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Old 01-18-2006, 04:02 PM   #1
Trunk_Monkey
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Default G-Meters and Tuning

Would one of these be able to substitute a dyno for tuning? http://www.gtechpro.com/rr.html
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Old 01-18-2006, 04:21 PM   #2
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I think it could. I also think logging delta RPM/second or half a second or quarter of a second would do the same thing. Both are based on acceleration measurement.
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Old 01-18-2006, 05:01 PM   #3
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Bump - Any more input?
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Old 01-18-2006, 05:42 PM   #4
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try http://www.dynamic-dyno.com there are quite a few of us on WRXFanatics using the software and the #'s are on target with actual dyno #'s on a dynojet

i have charts in the review section
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Old 01-18-2006, 09:28 PM   #5
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That's pretty cool software. There's a similar one called Road Dyno. The GTech seems like it should work just fine if you can get the data onto a computer. The little screen on the GTech Pro does not seem good enough (lacks resolution).
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Old 01-18-2006, 09:30 PM   #6
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less hardware to mess with than teh Road Dyno & the developer of the Dynamic Dyno Software has a Saabaru
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Old 01-19-2006, 12:39 PM   #7
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The main benifit from dyno tuning is not some bragging number at the end. It's being able to do work on your car off the road (safely) and to be able to put a high amount of load so that it takes longer for your car to rev (thus getting more data at diffrent points during your pull).
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Old 01-19-2006, 01:35 PM   #8
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I'd trust an accelerometer more than I'd trust a Time/RPM log by a longshot. The Gtech uses an accelerometer and the weight you input to calculate power. It logs RPM, but only so it can graph your power against RPM. There are two big problems with logging RPM. Wheelspin, and the quality and speed of the RPM log. To do it, you need a very high speed sampling rate, and each log sample needs to be counter-based so it is representative of the average RPM from the moment of the last sample to the current sample. Most RPM logs jump around too much and are "noisy", requiring tons of smoothing, and the more smoothing you use, the more samples you need to retain precision. I can at least tell you UTEC and SMT-6 logs are not precise enough. The UTEC isn't fast enough, either, although there is a logger now that has "fast logging" ability which may help (haven't tried yet). I don't think OBD/SSM is fast nor precise enough.

With any sort of road tuning you need to make sure you are consistent or you'll never know exactly what changes you are making are really doing. If you can do a full acceleration run in 3rd gear the same direction on the same stretch of road I don't think there is a big proble with doing this.

parid: that really only applies to a loaded dyno. I agree a dyno is a crap load faster. Resetting is faster, consistency is going to be much easier to achieve, you're not out on public roads, etc. It's a much more controlled environment.
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Old 01-20-2006, 12:51 PM   #9
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Quote:
Originally Posted by Freon
that really only applies to a loaded dyno. I agree a dyno is a crap load faster. Resetting is faster, consistency is going to be much easier to achieve, you're not out on public roads, etc. It's a much more controlled environment.
I've actually read alot about this stuff just recently, while a dyno may be more acurate, and easier to repeat with the same consistency, it still is not "Real World" conditions. So while on the dyno everything looks great, on the road may be a diffrent story.

While I know a dyno is the better method, logically it almost seems "Road Tunning" would end up with better results?

I wish I could rember where the artical is that I read about this. It was quite intriguing.


edit - I found the artical - enjoy

http://www.dinancars.com/whitepapersFile.asp?ID=9
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Old 01-20-2006, 12:55 PM   #10
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from SloRice (a Mustang Dyno sales engineer):

Quote:
Originally Posted by SloRice
Quote:
What information do I need to input into Dynamic Dyno? Vehicle weight including passengers, an
estimate of the amount of fuel needed to fill up the gas tank, final drive ratio, gear ratio, tire radius, drag
coefficient, frontal area, air temperature, dew point, and pressure. Some of these values have a very
small effect on the calculated horsepower and torque. Download the user's manual if you want more
information on the effect of the different factors and suggested internet sites for finding them.
It's basically the same thing as a Dynojet. Except the Dynojet doesn't factor in the aerodynamic coefficient of the vehicle like this program does. So this program is probably a little more accurate as long as you enter the correct weight of the vehicle and the aero. coeff.

F=MA
M=weight of the vehicle + areo. coeff.
A= based on how fast your car accelerates

HP=Force*(distance traveled/time of test)
Torque=HP*5252/RPM
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Old 01-20-2006, 12:57 PM   #11
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Oh and while reading up about, all these "dyno" type programs I came accross this spread sheet.


http://forums.audiworld.com/vag/msgs/457.phtml

I'm sure it could easily be modified to work with our cars (and a simple data logger). I dunno how acurate they would be, but the audi guys seem to get good results.
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Old 01-20-2006, 02:13 PM   #12
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Here's a spreadsheet I made up attempting to get HP from an SMT-6 log of time and RPM:

http://freon.shackspace.com/ecu%20an...0worksheet.xls
(go to "Sheet 1")
I used a Delta Kinetic Energy model. I knew my gear ratios, so I can translate RPM into speed pretty accurately. From there, I take the speed * mass of the car to get kinetic energy at each sample, then subtract adjacent samples to get the change in total kinetic energy per sample. Delta Kinetic Energy is a simple factor change into horsepower.

As you can see, it didnt work out too well, even after messing with various windowing functions to smooth the data. There is just a giant spike in the middle, and LOTS of general "noise."

The math is not hard, and it is really easy to come up with an Excel spreadsheet to calculate it. That's not the problem.

The RPM log just isn't precise enough. Either it needs to be counter based (average RPM over sample window), or the sampling rate needs to be drastically increased. A typical RPM log is just too noisy. The car in question was a 2.7L NA with weak cams, which should have about 150whp at 5500rpm and a wide flat torque curve.

Look at a typical log. While accelerating, sometimes recorded RPM actually drops! But either way, they are almost always very noisy. I.e. something like 5015, 5198, 5216, 5304, 5490, 5510 under WOT. It should be much more consistent and smooth. If it isn't, you'll never be able to get a good graph.

The SMT-6 was reading straight off the crank signal of a 60-3 crank wheel. (60 teeth, 3 missing) It logs at 9-12 samples per second to its internal memory. Most other loggers are loggin at an even slower rate. The UTEC is horrible at only 5hz and is still noisy. I haven't tried making it work with a log from SSM (deltadash/ecuexplorer, etc).

Last edited by Freon; 01-20-2006 at 02:20 PM.
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Old 01-20-2006, 02:29 PM   #13
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I belive, thats what is special about the link to the spreadsheet I posted. The person who made it had some sort of smoothing algo that seems to working quite well.

The only thing that sucks about his design is the "coast down".

I'm going to take a look at your spreadsheet, nice to see I'm not the only person who would have an interest in such a thing! I just haven't had the time to really get into it, with the new baby. Gotta love kids
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