Dyno Reading Comparisons

[Race Grandpa]

Paul Magee's dyno results brought up the question of different results from the Mustang & Dynojet. Paul's results were from a Mustang.

I believe that one person said that Mustang gave better results than the Dyno & another person said just the opposite.

Any other opinions on this subject?

[mageep]

I think the conventional wisdonm is that Mustangs read shy compared to the DynoJet...

HOWEVER, not sure if it makes any difference, but I was on a development / testing unit IN the Mustang Dynamometer HQ in Twinsburg, Ohio...

I have been there 3 times, and it seems to read generously compared to other Mustang units. The dozen or so other folks I know that have been there on the same dyno say it reads a little high by Mustang standards as well.

Now, the way Mustang uses SW to determine what should be 'consistent' results says they should be more consistent... But they are using a lot of technology to create that consistency (relatively speaking), whereas DynoJet just keeps on using that same big, heavy drum, which IS consistent, so...

It's like comparing an old carbureted GM to a brand new Mercedes S-class with 6 miles of wiring in it. They're both with faults. Just one is bone simple; the other requires a comp-sci degree to get it right.

Long story short: Don't use 2 different dynos to do any tuning or you're screwed. Use the SAME DYNO all the time. It's the only way to know you're apples to apples.

[Race Grandpa]

I did a search on the Miata.net forum for an answer to my question as to the differences one should see between Mustang & DynoJet. (Lots of posts with word Mustang - yes the car.)

This is what I found there:

Gordon, The Preeminent Moderator, stated that the "Mustang dynos typically read about 13% less than a DynoJet..." Or if you are stating how much more does a Dyno Jet reads over a Mustang it would be 14.3%.

Then I found two post where people were comparing Mustang to a DynoJet results. The differences ranged from 21.2% to 33.0% in WHP!!! However, the "comparisons" were done one to two weeks apart from one another. So, those were not comparisons.



My inquiry was in anticipation of putting my car on a Mustang Dyno for tuning right after the coldside install. I was not happy with the results and the best results occurred on the 10th run. So a lot of heat soak, which they said accounted for a power drop of 10-15 hp. I am not sure how they can come up with this number.

NO, you can not see the charts Will put it back on the dyno soon and post the charts.

However, I am real happy as the car is REAL FAST.

I think the best thing that I learned from this exercise is the value of putting the car on the dyno is for tuning to get maximum hp and make the engine safe. There seems to be a lot of variables that are hard to issolate and make adjustments for in on getting absolute numbers. Still, I would like to wear that badge that has high hp written across it - my ego always needs to be stroked!!

[chuckerants]

Granpa,

You can tune a car on most any dyno. However, the reason why most people use Dynojets is because Dynojets are the most prevalent dynos around. Also, the results on one Dynojet will be repeatible on any other Dynojet.

There are those that don't consider a Dynojet a "real" dyno, but again, in order for people to be able to compare apples to apples is one main reason we use a Dynojet.

[Kyp J]

Another good thing about running on a dyno is the ability to observe and listen to the engine with just engine noise and standing right next to the open hood.

Mine was correctly diagnosed with a problem by people who knew what it should sound like and could also hear (both are attributes that I don't have). They said "That don't sound right". (Actually the poor grammar was put in for effect, they are well educated and well spoken gentlemen.)

I am now working to correct the problem which eventually got bad enough that I could hear it.

[chuckerants]

Another good thing about running on a dyno is the ability to observe and listen to the engine with just engine noise and standing right next to the open hood.

Mine was correctly diagnosed with a problem by people who knew what it should sound like and could also hear (both are attributes that I don't have). They said "That don't sound right". (Actually the poor grammar was put in for effect, they are well educated and well spoken gentlemen.)

I am now working to correct the problem which eventually got bad enough that I could hear it.

I think you got the quote right.

I wasn't even near your car but I heard that "sound" and I thought WTF is that???

[Race Grandpa]

Thanks for the info.

Two questions for you:

1) The Mustang dyno had a Weather Correction Factor in the program. Do DynoJet's have this.

2) How much can one depend the WCF?

Just getting into Corky Bells book. Learning how the condition of the drive train and tire size can make a difference in the dyno results.

Thanks Again

:dots:

[Tom @ Fast Forward]

DynoJet also corrects for ambient temperature, pressure, humidity, etc.

You want to run the dyno with the gear that is closest to 1:1 for the best results. For a Miata, that is 4th for a 5 speed and 5th for a six speed. Tire diameter does have an effect as it effects the final drive ratio. Dragster tires do an especially great job of that. ;)