BHP question (RR and Vag com)

[Shock_Xe]

Right... where do i start?? Firstly where do the likes of stealth get their figures from on their RR?? i.e. at wheels, flywheel?? etc

Secondly Where is Vag-com calculating it @ (when using block 120)

The reason i ask is that myself and Andy blunt had our motors Rolling roaded at stealth and bout got around 210bhp. However on Vag com today I got 148 (low 9) and he had 157 (he on high 9) and stevo (leon cupra) got 150bhp. Now all these cars are down on power according to this However torque was 200lbs for myself and andy and a little less on the leon. All the runs were in third from 1,500 rpm (Leon in 4th) (also only got 148 on local RR today, Never got above 164bhp on there!)

Am I doing something wrong?? I used block 120 for RPM and torque and block 115 or 005 (cant remember which) to log boost.

I created an excel sheet that converts Nm-lbs, Bhp, mbar-bar & psi, 0-60, 0-100, 1/4 mile etc etc on one sheet by entering the data (done this by chopping up 3/4 xl sheets and combining them into one)

cheers

mike

[m0rk]

RR's measure torque @ wheels then transmission losses (on run down) then add them to get the flywheel figure

VAG-COm measures torque (so I beleive) but I also think that unless you did run down, you have the @ wheels figure. AND - I think 4th Gear is the one to do it in (on a private motorway)

Mark

[BenS1]

Mike, your figures seem very strange.

As Mark said, Rolling Roads measure Torque at the wheels at any one instant. From this you can easily calculate bhp at wheels as bhp = torque * rpm /5252.

Also, as Mark says you can get an estimate of the power at the flywheel by doing a rundown test. The amount of time that the rundown test takes indicates the amount of resistance in the transmission and so knowing this you can adjust the at wheels figures to give the at flywheel figures. This is only an estimate though... it'll never be as accurate as a flywheel dyno.

I believe VAG-COM calculates torque at the flywheel using calculations from a number of inputs, but I don't know for sure.

As Mark says, most Rolling Road tests are done in 4th gear, however technically it doesn't matter what gear you are in as the rundown test should compensate accordingly. Also, 4th gear on one make/model of car could be a completely different ratio to that of another make/model... eg. 4th gear in an Ibiza is roughly equivilent to 5th gear in a 1.2 Clio and a 306 XSi.

Cheers
Ben

[Glenn]

VAG-COM produces ECU-derived Flywheel torque figures in Nm. I've seen four different figures given for conversion into ft/lbs but the most common is 1.357Nm = 1 ft/lb. AFAIK, the ECU derives its torque figure from air-flow (there's a correlation between this and bhp), injector duty cycle and something else that I forget.
Check your spreadsheet maths are correct - the torque (in ft/lb) and bhp figures should be very similar around 5200-5300RPM and identical at 5252RPM. If not, the maths aren't correct.

It shouldn't matter which gear you perform these VAG-COM runs in, the difference being that your relative speed per RPM is lower and this may have an effect on charge temperature - due to airflow over the intercooler. I've done 3rd and 4th gear runs back to back and found that they return results within +/- 3bhp of each other. In practice, I've found it impossible to get to 6500RPM in 4th gear as I tend to run out of road - my car is standard-engined apart from a Milltek 2.5" exhaust.

Try doing a log of charge temperature (block 004) vs. RPM - you may find this enlightening. For reference, my standard car logged 49 Degs C at 6500RPM in 3rd gear at an ambient temperature of 15 degs C. (The curve was similar for 4th gear but I couldn't get beyond 5800RPM).

Finally, if you have your bhp@wheels figures from Stealth, divide them by 0.85 and compare with your VAG-COM results. A genuine 200bhp FWD car should produce around 170bhp @ wheels.

[ibizacupra]

Not sure if this helps you at all, but here are some vag-com dyno runs i did way back when on my own Oettinger'd Ibiza... 4th gear runs

http://www.badger5.demon.co.uk/bin/dynoplot-vagcom2.xls

Note airflow, induction temps & boost in addition to the derived #120 torque output.

mine always came to around high 180's low 190's bhp when vag-com dyno'd.

How do mine compare with yours?

Bill

PS... Maybe the REVO software is fiddling some of the torque block tables so VAG-COM is'nt going to read block #120 accurately any more. (just a thought. My Jabba IHI will not read meaningful outputs now as its a hybrid of parts and sofwtare)

[John]

Originally posted by Shock_Xe
Right... where do i start?? Firstly where do the likes of stealth get their figures from on their RR?? i.e. at wheels, flywheel?? etc

Secondly Where is Vag-com calculating it @ (when using block 120)

The reason i ask is that myself and Andy blunt had our motors Rolling roaded at stealth and bout got around 210bhp. However on Vag com today I got 148 (low 9) and he had 157 (he on high 9) and stevo (leon cupra) got 150bhp. Now all these cars are down on power according to this However torque was 200lbs for myself and andy and a little less on the leon. All the runs were in third from 1,500 rpm (Leon in 4th) (also only got 148 on local RR today, Never got above 164bhp on there!)

Am I doing something wrong?? I used block 120 for RPM and torque and block 115 or 005 (cant remember which) to log boost.

I created an excel sheet that converts Nm-lbs, Bhp, mbar-bar & psi, 0-60, 0-100, 1/4 mile etc etc on one sheet by entering the data (done this by chopping up 3/4 xl sheets and combining them into one)

cheers

mike

Weird one this i seem to get the same sort of results when i have done mine in the past cars running fine though (pulls away from a college's standard 210 S3)



:cheers:

[Shock_Xe]

Originally posted by John
Weird one this i seem to get the same sort of results when i have done mine in the past cars running fine though (pulls away from a college's standard 210 S3)



:cheers:

see u didnt really get more than 160bhp?? Mines about the same on mine anbd Andys, both revo and lowered

[Shock_Xe]

Originally posted by ibizacupra
Not sure if this helps you at all, but here are some vag-com dyno runs i did way back when on my own Oettinger'd Ibiza... 4th gear runs

http://www.badger5.demon.co.uk/bin/dynoplot-vagcom2.xls

Note airflow, induction temps & boost in addition to the derived #120 torque output.

mine always came to around high 180's low 190's bhp when vag-com dyno'd.

How do mine compare with yours?

Bill

PS... Maybe the REVO software is fiddling some of the torque block tables so VAG-COM is'nt going to read block #120 accurately any more. (just a thought. My Jabba IHI will not read meaningful outputs now as its a hybrid of parts and sofwtare)

as far as figures go my working is correct as i copied your results into my tables i made and it is the same, however bhp is still alot lower while torque was comparable (262nm on mine) 266nm on yers. Andys is similar. so aint got a clue except that max torque on yers was high 4s and mine was high 3's

[Shock_Xe]

pic of graph

[max_torque]

Basically the Vag_com torque figure is just a log of the output from the ecu of current engine torque. the ecu gets this number by looking at engine speed (measured by crank sensor) and multipling it by the torque, which comes from a big look-up table that is programmed by the person who did the original calibration. it will modify the base torque which comes from engine airflow, ignition timming, and fuelling, with factors such as oil and coolant temp that effect engine friction. However although when the base calibration is done we tend to ensure that the look-up table will extend further than std operating conditions (ie std boost +50kpa etc.) if you chip your car or modify the hardware (exhaust turbo etc) then this table will no longer be accurate and Vag-com figures will be innacurate.

[slim_boy_fat]

That one mad looking graph

[Shock_Xe]

With the new excel sheet ive compiled it works out 0-60, 1/4 mile, 0-100, kph into mph, mbar into psi and bar. Max boost produced, auto graph on bhp/torque, NM into lbs,

but need help with few formulaes if any1 is good with excel??
Need to work out Power to weight Ratio?? How is this done? what is the formulae for working this??

Also I need excel to search in a field i.e. for 60mph and tell me the time stamp that this was achieved (different column) would would the formulae for this be?? cheers

Mike

p.s. is vagcom at the wheels?? if so how would i work out the fly wheel figure??

thx again

[ibizacupra]

Originally posted by Shock_Xe
p.s. is vagcom at the wheels?? if so how would i work out the fly wheel figure??
thx again

VAG-COM is flywheel

[Shock_Xe]

Originally posted by ibizacupra
VAG-COM is flywheel

bugger that makes the figure really low :( on both Revo cars and the standard leon cupra?? hmm any ideas then???

[max_torque]

In excel either write a little macro to look for the cell contents, or (and i find this easier, but depends on if all you logs will be same length, ie number of cells down) us HLOOKUP or VLOOKUP to search for a value you specify in a range of colums, then return a value in the same row but a different column - see the help file in excel for syntax

Power to weight is usually the flywheel power in bhp divided by the kerb weight in tons, ie 150bhp in 1 ton car = 150bhp per ton, 150bhp in 2 ton car = 75bhp per ton.

Its a bit of a cheat because you have to have at least one person in the car when your moving, and the transmisions looses something like 12 to 15% power, but also long as you use the same formula for all cars it a valid comparison.

(on the pwr to wght front watch out for motorbikers claiming ridiculus pwr to weight figures by conveniently forgeting the riders weight, a BIG percentage on a modern sports bike!)(not that the average sports bike needs any exageration in the pwr to wght front anyway:p )

[Shock_Xe]

how to i convert kgs into ton?? as most ppl's weight and car weight is in kgs??

[ibizacupra]

Originally posted by Shock_Xe
how to i convert kgs into ton?? as most ppl's weight and car weight is in kgs??

I would presume you're talking tonne and not ton...

Tonne is 1000Kg's ie a metric ton(ne)

regards
bill

[Shock_Xe]

Originally posted by ibizacupra
I would presume you're talking tonne and not ton...

Tonne is 1000Kg's ie a metric ton(ne)

regards
bill

when we talk power to weight ratio, do we use tonne or ton??

so would 153bhp get 108 bhp per tonne??

Still dont understand how my figures are so low. This would mean that 2 Ibiza revo Cupra's and 1 leon cupra are only 130bhp at the wheels according to vag com!!!!

[ibizacupra]

Originally posted by Shock_Xe
when we talk power to weight ratio, do we use tonne or ton??

so would 153bhp get 108 bhp per tonne??

Still dont understand how my figures are so low. This would mean that 2 Ibiza revo Cupra's and 1 leon cupra are only 130bhp at the wheels according to vag com!!!!

Forgetting VAG-Com for the moment... do you actually feel your cars are going less well?

Bill

[Shock_Xe]

Originally posted by ibizacupra
Forgetting VAG-Com for the moment... do you actually feel your cars are going less well?

Bill

No definatly not!!! As good and as strong as they have always been! Mine and andy's are exactly the same (0-60 @ SW-CC showed that, Same time down to the decimal point plus during a race nothing in it) I know for a fact its faster than standard as I lost against my bosses 300ZX in standard but in chipped i owned him plus i have beaten 150bhp cars easier where b4 chip i struggled!!

Its just that I must be doing something wrong as both mine and andy's figures are down and guy with standard leon cupra is down and its atleast 30bhp or more so its not as if its a little. Therefore i must be doing something wrong??