Why do headers make our engines run rich or
Thread Starter
12 Second Club
Joined: Apr 2002
Posts: 680
Likes: 0
From: Cave Creek, AZ- Canada Also.
Why do headers make our engines run rich or is this just a misnomers. 
Why would they effect A/F ratio or is it just because the O2 sensors are place so far down the pipe (as opposed to stock placement) and people see their reading are richer and take it that the car is running richer and it really isn't.We just need to get a proper reading on the dyno.
Your thoughts.
Why would they effect A/F ratio or is it just because the O2 sensors are place so far down the pipe (as opposed to stock placement) and people see their reading are richer and take it that the car is running richer and it really isn't.We just need to get a proper reading on the dyno.
Your thoughts.
On a related note, if I'm adding an LS6 intake (I have a 2000) and a ported throttle bottle (potentially increasing the air taken in) at the same time as long tubes and an ORY (getting more air out and faster) is there a chance that the A/F could go somewhat unaffected staying within acceptable parameters?
Or am I not even close with this theory LOL?
Or am I not even close with this theory LOL?
TECH Apprentice
Joined: Jan 2004
Posts: 328
Likes: 0
From: Los Angeles, CA
You can see from my mods, I've got a free-flowing intake and exhaust. The other day I was logging A/Fs with my stock tune and saw mid- to high-13s. I would think the the increased airflow, both entering into (airbox, CAI, MAF) and scavenging from the exhaust (LTs, ORY, LM), is leaning out my mixtures. I'll be going by the office tomrrow and will definitely remember to get my LS1 edit equipment for some weekend tuning fun.
Thread Starter
12 Second Club
Joined: Apr 2002
Posts: 680
Likes: 0
From: Cave Creek, AZ- Canada Also.
From what I have read headers do make or trick the puter into thinking your running rich ie more air flow so the puter dumps in more fuel to compensate.
My Q is if my Ltrim #'s are -5 and -6 cruising and go 0 at WOT but I feel the car is a little lean by adding more fuel will this actually bring my Ltrims #'s more neg or will they show a more pos number on my Predator.
Thanxs
My Q is if my Ltrim #'s are -5 and -6 cruising and go 0 at WOT but I feel the car is a little lean by adding more fuel will this actually bring my Ltrims #'s more neg or will they show a more pos number on my Predator.
Thanxs
On The Tree
Joined: Dec 2002
Posts: 112
Likes: 0
From: Central FL
I'd say it has to do with the fact that headers move the O2 sensor further away from the exhaust port. The components that make up emissions are highly dependent on temperature, and allowing them to cool before they get to the sensor will likely change their make-up. Of course, your computer doesn't know that you've moved the O2 sensor, so it treats those exhaust components as if they're occuring close to the ports as if you've still got the sensor in the stock location.
TECH Apprentice
Joined: Jan 2003
Posts: 308
Likes: 0
From: Mission Viejo CA
99SSragtop is correct, the LT headers cause the PCM to think your running lean so it starts dumping fuel to compensate, AKA your AF becomes pig rich. The O2sims are to tell the PCM that your CAT's are up to temp and thus not throw a code. When tuning with the Predator your only changing the WOT AF, it doesn't affect the regular driving. The tune they put in does but my understanding is that you can't affect the LTrims for normal driving without having them give you a custom tune. +1/+2 to -2/-6 are what everyone sees with normal cruising.
Trending Topics
TECH Enthusiast
Joined: Jul 2002
Posts: 618
Likes: 0
From: Pensacola, FL
None of this makes sense...
I do not know the answer for the exact question, but I do know some basic facts about headers and O2 sensors:
1) Headers make any other car run lean because of the increase in airflow.
2) O2 sensors work off temperature.
3) Headers run much cooler than manifolds, they dissapate the heat faster.
Now, if you put all these things together, here's what it should look like...
The sensors are moved further down the exhaust AND the headers run cooler. Therefore both of these things combined would cause the computer to think the car is rich because cooler sensors are rich sensors. Hot sensors are lean.
So you hook up a monitor and the sensors are cold, your monitor tells you that you are rich, but you aren't, the sensors are fooled.
Combine that with the computer pulling out fuel and headers inherently running lean, you could be running dangerously lean and not even know it! You look at the monitor and you see rich, but it is showing you cold sensors, not correct sensors.
Something to think about.
As long as the computer is tricked, so are you when you hook up a monitor program.
I don't know that this is how it goes, but I have a sneaking suspicion that this is more of a problem than folks think...
A problem that could potentially burn a piston or valve.
Dave
I do not know the answer for the exact question, but I do know some basic facts about headers and O2 sensors:
1) Headers make any other car run lean because of the increase in airflow.
2) O2 sensors work off temperature.
3) Headers run much cooler than manifolds, they dissapate the heat faster.
Now, if you put all these things together, here's what it should look like...
The sensors are moved further down the exhaust AND the headers run cooler. Therefore both of these things combined would cause the computer to think the car is rich because cooler sensors are rich sensors. Hot sensors are lean.
So you hook up a monitor and the sensors are cold, your monitor tells you that you are rich, but you aren't, the sensors are fooled.
Combine that with the computer pulling out fuel and headers inherently running lean, you could be running dangerously lean and not even know it! You look at the monitor and you see rich, but it is showing you cold sensors, not correct sensors.
Something to think about.
As long as the computer is tricked, so are you when you hook up a monitor program.
I don't know that this is how it goes, but I have a sneaking suspicion that this is more of a problem than folks think...
A problem that could potentially burn a piston or valve.
Dave
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0
Brett Foote
10 Reasons the LS7 Is GM's Most Extreme Naturally Aspirated V8 Engine Ever
Verdad Gallardo Thread Starter
12 Second Club
Joined: Apr 2002
Posts: 680
Likes: 0
From: Cave Creek, AZ- Canada Also.
This **** is driving me crazy.
Ive been fooling around with the predater power enrichment settings.Right now Im at the settings I had when I had the stock exhaust.Those setting were PE -.48 and spark was + 4.98.Numbers looked good WOT ie O2's = .098 and no KR.
Now my numbers with thiese settings are slightly neg like before but sometimes jump positive just off excelleration and when the car has been sitting for 15 to 30 mins.
I guess I take the positive LTRIM numbers because of extra air coming into the exhaust like someone has mentioned above.
I maybe inclined to leave my setting that I have now and see how things work out and until I go and get a dyno tune because I can't get a good reading for my O2's at WOT.
Even with a dyno tune (can someone explain) how they go about it.Do they take out one O2 sensor Bank 1 say and hook up the dynos O2 ? If this is the case how can this be accurate when the O2 sensor is way down the pipe (unlike the stock location) and are we truly getting a good figure on our A/F ratio.
I need a beer right now and cook a Bison burger.
Ive been fooling around with the predater power enrichment settings.Right now Im at the settings I had when I had the stock exhaust.Those setting were PE -.48 and spark was + 4.98.Numbers looked good WOT ie O2's = .098 and no KR.
Now my numbers with thiese settings are slightly neg like before but sometimes jump positive just off excelleration and when the car has been sitting for 15 to 30 mins.
I guess I take the positive LTRIM numbers because of extra air coming into the exhaust like someone has mentioned above.
I maybe inclined to leave my setting that I have now and see how things work out and until I go and get a dyno tune because I can't get a good reading for my O2's at WOT.
Even with a dyno tune (can someone explain) how they go about it.Do they take out one O2 sensor Bank 1 say and hook up the dynos O2 ? If this is the case how can this be accurate when the O2 sensor is way down the pipe (unlike the stock location) and are we truly getting a good figure on our A/F ratio.
I need a beer right now and cook a Bison burger.
Last edited by 99SSragtop; Jul 10, 2004 at 05:55 PM.
TECH Enthusiast
Joined: Jul 2002
Posts: 618
Likes: 0
From: Pensacola, FL
I dunno...
I have always been against ceramic coated headers. I consider coating to be 'snake oil'.
I am rethinking that idea. Not for all engines, just the LS1 because of it's computer and sensors. If the ceramic holds in heat, it seems it might improve sensor accuracy on LT applications.
However, that is the only reason I would ever consider ceramic coated headers. It's funny that all the reasons they advertise the need for coating are 'bunk', and the one reason you could think of that is important, they never considered.
Also, another way to check sensor accuracy would be to read the plugs from time to time and see what they tell you is really going on in the combustion chamber.
Dave
I have always been against ceramic coated headers. I consider coating to be 'snake oil'.
I am rethinking that idea. Not for all engines, just the LS1 because of it's computer and sensors. If the ceramic holds in heat, it seems it might improve sensor accuracy on LT applications.
However, that is the only reason I would ever consider ceramic coated headers. It's funny that all the reasons they advertise the need for coating are 'bunk', and the one reason you could think of that is important, they never considered.
Also, another way to check sensor accuracy would be to read the plugs from time to time and see what they tell you is really going on in the combustion chamber.
Dave
Thread Starter
12 Second Club
Joined: Apr 2002
Posts: 680
Likes: 0
From: Cave Creek, AZ- Canada Also.
I did pull one passenger and one driver side plug out and they did look a little white tanish so I have richened up the mixture a little ( looking for a nice tan colour).I know its really one of the best ways of checking A/F ratio mixtures especially if you have headers for as we all know headers and their O2 locations are far from perfect.
TECH Enthusiast
Joined: Jul 2002
Posts: 618
Likes: 0
From: Pensacola, FL
I just had a brainstorm...
I do not know if my thinking is correct though, I have never used an edit program.
Here it is though, food for thought if anything:
The sensor does not distingush the O2 level in the exhaust. As a matter of fact, all it does is turn exhaust gas temp into an electrical voltage. Kinda a modified EGT sender, which is the mechanical version.
Okay, the O2 sender converts temp level into current level.
Now the computer analyzes the data... it looks at a chart that says 'on an LS1, if the voltage recieved is .xxx, the exhaust gas temp is xxxx*", then the next chart says "xxxx* EGT reading on a stock LS1 means the car is rich (or lean).
Now, if we figure the sensor is cooler and essentially uncalibrated after LT install, would it not be possible to calibrate it?
Can you take your edit program and open the chart for exhaust gas temp, or 02 voltage definitions, and skew it slightly to compensate for cooler readings?
This would calibrate everything and put you back on an even keel, assuming that access to this chart in the PCM is even possible with an edit program.
Does this make sense?
Dave
I do not know if my thinking is correct though, I have never used an edit program.
Here it is though, food for thought if anything:
The sensor does not distingush the O2 level in the exhaust. As a matter of fact, all it does is turn exhaust gas temp into an electrical voltage. Kinda a modified EGT sender, which is the mechanical version.
Okay, the O2 sender converts temp level into current level.
Now the computer analyzes the data... it looks at a chart that says 'on an LS1, if the voltage recieved is .xxx, the exhaust gas temp is xxxx*", then the next chart says "xxxx* EGT reading on a stock LS1 means the car is rich (or lean).
Now, if we figure the sensor is cooler and essentially uncalibrated after LT install, would it not be possible to calibrate it?
Can you take your edit program and open the chart for exhaust gas temp, or 02 voltage definitions, and skew it slightly to compensate for cooler readings?
This would calibrate everything and put you back on an even keel, assuming that access to this chart in the PCM is even possible with an edit program.
Does this make sense?
Dave
TECH Enthusiast
Joined: Jul 2002
Posts: 618
Likes: 0
From: Pensacola, FL
Originally Posted by 99SSragtop
I did pull one passenger and one driver side plug out and they did look a little white tanish so I have richened up the mixture a little ( looking for a nice tan colour).I know its really one of the best ways of checking A/F ratio mixtures especially if you have headers for as we all know headers and their O2 locations are far from perfect.
Your plugs seem to read lean.
What does your scanner say?
If it says lean, our theory is blown out of the water.
If it says rich, we are on the right track... the scanner is wrong.
Dave
Thread Starter
12 Second Club
Joined: Apr 2002
Posts: 680
Likes: 0
From: Cave Creek, AZ- Canada Also.
Dave, the Predator read .096 give or take on the O2's.Yes the scanner (O2' anyways) is wrong.What Im at now for tuning is + .30 on PE and only + 1.43 on spark ( 28.4 advance WOT).O2's were .92 ish on b1 and .94 ish on b2 this was only one good run on the highway.
My numbers before headers (James tune for 0 Ltrims) were PE -.43 and spark +4.98
One question about spark advance,If Im at 28.4 total advance at WOT and I add more will I get more advance or does the PCM hood it at say 29.
My numbers before headers (James tune for 0 Ltrims) were PE -.43 and spark +4.98
One question about spark advance,If Im at 28.4 total advance at WOT and I add more will I get more advance or does the PCM hood it at say 29.
I used to have a great link to an article about the effects of headers on an engine.....
Yes headers make you run richer.
the o2's basically think that you have a different ratio because of the temperature difference they see from being moved over a foot from where the factory ones sit....the 02's read lean...so the computer dumps in more fuel to compensate....Its not usually a huge amount..but you will run richer...
Yes headers make you run richer.
the o2's basically think that you have a different ratio because of the temperature difference they see from being moved over a foot from where the factory ones sit....the 02's read lean...so the computer dumps in more fuel to compensate....Its not usually a huge amount..but you will run richer...
Ratio411
Put your theory to rest. My car and my brothers car both ran rich when we installed LT headers. We are talking about a computerized car that makes changes based on info it receives from ins sensor. I do agree that in old school rides it may make the car run lean because you don't have the cpu making changes. Not trying to hate. Just trying to help.
Put your theory to rest. My car and my brothers car both ran rich when we installed LT headers. We are talking about a computerized car that makes changes based on info it receives from ins sensor. I do agree that in old school rides it may make the car run lean because you don't have the cpu making changes. Not trying to hate. Just trying to help.
