Competition Dyno types and differences

[4xquadrod]

I am looking for a thread about the technical differences of a Dynojet vs. Mustang dyno. I thought it was here at TDR but I can't find it. Anyone know where I can read a good article on this?

 

[bgilbert]

Just gotta know who started the thread and it will make your search easier. Here ya go: https://www.turbodieselregister.com/forums/showthread.php?t=123151

 

[4xquadrod]

Thank for the reply, I am looking more for the technical differences on how the 2 styles work. Not so much on how the diesels react to them both. I'm thinking now that I read an article in a mag somewhere.


Thanks again!

 

[jwilliams3]

What ever happend to Jetenginedoctor guy?

 

[KLockliear]

Do you have a specific question? It's much easier to answer a specific question than to give a vague, all-encompassing one.



The Dynojet is an inertia dyno. Two 48" diameter heavy drums give a rolling resistance against the vehicles wheels. The runs are made by accelerating from one speed to another (ie, 50mph to 100mph). The difference in speed from the start to the finish, is divided by the time to calculate the HP created. Given an RPM signal, torque can then be calculated from these values.



Because the inertia doesn't change, and is not operator adjustable, the runs are extremely consistent and repeatable (as much as the vehicle is anyway). Simplicity is the key. Typical dyno run times from drive in to drive out can be as short as 5 minutes. The dyno is rated for 1500hp/2000ft-lbs.



I have used a Mustang dyno as well. They use small rollers (8-10" diameter), which have less contact patch. There are two rollers instead of only one, so you are also heating the tire twice as quick. Typically, these are only good for 400hp or so, until wheelspin becomes a problem. No RPM pickup - you have to do a test where you get into the gear you are going to dyno in, then hold steady at a given RPM so the dyno can calculate the MPH per RPM ratio.



Then, you can do a test where it uses eddy-current load to create the load. You tell it to accelerate from this speed to that speed in so many seconds. The problem I had was that it would accelerate quickly initially, then slow down the second half of the run to reach it's target length of time. This is just not representative of what happens on the road when you hit the throttle, IMO.

 

[jwilliams3]

Keith,

I am sure you know there are larger Mustang Dyno's with the one wheel option.

I do agree, I like the Dynojets better!

 

[bgilbert]

I thought there was only one dyno, Dave Dunbar's dynojet???

 

[Amish Elegance]

Thats allll we need.