Oil temps: Looking for feedback from trombone users and upgraded cooler users

[chrisp]

The facts: at the track this past week I was running 250 deg F to 270 deg F and climbing (20 minutes run time). Yup, way too hot. FYI, I was running between 4,500RPM and 6,250RPM all day so I was using the engine under hard conditions. Lugging around in 4th at around 3,000RPM and 5,000RPM for one session did lower oil temps to between 220 deg and 250 deg. Pulled the front corner lights between sessions and it may have helped lower temps by 10 deg. Ambient temp all day was around 80-85 deg and it was very humid.

I currently have an 83SC with a stock trombone cooler filled with Mobil1. I know trombones run hot under track useage but are these temps an indication of another problem? I am fully prepared to upgrade to a fender radiator cooler. But while I am researching that, I want to investigate other potential causes, if any, for my high oil temps. I guess I was expecting trombone "hot" to be around 250 deg not 270 deg! That's why I am wondering.

Thanks for the help.

[Chuck Moreland]

Chrisp

Your temperatures are not indicative of a problem. The trombone is just not adequate for the track. For a lot of us 80-85 is a COOL track day. Imagine what you would have seen if it was hot!

You really need to upgrade the cooler to a Carrera style or other efficient cooler. That alone may prove marginally acceptable and your temps may still be high.

You may want to enhance that new cooler with improved air flow (box it in, remove turn signals, cut open headlight bucket, etc), Elephant Racing finned oil lines (orderable from our host) or a valence mounted cooler.

Here is a recent link in which I describe my results.

[pbs911]

I ran at California Speedway a couple weeks back in about 100 degree heat. With the Carrera cooler in place of the trombone cooler, and headlamp bucket cut out w/ headlamp removed, the temp never went above 230. Still a little woarm, but these were pretty extrme conditions. I plan on replacing the oil return line from the Carrera cooler with an Elephant line in the near future. I expect that should be good for another 5-10 degrees.

Even in daily stop and go driving in high 90 degree temps the Carrera cooler has keep the oil below 220, without the fan.

This is on a 78SC with the a/c condensor removed from the deck lid and cool collar.

[chrisp]

Thanks guys. This is very helpful. I am going to research what I can do for airflow to my new Carrera cooler once it's installed. I would like to retain all of my stock lights. I am thinking of buying a large rectangular scoop with a 3" inlet and use the scoop to cover the radiator with the 3" tubing leading to a scoop somewhere near the front bumper. This way I could channel all air directly through the radiator without concern for how well it seals to the fender and tub walls.

[Noel]

I have a 1980 SC with stock trombone. While at Nelson Ledges a couple weeks ago with the ambient temp around 80, my temps at the end of the 30min session would get up to 250, but when I saw this I would back down for a couple laps. I had my front turn signal out and I have just cleaned all the gunk off the trombone so it looked like brass when I was finished. I also used Mobil 1 15/50. The difference may be just the track too. Nelson Ledges is a very fast average speed track so I always had plenty of air flowing over the lines. Just my two cents. BTW, I also plan to upgrade to a Mocal cooler this winter.

Noel

[chrisp]

Thanks. My trombone is free of undercoating as well and average lap speed at Lime Rock is in the 75-80 mph range. Probably a good amount of airflow but I am not familiar with how this compares to your conditions at Nelson Ledges

[Wayne 962]

Ok, here is my compiled knowledge on oil coolers:

- No oil cooler. Bad for any 911 engine. Get one
- Trombone oil cooler. Better than none, but still not great. Used in the US because of emissions controls / need to keep temps up to reduce emissions
- European Brass tube oil cooler (also used in 1984 I believe on US Carreras, not 100% sure). This is a very good cooler, and my personal choice for durability and cooling (however, see below)
- Carrera oil cooler. This is the radiator style cooler. Good, but the early versions did not have the fan. Without the fan, I hear the brass-tube cooler is better
- Carrera oil cooler with fan. Best option for most cars. best cooling (better than stock brass cooler).

- Front mounted RS style cooler. Good for track use. Dangerous for street use without appropriate protection (concrete parking tiers, etc.).
- Left side fender coolers. Good additional cooling when combined with the right side.
- Cool collar. It works.
- S-tube cooler. Also works, although more expensive than the $30 cool collar

The law of diminishing returns applies here. The first cooling upgrade will give you good degree lowering per dollar. Subsequent upgrades will lower temps, but the price will go up...

-Wayne