how does it calculate torque? and would it still be able to do this accurately if I changed, for example, the turbo and the maf?

:confused:

Using some difficult sums!

Sorry, but the only way I can see of measuring torque without a rolling road is to measure fuel flow, MAF, air temperature and manifold depression, and revs, and then do sums from there.

yeah, sorta didn't expect it would be easy maths (stuff that i would understand)

so changing the turbo/MAF/intake etc would possibly screw it up and make vag-com kinda spazz out :confused:

bugger...

Its basic heat engine calculations, given that it knows your fuel type and air flow in.

Not what I meant; I meant that the calculations were involved and technical, rather than that tuning the engine would stop them working unless you tune to the point of getting a floating point overflow (so much power that the computer can no longer represent the numbers involved correctly).

that's kinda not what i meant either i was thinking more along the lines of there being certain known constants, and fitting a larger turbo and/or maf messes things up :confused:

IIRC the constants are all either universal constants/conventions like the volume of a unit mass of air at a specific temperature, or things like the calorific value of the fuel. Basically, you'll not mess up a VAG-COM by running it with a tuned engine. OTOH I'd treat any power or torque figures not obtained from accelerometer or brake dynamometer testing as notional rather than actual values.

and fitting a larger turbo and/or maf messes things up :confused:

I don't think it can because otherwise VAG-COM would need to know exactly which engine you had and store specifics for that. I think it's much more generic than that...... You could always e-mail Ross-Tech and ask them

Chris

I was really wondering why it would indicate not a lot more than standard mk1 vRS power/torque, and why the resulting graph looked so similar to the Eiffel tower :confused:

The common concensus is that you shouldnt use it for power figures, more for fault finding and comparing various mods (airbox Vs. CAI etc.).

FWIW. I graphed mine in excel then added a correction factor to match the VAG-COM peak figure to the Marlin peak figure. The 2 graphs look pretty much the same over 2000rpm.

that's exactly what's going on here - a straight before and after comparison...:(

Haven't you done that before though with the airbox and CAI ?

yep, on my brother's octavia. and all that got changed was the CAI removed and the standard airbox installed - we got different, but very believable figures.

there's no way it's anything like an accurate representation in this particular case

So has he finally had a big turbo fitted, then ?

he hasn't got the factory turbo, but i'm not aware of him having a big turbo, no

I don't know enough about the power figures you're expecting, or about the s/w, to know if this even might be the case, but you might be running into either the overflow I mentioned earlier (tho I'd have expected no figures at all in that case), or a scaling problem, where, to avoid overflowing, the designer has changed the precision with which the figures are measured (which has the effect of measuring a much bigger peak figure, but on a rougher scale, for example, in decimal cos most people understand it better, measuring 1 to 100 every unit, or 10 to 1_000 every 10 units), and you've crossed a boundary to a lower precision scale.