power loss

[projectgtir]

Had my car setup today at thor-racing, they have a hub dyno which only gives power at the hubs and the readout doesnt give power at the flywheel.

My car made 272hp at the hubs at 1.2bar .
Taking into account losses from the drivetrain at 25% for awd it works out at 340 at the flywheel .

So my question is, does this seem abit high or is 25% for losses to much .

My mods are ;
proper 3" elbow/downpipe to mongoose
fuel pump
apexi avcr and apexi afc neo
denso plugs
helix organic clutch
jun flywheel
air con removed

Factory turbo and intercooler

 

[Trip]

25% is usually taken as drivetrain losses from engine (flywheel) to the wheels. I doubt with wheels on and with wheels off will make a big difference on the dyno.

Taking 363 BHP at the flywheel less 25% = 272 WHP


363Bhp is a little high for your mods especially if you are running on standard injectors and MAF.

 

[Mad]

% loss through to the wheels can vary, especially between FWD,RWD and 4WD but a rough rule of thumb is 18% to 25% for 4WD.

As well, different Rolling Road's sometimes give different power figures anyway which makes it even more confusing to give a true power figure.

Also, it depends on if you look at bhp as a gain percentage, or loss percentage (confused now) over whp.


272 whp at 18% gain = 320bhp
20% gain = 326.4bhp
22% gain = 331bhp
25% gain = 340bhp

340bhp at 25% loss = 255whp
340bhp at 22% loss = 265whp
340bhp at 20% loss = 272whp
340bhp at 18% loss = 278whp

The Escort Cossie's used to be renound for loosing a lot of power through the transmission but do not think the GTiR's are as bad.

Very confusing I know lol.

 

[projectgtir]

Yeah thanks guys ,as long as the fueling is ok im not botherd anyway i just wanted to know if i was in the right region of power for the mods.
I just dont understand why its always a pecentage though, for example
A skyline with say 1000bhp would lose 250hp through losses but how when the drivetrain hasnt changed, its losing more power based on this than a standard one almost makes.

 

[fubar andy]

as long as the fueling is ok im not botherd anyway

That’s the best way to think about using dyno’s

At the end of the day as long as there are not issues with the fueling and no DET then its served is purpose. Personally I take all figures with a pinch of salt regardless if they are at the wheels, hubs or fly.

Most "operators" know ways to bump up the figures so that when you go away, you'll be feeling better about yourself, your car and they'll be in the knowledge you’ll be back for another session of “heightened” dyno readouts. ;-)

 

[PobodY]

I thought all the power levels were lower than expected from Dyno Demon, but as they were all done at the same time it made the comparisson easier... and any way you look at it I'm way down on power compared to you Andy.

However, I've got a good picture of my boost curve and proof that my bleed valve isn't spiking (and that it holds the boost pretty well). I can see that my fuelling is good across the rev range, and that I have (or had hopefully) an ignition problem... So like you, I'm pretty happy with the experience, but unsure about the "real" power output of my R.

 

[markwashington]

Most "operators" know ways to bump up the figures so that when you go away, you'll be feeling better about yourself, your car and they'll be in the knowledge you’ll be back for another session of “heightened” dyno readouts.

Brilliant and so true, I've got quite a few readouts for my car and they vary massively from 330 to 380 on the same spec!

 

[Mad]

I never foget when I had an Evo 4 with boost upgrade, zorst and air filter.

Powerstation RR it at 265bhp on the Thursday and I was not impressed so went to Power Engineering the next day
who said 325bhp and on the Sunday I ran a 12.6 quarter mile at Santa Pod.

325bhp was probably more realistic comparing it to the quarter mile time but it is unbeleivable the differences you can get between dyno's.

 

[stumo]

I never foget when I had an Evo 4 with boost upgrade, zorst and air filter.

Powerstation RR it at 265bhp on the Thursday and I was not impressed so went to Power Engineering the next day
who said 325bhp and on the Sunday I ran a 12.6 quarter mile at Santa Pod.

325bhp was probably more realistic comparing it to the quarter mile time but it is unbeleivable the differences you can get between dyno's.

and you could have gone to xyz dyno and they'd have said 500hp.:der:

It's all in the fiddle factors that can be changed on any dyno.

 

[Spikey]

What things can we do to Improve from Transmission losses?

 

[red reading]

What things can we do to Improve from Transmission losses?

Straight cut gearbox and final drive,ceramic bearings,thinner oil in gearbox and diffs (not a good idea!), run less pre-load on the rear diff and gearbox and transfer box bearings (reduces there life dramatically), use friction modifiers (teflon etc, but not in any friction/clutch type diffs ), machine each gear down to the bare minimum for your power required, reduce rotational mass (light weight rims)..............how much do you want to spend?

 

[skiddusmarkus]

Mine made only 315bhp(1.1bar) at the flywheel on surrey RR but a healthy 267bhp at the wheels.I put this down to very light rays wheels, 5kg flywheel, lightened and balanced bottom end, lightweight pulleys inc cam pulleys.It all adds up and supposedly every kilo you save off the rotating mass is basicly free hp.Its obviously doing something as I only lost 15% compared to a lot more on most cars.
It should be on the rollers again on wednesday so will see if it was just a blip.

 

[red reading]

losses increase with power, sort of, my whole drive train is straight cut (much lower losses) and the car made 407bhp at the wheels,which means the 500.1bhp at the crank i was getting 25% loss, there is no true way to calculate losses unless you actually measure them for each component, dyno's just guess.

 

[Spikey]

But what else can be done against Transmission losses?
Solid prop? lsd? solid mounts?

 

[skiddusmarkus]

Carbon fibre driveshafts/prop.Thinner tyres.

 

[Spikey]

Carbon fibre driveshafts/prop.Thinner tyres.

So removing weight and drag...

 

[red reading]

prop is rotational losses (would'nt show on the dyno as it will be so smaller gain)
tyres are frictional losses (the dyno would calculate the differance, so you will not get any gain)
engine mounts will help with response not losses to the wheels,

and if you look at the top of the page i have listed transmission things you could do

 

[Spikey]

So nothing Practical then So is the 25-30% normal? even on a full spec rally/Race car?
also Im sure i have seen titanium Propshaft somewhere think it worked out 1k or so.

 

[red reading]

It's 18-25% and yeah its normal, old auto gearboxes were 33%..lol. and a ti prop will not make much differance, where as a set of magnesium wheels would, the more mass moves away from the center line the more inertia you'll get, hence why 2 wheels of the same overall weight but one that has the lighter rims and spokes would require less energy to accelerate and stop it..... shall i go on?

 

[Spikey]

I know about the Rotating mass from the wheels. But did not know it affected the loss so much. i have saved almost 20kg in weight with my new rims in total so ill see what the Difference is.