buckethead1

I was playing around with the various gauges on my car(cylinder head temperature,vacuum etc..) and I realized that I have no idea what the normal operating range is. I realize that on the oil temperature gauge the red zone isn't good. But what about the others? What is too hot for the heads? What is the indication that the air/fuel ratio is off?
Is there a chart somewhere with these ranges?

buckethead1

So are these gauges just a gimmick?

SpectreH

I don't think they are gimmicks, but I'm with you, I'd like to know the normal operating range. Especially cylinder head temp.

Roadk9

This is interesting, the more I read on these forums the more folks I find with no or little experience with the manual side of cars. By Manual I mean experience building or making major repairs and having to take measurements to gauge the quality, or effectiveness of the work by understanding what is actually happening in the engine or trans or the suspension for that matter. The other day I saw a post on a radiator thread that brought this out full force. The thread was a MFG rep keeping us up to date on the development of a larger capacity radiator. A forum member asked if the radiator would cause the engine to run too cool!!!

Okay no disrespect meant to either of the above posters but as for the heat in the engine, it is related to the radiator and the cooling system. The engine has water jackets that the water pump pushes the antifreeze mixture thru. It also flows thru the passages in the heads.
Modern engines still use a very old system to regulate how hot the engine is allowed to get before the cooling system starts working. The Thermostat is rated to open at a particular temperature that the engine is designed to work best at. When it opens cooling starts.

Now knowing that you can answer your own question about the cylinder head temp, and the oil temp. Your stock thermostat opens at a little more than 210 degrees. That means the designers wanted the antifreeze flow to keep the engine around that temperature. If you are seeing a cylinder head temp significantly higher than 220 degrees then obviously something is not right. But when you start the car if you just sit still (Don't drive)and watch the temp gauge you will see it rise up past that 220 degree mark and then come down. It comes down when the thermostat opens and allows the cooler water to move the heat to the radiator.

It is possible to over cool an engine but typically it only happens in really cold weather with a thermostat that is stuck open.

As for the Air Fuel gauge all gasoline engines are stoichiometric and the perfect reading would be 14:1 (14 parts air to 1 part gasoline)(Wikipedia says 15). A gas engine needs to stay close to that to run healthy. If you suddenly see it drop 10, 08 (stomping the gas pedal)it will quickly come back up if the Fuel injection system is working right. Likewise when you get off the gas you'll see it rise. Closed throttle coasting pegs the gauge. The gauge helps determine if the engine is running rich or lean. Higher than 14 is lean, lower is rich.

Hope that helps.

SpectreH

No offense taken, but I do understand the basics on the cooling systems for both water and air cooled engines. The original poster's question on the center gauges is still valid.
It is my understanding that the real gauge to the left of the fuel gauge is water temp, but the digital gauge in the center that you can bring up is an actual cylinder head temp gauge. Cylinder head temps will run higher than the coolant temperature. Unlike the digital engine oil and trans oil temp gauges, the cylinder head temp gauge lacks a normal range indication.

buckethead1

What he said^^^!

I understand the mechanics of the system. What I don't understand is why would gauge readings of different engine functions not have a reference to normal operating perameters.

Roadk9

Oh, I get it now..

Please post a pic of the cylinder head temp gauge reading above 220 degrees when you see it.

BaknBlk

If you are lucky enough to live in the "dry heat" of Arizona, you will regularly see cylinder head temps in excess of 220 degrees...my extreme was 246 degrees with a inlet air temp of 158 degrees....and yes, the cooling system was working just fine....just not much cool air to work with as the temperature that day was at 115 if I remember right. I took a picture of the readout and still have it, but for some reason can't post it. Living with a "dry heat" is so much fun !!!

SpectreH

I saw head temps that high when stuck in traffic due to a terrible accident on I-95 outside of Daytona Beach, FL a few weeks ago. The air inlet was in the 120 range at that time. Gently holding the engine just under 2000 rpms would bring it down some due to more coolant flow.