Too hot?

I went to our local track today and watched some vintage racing. On the way home, while driving on the freeway (75 mph), the oil temperature started to creep up. It ended up around the 195/200 degree mark (outside temperature was 85 degrees F.

Strangely, my CHT gauge never went over 225 degrees F., but the engine compartment was hot and the fuel injection started to act up (slight hesitation and stumble at cruising speed)

When I got home I left the car running and grabbed my temperature gun. The heads showed 201 degrees F and the oil temperature sender unit on the back of the block showed 197 degrees F.

My questions are:
1. Is 195/200 degrees F about right for the conditions I mentioned above?. My car revs at 3700/3800 at 75 mph, so the rpm is quite high.

2. Is there something wrong with my CHT gauge? It's a Westach gauge, which is considered an accurate, dependable gauge. I ask this because 225 degrees F seems low.

3. How hot is your engine bay after a run on the freeway, on a hot day? Can you rest your hand on anything in the engine compartment?

I'm starting to wonder if I went with too hot (performance wise) of an engine (2275cc, 9.0 to 1 compression), considering I use my IM mainly for highway cruising. Having said that, I do like the power.
Thanks
Ron

My opinions:

1) 195/200 is fantastic. I'd be very happy. 240 is getting to be critical.

2) It's hard to know about the calibration of the gauge, but I indicate about 275 deg on a 75 deg day. You can check your calibration by dropping the sensor in a pot of boiling water-- it should read 212 deg. 300 or so is considered "normal", 400-425 deg is critical.

3) I don't want to touch anything on the engine after a long run on a hot day. I grab the dipstick with a rag. 200 deg is hot. Everything gets heat-soaked.

If you are not knocking, then you are pretty close to perfect on temps. I'd be happy with the power of what you have.

Your temps are fine, Ron. The people who are happy that their engines are only running at 165 are woefully misguided. It is actually NOT good to run excessively cool.

The temps you are running will burn the moisture out of your oil and demonstrate that your cooling system is adequate for the amount of heat the engine creates (through displacement, compression, friction, etc). Don't even worry about 210 for the coolant (oil). Start paying attention as you approach 220.

Temps are healthy - you're doing GREAT!

angela

Sounds to me like I should get serious about getting some more gauges in my car soon. I've already noticed my temp gauge creeping up slightly (but returning) a couple of times.

Rich---I have the Westech gauges too. CHT and oil temp and the CHT saved my engine one time.

Rich (and others who might worry about this).......

Aircooled engines do not behave like their water cooled counterparts. Water cooling is quite a bit more efficient than air cooling and the modulation you get from the water thermostat tends to keep the engine temp closer to whatever is "normal" for that engine than the thermostatically controlled air vanes in a VW fan shroud. In other words, it takes longer to modulate the swings in temp that the engine sees.

It is perfectly normal for your temp gauge needle to move around a bit as you drive it, especially if the gauge is sensitive (as a lot of VDOs are). As an example, my gauge is about 175 on the left margin, and 230 on the right margin. Right in the middle is about 205. Of course, your gauge may be entirely different, as I've adjusted the range on mine with an external resistor.

Anyway, if you drive up a long hill, the temp might climb just a bit.

Drive down the other side and it might drop just a bit.

The best way I've found to "calibrate" your gauge (which usually doesn't have any numbers on it so you're kind-of 'winging it') is with a Mainely Custom By Design dip-stick thermometer. Use the dip stick to see what your oil temp is and note where the needle is on the gauge. Do this for a few different temps on the 'stick to get an idea what your gauge is doing. When Chris borrowed Pearl for his wedding get-away car, I didn't know who would be driving it, so I put a piece of red marker tape on the gauge face at about 215-ish to tell them if it got there, then stop, just as a precaution (it didn't).

If it goes up towards 220+ and stays there, then I might get concerned, but other than that, just drive it.

My oil temperature gauge seems to be fairly accurate. The needle was around the 190/195 degree mark and I ran around and took a reading at the oil temperature sending unit with my temperature gun. The gun read 197 degrees.
What I can't figure out is why my heads are running so cool. Doing a temperature test on the CHT gauge will be difficult, since the gauge has special wiring.
My fuel injection definitely works better on hot days when I have the engine lid propped up 4 inches. Getting more ambient air into the throttle bodies can't hurt either.

Where do your thermocouple wires terminate, both the hot side and cold side? Hot side would typically be the ring terminal, cold side is wherever the thermocouple wires connect to any other wire or terminal that is not made of the thermocouple alloy. If the cold side is at the back of the gauge, you should be fine. The Westach gauge is calibrated for 70* ambient but only if the thermocouple terminates at the back of the gauge. If it's in the engine bay, you'll be reading low because the ambient temperature will be higher than at the gauge.

I'm not sure how to answer this, so I'll give you a photo instead.

Ok, assuming the ring terminal is under your spark plug, where's the other end of the wires? Does it go in one continuous run to the switch or gauge (assuming both in the dash)? Or is it spliced into standard wires that run to the switch/gauge, and if so where in the car is the splice?

And you don't need to completely remove the gauge or sender to test it. Just dip the ring terminal into a cup of boiling water. It'll cool down on the way out to the car, so if you've got a candy thermometer, use it so you know what the actual temperature of the water is. If you don't have one, a bigger pot of water will hold the heat longer.

Justin, 01226 attaches to 01266, which attaches to the gauge (01235).
I've considered using a boiling pot of water-dipping in the CHT sensor ring and my Mainely dipstick, for a comparison.