ScoobyNoob79

How accurate is the dyno in romraider?

I decided to run a dyno on my supposedly stock 2004(53 plate) WRX PPP Wagon(5 speed manual) to see if it was pulling standard figures.

So I made sure I had the up-to-date definitions etc.

I set the car as a 03 E/USDM WRX WGN 5MT, tyre size 215/45/17, selected 3rd gear for the run, delta weight 225lbs, base weight 3165lbs and hooked it up and took it for a run.

Rolling start from 2000rpm WOT up to 7000rpm.

Having read articles from other forums and the romraider forum they say the figure produced is WHP and you can use some math to convert that figure to BHP with drivetrain losses, they also say the MAF reading is also pretty close to your BHP figure.

So the figures:

Dyno showed 262.7 and the MAF showed 249.38 max, so these figures would be WHP.

Using the formula from the other article is says the following:

WHP to BHP is WHP / 0.74
BHP to WHP is BHP * 0.74

Apparently this figure covers drivetrain loss.

So, a stock WRX would be:

227bhp * 0.74 = 167.98whp
167.98whp / 0.74 = 227bhp

A stock WRX with PPP would be:

265bhp * 0.74 = 196.1whp
196.1whp / 0.74 = 265bhp

So, if these figures and formula is correct and romraiders dyno is accurate, then my dyno figure would produce:

Dyno: 262.7whp / 0.74 = 355bhp
MAF: 249.38whp / 0.74 = 337bhp

Now, correct me if I'm wrong, there is no way a stock WRX with PPP is going to show figures like that.

So, either the dyno run was inaccurate, or the car has had more done to it than I was lead to believe and if it really is pushing out this figure then I better start looking for a 6 speed tranny.

Cheers,
Scott

ScoobyNoob79

Anyone?

Shaun

Transmission losses are too high imo. Aim for around 20% and you'll be more accurate. No idea how RR deals with smoothing, but that will have an influence. You also need to take into account that these forms of dyno show the extreme peaks and troughs of how it takes figures along the rpm range.

Log things like boost and see what it's pulling as that will almost certainly tell you whether or not it's really just a PPP etc.

There are all other manner of ways to ensure you gain "More" accurate figures as well. You must ensure your road is straight and dead level. Make sure the weight is representative of your vehicle weight WITH fluids AND passengers etc etc.

ScoobyNoob79

Cheers Shaun.

I ensured the weights where correct and the road was pretty level, as I've not got a boost gauge fitted yet I've used RR to check Manifold Relative Pressure(corrected) as that's apparently closest to 'actual' boost?

That showed 17.56psi, the log is here if you'd like to check it out: https://docs.google.com/spreadsheet/...XWktGNlE#gid=0

Thanks again,
Scott

Bob Rawle

Your figures are way off, a TD04 turbo will not make 300 bhp at the flywheel with good supporting mods except in very rare circumstances.

You have a vehicle weight of 1438 kg, where did that come from ?

Maf figure is not equivalent to whp just to say.

Losses will vary according to vehicle type and the actual power level being produced so not a constant and not 26%

Look at some of the published graphs on here to get a better feel for that

cheers

bob

ScoobyNoob79

Hey Bob,

Yeah that's what I'm trying to figure out, whether it is a td04, or whether it has more mods than I was led to believe.

The weights are from the manual.

The equation and MAF figures are what I found on another forum.

I think the easiest solution would be to get it on a rolling road and see whats what.

Ohh, btw, the log attached above isn't the one I run the dyno on.

Cheers,
Scott