just re-dynoed WTF!!!????

[LeoGSVT]

i took my car to Ford Parts network, a well known tuner in st. augustine last week...my mods are a 2.80, idler, borla stingers, FIPK, SCT tune...the car made 454/469...today there was a dyno day up here in jacksonville at a shop that just opened up, they have a DynaPack chassis dyno, it bolts up to the actuall axel...wheels off!!! make a long story short i threw my car up on it to see if it would make to same power...they made 4 pulls and my higest numbers were 407/490...im like wtf?? where did all my hp go?? and they are saying go back and check the other dyno, its not right...and this dyno is more efficent, true TO THE WHEELS!!! i know what my car puts down...has anyone ever used one of these dynos before?? im lost here.... :shrug:

 

[SVTspeed]

wow that is weird... i've never heard of it.. with the mods you have.. many others have as well.. and make 455-480 rwhp with those mods

 

[Juiced46]

dynapacks are the most accurate dyno to use. But the #s from what ive seen have been very close to dynojet #s

SVTspeed, where did you get that avatar from, looks familiar

 

[SVTspeed]

ehhe i dunno someone had it and i msged them said it was cool so i used it from there on

 

[03gobluecobra]

That drastic of a power change, you would definitely be able to feel it on the street. I'm guessing their goofy dyno is what's messed up.

 

[harleytruck9144]

i am a friend of Leo and i was there when this all happened. my theory is that the reason the numbers are different is because of the way the two dynos work. for those that dont know, both dynos measure the numbers in a different way. the dynojet measures horsepower and converts it to torque using the equation hp*5252/rpm, while the dynapack does exactlly the oppostie and measures torque by putting backpressure on the motor. the excess backpressure the dynapack puts on would explain the extra torque and less horsepower as the wheels are accelerating much slower with the excess backpressure. the dynojet is simply a 3000lb drum that you are spinning and it measures how fast you accelerate the drum. i duno, maybe im wrong but it seems to make sense to me and it is atleast an excuse for now.

 

[03yllwguy]

I had the SAME EXACT scenario happened. Had Shawn at Socal tune my car and made 457/456. Next day went to this other dyno shop for a club day and dyno'd 437/437. I called Shawn and was like WTF. He put it back on his dyno free of charge and I made the same 457/456. He then tweaked it a little more since I was already there free of charge as well. But case in point, don't go off these dyno results. If you had your car tuned at a reputable shop, stick with those numbers. Remember Dyno's are tools for tuning, and that only.

 

[03yellow]

Can you post your graph?

 

[fiveoguy]

I had my car dyno'ed on a dynapack when it was bone stock. Put down 371/358, which is right in line with what I expected. I don't think the problem here is the type of dyno, but probably a calibration difference in the two. You should try to stick to the same dyno if you can, there is always going to be differences between different dynos.

With that said, the dynapack numbers sound a little off for your mods. The dynapacks seem to be a little more complicated to setup and use correctly than say a dynojet. The place where I had my car done had only recently learned how to use theirs correctly after having it for over 6 months.

One of the most common problems I've seen with the dynapack is the rear gear ratio being off. If you don't run your car in 4th gear (1:1) and enter the correct rear gear ratio into the computer on the dyno, your numbers will be off. Seeing as how you had high torque and low hp, i'm betting that the dynapack operator had the wrong gear ratio.

 

[DR. WU 2000]

I don't know about you guys but I am confused, and I not be the brightest bulb either. :shrug: Something seems wrong to me. I would go with the first dyno #'s. :beer:

 

[LeoGSVT]

my car def. does not feel like 407 to the wheels, i would never use another tuner other than the first guy i went to..i just wanted to see how acurate the other dyno was...the gear ratio thing sounds right though, because he was asking me about it before hand, and he said he had to look it up on the net...

 

[Rwick7]

I wouldn't sweat it if the car feels fine. Go back to a dynojet if you must put your mind at ease

 

[CobraBob]

Here's some interesting information I found doing a Google search comparing the Dynojet to the Dynapack. It says that the Dynapack characteristically reads about 6-7% higher than a Dynojet 248C. So if that is true then the numbers posted above are way low. Can someone who really knows these two dyno types comment?

 

[Black2003Cobra]

The two dyno's do the measurements differently, yes, and I can think of one reason why the Dynapack would read higher than a DJ, but not by 6-7%. Since you take the wheels off and mount the dyno right onto the hub with the Dynapack, you don’t lose the inertial power that would otherwise be used to accelerate the rear wheels and tires. The amount you lose would go in direct proportion to how fast they’re accelerating. Anyway, I’d guess it would only be in the 5 to 10 hp range (if I take a stab at the angular acceleration and mass moment of inertia of the wheel + tire). So it is odd that the numbers were lower. Was there a difference in ambient conditions (viz., the temp) between the two pulls? If it was hotter out when you ran it on the Dynapack maybe your computer pulled some timing. Oh, and did both dyno’s use the same correction factor and/or were these numbers uncorrected? Just some guesses.

 

[Logan2003Cobra]

Did they do the correction for altitude, temperature, humidity etc... If I were to go by actual numbers, my car only put 308 to the ground when stock... at over 5000 ft. elevation with the outside temp in the upper 80's. Catch my drift. That's why most people go with SAE numbers; to balance things out.

Logan