Overinflated TVR Topspeeds
Discussion
I alway thought the Top Speeds on a Griffs or Chim500's at 167mph were a bit exaggerated.
Just done some basic calculations. Knowing that really pulling more than 5600 in the gears is a waste of time and wearing the engine out and prolonged 5600 - 6000 (max recommended revs - I think the limiter is about 6100ish - not found it in current one as pointless).
Rear Wheel circumference on a 245/45x16 is 77.5"
Diff Ratio = 3.45:1
5th Gear ratio is 0.8
Doing the numbers 6000 in top is 160 mph.
6500 in top is 172 mph
so the TVR 167 mph would be at ~ 6300revs.
1) I think the (RV8 in std spec - no fancy rods, pistons, cranks or end bolts) engine would grenade itself at these speeds.
2) the Torque and Power curves are way past their peaks even if these revs did not result in the Big Bang.
3) not enough Power or Torque to overcome the brick wall aerodynamics at these speeds (massive windscreen etc).
The above is not so likely to be the case for the higher rev'ing later TVR engined cars the engines being able to pull safely the revs needed for their claimed Top Speeds.
Just done some basic calculations. Knowing that really pulling more than 5600 in the gears is a waste of time and wearing the engine out and prolonged 5600 - 6000 (max recommended revs - I think the limiter is about 6100ish - not found it in current one as pointless).
Rear Wheel circumference on a 245/45x16 is 77.5"
Diff Ratio = 3.45:1
5th Gear ratio is 0.8
Doing the numbers 6000 in top is 160 mph.
6500 in top is 172 mph
so the TVR 167 mph would be at ~ 6300revs.
1) I think the (RV8 in std spec - no fancy rods, pistons, cranks or end bolts) engine would grenade itself at these speeds.
2) the Torque and Power curves are way past their peaks even if these revs did not result in the Big Bang.
3) not enough Power or Torque to overcome the brick wall aerodynamics at these speeds (massive windscreen etc).
The above is not so likely to be the case for the higher rev'ing later TVR engined cars the engines being able to pull safely the revs needed for their claimed Top Speeds.
PetrolTed said:
I've seen friends either doing or with SatNav evidence of 155mph in the ex-press Chim 450 and 195 in Cerberas.
The problem is at anything over 140ish, the roof would lift so far off the window that you were sure it would pop off at any moment, and there is no way you are getting those speeds with the Roof in Targa mode.. tho I suppose you could try full down, but I never liked the loss of Rear View with that.
Could be just that my roof wasnt a good fit, but I('ve been told you) would see a 1-1.5inch gap between the top of the window and the roof at speeds.
Just waiting for the - I have seen type lines.
And the sat nav ones Ted. 195 in a Cerb (with <400bhp) - 185 maybe.
I recon a Griff might see just over 160 and a Chim about that if the roof could be kept on.
Can't see the Top speed attraction. What would a hard top do to a car following at those speeds!
And the sat nav ones Ted. 195 in a Cerb (with <400bhp) - 185 maybe.
I recon a Griff might see just over 160 and a Chim about that if the roof could be kept on.
Can't see the Top speed attraction. What would a hard top do to a car following at those speeds!
I thought the T5 ratios were final = 3.31 and 5th = 0.73. Of course, I could be wrong...
Our Griff 500 manages 4750 in 5th easily but the rear screen goes through it a bit. I estimate that it'll be all done at 5500 rpm. (about 170) so the quoted top speed isn't that far out assuming the ratio info I've got is correct.
Our Griff 500 manages 4750 in 5th easily but the rear screen goes through it a bit. I estimate that it'll be all done at 5500 rpm. (about 170) so the quoted top speed isn't that far out assuming the ratio info I've got is correct.
The book and few sight I have checked are saying 5th = 0.8 (which is pretty common).
Speed do reading are usually up to or even over +5% at these speed. Maybe TVR just print what some one once saw on the counter. You can tweek the output from the diff to the ecu and the speedo to make them read what ever you want - have had to research all this for the LS6 (which has a true red line - actually an ecu programmed fuel cutout at 6600) - about 174.5mph. But I won't be verifying it.
Speed do reading are usually up to or even over +5% at these speed. Maybe TVR just print what some one once saw on the counter. You can tweek the output from the diff to the ecu and the speedo to make them read what ever you want - have had to research all this for the LS6 (which has a true red line - actually an ecu programmed fuel cutout at 6600) - about 174.5mph. But I won't be verifying it.
Who cares?...I certainley dont! 
Seen a picture of a GPS verified 200MPH from a Cerbera 4.5 (standard). Also seen a GPS verified 147MPH from a 4.0HC Chimaera. So not far off...
Dont actually care really. Top speed is so subjective anyway - I mean given a long enough road, the majority of cars will break their TS anyway. The problem is that almost all of us dont have access to such roads and therefore doesnt really matter.
Dont actually care really. Top speed is so subjective anyway - I mean given a long enough road, the majority of cars will break their TS anyway. The problem is that almost all of us dont have access to such roads and therefore doesnt really matter.
Paddy - I don't really give a Rats either, especially top end.
I almost went down the RX7 route and got as far as working out th numbers on a Petit Banzai - (would give a Mclaren F1 a good run.
www.pettitracing.com/rx7/index.htm - Banzai
I almost went down the RX7 route and got as far as working out th numbers on a Petit Banzai - (would give a Mclaren F1 a good run.
www.pettitracing.com/rx7/index.htm - Banzai
if you use the correct 3.31 diff ratio that gives you 166.4 @ 6000rpm so assuming your 6100 rev limit then 167mph is not bad... however at that sorta speed the tyres will have expanded a good deal so your could be going even faster 
i've been in a griff 500 at bunters with the speedo showing 171 with the roof on flat out.... the same car did an indicated 165 with the roof off! damn it was noisey lol
just as a foot note if you could get the engine to rev to 7000rpm your would be doing 194 (without the tyre expansion) and to crack 200 you would need a rev limit of 7250
personaly i think top speed is cool
i've been in a griff 500 at bunters with the speedo showing 171 with the roof on flat out.... the same car did an indicated 165 with the roof off! damn it was noisey lol
just as a foot note if you could get the engine to rev to 7000rpm your would be doing 194 (without the tyre expansion) and to crack 200 you would need a rev limit of 7250
personaly i think top speed is cool
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