[spuggy]

Originally Posted by chrisbalich

I do have a Clewett cam sensor at the back of cyl 3. I won't pay for that slick CHT adapter plate, but I may yet make one whenever the engine next comes out. I reckon it'd be really easy to make.

I think it'd certainly be easier to make/fit one with the motor out, LOL...

Originally Posted by chrisbalich

I have warmup finishing in that 50-60C range as well. But when it's 38*F ambient, it takes a while for the engine to get to 60C.

Yes, a little while.

I've got several trial cold starts inter-mixed in the most recent log I pulled up to look at; but starting from a ~10C ambient and IAT, ECU, CHT and oil temp within 3 degrees of each other:

CHT hits 20C within ~30 seconds of starting, (chaincase) oil temp has come up 2 degrees.

30C on CHT, chaincase temp has come up 0.5C.

40C on CHT, chaincase reads 12C

50C on CHT, chaincase reads 13.7C

60C on CHT, chaincase reads 15.8C

Each 10C rise in CHT temp is roughly 1 minute apart (darn the Motec I2C log reader, which makes this hard to figure - there's gotta be a trick for that).

70C on CHT, chaincase reads 16.6C

Some 6-7 minutes elapsed; heater in lambda sensor reached temperature, and providing readings.

80C on CHT, chaincase reads 18.7C

90C on CHT, chaincase reads 25.8C. Which could actually be ambient inside the engine bay, as the Motec reports 22.3C. IAT (intercooler outlet) reads 12.6C

Head temps over 90C depend on load - just cruising around with light throttle won't increase them. I don't see much more than 100C or so when the car is moving.

10 minutes elapsed; chaincase reads 40C

17 minutes elapsed; chaincase reads 50C

20 minutes elapsed; chaincase reads 60C

Stop for gas; on re-start, chaincase sensor has heat soaked to 78.9C (highest reading) and IAT picks up another 5C (to 20C).

One issue I see with using chaincase sensor for warmup compensation; I logged 60C CHT when the chaincase was reading 16C/60F - you could have ambient exceeding that in summer.

Originally Posted by chrisbalich

And with no proper heat, I have a tendency to let the car idle for long periods of time. So it needs to read [reasonably] accurately under all conditions.

Pretty sure it does. I never leave any motor I care about - especially an air-cooled one - just idling for long - especially from cold - but that's just me.

I think few appreciate just how hot the heads get with inadequate airflow when idling - when messing with idle trim, injector timing etc, I saw 250C on the CHT after 10-15 minutes or so. Now I set a temp alarm of 180C on the Motec dash. Which, for perspective, is almost twice as hot as the car runs under boost.

Which most likely doesn't actually hurt them; it's been SOP at most shops to leave them idling to get the oil hot for changes for many, many, years, right?