Topic: Headers on 4 banger

[joe-joe]

Are headers going to really decrease performance in a 99 2.5L that already has a Dynomax catback? I have heard many say that the header will reduce low end torque and is not a good idea for a 4 banger. Got any advice?

[wrangler387]

It could/could not. Depends on the design of the header. A longer primary header will produce more bottom end power (so a shorter will yield more higher end), but for the most part diameter and the collector make the biggest difference. You want to use the smallest tube ID you can without hurting flow (this will give you the highest velocity). A high velocity with a true merge collector (which won't suprise me if nobody makes a good header for the 2.5L) can create a suction which obviously will help move the combustion form the cyclinder.

[snowbrew]

I just put a banks header on my '91 YJ. I really felt the engine come alive throughout the entire horsepower range. The low end torque increased a little bit, but in the upper end of the RPM range the HP was really felt.

[Skinny]

I just put a Pacesetter header on my 95, with a Magnaflow cat, and high flow straight shot Magnaflow muffler,  it opened mine up a bit, I have been suprised with the low end get up, but also the fact that I can use 4th gear again driving around town going up hills with out any hesitation. It just moved the power band a little bit higher on the RPMs but not much. Overall I think it was a good choice for me

[Jeffy]

Most headers are designed for mid-range power.

[chardrc]

does anyone hear know if you can get a header that will work with a pre 1991 yj with a 4cly with power stearing. cuz i can only find 1 header that is soposed to fit but it says it wont work if you have powerstearing becasue of how the braket is for it. so my question is does anyone know away around this problem / has put a header on their 1990 or older wrangler yj with a 4cly.

[Jeffy]

The only one I've seen was Borla's.  But i'm not sure of the particulars.

[shotgun]

I have a broken borla on one of my spare engine's. It seems incrediblly expensive at roughly $450. And the PO of my engine said he broke it twice before he went to an AMC 360. I'm looking into getting mine repaired, again before I install it.

[snowbrew]

The Banks header is ok'ed with the power steering unit.

[chardrc]

The Banks header is ok'ed with the power steering unit.

for the 1990 model.. sweet ill have to look into that then.....


thats only for the 1991 or newer 2.5l i have a 1990 so its different.. unless i mised somehting on there web site

[Oilsmoke]

I think the lose of low torque is misnomer, I now can lug without throttle with my banks heade,r But i also run a smaller oulet of 2 inch after the muffler.
seams alot better than with stock exhaust maniflod.

[chrisfranklin]

I was reading the product user reviews on JeepForum, namely the header reviews.  Guy was talking about how he installed a header on his 4.0.  A dealership mechanic then told the guy that running a header on the 4.0 would cause a lean running condition.  Said the guy needed to upgrade to different fuel injectors and tweak the MAP sensor to make it work.  So, the guy decided to remove the header, depite the fact that his Jeep seemed to be performing better.

Frankly, I am little suspicious about that mechanics advice.  The air-fuel ratio is set based on sensor readings at the intake - MAP and IAT.  You open up the exhaust with a header and this is not likely to affect the intake MAP or IAT readings is it, provided the intake set-up remains stock, right? Or do you think the MAP (manifold pressure) would fall with the exhaust opened up using a header, thus causing a lean running condition?

If the lean running condition scenario is true with a header, its troubling why manufacturers making exhausts for YJ, TJ Wranglers don't mention this when marketing their products. 

[lanulos89]

i have the pacesetter header from 4wd hardware.  even though i had an issue with the down pipe, i would still recommend it to people.  on the highway i used to struggle to do 70, have 31's 3.73's and the 3 spd auto, after the header i could easily do 75.  so if you have the opportunity to get one i'd say its worth it.  for the small price of like 200 bucks you feel the power gain.

[Erik]

the borla on my 89 2.5 has been flawless for 3 years.

i've cut and welded the piping to make it fit better as i rearranged my skid plate and rear suspension but the header itself is holding up great.  not sure why people complain about them... perhaps i am just lucky....

[Tall Boy]

I got a banks torque tube and noticed I can use 5th gear more. I also noticed that 4th gear has more power , so I do not have to row through the gears from 3rd to 4th as much.