jonb2010

If a standard Impreza (uk 98ish) is about the 210 bhp mark is this at the wheels or the flywheel ?

I have just seen a lot of posts about BHP and got a bit confused.

Callum Ferguson

iTrader: (1)

Figures for standard cars quoted around 210 - 220 bhp are at flywheel. They need to be tuned to nearly 300 bhp to make 210 ATW -and it makes them a little more ...interesting Hope this helps.

jonb2010

Cheers Callum

so when people hit the rolling road they are quoting flywheel figures ?

Callum Ferguson

iTrader: (1)

Yes, generally, when not specified it will be flywheel. John B, AndyF, Bob, Harvey, etc, will often provide ATW outputs as well as the flywheel figures. Most rolling roads provide both but the flywheel output looks better It takes a bit of effort to get 200+ bhp ATW & a lot of effort to reach 300+ bhp as these guys have. My standard STi made 177bhp ATW on it's first run which doesn't sound as impressive as the 264bhp flywheel figure despite being one and the same

velohead66

My all standard WRX Type R V-Ltd made 170.7kW at the wheels.

I was quite impressed, as that's ~226 bhp ATW,
and allowing for 25% power loss, that's 301 bhp at the flywheel.

Erm, SIDC FAQ quotes this as 300 PS (295bhp) so can't be too far off.

However, I beleive there is a tad of overstatement depending on in which gear you do the rolling road test.
Ideally 4th should give the same result as 3rd, is this the case ??

RB5_245

Well my RB5 (not WR spec) Made 175 ATW with only an Induction Kit and back box which AVA 'Reliably' informed me was below average for a standard WRX...... So who knows?

velohead66

So have you had very different results on either the same dyno in different gears, or different dynos in the same gear ??

Assuming no changes to car/engine of course.

DutchClutch

No,

The only time my car was put to the test was after the ECU-Tek,so during a roaddyno,and in 3d gear only.(In 3d gear windresistance isn't such a big 'partyspoiler' yet.)
Several simmelar ECUTekked MY99/00-car's with moreless the same setup here ran also on a 4WD-'powerbank',with very dissapointing max.power-figures.(Est.250BHP)This low output was due to the very bad coolingconditions during the testrun's.
One car however did have good powerfigures,which nearly matched the car's raoddyno-figures,but this was the only FMIC car.The FMIC is standing right behind the coolingprop!
As said,a 'powerbank' is useless for a TMIC-car's real powerfigures,due to bad coolingconditions,which can go up to a 20-25 degrees difference when compared to drivingconditions.Don't forget the TMIC's bad place on top of the hot runnig engine too,making things even worse.

To have a good reliable run,you would have to place the car in a windtunnel,to produce enough wind to create real roaddriving-conditions'.

And don't forget that the outcome of a roaddyno is simply mathematic's,using the real data that count's.Some guys here have a G-tech in their car,wich can perform a roaddyno too as you know,and match their DeltaDash roaddyno outcome.It's is just a very precize measuring method,and the only reliable test for a TMIC-car,which normally runs with the bonnet closed,and cold air flowing through the IC.

Arend.

DutchClutch

My GTT(MY99) with Japanese import engine(Different shaftcam's/cilinderheads)is tuned with ECUTeK.When the car was finetuned after a few houres,we did a 'roaddyno' in 3d gear.(This program results in a power/torque-grafic which shows the wheelpower/torque as you probably all know.)
"Look what a unexpected great result we accomplished!" the tuner showed me.I looked at the figure on the laptop,and read 228BHP!?!

"At the wheels!" ,the man sead,"at the wheels!"

Telling me about the 0.25-0.26 loss,a very big smile from ear to ear apeared on my face.

After heavy enhancement of the grafic's an 280BHP is realistic.
A raoddyno is more reliableby by the way,than a run on a 'powerbank' because the cooling drivingwind can never be generated by a simple prop standing in front of the car,especially in case of a TMIC.The inlet-air temp's measured in both cases can go up to 20degrees or more in advantage of the raoddyno!And where do we drive our car? Wright!
It is very important of course to feed the DeltaDash the right data,so your real carweight,and wheeldiameter has to be measured first.My car's real wight during the run was 1446kg(Incl.driver,co-driver,and half a fueltank)

Believe me,a 4WD'powerbank'is very handy when a car has to be tuned.But when you really want to measure the car's streetperformance a roaddyno is absolutely the best way.


You allways hear about flywheelpower,but the only thing that really matters is your power at the wheels of course.But the higher the figures,the better the sell.

Arend.

[Edited by DutchClutch - 6/9/2003 1:27:54 PM]

[Edited by DutchClutch - 6/9/2003 1:29:09 PM]

[Edited by DutchClutch - 6/9/2003 1:30:37 PM]