* ? re 3.6 engine - hot engine/performance

[Craig 930 RS]

Have 1997 Varioram 3.6 in the 79SC.
What system(s) are on the 993 engine with regards to:

Oil temp
Cylinder/engine case temp

I need some specific 993 engine system details that might explain a performance change based upon oil & or engine temperatures,
ie someone that is able to tell what system(s) dials back timing etc based on oil or cylinder temp.

This is installed in a 79SC with 2 oil coolers that need repositioning for better cooling. Seeing 230 to 240 on a hot day NOT GOOD.

Ideas?

[Craig 930 RS]

Muffinman, Thom, Jack, etc 3.6ers.....what do you think?

[widebody911]

I don't fully understand the question.

Air-cooled motors are known for heat soak and reduced performance.

When the engine gets hot, it can ping, which the knock sensor should detect and dial back the timing.

What kind of airflow do you have through your coolers, and have you verified the oil is getting to them?

[tholyoak]

Only temp inputs on the engines I am aware of are the air intake temp and the cylinder head temp. Oil temp is not used directly as far as i understand. As Thom states, as temps increase, chances for detonation increase which would cause the knock sensors to dial back timing

Todd

[MuffinMan]

I'm not sure what systems would retard the timing, or otherwise decrease performance. I once heard that ~210F is the optimum temperature for making horsepower, but I have no idea of the validity of that statement.

I'm running a front center cooler from a 2nd generation Mazda RX7 with plenty of flow area behind the cooler, and it also gets wicked hot on the track. When I'm at ~7 or 8/10ths and slowing down for traffic, the temperature is absolutely fine. But, give me a few open laps chasing down a C2 cup car and the temps SOAR. I saw 250F before I realized what how dramatic the temp diff was between previous runs and this one. Needless to say, I'll be changing out the oil cooler for something more efficient, and larger. I will most likely go with the B&B.

What coolers do you have in there now, Craig?

[Craig 930 RS]

I left the question open ended -

I am seeing reduced power under this situation:
80 degrees ambient
Oil temps 230-250 (yes, I know..not good at all)
Using a mix of race & 92 pump gas for a resulting 96 octane blend

No surprise here.
-----------------------------------------------
Pretty good size power increase at Portland this past Friday, granted the temps were 60 degrees with moister/denser air - as well as 'only' 210 oil temps

I wanted to know what systems may be reducing power besides heat soak and knock sensors - looks like there are no additional systems that would do this.

Oil is flowing fully through all cooler and the thermostat.
I have a B&B up front and a Carrera in the fenderwell with *2* fans. The oil temp problem is due to the fact that the front cooler is mounted - out of temporary necessity - about 1" from the pan.
This will change in a few weeks with the F(&R) Ruf style bumpers.

Intake temp is ambient.

So it sounds as if good old heat soak is causing this situation and no other engine system drawing the engine back in self-protect mode? If so the cooler ought to fix the situation about as much as can be expected.

[widebody911]

Originally posted by MuffinMan
But, give me a few open laps chasing down a C2 cup car and the temps SOAR.

My setup gives me the opposite problem; when I'm stuck behind SM's and vipers, my temps go up; when I can open it up, they go down.

Craig - can you post pix of your cooler setup?

[Bill Verburg]

No one asked me but, there is an intake air temp sensor that can alter timing and mixture, it is an input to the DME

[tholyoak]

My Mocal, is mounted no more than an inch or so from the tub behind the ruf bumper. But the bottom 1/3 or so hangs below the tub. Hooked in line with the 28-tube cooler in the wheel well via AN -16 lines, I can't get the temperatures over 200-210 even in the heat of the summer, as long as I am moving. Typically it sits at 180. If I get stuck in traffic in the heat for 45-60 min though, the temps get up to 250. So I think I need a fan.

[Craig 930 RS]

Mine is virtually identical in mounting as to Todd's red car - except it is unfortunately mounted higher.

The bottom line in my case is just virtually no air flow through the front cooler -

THX all!

[MuffinMan]

Originally posted by widebody911
My setup gives me the opposite problem; when I'm stuck behind SM's and vipers, my temps go up; when I can open it up, they go down.

Craig - can you post pix of your cooler setup?

In aforementioned situation, I was near redline/full throttle for a much greater portion of the open laps than when I was in traffic. I agree that all situations are not equal, but this was what I experienced at that event.

[widebody911]

Yes, you need a fan - my fan died, and I got stuck in traffic and had the exact same problem - temps went thru the roof and quickly.

My car doesn't have an IAS, but I'm sure the V-Ram motors do.

[Craig 930 RS]

The 4" SPAL *pusher* fan works very very well on these coolers - although they are a b*tch to find. Iowa Import/Export seems to be the only source - when they have them.

[Jack Olsen]

How aggressive is the re-programming on your OBDII DME? It sounds like you should have plenty of cooling capcity.

[Bill Verburg]

This cooler does my full 3.8RS nicely 80-90&degC under the worst street and under 100&degC on track. Single B&B


My chip is set up track rich