S4/RS4 Drivetrain Losses

[Dippy]

...but the torque band from 3000rpm to 6000rpm is awesome, showing 700nM peak at 4750rpm on G-Force's RR. ...

That's nothing. A JATO would give you 7000nM from 0 to 60,000rpm. Terminal, but what a rush!

[Andiroo]

[img]images/graemlins/roflmao.gif[/img]

Andiroo

[Nige_RS4]

Dippy,

But I suppose that 'bragging in the pub' is what MOST people want the bhp figure for isn't it?

There is probably an un-written rule that says add 10% to your 'real' hp figure per pint of beer that has been consumed.

[img]images/graemlins/beerchug.gif[/img]

[Andiroo]

It has certainly woke me up with regards to what to expect when you change rolling roads - in the space of two weeks I've had three different bhp figures spread by 90bhp all with the same torque figure.... [img]images/graemlins/confused.gif[/img]

Andiroo

[Joshie]

Well many on this site will know that I've always had my doubts about claimed power outputs. I guess the only sure way to find out what sort of power and torque your engine is putting out is to lift the engine and get a power at the flywheel figure.

Having read this thread it occcured to me that unfortunately, "getting a second opinion" just seems to be that, an opinion.

I wonder how the likes of Abt/MTM measure the performance of their upgrades.

[Nige_RS4]

Andy,

It has certainly woke me up with regards to what to expect when you change rolling roads - in the space of two weeks I've had three different bhp figures spread by 90bhp all with the same torque figure....

Aahh, most interesting ! I did some reading up on a handful of rolling road mfr sites and noticed that they reported that RR's only measures torque. Here's an extract from one of them ;

"Horsepower" is a largely imaginary figure, like "advertised duration" in cams or "user friendly" in software. What the dyno measures is torque. You take the torque figure, then plug it into an equation with the RPM, altitude correction, your current astrological chart and maybe roll the dice, and you get horsepower.

Nige.

[Dippy]

Andiroo,
Actually your experience is quite assuring. As we all know its the torque curve which is the really important thing to see, so if these various RRs all showed the same sort of torque result then you have confidence that that is the truth.

Since power is simply a function of torque, it means that your power curve IS the same, it's just that you don't really know what it is because of the differences between the methods of calculations.

I have a suggestion: When you fit your JATO you might as well remove the engine (bit less weight so your 0-1000mph figure should be a bit better). If you arrange for an engine dyno then you'll get a true flywheel power measurement and that'll help us all understand this issue a bit better!

Well done [img]images/graemlins/thumb.gif[/img]

[TimJMS]

Poster: Andiroo
Subject: Re: S4/RS4 Drivetrain Losses

G-Force are the most knowledgable guys in the business and they work on 28% for the Quattro as of yesterday, which is comparable to the Skylines. Like Karl says, the best way is to see if a bog standard RS4 has been ATW measured on G-Force and this will be the definitive answer

Andiroo

At the RS246 meet at G Force on 31 May the only truly standard car that went on the rollers was Nick M's.

IIRC and I usually do [img]images/graemlins/smirk.gif[/img] then his power output on the morning run, when converted from at the rollers to at the flywheel was very close to the 380hp claimed by Audi.

Mine was slightly down, even though the day was marginally cooler when mine went on. Possibly because of tyre / rim combination.

Therefore the losses G Force factor in must have been fairly spot on.