# anyone ever had problems on "dyno dynamics" dyno?



## Ugly_Dub (Mar 19, 2003)

Like the title says... I tried to have my car dynoed again. This is the 3rd time it has been on a dyno. The first 2 were on a dyno jet. Last time the car dynoed at 367hp. Never had any problems at all. This time though I could not get any consistent runs and the highest was 292hp run. The worst being a -2.4hp. haha.. Now The operator is telling me that there was nothing wrong with the dyno and that it is my car that has something wrong with it. Now to me it seems a lot like operator error. While I was making my runs in 3 and or 4 gear. He would hold me at 2000 and the once I was stable I would run it to redline. But the car would bog down really bad at first then would finally go screaming up to about 4500 and just stop... Now last time I was on the dyno I did not have any problems with it doing this. It would not bog down nor did it just stop at 4500 rpm. It went all the way to redline( around 7000rpm) Now I dont know tons about dyno's and I do realize that this is a different type but with bigger injectors and better software I should have atleast seen close to the same numbers. Now what Im thinking is that the load factor is way to high. Can anyone shead light on the truth to this? or any info? thanks


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## scharged (Sep 9, 2004)

dyno dynamics reads a LOT lower than dynojet first of all
second, was your car actually stopping at 4500rpms, or was the dyno only reading to 4500?


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## Ugly_Dub (Mar 19, 2003)

*Re: (scharged)*

Yea I expected it to read lower or higher... but a drop off of over 100 hp when the car have been upgraded more? just seemed a little unlikely. As for the rpm's. In 4th gear it stopped and in 3rd it stopped at 6000. Not a problem on the road driving around nor when I was dynoed last time..


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## tdogg74 (Mar 1, 2002)

Here's the first mistake you made...switching dynos. If at all possible, ALWAYS stick with the same dyno/operator. Get your baseline and go from there. Dyno Dynamics are a LOT more accurate in a trained operators hand. Dynojest are for numbers to make people happy. 
Also, the reason why it bogged down is because it isnt "bogging" at all. A DD is a brake dyno. Once you get the car on and into the desired gear in 2000rpms, the switch is flicked and the "brake" load is applied. Thats what measures the torque. Its different from the drum style in a Dynojet. 
As for why you are shutting down at 4500, thats beyond me. 


_Modified by tdogg74 at 12:41 PM 1-28-2008_


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## Ugly_Dub (Mar 19, 2003)

*Re: (tdogg74)*

switching dynos was not my idea.. moved to a different state... but thanks for the info.. This guy was very new with this dyno. So I think if it was being operated by a more trained person it would have gone much smoother..


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## Dyno Mike (May 28, 2007)

Jetracer, as a DD dyno owner myself I'll pass along a few ideas, some of which you may be aware of, but for the sake of others here goes. 
Find a dyno and operator your comfortable with and stick to them. Dyno's will of course vary brand to brand and also dyno to dyno of the same brand. Dyno jets I've tested with cars that have been on my DD dyno, typically read 15-17% higher and other DD operators report similar findings. Mustangs generally read closer but as there seem to be various options for Mustangs, not consistently. I've seen variations between DD dyno's of as much as 5%, which depending on the engine mod you've made can make all the difference in detemining the mods effectiveness. 
On a DD it is important that inertia and ramp rate are consistent between testing sessions. It is also very important that test cell conditions are monitored closely. The DD will require periodic updated temp/humidity/baro, but in a small cell these conditions can change very quickly and affect the atmospheric corrections.
Once the load is switched on and the pedal floored, the run should commence immediately to avoid building heat and abnormal boost.
Regarding your bogging, there are many possibilities, but here is one to keep in mind. I've had cars that seemed to run great on a dyno jet, but have a flat spot/drivability problems on a DD. The dyno jets heavy drum can hide a bad part of the map because the drum inertia will power the car right throught the flat spot. There's a good reason you don't slam the brakes on when your on a Dyno Jet
What does your A/F and graphs look like?


_Modified by Dyno Mike at 3:17 PM 2-3-2008_


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## Ugly_Dub (Mar 19, 2003)

*Re: (Dyno Mike)*

hey thanks for the info.. yea some I know but some is new info..


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## DD Todd (Feb 9, 2008)

*Re: anyone ever had problems on "dyno dynamics" dyno? (jetracer)*

*"The first 2 were on a dyno jet. Last time the car dynoed at 367hp. This time though I could not get any consistent runs and the highest was 292hp run."*
You can't compare numbers from different dynos like that, especially the lowest reading dyno (Dyno Dynamics) to the highest reading one (Dyno Jet). Well, you can compare numbers between Dyno Dynamics dynos when used in 'Shootout' mode. This mode runs a fixed set of varibles like atmosphere, ramp rate (I'll explain that further down), etc etc. This mode makes it impossible to skew the test results. Ordinarily, Dyno Dynamics reads on average 15% lower than Dyno Jet. Dyno Jet numers are inflated and unrealistic, which is well known in the chassis dyno industry. 
Using a generic 15% reduction from your orginal Dyno Jet numbers, you would be around 311whp versus the 292whp that you actually saw. That still leaves 19whp that you’re missing. Maybe something changed in the tune? Boost? Gas (octane lower or winter gas additives)? Crappy fuel would definitely make the ECU pull timing, which would result in less power. 
On Dyno Dynamics, there are various ways to strap the vehicle down. Instead of pulling the car from the front and the rear as with other chassis dynos, instead the wheels are pulled into the rollers. This is really the best way as the tires are being forced to dig into the rollers. With enough power, the tires will actually climb up the rollers. Other dynos rely only on the weight of the vehicle and being in a higher gear to hold traction.
With that said, if the wheels are strapped down with too much force into the rollers it will make the numbers lower. Additionally, they should have instructed you to bring your car in with 50psi of air in the tires. When tires deform from having less than optimal pressure, the numbers will again be lower and lack consistency between runs. 
*"The worst being a -2.4hp."*
The only time I ever see this is when the "Backwards" mode is selected. Dyno Dynamics is a bi-directional setup. If the incorrect direction was set, then the numbers would indeed be negative. 
*"The operator is telling me that there was nothing wrong with the dyno and that it is my car that has something wrong with it. Now to me it seems a lot like operator error."*
Did you have the WB attached to read AFR? How about the vac/boost attachment? You could have had a graph printed to show AFR against boost over RPM. This is great diagnostic info and in my opinion should always be used. 
*"While I was making my runs in 3 and or 4 gear. He would hold me at 2000 and the once I was stable I would run it to redline. But the car would bog down really bad at first then would finally go screaming up to about 4500 and just stop... Now last time I was on the dyno I did not have any problems with it doing this. It would not bog down nor did it just stop at 4500 rpm. It went all the way to redline (around 7000rpm)”.*
Dyno Dynamics is not an ‘inertia’ style dyno. Well, there is some inertia of course, but it is very low. An inertia dyno requires the vehicle to be in a 1:1 gear, usually 4th gear or 5th on a 6 speed manual. On a Dyno Dynamics, you could actually dyno in any gear BUT the ‘ramp rate’ must be changed to account for the different rates of acceleration. 
Ramp Rate, in a nut shell, is “how quickly do we predict the vehicle will accelerate the rollers?”. The lower the ramp rate, the lower power we expect the power output to be. This affects resolution in the graphing and if set too high, boost pressure may be lower than expected. You want to be as close with ramp rate as what you would see on the road (there are guidelines for the appropriate ramp rate). I generally instruct folks to use 3rd gear for testing WOT runs in a 5spd and 4th gear to be used in a 6spd. 
Concerning holding the car at 2000 RPMs that is supposed to happen. There is a ‘hold’ mode, which should be used at the start of the run. This helps load the car up in preparation for the run. It can hold for as long or as little as you like. Now why you weren’t able to get above 4500rpms on one of your runs may have been operator error. Maybe the run was stopped prematurely?? Not sure. Did you guys turn off traction control (if you car has it) etc? 
At the end of the day, the dyno is only a tool. Most shops that own a Dyno Dynamics were sold on its ability to quickly map out engine management, hold traction on high powered vehicles, and produce consistent readings. But you have to know how to use it








This is probably more info than you wanted but hopefully this helps you better understand your numbers











_Modified by DD Todd at 6:48 AM 2-9-2008_


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## Ugly_Dub (Mar 19, 2003)

*Re: anyone ever had problems on "dyno dynamics" dyno? (DD Todd)*

the more info I get the more that Im quite sure that its mostly operator error. given the fact that he tells me on the second run that he did not hook up any a/f, or boost sensors. Then to have not one of the runs be close to any other. And after the fact I have found out that he has only run about 10 cars..


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## GTIracing88 (Dec 27, 2007)

*Re: anyone ever had problems on "dyno dynamics" dyno? (jetracer)*

When I put my car on a dyno dynamics dyno it said that I only had 138hp . Seeing that number pop up was heartbreaking and very dissapointing considering that my car is supposed to come with 150hp stock and Ive already put a nice amount of money into it. I wouldnt worry about it to much if i was you, the guy operating it prob had no idea what he was doing. My dyno graph says i have 138hp but i still beat my buddys jetta which dynoed at 211hp


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