I guess that's the message that the Buschur camp has been pushing for years.

However, if you continue using a dynojet for what it is--a tool -- I still see it being a viable instrument for tuners around the world. A while back in another dyno discussion, I mentioned a metaphor that equates to this whole dynojet vs dynodynamics issue.

To me it's the same as the worldwide conflict of measuring inches vs cm. A ruler is a tool of measurement. If you decide to use the cm side or the inch side, you are still taking measurement of the same item. Ultimately that item is the same size, but the user of the tool decides what scale to use for measurement. The difference in "size" after mods/tuning is what should be emphasized.

 

What is very interesting to me is the notion that the Dynojet #'s begin to get closer to flywheel power as power increases. This seams like a terrible characteristic. Because for example, look at AMS cam tests and CNC cylinder head tests and stuff. They are using a 35R car for those I think, and making things like 80 ATW gains or whatever.

So at the 600 atw level on a Dynojet, 80 atw is not the same as 80 atw at the 300 atw level. So this becomes very misleading when we as consumers are evaluating AMS parts with these tests.

An interesting dyno comparison I think would be to test a car at 14 psi and 30 psi on both Dynojet and DD and see how the #'s turn out.

As a final note, one thing that has upset me so much over the years is how many DD shops use a 1.1 or 1.2 or even 1.3 correction factor. It really destroys the DD dynos reputation. Whoever is the dealer for DD in the USA I think has been a big let down. Also, all DD runs should be in shootout mode so all the variables of the run are printed on the graph.

 

A.. You are dead right.. the higher the hp- the higher figure of the spread (even keeping the percentages the same)

B..Only issue to most is when the correction factor isn't 'disclosed'. As long as it is, anyone can put the numbers into perspective. When it's not disclosed, it leaves a variable up in the air. I'd still like to understand the MD calibrations a bit better and how it relates to other dyno 'tools'.

C..As I understand it, shoot-out mode reads higher than 1.0 correction-- I'll let the experts chime in on that one..

 

Great thread and info. Whenever I dyno from now on I will be sure and ask the correction ratio.

 

Its more like comparing inches by "just eyeballing it" vs. measuring centimeters with a laser micrometer.

Here's some reasons I think Dynojets suck.

1) Dynojet numbers run away at higher power levels (can't correlate real power:weight like that).

2) Dynojets have a ton of roller noise and require smoothing. There are dips, jags, and bumps in the curve. This sucks, because you can't tell a minor ECU corrective event fron roller noise.

3) You can't partial throttle tune load cells like on an eddy current dyno. You can't adjust ramp rate in the same way or simulate high load vs. low load situations.

4) The graph just spits out at the end, and you can't view the run in real time.

 

There was some confusion about this, but what happened was, people were running in shootout mode and looking at the "s_hp" number, which is a DD flywheel estimate. The "hp" number is the atw number.

 

I think DD operators that "correct" are kind of selling out. Educating your customers will pay off a lot more than stroking their ego.

A few years ago, there was a Subaru guy who made 390whp on a Dynapack, and he challenged me to race at our local forum's annual dragstrip outing. I was making 348whp on a Dyno Dynamics. He was talking mad smack about my numbers all day until I went 11.8@118 to his 12.2@114. Shut him up real quick.

 

It all depends on the software version when determining a "set" correction factor. However, because of all the debate on correction factors, I leave my dyno set to 1.0 all the time.

 

Funny you mentioned that. We were able to use the lower reading dd to "bait" a certain high hp civic into a contest of speed. It's funny how you can twist lower numbers to your advantage in some cases.

 

 

I too like DD dynos for tuning do to above posts...dynojet for "dyno queen" #'s. On a very rough/poor tune I made 463whp/410tq on a DD dyno.

 

That's a strong running car....

 

This is a big issue. I remember my first trip to the USA (quite a few years ago now) tuning Haltechs and we were tuning this Mustang. Anyhow I said to the dyno operator ok we now need to hold it at 4000 RPM so I can find this lean spot and he said "oh we can't do that".

 

There is a DynoJet and DynoDynamics locally that I dyno on and the DJ tends to read ~15% higher than the DD.

 

Oh ok that explains a lot. Better than nothing I guess.