Track Oil Pressure Drop

[macnewma]

I time trial and do lapping days in my 86 944 Turbo (about 280-300rwhp). I currently run M1 15w50 and I am seeing my oil pressures drop during a session. 5bar is normal oil pressure when cool to warm. When hot, on throttle I see 4bar and at idle I see 2.5bar.

I am concerned that my oil is thinning due to high oil temps. I am in the process of installing an aux oil cooler, but I would like to make sure that I am running the best oil for my setup.

This car is used on the street as well as track and the oil can see temps of up to 280F in the pan. I cannot use Redline's racing oils due to a lack of detergents. Here is a list of oils I am considering:

1. Redline 5w-40, 10w-40
2. Amsoil S2000 20w-50, 0w-30
3. Synergyn 5w-50, 15w-50
4. Royal Purple 21
5. Torco, not sure which one
6. Valvoline VR1
7. M1R 0w-30
8. M1 Truck/SUV 5w-40

As you can see I am all over the board on this. I really want an oil that will maintain my oil pressure as I am road racing and I don't want to starve my rod bearings.

Any suggestions?

Max

 

[Durrr]

Synergn 5w-50 and Royal Purple 21 and also take a look at 41 too. Both are solid racing setups. May also want to take a look at M1 0w-30 R. Special racing formulation that has an incredible additive package.

Edit : btw, do you lose pressure around corners? cause your oil could be sloshing around and you MIGHT need a baffled oil pan. Just something to think about

 

[Michael SR]

max, given the ht/hs figures, the only oil i see on your list that matches M1 15w50 is the amsoil 20w50. my guess is that every other one would show even less pressure at those temps.

also, do you think 4bar is too low?

redline 20w50 isn't one of their "racing" oils, but has a very impressive ht/hs.

-michael

 

[macnewma]

Durr-

Why do you suggest the Synergyn 5w-50 over the 15w-50?

Also, is M1R 0w-30 too thin? So many racers are stuck on using the heavier weights, is this smart?

Also, this isn't due to cornering, not that it isn't a concern. This low oil pressure is seen on straights as well.

Michael SR-

I am not an oil expert by any stretch, but is HT/HS the main indicator I should look at in a race oil? I thought this was an indicator of how quickly an oil breaks down over a longer period of time. I am concerned only in the short run. I don't need long OCIs as much as maximum protection for at least a weekend of racing.

Max

 

[Michael SR]

quote:

---

Originally posted by macnewma:
I am not an oil expert by any stretch, but is HT/HS the main indicator I should look at in a race oil? I thought this was an indicator of how quickly an oil breaks down over a longer period of time.

---

i'm not an expert either, but my understanding is that ht/hs is a measure of what the viscosity will be if/when at 150°C and being sheared. i've heard it said this approximates severe duty inside a bearing.

so i think of ht/hs as the viscosity of oil when on track, very hot, and revving hard.

whether or not it's the "main indicator," i don't know. i bet plenty will argue otherwise, and M1R is a good example of this since mobil claims the ht/hs is only 2.9.

but if you're worried about oil pressure readings (and i'm not trying to comment on whether or not you should be because i really don't know anything about your car/engine), and you're hitting ~280°, i'd say the ht/hs is a decent indicator of what oil pressure you will see on track.

about the car, what did you do to up the power to that level? just boost, or more? does the porsche manual say anything about what pressures are acceptable?

also, if the manual specs 20w50 for street use at the ambient temps you race at, then i would stick with a 50 weight for sure.

-michael

 

[Durrr]

well, true, I didn't take into account what the manufacturer's specs are. But, I like the 5w-50 because it flows well, and has a killer additive package. Just do some searches on here, some of the most solid stuff out there (though can be tough to find at times). But, if the manu. specs 20w-50 for OEM, then I'd stick with a 50 weight in the upper end for sure. As for the rest, find a good additive package/something that will hold up and a solid filter.

 

[theguru]

Can you get the Motul 300v oils? Worth considering if you can.

 

[Lance]

I sponsor a friend running an alcohol fueled sprint car. He is almost finished with the season. My sponsorship consists of providing 5 gallons of Amsoil 20W50 High performance motor oil, no charge,(NOT S2000). We are planning to analyze and change the oil, due to 2 overheating events, and the fact that he's first in points and may just take the top prize this year. I'll be happy to post the results for your enlightenment. I am an Amsoil dealer.

 

[k1xv]

Wow, 280F in the sump sounds very high for a water cooled engine. You need an oil cooler badly to bring that down by at least 40F or so. Oil that is 280F in the sump is even hotter at the hottest locations in the engine, and at these locations, such as piston bottoms, oil is the primary means of cooling those engine components.

Once you bring the oil temperature down, your choice of oils becomes simpler.

 

[KJA426]

As mentioned earlier, Redline makes a 20w-50 "street" oil.

 

[Eddie]

From my racing experience with Porsche 911s I don't feel that 280 degree sump temp is too high, especially with Mobil 1. Why don't you contact the mobil site with your concerns and get an ? expert opinion rather than NG guesses.

 

[k1xv]

Obviously, the 911 is air cooled whereas the 944 turbo is water cooled. Air cooled engines will generally run higher oil temps than water cooled engines.

 

[terryr]

280 is way high. I have read racers worrying about 250 F. The hotter an oil gets the faster it breaks down.

I would say use a thick synthetic and get that oil cooler.

 

[Santo Fontana]

I asked Synergyn about their 5w50 and they said they dont make it anymore.

 

[KobaltBlau]

The original poster may not care about this anymore, but I just saw it so I'll post my experiences:

The pressure drop isn't really a problem unless your oil pressure gets lower than you are comfortable with. the "hot" figures you mentioned are just fine IMO. This happens all the time with air cooled porsche engines.

I would guess based on your pressure drop that your oil is seeing temps in the 240F range. BUT you really should get an oil temp gauge, see if you really need the cooler.

If I were you what I would do is add an accusump device, since you have a wet sump. 944s and 951s are known to spin rod bearings on occasion on the track, and the accusump adds a nice big pressure reservoir to save you from that.