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RoninLB RoninLB is offline
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Join Date: May 2001
Location: Peoples Republic of Long Beach, NY
Posts: 21,143
Originally posted by dvkk

If your carburated engine makes more power when it is cold out, that proves your mixture is waaaay too rich when it is warm.
Since your engine does make more hp when it is cold out, that proves you are dumping in the necessary extra fuel at all time.
------- Sounds good but that hasn't been my experience
My EGT's are about 25degF hotter at 70degF than at 40degF. If I lean out 70degF operation EGT's will become hotter and will have greater deviation between hotter and colder EGT.. in other words the spread of piston power will become greater. It's as lean as I could make it and be easily streetable for my act.

Since the fuel has considerable mass, what it does is put out the fire, absorbing the heat of combustion, reducing hp. By leaning out the jets, you will regain some of the lost hp you notice when it is warm out.
---------- it does put out the fire but it still feels stronger at night. I have hard numbers on that.

A few of you made the same observations with your FI cars. Those of you that are smart enough to have your O2 sensors hooked up are having your A/F ratio properly adjusted to compensate for the colder air.
-------- FI is another story somewhat because FI doesn't have the atomization critical issue that carbs have. A cool carb and intake allows the mix to be dense as possible.

I don't really have a text answer on what's happening but i think I could get away with 1/4 idle mix leaner at night and make even more power. That 1/4 turn is worth about the 25degF in EGT. Then I'd have to reset for daytime hotter ambiant. I'm figuring the above on 30-40degF ambiant difference.
Ronin LB
'77 911s 2.7
PMO E 8.5
SSI Monty
w x6
Old 10-11-2005, 08:40 PM
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