whip

Just been looking through the dyno graphs, it seems that UK cars have much larger transmission loss compared to imports. A few examples...

UK
193paw 289bhp
179paw 261bhp
153paw 250bhp
140paw 229bhp

Jap
202paw 289bhp
207paw 266bhp
213paw 278bhp

Whilst there are plenty of UK cars making 280+ hp, there don't seem to be any that make more than 200bhp at the wheels.

Is this just due to gearing or something?

Whip

AlanG

85 brake loss last Sunday on a UK car.....211 at the wheels......more to come for definite....

ustolemyname??stevieturbo

iTrader: (1)

Where are the rolling roads that provided the info, what tyres where they using, size of wheels, tyre pressures, oil in gearbox/diff?? All these factors will contribute to different transmission loss figures on the rolling road.

whip

The figures are off the scoobynet dyno section, and seem to be a mix from different RR days at Power Engineering.

Just seems to be a big coincidence that all the Jap cars are getting around or over 200bhp at the wheels.

Whip

mutant_matt

Presumably the transmission losses are not a linear relationship between flywheel and wheel power figures? IF this is the case then they are going to have a similar loss at a given power level but as the flywheel power goes up, the losses do not go up at the same rate?

I've seen Moe and Trout's cars on the rollers several times and (from memory), they seem to get similar PAW and PAFW figures, even though one is a UK car and one is an STi.

Matt

mutant_matt

...also, STi's have lower gear ratios and most Dyno runs are always run in 4th gear. This would in itself account for higher PAW figures for a given PAFW for STi's vs UK cars.

The other difference which you need to take into account is that all Type-R based trasmissions (RA, Type-R, 22B) all have a different drivetrain which have less losses and these also have higher PAW figrues than other Scoobs. The RA's also have lower gearing again than the STi's.....

Matt

dowser

PAW figures are meaningless - apparently 5psi more tyre pressure will give 5-10 more PAW. During the coast down after a power run the dyno calculates the losses through the drivetrain to arrive at the flywheel power.

Try it - do 2 runs back-to-back with different tyre pressures; PAW is different, flywheel should be the same.

Richard

mutant_matt

Dowser,

You're right - Merv @ PE told me that he did 3 runs with tyre pressures at 20, 30 and 40psi and the PAW figure went up with each run but the PAFW didn't change.

Matt

Trout...

Since when has Moe had the same PAW as me! LOL

STis seem to have lower losses - but it is probably the gearing that seems the make the difference. When Moe gets the same PAFW as me - his PAW figure is typically 10-15bhp lower then me.

When he got close to my PAW figure - his PAFW was 10bhp more than mine. Strangely my highest PAW figure ever - resulting in my lowest PAFW figure by at least 10bhp *sob*

However the Trout car has had a few little changes hugely improving the seat of the pants torque and top end smoothness - will there be more power? Who knows!

Trout

mutant_matt

Trout, no offence meant m8 I did say from memory they were "similar"

Matt

Sam Elassar

hi there

it is actually only due to the gear ratios. the shorter the gear rations the higher the power at the wheels and the lower the transmission loses and vice versa. so for a uk car to pull the same paw as an sti that is an achievment. that is why you can't compare paw in cars with different gear ratios. so paw will the be the most accurate when comparing stis,p1 while if you are going to compare uk to sti you have to take the power at the flywheel figures.

i remember doing few runs at the same rolling road with my uk car using 3rd, 4th and 5th gear. and the results were consistent. 3rd gave the most paw while 5th gave the least. the transmission losses increased going from 3 to 5th. you also need to take into account that reving hte car to 7000revs in 3rd and 4th will give different speed. the higher the speed the more tansmission loses.

if course if you want more transimssion loses make sure you turn up to the rollers with a knackered clutch that could be worth anything about to 30-40bhp


sam
my 2p worth.

The Man From Rangoon!

what i would like to know is;how can 2 cars producing similar bhp,have ,in some cases,vastly different torque figures?

john banks

Peak torque typically arrives at about 3500-4000 RPM according to manufacturers figures. Peak power typically arrives at 5500-6000. Obviously mods can affect these. Power is proportional to torque * engine speed. So for example a small turbo at high boost might produce big torque but struggle to hold enough up to the peak power point resulting in lower peak power.