I just googled the difference bet. a Dynapack and Mustang dynometer due to the heated debates between tuners and their loyal followers lately.
...Not surprised at all, I read an article by Meritt Johnson when they tested the new Nissan GTR & Porche GTR and read these numbers:

Nissan GTR:

Mustang Dyno: 406 HP/6400 rpm & 414 ft-lb/3800 rpm
Dynapack: 452 HP/6350 rpm & 448 ft-lb/3865 rpm

Tested on same day and conditions.

I have also read other articles and car forums that the general consensus is that Mustang reads 10-12% lower than Dynapack but Dynapack seem to jibe with manufacturer's power claim.

'Just for the sake of information..

 

Well, the manufacturers are reporting crankshaft horsepower and torque, while the chassis dynos are measuring wheel horsepower and torque, so if the Dynapack dynos are regularly agreeing with the manufacturers, then I'd call that an inaccuracy on the part of the Dynapacks.

 

The Porche was not tested in the Dynapack bec. the Nissan GTR broke the machine after 2 runs

 

I would suspect a lack of maintenance on the part of the DynaPak owner. There is a Porsche shop down the street from me with one, and they routinely test cars with 500-700HP. Race shops choose this unit because of its reliability and consistency. "Tuning" shops often choose rolling road dynos because they are less expensive and faster to set up.

 

The Dynapak will always be more consistent. Yeah the numbers will differ from those of a rolling road type, but that's always the issue when comparing numbers from different runs or dynos.

There are simply more variables to consider and attempt to duplicate the conditions of with the rolling roads. Tire pressure, orientation on the roller, strapping pressure all come into play when comparing the same car. Even tire compound will effect the rolling resistance.

I'm sure there can variance in the way a car is mounted to the DynaPaks also, but the fewer varables there are, the better.

 

WOW
Seems like Grassroots has got it right.
Isn't consistency what it's all about. Chuckt has it right too.
I've been on 3 types of Dyno's and the more consistant has alway's been the Dynapac.
That's my 2 cents worth.

 

I came across this article some time ago that has a pretty good description of the differences between hub and wheel dyno measurements. As you would expect, the overriding difference appears to be due to the impact of the wheel's Moment of Inertia on the torque calculations:

http://home.earthlink.net/~spchurch/churchautomotivetesting/id12.html

The difference between the two approaches increases with higher horsepower cars. For the hp/torque levels produced by Minis it seems like (very) roughly a 3-5% difference.

Note: this article talks about Dynapack vs. Dynojet. But since both Dynojet and Mustang are wheel dynos, the physics is equally applicable to both.

 

Dynojet even reads higher than Dynapack but they are closer in results. My point is don't bash the results in Mustang as some people here because they read lower than Dynapack...at the end of the day, what matters is winning the race and putting good numbers on track and drag (given equal driver skill).

 

Hmmm...really? Our cars dynoed on a Dynojet and it was very conservative. Even guy's coming in with huge V8's were humbled by it.

 

as was stated consistency is key and that is where the dynapack comes in handy...your not at the mercy of the tires and friction...you can get a clean run and get the most out of it

 

Mustang is also consistently reading lower than Dynapack. Almost all car forums I've visited from BMW, SRT-4, Camaro, G35, RSx, Civics agree that Mustang is the heart-breaker dynometer as we all know that high numbers make us feel good

 

I think people get caught up in the whole dyno number thing a number is just that, a number.
Dynos are good at measuring the deltas or gains before and after performance improvements.
But numbers are only good for pissing matches and bench racing. It should come down to how the car drives.

Now on to the comparison:

The industry leader in number output by far is Dynapak followed closely by the Dynojet.

Next is Mustang, generally about 7% less than Dynojet numbers.

Superflow is about 3% less than Mustang.

Dyno Dynamics are about 3% less than Superflow.

So the Dyno Dynamics reads lower than the Mustang. It reads WAY lower than a Dynojet. It reads WAY lower than a Dynapack.

Just because the dyno spits out a number, it doesn't means squat without knowing ALL of the correction factors.
All of the dynos software incorporates parameters that are operator definable. The operator can "adjust" the output of the dyno to display any number desired. By adjusting weather station parameters, external corrections factors, inertia compensation, or any one of a dozen different factors the output number can be modified. Some dyno operators adjust the output of their dynos to read high .

 

Good Data D-Man

 

Thanks D-Man. That makes this even more amazing then I thought .

First run: Thursday
Stock tune
Stock Injectors
Stock cam
15%
OBX
Miltek

Second run: Friday
Stock tune
Stock Injectors
Stock cam
15%
OBX
Miltek
RMW Big Valve Head


CCE00000_21.jpg?t=1239153555

 

wow big numbers there longboard, it'd be nice if you had comparison numbers on another dyno

 

Man, that was the start of project 300hp.
Long time ago. Just proves Jan's parts and tune produce big numbers.

 

So a Dynapack indeed gives higher HP/Tq reading than Mustang Dynometer. Thanks everyone.

 

Short answer:

DynaPack reads a bit high [a few percent high assuming reasonable settings]
DynoJet reads fairly accurate
Mustang reads quite low [anywhere from 5-15% low in my experience]
Land & Sea Dynomite are all over the place depending on settings

 

high, accurate and low to what

I know off only one person and there in the uk who dyno there engine on an engine dyno and then went to 4 rolling road to see how accurate they were.

Cant find the thread unfortunatley, but who says there engine dyno was reading right in the first place

Just enjoy your deltas

 

With known BSFC, MAF, MAP, and AFR you can calculate HP very accurately. The first one is toughest to find, but being in Detroit helps ease the acquisition of such information. Like I said in my previous post, I gave the short answer.

You bring up a good point though. With so many dyno operators about as intelligent as the Big Gulp they're hanging onto, it's better to trust same-session deltas than try to get accurate data.

 

Very impressive numbers

What were the deltas?

Why aren't the HP/Tqe curves are not crossing at 5250rpm

 

Hp and Tq aren't plotted on the same axis in this graph.......

It's 5252 in the equation.