Wrapped Headers???
Pro
Joined: Jun 2005
Posts: 593
Likes: 1
The biggest performance benefit of coated headers is that they help keep the heat in the exhaust system. As the exhaust gases cool, they also lose velocity.
By keeping the exhaust hot, the velocity will be higher and you will get more of a scavenging effect. At low rpm, reverse flow will be reduced also. By keeping the heat in the exhaust system, you also reduce under hood temperatures, which can really be a plus if your aircleaner is breathing under hood air.
Thermal wrap does a better job at insulating heat and reducing under hood temperatures, but they also tend to hold in moisture and cause rust.
If you use wrap on a street car, you should use a coated header to help it last. Headers will not last as long if they are run hotter, and wraps make the header run much hotter. The metal will fatigue much quicker. Gaskets will also fail sooner if the system is hotter, especially the collector gaskets.
Depending on what the header is made of coating or wrapping will cause welds to crack or cause like stainless steel to change shape.
Coatng CAT is stupid for the hotter they get the more excess fuel the PCM commands to cool the CAT off.
Changing the internal exhaust temp will effect the O2s and cause PCM to make AFR canges when it really was not needed so tuning the PCM is a must.
By keeping the exhaust hot, the velocity will be higher and you will get more of a scavenging effect. At low rpm, reverse flow will be reduced also. By keeping the heat in the exhaust system, you also reduce under hood temperatures, which can really be a plus if your aircleaner is breathing under hood air.
Thermal wrap does a better job at insulating heat and reducing under hood temperatures, but they also tend to hold in moisture and cause rust.
If you use wrap on a street car, you should use a coated header to help it last. Headers will not last as long if they are run hotter, and wraps make the header run much hotter. The metal will fatigue much quicker. Gaskets will also fail sooner if the system is hotter, especially the collector gaskets.
Depending on what the header is made of coating or wrapping will cause welds to crack or cause like stainless steel to change shape.
Coatng CAT is stupid for the hotter they get the more excess fuel the PCM commands to cool the CAT off.
Changing the internal exhaust temp will effect the O2s and cause PCM to make AFR canges when it really was not needed so tuning the PCM is a must.
Le Mans Master
Joined: Mar 2002
Posts: 5,253
Likes: 50
From: Sandy Eggo Calif.
St. Jude Donor '06-'07-'08-'09-'10-'11-'12, '16
Originally Posted by boosted_z06
Coatng CAT is stupid for the hotter they get the more excess fuel the PCM commands to cool the CAT off.
Pro
Joined: Jun 2005
Posts: 593
Likes: 1
Originally Posted by TommyV
My mileage has improved, so I'm not sure what you mean. Cat's are suppose to run hot.
The PCM is assuming what the CAT temp is only by what the O2s report so coating exhaust also then reflects what the O2s report.
Safety Car
Joined: Dec 2004
Posts: 3,565
Likes: 5
From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
Originally Posted by boosted_z06
No they are supposed to operate over a set temp range and when they get over that temp the PCM kicks in COT ( Cat OverTemp) which dumps fuel in to cool the Cat and why people call when at WOT being pig rich.
The PCM is assuming what the CAT temp is only by what the O2s report so coating exhaust also then reflects what the O2s report.
The PCM is assuming what the CAT temp is only by what the O2s report so coating exhaust also then reflects what the O2s report.
Safety Car
Joined: Sep 2005
Posts: 4,369
Likes: 179
From: Road Atlanta You do the MATH!
Originally Posted by boosted_z06
The biggest performance benefit of coated headers is that they help keep the heat in the exhaust system. As the exhaust gases cool, they also lose velocity.
By keeping the exhaust hot, the velocity will be higher and you will get more of a scavenging effect. At low rpm, reverse flow will be reduced also. By keeping the heat in the exhaust system, you also reduce under hood temperatures, which can really be a plus if your aircleaner is breathing under hood air.
Thermal wrap does a better job at insulating heat and reducing under hood temperatures, but they also tend to hold in moisture and cause rust.
If you use wrap on a street car, you should use a coated header to help it last. Headers will not last as long if they are run hotter, and wraps make the header run much hotter. The metal will fatigue much quicker. Gaskets will also fail sooner if the system is hotter, especially the collector gaskets.
Depending on what the header is made of coating or wrapping will cause welds to crack or cause like stainless steel to change shape.
Coatng CAT is stupid for the hotter they get the more excess fuel the PCM commands to cool the CAT off.
Changing the internal exhaust temp will effect the O2s and cause PCM to make AFR canges when it really was not needed so tuning the PCM is a must.
By keeping the exhaust hot, the velocity will be higher and you will get more of a scavenging effect. At low rpm, reverse flow will be reduced also. By keeping the heat in the exhaust system, you also reduce under hood temperatures, which can really be a plus if your aircleaner is breathing under hood air.
Thermal wrap does a better job at insulating heat and reducing under hood temperatures, but they also tend to hold in moisture and cause rust.
If you use wrap on a street car, you should use a coated header to help it last. Headers will not last as long if they are run hotter, and wraps make the header run much hotter. The metal will fatigue much quicker. Gaskets will also fail sooner if the system is hotter, especially the collector gaskets.
Depending on what the header is made of coating or wrapping will cause welds to crack or cause like stainless steel to change shape.
Coatng CAT is stupid for the hotter they get the more excess fuel the PCM commands to cool the CAT off.
Changing the internal exhaust temp will effect the O2s and cause PCM to make AFR canges when it really was not needed so tuning the PCM is a must.
Race Director
Joined: Jan 2000
Posts: 12,375
Likes: 406
From: Florida
Originally Posted by boosted_z06
No they are supposed to operate over a set temp range and when they get over that temp the PCM kicks in COT ( Cat OverTemp) which dumps fuel in to cool the Cat and why people call when at WOT being pig rich.
In fact, hotter exhaust temps actually LOWER the operating temps inside the catalyst because there are fewer hydrocarbons to be processed.
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