Why do headers make our engines run rich or
TECH Enthusiast
Joined: Jul 2002
Posts: 618
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From: Pensacola, FL
Originally Posted by Bowtieman4life
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.
O2 sensors work off temperature.
If the header moves them back to a cooler spot (not to mention the headers run cooler anyway), then the sensor picks up a cooler exhaust gas temp. Cooler, to the sensor, means more unburnt fuel in the mix, therefore rich.
The point is, the man's scanner is telling him the car is running rich after headers, but the plugs read lean.
This fits, because the PCM is tricked by cooler EGT to think the car is rich... But, as any old schooler knows, headers cause a lean condition, then add to that the PCM just might be pulling more fuel to cure the cool O2 sensors.
Yes, I understand all of you may have seen 'rich' on your scanners and edit programs after headers, but from what we are seeing here, the truth is that the PCM, therefore your scanners, are tricked into that reading.
I will ask again...
Can LS1 edit get into the PCM and recalibrate the EGT chart to compensate for the cooler O2 sensor?
Dave
Originally Posted by ratio411
I think you guys are missing the point of the thread:
O2 sensors work off temperature.
If the header moves them back to a cooler spot (not to mention the headers run cooler anyway), then the sensor picks up a cooler exhaust gas temp. Cooler, to the sensor, means more unburnt fuel in the mix, therefore rich.
The point is, the man's scanner is telling him the car is running rich after headers, but the plugs read lean.
This fits, because the PCM is tricked by cooler EGT to think the car is rich... But, as any old schooler knows, headers cause a lean condition, then add to that the PCM just might be pulling more fuel to cure the cool O2 sensors.
Yes, I understand all of you may have seen 'rich' on your scanners and edit programs after headers, but from what we are seeing here, the truth is that the PCM, therefore your scanners, are tricked into that reading.
I will ask again...
Can LS1 edit get into the PCM and recalibrate the EGT chart to compensate for the cooler O2 sensor?
Dave
O2 sensors work off temperature.
If the header moves them back to a cooler spot (not to mention the headers run cooler anyway), then the sensor picks up a cooler exhaust gas temp. Cooler, to the sensor, means more unburnt fuel in the mix, therefore rich.
The point is, the man's scanner is telling him the car is running rich after headers, but the plugs read lean.
This fits, because the PCM is tricked by cooler EGT to think the car is rich... But, as any old schooler knows, headers cause a lean condition, then add to that the PCM just might be pulling more fuel to cure the cool O2 sensors.
Yes, I understand all of you may have seen 'rich' on your scanners and edit programs after headers, but from what we are seeing here, the truth is that the PCM, therefore your scanners, are tricked into that reading.
I will ask again...
Can LS1 edit get into the PCM and recalibrate the EGT chart to compensate for the cooler O2 sensor?
Dave
I forgot about that...
thats why headers can cause you to burn a valve.......
forgot it just reads rich...even though it leans you out normally...
I think I sort of got
....but not like full owned.....just enough to cause chaffing 
Staging Lane
Joined: Apr 2004
Posts: 71
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I believe that LS1 edit can do that. You may want to ask in the PCM tuners
section. The 02 sensors have to be very hot to give accurate readings, in fact
I'm told they actually contain heating elements to get them to operating temp
very quickly, even on a cold engine.
section. The 02 sensors have to be very hot to give accurate readings, in fact
I'm told they actually contain heating elements to get them to operating temp
very quickly, even on a cold engine.
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formerly BlacKSS2oo2 (9-20-2012)
Joined: Feb 2004
Posts: 135
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From: houston, tx
Originally Posted by 99SSragtop
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.
Man, Diablo predator sucks *** man...I had one and could never get the tune right. I just went to MTI in houston and got jayson to tune it for me..The diablo tune was setting my a/f to 11.5 and 3 degreees kr, pathedic. Heh my advise is to get rid of that peice of **** daiblo
Thread Starter
12 Second Club
Joined: Apr 2002
Posts: 680
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From: Cave Creek, AZ- Canada Also.
Originally Posted by BlacKSS2oo2
Man, Diablo predator sucks *** man...I had one and could never get the tune right. I just went to MTI in houston and got jayson to tune it for me..The diablo tune was setting my a/f to 11.5 and 3 degreees kr, pathedic. Heh my advise is to get rid of that peice of **** daiblo
See ya
Teching In
Joined: Feb 2004
Posts: 41
Likes: 0
If the sensors are reading cooler, why not move them closer to the engine. This would probably mean placing it in one of the primary tubes, but shouldn't the ratio in one of the cylinders be close to the rest on that bank?
Headers create a rich condition because,
To understand this reason consider MASS AIR FLOW, not pressure. The mass of air is what creates power with fuel. The object of creating power is trapping as much Mass in the chamber as possible.
Headers increase the mass through the exhaust mostly through the overlap. Engines are designed utilizing the exhaust pressure of the stock exhaust and work back to design a cam that satisfies this condition. Relieving this pressure allows more MASS to escape through the overlap. In a naturally aspirated engine this reduces the intake port pressure and subsequent less mass enters the engine as a proportion of the total sensed at the MAF sensor.
In effect the engine is fueling for more MASS then is actual needed for combustion. The O2 snesors take care of this in closed loop and you have to tune for this in Open Loop.
The headers help power in the NA condition in 2 ways:
Cool the chamber with additional flow allowing more timing and
May encourage addition MASS into the Engine, but not always.
But then again I could be wrong.
To understand this reason consider MASS AIR FLOW, not pressure. The mass of air is what creates power with fuel. The object of creating power is trapping as much Mass in the chamber as possible.
Headers increase the mass through the exhaust mostly through the overlap. Engines are designed utilizing the exhaust pressure of the stock exhaust and work back to design a cam that satisfies this condition. Relieving this pressure allows more MASS to escape through the overlap. In a naturally aspirated engine this reduces the intake port pressure and subsequent less mass enters the engine as a proportion of the total sensed at the MAF sensor.
In effect the engine is fueling for more MASS then is actual needed for combustion. The O2 snesors take care of this in closed loop and you have to tune for this in Open Loop.
The headers help power in the NA condition in 2 ways:
Cool the chamber with additional flow allowing more timing and
May encourage addition MASS into the Engine, but not always.
But then again I could be wrong.
Teching In
Joined: Jul 2004
Posts: 4
Likes: 0
From: Rochester, NY
Ratio411, O2 sensors depend on temperature, but do not give readings based on temperature. They do need to reach operating temp before the readings will be real, but the voltage signal from them comes from the electro-chemical potential between the metaloceramic coating on the electrode and the metal it's coated on. It's a little more complicated than that, but it does not read teperature. If you guys try to tune your mixture using temp, please make sure you're completely bent over, use plenty of lube, and for God's sake, don't use a glass thermometer.Check out this link to the Bosch USA website. It gives you all you need.
http://www.boschusa.com/AutoParts/FAQs/OxygenSensors/
http://www.boschusa.com/AutoParts/FAQs/OxygenSensors/
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.
If you did do it this way ignore my babble. Just thought I would throw that out there
TECH Addict
Joined: Mar 2004
Posts: 2,336
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From: Fat Chance Hotel
Originally Posted by PowerSpooge
Ratio411, O2 sensors depend on temperature, but do not give readings based on temperature. They do need to reach operating temp before the readings will be real, but the voltage signal from them comes from the electro-chemical potential between the metaloceramic coating on the electrode and the metal it's coated on. It's a little more complicated than that, but it does not read teperature. If you guys try to tune your mixture using temp, please make sure you're completely bent over, use plenty of lube, and for God's sake, don't use a glass thermometer.Check out this link to the Bosch USA website. It gives you all you need.
http://www.boschusa.com/AutoParts/FAQs/OxygenSensors/
http://www.boschusa.com/AutoParts/FAQs/OxygenSensors/
Teching In
Joined: Jul 2004
Posts: 4
Likes: 0
From: Rochester, NY
Originally Posted by technical
Brings me back to my question of heated O2 sensors. Once they're hot, they should read fine regardless of placement unless they're behind the cats.
TECH Enthusiast
Joined: Jul 2002
Posts: 653
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From: Mannheim, Germany
If you still don't understand why headers cause a rich condition, read the quote over and over until you do. The key point is the part about overlap (when the intake and exhaust ports are both open)
It took me a few times of reading but it makes great sense. I know my car's rich since my plugs are so blackened.
BillC5, is a MAFTuner the cheapest/easiest way to get my A/F dialed in somewhat close? I don't want to pay for tuning but I'm running way rich. Is there a cheapo way? (ie put a resistor inline with the air intake temp sensor or MAF or something like that)
It took me a few times of reading but it makes great sense. I know my car's rich since my plugs are so blackened.
BillC5, is a MAFTuner the cheapest/easiest way to get my A/F dialed in somewhat close? I don't want to pay for tuning but I'm running way rich. Is there a cheapo way? (ie put a resistor inline with the air intake temp sensor or MAF or something like that)
Originally Posted by billc5
Headers create a rich condition because,
To understand this reason consider MASS AIR FLOW, not pressure. The mass of air is what creates power with fuel. The object of creating power is trapping as much Mass in the chamber as possible.
Headers increase the mass through the exhaust mostly through the overlap. Engines are designed utilizing the exhaust pressure of the stock exhaust and work back to design a cam that satisfies this condition. Relieving this pressure allows more MASS to escape through the overlap. In a naturally aspirated engine this reduces the intake port pressure and subsequent less mass enters the engine as a proportion of the total sensed at the MAF sensor.
In effect the engine is fueling for more MASS then is actual needed for combustion. The O2 snesors take care of this in closed loop and you have to tune for this in Open Loop.
The headers help power in the NA condition in 2 ways:
Cool the chamber with additional flow allowing more timing and
May encourage addition MASS into the Engine, but not always.
But then again I could be wrong.
To understand this reason consider MASS AIR FLOW, not pressure. The mass of air is what creates power with fuel. The object of creating power is trapping as much Mass in the chamber as possible.
Headers increase the mass through the exhaust mostly through the overlap. Engines are designed utilizing the exhaust pressure of the stock exhaust and work back to design a cam that satisfies this condition. Relieving this pressure allows more MASS to escape through the overlap. In a naturally aspirated engine this reduces the intake port pressure and subsequent less mass enters the engine as a proportion of the total sensed at the MAF sensor.
In effect the engine is fueling for more MASS then is actual needed for combustion. The O2 snesors take care of this in closed loop and you have to tune for this in Open Loop.
The headers help power in the NA condition in 2 ways:
Cool the chamber with additional flow allowing more timing and
May encourage addition MASS into the Engine, but not always.
But then again I could be wrong.
TECH Addict
Joined: Mar 2004
Posts: 2,336
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From: Fat Chance Hotel
Headers causing a rich condition is still not a function of O2 placement in the header 6-12" farther downstream than in a manifold...there's two debates co-mingled here. It stands to reason that it's a mechanical issue (overlap/airflow) not an electrical ( O2).
