DIY VAGCOM Road Dyno

[A4Ade]

Hi,

I thought I'd have a go at producing a horsepower/torque curve using the logged RPM and speed data from VAGCOM. The thumbnail below shows my first attempt, which for anyone that's interested was created in IDL using code based on andy@ross-tech's 'Butt-Dyno'.



It wasn't exactly done under control conditions - the road was a bit hilly and I was only in 2nd gear (I've read that the higher gear you can use the better). I also estimated the car's mass a bit crudely: I found a kerb weight of 1491 kg on the web, and added 90 kg for me. That being said, the car's a 1.8 T 163, so it's not exactly far off. I'll try again at the weekend.

If anyone has any logged data, or would be willing to log some and let me have it, I'd like to run some more data through the code, especially if you've also had a professional dyno done so I have something to compare to. I basically just logged Engine Measuring Block 5. Any comments welcome - I don't really know what I'm doing

Cheers,
Ade

[paul b]

I could do with some instructions on how you did this... I'm interested in finding out if my 1.9 TDI has been re-mapped in the past. It flies!

Paul

[A4Ade]

I could do with some instructions on how you did this... I'm interested in finding out if my 1.9 TDI has been re-mapped in the past. It flies!Paul

That's essentially why I did it - the dealer I bought my car from said it had been remapped but when I asked for documentation to show it he backtracked and said he'd been mistaken. I'm still not certain - I either did a very accurate job of measuring 163, or a really bad job of measuring 190! Still, it's worth a go - if you're interested here is what I did:

Connect the laptop, run VAGCOM and set it logging Engine Measuring Block 5. This was for my A4, it might be different on a different car, but basically you need RPM and Speed. If possible log both of these on the same block though - initially I used two different blocks, but then you get two different sets of timestamps which slightly complicates matters.

Set the laptop up not to sleep when the lid is shut, then close it and put it behind the drivers seat so the cable is out of the way of the pedals! Exactly what you do is up to you, but obviously you need to make sure the laptop and cable are not in anyway hampering safe driving!

Set off, and find a reasonably straight road with no traffic (I did a few "0 to 60"s where I could safely and legally do so while I was at it )

Now, ideally you would want an unrestricted bit of tarmac off road somewhere, so you could do nice controlled runs in 3rd gear. However, I had to make do with a quiet back road, so was limited to 2nd gear (to avoid breaking the speed limit) and the road wasn't completely flat either, which will have had some negative effect on accuracy, but you get the picture.

So, to begin, change up into whichever gear you are planning to use as early as you can, and then floor it. Keep it floored until you hit the rev-limiter, then disengage the clutch (and the throttle) and just coast. This will take a lot longer than the acceleration part, obviously, and if other cars appear you may have to abort to avoid holding them up, but ideally you want to coast until your speed drops to the speed at which you first engaged the gear you are in.

You now have the data you need to calculate power and torque curves, assuming you know what the weight of your car. This might actually be the tricky part, but I guess the standard figures for your car's weight shouldn't be that far off. Then add your own weight (and I guess I should have added something for the fuel in it too!)

I read up on how to do this here. Once you've your logged data (as a ".csv" file which is what VAG COM saves it as) then I'd be happy to run it though my code and produce your graphs if you'd like. If you want to use the spreadsheet then you're on your own because I've not used it. Or I guess you could email andy@ross-tech who wrote it.

If you do log some data, I'd appreciate it if I could have it either way. If you get it dyno'd elsewhere it would be good to have something to compare my results to!

Ade

[dansansome]

i will be doing exactly this procedure very soon to see if my car is remapped or not. i have the dynoplot.xls set up with the weight of the vehicle+me+laptop(every little helps)+fuel

parkers website is a good source to find your vehicle weight (as quoted by manufacturers)

and i managed to work out that petrol has a density of 1.625lb/litre which will hopefully make the vehicle weight (and therefor bhp) a little more accurate, seeing as a full tank of fuel is nearly 114lbs!!

my laptop weighs around 6.5lb for anyone who wants a basic weight.

[Charlies Online]

Not a bad thread of information for us all; I'll have to have a go later.

Thanks for posting

[phatso]

I will log some data for you, i was just wondering how much power my mapped up S3 is putting down when i came across your post.

Im gonna have to try and find somewhere long enough to do the runs, as costing back down from speed does take some time.

When i take this car on a propper set of rollers i will log in vagcom as well and see how acurate the calculations are.

Could you let me know how you created the graphs from the logged data?

[A4Ade]

I will log some data for you

Cheers!

When i take this car on a propper set of rollers i will log in vagcom as well and see how acurate the calculations are.

That would be great. I currently have no real idea how well my code is doing, other than (a) it does a very similar job to Andy's Butt-Dyno and (b) seemed to return close to my car's 163.

Could you let me know how you created the graphs from the logged data?

I basically followed the technique which I linked to in my post above (#3). I doubt I could do a better job of explaining it than Andy did!

[phatso]

I have just logged some data for you, i have tried putting it into the butt dyno spreadsheet but it wont draw the graphs for me.

I have attached the csv from my logging session, there is a lot of random data in there as i was doing some test logs while i drove out to the long straight i used for the runs.

I did 2 3rd gear runs upto 6k rpm in the S3, One each way down the same straight. If you could let post up the graphs after working them out that would be great.

The S3 is running 20psi with a MBC with a full custom remap, re circ valve, air filter and miltec full system with sports cats.

Looking at the logged file it says i was only using part throttle even though i was sure it was flat on the floor, I might re cailbrate the TPS, (throttle)

I think the 1st run is roughly lines 1325 to 1555 and the 2nd run is line 1602 to 1793

[phatso]

Well i got some data out of the butt dyno spreadsheet, i have attached a pic showing the graphs.

Its a little lower on HP than i was hoping for but then its not the best power graph and the logging says the ecu was not reading full throttle either.

[phatso]

I have sorted the data from my second run and added them to the graph, The 2nd run seems to be a lot more like a normally aspirated engine.

I will have to do some more runs to get an idea of the power the S3 is running.