problem with car when it got hot on my CIS to EFI conversion

bb · 07-11-2005, 08:36 PM

I had a problem today. I finally got the car running today, and it ran awesome. The throttle response and the power with Tony's kit is impressive. Now for the problem, when I finished my runs and was letting the car Idle when the idle started to go up and down running real lean and could barely keep it running. The fuel pressure was good. The car seemed to be running hot 220 degrees f. Is this high? Now when the car cooled down it did seem to run good again.

76' 2.7 turbo

Any ideas?

Thanks
Oscar

cmonref · 07-12-2005, 03:59 AM

You need to register and post your query on the Megasquirt forums. Go to www.msefi.com

Those are the folk with the answers you seek.

bb · 07-12-2005, 04:13 AM

I will in that forum as well. I was just wondering about how hot the car was running and if this is too high?, and or any suggestions.

cmonref · 07-12-2005, 05:40 AM

Does the 220 deg F represent a change from pre-EFI? If yes, that is of concern. Your post says you were running lean, and that could cause higher temps. And probably some anomaly in a setting of the EFI.

You'll get a pile of answers as to what is HOT in a 911. I've always thought 220 was the upper edge of the "normal" band. My '80 SC has not seen 220, even with the AC running on a hot day. The engine is stock with the 28-tube brass cooler.

Your temps "post-EFI" should be the same as before you made the conversion. Changes would be in the EFI and its tuning.

tbitz · 07-12-2005, 06:11 AM

Oscar,

The VE table just needs to be tuned. I assume your are using the default RPM columns I sent. Here is what is happening.

As the rpm goes up, you get MORE vacuum (yes more, because your throttle is still closed during idle). As you get more vacuum in your 950 rpm column your probably giving less fuel which causes the engine to lean out and falls back to your 750rpm and the ECU richens the mixture which starts the whole process over again.

You need to play with the vertical column (vacuum column) to get rid of the hunting. Creating two rich points on either side of the target rpm to keep the engine locked at that rpm.

Changes with the laptop are easy so play around with it.

The most likely reason temperature is playing a roll, is because with a cold engine, the ECU is in "Cold Enrichement" mode where extra fuel is being dumped which keeps the engine out of the lean condition.

Cheers,