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Discussion Starter · #1 · (Edited)
i found this to be an interesting comparison from the TOV guys :

2.4l accord ex mt5 on dynojet :





and a brief explanation by shawn church on the two dynos :

Interpreting dyno charts - Dynapack runs are somewhat different than Dynojet measurements. In particular, the Dynapack loads up the engine for a second or two before making a measurement run. This leads to somewhat high torque numbers at the start of the run because the engine is making maximum output without accelerating, which means there are no accelerational losses to speak of. Its a minor factor for NA cars, but for automatics the torque converter will often slip and cause excessively high readings that don't correspond to actual engine output, but they do reflect real world torque at the ground.

Readings between different sorts of dynos can not be directly compared, but in general the Dynapack will read at least 10 hp and 5 lbs-ft of torque _higher_ than a Dynojet.
the k24 is putting down good numbers.... 140 on the dynojet from allegedly 160 crank hp. given the 5th gen at 160-165 on dynojet from allegedly 200 crank hp, one of 'em ain't rated properly. ;)
 

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Interesting. Where is Joel? Wasnt his 203whp run on a dynapack?
 

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Is that even the same car? The dates are almost 5 months apart. Now it is less valid of a comparison, lol.
 

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Discussion Starter · #5 ·
nope, not the same car, just the same model with approximately the same mileage. notice, though, that the torque and hp curves are almost exactly the same shape, just scaled slightly differently.

and the explanation of the two dynos is valid either way... and keep in mind this is coming from someone who owns a dynapack. bottom line, when you compare dyno runs, a 215 whp run on a dynapack is more like a 200whp run on a dynojet, ±5whp on each side.
 

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schwett said:

and the explanation of the two dynos is valid either way... and keep in mind this is coming from someone who owns a dynapack. bottom line, when you compare dyno runs, a 215 whp run on a dynapack is more like a 200whp run on a dynojet, ±5whp on each side.
I agree, but I think I can explain it. the Dynapack, from my understanding, requires you to take the wheels off the car and measure hp at the hubs. This isn't quite the same as the dynojet, since the dynojet measures power with your entire car on rollers with the wheels on. Hence, the Dynojet will account for hp losses due to power loss at the wheels, whereas the dynapack cannot. And since wheels are heavy (stocks with tires are around 40lb, I believe), but more importantly, they require power to turn and due to rotational mass, it's actually requires a lot of power to turn. That 10-15 whp difference is probably because the Dynojet is forced to take this into account, and gives a more accurate reading at the wheels, whereas the Dynapact just takes its reading at the hubs.
 

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Discussion Starter · #8 ·
yep, the wheels themselves and the frictional losses of the wheel vs roller interface are the main reasons why the dynapack reads higher. there are other differences related to the accelerational losses of the roller itself but i think the wheels are the largest factor.
 

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I'm going to Church on Sunday (hehe)........ for a vafc tuning on a dynapack with a wideband 02 sensor. Would I be better off looking for a shop that uses a dynojet? The dynapack sounds really good to me..but I'm not that knowledgable about dynos.
 

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The dynapack is a more versatile tuning tool than the dynojet - go for it. Just be aware that the ultimate #'s will be different than if you used a dynojet.
 

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Daemione said:
The dynapack is a more versatile tuning tool than the dynojet - go for it. Just be aware that the ultimate #'s will be different than if you used a dynojet.
Why does it make it a more versatile tuning tool than a dynojet?
 

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axio said:
Why does it make it a more versatile tuning tool than a dynojet?
It can be set to do runs that last as long as you want them to, which changes the load on the engine. It's got a couple different modes of operation - I believe you can do part-throttle tuning as well. You can make it stop the engine at specific rpm, etc., etc. I'm no expert on it, but there's a bunch of info over at their website - www.dynapackusa.com.

It's major advantage is it's sensitivity, though. Since there's virtually no inertia other than the engine itself (wheels & tires are removed, & no big steel drum that it spins), it can pick up tiny little variations in power output that just get covered up on a dynojet. They claim to be able to measure the difference in output from turning your headlights on . . . . .
 
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