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MikeJinCO · Posted: Wed Aug 25, 2021 6:45 am Post subject: Oil Temp Problem

In the track car the motor oil has been running 220F for the last two years. Last time out it pegged at over 250F. I have changed the oil and dismantled and cleaned out the entire system and cut the oil filter open and inspected it. No sign of a problem, now runs fine with 6 bar at idle. They only change I made to the car was that I changed our the 4 speed for a 5 speed. It was running strong and I could really tell the difference of the 4.11 vs 3.88 axle('78 US).

But, I am wondering if the tranny could be just dragging enough to over heat the motor oil?. Before I put it in it was turning quite freely, as easily as the 4 speed, and I also drained it and then put in some diesel, turned the input shaft about 200 turns and rolled the transmission around to try to clean it out. Then I put in to Redline MTL before running it. I made an illegal test cruise around the neighborhood for about 3-4 miles before taking it to the track. Ideas?
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Mike

'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

Cedric · Joined: 27 Aug 2004 Posts: 2810 Location: Sweden

D Hook · Joined: 02 Nov 2002 Posts: 3158 Location: Omaha, NE

6 bar at idle is 87 psi. That seems a bit high.
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'80 924 n/a SOLD

924RACR · Posted: Wed Aug 25, 2021 9:38 pm Post subject:

Yeah, shorter gears will make more heat.

I'm guessing that 6 bar is cold idle, not warm idle...

250 isn't too bad if you're running synthetic; not ideal but still entirely workable if dino oil. 220 is actually at the bottom range for optimal power...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

MikeJinCO · Posted: Wed Aug 25, 2021 10:49 pm Post subject:

Thanks for the input, it starts me thinking about this in different ways. I originally had an oil thermostat, but removed it a few years ago as when I looked at how it worked the one I had really restricted the flow. Another example that if you try to do it the cheap way($75 vs $200 for a good one) you end up paying for it twice. That and a larger cooler(8x10 I think) reduced the temp from 250+ to 220. I have 6 bar at cold start up and idle with oil temps in the 100-150 range. It typically runs at the 6 range. I increase the idle to 1200-400 when home to keep it running as the 45 Webers are not real happy idlers.

I have run Driven semi-synthetic this year. Yes the rpm picked up probably 400 to 600 everywhere, I was accelerating well when before sort of stumbling along at times, lots of difference from about 3600 to 4200 on my quite mild cam. I don't have a tire(Nitto) temp gauge, but I noticed they had picked up much more garbage so had to be quite a bit hotter. It was also 95 degrees out there. So a lot more heat in general

Another factor could be lack of cooling, I run at 5000+ ft so the cooling is dropping about 15 to 20 percent due to air density. I could use a 931 front metal to get the air vents to cooler and 951t radiator.

I've decided to put the car up on blocks, then run it in 2nd gear. Then I'll check the tranny temp with my infrared thermometer, if no problem it shouldn't heat up much just free wheeling.

The motor man and I are going to recheck and possibly reset the timing a bit as his circle track folks have significant oil heat problems with too much distributor advance.
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Mike

'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

Cedric · Joined: 27 Aug 2004 Posts: 2810 Location: Sweden

Altitude definitely affects the cooling, i worked with high altitude calibration at my previous work position and its something you can clearly see in the data.

I think before you conclude that something have changed you should run at a track where you have been before in conditions you have run before. 120degC is where a stock 924 and 931 seems to hoover around on track, at least over here.
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1980 924 Turbo
www.instagram.com/garagecedric/

MikeJinCO · Posted: Wed Sep 15, 2021 11:23 pm Post subject:

Update. Ran it on blocks for 15 minutes and transmission not a problem. Then took it out to track last week. Temperature only 80F(morning) oil temperature never got over 210F, water at 180F. Next race weekend is Sep 25/26 temperatures will probably be 85+.
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Mike

'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

924RACR · Posted: Thu Sep 16, 2021 3:33 am Post subject:

Sounds promising!
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

MikeJinCO · Posted: Thu Sep 16, 2021 10:23 pm Post subject:

I measure the temperature coming off the motor where I should measure it in the sump or returning to the sump. I drilled and tapped the drain plug but did not want to be disconnecting it all the time to change oil as it would just promote future problems. I found a good inline sensor tap but that requires enough AN plumbing changes that I wont start that trial of a project during the season. If I can get my new motor ready for next year I'll need to upgrade the cooler again from the supposedly 20,000 BTU as the oil supposedly supplies about 40% of the motor cooling.
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Mike

'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

What instrument are you using to measure temps? Are you logging it or eye-balling it? Voltage variations and bad ground can wreak havoc on instruments...
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erstwhile owner of just about every 924 variant ever made

924RACR · Posted: Thu Sep 16, 2021 11:56 pm Post subject:

What matters most is to understand the long-term behaviour, less so one specific location vs another.

On my P2, I measure it in the tank and also coming out of the motor... but that's a different story, as the exit from the motor is on the scavenge side (dry sump), before the cooler.

On the 924, since the plumbing is different and wet sump, I measure it at the oil filter, heading to the cooler, because that was accessible. I simply drilled and threaded an already-existing boss on the oil filter remote mount, and put the sensor in there. So in my case at least the oil going into the motor wil be cooler than what I'm measuring. And since the pump is drawing from the sump, while the sump could be a little hotter it won't be much different.

In this case, I'm getting the measurement of worst-case, so I can see if the oil is at risk of breaking down.

Seems similar to your setup... and you won't be able to measure it returning to the sump, because that's the internal draining down the inside of the block.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

MikeJinCO · Posted: Wed Sep 22, 2021 10:10 am Post subject:

I have an Autometer electric temperature gauge, new one up to 300F, currently measure on the way to the oil filter which is located where the passenger side headlight used to be, so measuring the worst case also. I had an oil thermostat coming off the filter as that' s where the hoses come in and out from in front of the radiator. I pulled the thermostat and put some copper piping in its place, sort of crude, but cheap and easy. I was thinking of putting the thermostat fitting there, but it might be better piped solid to to the filter as getting a ground for an electric gauge is pretty ugly with the tubing.

I took the car to the track last week and at cooler temps of about 80 in the morning the temp never went over 210 with water at 180. So at this point just one of those mysteries.

Got another race weekend this week, it will be interesting as I did not get shift points with the 5 speed figured out last week as was concentrating more on the gauges and just general running.
_________________
Mike

'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

MikeJinCO · Posted: Mon Sep 27, 2021 10:34 pm Post subject:

Ran on Saturday at Pueblo. In the morning with cooler temperatures below 65 F the oil temps ran at 210. By mid afternoon at 85F the temperature started moving up to 240. My conclusion is that with rear axle ratio change I'm running higher rpm and producing more heat. Since I don't have any better location for the cooler a bigger better cooler is called for next year. In summer frequently run at 90+F at altitude of 5000 feet plus so efficiency is down a minimum of 15%.
_________________
Mike

'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

MikeJinCO · Posted: Wed Sep 29, 2021 3:42 am Post subject:

Hopefully this imgur picture will show up. This is the front end with the bumper removed. They only improvement I know of to make is to move the cooler further forward then making a deflector to move the air out the bottom so as not to have flow restriction from air having to pass thru the water radiator. I would like to have the 931 front panel vents for additional cooling and may try to do that this winter when I will make the entire lower panel (back around to the wheel wells)removable as the current setup requires many extra steps to load onto a trailer due to the very low approach angle.
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Mike

'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)