Why is it that we are seeing such wide variations in dyno numbers (from the same car with no changes in many cases) between different dynos.

From Roger:
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well i have always dynoed my car at mti because they are nice guys,very professional and have always treated me well but being i had a mustang they couldnt tune my car so i took it over to houston performance and had it dyno tuned.

Here are the numbers:

mti=408rwhp,392rwtq

hp=381rwhp,367rwtq

this is a good reason to try not to compare numbers unless they are on the same dyno.
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Same mods, same car, different dyno 30RWHP less than at MTI's dyno.

Another example from uptolate76 post:
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the numbers: 390 HP/ 372 TQ
the parts: thunder racing stage II'2 w/ tr224 cam-114 lsa.
the other mods done to car: FLP headers/ corsa cat back/ SLP lid and filter.
3.42 gears, M6. Mail order tuning from thunder.

Most Thunder cars that dyno at Thunder make 420-440RWHP with this identical package on STOCK tuning in many cases.

Another example this one Cartek:
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cartek stage II heads and H cam on it and C5R timing chain
375 to 385rwhp and 400 torque thru A4 with 3500 and 4000 stall on it and 3.42s
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This package at Cartek typically dynos 400-420RWHP through an A4 unlocked.

Why are these variations occuring? Why are we seeing such wide discrepancies in power when the cars all run within 1 tenth and 1mph of each other in MANY cases. Cars with similar gearing, raceweight, tranny type/converter type, etc etc.

Are there differences in the weather correction factors within different versions of the dynojet programs? Or some other parameter (user defined or built in) that is different between these dynos that we dont yet understand or have not figured out yet...

I'd like to find out what version of dynojet software different shops are using. Maybe there is something different within the program itself or some variable that is set/turned on or off that affects these numbers.

I am NOT and I repeat NOT suggesting people or shops are lying or rigging dynojets. I am trying to understand why these variations occurr with the same car with no changes in mods!

The cars all run very close to each other, ET/mph at the track is VERY close between different cars but you are seeing dyno number discrepancies of 30-50RWHP!!! OFTEN ON THE SAME CAR!

Your thoughts and opinions are appreciated and again I dont want this to turn into a flame fest.

cheers,
Chris

<small>[ November 04, 2002, 06:46 PM: Message edited by: Chris ARE 360 ]</small>

 

The shop can change the altitude only on a dyno-jet.be interesting to see what they are set at huh.
My car made 346 rwhp on a mustang dyno! yet runs 7.20's in the 1/8 in a 3500 lb car

 

I feel some of the difference lies in the way each dyno is maintained and how often it is maintained. Some shops may lube their dyno more often than others. Some may also use synthetic grease versus another shop who doesn't even do any maintainence. I was told my car put down sub par numbers with what I have done, and from other locals, I have heard that the dyno I use is a little on the low side, who knows. Maybe some shops just have a newer dyno than others who may have bought them 2 years or so ago?

 

Correction factors can be altered. Weather ( humidity, temperature, etc) plays a big part as well.

As long as you see gains when you tune who cares what numbers the car pulls , I use the dyno strictly as a tool to measure before and after mods. The real test is to take to the track and see what she runs. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

What I meant to say but forgot to include in the above post was the dyno is a measuring tool to use when you are tuning, as long as you show gains that's all that's important! <img border="0" title="" alt="[Razz]" src="gr_tounge.gif" />

 

as stated above...

https://ls1tech.com/ubb/ultimatebb.p...c;f=1;t=008723

one persons find??

I agree all dynos to be different. I really do think a lot of guys also show they're higher #'s also not the corrected ones...but if one guy is comparing one and the other a different correction factor there is/can be big differences.

 

I have dynoed at three different places: Cartek, JD's auto repair, and Performance Specialties. From my experience, those three are relatively close to the same, despite my belief that performance specialties is a little low (5-8rwhp is what seemed to be the number), but Cartek and JD's seemed about the same. Ive dynoed at each place at least 7 runs each. Modifications going from one dyno to another yielded about the expected numbers (usually on the low side though).

Ive also raced at 7 different tracks, and I can tell you the variance from track to track and day to day is much, much greater then differences ive seen in dyno numbers from dyno to dyno.

<small>[ November 04, 2002, 08:47 PM: Message edited by: ezss ]</small>

 

A little thing called error. There is no standard for dyno measurement...For example, At our Lab we use ISO-9000 standards which are traceable to a known certified standard. This method actually relates our machines to others across the globe to a certain extent (limited error still exists). A 30rwhp error on a 410rwhp engine is only 7%, not bad actually, but who's to say one of said dynos is off 7%. Both dyno's could be off 3.5%, the sum of the errors comes up to 7%. Again not bad.

<small>[ November 04, 2002, 08:49 PM: Message edited by: cantdrv65 ]</small>

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by cantdrv65:
<strong>A little thing called error. There is no standard for dyno measurement...For example, At our Lab we use ISO-9000 standards which are traceable to a known certified standard. This method actually relates our machines to others across the globe to a certain extent (limited error still exists). A 30rwhp error on a 410rwhp engine is only 7%, not bad actually, but who's to say one of said dynos is off 7%. Both dyno's could be off 3.5%, the sum of the errors comes up to 7%. Again not bad.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">They are supposed to be corrected to a standard using a standard error correction, so this is not really true. Thats what 400rwhp SAE means, for example. Maybe some shops are posting uncorrected numbers, is that what you meant?

 

No I dont think it has to do with posting STD vs SAE numbers.

I think it is in the correction factors within the software. SW versions would really help in this and what altitude they put in for their location.
cheers,
Chris

 

Exactly what EZSS said. Most all of these guys that post dyno #'s are uncorrected dyno runs. Thats great is you want a glorified dyno sheet, but is not consistant. You can have the same car make 30 hp different in temp change and altitude. This is why you should always have corrected runs to compare to each time you make another mod. Otherwise you really dont know where you are, as far as gains.

 

Two things that I know will alter hp readings (SAE Corrected) between dynos. 1. The location of the temp,alt,hum sensors that correct to SAE...if they are placed high on the wall in a "hot spot" the corrected hp will be higher than a shop that places the sensors nearer to the actual inlet air temp.. 2. The SAE CF is only accurate in a narrow atmospheric range. I.E. run car A on a dynojet in -2000 DA at 40 degrees F and retest car A in +2000 DA 95 degrees F and the SAE corrected HP will be WAYYYYY DIFFERENT for the same car. The latest dynojet software does not allow altitudes to be inputed. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

This is why I don't put too much stock in dyno numbers . The same goes for head flow numbers. I'm not saying anybody is fudging the numbers, just that the only way to tell if brand X H/C numbers are better than brand Y H/C numbers is to dyno the cars on the same day same dyno. Differences of 10-15 hp can happen on different dynos. I think ET, race weight, trap speed, and DA numbers might be a better formula for comparing apples to apples. Car setup plays into this as well. If my car with the same setup as someone else dyno's 10 hp less on a different dyno I'm not going to sweat it. If it does on the same dyno than I would check my car closely. Just my .02 <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />

Bruce

 

CHRIS ARE 360:

Simple answer to my quote about my cartek stage II heads and H cam making between 375 to 385 rwhp thru my 98 A4 C5 with 3500 stall and 4000.

Explanation for this is simple, my heads and cam were purchased 16 months ago from Cartek and ARE NOT THE X PACKAGE which is out now and kicking **** and putting out 400 to 420RWHP on a A4. Different heads and cam packages here big time and mine unfortunately are not nearly as aggessive as the X PACKAGE which has now put 2 cartek M6 C5s into the high 10s and several in the low 11s

MTI 422 Z07 ROADSTER

 

i own a portable mustang MD250 dyno...operator error can enter the picture too! not long ago i visited a shop during a test session,the car was being strapped down so tight i couldnt believe my eyes! where did the guy think the car was gonna go? that night i came home and put my corvette on my dyno and made some passes...when i strapped the car down tight in the back i ate up about 15 rwhp. this is a car that i use for my dyno mule...i know what to expect everytime i run it. as long as you use the same dyno,operator and testing procedures you can expect good repeatability...have a great day <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by RAMBIRD2002:
<strong> Most all of these guys that post dyno #'s are uncorrected dyno runs. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I really hope you are joking, because I've always used SAE corrected numbers, and thought everyone else did as well. <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Most of the people that post their dyno sheets for proof have SAE correction on the right hand side of the dyno sheet, at least from what I've seen. I doubt they are photoshopping that there <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" />

The only fishy thing I've ever seen is MM&FF posting their dynos using STD correction vs. SAE correction. Its very misleading and most people don't realize it shows more horsepower being put to the ground compared to SAE correction.

 

What irks me is that not everyone is up front with how their car is setup on their dyno runs. A lot of times it has to get prodded out of them. <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" />

Everyone's dyno setup is different. I personally don't change the car one bit from how I drive it on the street. Others however choose to add headers extentions, run open headers, do the short belt mod, use 30 box fans funneled into the intake, or whatever suits their fancy.

I always go to multiple dynos to verify. There are 3 main ones I go to, all dynojets. The all are always within 5rwhp.

I have noticed discrepancies on a few occasions. On one dyno I ran a 440rwhp figure with only 388rwtq, while on another dyno I ran 440rwhp/401rwtq. Same hp, but the tq differed. 12rwtq seems like a lot, but its only a 3% difference.

The one thing that really made my numbers fluctuate was detonation. For those that don't use ATAP or a Tech II, and don't have a keen eye to notice timing being pulled on the dyno graph, may not realize they are down 20+ rwhp from excess knock retard turning down timing.

I think there are too many variables to expect dyno figures to be consistant between cars.

When comparing dynos on similarly modded cars you have to consider the following:

1. Temperature outside (although it is accounted for you will dyno more on cold days vs super hot days)

2. Altitude programmed into the dyno

3. How well the dyno is maintained

4. What dyno friendly tricks are being used (high psi in tires, shortbelt, open headers/header extentions, no catback, open airbox, tons of air from fans, etc.....)

5. How tightly the car is strapped down on the dyno

6. Is the car tuned well, or tuned at all?

7. Knock retard? Less timing?

8. Dyno error

9. Correction factors used if any


And the list goes on and on, but you all get the idea.

Just my .10 <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

<small>[ November 05, 2002, 04:58 AM: Message edited by: verbs ]</small>

 

Who cares?...lol. Let's go to the track and race. Then we can compare these dyno queens. Hell, my 2 year old heads and cam setup made 414 rwhp and ran 123+ mph at 3500 lbs and an A3. There are dyno queens here with said 440+ rwhp not running those trap speeds. My current set up runs 486 rwhp on the dyno and runs 135+ traps. A dyno is a tuning tool period.

It's all a marketing game guys. The fact is that dyno numbers sell product. We don't play that game.

I suggest that when you purchase a modification, use the same dyno before and after and look at the gains, not the actual number.

My .02

Mikey

 

Kinda funny you mention this Chris. 440 rwhp 346 LS1's are merely a myth here in Georgia. There have been 100's of heads/cam LS1's to roll out of our shops with MTI/Thunder/Cartek/etc parts, and we haven't seen one yet make even close to 440. Cars make good power in GA, but not like the magical #'s you see posted on here.

FWIW, we had a car come from a VERY well known shop(won't disclose who), and made 55 rwhp less than what it made at their shop with no other changes. Things that make ya go hmmmmm <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Josh

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by ezss:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by cantdrv65:
<strong>A little thing called error. There is no standard for dyno measurement...For example, At our Lab we use ISO-9000 standards which are traceable to a known certified standard. This method actually relates our machines to others across the globe to a certain extent (limited error still exists). A 30rwhp error on a 410rwhp engine is only 7%, not bad actually, but who's to say one of said dynos is off 7%. Both dyno's could be off 3.5%, the sum of the errors comes up to 7%. Again not bad.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">They are supposed to be corrected to a standard using a standard error correction, so this is not really true. Thats what 400rwhp SAE means, for example. Maybe some shops are posting uncorrected numbers, is that what you meant?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">NO, they are not related to one another by ANY standard. A standard for example, would be the same car set up exactly the same way measured on each different dyno under the SAME conditions. While there is a correction factor for atmospheric conditions it does not account for all the error that can be introduced. Too many variables exist. As Mickey said, a dyno is a tuning tool, and internet bench racing means very little at different loctaions on different dynos.