Thread: sr20ve itbs 50mm bmw

it is a merged collecter, 4-1
4x 1 3/4 into 3" then down to 2.5" for the muffler it has a 90 degree bend due to the quick exit into muffler and out. will try get different photo

It looks more like a formed collector that slips over the pipes. The header should choke down to 2.25 as it exits the header.

something like this but you have bends. It could still be done.

x 2 on a proper/longer merged collector with a smaller choke.

I do like the ITB's though. Is there a chance you will have an overlayed dyno graph with a before/after the ITB install? You still have N1's to install, correct? Are you able to dyno the N1's seperate to the ITB's? I would love to see the difference the BMW throttles make, with the same setup.

hi yes, the n1's are not going in, but the new exhaust will be on as well. so wont be able to get power gain from throttle body alone. as the old headers i had were from a de motor. so very restrictve for the ve. so only changeds are the intake and exhaust.

remember this is a race engine, which lives mainly between 5000-8500rpm range.

also the runner length is just on 24" equal apart from number four it about 22"

but it was my first headers, might try make something different later on.

ok we actually lose power, 20hp between 2000-5000 rpm and 10hp 5000-8000
two main reason, the injectors are not at the correct angle, actually hitting the intake roof,
and i need to make a longer pipe from collector to muffler.

Sounds like it might have been better to cut up the stock intake mani behind fuel rail. How are you going to fix it?

I think there a two problems:
1.The angle of the ITB's
2. The collector and choke of the header
Just my .02

looking at the adapter and the itb's i think BlueRB240 is on the right line, as the injectors when on the original engine point directly into the head as you can see here

injector direction


placement on head


where as the adaptor plate you have doesn't help with this


also the inlet trumpet length may not be ideal, here are the stock bmw ones



have you thought about where your going to try and modify this to correct the problems? imo i'd put the old exhaust back on so you are only chasing problems at one point as changing both like you did makes it harder to work out what made the main differences