I think all of us would like to have a DynoJet or Mustang dyno in our garages, but the $25k-35k price range keeps them out of reach for the most of us.

Has anyone had any experience with the Home Dyno kit? http://www.charm.net/~mchaney/homedyno/dynokit.htm
I ordered the Road Dyno version - complete kit for $149

I ordered one yesterday because I have extra play money and what little I've heard about it, it's all been positive.

Supposedly within ~5% of a DynoJet and very consistent results. I'm not really looking for bragging rights for HP/TQ numbers so I think it'll be a good tuning tool and see if <insert new hotrod part here> actually makes a difference.

Anyone used one before? What about the skeptics?

wouldnt touch it...listens to sound ...kinda like the guys who say it has 500 hp bc of the flowmasters

look at the road dyno kit...... it does not use sound at all. i'm interested in what you guys think as well..... may be a good tool for fine tuning.

I've been doing a lot of research on dynos lately - my friend is opening a shop and handed me the duty of doing some research for him. It functions very similar to a DynoJet.

The DynoJet is an inertia dyno. It measures how long it takes to spin up the drums that weigh xxxlbs and extrapolates horsepower, and then torque from those numbers. With the Road Dyno (Home Dyno too), it's measuring how long it takes to move your car at WOT. You punch in the details of gearing, tire size, frontal area, weight, etc. and it calculates horsepower and then torque from that.

This isn't comparable to a Mustang dyno which is hydraulic. I hear a lot of people talk bad about them because their numbers are lower, but actually, it's the DynoJet numbers that are exaggerated. The Mustang dyno measures Torque, then calculates horsepower - the way it should be. The DynoJet *calculates* horsepower, then extrapolates torque from that.

Enough of my banter about dynos for now. When it comes in, I'll give it a full review. $150 for a tuning tool is A-OK with me.

BTW: DynoJet and Mustang both record the spark impulses and read it as analog audio, the software finds the peaks to determine each spark.

I don't see the difference in calculations. How is one more accurate than the other?

HP = (TQ * RPM) / 5252

TQ = (5252 * HP) / RPM

When I stick numbers in my calculator I get the same answer no matter how I do it.

I'll have to find the doc that explained it (there's a LOT of paperwork explaining dynos I've read lately)

Basically, a hydraulic based dyno is more accurate because it actually loads the car down and measures the torque required to spin it. An inertia based dyno will produce slightly inflated numbers because it's basically spinning a flywheel. If you have a HP dip, it will not show up because of the flywheel effect.

I'll dig around when I get home and find the info for ya.

I'm not saying either one is good or bad, both are great for tuning, but for the nit-pickers, a hydraulic based dyno is the way to go, lower numbers or not.

Hydraulic pros/cons:
P-Ability to create different loads on the car
P-Great for low speed troubleshooting
P-Helps in tuning across the board instead of just peak HP.
C-Takes a little longer to extrapolate data

Inertia Pros/cons:
P-Consistant. Very close numbers every time.
C-Drum acts as flywheel, hiding performance problems
C-Can't increase or decrease load

The only reason I lean towards the hydraulic, even though more costly, is it's ability to apply load to tuning.

For a "road" dyno ... I've been hearing very good things about the G'tech. It's quite simply a calibrated accelerameter ... but it works.

Here's one that I've thought about for a while, is a home-made engine dyno. When I was in college we used an old style dyno ... before we got our SuperFlow.

Basically there was a hydraulic coupling attached to the flywheel. Attached was a 12" rod, connected to a potentiometer. The rod gave you 1ft, and the potentiometer measured lbs ... Thus you had lb-ft torque.

Here was the really tricky part ... you loaded the hydraulic coupling (and engine) by adjusting a water valve, more water, more load. It was hard as heck to actually control engine RPM's very well ... and record torque data.

Now the SuperFlow works identical, only difference is that it uses a computer to control waterflow and engine load ... and record torque and RPM data.

Now given that information has anyone tried to make a home-made water-brake dyno?

Neal

Interesting. We went with the inertial dyno for much the same reasons, repeatibility, ease of operation, ability to load at any rpm or mph. A loss of power at any point will show up on the graph. It's not just about peak numbers at all.

I'm not sure how the inertia dyno is measuring hp directly. That doesn't seem possible to me. You take the speed change per unit time and then you can calculate the accelerating torque required to produce that speed change. From the speed and torque you then calculate hp. That's how it's done in any calculations I've seen.

I even worked on a program to calculate the acceleration profile of electric motors which works about the same way, but in reverse. Knowing the torque, the program calculates the incremental speed change for every 0.01 second.

I also thought the Mustang used something like an eddy current clutch or some other form of electrical brake, not hydraulic.

Peter

Originally posted by Peter F.:
I also thought the Mustang used something like an eddy current clutch or some other form of electrical brake, not hydraulicEddy current dynos fall under the same category as hydraulic dynos as far as the ability to apply a load. (At least, I grouped them that way anyway)

I didn't mean that they were different in the basic methodogy behind the test performed, I just meant that the Mustang is basically an electric brake.

I wonder if the Dynojet numbers are inflated because it calculates the average torque for a certain delta speed and then uses the ending speed (rpm) value to calculate the hp. hp is proportional to rpm so if a slightly high rpm is used for the calculated torque value, the hp will be inflated.

Peter

The calculation is done far too frequently to get much error due to the change in rpm. If you sense the rpm off a plug wire, you get a pulse every .02 seconds.

Well, the kit came in the mail today. Really simple to use actually.

Weight
Gearing
Tires
frontal area
weather

With the data from the list above punched in the program, my beast of a truck (96 Ranger 3.0V6) put down this dyno chart. The numbers don't seem too far off. I don't know what the dyno for a 3.0V6 truck engine looks like, but I do know peak HP for '96 was 147HP and 170lb/ft of torque. I have no idea at what RPM though.

I'm going to try the unit out on a car that's been on a chassis dyno and compare.

http://www.team140.com/dyno.jpg

Team, keep me posted on your results please. I am interested in that unit to combo with my wideband 02 unit. Thanks Monte