How to drive a peaky car

Sounds dumb but since the cam was changed in my rwd car and the power range moved up to 6000-7500 i seem to be getting slower !
so whats the best way to drive a peaky car ?

in a peaky hat ? :rofl:

mines like an asthmatic slug up to 4500, it all happens 5-7k, generally I just have to keep it there, and ended up changing Diffs to make it work properly, or tyre sizes is another option

Keep the revs up, by changing gear a lot. Adjust gear ratios so that in most corners you can stay in the power band, without running of out revs on the straight or being rubbish off the line.

But to me it sounds like you need to throw away the useless camshafts you now have, and put in sensible ones.

What car is it, and what sort of engine modifications has it had?

so whats the best way to drive a peaky car ?

"carefully" :)

its a 1380 cc rear drive with a full race engine the original cam allowed the power in at 4.5k but gave away some top end bhp and others race with this cam
that said i appreciate the advice so far and i think the first mistake im making is simply not changing gear sufficiently

I have seen this often before, you don't (IMHO) want the maximum cam available for road racing as what you may gain at the end of the power band you will loose for sure coming out of slow bends and its not just the cam its the exhaust as well especially the headers, I know someone who raced a V8 car and used to change the system for different circuits putting a 4 into one header for grunty circuits and a two into two into one for circuits like Lydden also the size of carbs and design of inlet manifold can dramatically change the rev band. You can get some monster cams for the Small Block Chevy engine over .7 inch lift massive durations to rev to 10,000 rpm but these are drag racing kit and just will not work on a circuit car. I remember when I used to do HotRods with the Kent engine years ago if you went to an A8 profile it was useless you had to use the A7 (from memory). Most important of all is you need a seriously close ratio set of gears.

What matters isn't the peak power figure, or even the peak torque figure, but the area under the curves of torque at the wheels versus road speed.

If you have finite number of gears (say 5), then having a wide torque spread (i.e. not very peaky) will usually beat the same car with a narrow torque spread (peaky), unless you are a very good driver, and/or can change the gearing of the car (either with ratios, CWP or tyre circumference).

The more data you have (torque curves, gear ratios, CWP ratios, tyre dimensions, expected highest and lowest road speeds etc) the easier it is to work out what is 'best', although driving is sometimes very different from theory, so ultimately it's the stopwatch and the driver that decide. But as track time in club racing is limited at best, getting as close as possible via theory is going to be better than spending a season trying all possible changes.

its a 1380 cc rear drive ......
Can you be a bit more specific, Spridget / A35 / A40 / Lotfield 11 or what?

One needs to make a choice, Out of the corner low end torque or high end top speed.

Normally Out of the corner torque and speed determains your top speed.

The question then, is it worth to have 2-4 mph more top end at the end of a long straight or get the 2-4 more mph out of the corner sooner?

My choice is got out of the corner ASAP and UP to Speed then have the extra 2-4 mph at the end of a long straight

Sounds dumb but since the cam was changed in my rwd car and the power range moved up to 6000-7500 i seem to be getting slower !
so whats the best way to drive a peaky car ?I completely agree there's no point pushing up your peak power if you've reduced the area under your power/torque curves - you'll just go slower.

But you didn't say that.. only that you've pushed the power up the rev band and you are going slower. So first thing to check is if you've reduced the area under the curves or not. If you don't have dyno/rolling road data of before and after, a rough and ready way is to have a think about where you're getting into top gear on the straights. If you feel you've got out of the previous corner really well but aren't grabbing top as soon as you expect, then you've probably hurt your mid range too much by going for top end power.

If your car still pulls really well once you're on the straight, but the problem is that you're bogging down as you actually come out of corners, then it's likely that its just a gearing thing. You might be getting a feeling of: nothing.. nothing yet... whoooo there it is! If that's the case you'll need to experiment with using a lower gear from the ones you're used to for various corners, or try changing to a slightly lower diff.

If, on the other hand, its a feeling of: nothing... nothing... Tooooo much! and you're getting all squirrely when the power comes in, then you may have gone a bit too far in a "peaky" direction and should think about going back to your old cams and look for a bit more power elsewhere. :)

You could also try playing around with the cam timing to change the characteristics. Advancing it up lowers the powerband as I believe does increasing the valve lash.

Flat out and No brakes just keep above the min rpm band. If you can't get on with it just downgrade the cam.

Just be brave and have faith in the roadholding. I have been driving a peaky cammed car for years . Get the car as light as possible, limit how much fuel you need, go on a diet if you need to. Make sure you can pull max revs in top gear on the fastest part of the circuit (I use 6 different diffs)
Lastly you may find this a stupid answer but don't floor the throttle coming out of slow corners if slightly below the power band . I only have a 4 speed box so you can do it.
The problem is worse on smaller cc engines that are cammed too much!

Anyway after Castle Combe why do you want to go faster ? :rofl:

Anyway after Castle Combe why do you want to go faster ? :rofl:
because Gordon this time i would like to get much higher before the car comes back down to earth ....!

i think it needs a change in driving behaviours - but im really grateful to you all for the time u've spent answering my dumb question(s)

because Gordon this time i would like to get much higher before the car comes back down to earth ....!

i think it needs a change in driving behaviours - but im really grateful to you all for the time u've spent answering my dumb question(s)


With a rev band that narrow,ever thought about a seven speed box.:laugh:

When 50cc motorcycle racing was big in the 60s some of the works bikes had 16 speeds !! Now "thats" a narrow power band.

Sounds dumb but since the cam was changed in my rwd car and the power range moved up to 6000-7500 i seem to be getting slower !
so whats the best way to drive a peaky car ?

Pah, call that peaky! Try 7500-8700! And my car weighs over 800Kg!

You have three ways to go -

- More gears, I ended up fitting a six speed box and have to make sure gearing is perfect by checking my data logging.

- Extend the rev range up to widen the power band. We ended up going to 9500RPM, power was dropping off (torque even more so) but with the benefit of gearing the car was still fast.

- More capacity/less cam to extend the power band downwards. I have just done this and the car is MUCH easier to drive. Whether it goes any quicker remains to be seen as lots of other unrelated things have gone wrong so far and we haven't had a decent run.

The order of the above is very deliberate. From our experience if you can make the car work with the smaller power band then it will be quicker, however six speed boxes, all steel bottom ends etc etc all cost money and if you haven't got/aren't stupid enough to spend it then you would be better off with a softer and more drivable engine.

As regards the driving, even a simple RPM recording tacho would help a lot. People without data logging rarely realise how 'imprecise' they are at keeping the engine within the power band. However even if you have data logging if you don't look at it AND do something about it then it is a waste of money.

Nahhh fit a chevy v8 Denis.

You know it'll fit!

Though I think that Gordon has it - maximising your gearing to use the revs. There's no point in running a diff which means you never find peak power at your fastest point.

When I ran my Nova (1300cc), it used to be 4.53 for Lydden (which was as low as I could get), 4.18 for most other circuits, but 3.94 for Combe (before they neutered the circuit). When I went to 1600, it was 4.53 for Lydden, 4.18 for Brands, 3.94 most everywhere else, and 3.74 for Combe / Thruxton.

All this talk of data logging is starting to make me come out in a cold sweat. Do I need to add more wedge, or take some out?

- More capacity/less cam to extend the power band downwards. I have just done this and the car is MUCH easier to drive. Whether it goes any quicker remains to be seen as lots of other unrelated things have gone wrong so far and we haven't had a decent run.


.
Denis you will find if you increase the cc you can get away with the same radical cam as it tends to soften it !
As I already said, small cc engines don't really like big cams !

Denis you will find if you increase the cc you can get away with the same radical cam as it tends to soften it !
As I already said, small cc engines don't really like big cams !

I would use the term 'mask' the more negative effects of a radical cam, we certaily lost nothing at the top end with the capacity increase, despite the reduction in bore to stroke ratio.

Small CC engine love big cams, you just have to develop a whole new attitude to bottom end strength, rev limits, drivability at low revs/part throttle etc.

A good example is a standard 4age will make around 97-110ftlbs at 4800RPM-5800RPM (depending on small or large port head). With bigger fast road/rally cams you can easily get to 125-130ftlbs but this is at 6000-6500RPM. With proper race cams etc you can see 135ftlb but this will be at 7000RPM+.

Not only do you get more torque, it also 'holds on' to it for longer. The standard engine usefully revs to 7200ish RPM, the fast road/rally engine around 8700RPM and the race engine will rev past 9200RPM.

And being at a higher RPM you can regear and get further benefits.

Of course the downside is lumpy idle (I set mine to 2000RPM), appalling economy, poor low speed drivability, constant rebuilds etc. However none of these should be a big issue on a race car.

When 50cc motorcycle racing was big in the 60s some of the works bikes had 16 speeds !! Now "thats" a narrow power band.

We have a 50cc Honda CR110, which is "only" 8 speed. The power band is about 1000rpm. 15,200-16,200. :)

Anyway, interesting topic. I had years of gearbox karting experience before I switched to cars - I also happen to be building a Mazda RX-7 to race. Both two stroke and rotary engines are very peaky in their racing forms, so I think I've already learnt the hard bit.

With a really peaky engine you can't afford to let the revs drop, you have to stay "on it" at all times. Using a front wheel drive "slow in, power through" cornering method seems to be what works best.

The thing I've noticed most about racing a peaky powered vehicle against torquey V8's for example is that you have to put a lot more thought in when lapping and battling. You can't afford to lift off the throttle where you wouldn't on a clean lap, because the cars with lots of bottom end will just eat you up.

Thanks for all the replies - it seemed to work best result of the year - so thanks very much