9 replies to this topic

[Rexx Havoc]

I'm re-pondering investing in a chassis dyno and branching out into that area

6-7 years ago I spent some time researching chassis dynos for asm inspections with a possibility of using it for diagnostic work also.
Now the interest is bubbling again... the dynapac 4000 upgradeable to 4wd sounds interesting
Allthough I have no experience in it, I think there would be a small swell of just curiosity seekers to begin generating interest in it and then aggressively learning the info necessary to offer tuning ... especially with people changing thier own components and building packages that make proven power.
Not to mention the portability to go to track days and the sort

My question is what experience do people here have in different chassis dynos and thier pro's and con's
the dynapack seems head and shoulders above the competition when it come to convienience and repeatiblity of runs
It almost seems to be the the only sensible choice and other dyno's in that class obsolete

what are the drawbacks of this system

thanks

[gt3rsr]

Rexx, I have ony used an inertial/water brake unit (land and sea), but have seen the dyna pack unit in action. In conversation with the owner, he echoed my concern: setup time. It does seem to take a fair amount of time to get a vehicle set on the thing, but perhaps as your familiarity increases, set up time goes down. On the upside, portability is a great thing, as is the ability to run AWD cars. With the market seeing an increasing number of youth turning Evo's and WRX's into wing-laden rolling grenades, this could be lucrative. And humorous.
Safety wise, I think I'd be more comfortable with a dyna pack unit. Hard for me to really relax on those rollers, especially with a FWD car.
As far as 'accuracy' goes, I think any dyno is as good as the guy operating it, maybe less so. Others here, like McGuire, have far more experience and are more intelligent then I, so look for input from them.
I have heard the sales pitches (in terms of accuracy) from both the dyna pack and the roller guys; none of them convinced me of the merits of one over the other. Good luck with it, hope you have fun with the thing.

[Greg Locock]

When you run twin roller dynos do you use slave tires? You should.

[Rexx Havoc]

When I was looking into the emmision testing based dyno. I had the spx corp agree to test my own (borrowed) vehicle on the dyno.
we went thru the emmision testing phase neatly and efficiently without much effort required

but once we decided to do a horsepower run, the car was nervous on the rollers with the tires getting very hot and smoking. We resecured it and tried again, finnaly unimpressed we decided to forget about trying it. Ultimately the dream died with the hopes of running the vette at full song.

After reading about the dynapack it rekindled that desire to get into dynoloading a car for driveability and eventually performance loading

I've developed a reputation for fixing the unfixables and see alot of cars from other shops, but the idea of not having to drive a car above the speed limit on limited visiblity roads all the while looking at a data readout on a scanner and occationally a lab scope ... is to say the least inviting.

[Rexx Havoc]

Quote

Originally posted by Greg Locock
When you run twin roller dynos do you use slave tires? You should.

i'm unfamiliar please expand

[Rexx Havoc]

Quote

Originally posted by gt3rsr
none of them convinced me of the merits of one over the other.

please explain why you were unimpressed with either the roller or direct coupling

[bobqzzi]

The dynapack really is superior. My experience is a 2wd car can be set up in about 15 minutes. It offers excellent control and allows you to do most of the stuff you could on an engine dyno.
Since every shop I've ever been in is tight on space, the portability is really useful from an economic standpoint.

My next choices would Dynodymamics and Mustang. The dynojet is of much more limited use.

[McGuire]

No #@*& rollers, I like it already.

Potential for improvement in any chassis dyno installation: the engine cooling/fan setup. If you can devise an accurate and consistent mechanism for controlling the airflow at the front of the car you can go a long way toward producing more real and useful numbers... especially on all the cars running around these days with the great big air/air intercoolers hung on the front.

[Greg Locock]

When you do a full throttle run on a twin roller dyno you need to pull the safety straps down tight.

This forces the tire belt into reverse curvature on both rollers. This severely weakens the tire. As you point out, overheating the tire is also common, this again will weaken it.

Our SOP is to use slave tires on twin rollers, there again, this is the first place I've worked with a twin roller dyno, most places I've worked have a single 2m dia roller, which is better for noise work, but not much good for full throttle runs.


The hub mounted dyno sounds better and better.

[J. Edlund]

Dynapack seems very similar to Rototest's dynos. I think Rototest was the first hub mounted dyno and they are used by some major car manufacturers (for example DaimlerChrysler, Volvo and Volkswagen).

From what I've heard, Dynapack is kind of a Rototest "light", cheaper but with less features. Both systems are hub mounted, hydraulic and portable but Rototest also have a model called "Dynamic" which uses AC motors instead of hydraulics.