28mph for 1000rpm
Discussion
Read this somewhere on a recent thread and checked out theory on my Chimaera 500 (altho assume its all about gearbox ratios and not engine cc) It is 2002 version by the way.
Now I'm worried as my speedo and rev counter exactly reflect this, ie:
in 5th gear 2000 revs = 56mph, 3000 = 84mph, 4000 = 112mph, didn't go past this.
I had assumed that speedo would be overstating as every one elses seems to do and even at a reading of 95mph I still get lots of cars passing me (who I guessed were doing 85ish)
What do you think, am I the only TVR in the country with an accurate speedo??
David
Now I'm worried as my speedo and rev counter exactly reflect this, ie:
in 5th gear 2000 revs = 56mph, 3000 = 84mph, 4000 = 112mph, didn't go past this.
I had assumed that speedo would be overstating as every one elses seems to do and even at a reading of 95mph I still get lots of cars passing me (who I guessed were doing 85ish)
What do you think, am I the only TVR in the country with an accurate speedo??
David
ATG said: Mine agrees with a GPS to within the accuracy of the speedo dial ... plus/minus a couple of mph at worst.
I agree, 140 on the speedo showed a max speed recorded on the gps of 139 in my Griff 4.3, dunno what the revs were, was busy looking mostly at the road - seems there's a few accurate ones out there!
No most of them are accurate. Most people don't post saying "my car does this correctly" so you can get a totally skewed vision of things by just looking here. The early cars were not due to component changes and tyre changes which affects the readings. There's a spread sheet on my website that can calculate these figures and the figures for the common tyre sizes and bigger wheels is in the Bible 2nd ed.
Steve
www.tvrbooks.co.uk
Steve
www.tvrbooks.co.uk
Tony Hall said: 95 4.0HC , my speedo reads around 66 to 68mph at 2000rpm. Always assumed it was reasonably accurate, now i'm not so sure!
WOW! So at a liesurely 4000rpm you're doing about 134mph and maxing out at say, 5500rpm means a top whack of over 180mph. Not bad for a 4.0. I think you should make some adjustment - or allowance here.
JamieBeeston said: 3000 in 5th is 80 on my speedo, dead on, 98 Chim
they tested against rolling road and found it to be ~10% out all over the range,
so assume 70-72ish at 3000 rpm REAL SPEEDS
Jamie - NO! unless your tacho is way out? As I mentioned in another thread (from Autocar road test) standard car is around 28mph/1000rpm. So at 3k it should read 84 + 10% error allowance, so anywhere up to 92 is acceptable.
the dodger said:
Jamie - NO! unless your tacho is way out? As I mentioned in another thread (from Autocar road test) standard car is around 28mph/1000rpm. So at 3k it should read 84 + 10% error allowance, so anywhere up to 92 is acceptable.
Dead on 80 Dead on 3000 rpm, dead on 100 dead on 4000 rpm,
dead on 500rpm for 10mph on mine,
spent about 8 hrs on the dyno over the last few mths, so assume the tacho is spot on, else it woulda been spotted..
Asked them to check the speedo whilst on the dyno, and that was their findingd, approx 10% out all the way thru,
60 read 54, 100 read as 90 etc..
>> Edited by JamieBeeston on Wednesday 8th January 23:17
-Quite obvious your speedo has a problem here Jamie. 80mph at 3k = 26.6 mph/1000. 90mph at 4k = 22.5 mph/1000. Either you have a variable rate diff or there's a problem with your tacho/speedo. 
it = 500rpm per 10 mph in 5th, nice and uniform all the way thru 5th gear,
like i say, I aint worried, i KNOW its fine, they tested it AT MY REQUEST on the rolling road all thru the range, every point they tested it at, it was nigh on 10% out..
Good enough for me..
now i know i can add 10% before i come close to ACPO Guideline allowances
>> Edited by JamieBeeston on Wednesday 8th January 18:11
like i say, I aint worried, i KNOW its fine, they tested it AT MY REQUEST on the rolling road all thru the range, every point they tested it at, it was nigh on 10% out..
Good enough for me..
now i know i can add 10% before i come close to ACPO Guideline allowances
>> Edited by JamieBeeston on Wednesday 8th January 18:11
Jamie, I don't want to labour on this because it's not that important. If you're happy that's fine. But if you think it's 500rpm for every 10mph then at 3000rpm you would be doing 60mph, at 4000 = 80mph and we all know that ain't right. Agree? I am just going by the Autocar road test data which actually states 27.5mph/1000rpm in top. This was for a standard 4.0L but I don't think they changed the cwp ratio on other engine variants. I haven't looked in the Gospel acc. to St. Heath yet either. Have fun anyhow. May see you at Forresters this Sunday if I can make it.
JamieBeeston said:
Dead on 80 Dead on 3000 rpm, dead on 90 dead on 4000 rpm,
dead on 500rpm for 10mph on mine,
Jamie, I'm no TVR owner or driver, but that just don't make sense mate!
If 3000rpm is 80mph, and you add 10mph for every 500rpm then 4000rpm would be 100mph not 90!
I think it's a case of you know what your talking about, but what you wrote is complete b*ll*ks
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