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June 08, 2005
G'day all
Let's start with a definition. Those non-standard tubular pipes that bolt onto your cylinder head to let the exhaust gas out, and eventually join into one "collector" for the exhaust pipe, are called "extractors" or in some languages "headers". "Exhaust" includes these plus everything down the line, past the muffler to the chrome tip on the tail pipe. I guess we are talking here about insulating the extractors, not the entire exhaust system.
We run in all our engines on a calibrated engine dyno. It lives in a 10ft x 15ft brick room with a huge fan to keep things comfortable.
We have run quite a number of engines back to back with mild steel painted extractors, and with ceramic coated extractors, and there is absolutely no difference in power output.
Now before you jump in and say "But .....", you are quite correct. An engine dyno room doesn't replicate the engine bay of your car. In the dyno room, the fan is blowing ambient air over the carby inlets, as well as cooling the exhaust system, so there isn't much chance of the carby inhaling hot air from the exhaust. However it is interesting (at least, I think so) that the "keeping the hot air in the exhaust cos it flows better" seems to be disproven by this test.
Despite the above result, we use and recommend ceramic coating the extractors. Why?
1) It does keep the engine bay cooler during slow running, gridding on race starts etc, and that can't hurt.
2) It protects both inside and outside of the extractors, eliminating rust which will destroy them over time.
3) It looks pretty.
Before ceramic coating, we used to wrap them in asbestos tape. Kept the engine bay cool, but it unravelled, it held in water so promoting rust, and it looked ugly.
avagoodday
Colin
"Colin Dodds" < colin@... > 37462
Posted on June 8, 2005 08:48 AM
Posted to category(s) Cooling System | Cylinder Head | Engine (external) | Engine (internal) | Exhaust System | Fuel System | Intake System | Lubrication System | Miscellaneous | Racing | Restoration | Tuning
