Top Speed?

[DustyC]

Someone* told me that in 5th gear;

4000 RPM = 120MPH
4800 RPM = 140MPH

So what does 6000RPM equal and is it reachable in top gear?

* To the tune of Cococapana
(Her name was Griffith,
she was a sportscar,
pretty colours everywhere,
dirty growl came from the rear.....)

[deeen]

according to my calculator

if 4000=120, 6000=180

and if 4800=140, 6000=175

as to rev limit, i thought it was sposed to be 6250.

My standard chim 500 seems to hit the limiter around 6200 and seems to be geared for around 165 in 5th at those revs.

one way to check yours is drive at 3000 rpm in top, note the speed, then double it to find out what you would be doing at 6000. Allowing for the usual seedo error, of course.

[angusfaldo]

Right - just been out to test this

Well at 3100 rpm in top my road angel reads 83mph.

So with the 500 allegedly limited to 6200 that would tell you that in theory, it will do 166 in top gear.

[angusfaldo]

Also interesting to note that the speedo does, quite significantly, over read.

[DustyC]

My limiter is at about 6200-6300 too.
Hitting it at top speed wouldnt be nice though!

My speedo is 12% out at 100MPH

Im sure that your 3000RPM test in top gear wont make calculating top speed possible. What about drag? Surely that will have a counter effect. Also is it a linear curve? I wouldnt have thought so.

(If this post comes across in a growling manner it wasnt written with such intent!)

[deeen]

DustyC said:

My limiter is at about 6200-6300 too. Hitting it at top speed wouldnt be nice though! My speedo is 12% out at 100MPH Im sure that your 3000RPM test in top gear wont make calculating top speed possible. What about drag? Surely that will have a counter effect. Also is it a linear curve? I wouldnt have thought so. (If this post comes across in a growling manner it wasnt written with such intent!)

All my "3000 rpm test" means is that IF your car will pull 6000 in top, the actual speed WILL be exactly twice that at 3000rpm, cos there's a mechanical connection between the crankshaft and the back wheels, and ye cannae change the laws of physics, captain!

Other factors (drag, friction, brown trousers, etc) will affect the car's ability to reach those revs in top gear, but if it can do it, the relationship between revs and speed in any given gear should be a straight line.

Unless your clutch is slipping or you have an automatic (?!) and ignoring the tiny effect of the diameter of the tyres increasing at speed, and other miniscule things which some edantic ugger will think of later.

All growls assumed to have come from rear of Griff, btw!

Oh yeah and the speedo error may not be linear either...






>> Edited by deeen on Thursday 20th May 09:38

[Painey]

My speedo doesn't seem to overead by too much although judging by how "different" all TVR's can be maybe I just got lucky? The reason I know it doesn't overead too much is I've had a verified 164mph out of it and the speedo was reading just over 170 at the time. I think unless you've done something to the engine you're unlikely to hit the limiter in fifth.

All the best - Chris

forgot to add that the rev counter was just below 6000 rpm at the time!

>> Edited by Painey on Thursday 20th May 11:25

[Nano2nd]

worked mine out using a calculator the chim is slightly higher geared with the 225's on these are the figures..

223.49 @ 8000rpm

195.55 @ 7000rpm

167.62 @ 6000rpm

be nice if it would rev to 7500!

[deeen]

mine has 225 on the FRONT, 245 on back... you havent got a front wheel drive chim, have you?

[donatien]

I've said this before but at 6200 RPM a standard 500 will be well down on its peak power as the power curve dips drastically. If you can pull to the limit in 5th then taller gearing *may* get you a higher top speed.

Dave

[pete]

My 500 is putting out a shade under 240bhp at 6,400rpm on Austec's rolling road, from a peak of 275ish at 5,300rpm. It's also down to only 200lb.ft of torque at 6,400.

Based on the fact that it reached 6,400 without hitting the limiter, it seems more certain that aerodynamics are the limit for my car. Guess it depends where your limiter is set.

Pete

[Nano2nd]

deeen said:

mine has 225 on the FRONT, 245 on back... you havent got a front wheel drive chim, have you?

chim 450 has 225 rears and 215 fronts

[Nano2nd]

here are the figures with 245/45 section tyres

166.33mph @6000prm

194.05pph @7000rpm

as you can see theres not much in it but the 225 tyres give slightly higher gearing

[Nano2nd]

by my calculatons a griff 500 that would hit the limiter in 5th (6250) would be doing 173.16mph

obviously not included the variables already mentioned.

[kevinday]

Ignoring all the technical talk, a Griff 500 will reach about 160mph +/- 5%. The major variables are the real power output of the engine and whether the top is up or down.

[DustyC]

kevinday said:

Ignoring all the technical talk, a Griff 500 will reach about 160mph +/- 5%.

But thats no fun is it! You need to use the rev figures and then argue!

[deeen]

kevinday said:

Ignoring all the technical talk, a Griff 500 will reach about 160mph +/- 5%. The major variables are the real power output of the engine and whether the top is up or down.

and where the speed cameras are!

[bensandars]

On a recent trip, I had between 160 & 170 on the clock (ego-meter), and these tied in with my friend who was in a DB7, previously, I have had a GPS and speed around 100 seemed to be consistant with the speedo.


P.s my limiter seems to cut in around 6350 -6400 rpm

[DustyC]

did you really take a picture at that speed?

[bensandars]

She sits really nicely at that speed on the French motorways at between 120 -160 in fact, I must have covered the majority of the 800 mile journey at that speed in my dash back to the ferry after leaving Cannes 8 hours late....