How to Dyno for FREE*

[wolfsburg_de]

http://andy.swankmonkey.com/vwfiles/tdibutt.xls

That's a second gear pull. Find a straight, flat road with no traffic. In a TDI, log Groups 005 and 006 simultaneously as you do a full throttle run from idle to redline in 3rd or 4th gear. At redline, push in the clutch and allow the car to coast as far as possible.

Crunch the data on your own, or send it to me.

* Requires VAG-COM

 

[AtomicSushi]

I know 20V guys do block 120 dynoes or something like that. I couldn't find anything like that when fooling with my vag-com the other day...I guess I didn't look hard enough.

 

[VelvetFoot]

Well, I might actually try this myself!

If a 3rd or 4th gear pull is advised, why the pictured 2nd gear? Wouldn't going from idle be a little hard on things? And one more...why the coasting from red line? Thanks.

 

[wolfsburg_de]

Hojo,

Block 120 is possible on 1.8T's since the ECU is constantly calculating load, which is torque in Nm. The TDI engine management does not have this exact type of calculation.

VelvetFoot,

The person who did this run in his TDI didn't obey the instructions.

Realistically, power is pretty much spot on, even in 2nd, but torque peak is a lower number at a higher RPM due to the time it takes for the turbo to completely spool. The reason for the coast down is to measure the power being used up by the road (air drag, rolling resistance, bearing losses). This way, you get a true power at the wheels figure.

BTW, this is the exact same type of measurement done by a DynoJet, only in this case we use the vehicle's mass instead of the mass of the rollers.

 

[**DONOTDELETE**]

How do you get a printout from your "butt" dyno?

 

[wolfsburg_de]

Toilet paper?

 

[AtomicSushi]

"Wouldn't going from idle be a little hard on things?"

Surge, anyone?

-H

 

[wolfsburg_de]

You can use any start or stop RPM that you want, but most people are interested in a full-range plot.

 

[AtomicSushi]

Coolness.

So, is the number crunching straightforward or will I need data like current vehicle weight and gear ratios?

 

[wolfsburg_de]

You'll need an accurate vehicle weight with you in it. Other than that, all of the number crunching is relatively straightforward. I can help with the decel curve calculation.

 

[Stealth TDI]

Hi,

Was this done on a STOCK TDI? Also, why is SMOOTH info plotted? Would the other plot be to jumpy to read?

 

[wolfsburg_de]

I believe this TDI has some sort of tuning box. The smoothing is used due to rounding of speed done by the ECU. You can change the plot to see the raw data.

 

[Gary Miyakawa]

I sure hope it didn't have a tuning box..... Poor numbers if it did....

Is it fair to say, if we use the same "weight" all the time, and the same road location, we should be able to determine "added" HP when we do make changes ??? (even if we don't have the exact correct weight?).....

Also, if we start at say, 60 mph in 4th (about 2700 rpms) and roll out to red, should the spreadsheet be able to handle it ??

Also, If we have a way to get "more" datapoints than VagCom currently can supply, can we use it instead ??

Thanks,

Gary M

 

[wolfsburg_de]

Gary,

Yep, you can definitely change the start and stop points and log whatever you'd like. I sometimes like to do a "Sanity Check", simply change in RPM over time, without respect to mass, drag, etc. It should show actual before and after acceleration.

... and as long as you are logging stuff, do a shiftpoint analysis as well.

 

[acktdi]

How would I apply this to an automatic transmission? Shift to neutral for deceleration?

 

[Davin]

Andy, glad to see that you're getting people to use this.

This is a fantastic tool... and I think that Gary M.'s comments are spot-on. If you're making mods and want to see the effects, this is a fine way of evaluating effects!

 

[wolfsburg_de]

acktdi,

I honestly don't know how much is going on inside an automatic when it is in neutral, but I wouldn't be comfortable messing with an auto like that.

Davin,

Thanks, as Eric says, this is the free product I keep trying to get people to buy.

 

[Gary Miyakawa]

If I don't care about the "decelleration" time, can I just "zero" it out ??? or set some constant in there ???

Gary M

 

[wolfsburg_de]

You can ignore the decel part, but remember that power-sapping drag is still there, you're just ignoring it.

You can either alter the equation to take into account only the acceleration, or (a better idea, IMHO), just use the deceleration curve in the example chart. That way, you'll get consistent before and after results, with a reasonable estimate of actual power.

 

[Gary Miyakawa]

Hmmm... tried that... numbers went wacko... I've also got about 2 times the data points you have.... I noticed the formulas change as they go down the line (some change to averages)... not sure the best way to "extend" them to fit my datapoints.

Still playing....

Gary M

 

[wolfsburg_de]

Gary,

Feel free to send me your data. Remember, this run was done in my car in 2nd gear. It only takes a about 7 seconds to go from idle to redline in 2nd.

 

[MistralVR6]

Tried block 005 on my 2000 VR6 but I cannot figure out how to calculate the deceration time ... your spreadsheet seems to have numbers in the 100's and decreasing ones. I dont have any such data

Is it because I have a VR? This is what the data looks like

Time RPM Load% km/h
0.01 1920 32.3 27.5
0.40 2000 56.4 27.5
0.81 2240 71.4 30.0
1.20 2520 76.7 33.8
1.60 2840 80.5 37.5

[ September 24, 2002, 19:36: Message edited by: MistralVR6 ]

 

[wolfsburg_de]

Did you do a coast down?

 

[aaron]

This is the coolest thing I have seen in a long time. I'm excited!!! I couldn't get my wife to see why it was so cool, but I'm sure my buddies at work will understand.

I did a third gear run last night, but I want to do a couple more before I post a graph. So far:

Torque: 174 @ 2562
HP: 105 @ 3468

I left the weight at 3100 LB. Anybody know what a 2000 Golf GLS should weigh? And are these calculations supposed to be WHP, or at the flywheel?

(edited to fix spelling stuff)

[ September 25, 2002, 09:27: Message edited by: aaron ]

 

[SilverBullet]

wolfsburg,

can you quickly bring me up to speed as to how you're calculating hp and torque. i was trying this last night in the following manner.

take the log file using blocks 5 and 6. calculate power by calculating the change in kinetic energy over the change in time.

dKE/dt = Power

i came up with figures that were believable, but not great. i need to try the run again.

is the above a good way to do the calculation? also, what about torque?

tips are appreciated.

hans

 

[wolfsburg_de]

Velocity = Speed and direction
since we are going straight, Velocity=speed
V is in km/h

Potential energy is constant, at least as far as gravity is concerned, since we are not on a hill

Kinetic energy is 1/2*Mass*Velocity^2

KE=0.5mV^2

Mass is in kg (0.454 kg per lbm)
Velocity is in m/s (0.278 m/s per km/h)

KE is in Joules

Power is change in KE over time

P = (d/dt)KE

or

P = (KE2-KE1)/(T2-T1)

In units, Joules/s is Watts. (0.001341 Horsepower per Watt)

So, at each moment in time, as dictated by the timestamp during the acceleration run, we have Kinetic Energy. The change between any two points is Power.

Here's where the magic happens. During our acceleration run, we were accelerating the car's mass and seeing the results. But, we were also using power to overcome air drag, rolling resistance, etc. The way we account for this is the coast down. During the coast down, we are encountering the same air drag, rolling resistance, etc but instead of overcoming it, we are letting it slow us down.

By measuring the Power being used by drag forces to slow us down, we know how much extra power we used during our acceleration run. Using the GROWTH function in Excel, we can plot a decelleration curve, and more importantly, we can plug in discrete X-values (the velocity values for each timestamp in the acceleration run) to come up with timestamps for the decelleration that match up.

 

[Gary Miyakawa]

Andy,

Did you get that file I sent you ???

Just curious...

Gary M

 

[GeWilli]

the weight issue seems to be the biggest problem - just putting an extra 15 gallons of fuel in there (8 pounds per gallon?) 120 pounds . . . pretty significant no?

even 100 pounds changes the values pretty significantly.

 

[Boundless]

GeWilli, can you estimate the fuel load when the run is performed with your fuel gauge?

 

[wolfsburg_de]

100 lbs looks to make about a 5whp difference.

Gary, I have your data, but am still scratching my head.