What is your Peak shift point

[pikey motorsports]

talking of rev limits and such got me thinking.... does anyone know their "peak shift" figure?

looking at my dyno sheet from last weekend, mine appears to be 5800rpm, thats when i am at peak bhp and within 20lb/ft of peak torque, so would be a sensible place to shift up no?

if im getting that wrong someone please explain it to me

 

[RobBentley]

Re: What is your redline rev limit

I'd have thought it better to shift just after you hit peak horsepower when you do hit peak torque. That said, I experimented with various shift points at Santa Pod in the R36, and it always proved fastest to rag every last RPM out of it. So then I got all confused..

 

[obi_waynne]

I tend to change (when driving in anger) at 5000rpm (there is probably another 1000 usable RPM), but this seems to be the point where the engine is just running out of puff and when I've changed up the engine is already well into the torque curve.

Not really tried this on the clock or Dyno and it would certainly be interesting to know. I would guess you make more rapid acceleration in the Peak Torque band rather than the BHP peaks.

The redline is certainly never the peak shift point in pretty much all cars. You need to find the Peak Torque figure to determine this ideally.

 

[HDi fun]

Mine sorts itself out quite nicely.

 

[Jakeymd]

It varies from gear to gear. You're after the highest wheel torque possible at each speed. The gearbox acts a torque multiplier so wheel torque is reduced as the gears get higher. but sometimes it's better to shift earlier in any particular gear because as your torque drops off the matching wheel torque in the next gear may be higher as it falls into the peak torque band. This is more likely in higher gears as the ratios are usually much closer together. In lower gears it's usually best to change at the redline for fastest acceleration.
You would need to study your torque curve and your gear ratios to find when is best in each gear.

 

[RobBentley]

I was going to say before your reply about wheel torque that when I went to Santa Pod with the RS4 as much as I tried these theories out it always ran fastest when I squeezed out every last rpm!

 

[bigbadjoe]

About 7200. Since my last remap. Before it was about 6000 but now, I get good pull untill I hit the limmiter about 9000. Forth is a little less. about 6900 in forth, but at that point, (so I have been told(lol)) you are doing 140mph so you don't really check! :blink1:

 

[old-git]

If you have a power graph and know the RPM drop when changing in each gear, then it is easy to work out optimum gear change RPM

The idea is to find the gear change RPM that gives you the greatest area under the graph when drawing two verticle lines from the shift point and the new RPM after the change. For example, if you change at 8000 and the RPM drops to 6000 draw your lines from these points and work out the area underneath the graph. By simply looking at the graph it is relatively easy to see whether by moving the gear change RPM you can increase this area. The larger this area the higher the average BHP is during the change period.

The gear change RPM will be different for each gear as the distance between each gear ratio is different and this will affect the RPM drop.

Told you it was simple

 

[old-git]

Re: What is your redline rev limit

I'd have thought it better to shift just after you hit peak horsepower when you do hit peak torque. That said, I experimented with various shift points at Santa Pod in the R36, and it always proved fastest to rag every last RPM out of it. So then I got all confused..

If you look at your power graph, you will probably see that max RPM is the best shift point based on the area under the graph (see my previous post). Max power RPM is not normally the best time to shift as the RPM loss usually drops you out of the power band.