Originally Posted by
Julianvr4
2slow2tedius on 3si...I don't post much here but here is my take on it:
Our rear manifold is a 1n3/4 collected cast manifold, our front is a 1n3/4" half-ass log manifold, feeding a turbine housing as wide as my thumb, using a wheel that was devised in the 80's.
This is why the stock exhaust is ok'ish...we have several restrictions in place, and no matter what you upgrade downstream, it doesn't fix the bunk ass hotside we have (and share with many bolt-on turbos) then if you look at the microscopic internal waste gates we have...another fail. We are supposed to be sending exhaust gas outta that straw hole. Someone needs to cast a bigger hotside.
Adam vr4 running 14b's and adapter plates was able to squeeze out more boost after he got an actual manifold setup.
DSM's and EVO's get a set of hks 272's almost immediately because the are so inexpensive to get their stock cams reground ($200) for us, it's about $400 from Delta camshaft who will copy the lift/duration of the HKS 272's. They also have a much newer front mount, and a BIGGER TURBO. EVOs run 20-21 psi stock on the 16g. They don't have 3 cat converters or limited to a 3" down pipe for 3L of displacement. Packaging constraints are less of an issue for them.
Half-ass proof
My last setup on 9b's and stock cams, I would hit fuel cut before I got any knock at 18-19psi. The car was FAST after I put a fuel pump and a clutch in it. The car weighed 3500lbs with a 1/4 tank of gas. This was on a JDM ecu and I had gone through the combustion chambers with 220g and 320g sand paper to knock down the high spots and smooth out the texture. Nothing to it. Note that I was also running open downpipe the entire time. On 9b's. Stock side mounts. Very healthy engine, perfect compression, NEW OEM IGNITION (coil pack/ptu/plug wires).
This next build that I'm very close to finishing (twin HX35's on a BONE STOCK 6G74) will probably poop out at 15-16psi without meth injection just because of the high compression (making 550whp on 93oct) I've done everything I can to make sure that my biggest restriction is the cylinder heads lol.
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