Out of curiosity, I decided to check exhaust manifolds temperatures in my F355. I found something a little disturbing. At engine start, half of the engine was running cooler than the other. Left bank at 200°C (400°F) and right bank, 50°C (120°F). I am new to ferraries, but the exhaust sides should run even, unless something is wrong with the engine. The engine does not sound to be running in 4 cylinders. Have someone experienced simmilar issue? Any clues? In the link below you can see the movie with temperature measuments done with dual beam Fluke infrared gun. https://youtu.be/R26ZmRK099M Thanks, Fred
I tried to take temps off my headers and it always seems the oil cooler side RH was hotter Could be a possible ehaust leak, get a smoke test and find out. Plenty of info on the forum about it.
Maybe the auxiliary air supply to the exhaust at startup is only working on one side The non return valve could be closed What about temperatures when the engine is hot
When hot, after running in idle for 15 min, the temperature evened out. It actually happened in a matter of 2-3 minutes. It just started rising quickly to the same readings as the left side. How does this auiliary air supply works?
Auxiliary air pusses fresh air through a one-way valve and into the header tubes. The fresh air burns residual fuel from the rich start mixture. I suspect one of the one-way valves is not opening.
at start up from pure cold.. there is an air pump that blows air into the rails connected to the headers for the first 2-3mins.. to lean out the rich fuel mixture at start up.. which I think had to be done for emissions reasons.. owners often delete the system all together.. the pump makes a whistling sound for 2-3mins then turns off.. you will not hear it again at future starts, unless the car cooled down significantly.. could make sense if air is getting only to one side making it cooler.. but how quick from start up was your vid.. as I did not hear air pump sound in the vid..
Drock, the video was taken 1-2min after start. I will check if the temperature rises right after the pump stops. Maybe the hot manifold (driver side) has a check valve stuck in close position or system dissabled on that end. This would actually mean the left side is the one running as spec. I guess first I have to hear the pump! I will do it as soon as back to Brazil next month and I will update this forum thread. Note: I found the description on the system, see picture below. The text is a bit contradictory. At the begining it says the system runs with engine at cold start and then later it says extra airfeed is not activated at temperature below 59°F (15°C). Am I missing something here? Earlier vs Later F355s Is this system applicable for the 1995 models? I thought the ealier cars didnd't have as much strict emission controls. Image Unavailable, Please Login
There is no contradiction - air injection is activated if the engine temp. is anywhere between 15C and 63C; if the engine temp. is below 15C, it will not be activated to avoid overheating of the exhaust system. The reason for this, I believe, is because at temps below 15C the mixture will be enriched to such levels which will cause too much "afterburn" with the injected air causing overheating of the exhaust (and you may take-off if running with afterburners!).
Understood! Afterburning was good analogy! Anyone can clarify if this auxiliary airfeed is installed in the early F355s? Mine is 1995, motronic 2.7. I wish I could check physically, but the car 15,000 miles away and I don't have my tele-transport machine on me lol
Maybe, if in fact the engine is running on all 8 cylinders, the inside header insulation on one side is gone since technically the measurement is not being taken from a header pipe....
I wonder if this system, if running longer than it should or otherwise running when it should not be, is a contributing factor to header melting?
Doubtful. The only reports we ever get are of the system not working ("check engine" light illuminated), due to the fuse blown (Ferrari ended up recommending a 5amp higher fuse to stop the fuse blowing). The air pump whistling noise is so loud, that you would know if it was running too long or continuously...it is pretty obnoxious racket...
I agree that it's noticeably loud at start-up and idle but if it continued to run during driving I doubt if you would hear it, particularly in a GTB with the windows up and a non-OEM exhaust or if you're playing music. I've disconnected mine but not due to the sound/noise.
