Dyno differences between various tuners
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From: Valley Ranch, Texas
Dyno differences between various tuners
First, let me state, I'm not trying to stir anything up, but just state some observations. At the last dyno day in Houston at MTI a few months ago, I Dynoed: 332.3 rwhp 336.3 rwtq. Yesterday, my car was dynoed at UTI on the exact same type dyno machine, DynoJet(??) (but possibly newer software), and I dynoed: 322.9 rwhp 326.7 rwtq. All these numbers are SAE corrected. The only difference between the dyno's (performance wise) is that I added a GMS MAFT. I don't expect I gained more than 3-5 hp from this (which would make the numbers even more off). Sooooo, anybody see anything wrong here?? :confused: or is this common/normal?? What experiences have others had between dyno's??
Drifting
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Re: Dyno differences between various tuners (JWSchmidt3)
Well, at Colvin Automotive last week I dynoed 336 RWHP and 344 TQ. I am going to MTI this Friday to have the T1 cam installed. Perhaps I'll have them dyno it before hand to see how their numbers compare with Colvin.......
Heel & Toe
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Re: Dyno differences between various tuners (JWSchmidt3)
Dynoing your car depends on a lot of factors. One of the largest being weather, just like at the track you can see a lot of differences in your cars performance even if you duplicated your launch and shifts. The temperature was most likely cooler at your first dyno, or your car could have been prepped differently. There are a lot of factors on the weather side. Atmosphereic pressure, etc. Im not a real expert but from my experiences thats what Ive noticed. Hope this helps.
Jarod
Jarod
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Re: Dyno differences between various tuners (jrod278)
I thought that's why it was corrected data. Am I missing something?
Dynoing your car depends on a lot of factors. One of the largest being weather, just like at the track you can see a lot of differences in your cars performance even if you duplicated your launch and shifts. The temperature was most likely cooler at your first dyno, or your car could have been prepped differently. There are a lot of factors on the weather side. Atmosphereic pressure, etc. Im not a real expert but from my experiences thats what Ive noticed. Hope this helps.
Jarod
Jarod
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From: CenTex Texas
Re: Dyno differences between various tuners (JWSchmidt3)
John,
There are many things that influence a dyno run (Outside Temp, Altitude, Humidity, Car Temp, etc, etc), which is why it's a good idea to use the exact same dyno machine and on a similar type of day for each dyno run. Doing this will help give you a more consistent reading and will show a more accurate power gain/loss.
A good example, a forum member from Austin Dyno'ed at Colvin's (in Austin) @ 409rwhp and a two weeks later dyno'ed it again at MTI in Houston @ 418rwhp.
levrac68 - The SAE correction factor is just a "fudge factor" for the dyno numbers by taking into consideration all the items that effect the dyno (like weather). Which is why dyno's vary so much.
[Modified by 97C5ENVY, 9:40 PM 11/6/2001]
There are many things that influence a dyno run (Outside Temp, Altitude, Humidity, Car Temp, etc, etc), which is why it's a good idea to use the exact same dyno machine and on a similar type of day for each dyno run. Doing this will help give you a more consistent reading and will show a more accurate power gain/loss.
A good example, a forum member from Austin Dyno'ed at Colvin's (in Austin) @ 409rwhp and a two weeks later dyno'ed it again at MTI in Houston @ 418rwhp.
levrac68 - The SAE correction factor is just a "fudge factor" for the dyno numbers by taking into consideration all the items that effect the dyno (like weather). Which is why dyno's vary so much.
[Modified by 97C5ENVY, 9:40 PM 11/6/2001]
Le Mans Master
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From: Fort Worth Texas
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Re: Dyno differences between various tuners (levrac68)
I thought that's why it was corrected data. Am I missing something?
One has to remember that the correction factors were setup in carberated days where correcting for differences in the atmposphere effected a car moreso than todays fuel injected computerized motors. In other words todays technology is able to more redily adapt to varying conditions than the days when correction factors were decided upon in the carb. days.
In your case JW, adding the GMS MAF could be its not calibrated just right for your motor with its fixed electronics. You may need some tuning to bring it into line. Or mabey more driving to allow the computer to fully realize its there.
Also, for what its worth, RAT dynoed within a couple of Horsepower between the MTI dynojet, and the Speedworks dynojet up here in Dallas.
[Modified by kewlbrz, 9:30 PM 11/6/2001]
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From: DFW, Texas...2001 Millennium Yellow Z06
Re: Dyno differences between various tuners (kewlbrz)
Also, for what its worth, RAT dynoed within a couple of Horsepower between the MTI dynojet, and the Speedworks dynojet up here in Dallas.
[Modified by kewlbrz, 9:30 PM 11/6/2001]
[Modified by kewlbrz, 9:30 PM 11/6/2001]
as for SAE correction, the computer can correct for bad air but it cannot figure the amount of loss by burning hotter less dense air figuring the same amount of fuel is dumped in ..... IMHO....that is just me thinking outloud, but you are going to have a slight variation from dynojet to dynojet....also, the ones with a weather station hardwired right to the computer dont have a HUMAN error factor....some have a little mobile weather station that they have to ENTER the data into for the correction.....THAT can account for ALOT of difference
just my $200 ( i aint cheap ;) :lol: ) hehehehehhehehe
thanks
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From: Orange California
Re: Dyno differences between various tuners (JWSchmidt3)
JOHN
I FEEL LIKE THE NUMBERS ARE MORE ACCURATE AT UTI THEN MTI, THE #S AREN'T ADJUSTABLE WITH THE NEW SOFTWARE. IM ME AND WE CAN TALK
PAUL
I FEEL LIKE THE NUMBERS ARE MORE ACCURATE AT UTI THEN MTI, THE #S AREN'T ADJUSTABLE WITH THE NEW SOFTWARE. IM ME AND WE CAN TALK
PAUL
Melting Slicks
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From: ATLANTA/HOUSTON
Re: Dyno differences between various tuners (COH PAUL)
I have to agree that it "MAY" actually be the GMS MAF that has caused you to lose some power. When I had my computer reprogrammed at Ed Wright's. One of the questions he asked me was if I had the stock MAF or one from GMS. When I told him that mine was stock, he said that was good because the MAFs he had seen from GMS we not consistent at all in the way they were calibrated. He said that no 2 that he's seen were alike, I don't know all the details about how this would affect the stock computer. Just food for thought.
FYI, I still have my stock MAF on my car, sans the screen. It works fine for me.
FYI, I still have my stock MAF on my car, sans the screen. It works fine for me.
Race Director
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From: Bonneville Salt Flats
Re: Dyno differences between various tuners (COH PAUL)
You expected a 3-5 hp increase!? The error of measurement is greater than that, meaning you could dyno an identical car on identical equipment under identical conditions and get a bigger difference due to chance.
Many seem to have a faulty idea of the accuracy, or lack there of, involved. In fact, the dyno man who used to do our comp engines was quick to note that he could "make the dyno" produce whatever he wanted it to, if he were unscrupulous. It makes sense from a marketing standpoint, then, to turn-out figures on the highside for "paying customers." Bottom line--if you wish to do before-and-after testing, at the least, stay with the same dyno! :yesnod:
[Modified by Avanti, 10:28 PM 11/6/2001]
Many seem to have a faulty idea of the accuracy, or lack there of, involved. In fact, the dyno man who used to do our comp engines was quick to note that he could "make the dyno" produce whatever he wanted it to, if he were unscrupulous. It makes sense from a marketing standpoint, then, to turn-out figures on the highside for "paying customers." Bottom line--if you wish to do before-and-after testing, at the least, stay with the same dyno! :yesnod:
[Modified by Avanti, 10:28 PM 11/6/2001]
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Re: Dyno differences between various tuners (Avanti)
John,
Tire pressure can also change dyno numbers. I haven't seen anything really positive about the GMS product on the Forum here. Mayeb MAF tuning would help.
RG
Tire pressure can also change dyno numbers. I haven't seen anything really positive about the GMS product on the Forum here. Mayeb MAF tuning would help.
RG
Safety Car
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From: Albuquerque NM
Re: Dyno differences between various tuners (JWSchmidt3)
Ignoring the possibility that tuners will give their customers a "home field advantage", because I think most are honest, there are still valid reasons why readings will differ. Even with an accuracy variation of only 1% (VERY GOOD) the same dyno could give 3-4 HP difference , same car, same day, same weather. The PCM "learns" as you drive, and not to give best HP, but to give lowest emissions, with the gas you give it and your driving style. The GMS may not be calibrated best for your car. I agree that a 10 HP drop is disconcerting especially when you are expecting a gain, but there are too many variables to say why the reading was lower. Consider: I dyno'd mine at MMS at sea level, on a warm day, got 412.7 sae rwhp. Redyno'd at 5,000 ft on a hot day, and got 399. BUT the a/f was rich, we adjusted it (gotta love the MAF-T!) and got 409. Well within the margin of error. But I'll post the 412 reading! :D
Race Director
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From: DFW, Texas...2001 Millennium Yellow Z06
Re: Dyno differences between various tuners (6Speeder)
JW....I missed the GMS MAF part.....DUMP that thing......I use stock maf on my head cam car like Darth mentioned above....
between here and LS1.com I have read very FEW positive things on that mess
get a refund and send the car to MTI :)
thanks
R
A
T
between here and LS1.com I have read very FEW positive things on that mess
get a refund and send the car to MTI :)
thanks
R
A
T
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Re: Dyno differences between various tuners (Ram Air Tony)
Results like these are why I never put too much emphasis on comparing one tuner's dyno numbers to another. There is no PERFECT comparison in life for the power a car has. Sure the track is a great place to compare as well but there are even MORE variables at a track than there is on a dyno.
I do agree though, the GMS MAF could quite easily rob some power from you. If you were already running a bit on the rich side and added it, you could now be running VERY rich.
I do agree though, the GMS MAF could quite easily rob some power from you. If you were already running a bit on the rich side and added it, you could now be running VERY rich.
Burning Brakes
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From: Morganton, NC, USA
Re: Dyno differences between various tuners (MattG)
Correction factors for air temperature, air pressure (barometer) and humidity exist so that identical runs at different atmospheric conditions can be equated. With a computer controlling a dyno, it is a simple matter for it to apply these factors giving "corrected H.P." These factors come from the principals of thermodynamics and are accepted as "gospel." It would be very interesting to see if someone actually tested the same engine on the same dyno with wildly varying atmospheric conditions to verify the correction factors. Furthermore, if there were any differences in oil temperature in an engine between two dyno runs, like if the car sat for a couple hours one time and not the other, there could be a significant difference in HP. Lastly, with the ability of the cars computer to monitor operation and adjust fuel and timing, and the amount of running time it takes to "adjust", I don't know how one could get a good answer by simply making adjustments (with parts) on a dyno. :confused:
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Re: Dyno differences between various tuners (2kbluestreak)
Lastly, with the ability of the cars computer to monitor operation and adjust fuel and timing, and the amount of running time it takes to "adjust", I don't know how one could get a good answer by simply making adjustments (with parts) on a dyno. :confused:
For example, you can change WOT frequency adjustments on the MAFT because that is used during WOT operation and is immediatly realized. You cannot however change base settings on a MAFT since its used throughout the range and where the fuel trims are updated via the O2's because there needs to be time for the fuel trims to adjust to the change in closed loop.
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From: Valley Ranch, Texas
Re: Dyno differences between various tuners (kewlbrz)
Thanks for the responses. I am very aware that various weather indicators can cause differences, hence: SAE correction. You would think that rwhp values would be relatively similar with the SAE correction, but yes, I realize some dyno "operators" have a "fudge factor". I think most operators are honest, but believe multiple runs on different dynos at different shops are a good thing. I should (will) have my "package" done by Thanksgiving, so I'd like to get a dyno done at Speedworks and/or maybe LG Motorsports (since I'm in Dallas). Can anyone hook me up?? RAT?? Maybe a DFW dyno day?? When I'm back in Houston (at X-mas), I'll probably hook up with MTI and get a dyno from them too. Then I'll have 3 sets of numbers. Also, I'm about 90% sure I'll be losing the GMS MAF. It doesn't seem to be a problem, but neither does it seem too advantageous. :cheers:
Team Owner
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From: Spring Texas
Re: Dyno differences between various tuners (JWSchmidt3)
John,
I think you may be caught up in repeatability versus reproducibility. The repeatibility is the measurement deviation for the same operator on the same piece of equipment. The reproducibility is for different operators on different equipment.
I don't know what the specs are for the repeatability for dynos but I would expect it to be a big number (just a hunch). Your numbers are 3% different (albiet unexpectedly lower, as you mentioned).
I would guess that even the expected increase in the numbers you expected with the GMS MAF are within the repeatability of the equipment.
In other words, the increase is there but you can't measure it.
I think you may be caught up in repeatability versus reproducibility. The repeatibility is the measurement deviation for the same operator on the same piece of equipment. The reproducibility is for different operators on different equipment.
I don't know what the specs are for the repeatability for dynos but I would expect it to be a big number (just a hunch). Your numbers are 3% different (albiet unexpectedly lower, as you mentioned).
I would guess that even the expected increase in the numbers you expected with the GMS MAF are within the repeatability of the equipment.
In other words, the increase is there but you can't measure it.