jf1sf5
Forum Member
- Joined
- Aug 5, 2012
- Messages
- 2,089
- Location
- Switzerland
- Car Year
- '97
- Car Model
- Forester
- Transmission
- Manual
I have always thought that n/a motors need equal length headers for better power and torque, am I wrong ?
I have always thought that n/a motors need equal length headers for better power and torque, am I wrong ?
Right bit of misinformation here. Even the cheapest ebay UEL headers will add power over the stock header unless you have a ej204 ej253 ie newer avcs motor. The stock headers are ridiculously restriced with tiny diameter short primaries and if you cut one open you will see sharp poorly formed joins that jut out obstructing flow.
While I agree on the joints that obstruct flow, I don’t agree on the primary runners being too small. A mates dad that’s been in the exhaust building game longer than I’ve been on this earth tells me the runners are far too large for the size of the engine. To get better exhaust gas velocity the primaries need to be smaller, and those joints smoother.
Just swapping UELs on a factory system might give a small note change but not worth it in my opinion unless you add a cat back system with a sports muffler that’ll let more noise out
As for power you might lose a tiny amount but really you’re not going to notice the difference with a nice note to listen to...
Cheers
Bennie
I wouldn't advise putting headers alone on any car its pointless. To see gains you would need to replace the whole system including decat. The diameter of the primaries may be adequate for a road car but the length of the primaries are short like 6" short. Back pressure and gas velocity has been debated to death over the years and in tge US everyone swears by a exhaust bore of 2.25" but in the UK motorsport engine and exhaust builders say if its producing over 150bhp it needs to be 2.5". Likewise manifold primaries are often 1.75" diameter and anywhere from 12-18" in length depending on the compression,cams and where peak tourqe is found in the rev range. These guys regularly see 135bhp per litre on NA competition engines. There is a guy locally to me that consistently gets 320+bhp from 2.5 duratecs on throttle bodies. Surely some of the same practice can be transfered across.