Bullshit BHP

[rev-erend]

Forums like this and others seemed to have run the good fight against the Bullst BHP figures manufactures seem to pass around .. and rolling roads have proved beyond a doubt what is real and what should remain on a marketing campain piece of paper only..

But don't you think it's like pushing against the tide or bailing out a sinking boat with a tea spoon.

Should those of us with cars with a higher state of tune than standard also 're-inflate' our bhp figures.

If so - what should the pub talk bhp be for .. say examples :

Griff 500 producing an actual 300 bhp .. ?

450 SEAC producing (an expected) 390bhp.. ?

Please feel free to add your car and real figures for other to decide on the talk bhp for you

[jammy_basturd]

For me peak BHP and torque figures are completely useless anyway. None of them tell you how quick a car moves, how well it brakes, or turns. Power figures should ALWAYS be quoted along with a mass figure for a start.

Personally if I was to try and convey how quick my car is in a straight line, I'd prefer to quote a 1/4 mile figure, as not only with this have some real world perspective, but it also takes into account how rubbish I am as a driver. No point in having 500 bananas under the throttle pedal but having the driving ability of a peice of soggy haddock.

[dbv8]

A rolling road recently told me i only had 330 bhp while on nitrous then i ran 11.6 @ 120 at the drag strip and an online calculator tells me i need 450 bhp in order to run such a 1/4 mile time. So its anybodys guess what power my car is producing.
I dont believe in bhp figures that people talk too much now.
But you cant argue with actual recorded figures at the drag strip.

[TVR_owner]

Sadly, the bullst starts when people quote flywheel BHP from a rolling road. Rear wheel BHP/tonne is the important one, not the big rather dubious number that ignores the fact that your car's is a lard arse....

Edited by TVR_owner on Thursday 10th September 14:19

[bobfather]

jammy_basturd said:

For me peak BHP and torque figures are completely useless anyway. None of them tell you how quick a car moves, how well it brakes, or turns. Power figures should ALWAYS be quoted along with a mass figure for a start.

Personally if I was to try and convey how quick my car is in a straight line, I'd prefer to quote a 1/4 mile figure, as not only with this have some real world perspective, but it also takes into account how rubbish I am as a driver. No point in having 500 bananas under the throttle pedal but having the driving ability of a peice of soggy haddock.

Someone talking sense here. People perceive the BHP results as a measure of performance and that's just wrong. Mass, chassis design, wheel alignment, tyre rigidity and adhesion, driver ability, LSD, flywheel weight, etc., etc. all need to be optimised to maximise the contribution that BHP provides.

Perhaps we need to encourage wheel alignment events, in my experience this can totally transform a car.

[ridds]

You ave to be fairly sharp to bullst your way past a VCA inspector on your Cert day.

Believe me Vehicle Dynos are a LONG way from accurate.

[900T-R]

ridds said:

You ave to be fairly sharp to bullst your way past a VCA inspector on your Cert day.

Believe me Vehicle Dynos are a LONG way from accurate.

Maybe, but we take all our road test cars to a rolling road here for a power/torque graph and every time it significantly differs from what the factory quotes, there has been something going on - from a lack of airflow to an unfortunately positioned intercooler to cars that came to us with erm, 'experimental' engine management versions with consumer mags having road tested the exact same car raving about how well it went for 'only' 150 bhp. Guess what subsequent cars delivered to actual customers made on the same RR - you got it, 150 bhp rather than 170...).

That is to say a RR that has been set up and is being operated by experienced engineers can be a consistent and trustworthy indication of real-world bhp and torque.

For the record, the German/Swiss 'certified' outputs for TVR RV8 engines are 228, 260 (IIRC) and 309 PS DIN for 400, 450 and 500 models respectively.

[s5tvr]

dbv8 said:

A rolling road recently told me i only had 330 bhp while on nitrous then i ran 11.6 @ 120 at the drag strip and an online calculator tells me i need 450 bhp in order to run such a 1/4 mile time. So its anybodys guess what power my car is producing.
I dont believe in bhp figures that people talk too much now.
But you cant argue with actual recorded figures at the drag strip.

Best dyno for real world results I've been on was TDI's at Lakeside. My car makes 311bhp at the hubs (hub dyno) and there's no way I could run an 11.6 1/4 mile. I reckon I could just dip under 12s. So your 330bhp at the wheels is maybe believable (I would say you have more) but 330bhp at the flywheel - forget it you must have way more especially as I would say my T350 is likely to put its power down better than your Chim ?

[ridds]

900T-R said:

ridds said:

You ave to be fairly sharp to bullst your way past a VCA inspector on your Cert day.

Believe me Vehicle Dynos are a LONG way from accurate.

Maybe, but we take all our road test cars to a rolling road here for a power/torque graph and every time it significantly differs from what the factory quotes, there has been something going on - from a lack of airflow to an unfortunately positioned intercooler to cars that came to us with erm, 'experimental' engine management versions with consumer mags having road tested the exact same car raving about how well it went for 'only' 150 bhp. Guess what subsequent cars delivered to actual customers made on the same RR - you got it, 150 bhp rather than 170...).

That is to say a RR that has been set up and is being operated by experienced engineers can be a consistent and trustworthy indication of real-world bhp and torque.

For the record, the German/Swiss 'certified' outputs for TVR RV8 engines are 228, 260 (IIRC) and 309 PS DIN for 400, 450 and 500 models respectively.

Still too many variables. Even on the Engine Dynos I've performed Engine Certification you have hundreds of factors that will alter your result.

Also, there is a big difference between a claimed output of an engine and what it will ever see in a car. Can you guarantee that you ambient air is 25°C, the humidity is at 35%, the baro is around 1010mBar? Just those 3 factors alone will ave a HUGE effect out your output, yes they can be corrected against but it's not perfect.

With Rolling roads you then have friction which will vary with temperature, type of oil used in transmissions, load applied through tie-down straps etc etc.

[dbv8]

s5tvr said:

dbv8 said:

A rolling road recently told me i only had 330 bhp while on nitrous then i ran 11.6 @ 120 at the drag strip and an online calculator tells me i need 450 bhp in order to run such a 1/4 mile time. So its anybodys guess what power my car is producing.
I dont believe in bhp figures that people talk too much now.
But you cant argue with actual recorded figures at the drag strip.

Best dyno for real world results I've been on was TDI's at Lakeside. My car makes 311bhp at the hubs (hub dyno) and there's no way I could run an 11.6 1/4 mile. I reckon I could just dip under 12s. So your 330bhp at the wheels is maybe believable (I would say you have more) but 330bhp at the flywheel - forget it you must have way more especially as I would say my T350 is likely to put its power down better than your Chim ?

I had 252 @ fly without gas then 330 with or 270@ wheels.
The power was down on the gas but i can believe the NA figure +/- 10 bhp.
I ran 13.3 @ 104 off gas for comparison.
The torque curve is interesting however when the nitrous was activated at 3000 rpm reaching nearly 390 lb/ft before something going wrong???.
Note red = NA and blue and green are on gas....

Edited by dbv8 on Thursday 10th September 16:28

[LordGrover]

Last year when my precat was top of the charts (BHP/litre) at the Growl the figures were accurate and a true reflection of my car.
This year as I came well down the list it's all just bluster and willy-waving.

[s5tvr]

ridds said:

900T-R said:

ridds said:

You ave to be fairly sharp to bullst your way past a VCA inspector on your Cert day.

Believe me Vehicle Dynos are a LONG way from accurate.

Maybe, but we take all our road test cars to a rolling road here for a power/torque graph and every time it significantly differs from what the factory quotes, there has been something going on - from a lack of airflow to an unfortunately positioned intercooler to cars that came to us with erm, 'experimental' engine management versions with consumer mags having road tested the exact same car raving about how well it went for 'only' 150 bhp. Guess what subsequent cars delivered to actual customers made on the same RR - you got it, 150 bhp rather than 170...).

That is to say a RR that has been set up and is being operated by experienced engineers can be a consistent and trustworthy indication of real-world bhp and torque.

For the record, the German/Swiss 'certified' outputs for TVR RV8 engines are 228, 260 (IIRC) and 309 PS DIN for 400, 450 and 500 models respectively.

Still too many variables. Even on the Engine Dynos I've performed Engine Certification you have hundreds of factors that will alter your result.

Also, there is a big difference between a claimed output of an engine and what it will ever see in a car. Can you guarantee that you ambient air is 25°C, the humidity is at 35%, the baro is around 1010mBar? Just those 3 factors alone will ave a HUGE effect out your output, yes they can be corrected against but it's not perfect.

With Rolling roads you then have friction which will vary with temperature, type of oil used in transmissions, load applied through tie-down straps etc etc.

All good points but an 11.6s 1/4 is simly (IMHO) not achievable in a 330bhp flywheel car. If I remember correctly Brummie in his LS Cerb is running 11.2's with not much short of 600bhp - correct me if i'm wrong on this.

As dbv8 said the maths would indicate that an 11.6s is only achievable with (ish) 450bhp. Either dbv8's car is making much much more than 333bhp or the 1/4 mile time is simply way off - my guess is the latter ?.

I have to say I do find an 11.6s 1/4 mile in a Chim a little bit hard to believe even if it is running nitrous - what would that give extra at the wheels ? - up to 100bhp say. A really good 500 Chim / Griff might put out 230bhp at the wheels, add 100bhp extra for the nitrous might give say 330bhp which to me doesn't seem compatible with an 11.6s 1/4 mile. 11.6s 1/4 mile times is what you would expect from an 500bhp Ultima not a nitrous'd Chim.

Edited by s5tvr on Thursday 10th September 16:33

[dbv8]

s5tvr said:

I have to say I do find an 11.6s 1/4 mile in a Chim a little bit hard to believe even if it is running nitrous - what would that give extra at the wheels ? - up to 100bhp say. A really good 500 Chim / Griff might put out 230bhp at the wheels, add 100bhp extra for the nitrous might give say 330bhp which to me doesn't seem compatible with an 11.6s 1/4 mile. 11.6s 1/4 mile times is what you would expect from an 500bhp Ultima not a nitrous'd Chim.

Edited by s5tvr on Thursday 10th September 16:33

Thats a ridiculous remark.
I run a Wizards of nos comprehensive kit jetted for 150bhp + 100bhp 2nd stage.
The 1/4 mile times were recorded properly at York and Shakey.
I have 2 11.6 runs at York, 1 with a terminal of 125 and ran 11.6 last Saturday and 11.8 last Sunday at Shakey... no argument
This is the 11.8 run.... http://www.youtube.com/watch?v=xPcGaJgySPs

Edited by dbv8 on Thursday 10th September 16:48

[spend]

Rather than arguing about calculations and simulations, why don't you delve into how they are made and what assumptions they make. Models are models whatever you do, you can spend hours refining them for accuracy but they can still only be used as a guide. As for dynos I agree with Ridds getting control conditions is almost impossible, even when you accept SAE and DIN run different tests and that the calc between bhp / KW / PS does not make them equivalent.

I know several areas which I have modified which will be absolute pants on a rolling road, but exactly the opposite on a real road.. Understanding what you are trying to achieve is often the hardest element of comparative testing?

[jammy_basturd]

It hasn't taken long for people to completely disregard mass again!

[FlipFlopGriff]

Have to agree with Derek (dbv8) as I was there watching. Can't imagine Shakey having dodgy timing devices given some of the machinery being worth millions and guys trying to shave 1/1000's of their times.
My best was 13.5 in a Griff 4.3BV. Probably crap but I couldn't get away. I'm sure I could get low 13's given a top start but need more practice and playing about with gear changes etc. Was R/R at 256bhp at the fly.
FFG

[s5tvr]

dbv8 said:

s5tvr said:

I have to say I do find an 11.6s 1/4 mile in a Chim a little bit hard to believe even if it is running nitrous - what would that give extra at the wheels ? - up to 100bhp say. A really good 500 Chim / Griff might put out 230bhp at the wheels, add 100bhp extra for the nitrous might give say 330bhp which to me doesn't seem compatible with an 11.6s 1/4 mile. 11.6s 1/4 mile times is what you would expect from an 500bhp Ultima not a nitrous'd Chim.

Edited by s5tvr on Thursday 10th September 16:33

Thats a ridiculous remark.
I run a Wizards of nos comprehensive kit jetted for 150bhp + 100bhp 2nd stage.
The 1/4 mile times were recorded properly at York and Shakey.
I have 2 11.6 runs at York, 1 with a terminal of 125 and ran 11.6 last Saturday and 11.8 last Sunday at Shakey... no argument
This is the 11.8 run.... http://www.youtube.com/watch?v=xPcGaJgySPs

Edited by dbv8 on Thursday 10th September 16:48

Not ridiculous at all. What are you saying your power is ?. If your saying your Chim is 332bhp with NOS as the dyno print out suggests (at the flywheel) then quite simply I find that hard to believe you're running 11.6s. There are a couple of Griffs out there that are similar power i.e. 330bhp ish (flywheel) and the fastest of them clocked just under 12.5s for the 1/4 mile at Fighting Torque this year. All I'm saying is that to me the numbers don't stack up - a 330bhp at the flywheel car does not run an 11.6s 1/4 mile - end of. A 330bhp at the wheels car would probably struggle to run an 11.6s.

[900T-R]

ridds said:

Just those 3 factors alone will ave a HUGE effect out your output, yes they can be corrected against but it's not perfect.

With Rolling roads you then have friction which will vary with temperature, type of oil used in transmissions, load applied through tie-down straps etc etc.

And IMO it's in the skill and experience in the folks who set the RR up and operate it how close to 'perfect' those corrections are. If, like us, you have put a hundred of new cars on the RR you soon learn to get a hunch for anomalies (& revisit your measurements where applicable).

Of course the real-world output will vary with ambient air temp, poressure & humidity and how hot things have gotten underbonnet - that's why the corrections are made to reflect the standardised values for which the outputs were claimed.

[spend]

jammy_basturd said:

It hasn't taken long for people to completely disregard mass again!

Why should mass be anymore important than several other factors eg. drag? that are not part of measuring power (which I understood this topic to be concerning).

[coetzeeh]

I thought torque was the main factor in accelerating a car, with big hp needed to punch at high speeds? (and no, anot an expert, just curious).