Too Hot......or Not Too Hot?

schubee · schubee's Garage

As some of you know, So Cal has been pretty warm in the last week. We’re experiencing around 85 - 100 degree weather. My question is, what’s hot and too hot? I upgraded my temp gauge to numerical and in stop and go traffic, my temp would max out at 210. I just had my CO adjusted at ANDIAL and it passed smog with flying colors. Do you guys think I’m running too lean and should I richen my CO to drop my temps? Or is 210 in stop and go traffic okay for a short trip. The distance traveled with this temp is approximately 20 miles. Thanks in advance for your comments.

makaio · 07-10-2002, 12:30 PM

John,

Glad to see you're still with us. I haven't heard from you in a while.

First, 210 in stop and go traffic is no big deal. My car has been running 200 or so down the freeway, in 100-105 degree heat.

What weight of oil are you running? This time of year in california, you should be using a 20-50 dino oil. I don't know what weight in synthetic.

Second, it's about 108 here in Red Bluff right now, and it's expected to reach 115-117, this afternoon. It was only 113 yesterday!

Cheers

rickeolis · 07-10-2002, 12:31 PM

210 for stop and go on a really hot day is just fine. I have been getting 240+ on our hot days, and my friend had to install an oil cooler on his to deal with it. I am going to have to get a cooler too, but have many other issues to deal with first. (Rusty panels, etc.)
You really don't want to go past 250 if you can avoid it. That is the rule found on this BBS and in aftermarket manuals I have read.

88911coupe · 07-10-2002, 12:36 PM

Maybe dumb question...why does richer = cooler? Is it b/c more fuel in the intake cools off the heads or something? Just thought I'd ask.
Thanks,

Doug E · 07-10-2002, 05:13 PM

Buck - good question which I've wondered about myself. Just a guess, but I believe the mixture affects the firing of the engine and if the firing is reduced then there is less heat.

Hopefully one of the experts will definatively answer the question.

marcesq · marcesq's Garage

A leaner mixture burns hotter than a rich mixture, hence the higher temp.

MarkY · MarkY's Garage

You think Southern Cal is hot, try Phoenix. A lot of people talk about storing their P-cars in winter, here in Phoenix my car doesn't see daylight in the summer.

GB83SC · 07-10-2002, 05:43 PM

You think is hot out west try south Florida with 100% humidity
plus its been raining non stop for the last 45 days.

I cant wait for the first cool front to hit but that is late Oct.
Stay cool boys.

Sunroof · 07-10-2002, 06:29 PM

Least we forget HOTLANTA! Like Florida minus the gulf breezes.
I hover around 200 - 220 on hot days but I am using the Cooler Collar and Heat Sheets to help it out a bit.

Looking forward to fall.

Regards
Bob
73.5T

mark 74 carrera · mark 74 carrera's Garage

From what I've read (and having a 2.7 you read about heat!) Bruce Anderson gives ranges from the Technical notes II (5/2001) in Excellence ... 180 - 200 = Normal opersting temp, 230 is warm, 240 is hot, 250 is too damn hot.

From Bruce Anderson's perspective I'd say you OK.

911pcars · 07-11-2002, 12:48 AM

A rich mixture burns relatively faster than a lean mixture. A slower burning lean mixture means more of the cylinder is exposed to the combustion process as the piston goes downward on the power stroke. However, an overly rich mixture also provides a cooling effect to the combustion process since not all the fuel is burned. \\

Sherwood Lee
http://members.rennlist.org/911pcars

Bo · Bo's Garage

Excellent thread - I recently installed an 82 Row SC engine in my 72, and I use only the oil cooler in the engine right now.

I was a bit concerned about this fact to start with, but the highest temperature I've seen so far is around C95 (that is F203 for you guys), which leads me to believe I can get away with the engine swap without adding an external cooler - IF I stay aways from the track, that is..

stlrj · 06:03 AM

If we use stoichiometric mixture settings as our point of reference as in closed loop 02 sensor operation range then running leaner burns cooler as does running richer.

Peak mixture settings, or stoch, occur typically at a 15:1 air/fuel ratio for most gasolines, including avgas. At 14:1 in this example, with 14 parts air and 1 part fuel, the mixture is rich, and burns cooler than stoch. At 16:1, the mixture is lean, and burns cooler than stoch.

http://www.ipilot.com/forum/message.asp?PID=9101

recent tests on Lycoming engines by ASTM revealed this fascinating result: detonation is most likely to occur at a mixture setting 11% richer than stoichiometric (i.e., substantially richer than peak EGT).

http://www.avweb.com/articles/englies.html

under the operating conditions used by Texaco, an equivalence ratio of 1.11 gave maximal knock. (Equivalence ratio is just a normalized, dimensionless way of talking about fuel-air ratio, such that an E.R.. of 1.0 corresponds to stoichiometry, 1.1 is 10% richer than stoichiometric, 0.9 is 10% leaner, etc.

http://www.texasskyways.com/avfuel.htm

Peak EGT will be seen when the engine is burning a perfect stoichiometric Air to Fuel ratio. This occurs at about 14.7:1 on gasoline engines. Best engine performance at WOT is typically seen at A/F ratios between 11.5 and 13. Exhaust gas temperature will be considerably cooler at these mixtures. Retarding timing without making other changes will raise EGT. If AF ratios of greater than 15:1 are reached EGT will begin to drop. So it is VERY important to know which side of peak EGT you are on.

http://www.denverspeed.com/EGT.html

The next question we might ask ourselves is how all this relates to cylinder head temperatures (CHT) and engine oil temperatures?

Cheers,

Joe Garcia
Redwood PCA since 1976
86 Carrera
92 Grand Caravan
86 Olds 98