Cincykemo

Howdy
I just picked up my freshly built engine last week and am having a couple of issues, both heat related, the oil temp being the more concerning of the two.

I'm seeing oil temps (taken at the filter) climb to 240 with just light highway driving. The water temp hovers anywhere between 200 and 210 but the oil temp just keeps climbing when cruising at anything above 15% throttle. Other than this the car appears to be running well, no smoke, no cold start piston slap, it was dyno tuned and made what it should.

Setup:
BP05 head/ BP4W block (both faced .006 in)
83.5 mm 8.8:1 Supertech Pistons
Manley Rods
Weisco XX Rings
Standard Size Race Bearings Clevite/ACL
Boundary Pump With 1 Shim (+5psi from stock)
ATI Damper
640 CC Flowforce Injcrs
M Tuned Reroute
195 degree T Stat
MS2
93 octane
Hood vents
After market rad with mishimoto fans
MP62 Hotside kit Intercooled making 13.5 lbs


Clearances:
PWC: .035


I just don't think the oil temp should be getting this high. I hate to think where it might go if I drive the car how'd I'd like. The shop that built it is using Cenpeco Super Racing (high zinc) 10w-30 in it. It never ran this hot before the build, granted I was using a different oil and the clearances were different. I could always add an oil cooler but I feel like that would be a band aid.

Second problem I'm having is when the car first heats up the temp (from my Mega Squirt 2) will keep going right up to 225-235 and then shoots back down and stays around 200-210. It's bizarre, even the stock water temp guage goes hot and then back to the middle.

I haven't been able to do to much investigating on either of these matters. Hoping someone might have some insight or suggestions. Maybe I'm making to much of a deal of the oil temp, idk,


Build Thread: *** Or Kitties? (an mp62 build thread) - Miata Turbo Forum - Boost cars, acquire cats.

LeoNA

The standard oil temp posistion is the pan. 240F at the filter might be 20+ deg higher than the pan reading. Also the temp gauge might be reading on the high side.

curly

iTrader: (25)

I'd like to know what your water temp calibrations are, and what your oil temp setup is.

Your readings of the water temp sound spot on for an M-tuned reroute. It'll spike high until it heat soaks the ~6" of water between the head and the thermostat, then dump cool water through the radiator, cycle repeats, causing oscillation until an incredibly long drive later, you stabilize at thermostat temp. Worst oscillation of any reroute I've seen, I'd recommend changing it asap.

Dunno if that's an original color, is that a 90-93?

Cincykemo

Curly
My oil temp setup is a Glowshift sandwich plate, Innovative guage, with the temp and pressure sunsor the guage came with.

How would I calibrate my water temp?

What is it you're suggesting I change? The t stat is a new 195 degree unit. I do have a spare 185 kicking around I can switch out. It never did this "spike" thing before when it had the original 185 tstat the car came with but I was having heating issues last summer after switching from an m45 to mp62 unit. I did notice the shop that put the car back together routed the reroute where the hose is angled up towards the back of the engine maybe causing this issue.

It's a 95 in Montego Blue, original paint.

hornetball

iTrader: (4)

On the reroute, what is happening is that you have a large volume of stagnant, cold coolant that is preventing the T-stat from opening. In general, the closer you can get the T-stat to the head, the better off you'll be. Drilling a small bleed hole in the thermostat might help.

Your oil temp is concerning. With street driving, it should track your coolant temp -- even if you monitor at the oil filter. Oil temperature is driven by rod and main bearing friction, which is why an oil cooler is needed for high-rpm track operation. If that friction is high with street driving, then bearing clearances are suspect. Is it getting any better as you break-in?

Something else I've seen that can drive oil temperature is piston ring problems. In this case, a secondary indication is oil that gets dirty quickly or other indications of blowby. Basically, hot combustion gasses getting into the crankcase.

LeoNA

The hottest components in the engine are the valve springs, turbo and oil pump. The oil pump pulls oil from the pan and pumps it through the oil filter. It will be hotter then the pan oil temp. The oil temp recommendations are referencing the oil in the pan. 240-260 at the filter is not unreasonable. 10-30 oil is not ideal. You should switch to a 40 or 50 weight, (0-40, 5-40,10-40, 5-50, 15-50). I would use a name brand readily available product. A very good oil that still has a fair amount phosphorus (zddp) is the Mobil 1 15-50. My preference is the redline 5-40 or 5-50.

I would replace the t-stat with a 180f. It will not reduce the peek operating temp, but will allow you to have more headroom. You will not be able to run a temp lower then the opening temp of the t-stat. Most 195 t-stat’s open at 195 and are fully open at 200. The 180 should be fully open before 190, which will allow you to have a 190-195 nominal operating temp. The t-stats in the re-route’s are relatively small, so having it fully open at a reasonable temp is important. Also there is a chance that the current t-stat is sticking, it is common.

Fan strategy is important. I recommend having the fan turn on a bit early to prevent run away temps under heavy demand situations. A 193-195f on temp will allow the fans to turn off at cruise where the ambient temp is moderate and still try to keep the temps under 200. The common coolant cocktail is 1 bottle of Redline Water Wetter with a small amount of coolant, maybe quart and distilled water.

.0035 PWC is not enough. Make sure you let the engine warm up well before driving. Especially on a new engine. 180f on the water and 100f+ on the oil.

I would also double check the calibration, resistance spec’s for the temp sensor’s.

engineered2win

I think the oil temps (~115C) are in line with expectations:

• I'd definitely move the temp measurement to the pan. That's an industry standard location and gives you a far better indication of what the bulk of the oil is doing. I really don't know what increase to expect from measuring at the oil filter, but the oil pump is applying work to the oil, so it's guaranteed to be higher than the pan temp.
• Even without the OE coolant/oil warmer, the oil is pretty closely linked to coolant temp. If you're running >95C coolant temp on the highway, then basically your oil temp won't be lower than that. I expect ~100C oil temp during highway cruise as normal (~25C ambient) and it will offset with ambient temps also. Get your coolant temps in check and oil temps will drop probably 5-10C.
• The biggest contributor to oil temp is going to be engine speed. This is why even stock N/A miatas can get screaming hot engine oil (and trans/diff) temps on track. Depending on what gearing you have, you're running 3500-4000rpm at 75mph on the highway.
• New oil will be more viscous, meaning higher pressure and temp for a short period of time. It's common to run a 1 hour break in at like 5000rpm to accelerate this process in the OEM world before starting any critical testing (friction, BSFC, WOT output, etc.).

hornetball

iTrader: (4)

Drove the '90 turbo today just to get some run time on it (no longer my daily). It was about 100F outside. Water temp settled at ~195F. Oil temp (measured at the sandwich plate -- no oil cooler) settled at ~210F. I was using AC. That's pretty much the norm for this car in highway cruising.

Just a data point.

technicalninja

That sounds exactly right to me as well. This is a good data point.
Why did this get a neg cat?
Took care of it...
Rick

sixshooter

iTrader: (12)

Switching to a thicker oil can cause higher oil temps. But it may offer better viscosity.

LeoNA

In general, that is true. The oil temp at 240F is less of a concern then the minimal piston to wall clearance and that is why I recommended the higher viscosity oil. The higher film strength will help prevent it from sticking a piston.