Chris Gilbert: "No more than 90% of the power band"

[jameslb101]

So I'm watching a Chris Gilbert DVD and he talks, in the context of making maximum progress, about changing up at peak power, which in the car he is driving is at 5k (with a redline of 6k).

"You're wasting your time holding on to the gear beyond the 90% because you're actually loosing performance"

Ignoring the fact that 5k out of 6k isn't 90% he has a point. On a normal petrol car power drops off before the redline.

But surely if you use the range (for example) of 4k - 6k rather than 3k - 5k, the area under the graph (work done) is greater so the acceleration will be greater.

Not only that, but because you're in a lower (shorter) gear for more of the time, the torque at the wheels will be greater as the engine is being geared down less.

Can anyone shed light?

Reference for my second point:

[stefan einz]

He's talking bollocks. Hope that helps...

+1.

A number of cars that I have driven have peak power precisely at peak revs, so his starting assumption is wrong. It depends. And the other factor is that, if you change up before peak revs, do you drop down too low in the powerband?

[Astraist]

it does not sound quite right. There are petrol cars where you might even need to pull the revs past peak power to overcome a gap in between the lower gears.

Is it possible that this assertion derives from other aspects like always keeping more power available?

[martine]

He's talking bollocks. Hope that helps...

[waremark]

In Autocar road tests, I often look at the in-gear acceleration times - they give the time taken for 20 mph acceleration bands in each available gear. The fastest time is always (well, certainly very nearly always) achieved (even in diesel cars) in the lowest gear which can run to that speed.

[cupraray]

When you can achieve all that Chris Gilbert has achieved, then your comments might be worth taking into account. But what I've read from all of you,literally all of you, is total rubbish.

[stefan einz]

When you can achieve all that Chris Gilbert has achieved, then your comments might be worth taking into account. But what I've read from all of you,literally all of you, is total rubbish.

In what way "rubbish"?

[trashbat]

Here's my dyno graph for realsies, lumpy as it may be. Common or garden N/A petrol two litre.



I can't be bothered to find out the specific gear ratios and what revs you'd drop to by changing up before peak in any gear, but it's definitely not going to be optimal.

[Keithrm]

When you can achieve all that Chris Gilbert has achieved, then your comments might be worth taking into account. But what I've read from all of you,literally all of you, is total rubbish.

Strange response to a well debated thread
Who is this Chris Gilbert anyway

[watts93]

When you can achieve all that Chris Gilbert has achieved, then your comments might be worth taking into account. But what I've read from all of you,literally all of you, is total rubbish.

I'm happy to be corrected but as far as I can Chris Gilbert is wrong and the other posters are correct. Here is an mx5 mk1 dyno plot with some points marked on:



The red line on this engine is at 7000rpm but the rev limiter doesn't kick in till about 7300rpm.

I have marked on the graph the Chris Gilbert recommended change point at 90% max rpm (line 2) and the resultant drop in engine rpm from the gear change (line 1). I Have also marked on changing at 7000rpm (line B) and the resultant rpm (line A). Both examples are from 2nd gear to 3rd gear. As you can see using Chris Gilbert's recommended gear change point, which is before peak power, leaves you much further down the power curve after the gear change.In comparison changing slightly after peak power at max rpm drops you higher up the power curve. Although I didn't teach the royals to drive so all of the above, literally all of it, maybe total rubbish.

[WhoseGeneration]

Doesn't matter, because after the EU mandated gearshift indicators, there'll be EU mandated vehicle controlled gearshifts.
You all know why.

[zadocbrown]

Maybe we are taking Chris Gilbert's statement out of context. Obviously posters here are correct in terms of squeezing the last drop of performance out of a vehicle. CG must surely realise this though? I don't think he is into motorsport, so I suspect his advice is a pragmatic approach to road driving. Driving on road in a typical road car I would agree there is no practical gain in bouncing off the rev limiter all the time.

[waremark]

Maybe we are taking Chris Gilbert's statement out of context. Obviously posters here are correct in terms of squeezing the last drop of performance out of a vehicle. CG must surely realise this though? I don't think he is into motorsport, so I suspect his advice is a pragmatic approach to road driving. Driving on road in a typical road car I would agree there is no practical gain in bouncing off the rev limiter all the time.

But apparently he says: 'beyond the 90% because you're actually loosing performance'.

That is wrong regardless of context.

The pros and cons of regularly using the top of the rev range are quite another matter. Factors include whether or not you find it pleasant, how much there is to gain performance wise, and whether what there is to gain is something you are looking for. Ironically, I more often use the top end of the rev range in high performance cars in which the sound stirs the soul than in the lowest performance car which I drive regularly, which sounds to me as though it is being thrashed when you go beyond 4,500 rpm.

[Astraist]

When you can achieve all that Chris Gilbert has achieved, then your comments might be worth taking into account. But what I've read from all of you,literally all of you, is total rubbish.

Ad Hominem much?

[jcochrane]

When you can achieve all that Chris Gilbert has achieved, then your comments might be worth taking into account. But what I've read from all of you,literally all of you, is total rubbish.

Strange response to a well debated thread
Who is this Chris Gilbert anyway

I saw the wink but it is an interesting point. Apart from his police driving and instrutor experience at Hendon I'm not aware of any broader experience or knowledge in driving or car technology. I can remember the debates between him and Sir John Whitmore and wondered then the same thing. Not intended as a dig but would be genuinly interested to know.