Exhaust flow restriction (pocketed flang)
 

Hi everybody,
It seems my boost at low revs is not sufficient when i see your figures.
​​​i got 2 or 3 psi only at 3000 and it start to increase by this point to 5 to 7 psi at high revs (wastegate intentionnaly almost at the lowest boost setting).
i saw that exhaust flow restrictions could result low boost at low rpm. My afr seems very nice (saw that it could be the problem). My turbo seems not oversized too.

i have a full 2.5" exhaust except a stupid stock like oem converter in between (2"??) I will try to change that but i realized a mistake that maybe could hurt even more. I received a flange to diy your downpipe but i stupidly tought it was a kind of thermal expension part so i put it between the downpipe and the turbo.

First I saw in a video where someone make this same mistake and say that the fact the downpipe wasn t directly fitted to the turbo could be problematic for the wastegate system. Please tell me how!?

secondly i m embarassed about the fact that the flange is pocketed? I saw somewhere that the pocketed one have to do with optimizing wastegate system (it obstruct his outlet so obvioulsly it s in relation). Does this pocketing (obvious flow restriction) could be good or may i cut it large as possible (or remove it if you tell me to)?

thank you guys for you kindness and your absolute knowledge.

You have a restrictive 2" exhaust (converter is a bottle neck)
Not sure really what else you're talking about, wtf is a thermal expension part?
If your downpipe isn't directly fitted to the turbo, then where the heck is it?
What is "pocketed"?
What turbo do you have? ECU? How can we help you if we literally know nothing about your stuff??
Post pictures
Buy an off the shelf system that works

I'm not sure what a "pocketed flange" is? Do you have a picture?

Yes, a 2" cat on a 2.5" system will definitely hurt spool. Can you get a bolt-in high flow cat there?

What turbo are you using, and what engine?

--Ian

Im guessing he is talking about a bellmouth, where there is room for the wastegate flapper to actually open all the way. If that is the case, that would actually make spool worse, not better, assuming the flapper is blowing open and is the reason for your shitty boost threshold.

Having said that, you have a 2" cat........... thats probably the issue.

Also, pretty sure OP is a foreigner or at least ESL, so go easy

It has nothing to do here it s just a flange they provided me and that my friend told me to be a needed to avoid excecive temperature on downpipe support (not one my 01sti but i tought why not?). I know that is not the case bit it s still there and i want to know if it s needed for me to remove it (exhaust will have to be modified downward). I have rx7 injectors and tdr card and i m far away from the limit of the system at this boost (i only needs to use it at low enrichment settings).

thats a picture of one of these pocketed flange. Note the restriction (surrounding my question!)https://cimg4.ibsrv.net/gimg/www.mia...a56919c83b.png
ge

i sent a picture! Yes i ll try for the cat.
thx

looked for what is a belmouth and i think we are talking from different thing there (i sent a picture). So no reason i ll get the flapper wide open or this could be?

Different things that try to solve the same problem. My previous statement still applies.

ok thx a lot!!

that's not a restriction, your 2" cat is.

they both are.