In Gear Speeds

[Anthony Micallef]

Just out of interest can anyone tell me the maximum speed in each gear for a 5 speed 1.6 Superport running on 14" wheels.

 

At last I own one teeth.gifteeth.gifteeth.gif

 

 

Edited by - anthony micallef on 12 Mar 2002 16:03:00

[oilyhands]

Try downloading the gearing program that resides here it is DOS based but has all the most common gearbox ratios coded in, just hit F6 when asked for the first gear ratio and then select the desired box type.

 

Oily

 

Edited by - oilyhands on 12 Mar 2002 16:43:35

[Bob Corb]

For a Supersport (rev limit = 7600rpm, 185/60/14 tyres, and a std sierra 5spd box with a 3.92 diff) the back of my fag packet says :-

 

1st 2nd 3rd 4th 5th

 

39.1 72.5 104.2 131.2 160.1mph(??)

 

I wouldn't trust my figures though....

 

BC

Next year I'll learn to drive

[R500 CYA]

So buy a six speed!

 

8000 rpm in 6th = 128.1 using a 3.92 and 13" wheels. Much more realistic and considerably more fun on the track.

 

I have seen the change light in 4th with the 5 speed, but it took some doing and the windscreen to be off!

 

Nick

[edmandsd]

I'm sure you'r right Bob it's just the car won't pull the limiter in 5th !

 

I remember a guy once who calculated the top speed of his car on this basis convinced it would pull all the gears. I recommended he fit a Corvette box with a 0.50 6th and then that way his car would do 250mph ! It was a Morris Marina but with a 'Stage 3 head' if i recall.................whatever that means !

[EFA]

As of last weekend my car is setup for 171mph in 6th at 9500rpm. HOWEVER this means I wont blow the engine at the Ring on the straight, or anywhere else where I can sit flat out for minutes!

 

It is important to get the rest of the ratio's correct however, and IMHO any car which has a 1st gear ratio higher than 6.5mph/1000rpm will be slow off the line. Very sticky tyres will reduce this issue, but it certainly holds true for road tyres (ACB10's included.

 

On that fateful day in 2000 when Mr Krebs managed to beat me over a run up Santa Pod he ran a 6.21 1st gear and I ran a 7.38. Watch the video on my website to see the effect!

 

At Brooklands I ran a 6.21 1st as well and it resulted in the R500 being .5 secs slower to 60mph comparing best runs.

 

Gearing is probably more significant than engine power.

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

[Paul Ranson]

I don't think it's that simple.

 

You want to run the tallest gear that still allows the right amount of wheelspin. On my hillclimb car I usually run a 68mph first, which seems about right. I accidentally tried 83 once, I thought it was a little more reluctant than usual to do the burnouts... Anyway with your substantially reduced level of grip and traction perhaps a taller gear would work well.

 

Remember, 6000rpm, pop the clutch, feather the throttle to prevent run-away wheelspin, floor it. You know it makes sense.... If you don't run flat out in first gear for a time then the gear is too low.

 

IMHO of course.

 

Paul

[EFA]

Paul, It is that simple and here's why.

 

(Carmichael mode on)

 

 

The optimum traction is achieved at a point between loss of traction and peak torque output of the engine in 1st gear. The closer you can get these two values together, the better chance you have of hitting the sweet spot and getting a good clean start.

 

There is a sweet spot with any gear ratio. but that ratio then determines the stall (bog down) speed, so you end up in a situation where the car will bog down, or get masssive wheelspin, neither of which are condusive to a clean start.

 

Lower gearing (lower, not low) does not hamper the amount of drive you can get in 1st gear, but high revving engines benefit from being able to reduce the gearing to a value like 6.2mph/1000rpm and drive the car to 58mph, as a 9500rpm redline would give for example.

 

Clsoer ratiosn throughout the box, derived from a low CWP ratio also then means that your rpm drop below max power per gear is smaller, so you hit the power curver higher, and hence go quicker.

 

(Carmichael mode off)

 

With my new box I have gone from a 2.69 1st ration to a 2.39 which give a compound speed per 1000rpm increase from 6.21 to 6.99.

 

I reckon this will mean I cannot get my 0-60 to dip much below 4 secs, whereas before it would do a 3.3 happily.

 

Proof of the theory lies ultimately in the testing. Tomorrow I will know how the car feels after some shake down tests.

 

 

 

 

 

 

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>