How many MPH per 1k revs?

[The AJP Griff]

Hi all,just doing a little gearing calculation,and was wondering how many mph/1000rpm a 4.5 cerb does with 18" wheels in fifth gear?What ratio diff is this with,and where is the red line for a 4.5 red rose please?Cheers,Mike

Edited by The AJP Griff on Tuesday 7th August 20:17

[The AJP Griff]

Boing!!Anyone?

[RUSSELLM]

I think mine, does 27mph per 1k revs, i'll confirm that after the weekend on the sat nav, not the ridiculous speedo readings

gear ratios
1st 2.95:1
2nd 1.95:1
3rd 1.34:1
4th 1.00:1
5th 0.80:1
LSD 3.45:1

max revs (not red rose) 7500

Don't know if any of that helps.

[The AJP Griff]

Cheers Russel,thanks for that,just what i wanted to hear if it turns out to be a real 27mph/1k

[RUSSELLM]

Providing my rev counter's correct, I reckon my fifth is 25mph per 1K revs, may be slightly more, but closer to 25 than 26.

Hope that helps.

[Byker28i]

21mph in 4th , 27mph in 5th based on speeds at 7K revs

Hence the 190mph claim?

[RUSSELLM]

I reckon my speedo shows 27mph per 1K, but the tom tom was definitely closer to 25mph.

That said, each car's gearing's got to be different.

A lot of us went through the chequered flag with the buzzer on in 4th gear, and all achieved different terminal speeds.

Good old TVR

[V8Cerbera]

IIRC, the last time this was queried someone sprang up with 26.6MPH/1k in 5th gear.

[RUSSELLM]

I think they quote 195.

However, they also quote 420 bhp & 0-60 in 8.1 seconds

For me it's 25mph x 7.5k = 187.50.

I do wonder if they were using the car's speedo & a grandfather clock, when they put some of those figures together.

[V8Cerbera]

I thought the buzzer was set to about 6,800rpm...?

For me then that would be 25x6.8 - 170mph, but I know damn well that I've had her up to 180 with no buzzer.....

I find my speedo to be very accurate BTW - If the speedo says I'm doing 100 then tom tom agrees entirely.

[RUSSELLM]

Is the buzzer and the max revs the same figure though.

The book quotes 7500 for the maximum revs.

I'm wondering if the buzzer is a "recommendation" warning

[V8Cerbera]

AFAIK the buzzer is a recommendation to shift gears. Mine revs right round to 8k (though I wouldn't recommend it). Rather like the shift lights in a tuscan...

Green light - Please change gear
Amber light - Seriously dude, change gear
Red light (right in your eyes) - If you don't change now you're gonna break the engine!!!!

[BCA]

It is.

Standard early 4.5's wont rev beyond 6.8/7krpm as the hoses collapse though. We know as ours is (at our request) fuelled to 9krpm without a set rev-limiter... we wanted to work out why it always cut out at 6.8/7, now we have we'll have to get it re-adjusted.

Incidentally I dont believe alot of cars have a rev-limiter as such, they just run out of fuelling above 8krpm on the map, though im sure Trackcar once told me that for some bizarre reason they are mapped for fuel beyond 9k after that brief pause.... very odd, very TVR.