24 replies to this topic

[Awlred Drives a Quant]

And how many “suspected” miles has this wonderful 998 done?

If the old clocks were right its done nearly 102k

Just curious about it to know if I'm shifting too early as I was distracted when I was in 3rd and so shifted later than normal and it just seemed to have more kick than my normal shift at about 3000RPM

[biggav]

i got a 296 cam....

surely you want to change gear above peak power so so that you are nearer to peak power after the change??

[Jimmyarm]

i got a 296 cam....

surely you want to change gear above peak power so so that you are nearer to peak power after the change??

But dont forget you have peak torque lower down (which is what gives you more going forward force), once you have gone past peak BHP you are just wasting time losing power so you are better shifting literally just past it so that you drop down to where you are making peak torque so that you have that to keep you accelerating and as that tails off the BHP takes over ?

It makes sense in my head, honest !

[Sprocket]

Are we talking about peak power or shift point, because the two couldnt be further apart!!

[Jimmyarm]

The shift point

Tell us how its meant to be done Mr Sprocket !

[fikus01]

im with sprocket, gear change shud happen when the engine is happy but starting to run out or noticable pull!! max power could happen at 5800 but the engine mite not lose a large anount of that power til 7000rpm!! it depends how fast the power curve drops down after max power!!

[Sprocket]

Its all to do with torque and gear ratios.

The best time to change gear is the point where, when you change from first to second, second to third and third to fourth, transmitted torque to the wheels drops the least between each change.

You need a rolling road print out for your engine, you then need to know the final drive ratio as well as the first second and third gear ratios.

Work out overall gear ratios, first second and third. Fourth will always be the same as final drive ratio.

Take these ratios in each gear and multiply it by the torque figures at 1000 rpm intervals right up to 6000rpm. Draw up a table with all these readings, rpm on the left and gear/ overall final drive ratio across the top.

From this table work out the best rpm that is common to all gears that has the least drop between gears in transmitted torque. This becomes your shift point and where to set your shift light, if you have one.

This is the basics of drag racing.

Like i said, it has nothing to do with power, nor the peak torque.

Edited by Mini Sprocket, 16 December 2006 - 05:37 PM.

[Jimmyarm]

Thanks Mr Sprocket, time to dig out that RR print out and see whats what !

Mind you its sunday tomorrow so I get to take the beast (645ci) out Will have a hunt around and see if I can find a power graph for that !

[Jimmyarm]

PS you forgot 4th to 5th and 5th to 6th

[Sprocket]

PS you forgot 4th to 5th and 5th to 6th

How many people can afford and have a five speed box, let alone a six speed box at 7k new!!!!!

As we were talking about the mini, i wouldnt be using fith for accelerating, unless its a KAD true 1:1 fifth