MPH per 1000 rpm

[bilton_d]

What is the correct speedo reading every 1000 RPM? my 4.5 with 17 inch alloys reads 26 mph every 1000rpm but i seem to recall reading somewhere it was supposed to be 29mph per 1000 rpm?

[VYT]

My 4.2 does 27 ish. I seem to remember the Chimaera T5 gearbox has a shorter 5th gear ratio than the Cerbera. 0.73 for the Cerb and 0.8 for the Chimaera. I wonder if we have Chimaera gearboxes fitted? I test drove a 4.5 that was similar before I bought my 4.2.

[exocet]

I get about 26 in my '96 4.2, and I think the speedo was fairly accurate when compared against a GPS.

Jo

[rolexblue]

Here we go



At 70mph my 4.5 on 18" wheels is spinning at 2700rpm which works out @ 26mph per 1000rpm.

Paul

[PaulK]

I have a 96 4.2 which returns 26 to 27mph per 1000rpm.
Dont know what the official figure is.

Paul

[Katanarog]

If you work out the circumference of a tyre. A 255/35 18 works out at 78.65 inches. Then multiply by gear and diff ratios one engine rev equals .36 of a wheel rev. ie 28.314 inches travelled for 1 engine rev.
multiply 60000 to get inches/hour at 1000 rpm 1698840 inches /hour = 26.8mph I think but Im shure youll know diffrent.(crap at maths)
Just a thought but maximum speed must be well short of 200mph as claimed by some?

[mudstud]

Just checked my 4.5 on 18"'s, 26.6 mph per 1000 rev's, if the rev limiter won't let you do above 7000 that puts top speed at 186.6, I'll just nip out and check that......maybe not tonight on account of a little ice about!

[Katanarog]

Thats what I thought why do the new speedos go up to 210 is it just bravardo?

[BCA]

From our RR print out we reckon 195 is on, and this is with an average 4.5 - Red Rose cars are a fair bit more powerful, they may well be able to push the double tonne.

[dannylt]

The limiter is not at 7000 rpm, think it might be around 7500, but don't remember hitting it. Certainly my Red Rose engine shows peak power at 7200. Think the buzzer comes on shortly after this.

danny

[rolexblue]

Hmm - according to my dealer the buzz comes on at 7000rpm (and it does) with the limiter set at 7800rpm which gives 202mph

Has anyone had theirs wound up in the 7000+rpm?

Paul

[dannylt]

Maybe your tacho wasn't very accurate. Since mine has peak power at 7200, I've clearly been above that on the dyno.

danny

[rolexblue]

dannyit - never had mine that far into the 7's, scared something might break! Curious whether anyone's seen 7400-7500, which would still give TVR's quoted top end.

Paul

[Katanarog]

Im sure my buzzer comes on @7000rpm but I must admit my eyes are more fixed on the road than the tacho. to get to 200 you would have to reach 7500conrod bending revs!