Safe RPM for a 3.6 964 C2 engine?
Discussion
Had a replacement lump in put in the C2 and am finally back on the road. Is it good practice to take the car up to the Rev limit as the thing just wants to pull and pull up past 6000, or should I be taking it easy with the old gal and changing around 6?
Just need to know before her next track day.
Cheers
Pete
Just need to know before her next track day.
Cheers
Pete
thegoose said:
964RS. said:
Max rev limit is 6,700RPM +/- 20 but you should be changing at 6100RPM as this is the threshold of maximum power.
Shouldn't where you'll sit in the power band in the next gear also influence the revs you change up at?
.6100(ish) changes for me then. Ta.
Cheers
Lucky
I can't really see what damage you expect to occur by running into the rev limiter.
My experience of 964 engines on track is that the power begins to drop off before the limiter and that's the time to shift gear but it's still pulling hard at 6000rpm and it's a waste of available power to shift that early.
My experience of 964 engines on track is that the power begins to drop off before the limiter and that's the time to shift gear but it's still pulling hard at 6000rpm and it's a waste of available power to shift that early.
tony.t said:
I can't really see what damage you expect to occur by running into the rev limiter.
My experience of 964 engines on track is that the power begins to drop off before the limiter and that's the time to shift gear but it's still pulling hard at 6000rpm and it's a waste of available power to shift that early.
/agreedMy experience of 964 engines on track is that the power begins to drop off before the limiter and that's the time to shift gear but it's still pulling hard at 6000rpm and it's a waste of available power to shift that early.
I also take the view that the red line is there to be used --- and it should be a safe limit.
But it also depends upon the gear spacing, I have a 7.5 ton truck and the gearbox seems to be in two halves --- 1 and 2 work low, 3, 4 and 5 work high --- so a double declutch down to 2nd from 3rd is always a bit of a surprise ... and care is required.
And surely that's the point on over-revving, it's not going up the box that's the issue, it's coming down.
But it also depends upon the gear spacing, I have a 7.5 ton truck and the gearbox seems to be in two halves --- 1 and 2 work low, 3, 4 and 5 work high --- so a double declutch down to 2nd from 3rd is always a bit of a surprise ... and care is required.
And surely that's the point on over-revving, it's not going up the box that's the issue, it's coming down.
For max performance, the engine should always be kept between max torque and max power.
To save the engine, I always upshift around 6.200 rpm. As posted many times above torque (which is acceleration) is strong , so there is little point to go to the rev limiter unless racing, to save an unnecessarily short upshift just before a braking point.
BTW, this video illustrates those "early" upshifts... I just let the engine go past 6,200 in the Kemel straight...
http://uk.youtube.com/watch?v=SMbAN6nDuQ0
To save the engine, I always upshift around 6.200 rpm. As posted many times above torque (which is acceleration) is strong , so there is little point to go to the rev limiter unless racing, to save an unnecessarily short upshift just before a braking point.
BTW, this video illustrates those "early" upshifts... I just let the engine go past 6,200 in the Kemel straight...
http://uk.youtube.com/watch?v=SMbAN6nDuQ0
Edited by PhilRS on Monday 26th May 15:17
In any gear, maximum acceleration occurs when you keep the rpm of the engine in the widest possible average power area of the power band - in mathematical terms you are looking for the maximum "area under the curve". Interestingly every naturally aspirated 911 engine I have ever dyno tested has its peak power occuring within 800rpm of its rev limit, so irrespective of where peak torque occurs, what this means in practise is that you need to take to engine up to (but not into) the rev limiter in every gear in order to use that maximum area.
So, why not use lower revs and use the torque? In laymans terms, torque represents the size of the bang in the cylinder, whereas power is the cumulative effect of bangs per second, so although at peak torque the bangs are bigger, at peak power the higher frequency of slightly smaller bangs will win the race.
With respect to the 964 engine, the safe working rpm is 6800 and my recommendation is not to exceed this limit, but by all means use it as often as you like as no harm will come to your engine as a result.
So, why not use lower revs and use the torque? In laymans terms, torque represents the size of the bang in the cylinder, whereas power is the cumulative effect of bangs per second, so although at peak torque the bangs are bigger, at peak power the higher frequency of slightly smaller bangs will win the race.
With respect to the 964 engine, the safe working rpm is 6800 and my recommendation is not to exceed this limit, but by all means use it as often as you like as no harm will come to your engine as a result.
Edited by NineMeister on Monday 26th May 23:17
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