right for a long story really short when i got my ef crx with b16a it came with this long runner 4-2-1 manifold on it (hand made etc) basicly it clears the oem front crossmember with no grinding required :D

anyway i hit it on the underside and cracked the flange that bolts up to the bracket on the underside of the car, so i had it all off and re-installed an oem stock b16a manifold again. anyway when it got repaired i had the latter section altered to a 2.5inch collector and flex pipe for a few more hp's.

the question is this: when i had the oem manifold on the exhaust (tanabe super medallion racing) was really loud, so was vtec, but when i run this custom manifold it makes it run seriously quiet (at least 20db quieter)

also when coming down off vtec with this custom header i hear a sort of fluttering noise coming from the underside (only when coming off the throttle though). so the questions i have are as following:

do you think the fluttering and quietness are being caused by a not so good join at the place the primarys enter the secondaries? its a tight fit and required a good hammering to get them to slide all the way in?

my mechanic said NOT to use exhaust sealing paste when joining them up because stainless steel prevents it from sealing and it will seal on its own? is this true

could it just be the design of the header that is making it quieter.

anyway some pics before it got modofied (and yes the car still made the fluttering noise and quietness before it was repaired)









if anyone could give me some advise it would be great :D. would exhaust wrap around the collector help seal the outside of the pipes if they are leaking gas? the place that modded it said they could weld it BUT because the pipes are so close together they wont be able to weld all the way around it.

thanks in advance

 

nice header
I wouldn't weld it. if you do then it would be a bitch to take out of the car
maybe cut a 1/2 inch slit on the 4 outside pipes and use a exhaust clamp so when you slip fit everything together you can tighten the exhaust clamps around the pipes. that should seal it up given that you have enough space.

 

the manifold is already back on the car

to get it in/on we just dropped the front cross member and fitted it, last tie we took it out we put one of the primarys into the rad core :lol: (the rad was duff anyway, nice new shiny in there now though)

just wondering really why it seems alot quieter compared to the stock as it easely flows more gas and also does not deaden sound like the cast iorn manifold :?

 

Move your O2 sensor.

But my engine's note changed dramatically when I was testing a friend's custom header vs. my old JDM DC 4-1.

- Derek

 

move the o2 sensor?

car is obd0 which runs a 2 single wire o2 sensor setup. though the car is chipped and tuned with BRE (see pmgfi.org) so the secondary o2 sensor is disabeled and it just reads from o2 sensor 1 and mirrors its value across the ecu to sensor port 2 (so you can use port 2 on the ecu for a wideband)

o2 sensor works either in the collector or in the runners, seems to make no diffrance to the cars out put afr's at all

 

But it's only sampling from one cylinder...

Not a very accurate portrayal of the engine's overall A:F, now is it?

 

well i just got my car re-tuned last night :D

crap does it run better, we had an air leak inlet side and exhaust first tune and the tuners laptop was niknak and slow, got all the problems sorted and its an animal now its been re-tuned on his nice shiny new laptop. enabeled both o2 sensors again to.

butt dyno says 185 hp, though booked in for a dyno in a few weeks :D

 

i dont mean to thread jack but i have a simple question my friend knows how to make custom headers and what not i want a cool looking header kind of like the ram horn manifold like the turbo ones are u guys think they r good and im probably gon do like a 3 inch collector u guys think that would look good and be good for sum power