99Hugger

iTrader: (3)

I was border line lean on my last dyno, which was about 6 months ago. Just got the car dyno'ed again last weekend after installing LT's and ORP. I've lost 10rwhp and 15lbs of tq . My a/f numbers were really bad, super lean at 16.1 at 5500 rpms.

I've always heard that headers will put you on the rich side. Has anyone else gone lean after headers or is it something else? Guy at the dyno shop told me it just needed tunning and that the headers could very well cause a lean condition since the flow of air is so much less restricted and the stock PCM tunning can only compensate so much more fuel. Kinda makes sense, but he could also just be trying to drum up some business. I know tunning is beneficial after a header install, but shouldn't I seen some kind of gain without the tunning?

I did add ported MAF ends, but would that really cause that big of a lean out?

Here's a link to my dyno graph with the wide band. Mods are also listed on the page. http://dynoperformance.com/search_details.php?ID=630

Let me hear what you guys think...
Thanks in advance

Tranzor

Here's a good explaination...

https://ls1tech.com/forums/generation-iii-external-engine/93593-would-somebody-explain-what-longtubes-will-do-my-air-fuel.html

99Hugger

iTrader: (3)

Ok... that explains why headers may cause a rich condition, good info. But why would I go lean. Based on that link shouldn't the mix have become a little richer? How much extra fuel can the PCM actually compensate for? Or do ya's think this is a totally separate issue not being caused by the headers?

Slowhawk

iTrader: (12)

Looks like you can just get away with a MAFT to richen up your car..Each car is different.Headers do richen the car,but ported ends on a MA lean the A/F out...Your ported ends won!!

99Hugger

iTrader: (3)

Yea, I agree a MAFT is definitely in order. At least to hold me over until I get it tunned when the cam is in. I didn't think that just MAF ends would put me that lean. Thx for the replies...