why do headers make u run rich?
Depending on where your O2s are relocated, and how
much heat you lose, you can see a very different or
even dead output. Colder O2s will read higher voltage
for the same actual mixture (when they are hot enough
to work). This is easily misinterpreted as being richer.
Dropping EGT from 750C to 500C makes a 70mV higher
output voltage, the same as swinging mixture (at 750)
from 13:1 to 10:1.
When they're too cold to work, they put out a low
voltage. The PCM would interpret this as an over-
lean condition and trim for it, making you truly rich as
a result. This only pertains to closed loop.
You would want to have the car tuned at a place that
uses a wideband O2 device so you know the truth of
the situation.
Headers should improve volumetric efficiency and give
you a cylinder fill that is more fresh air and less spent.
This should in fact make you lean, given the same fuel
shot. But lots of people say they make the LS-1 richer.
Whether this is true, only the wideband (before & after)
can tell in your particular case.
much heat you lose, you can see a very different or
even dead output. Colder O2s will read higher voltage
for the same actual mixture (when they are hot enough
to work). This is easily misinterpreted as being richer.
Dropping EGT from 750C to 500C makes a 70mV higher
output voltage, the same as swinging mixture (at 750)
from 13:1 to 10:1.
When they're too cold to work, they put out a low
voltage. The PCM would interpret this as an over-
lean condition and trim for it, making you truly rich as
a result. This only pertains to closed loop.
You would want to have the car tuned at a place that
uses a wideband O2 device so you know the truth of
the situation.
Headers should improve volumetric efficiency and give
you a cylinder fill that is more fresh air and less spent.
This should in fact make you lean, given the same fuel
shot. But lots of people say they make the LS-1 richer.
Whether this is true, only the wideband (before & after)
can tell in your particular case.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
so i will no longer be able to use the o2's for basic tuning? what about after the car is really really hot and they had time to get nice and toasty? will the LTFT's be effected if its running any richer?
Originally Posted by WS6FirebirdTA00
so i will no longer be able to use the o2's for basic tuning? what about after the car is really really hot and they had time to get nice and toasty? will the LTFT's be effected if its running any richer?
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Getting the headers coated will help with the car running rish after headers. The ceramic coating will help retain heat making the o2's run at a more effecient temp. I had that problem on my old truck. The headers made it run obnoxouisly rich, you could really tell after the cats were gutted. Once I took the headers off and put the manifolds back on, all was good again. For the new truck, I got them coated before I put them on, and they work great. My fuel mileage improved as to where it went down on the other truck.
These were the same exact headers too, only difference was the coatings and the truck.
Another observation I made, is that running open headers will make the engine run horribly rich. I went through 2 sets of plugs in about 30 miles. What happens is fresh air comes back up into the header passing over the hotter o2 which is more sensitive. The fresh air told the o2's it was running super lean, and it started dumping fuel in. I saw STFT's as high as +55. That wasn't when it set the SES light for lean codes on both banks either.
These were the same exact headers too, only difference was the coatings and the truck.
Another observation I made, is that running open headers will make the engine run horribly rich. I went through 2 sets of plugs in about 30 miles. What happens is fresh air comes back up into the header passing over the hotter o2 which is more sensitive. The fresh air told the o2's it was running super lean, and it started dumping fuel in. I saw STFT's as high as +55. That wasn't when it set the SES light for lean codes on both banks either.
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Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
ok so i went out there and checked my o2s. yea yea yea i know its not accurate but i have no other way to do it right now. my fuel trims barely changed, if anythign they are slightly negative. i took a few runs and right after the fuel trims read -.78% where before they were 0-.78%. now the o2's are reading 945 mV consistenly. question is can i get these down to 920's and be ok with it until i can get a wide band? i have no knock or pinging and the car doesnt feel as strong as i would have thought after doing headers.
The collective thinking on here is that tuning via 02's is good to a point.
You could try leaning it out to like 890-900 that's as far as I would take it by say using a MAF-T at the track. I'd go a little at a time.
You could try leaning it out to like 890-900 that's as far as I would take it by say using a MAF-T at the track. I'd go a little at a time.
