So I didn't have an "apples to apples" comparison.

 

That is a good point.

The results showing a power loss from re-routing the wastegate into the downpipe would have all been on 3" exhausts.

All turbo exhaust were basically 3" diameter in the US until this decade when the advantages of larger exhaust (especially downpipes) became more common knowledge. 3" exhaust on a turbo car was just one of those "rule of thumbs" that keep us mediocre.

 

2019 is here and I am tired of my setup and almost financially ready for the switch to 8374 iwg turbo. Before I switch I have been researching the boost spike situation with this setup. I see some persons porting the iwg. I have also seen a video of a guy changing the iwg all together with a iwg with two ports. Who has tried any of these things with good or bad results?

 

If you have a cat in there, there shouldn't be a problem mine was prefect at 14 psi all 3in. One i put a mid-pipe on i couldn't control the boost at all. So depends on your exhaust setup.

 

From first hand experience I have found boost control issues with the IWG 8374 are directly related to the design of the manifold, particularly the angle of entry into the turbine housing. Some manifold designs have the exhaust enter in such a way that it hits a wall inside the turbine housing instead of flowing directly to the wastegate and causes difficulty controlling boost. That being said, I have no problem holding as low as 8psi to redline on my 8374 kits regardless of engine porting or exhaust setup.

 

A lot of what people would consider boost creep issues appear to be user setup problems. I recently saw a customer have this issue, and low and behold, switched his ignition and ecu system and problem went away( power also jumped up 17%). Porting the turbine housing definitely works for very high flowing setups, recently had a customer hold 14.5psi( base spring pressure in the turbosmart actuator upgrade) with a full 4" exhaust on his cast 8374 IWG system. A full 4" exhaust will creep on 90% of EWG turbo manifolds FYI, regardless of turbo brand.

I have already tuned long, short, big and small tube IWG kits and confirmed it makes no difference on the boost control. To be clear here I have seen a long runner, equal length manifold creep on the dyno. This one was also fixed by just porting the housing.

There is actually a fair amount of data on IWG housings on other engine platforms, just google 8374 IWG BMW creep.


Its really simple, if you want to run low boost, just port the turbine housing. I recently did one by hand, as the machine shop I used in the past went out of business.