Miata Turbo Forum - Boost cars, acquire cats.

Quote:

Originally Posted by Track (Post 1081406)

So I am curious on theories for engine wear vs oil temp vs coolant temp.

Currently I am running a no T-stat reroute and an oil cooler on the car. Generally speaking on track my oil temps will get up to 190-ish, while coolant temperatures will run between 120-180 depending on the track and speed.

should I be worried about engine wear if my coolant temps are running low, even though oil temps are normal? I am assuming oil temp is a pretty good indicator of bearing temps, and coolant is probably more accurate for piston/cylinder walls, etc.

what do you guys think?

I think your engine is over cooled.

Totally in agreement with the use of a coolant thermostat to get the engine up to a proper temp. The comments and graphs verify what I've known intuitively and read elsewhere.

However, everyone seems to talk about optimal coolant temp, not including the oil. Tere is a "lead/lag" relationship of water/oil temps. By this I mean proper guages will show a coolant temp rise before oil temps go up. Once the engine is fully up to running temperatures, the oil temps will be higher than the water. Pushed hard, ie, on the track, oil temps in a non oil cooler equipped Miata will spike quickly ahead of the water temp rising. Temps we saw on our Spec Miata were ~280F momentarily which is the actual limit of the guage scale (Mechanical 270 degree sweep AutoMeter). Water temps at this time were 220F. Ambient Air temp was close to 100F. I think these elevated oil temps are from the oil squirter system all 1.6 & 1.8 Miata engines come with.

It seems your oil cooler equipped system is doing a bang up job of keeping things cool. I suggest maybe a bit too cool.

Running ITA and FP now, we have the ability to run an oil cooler. We also have an oil thermostat in the system - ours is a MOCAL. With an oil cooler we've now got water temps at the 190-200 range and oil runs from 220 - 230. On a race car the oil thermostat isn't totally necessary - on cold days you can cover the cooler. I like the flexibility to keep the oil temp where it needs to be.

Also I am not sure why you think an engine pull is required to change the coolant thermostat if you have a coolant reroute. Or why SixPack has to drop his PPF to do the same. We use a 1.6 thermostat housing on the head with the fan switch bung cut off. This gives is plenty of room between the thermostat housing on the back of the head and the firewall. On the 1.8 car pulling the coil pack off (if you don't have COP) is needed and pulling the CAS or the coil pack from a 1.6 makes lots of room. I really don't understand why Mazda didn't keep the T'stat back there to begin with.