<VV> Engine Bay Air temperature experiment

kevin nash wrokit at hotmail.com
Sun May 24 15:04:00 EDT 2015

Joel- Yes, my symptoms were (I got that problem over and done with) exactly like what you've been seeing, and it was hot
soak. The solution in my case was to richen the engine temp fuel values. What happens is, with the engine warm and shut off,
the engine bay temps go way up. The manifold air temps also go way up, and then the computer thinks it needs to lean
the fuel in response to the lower air density caused by the high air temps, leaning the fuel mixture beyond all reason, making
the situation even worse. To give you an idea as to how hot the engine bay temps can get after only ten miles of driving, and then 
park the car for 15 minutes or so, like I did yesterday- ambient air was 72 degrees, and I parked  the car. After sitting for 10 or fifteen minutes, the engine bay  temperature sensor was maxed out- reading HHH, so I know it was higher than the 125F temperature limit for that thermometer, and the engine temp sensor, located at the end of the right side head (uses the bolt hole where the original ignition coil used to be) was reading 167F (this sensor normally reads around 140 during normal cruise when the engine is warm). The manifold air temp sensor was reading something like 125, but cant remember for sure- in a normal
steady cruise, it usually reads around 100 to 110 no matter what "ambient is". I know it is tempting to think that there might
be a problem with my sensor, but there isn't!- it is well calibrated, and reads quite a bit higher than ambient only because of 
its location down close to the head in the left side of the cross over manifold.
Please note- I've been doing all of my tuning open loop, mostly because it is much more fun, and also so I don't have to depend
on the O2 sensor working properly for the engine to run right, so your solution may vary!!
Kevin Nash
63 Turbo EFI daily driver
> Message: 3
> Date: Sat, 23 May 2015 21:58:50 +0000
> From: Joel McGregor <joel at joelsplace.com>
> To: "virtualvairs at corvair.org" <virtualvairs at corvair.org>
> Subject: Re: <VV> Engine Bay Air temperature experiment
> Message-ID:
> 	<27D1EC0369826D478297DD86D9DE5E2C848DCA3D at 2012SBS.joelsplace.local>
> Content-Type: text/plain; charset="us-ascii"
> Good info but it's about what I would have assumed.  I have always been under the impression that heat in the engine compartment while running was only a problem with turbos on boost for an extended time.  Otherwise you have so much fresh air from the fan that it's pretty much ambient.
> My '65 (non turbo) with a Megasquirt system has what appears to be a hot soak problem.  It runs ok from a cold start and runs fine hot.  If I shut it off hot and try to restart after 15 minutes it either won't start at all or barely runs for about 5 minutes until (I'm assuming) everything cools back down.  It seems like it's running super rich but it doesn't blow any black smoke.  I can manually run the fuel pump for a while before I start it with no change in behavior.  It broke a cam gear and I had to move and don't have my shop setup yet so I can't work on it but I'm wondering if your symptoms are anything like mine.
> Joel McGregor


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