[GTT 280]

Hi all,

Can anybody tell me what the typical %loss is in BHP between the flywheel and the wheel?

Can anybody tell me how an exedy clutch, lightweight flywheel, lighter crank pulley, and 7kg O.Z. Superleggera wheels will have on this figure?

Cheers,
K.

[Paul Webster]

Karl,

The easisest answer is to pop down and we'll measure it

We have seen a low of 28bhp and a high of 40bhp with most Cooper S in the mid 30s.

This is why I personally am more focussed on whp because if you and your car weigh the same as mine and we're going at it down the back straight at Donny you should in theory out run me if you have the 28bhp loss and I've got the 40bhp loss.

The only way to find out is by going to a local rolling road just make sure you or they have the capibility to measure the IAT and that the fan is good enough to keep the IAT low. If they or you can measure to record the ignition timing even better.

It will also give you a chance to play around with your fpr as well to see what difference it makes but obviously this will change a bit on the road as well, so if you have thefacility to record afr even better.

A member of the Old Skool Ford forum recently had an engine dyno'd on an engine dyno put it in his car that night then went to 3 differnt rolling roads the next day and some of them were within 3 bhp if my memory is right an there was one way off the mark.

We could do this ourselves but the costing would probably be about £1000-£1500 due to the inital set up time, electronics bellhousing flywheel engine mountings etc etc. But once that is done you could dyno any S engine on that engine dyno for about £500.

Hope this helps

[GTT 280]

...can you not derive a 95% true BHP based on the drag detected on the rundown after the acceleration on a RR? The quicker the rollers stop, the higher the HP loss between the fly and road? - i guess the engine/scharger would impose some drag on that too, or do you release the clutch?

Cheers,
K.

[roland2003]

I and nearly every tuner worldwide outside the US (and all car manufacturs) disagree with the above .
Karl.....Dig out the 'Wheel Horsepower v Flywheel Horsepower 'thread . I explain it all in great detail there,and why WHP is meaningless as a 'quotable figure'. WHP is only any use as part of the equation to give a flywheel figure, after the losses have mean measured aswell. (not a correction factor) . You then have a Flywheel figure that 'should' be able to be used as some sort of comparison between cars. There is no guessing with Flywheel power...it is WHP that is guessing how much the engine is losing. Its a good thread check it out,

[GTT 280]

Hi Roland.

Was confused for a moment there, when you say "above" you actually mean the post from 1320 (that's not a dig at you 1320 ). So my understanding that the negative bhp being measured to calculate a 'quite accurate' engine BHP is correct, although you shouldn't disengage the clutch as i first thought.

Your thread (that i have read before ) makes perfect sense - and is based on common sense i guess.

In a real world environment it's almost impossible to get a scientifically exact BHP reading, but remaining consistent with the variables on offer should provide a 'quite' reliable and comparable BHP figure (WHP + "negative" bhp).

Problem is, everyone does these things differently, and often with non standard components fitted to the vehicle - wheels, tyres, flywheels etc. etc. with different ambient conditions, air temp, humidity, height above sea level etc. etc. fuel etc. RR equipment etc. etc.

I think the best and easiest judgement is to 'feel' how fast the car is compared to other cars - on the road, and in the open air. For example, if Lambourghini spent £00000's approving their power ratings, and i can keep neck and neck with them (that still makes me grin big time ), then whether a RR tells me i have 250, 260, or 270 doesn't really bother me too much. It feels fast, is fast, and keeps up with other things that are fast

Still, RR's are good for the layman and for pubs and i suppose if done well (with neg bhp) could be considered good reflection on your cars true performance.

Guessing the drag between flywheel and tarmac is crazy, and relying on a WHP can't highlight any issues in problems between flywheel and tarmac. What if the wheel HP was 250, and the fly HP was 400, would you ever know you were loosing 150 HP in the drive train somewhere if you never measured the neg HP? (excessive example i know, but could you?)

Well, looks like i've just started to repeat your thread Roland, so i'll cut it short here.

I think i have an answer to my original question though.....

There is no typical loss of bhp between fly and tarmac, and
Factors like a lightweight flywheel, lighter wheels should result in a higher WHP but have no effect on the engines BHP.

...and here is Rolands original thread for those who are intrested in the finer details:


Cheers,
K.

[KPKalle]

Hey guys can we just agree to differ on this please? I'm not remotely technical so have no idea about all this but this is turning into a cat fight. Thanks

[chrisflyer]

Well

Please excuse any spelling errors,
Both using BHP and WHP have there merits, BHP engine output and wheel horse power the amount of power you can put down on the road. Maybe both should be used.
Also there are some good explanations on the world wide web.
But is not the real mark of a cars speed the amount of torque produced and at what revs.
because this is what makes it accelorate fast.

[Paul Webster]

If you look at any heads up class in drag racing like comp eliminator you will see that a manual car has to carry 200lbs more weight than its identical twin automatic car due to it loosing more horsepower between the flywheel and wheels.

So if we had two identical weighted GTT260 cars and one was running a normal manual trans and the other one Roland had blueprinted to have as less horspower robbing drag as humanly possible which one would everyone want to take round the track.

[sam_a156]

Quote: Originally Posted by GTT 270 (original)

Flywheel BHP > Wheel BHP

Hi all,

Can anybody tell me what the typical %loss is in BHP between the flywheel and the wheel?

I was always wondering what this English language expression about "opening a can of worms" was all about. Got it now...

[GTT 280]

OK guys, lets cool it.

This is another boxing thread. Lets not cause trouble for trouble sake. If we have comments to make, lets keep them constructive, not destructive.

It's difficult when we are so passionate about the topic, i know. I think we all have good points to make, but lets keep the sarcasm for elsewhere, it acheives nothing - as i have learnt already.

We all have our own opinion, right or wrong.

...let's not forget the experience Roland is bringing to MINI2 - he has been in the modifying business for many many years now (GT5 etc) and he does have some excellent drivers on his team... F1 etc. I don't think he could have designed, manufactured, tested, and produced a 391BHP turbo R53 (with endless components) if he couldn't even grasp the concept of the Rolling Road theory.

Cheers,
Karl.

[Tüls]

Quote: Originally Posted by 1320autos (original)

If you look at any heads up class in drag racing like comp eliminator you will see that a manual car has to carry 200lbs more weight than its identical twin automatic car due to it loosing more horsepower between the flywheel and wheels.

So if we had two identical weighted GTT260 cars and one was running a normal manual trans and the other one Roland had blueprinted to have as less horspower robbing drag as humanly possible which one would everyone want to take round the track.

this is it right there.... everytime I am talking to a real racer/tuner I use WHP... cuase if I say... 450 BHP or 450 HP they always ask.. whats it make at the wheels?.... why.. cuase when it's time to race.. that's what matters..

what's funny is there are plenty of MINI tuners here in the states who use BHP.. so they can sell the kits... people strap them on and never ask... but when taken to the track or the dyno... a car that had 328 BHP only came out at 230 WHP.... both on the dyno and the drag... hmmn something didn't add up... I am gunnah say it was the tuners claim... but hey.. he's selling kits to the ignorant!

when it's time to brag.. it's BHP... for instance... all the merican muscle car guys... they tend to be a few 100 years behind the turners.. and all they know is HP... so I say.. 450 HP.. they go... oooOOOOooo... if I said 400 would they oooOOOoo, sure... cause it's a mini, but when I say wheels they dont get it.. all they know is (use american country voice here) my corvette sayays 500 hers powr in the fakteree manyull so it be thayat

Edit: IMO
I may not be the brightest tool in the box. God knows just since I was born on soild "accross the pond" I am counted as having a lower IQ...

however,

Using a Chassis Dyno to figure out Engine HP is like using an Engine dyno to guess wheel HP when you dont even have the car yet... LOL

next thing you know I am gunnah be told to go see a proctologist for brain surgery!

[GTT 280]

Quote: Originally Posted by Tüls (original)

this is it right there.... everytime I am talking to a real racer/tuner I use WHP... cuase if I say... 450 BHP or 450 HP they always ask.. whats it make at the wheels?.... why.. cuase when it's time to race.. that's what matters..

I agree that the WHP is ultimately the power that you get to enjoy on the road and is very important, but if you are trying to determine how powerful your engine is, then i still understand the Flywheel HP to be the better reading as it removes the problems encountered in all the moving parts between flywheel and roller - which can be quite different (tyre pressure, wheels, diff, gearbox, bearings, oil, dust etc)

WHP alone will not highlight the power lost in the drive train. You need to record the Drag HP on rundown to determine this.

I think both readings are equally important allowing you to determine the drag factor of the drive train, which is what my thread was all about.... determining if my lightweight flywheel and lightweight wheels generated a higher WHP (assuming the engine BHP remained the same).

Now, i don't quite know if the flywheel is included in the engine BHP or not, as this would effect the BHP and not the WHP (but ultimately the WHP too but not as 'drag factor')

I suppose the only actual figures are Wheel HP and Drag HP... adding these together provides you with the derived Engine HP (or BHP).

If you want to use BHP or WHP is personal preference, and seems to be the issue at hand between UK and US.

Cheers,
K.

[Tüls]

Where I am confused is why does the drive train loss matter? It is what it is... If you measure WHP... then you know making X... and your car weighs Y... you can then know how fast it is... with BHP you can only guess and hope.

Another example is if you are making 200 WHP and weigh 2500 lbs you know you can probably do really well against a car that's making 300+ BHP and weighing 4000 lbs especially cause you know that chances are they aren't making 300 WHP...

Thanks for explaining yer interest in BHP... for me when I buy a kit... or performance part.. I wanna know what my real world usable power is... cause in the end.. if it's a 5 bhp gain.. let's be honest.. it's virtually nothing at the ground! LOL

Quote: Originally Posted by GTT 270 (original)

I agree that the WHP is ultimately the power that you get to enjoy on the road, but if you are trying to determine how powerful your engine is, then i still understand the Flywheel HP to be the better reading, simply because the WHP will not highlight the power lost in the drive train.

I think both readings are equally important, one without the other won't allow you to determine the drag factor of the drive train, which is what my thread was all about.... determining if my lightweight flywheel and lightweight wheels generated a higher WHP (assuming the engine BHP remained the same).

Now, i don't quite know if the flywheel is included in the engine BHP or not, as this would effect the BHP and not the WHP (but ultimately the WHP too but not as 'drag factor')

Cheers,
K.

[MiniIndy]

BHP may as well be a guess without the motor being on an engine dyno. At least WHP can be tested or calculated by strip times & vehicle weight. IMO, the more realistic value is the one you can more positively measure and not calculate.

[GTT 280]

Quote: Originally Posted by MiniIndy (original)

BHP may as well be a guess without the motor being on an engine dyno. At least WHP can be tested or calculated by strip times & vehicle weight. IMO, the more realistic value is the one you can more positively measure and not calculate.

Like i say, each to their own. I suggest you read this thread and the linked thread in more detail first. You don't offer much of a justification for your decision.

If you can measure Wheel HP, and you can measure Drag HP, then you have BHP

Unless we are all saying that WHP minus DHP does not equal BHP ? but that undermines the basic principles no?

You mention that 1/4 mile times and vehicle weight can be used to calculate WHP, but surely that would be way out, as it is dependant on the ability of the driver to gear change, and any wheel spin, so it could fluctuate massivley - surely it's worse than an already debateable RR???

Cheers,
K.

[Tüls]

Quote: Originally Posted by GTT 270 (original)

Like i say, each to their own. I suggest you read this thread and the linked thread in more detail first. You don't offer much of a justification for your decision.

If you can measure Wheel HP, and you can measure Drag HP, then you have BHP

Unless we are all saying that WHP minus DHP does not equal BHP ? but undermines the basic principles no?

Cheers,
K.

I guess the question still remains... if you know the WHP which ultimately lines up with a speed trap/weight calculation... so is what matters in the real world... why does the BHP matter?

again... like you said... in the end it's probably just a matter of what you like... and again.. I use BHP all the time.. when talking to certain people... but if I am talking to some one about racing... I always speak WHP... cause it's what is actually making it to the ground...

ahhh philosophy!

[MiniIndy]

Quote: Originally Posted by GTT 270 (original)

Like i say, each to their own. I suggest you read this thread and the linked thread in more detail first. You don't offer much of a justification for your decision.

Read it and understood it just fine, thank you. I think my justification was clear as well, but apparently I may be wrong. Both sets of numbers can be skewed if you so desire. Until you start pulling your engines and placing them on an engine dyno, those BHP numbers can be seen as suspect IMO.

[GTT 280]

Quote: Originally Posted by Tüls (original)

if you know the WHP which ultimately lines up with a speed trap/weight calculation...

Sorry, i fail to see how WHP can be taken from a speedtrap - 1/4 mile - vehicle weight calculation when this involves driver error, gear changes, wheel spin, direction of travel, wind drag etc. ??

As i say above, would this not be less accurate that a RR that actually takes the Nm reading generated by the wheel directly?

The never ending debate. I think i am going to end it here, as i have the answers i need. it's getting boring now



Cheers,
K.

[Tüls]

Quote: Originally Posted by GTT 270 (original)

Sorry, i fail to see how WHP can be taken from a speedtrap - 1/4 mile - vehicle weight calculation when this involves driver error, gear changes, wheel spin, direction of travel, wind drag etc. ??

As i say above, would this not be less accurate that a RR that actually takes the Nm reading generated by the wheel directly?

The never ending debate. I think i am going to end it here, as i have the answers i need.



Cheers,
K.

accually what's funny about the strip... and maybe Paul can enlighten this a little.. is that the trap speeds dont change as much as the times do in these circumstances... we long had similar debates on "US" forums... but then people started seeing... there were very little differences in traps speeds... but the times were the things effected by driver error, gear changes, wheel spin, direction of travel, wind drag...

so there you have it...

It's not a never ending debate... I mean... for me.. it's all about learning... anyone who thinks they know it all is surely the biggest fool

I'll see if I can find the post where this same thing was laid out with times and trap speeds... it was very enlightening.. and frankly I never thought drag racing meant squat till people like Paul and Hubie helped me understand what was going on...

[Paul Webster]

http://www.mini2.com/forum/engine-dr...orsepower.html


Happy reading Karl