No doubt...We're actually doing this because of questions we have ourselves, pertaining to the same situation, just less extreme. And we thought the info might be pertinent in this case.
Not to mention I was one of the first to "question" the results of, um, possible vehicle, and, um, possible dyno....
Seen to many diff cars, engines, combos
After the said car in question was run on a DJ, those #s were actually believable. Low, but believable.

 

What did you find out on your tests?

 

One car was dead on. Another was about 20 HP higher on the DD than the DJ. The third was same HP, or real, real close, but with a 50 Ft LBS dif. The DD read lower torque on that one. Dont quite understand how there could such a big dif in torque, yet the HP was real close.
I think the one thing that we have come to realize with our little unscientific test, is that the DDs may not be as repeatable, or accurate as people would think. I may get blasted for saying so, but you sure cant beat the repeatability of a DJ. I've talked with the dynojet tech guys, and they tell me you cannot manipulate the correction factors of their dynos. That being said, there may be ways to "fool" them i.e. messin with the weather center, and so forth.
It would be nice if there was some sort of "standard", that way some of the optimistic numbers posted wouldnt be questioned. 'Tis an imperfect world we live in. Best we can hope for is truthfulness......

 

You might want to research "Xtra Correction" and "Inlet Air Temp Probe".

 

For a DJ? Or a DD?

 

Yes that has already been found in my research. Its on the DD units to fudge the numbers some more Thats what I think is happening in one case already and on 2-3 other cars as well.

My problem and question here is...Was the A/F the same on all your testing of these cars on the DJ and DD units Edcmat-l1?

 

You cannot beat the repeatablity of a dynojet. I dynoed the same car in 2 different cities within a week apart and the difference was less than 3hp on a 490rwhp car.

 

Short answer is no. There was quite a difference in the A/F. I tried uploading the DD graph. Aint quite workin out.
I only have one sample (car) of A/F from dyno to dyno. I can try to get the info on the others. Have to contact the car owners.
Anyways, I had the A/F @12.9:1-13:1 thru the entire pull. We got it to our dyno, and it was like 12.3, 12.4 straight across. The DD graph A/F sample was taken UPSTREAM of the cats. I was sampling at the tailpipe. So, that would increase the dif. Up stream should show richer, if the cats are lit, and in good shape. if they're not working, at the most it should be the same. So the dif is probably more like a full point.
After we get done with the cam swap, I'll check upstream and downstream to get an idea of whats up.

 

In the world of metrology, there are so many variables involved that you just got lucky that day.

Ya'll are looking at the wrong device as the UIC(unit in comparission). The standard isn't a motor. It can't be. LOL even Jet Engine Test Cells don't use a jet engine as the calibration method. Albeit they do have sets of motors that they will run to use as a comparision to a UUT.(Unit under Test)

First and formost a dyno isn't worth crap unless it is setup and calibrated correctly. That goes for any measurement equipment. The biggest correction factor is always in the user. Torque wrenches and pressure guages are the same way. Then the quality of the dyno itself, i.e. its parts then comes the algorithm that the manufacturer chooses to use.

I see it as a big fault of the dyno companies that they don't invest the time or the money in demonstrating their accuracies. I might use this for my Master's Thesis.

In an industry where .001 of a second count and .00001 of an inch can mean a part coming apart it would be benificial for dyno's to be more accurate not just for bragging rights but for more accurate tuning.

 

Listen, that is just one example. Should you still doubt me go ask any nascar team and see.


BTW. Theres no "calibration" to a inertia dyno.

 

I know what you are saying but I really dont see a big problem with any of the dynos that are in use as far as how they are built. What exactly is it that the dyno manufactures should be doing differently? When I can input the same load and the dyno repeatedly gives me the same output there isnt too much more the dyno manufacture can do.

Most of the confusion with the varying power numbers I feel comes from the lack of testing standards and operator error. Not being consistant with the test cell conditions and air quality, temperature differences from run to run, and MOSTLY when someone trys to compare a test result from one type of dynomometer to totally different type that is using a totally different testing method. Other than the word DYNO, there is not much else in common when you are comparing an inertia test to a loaded test.

We could talk about this alot more but I think you understand what I am trying to say.

 

I know what you're trying to say. I understand that the 2 types of dynos being discussed are completely different. I'm sure everyone else does too. The point trying to be made (I think) is the ability to skew a certain dynos numbers. The reason WE tested more than one car, on 2 different types of dynos was because we had the chance too. What started it all was one of my customers dynoing almost exactly the same on both dynos. We just by chance had dynoed that and 2 others on both dynos under very similar weather conditions. Had this thread and the other not been going, we would have most likely kept the findings to ourselves, as in our case the differences werent near as dramatic. There was some dif, but not terrible, just the fact that the results were inconsistent.

 

Bottom line is a dyno is for tuning. Baseline and gains thats all! The fact that DJ has been on the American market longer the DD has made it the benchmark of dynos. I spent almost 6 months looking at dynos before buying the DD. We wanted a stable and accurate dyno for tuning in load.

We have dynoed hundreds of stock late model cars in which we have determined that the DD dyno reads 10-12 % lower then a DJ. We locked our dyno a year and a half ago at 10% and never looked back. I just dynoed another stock 06' ZO6 which made 458 RWHP and 432 RWFT. That is on the money.

With all the new tuning software out there today and being able to tune in "real time" I am real glad I bought this load dyno. Hopefully this year we are going to be able to tie the tuning software into the dyno and be able to log things like TPS, MAF and any other OBD2 sensors. This is the next generation of data gathering.

 

That right there will be the biggest variance. A DD has a simple key to push, X, and you can add a % to the numbers. Some people call it a correction factor, I call it a multiplier. It needs to be asked if the operator is putting a multiplier on the readings, depending on the shop some do and some don't.

 

haha...yea...go figure...wether it be a engine dyno or a eddy current setup...its still a given weight spun on a known circle given over a specific time with x amount of force being applied and then throw in the mathmatics...

 

I would never ever own a DynoJet agian.


The DD dyno is so much better for tuning and actual real world stuff.



DynoJets are popular becuase they are cheap and plentiful.

 

Word has it he crashed the car a few days ago.

 

Go ahead and explain the difference in doing it and not doing and the numbers that will correspond with it. I think the person knows hes in a world of ****.

 

Dyno Dynamics are good tuning tools, no doubt. But to see the variation in results from ONE dyno dynamics to ONE dynojet, using the SAME cars in very SIMILAR conditions, for shear numbers sake it makes me think twice about the value of a DD for anything BUT load tuning.
AND, although I dont know the $ amount of a DD I cant see them being much more expensive than a DJ. My DJ is known for being stingey. Compared to the local DD, I've had customers tell me mine read as low as 60 HP LESS than the DD. And that was on a sub 500 rwhp car. Those #s are basically a 12% or better, fudge factor. And DJs are supposed to read high..........

 

doespeedturnyouon?
Whoever you're talking about, that sucks.....