Just had her on the Rollers

[terryb]

at Janspeed in Salisbury.

Measurements are taken at the wheel only and were

278 bhp and 285 lbsft torque

Happy with those figures. If transmission losses are 25% then that equates to 370bhp and 380 lbsft. Or at 22% they would be 356 and 365 respectively.

:D:D:D

[blacky555_RA]

Nice one Terry....must be an awesome drive :D :D

Mine is going on the rollers next weekend for a "baseline" run before I start modding :D

[terryb]

It certainly is mate.

After researching, the best opinion seems to be 24% transmission losses for Subaru Impreza's, making my figures 366bhp and 375 lb-ft torque :D:D:D

[r4lly]

very nice mate, :D what mods have you done?

[terryb]

very nice mate, :D what mods have you done?

uprated fuelling - sx pump, reg and apexi 550 injectors,FMIC, uprated turbo - MD191 (1.5 bar), GEMS ECU, HKS racing suction kit - decatted of course. :D:D:D

[Gazza]

Good power there Terry, think i've got a bit of catching up to do though... :)

Still, was happy with my results considering only got a De-Cat & a Blitz Panel Filter... 237.39 Bhp - 231.57 lb/ft torque At the wheels... Which subject to debate comes out about 313 Bhp - 305 lb/ft torque at the flywheel...

A bit gutted they didn't finish my 2nd run tho, because looking at my graph it was about another 10 brake up on the 1st run, he backed off at 4k tho because of heat soak... :(

Gazza...

[terryb]

Good power there Terry, think i've got a bit of catching up to do though... :)

Still, was happy with my results considering only got a De-Cat & a Blitz Panel Filter... 237.39 Bhp - 231.57 lb/ft torque At the wheels... Which subject to debate comes out about 313 Bhp - 305 lb/ft torque at the flywheel...

A bit gutted they didn't finish my 2nd run tho, because looking at my graph it was about another 10 brake up on the 1st run, he backed off at 4k tho because of heat soak... :(

Gazza...

Yours are still good figures mate - especially on a lightweight car :D

[oldmanmille]

Nice one terryb....had mine at Tegsport with 297 and 276lb/foot,at the wheels. I just love the look on other drivers faces when i hit the loud thing... :D

John

[TonyB]

Im only running around 255/260@wheels but thats 318bhp at the fly, not sure about how much torque but 356lbs at the fly, car is standard except an STi panel filter :D

Tony

[JTaylor]

Im only running around 255/260@wheels but thats 318bhp at the fly, not sure about how much torque but 356lbs at the fly, car is standard except an STi panel filter :D

Tony

356lbft with just a panel filter! :shock:

[Eagle]

As a matter of interest, what is the calculation for working out the power at the flywheel?

[terryb]

As a matter of interest, what is the calculation for working out the power at the flywheel?

I researched this and the best indications are a 24% power loss from the flywheel to the wheels.

So if you have the wheel power, then to calculate the flywheel power you have to divide by 0.76 :D

[oldmanmille]

ouch! that gives me 390 BHP at the fly then...thought mine was quick :D

[Eagle]

As a matter of interest, what is the calculation for working out the power at the flywheel?

I researched this and the best indications are a 24% power loss from the flywheel to the wheels.

So if you have the wheel power, then to calculate the flywheel power you have to divide by 0.76 :D

On that basis that gives me 421bhp at the flywheel :shock:

[TonyB]

Im only running around 255/260@wheels but thats 318bhp at the fly, not sure about how much torque but 356lbs at the fly, car is standard except an STi panel filter :D

Tony

356lbft with just a panel filter! :shock:

The joys of twin scroll and equal length headers :wink:

As for the calculations of BHP@wheel..... tosh, total tosh (putting it mildly) as the figures for wheel BHP is calculated on the drag, so you need the fly BHP to work it out, plus you may find that it is nowhere near 25%, 20% should be your highest upper mark, 18% is more like it, especially with a DCCD equipped car, and i know of not one rolling road ive been on (and ive been on a couple :wink: ) that have not given the main figures at the fly rather than at the wheels as the rolling road calculates the fly figures first.

Tony :D

[terryb]

Im only running around 255/260@wheels but thats 318bhp at the fly, not sure about how much torque but 356lbs at the fly, car is standard except an STi panel filter :D

Tony

356lbft with just a panel filter! :shock:

The joys of twin scroll and equal length headers :wink:

As for the calculations of BHP@wheel..... tosh, total tosh (putting it mildly) as the figures for wheel BHP is calculated on the drag, so you need the fly BHP to work it out, plus you may find that it is nowhere near 25%, 20% should be your highest upper mark, 18% is more like it, especially with a DCCD equipped car, and i know of not one rolling road ive been on (and ive been on a couple :wink: ) that have not given the main figures at the fly rather than at the wheels as the rolling road calculates the fly figures first.

Tony :D

Tosh :roll: :roll: What you on about man?? How can the rollers, which are connected to the wheels (as the wheels are on top of them) possibly measure flywheel power/ torque?? Please explain that to me....

As for the figures I have used for calculating losses - I didn't just pluck that figure out of thin air - I spent ages searching numerous forums for a reliable figure that came from people in the know - and 24% is the figure.

Why would there be less of a power loss with a fully locked DCCD drivetrain compared to a standard scooby 4x4 drivetrain??

Your technical knowledge is obviously far superior to mine - so do explain all :lol: :lol:

[TonyB]

Im only running around 255/260@wheels but thats 318bhp at the fly, not sure about how much torque but 356lbs at the fly, car is standard except an STi panel filter :D

Tony

356lbft with just a panel filter! :shock:

The joys of twin scroll and equal length headers :wink:

As for the calculations of BHP@wheel..... tosh, total tosh (putting it mildly) as the figures for wheel BHP is calculated on the drag, so you need the fly BHP to work it out, plus you may find that it is nowhere near 25%, 20% should be your highest upper mark, 18% is more like it, especially with a DCCD equipped car, and i know of not one rolling road ive been on (and ive been on a couple :wink: ) that have not given the main figures at the fly rather than at the wheels as the rolling road calculates the fly figures first.

Tony :D

Tosh :roll: :roll: What you on about man?? How can the rollers, which are connected to the wheels (as the wheels are on top of them) possibly measure flywheel power/ torque?? Please explain that to me....

As for the figures I have used for calculating losses - I didn't just pluck that figure out of thin air - I spent ages searching numerous forums for a reliable figure that came from people in the know - and 24% is the figure.

Why would there be less of a power loss with a fully locked DCCD drivetrain compared to a standard scooby 4x4 drivetrain??

Your technical knowledge is obviously far superior to mine - so do explain all :lol: :lol:

The rolling road calculates the power on the run when you put your foot down and the wheels spin up, the calculations for the flywheel power are done using resistance from the rolling road, these are the most accurate figures you get, the power from the fly to the wheels (and by this time you already have your flywheel power btw) are done after you hit the red line and come off the power, hence the drag factor that provides you with your power to the wheels and calculates your losses, this isnt as accurate as it changes.
As for the differences in diffs, the Type RA with DCCD has an open diff and even when locked (it doesnt have to be locked btw to give your fly wheel power if you have a good rolling road) are different to the diffs used on other impreza's.
A good one is to speak to bob rawle who calculated his JDM STi (new age with dccd) to have 15% losses, a far out mark from your 24% :wink: but if you want to also take what some of the other sites say, 33% is a good one for tranmission losses in a scoob :oops:

Tony

[terryb]

Tony

You've got it fundamentally wrong. A rolling road measures figures at the wheels ONLY - it can only do this. An engine dynamometer measures flywheel ONLY - it can only measure that!!!

You are right that the rollers measure drag - but this is when the clutch is depressed at the end of the power run, and thus when the engine is disconnected from the drivetrain and thus the rollers are measuring the drag (resistance) from the drivetrain only.

So the rollers measure power/ torque at the wheels, and then by measuring the drag of the drivetrain and adding the 2 figures together, you get the figures at the flywheel.

Think about it - it makes logical sense :D

If you still don't believe me then have a good read of this - http://www.clubwrx.net/forums/showthread.php?t=56650

Terry :D

[TonyB]

Interesting Terry :D
Though its an old thread really and they are americans so ill not take too much notice ;)
The reallity of it is to take your car back to the same rolling road on several occasions (ive done this ;)) and see where the biggest differences are (oh its also one of the latest Bosch rolling roads) and my engine fly figures have always been within a couple of bhp of each other on the last 4 occasions (my car is still loosening up) but its lowest was 314, 315 then a 282 (my ecu had retarded alot from the 16 multiplier to 8 ) and on the last occasion, 318 , this was done over several thousand miles, but the wheel figures have all been different, varying from 240-260bhp, so ill let you decide which is the most accurate ;) but its not the wheel figures.
So basically 4bhp (except when my car retarded, on the road btw and not on the rolling road) difference over 12 months, thats pretty accurate ;)
It probably also depends on the type of rolling road you use, the one i used i believe does engine dyno power, but it is a really up to date one (think its the only one in the uk?) and is a little more accurate than say..... well lane for instance.

Tony :wink: