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Question - Should I Thermal Wrap my Exhaust?

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  • Question - Should I Thermal Wrap my Exhaust?

    We get this question a lot, since we both supply long tube headers for our LS swaps as well as being known as a shop that builds road race cars for the last 20 years.


    The answer is.... not unless entirely necessary... we try to avoid that. I will explain why we don't like it, and why some feel the need to do it.

    We have not found the need in a WELL TUNED and properly running engine to wrap exhaust. We will ceramic thermal coat headers and sometimes even the entire exhaust, to both trap heat inside the exhaust tubing and keep it from radiating to nearby parts and fluids as well as for corrosion resistance. We have used a shop in Dallas called Crosslink Power Coating to do this "polished ceramic" finish for years, and it is very nice. Similar to coatings by SwainTech, JetHot, Polydyne and others.

    And we will spot wrap certain areas with DEI thermal exhaust wrap, which we will cover more below. But the least amount of this fabric based thermal wrap on a race car = the better!


    We have had a very small number of folks that noted starter issues when used with our E36 or E46 LS swap headers, and we try to answer every question we get over email. This post started as an answer to one such customer. It almost always comes down to an engine tune that is too rich, allowing for that excess fuel to burn within the exhaust headers, which can pump out a LOT of excess heat.

    We don't feel the need for any special starters, and for all of our LS builds we use this new AC Delco starter, even with over 700 hp NA engines. Our shop car 2015 Mustang "Trigger" uses this same start and has zero issues with 627 whp and a season of use.

    We did have one of our LS swap builds that suffered from enormous underhood heat issues, but it was 100% from super terrible tuning work. This was a car that was undrivable under 3500 rpms and had major issues. I will try to explain, without naming names.

    This HPR 468" LS7 in this BMW ran VERY poorly with the initial tune, and still ran terribly after this shop had touched up the tune 4 different times. The engine wouldn't idle under 1400 rpm, it would foul the spark plugs within a few minutes of running, and the headers were glowing were red at idle! An utterly incompetent tuner was in charge of this first setup and he simply didn't understand physics. He couldn't make two dyno pulls in a row within 50 whp and figure out why. "That's just how these motors do".

    Wrong. We found out after chasing this issue for months and taking it to a proper tuner, that this setup was using a broken version of a MoTeC firmware. The physics model was busted - you could make changes but the engine wouldn't respond correctly. It also had a totally busted fuel distribution issue in the firmware. Once this second tuner figured this out, it finally responded "like how physics said it should". It made an additional 80 whp, idled at 1100 rpm, wouldn't die under 3500 rpm when getting going from a stop, and best of all - the headers quit glowing red.
    In addition to too rich, not enough spark advance also puts a lot more heat into the cylinder heads and exhaust. Sometimes a ?conservative? tune can actually cause overheating issues on a NA engine.

    After posting this, I talked with Erik Koenig at lunch, and had others chime in the same response online. This is also poor tuning that rears its ugly head and creates needless engine bay heat!


    Once you are convinced that your tune isn't the cause of heat issues underhood and elsewhere on your race car, it might be time to look for specific areas where things pass too closely to hot items.

    After we fired the first tuner, this engine made 686 whp, and we ran this car on track 5 times before turning it over to the customer. We had no starter issues and it uses the same starter we use on everything. We did have to repair and replace some items under hood, like knock sensors that got cooked and a few other things that I got to pay for. All told this bad tuner cost me $15K or more in lost billing and about 10 months of wasted time. Don't cheap out on your tuner!

    Even with a full flat bottom panel on this car we still only "wrapped" about 2 feet of the exhaust, where a 3" tube bent around the differential housing and some fluid lines there. We always try to wrap the LEAST amount of the exhaust with this stuff for a reason: FIRE

    We try not to wrap exhaust headers because if you have any fluid leak of anything flammable it can soak into the header wrap. This in turn makes for a nice torch, if your engine bay ever sees a touch of fire. This fabric wrap gets brittle and worse as it ages, and makes it soak up even more fluids that can burn.

    Our LS swapped Mustang track car uses the OEM starter but we have some localized heat reflective materials and of course the entire exhaust is thermal ceramic coated. There is zero header wrap on this car's exhaust.

    For Localized Heat issues - delicate things that are placed close to exhaust - instead of the "wicking" fabric based header wrap, we will use other products by DEI and the like. Above we wrapped a spherical bearing near the exhaust primaries with some DEI aluminum / fiberglass thermal barrier. This is formable and adhesive on the fiberglass side. There is some gold DEI wrap on some sensor wiring and the clutch line you can see above, too.

    We will used this DEI aluminum / fiberglass reflective sheet on the floorpan and certain areas, places near exhaust where heat tends to build up, to keep it from transmitting into the cabin.

    Again, if your plugs look BLACK and your headers are glowing, the engine's TUNE IS JUNK. The plugs need to look cleaner near the tips and electrode straps.

    We will also wrap cerain lines with this protective DEI "fire sleeve" when we see it getting close to any major heat source.

    Thermal management is an ongoing process, and you won't likely get it 100% right on your first time on track after a new build. Longer format endurance racing poses even more challenges than W2W club racing or Time Trial use, too. Make sure you look at your race car thoroughly after each track outing, especially the first few. Notice some discoloration? Plastics melting? It might be time to relocate items, replace them and add some thermal barriers or wraps to certain sections of the exhaust. Keep looking and learning!

    We hope this quick post gives you some ideas for better thermal management AND helps you avoid the dangers of fabric based header wrap - which is super popular but in time can lead to a nasty situation if it gets soaked in oil.

    Last edited by Fair!; 12-28-2023, 06:03 PM.
    Terry Fair -
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev