No one had boost creep with this manifold and i dont think double turbosmart 40mm arent enough

I will agree with fendamonky and point to the bad manifold design. I dont know what manifold you have but i will take a wild guess aand assume it is the turdblown ?

i have yet to see a manifold that didn’t creep from the said vendor

make a custom exhaust gasket with only a 3” hole and see what that does. If you have boost control you can play around making it larger until it starts to creep again, or vice versa if it still creeps.

It all comes down to balancing pressure differential between the turbine path and the WG path. Differential pressure relates to flow path area. The force at the larger turbine flow path area will increase more than the smaller WG flow path area when backpressuring the entire system.
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Any pictures of the manifold and WG priority?

the issue is that on the surface, the two smaller 40mm WG flow ratings appear to mimic a larger single 60mm wrt total flow rating, but what is being missed is that the flow area of the 60mm WG is significantly greater that the flow area of a 40mm WG. That there are two 40mm WGs is moot. In a low emap situation, the larger flow area of a 60mm WG has a significant pressure-induced flow advantage over the smaller 40mm WG flow area.

It’s the very same reason that putting a smaller hole gasket in the rear of the exhaust appears to back-pressure the entire system equally, yet it influences flow away from the larger turbine discharge opening to the small WG opening.
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what part of the rear of the exhaust you mean to put the gasket got no gaskets they are all v-band.

it would need an orifice plate insert or something similar to create a restriction then, same thing in principle
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I never did understand why they went and mimicked the final taper into the T4 twin scroll oval port opening to the same ID as the 1.5” Sch. 10 pipe (1.682”) on their cast manifold design. The T4 twin-scroll oval port opening is equivalent to a 1.875” ID. Which is almost equal to the 1.5” pipe OD of 1.900”. Because they used to squeeze the 1.5” pipe into the T4 oval port opening when hand fabricating them. While it was easy to hand fabricate that way, it wasn’t optimum for flow dynamics.

Because they over-compress the flow maybe thinking it has a velocity advantage into the turbine opening, but what happens is that the flow suddenly hits an expansion point of the larger oval port opening; losing the velocity advantage, and then has to recompress again into the turbine scroll.

In my minds eye this is resulting in an overall energy loss compared to tapering smoothly from the 2” ID exhaust port opening down to the equivalent 1.875” ID of the T4 oval port opening, and then the final compression/velocity increase into the turbine scroll. Which could easily be accomplished with a cast or 3D printed manifold.

:dunno:
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if it's vband it aint Turblown lol

please post a picture of your manifold.

I read that as him meaning that his exhaust (post turbo) was vband, as opposed to the manifold.

yes, he thought you were referring to the turbo manifold, not the downstream exhaust system as you had intended.

it would be beneficial for us to see how the manifold is configured and also how the WG pipes are plumbed back into the exhaust system if you have any pictures that can be posted.
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ah, the old Japanese proverb strikes again

猿も木から落ちる
(even a monkey can fall from a tree) :suspect:

waiting to see your pending G35-900 results. 🤣
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I dont think i would like to restrict my downpipe I think the problem are my wastegate flange position

that would consist with a poor manifold design. share some pics of the setup.

try thinking it through some more

it could be temporary pending modifications or easy in/out if you intend to boost it up with better fuel/higher power, but it’s not like you’re racing or making big power at the boost level/turbo being discussed. You never saw a muffler/resonator at the end of an exhaust system with an insert at the tip and a small bolt to hold it in place? Generally done more for streetable sound level, but it’s essentially the same thing.

If there was a 3” exhaust system on instead, you might not have any issue at all and be none the wiser, that’s just a guesstimate though. Nobody is suggesting to choke it off. It’s a bit more subtle than you might be comprehending.

nobody can really help you without seeing/understanding what you have though and it seems like you’re intentionally sidestepping all the requests for pictures.

Is there something you don’t want us to see? :dunno:
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when the car is done I always post them on my social media.

I must have missed it.

what MANIFOLD are you USING? Photos?

https://cimg7.ibsrv.net/gimg/www.rx7...abe02e9f0.jpeg

I dont see a reason to hide the branding, i think thats the SAS manifold out of the uk?
i have not seen them in person or used them

Because i dont like to criticise someones work thats all just the design didnt work out for me but he is eager to help me out so dont want to talk bullshit about the guy.

Well in this day and age, opinions are like ass holes and everybody has one. So I would not worry too much.I saw some work from SAS, the stuff look nice but i have not had the chance to test them.

Are the wastegates routed back in the exhaust? Hows the dump tube situation?
hard to say from the pic but i dont think you will boost creep with this manifold

No they are vented to atmosphere
https://cimg8.ibsrv.net/gimg/www.rx7...a9f625252.jpeg

そうだね、待っていますよ！

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so yeah, the WGs are vented to atmosphere, but not biased at all. Rather perpendicular to the flow stream. You don’t want to criticize then ok, I will. That style with only 40mm WG is exactly what I stated previously. The small flow area of 40mm with such poor bias and resulting small dP area force favors the turbine and not the WG flow path. Even just a 45° elbow there rather than 90° to the flow path would be so much better. It’s not a good design.

Not like it’s a secret even, wth …


https://cimg1.ibsrv.net/gimg/www.rx7...9cd58dc42.jpeg
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so when you go look at Howards nanifold design and the WG flow path being biased against the flow even, what maybe isn’t recognized is that the large 60mm WG has ~2.25x more area than a 40mm WG. Or rather 225% more force relative to pressure to flow in that direction.
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yes I know they are a bad design but now im thinking if I should fix this runners making the WG have priority or should I go with larger diameter runners as this are 1.5”.