997.2 3.8 Engine Failure
05-11-2019, 09:56 AM
#796
Rennlist Member
05-11-2019, 11:55 AM
#797
I thought it was pretty much decided that idling these motors to warm them up creates all kinds of other problems ... Start and drive off gently almost immediately.
Not trying to be difficult here. I'd really like an answer (solution?) regarding how to do an Auto X without risking cold seizure or other damage.
Not trying to be difficult here. I'd really like an answer (solution?) regarding how to do an Auto X without risking cold seizure or other damage.
05-11-2019, 12:22 PM
#798
Rennlist Member
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For all 26 track days I've had my BS on track, before each session regardless of what temp l the motor is, I start it up and use the throttle to hold the RPM between 1,200 and 1,600 RPM, varying it a bit, but not letting it do a slow idle and not zapping the throttle to zing RPM up. I do this until my Cobb AP shows engine oil and water temp are above ~205 and then I select sport plus mode and let the engine idle. Sport or sport plus mode idles at 800 RPM instead of 625. This 205+ temp usually occurs while sitting on the grid waiting to go out, but if something causes a long delay after I start idling in sport plus mode, say more than 5 minutes, I shut the engine down. The first 2 miles or so on track, I keep RPM below 5,000 RPM and don't use full throttle. Then I hammer it but always (almost always) upshift at 7,000 RPM even though redline is 7,800. Because there isn't much power increase above 7,000 anyway, and there's no sense stressing the engine internals. Forces and friction increase exponentially with RPM.
05-11-2019, 12:38 PM
#799
RL Community Team
Rennlist Member
Rennlist Member
Auto X.... I had the same question back when I was tracking..... you would all sit around... sometimes it was just cold.. with a coat on..... you wait until your run group comes up.... idle through the paddock .... sit in line idling, and then FULL THROTTLE..YEEEHAAA!!!!~.. hmmm.... no way were any of the cars warmed up.
Peace
Bruce in Philly
Peace
Bruce in Philly
05-11-2019, 02:43 PM
#800
Nordschleife Master
I thought it was pretty much decided that idling these motors to warm them up creates all kinds of other problems ... Start and drive off gently almost immediately.
Not trying to be difficult here. I'd really like an answer (solution?) regarding how to do an Auto X without risking cold seizure or other damage.
Not trying to be difficult here. I'd really like an answer (solution?) regarding how to do an Auto X without risking cold seizure or other damage.
To autox... drive to the track and warm the car. Keep it warm while it is there. By warm I mean oil temp correct and full engine block warm.
05-11-2019, 03:36 PM
#801
Try driving your car in manual, using the shifter like you would change in a stick shift. Engine warms up a lot quicker than in automatic when your in 6th gear 100 yds from where you set off.
05-11-2019, 04:40 PM
#802
Rennlist Member
Starting and idling is only an issue when the engine is cold and runs rich. You can idle all you want once it is warm and the mixture is normal.
To autox... drive to the track and warm the car. Keep it warm while it is there. By warm I mean oil temp correct and full engine block warm.
To autox... drive to the track and warm the car. Keep it warm while it is there. By warm I mean oil temp correct and full engine block warm.
05-11-2019, 04:57 PM
#803
Burning Brakes
I have observed that as well. But, in automatic mode you are warming the engine and oil up in as gentle a manner as possible. Which is better for these engines?
05-11-2019, 05:39 PM
#804
Just sayin, that if you had a manual trans in your car the oil and engine would warm up quicker than a PDK trans. Probably the PDK is set up for max fuel economy, as when I drive my car in manual I use a lot more fuel.
Bottom line is that these engines are meant to be driven.
Bottom line is that these engines are meant to be driven.
05-11-2019, 06:04 PM
#805
Good info all!!! Thanks 8)
05-12-2019, 02:35 AM
#806
LSPI (or detonation for that matter) can cause damage to the piston including the piston skirts, so anything is possible.
Rod/stroke ratios, piston skirt size/cam profile, piston offsets, crank angles, etc. all have play in this. Lots of variables with many unknowns and assumptions.
We made one observations early on with Cayenne and 9A1 engines - the pistons have a very hefty pin offset. With the M96/M97, we were able to make the pistons with no offset without having piston noise. We tried this with the Cayenne and 9A1 and the engines sounded like a Porsche diesel tractor. We ended up having to put the offsets into the pistons, leading me to believe (again my opinion) that the forces acting upon the pistons at BDC are greater in these engines due to possibly less favorable engine geometry and lower rod/stroke ratios.
Historically, Porsche has used a fixed deck height (with aircooled and watercooled engines alike) which means as the crank stroke increases, piston pin location must be moved further up towards the top of the piston, resulting in shorter pistons, and typically shorter rods, which results in less favorable rod/stroke ratios. The higher the rod/stroke ratio, the lower the cylinder wear and piston side loading.
Rod/stroke ratios, piston skirt size/cam profile, piston offsets, crank angles, etc. all have play in this. Lots of variables with many unknowns and assumptions.
We made one observations early on with Cayenne and 9A1 engines - the pistons have a very hefty pin offset. With the M96/M97, we were able to make the pistons with no offset without having piston noise. We tried this with the Cayenne and 9A1 and the engines sounded like a Porsche diesel tractor. We ended up having to put the offsets into the pistons, leading me to believe (again my opinion) that the forces acting upon the pistons at BDC are greater in these engines due to possibly less favorable engine geometry and lower rod/stroke ratios.
Historically, Porsche has used a fixed deck height (with aircooled and watercooled engines alike) which means as the crank stroke increases, piston pin location must be moved further up towards the top of the piston, resulting in shorter pistons, and typically shorter rods, which results in less favorable rod/stroke ratios. The higher the rod/stroke ratio, the lower the cylinder wear and piston side loading.
05-12-2019, 02:45 AM
#807
Nordschleife Master
Just sayin, that if you had a manual trans in your car the oil and engine would warm up quicker than a PDK trans. Probably the PDK is set up for max fuel economy, as when I drive my car in manual I use a lot more fuel.
Bottom line is that these engines are meant to be driven.
Bottom line is that these engines are meant to be driven.
So I see no good reason to ever be in auto/normal mode with a PDK car with or without SC. How can being in 6th gear at 30 mph and just below 1,500 rpm be healthy for the engine even when warming up? Lugging comes to mind. https://www.roadandtrack.com/car-cul...ad-for-engine/
05-12-2019, 11:57 AM
#808
Rennlist Member
Its better to have both: higher RPMs circulate oil and water faster without putting too much load/stress on the engine. When I say higher, I mean between 2,000-3,000, as opposed to 1500-2500.
05-12-2019, 09:34 PM
#809
Three Wheelin'
Perhaps Porsche should hire some BMW engineers that know a thing or 2 about the BMW's flat twin engines, or at the very least identify what the root cause of the Porsche's flat 6 engine problems.
05-12-2019, 11:43 PM
#810
