What does the torque curve for engine braking or "coast" condition for an F1 car typically look like? Pretty much flat? Does idle have any effect on it, or do F1 cars use some kind of "smart" idle that only works in neutral, or maximizes driveability etc? Thanks.
Engine Braking Torque Curve
Started by
Aubwi
, Feb 17 2004 16:06
8 replies to this topic
Advertisement
#2
perfectelise
-
- 244 posts
- Joined: December 00
Member
Posted 17 February 2004 - 18:40
A few years back, during a race, David Couthard crashed on the first slow bend entering the pit lane. His explanation was that a failure in the idle strategy resulted in a lack of engine braking which gave him excessive speed. This was unexpected and he did not react fast enough to increase braking. The term "idle strategy" suggests the engine braking torque curve is adjustable.
#3
panzani
-
- 18,732 posts
- Joined: September 03
Member
Posted 17 February 2004 - 18:51
I've seem on Williams and McLaren and Ferrari's steering wheels a button to increase/decrease engine's braking dinamycs so it is adjustable, indeed.
#4
Aubwi
-
- 453 posts
- Joined: January 02
Member
Posted 17 February 2004 - 18:53
Very interesting! I'm a little suprised they wouldn't just go for maximum engine braking to save fuel and reduce brake cooling requirements. 
#5
panzani
-
- 18,732 posts
- Joined: September 03
Member
Posted 17 February 2004 - 19:57
I guess when you're at the end of a long straight and you need all available braking forces to go down from 360 to 80Km/h you use full engine's braking; but when you're in the middle of a left/right medium speed chicane you just touch the braking pedals and keep on the engine throttle for the following full acceleration needs. But I may be wrong, of course...
#6
McGuire
-
- 9,218 posts
- Joined: October 03
Member
Posted 20 February 2004 - 07:44
I'm sorry but I don't follow this thread at all. How can the engine's braking properties be controlled once the throttle is closed? Seems to me that engine braking would be a function mainly of the engine's compression vs. how quickly the throttles return to idle.
And anyway, how would it make much difference in the car's overall deceleration rate, considering the brakes are capable of slowing the car at a rate somewhere in the range of 5 g? Also, these cars carry so much downforce that the resultant drag slows the car at 1+ g just by taking one's foot off the throttle (which is more braking than most street cars have in total). I can see where "closed-throttle driveability" i.e. throttle closure rate is an issue, but not due to engine braking per se. Please enlighten me.
And anyway, how would it make much difference in the car's overall deceleration rate, considering the brakes are capable of slowing the car at a rate somewhere in the range of 5 g? Also, these cars carry so much downforce that the resultant drag slows the car at 1+ g just by taking one's foot off the throttle (which is more braking than most street cars have in total). I can see where "closed-throttle driveability" i.e. throttle closure rate is an issue, but not due to engine braking per se. Please enlighten me.
#7
perfectelise
-
- 244 posts
- Joined: December 00
Member
Posted 20 February 2004 - 11:15
If fuel is still being burnt when the throtle is closed, as at idle and during engine braking (but not always), then there is still a power stroke and the piston is being helped down the cylinder. The amount of engine braking can be adjusted by varying the amount of fuel being burnt when the throltle is closed. I think that's it.
#8
Greg Locock
-
- 6,495 posts
- Joined: March 03
Member
Posted 28 February 2004 - 03:36
I'm not sure how relevant this is, but say fifteen years ago it was common to control the throttle-off response of production cars - if you have such a car (eg VW Jetta 1988) try releasing the throttle at 2500 rpm in neutral, you'll typically see the speed drop to about 1200, then pick up to 1800, then drop to idle. It was part of the emissions strategy, I guess to burn off the fuel that had been injected (if it was TBI) before the throttle was cut.
#9
Fat Boy
-
- 2,594 posts
- Joined: January 04
Member
Posted 28 February 2004 - 05:02
I'm not sure how you would go about testing it on a dyno, but at the track, I have worked with different throttle plate settings with the pedal released. Even with the throttle release, the blades will be a touch open to keep the engine ticking over.
At one point it was advantageous to have the throttle plates slightly more open at idle, but the actual idle speed was brought back down by playing with spark timing and running the fuel very lean. This was originally done to get better throttle response, but a side effect was that there was considerably less engine braking. It was enough that the drivers had to change their brake bias setting. It didn't really seem to effect lap time much, though.
I don't know if that helps, just my experience.
At one point it was advantageous to have the throttle plates slightly more open at idle, but the actual idle speed was brought back down by playing with spark timing and running the fuel very lean. This was originally done to get better throttle response, but a side effect was that there was considerably less engine braking. It was enough that the drivers had to change their brake bias setting. It didn't really seem to effect lap time much, though.
I don't know if that helps, just my experience.
