Discussion
Hello Folks,
This is a very old chestnut, I know, but how does TVR measure the power of their engines - particularly the Griff 500 rV8?
We all know that on a rolling road the power output (flywheel calculation) is likely to be well down on the 320/340 bhp that TVR claim, and the same is likely true of an engine dyno test, so how do TVR come up with the figures in the first place?
If the manufacturer stated power figure cannot be reproduced on a dyno, are we not being misled...?
This is a very old chestnut, I know, but how does TVR measure the power of their engines - particularly the Griff 500 rV8?
We all know that on a rolling road the power output (flywheel calculation) is likely to be well down on the 320/340 bhp that TVR claim, and the same is likely true of an engine dyno test, so how do TVR come up with the figures in the first place?
If the manufacturer stated power figure cannot be reproduced on a dyno, are we not being misled...?
1. TVR will clearly not measure the output of every engine they produce: they will have tested only a small number (possibly one 
).
2. Testing is likely to have taken place on an engine dyno, with no ancilliaries in the engine to sap power (and probably not with a full exhaust, restrictive air inlet etc.).
3. The engine that they choose to test could, if they wanted, be very close to ideal tolerances on all components.
4. All production engines will have a variety of mechanical tolerances that will cause the performance to deviate from the tested unit.
5. It doesn't matter at all: all the literature says you've got 320/340bhp for the necessary bragging rights down the pub, and the real world performance of the cars (acceleration, top speed) have been shown to be very close to the quoted figures.
It's a damn quick car, get out and drive it! 
Edited to add: this is no different from most other car manufacturers.
All IMHO etc., and I've no idea what actually goes on.
>> Edited by jeremyc on Thursday 21st August 11:23
). 2. Testing is likely to have taken place on an engine dyno, with no ancilliaries in the engine to sap power (and probably not with a full exhaust, restrictive air inlet etc.).
3. The engine that they choose to test could, if they wanted, be very close to ideal tolerances on all components.
4. All production engines will have a variety of mechanical tolerances that will cause the performance to deviate from the tested unit.
5. It doesn't matter at all: all the literature says you've got 320/340bhp for the necessary bragging rights down the pub, and the real world performance of the cars (acceleration, top speed) have been shown to be very close to the quoted figures.
It's a damn quick car, get out and drive it! Edited to add: this is no different from most other car manufacturers.
All IMHO etc., and I've no idea what actually goes on.
>> Edited by jeremyc on Thursday 21st August 11:23
To be fare to TVR, all manufacturers use bench dyno figures, this is measured without ancillaries giving a slightly higher figure.
TVR claim 320 lb ft of torque, most make around 300 or more on indipendent dyno's, bhp is a lot less than they claim but its the torque that gives the car "punch".
Tim
TVR claim 320 lb ft of torque, most make around 300 or more on indipendent dyno's, bhp is a lot less than they claim but its the torque that gives the car "punch".
Tim
OK, I get the gist - "it's a fast car, blah, blah..."
I totally agree with you. If I didn't then I wouldn't have bought a TVR. That's not the point.
Wishout intentionally wishing to dig up more fossils, there is a legitimate point about trade descriptions and whether TVR is "what it says on the tin", irrespective of timed performance measures.
I'm not planning to boycot TVR, or march up to PW and demand my 36k back (7 years later), but I am interested to know the extent to which car manufacturers (not just TVR) can do this.
Surely if the Vauxhall VX220 was stated at 400BHP we would be lining up in bigger numbers to have a go... and if TVR was stated at the more 'realistic' 270 BHP it would possibly not sell as many cars...
Believe me, I'm really not into "my co*k is bigger than your c#ck" discussions, but this is a valid consumer issue (christ, now I'm Ann Robinson).
If there's a thread on it, please point me there and I'll go away - couldn't find it on the forum search.
I totally agree with you. If I didn't then I wouldn't have bought a TVR. That's not the point.
Wishout intentionally wishing to dig up more fossils, there is a legitimate point about trade descriptions and whether TVR is "what it says on the tin", irrespective of timed performance measures.
I'm not planning to boycot TVR, or march up to PW and demand my 36k back (7 years later), but I am interested to know the extent to which car manufacturers (not just TVR) can do this.
Surely if the Vauxhall VX220 was stated at 400BHP we would be lining up in bigger numbers to have a go... and if TVR was stated at the more 'realistic' 270 BHP it would possibly not sell as many cars...
Believe me, I'm really not into "my co*k is bigger than your c#ck" discussions, but this is a valid consumer issue (christ, now I'm Ann Robinson).
If there's a thread on it, please point me there and I'll go away - couldn't find it on the forum search.
Sorry mate, wasn't trying to be sarcastic in a bad sense!
www.pistonheads.com/gassing/topic.asp?t=26759&f=13&h=0&hw=power+output+figures
is just one of the threads...
www.pistonheads.com/gassing/topic.asp?t=26759&f=13&h=0&hw=power+output+figures
is just one of the threads...
I typed in “Power” and “output” you could try other combinations, need I say more? Rich…
www.pistonheads.com/gassing/topic.asp?t=16723&f=9&h=0&hw=power+output
www.pistonheads.com/gassing/topic.asp?t=23947&f=9&h=0&hw=power+output
www.pistonheads.com/gassing/topic.asp?t=9923&f=9&h=0&hw=power+output
www.pistonheads.com/gassing/topic.asp?t=7858&f=9&h=0&hw=power+output
www.pistonheads.com/gassing/topic.asp?t=16723&f=9&h=0&hw=power+output
www.pistonheads.com/gassing/topic.asp?t=23947&f=9&h=0&hw=power+output
www.pistonheads.com/gassing/topic.asp?t=9923&f=9&h=0&hw=power+output
www.pistonheads.com/gassing/topic.asp?t=7858&f=9&h=0&hw=power+output
Marlon said:But thats the point: the only figure that TVR can quote is the one that their tested engine gave - 320bhp.
Surely if the Vauxhall VX220 was stated at 400BHP we would be lining up in bigger numbers to have a go... and if TVR was stated at the more 'realistic' 270 BHP it would possibly not sell as many cars...
Now it could be that Vauxhall are able to produce their engines with a smaller variation in power output than TVR, but no manufacturer is going to quote a range for their engines (Griffith: 280-350bhp
).Jeremy,
The Rover V8 is actually a pretty consistent motor from what I'm told - you certainly wouldn't expect a 30% variation... and most 500's are within 10 BHP of each other as standard, assuming no flaws elsewhere in the system (i.e. new).
Maybe I'm not making myself clear - the point is that on an engine dyno a typical TVR 5ltr rV8 will not produce 340 BHP, or as we would believe, not even close to it.
Thus, TVR are presenting an acurate (for 1 engine, heavily tweeked) but unrepresentative and unachievable performance figure that is used as a yardstick by most of the motoring world.
Accepted, the quoted performance figures of the car are on the whole indicative, but... oh I give up
enjoy your cars
The Rover V8 is actually a pretty consistent motor from what I'm told - you certainly wouldn't expect a 30% variation... and most 500's are within 10 BHP of each other as standard, assuming no flaws elsewhere in the system (i.e. new).
Maybe I'm not making myself clear - the point is that on an engine dyno a typical TVR 5ltr rV8 will not produce 340 BHP, or as we would believe, not even close to it.
Thus, TVR are presenting an acurate (for 1 engine, heavily tweeked) but unrepresentative and unachievable performance figure that is used as a yardstick by most of the motoring world.
Accepted, the quoted performance figures of the car are on the whole indicative, but... oh I give up
enjoy your cars
Marlon said:
Thus, TVR are presenting an acurate (for 1 engine, heavily tweeked) but unrepresentative and unachievable performance figure that is used as a yardstick by most of the motoring world.
We are all putting on our TVR-rose-tinted specs that allow us to forgive them anything, becasue we are fans of the breed. But Marlon has an entirely valid point. Let me take another, less emotive, example: you pay for a new TV which says it's 25" but then you find out it's only 21" - what would you do? Would you say 'It's a Sony so I don't really care'? Emotion aside, it's exactly the same debate. Trading standards, ASA, 'not as advertised', you name it.
But I'm still keeping mine!
Well before you disappear, you did say you'd drop the subject if we pointed you to the threads in the archives
So turning the question round, how do you find it? What did it give you on the rolling road? Who did you use for the work, where did you rolling road it etc. Rich...
Marlon said:Actually I didn't think that was what people said, in fact I thought the reverse, i.e. with no ancillaries etc. it could make 320/340bhp.
Maybe I'm not making myself clear - the point is that on an engine dyno a typical TVR 5ltr rV8 will not produce 340 BHP, or as we would believe, not even close to it.
Marlon said:Yours too, as I see from your profile and previous posts that you have done a whole bunch of modifications on it
enjoy your cars
So turning the question round, how do you find it? What did it give you on the rolling road? Who did you use for the work, where did you rolling road it etc. Rich... I understand that there are some fairly strict rules about how much horsepower can be claimed. But, there is plenty of scope for inflating the figures. For example, the power is quoted at standard temperature, pressure and humidity. Since it's normally measured under very different conditions, a correction factor is applied to show how much the engine *would have* produced under the standard conditions. The correction factor may not be totally accurate for your engine, so under some conditions it will overcorrect and some it will undercorrect. Test it under conditions where the correction factor overcorrects. Similarly, there's an allowance for rolling road inaccuracy. The rolling road has to be calibrated to within a certain error (which depends on the capacity of the road), but you can arrange that the error works in your favour. There's a restriction on the capacity of the rolling road versus the actual measured power, which limits the amount of error you can use in your favour (so you can't use a 1,000,000 bhp road and gain 1000 bhp). So you use the biggest rolling road you can get away with so you get the most error. All this is completely legal and above board, and is over and above any gains you might get by removing ancilliaries, using thinner oil, cheating on the engine spec, leaning on the dyno during the test, or simply lying and hoping nobody notices.
Thanks Rich,
I really must turn my attention to doing some work in a minute...
In fact, if you look through the other threads on this topic (as posted above) you will read that even on an engine dyno the rv8 will NOT (typicaly) make the claimed figures...
I had the P404 and ACT bits fitted by V8 Developments. They're a small outfit, but they clearly know what they are doing and are very helpful. I would recommend them.
The injectors were fitted at Power Engineering, where Mark Adams does much of his rolling road work (i.e. chip tuning). Again, they seem a good bunch of people and Mark rates the quality/calibration of their rolling road - so the figures will be quite accurate.
I'm more than pleased with the results! Throttle response is instant, it revs like a bugger right round past 6000 RPM, the low and mid-range torque will truly pin you back in your seat, and there's a great sound from the extra induction noise and chatter-chatter from the empty exhaust pipes!
It's been a progressive process taking a few months, so it's difficult to remember what the car was like before I started, but my brother (who has a chim 4.5, used to have a Fiat Coupe 20V Turbo, and had driven my Griff in the past) drove it at the weekend and as he returned brandishing keys proclaimed, "holy mother of christ etc etc... that's a bloody fast car". I think he was impressed!
Continued...
I really must turn my attention to doing some work in a minute...
In fact, if you look through the other threads on this topic (as posted above) you will read that even on an engine dyno the rv8 will NOT (typicaly) make the claimed figures...
I had the P404 and ACT bits fitted by V8 Developments. They're a small outfit, but they clearly know what they are doing and are very helpful. I would recommend them.
The injectors were fitted at Power Engineering, where Mark Adams does much of his rolling road work (i.e. chip tuning). Again, they seem a good bunch of people and Mark rates the quality/calibration of their rolling road - so the figures will be quite accurate.
I'm more than pleased with the results! Throttle response is instant, it revs like a bugger right round past 6000 RPM, the low and mid-range torque will truly pin you back in your seat, and there's a great sound from the extra induction noise and chatter-chatter from the empty exhaust pipes!
It's been a progressive process taking a few months, so it's difficult to remember what the car was like before I started, but my brother (who has a chim 4.5, used to have a Fiat Coupe 20V Turbo, and had driven my Griff in the past) drove it at the weekend and as he returned brandishing keys proclaimed, "holy mother of christ etc etc... that's a bloody fast car". I think he was impressed!
Continued...
Just to add my 2p to the 25" 21" TV comparison.
That is not a good example by any means. Physical differences like size would be like claiming a 0-60 of 4 seconds and a production car taking 6 seconds. If this were the case we would all (even those with rose tinted specs) be a bit annoyed I'll wager.
The facts of the cars performance are not in issue so I for one ignore all the stato guff apart from in the pub to shut some Porker owner up
That is not a good example by any means. Physical differences like size would be like claiming a 0-60 of 4 seconds and a production car taking 6 seconds. If this were the case we would all (even those with rose tinted specs) be a bit annoyed I'll wager.
The facts of the cars performance are not in issue so I for one ignore all the stato guff apart from in the pub to shut some Porker owner up
...
I still need to fit a few bits and bobs (possibly new airflow meter - waiting for some back to back test results conducted by Mark Adams this week) and an ACT hose from the airflow meter to air filter (mine's truly knackered), so not quite there yet...
The last rolling road session was a problem in that the ambient air temperature was almost 37C and the car was VERY hot - especially sucking air straight off the engine (no hose) - but from memory the figures were as folows -
Max power of 301 BHP at 5,750 RPM
Max torque of 334 Lb/Ft at 3,000 RPM.
Torque is the big win; 300+ Lb/Ft from 2,000 RPM right through to 5,500 RPM, with 330+ between 3,000 and 4,000
With the new air hose and a cooler day I should expect to see around 310 BHP and 340 Lb/Ft.
I still need to fit a few bits and bobs (possibly new airflow meter - waiting for some back to back test results conducted by Mark Adams this week) and an ACT hose from the airflow meter to air filter (mine's truly knackered), so not quite there yet...
The last rolling road session was a problem in that the ambient air temperature was almost 37C and the car was VERY hot - especially sucking air straight off the engine (no hose) - but from memory the figures were as folows -
Max power of 301 BHP at 5,750 RPM
Max torque of 334 Lb/Ft at 3,000 RPM.
Torque is the big win; 300+ Lb/Ft from 2,000 RPM right through to 5,500 RPM, with 330+ between 3,000 and 4,000
With the new air hose and a cooler day I should expect to see around 310 BHP and 340 Lb/Ft.
I was just curious to see what you got because I have similar mods on my car without the pre-cats out. Also I know my tappets are way off 
so next job is to get the tappets done, change the exhaust headers for cat-less ones and get it back to see Mark at P'Eng. I am also thinking I can improve the air intake for better breating. There are some pic's on www.greenbear.org.uk see under Griff 500/modifications
Rich...
so next job is to get the tappets done, change the exhaust headers for cat-less ones and get it back to see Mark at P'Eng. I am also thinking I can improve the air intake for better breating. There are some pic's on www.greenbear.org.uk see under Griff 500/modifications Rich...
jamesk said:
... in the pub to shut some Porker owner up
["History Today" mode]
PO: Today on History Today we have Sir James K Grubbly-Sphincter, Emeritus professor of 20th century transportation at Wheeler College, Cambridge. Good Evening professor.
JK: Good evening
PO: I wonder if we could start....
JK: You see that barge going down the river?
PO: I am acquainted, yes
JK: That's your Porker that is! See that challenger rocket?
PO: Well, I may be familiar with the concept.
JK: That's MY car, that is
PO: Well I.....
JK: You just go down the Kings Road posing like a .......
[/"History Today" mode]
...you get the drift
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