Wheel BHP convert to flywheel BHP

[Nealevo]

Does anyone know how to convert wheel bhp to flywheel bhp just want to test a theory out on my car but getting some wierd figures. Help please

[T5frankie]

Does anyone know how to convert wheel bhp to flywheel bhp just want to test a theory out on my car but getting some wierd figures. Help please

every car will be different mate

[t5_monkey]

That's basically like asking how good a band is!

can of worms. As a rule of thumb - add 20% on.

Other than that, you'll see endless threads about people arguing over it.. .there's no truly accurate way to measure losses apart from perhaps going on a MAHA dyno which are supposed to be pretty good.

[Yosser]

There is no formula, it's guesswork.

Good read on this topic here: http://www.pumaracing.co.uk/trans.htm

[cherry1809]

If you want a not very acurate way...

Less WHP to FWHP 15% for FWD, 20% for RWD and 25% for 4X4. Usually completely wrong though.

[Wobbly Dave]

My losses are just 8% across 3 runs done at the end of July this year. I think 20% is wildly overated.

[t5_monkey]

My losses are just 8% across 3 runs done at the end of July this year. I think 20% is wildly overated.

I believe losses can also depend on if the dyno is a one roller, two roller, your geometry, tyre pressures blah blah...

Basically... don't bother calculating, just take your car on the 1/4 mile.

[p fandango]

Basically... don't bother calculating, just take your car on the 1/4 mile.
as you know, alot of things can vary your 1/4mile time so i've never been keen on using that for any sort of power comparison. Think i've got upto 2second differences between runs on the same day

[lance]

Well at 15% loss my car would have 265 BHP but according to HLMs dyno she has 230 whp and 248 BHP which seems bang on!

[antz]

I dont bother with flywheel powers due to transmission losses and such. Flywheel powers are just pub talk to make you sound awesome in front of your friends. What matters is the power you get at the wheels.

My Escort mk2 is 130bhp at the wheels with a bit more to come from a re-tune of the carbs. Ive had people say its anywhere from 143-150bhp at the flywheel but I dont care. I know Ive got 130bhp spinning up those rear wheels :)

[t5_monkey]

I don't really care about the power any more... it's like the Arab Israeli conflict, people argue about dynos now and will be doing the same in 1000 years... As long as it goes pretty fast and sounds EPIC that's the main thing.

http://www.picanese.com/pbpics/60e91c681b8303f54dcdf48db805f961.png

[smithy]

the only thing im interested in is what the car goes like on the road ,my car goes on the rollers to check the afrs for boost and make sure i its running fine

[claymore]

I don't really care about the power any more... it's like the Arab Israeli conflict, people argue about dynos now and will be doing the same in 1000 years... As long as it goes pretty fast and sounds EPIC that's the main thing.



I agree, I don't care what hp I have, I just love the way it deliveres it :)

[T5frankie]

i disagree i want a zillion ponies, never gonna have enough lol

[t5_monkey]

As long as you can absolutely annihilate some tosspot in a 320d up a M-way slip-road - who thinks his diesel torque and an 'M' badge gives him super car slaying pace....

... it's all good :)

http://3.bp.blogspot.com/_xpXmvbLt7lM/SsiAu9kZEvI/AAAAAAAAAi8/qGTq8t7807U/s320/fail-owned-bmw-fail.jpg

[Wobbly Dave]

Single roller dyno - 34 psi in the tyres. 14.613 sec quarter @ 102.99mph. 289 whp - 406 NM.

Peak figures are not the full story. Area under the torque curve, sustain & smoothness of that curve are also very important.

It is more also to stick to the same dyno where ever you go.

[t5_monkey]

My last dyno was 228whp - 375nm

14.77 @ 99.5 - alongside wobbly dave (until he hit 3rd gear that was!)

For Reference - Focus RS (with professional driver etc..)

1/4 Mile - 13.77s - Terminal Speed 105mph

As wobbly alluded to dyno is better for 'before' and 'after'

[Rnash2002]

All dynos will be different so no way to work out proper figure.

[Wobbly Dave]

All dynos will be different so no way to work out proper figure.
Exactly why you should pick one & stick with it.

[T5frankie]

My last dyno was 228whp - 375nm

14.77 @ 99.5 - alongside wobbly dave (until he hit 3rd gear that was!)

For Reference - Focus RS (with professional driver etc..)

1/4 Mile - 13.77s - Terminal Speed 105mph

As wobbly alluded to dyno is better for 'before' and 'after'

ford focus aint that quick mate (13.77)?

http://www.youtube.com/watch?v=DqNNU0Frfck

[lance]

ford focus aint that quick mate

http://www.youtube.com/watch?v=DqNNU0Frfck

Its a dam site quicker than most of the old T5s and Rs on here and loads quicker around corners but it does have a thumping Volvo engine!
I have to say its not the fairest of test as I bet after 100k the renault will be knackered and the Pocus will still have years of life in it also the Focus wasnt tuned if it had been it would have been a very different story afterall look what Polestar did with the C30! Also Evo did test a Montune ST against a standard RS and found it quicker in a straight line 0-60 and 1/4 mile as it developed a load more torque and nearly the same BHP!

[t5_monkey]

I think it depends on the strip - Not sure what the official 1/4 mile time is, 13.77 could be remapped maybe.

As for the Renault... Fifth gear said it was less fun than the RS and under steered, plus it will be a puddle on your driveway in 5 years time.

It'll always sound like a ruff 4 banger too, can't beat that 5cyl roar.

[T5frankie]

i do love the ford st's and rs's just cos they are volvo powered and sound good on boost lol

[LiamT4]

At avon last year there were a couple of focus rs, running mid to low 14s and a standard astra vxr that was running faster, a 14.1.

[T5frankie]

At avon last year there were a couple of focus rs, running mid to low 14s and a standard astra vxr that was running faster, a 14.1.

i raced an astra vxr at santa pod it got a 14.9

[t5_monkey]

At avon last year there were a couple of focus rs, running mid to low 14s and a standard astra vxr that was running faster, a 14.1.

Astra VXR seems to do well on the strip.

They do have a closer ratio box... that makes a big difference on the 1/4

Do the VXR have a DMF ? that really makes a good take off quite awkward.

[LiamT4]

i raced an astra vxr at santa pod it got a 14.9

Not a good run then, any decent driver in an astra vxr will do mid 14s all day long. Out of all the hot hatches i'v been in they are by far the quickest (reletively speaking) in a straight line (standard), you'd think they have more than there figures suggest.

I'v seen an evo struggle to get under 15s, doesn't matter if its a quick car if its got a crap driver.

[lance]

I agree with the above ive seen a V10 M5 running 15s but doing it at around 107-115 mph! It is difficult to get a perfect run, I know I shouldnt say it but I find it easier to get the power down on a real road in good conditions no matter what car Im in!

[merc85]

Anyone Raced a Cupra k1 Standard 240bhp.? i find it very very close with my 855 t5 manual

[t5_monkey]

Anyone Raced a Cupra k1 Standard 240bhp.? i find it very very close with my 855 t5 manual

If your car is the 220-300bhp range there'll be precious little in it at 'sensible' road speeds.

big power only really makes a difference above 100mph...

If you're following one down a windy road, he'll have a bit less midrange so need to stir the gearbox a bit more... but will be a bit quicker at the top end.

(plus he'll go around the corners faster!!)

[merc85]

I find i've more top end as his is restricted.. lol mid range very close, i'm hlm,rip,walbro simota intake.

[popuptoaster]

We took my ex's Mk1 escort down to Track & Road in Rainham, her car had a brand new HT racing pinto, it had been on their engine dyno and then we ran the car on the single roller dyno, the escort has a Sierra 4 speed auto box in it.

T&Rs dyno got within 1bhp and was spot on for torque @flywheel figures compared to HTs engine dyno figures, and we didnt tell the two Steves what they were before they ran it either.

A decent dyno wand a decent operator can get proper figures, a lot of specialist manaufacturers use T&R for mapping work, those boys know what they are doing, even Noble have had test cars down there.