what is the hp difference from a mustang dyno and a dyno jet thanks

 

i think just the mechanical means by which the power is measured.

makes comparison between dynos impossible, truthfully even comparing one dyno jet to another dynojet is not neccessarily gonna be accurate.

dynos are a tuning tool that's it.
racing is for bragging rights

 

There was an article in Hot Rod magazine about 2 years ago, where they tested the same car (unfortunately a HP-challanged Mustang GT) on 5 different dynos, under as close to identical conditions as possible.

The results showed the Mustang dyno showed 3.5% less peak HP and 11.1% less peak torque than the Dynojet dyno.

Mustang dyno:
219.1 HP / 239.3 lb-ft

Dynojet dyno:
226.9 HP / 269.3 lb-ft.

I'll move this to "General F-Body Tech...." since it really isn't specific to the LT1/LT4 engine.

 

From what I understand the Mustang dyno is more accurate but shows less HP than what seems to be the industry standard Dyno Jet.

My 590 RWHP was done on a hot day on a mustang dyno. I'll be looking to dyno it again on a cooler day on a dyno jet sometime to break the 600 RWHP mark.

 

I've read of some people showing significant differences to the tune of 30+ rwhp, but you can't just automatically assume a Mustang Dyno is "way low". Especially nowadays when alot of Mustang Dynos are calibrated to put out numbers more in line w/ Dynojets (do doubt due to bad press about reading low even if it's actually more accurate...). One MustangDyno to the next could be significantly different due to some of these variables. There really needs to be a set industry wide standard for that results in all properly calibrated dynos putting out comparable numbers...

 

There are 3 main types of chassis dynos.
Dynojet is famous for their lower cost inertia dyno. It was derived from a motorcycle dyno after the inventor wanted a way to test parts operation on the bikes he serviced. After they figured out how to get the numerical calculations close to what made sense on a drag strip, he though..."I could do this for cars too." So the calculations that Dynojet used to calc your 4 wheeled vehicle all derive from the same calc he used for his V-Max. Interesting I thought.
Mustang and Superflow use Eddy-current brake dynamics on their dynos. A calculated amount of resistance is applied to the tires of the vehicle being tested. Its ability to overcome this resistance and at what rate it does so determines you numbers here. This design was a melded military concept into civilian reality. These tend to be less bragatory in results.
There were also attempts at making a water brake chassis dyno, much like engine dynos of today. I have never seen one though.
Hope this helps.
Oh yeah, I almost forgot. There is alot of talk about weather conditions and filters. At a quality shop, these are used to gain some sort of standard comparison. That way the weather won't play (in a perfect world) a factor in your bragging rights. In reality, a dyno operator can change the rate a dyno allows accelteration (2 second, 3 second intervals/rpm related) to cheat your numers + or - depending on their illicit reasons. The good thing here is, when people do this, they get caught. The dragstrip don't lie.
Finally. The key reasons for using the dyno are to tune, and to compare a part's performance on the same vehicle-the same day-in the same conditions.

 

They should have corrected the results to "SAE" or "STD" conditions, which (almost) eliminates the affects of temperature, humidity, altitude and barometric pressure. If they didn't correct your numbers, they didn't give you what you paid for.

This shows the fallacy of chassis dyno numbers..... whatever it takes to get a magic number, in this case 600HP. In reality, the cars true performance on the street or on the strip will not be one bit different just bacuse the dyno sheet shows a larger number.

 

I know. But a decent dyno sheet with over 600 to the wheels is always good to show off anyways.