Possible Dyno Day@bhpTuner Leeds

[cragmaz]

I would love to see it tell me what my exact transmission losses are and convert my WHP to BHP.... I drive an auto !!!

There are lots of unbiased sites that tell you why a wheel dyno cant give an accurate crank figure, its just a guess, no matter what the marketing blurb says. The only way to get even close would be to take the engine out and run it on a calibrated engine dyno, put it back in the car and run it on a wheel dyno.... that would give you some indication but even that would not be totally accurate, it could not take into account even the smallest amount of tyre slippage.....

Im not knocking your dyno mate not at all, its just that people get a bit wrapped up in how accurate they are and they are not.... they are a VERY good comparison tool, and a useful diagnostic tool.

It would be interesting to know what Maha's limits of uncertainty are ? Bet they wont tell you that ? Also do they tell you what the dyno was calibrated against and what the limits of uncertainty where on that. Everything that is measured has limits of uncertainty, and these limits can be very large indeed, although thats generally kept a secret. I work in the measurement industry, you think a degree is a degree or a cm a cm it isnt and neither is a bhp a bhp, it all depends on the original calibration of the equipment. Very accurate calibration is also very very expensive and for most people totally unnessasary, a tape measure is not an accurate measure, its just a comparison tool and so long as you always use the same tape measure, you always get the same result, the same goes for anything that measures. Dont believe the hype. As I said Im not knocking your dyno I dont have a vested interest in it and would love to come and put my car on it with everyone else, so that I can COMPARE my car with others.

No offence intended and I hope none taken, just a wee insight into measuring stuff, I measure stuff all day long, the whole measurement industry is basically a con. Ok I need to run and hide now before they come and get me for revealing secrets lol.

(Draws Breath!!!!) Ok Buddy, i fully take on board your point, but in the dyno market, the machine is one, if not, THE best available, as accurate or in-accurate as it may be, some are more accurate than others, and you are very right, it is only as accurate as the calibration allows, this is a brand new machine and was only calibrated last month, so its as good as it gets, and is certainly the best in the region.

Anyway, i do hope you will come along when i sort a definate date, and get your motor on the rollers, i am certain that you ( and everyone else) will be suitably impressed.

will post a definate date next soon, just need to check schedule/work load etc, but will def be a sunday.

Everyone, please let me know if your interested tho, will need a min of 10 vehicles.

Cheers
Craig

[wegal]

I have my daughter every other weekend so if its not one of those weekends you can put me down.

[Alan M]

Hub Dynos are more accurate.

[straight5]

Talking as a someone who is a bit new to all this, I thought I would throw this question out there for some of those more knowledgable to educate me. (short words please haha), surely I need only really concern myself with the power as measured at the wheels. All I want to know is how much power am I getting down to the road. Everything else being lost in between is theoretical and not helping me in the real world. Is this right? I realise the loss between the two may be useful info if there is a problem, but otherwise its not really what I need to know.....is it???

[wegal]

Two schools of thought really, some people like to know the crank power so that they can say I have xxx horsepower vs xxx - transmission losses horsepower.

Even going on about BHP is a bit accademic. Torque is the important figure. BHP is a calculation of torque and revs. Torque is the bit that tells you how quick you accellerate, BHP is the bit that tells you how fast you will end up going.

Different cars and maps will give different results depending on what the driver is after, I want my car to accelerate through the gears quickly, so i want high torque, I dont care if it cant do the 175mph because i dont drive that fast anyway so BHP doesnt matter to me, its all in teh torques baby ;-)

The only number that really counts for my money is torque at the wheels, everything else is pretty much not relevent. But that is just my view, Im not saying this is the correct view, its just mine.

[irf]

horsepower for me.

as said above horsepower is a product of torque and revs. more torque over a wider rev range = more horsepower.

a peak torque figure at a certain rev point means nothing to me.

just two sides of the argument/debate

[cragmaz]

I have my daughter every other weekend so if its not one of those weekends you can put me down.

Cool, will keep you posted, will get a provisional date in the next week or so

Craig

[Alan M]

more torque over a wider rev range

This is where I see the power thing also. More torque over a larger range so you can really see/feel the difference while driving.

[wegal]

Agreed but if you have high and constant torque at the wheels then you have high BHP by default, sort the torque and the rest MUST follow.

Whereas you can increase your bhp figure by just revving the nuts off it, although there will come a point of peak bhp, after which torque drops off as revs increase. Torque in a usable and safe rev range or high bhp at mental revs ?

the rr day at awesome they pulled my runs at below 6000 rpm, but stll getting 300ft/lbs torque, but due to low rpm only 277 bhp. The torque figure is acceptable whereas the bhp figure appears low. Im not worrying about the bhp, cos the torque figure is ok.

I want more torque however .............. time to get out the wallet ;-)

[rimmer100]

I would be up for the rolling road day...

[Loadsamiles]

Dyno days are only really a bit of fun.

Far more interesting than standing in a freezing cold pub car park.

They are also excellent diagnostics tools. When there are other similar vehicles present it gives you a good opportunity to check if yours is up to spec with similar cars.

As for reliable BHP figures...... Forget it. As there is no independent calibration authority, or regulator of such activities it's all up to the owners and manufacturers to set a figure. All makes of dyno read different. If you are looking for a representative figure, get the operator to set the dyno to wheel horsepower mode, it's as close as you'll get.

If the will was there, there could be a calibration body. it's easy to do. just fit a known calibrated power source with rubber rollers (electric preferably) to the back of a transit like a spectacle lift, and drive round the UK sticking it on the various dynos testing them all.

All our measurement equipment at work has to be calibrated. Volt meters, sound level meters, etc etc. so why not dynos.

I'm sure many dyno operators would welcome such a system as it would stop all this ££££££.

Some people even end up deciding that it's easiest to dismiss all the higher figures and state that the one that reads the lowest must be correct. Where the probability is that some are low and some are high.

So the best idea is sod the definitive power figure idea. Treat it as a bit of a comparison, and an excellent chance for a bit of diagnostics.

[Wobbly Dave]

more torque over a wider rev range = more horsepower.

Wrong. Horsepower is a product of torque and revs (divide by 5252). Hence you create car like diesel that has the same horsepower at lower revs as a petrol would at higher revs - D5 vs VTEC is a good example.

Peak figures are just an indicator - and do not provide the full picture.

Torque provides the acceleration and horsepower gives you speed.

A long flat torque curve is desireable and it provides an indicator of good acceleration.

Precisely why this sums up irfs knowledge of the subject

a peak torque figure at a certain rev point means nothing to me.

But peak HP does?

Peak torque - is as its name suggests the point at which the turning force around the fulcrum (the crank/wheel hum) is at its greatest.

[Enigma666]

How is what Irf is saying irrelevent?
He basically said he is not interested in a huge torque figure across a narrow band as that achieves nothing.

Why is that an issue?

[irf]

i'm not gonna get into a stupid argument. you stick with your peak torque figures, i'll stick with peak horsepower.

oh by the way, not sure if you remember, it was a 280bhp volvo(mine) that overtook your car at marham last year when you used to claim 335bhp. no wonder you don't like peak horsepower figures

[Wobbly Dave]

Explain how you reach the conclusion and I will give your arguement some respect. The two sides are intrinsically linked. All you do by stick up this childish arguement is showing your grasp of these engineer concepts is clearly flawed.

http://www.largiader.com/articles/torque.html/

Stick with your peak horsepower?? - you mean the one point on the graph where mathematically the rpm multiplied by the torque is maximised. Please illuminate us all the meaning behing your powerful insight?

To increase horsepower - you can do 1 of 2 things - increase the RPM - with a constant torque OR increase the torque for a given RPM.

I also remember that I wasnt accelerating at the time - once you've done the runway at full tilt once or twice - I was trying to limit the wear on my engine.

[wegal]

Oh dear I can see this degenerating.....

basically peak anything is totally irrelevent, BHP increase comes from increased revs or increased torque at the same revs, The more torque you have over a given rev range the more BHP you end up with. An oil burner will generate loads of torque but at low rpm compared to most petrols so they can accellerate ( or pull heavy loads) very well, but they run out of revs so have a relatively low BHP figure for their torque figure.

Its not really worth arguing about to be honest, its just a case of what you look at on the graph BHP or Torque - like i said BHP is not relevent to how I drive so im not interested in it, im interested in torque, so if I increase my torque I do by default increase my BHP figure. I look for a high flat torque "curve" that holds through the rev range, if its starts dropping early then its indicative of the car running out of something ( fuel / air ) if it starts to late then its more likely a mapping issue, BHP line is pretty dull. It climbs as the revs climb to the peak figure, its fairly predicatable unless there is something wrong with the engine.

There is no right or wrong to this one, its really just a matter of personal choice. Im more impressede with a big torque figure that a big BHP figure, but like i said if they are just peak power then it doesnt mean a lot.

Now come on gents lets not get nasty with each other, there really is no need.

[straight5]

Spread the love. Lets see no squabbling. Thanks for all the useful info and opinions though guys. Although I aim to be at the RR, I will still probably mainly judge things using the highly calibrated and world respected seat of my pants.

[irf]

I also remember that I wasnt accelerating at the time - once you've done the runway at full tilt once or twice - I was trying to limit the wear on my engine.

lol, good one.

what i mean by peak horsepower is a good amount of torque over a wider rev range then a peak torque figure at a certain rpm point.

i won't be coming back to this argument, if it's not clear now it never will be.

[Loadsamiles]

horsepower for me.

as said above horsepower is a product of torque and revs. more torque over a wider rev range = more horsepower.

a peak torque figure at a certain rev point means nothing to me.

just two sides of the argument/debate

I'm completely lost on that one Irf......

More torque over wider revs doesn't mean more horsepower.

More torque at higher revs = more horsepower.

Horsepower isn't an averaged figure. It's an instantaneous figure at a said RPM . As has been explained.

The car could be coughing and spluttering it's way to 5,000 rpm generating almost no go whatsoever then come good by 5,500 kick into life and develop a stonking horsepower figure. for 1,000 rpm before running out of puff again. Utterly useless.


I agree More torque over a wider rev range = a better drive.

It's pointless arguing horsepower -v- torque as one being preferable to the other. They are one and the same. It's a simple mathematical relationship as one is derived from the other.

A cumulative figure WOULD be the best indicator of overall performance. But they don't give us one.

[irf]

thank you joules, that's explained it a bit better.

saying things like "childish argument" as dave said above just gets peoples backs up. it did mine.

it's easy to say things like that on a forum which is why i dont. would he come across like that in person? i'd hope not.

still think he's bitter for being overtaken by a 280bhp volvo