DOES ANYONE KNOW THE DIFFERENCE BETWEEN A DYNOJET DYNO AND A MUSTANG DYNO?

I dont know what the technical differences are. Different brake system or maybe different math settings or whatever. But I can tell you Mustang dyno's generally give a lower horsepower number than Dyno Jets.

I believe the mustang dyno puts more of a strain (load) on the car, resulting in the lower numbers... Correct?

There is only one good dyno - the dragstrip!

I do like the dyno as a tuning tool, but I put little faith into the numbers themselves. Problem is that not all dynos are operated the same way, and there are ways to manipulate the results. I have to laugh about the comment about Mustang dyno's reading low (see previous sentence), and here's why: Just this last weekend at the L.A. Roadsters 40th Father's Day show (one of my favorites) I saw an interesting vendors display. Let's just say there were selling superchargers for late model G.M. trucks and SUV's, and the dyno results caught my attention. It was a before and after comparisson. Looking at the after of 405 hp would turn on nearly any gearhead - it was the before of 279 hp that made me ask questions. This was on a 5.3 liter fatory rated at 295 hp. So I made the comment; "flywheel hp right?". To which the answer was; "no, that is rear wheel hp". For a brief moment I asked what SUV on earth only loses 15 hp between the engine and those big heavy wheels? Sorry, but the parasitic losses of the trans, u-joints, prop shaft, locking differential, axles, and those heavy wheels is definately MORE that ~ 15 hp. They stood firm on their claims. When I asked about the dyno itself they said it was a Mustang dyno, and that really was the power that it made.

I still like dynos, I have done well beyond 100 dyno pulls for various tuning work on my own cars.

But the track is where it really gets proven. If it can't lay down the mph then it isn't making the power.

Thomas

There is a good article in hotrod magazine 2 months ago - get ahold of it, or search it on hotrod.com. A mustang dyno applied load in a more realistic way than the inertia wheel of a dynojet. The dynojet felt like it was accelerating almost as fast as first gear in third.

I'm not big into dynos, but they save time and money. And when you need to prepare for a race down south when your track and streets are still covered in snow, there is NO OTHER WAY!

Like said above, don't get hung up on numbers. THe main use I got out of it was to read plugs and see what the corresponding air/fuel was, also for nitrous tuning it was great because I could pull all the plugs quickly, make a change, run it again. To do that at the track, I would have to tow my car back to the pits (never done that before) so that I can jack up the car about 6" to get the rear plugs out.

I used a mustang II dyno at home with the dual rollers and it worked well -the dynojets have a single roller and I couldn't keep from smoking the tires naturally aspirated so nitrous was out of the question - on the mustang II, it worked good on motor but I exceeded it's 1000 rwhp limit instantly on the spray, the numbers bounced all over from 1000 to 2000 so don't know what it really made LOL but the plugs looked damn good!

N/A, the mustang dyno read 5% lower at home than the dynojet in memphis did. I need a tighter converter so I wasn't too concerned about the actual numbers but both were very repeatable run to run.

More important than the type of dyno is to bring lots of plugs and take lots of notes.

Yes, read the Hot Rod article.....not all chassis dynos are created equal.

I think however, that these chassis dynos can be good tuning tools. The actual HP isn't as important as the results you get when making changes.

I'm not sure though, how one keeps the engine at a constant temp throughout a day of testing. Temp will make a difference in the results.

You also have to know what the repeatability of the dyno is. 1%? 5%?

I am always wary when a magazine article declares a particular part a winner when it only made 4 more hp....is that really within the accuracy of the dyno?

The dragstrip of course is the ultimate test. But tuning there will likely be different than on the dyno. And the problems at the dragstrip are: changing weather and changing track conditions.

One thing I like about running an engine on an engine dyno is that you can tune it there, fix problems (oil leaks) there, and be sure that when the engine goes in the car, it's ready to put your foot to the floor.

Rock on!

Ron

Originally posted by Bomber '67:
I have to laugh about the comment about Mustang dyno's reading low (see previous sentence), and here's why: Just this last weekend at the L.A. Roadsters 40th Father's Day show (one of my favorites) I saw an interesting vendors display. Let's just say there were selling superchargers for late model G.M. trucks and SUV's, and the dyno results caught my attention. It was a before and after comparisson. Looking at the after of 405 hp would turn on nearly any gearhead - it was the before of 279 hp that made me ask questions. This was on a 5.3 liter fatory rated at 295 hp. So I made the comment; "flywheel hp right?". To which the answer was; "no, that is rear wheel hp". For a brief moment I asked what SUV on earth only loses 15 hp between the engine and those big heavy wheels? Sorry, but the parasitic losses of the trans, u-joints, prop shaft, locking differential, axles, and those heavy wheels is definately MORE that ~ 15 hp. They stood firm on their claims. When I asked about the dyno itself they said it was a Mustang dyno, and that really was the power that it made.
Manufacturers have been known to underate power. I mean u cant compare a rearwheel dyno number to a factory rating. Great example is the LS1 Camaro and the 03 Cobra (300 and 370 rwhp are the norm). Its obvious both arent losing only 5-8% power through the driveline. Then u also said it was done by a company selling a product, so who knows what they did to the vehicle.

Dynojet - Inertia Dyno
Mustang - Eddy Current

I used a mustang II dyno at home with the dual rollers and it worked well -the dynojets have a single roller and I couldn't keep from smoking the tires naturally aspirated so nitrous was out of the question - on the mustang II, it worked good on motor but I exceeded it's 1000 rwhp limit instantly on the spray, the numbers bounced all over from 1000 to 2000 so don't know what it really made LOL but the plugs looked damn good!

We've had cars well over the 1000hp mark on our Dynojet with no tire slippage problems at all. We've had a few with tire clearance problems creating a bit of smoke, but no slippage. The Dynojet roller is 48" in diameter. How big are the Mustang rollers? How does the Mustang dyno keep the loading on the rollers uniform when the car is under load? On our Dynojet, the car moves forward on the roller slightly as the force stretches the tiedown straps. I would think that keeping the car centered on two rollers would be difficult.

Originally posted by onovakind67:
We've had cars well over the 1000hp mark on our Dynojet with no tire slippage problems at all. We've had a few with tire clearance problems creating a bit of smoke, but no slippage. The Dynojet roller is 48" in diameter. How big are the Mustang rollers? How does the Mustang dyno keep the loading on the rollers uniform when the car is under load? On our Dynojet, the car moves forward on the roller slightly as the force stretches the tiedown straps. I would think that keeping the car centered on two rollers would be difficult. [/QB]Question - the 1000+ hp cars - where they big cubic inch, big torque? I have heard of smaller cubic inch blown cars getting high numbers w/o spin but I have been on two different dynojets with experienced operators. In memphis they tried several times to place the car in different positions on the roller, different air pressure, extremely tight straps, and it still smoked the tires. Nitrous was out of the question.

I'm not sure how the car stayed centered on the mustang dyno, but it did. The only issue was when I hit the nitrous the first time the back of the car slid out sideways - we put lateral straps on it and it was rock solid.

I checked the dyno specs - it has dual 19.75" rollers. It was a MD-600HP. I was the second car on it from new so the knurling on the rollers was very sharp so that could have helped. I'll find out the specs of the dynojet I was on also - I'm curious.

66 283, The newer Dynojets have better knurling on the rollers and can definately hold over a thousand horsepower and a Blown 572 C.I. Camaro made 1096 RWHP and 1100 ft. lbs. of tq. at the Fall Nationals on an older Dynojet, (Werx), in Springfield, Missouri last year but my sons Chevelle spun on the same dyno, same day at about 715 lb. of torque. The newer Mustang Dynos (model 1750) have one large roller like a Dynojet but still have a Eddy Current power absorber or can be had with the inertia wheel only the same as the Dynojet.

P.S. The two roller setups are very hard on your tires!

Question - the 1000+ hp cars - where they big cubic inch, big torque? I have heard of smaller cubic inch blown cars getting high numbers w/o spin but I have been on two different dynojets with experienced operators. In memphis they tried several times to place the car in different positions on the roller, different air pressure, extremely tight straps, and it still smoked the tires. Nitrous was out of the question.

The 1000+ hp cars are mostly big inch PSCA cars on nitrous. We have a knurled roller that's about 1-1/2 years old.

I'm a big fan of the Dynapack dynos. They bolt directly to the axles they "load" the car using hydraulic load brakes. You can have the machine run preprogrammed acceleration curves as you would an engine dyno. Some race teams program in a "track" and will run a simulated race on a car before going to flush out any problems.

They are more ackward to use and more time consuming to setup (jack the car up, take the wheels off, slide in the load units, choose the right axle adapters, bolt them up, then go), but they're great especially for tuning because you can accurately simulate loads and hold it in a certain RPM range if necessary, something you can't do on an inertia dyno.

Also, keep in mind, just like engine dynos, the dyno operator can make the thing read almost anything depending on what correction factors are plugged in. I have seen some VERY unscrupulous dyno shops; most recently someone brought a boat motor to my buddy's SF901 Superflow dyno. It dynoed almost 60 hp less than at the shop that built it. The first shop fudged the correction factors. graemlins/clonk.gif The engine owner was a VERY unhappy customer.

I wouldn't say chassis dynos are the "end all" of testing (the strip works great) because the guy running the machine can really throw the numbers off (either by mistake or intentionally) and wouldn't totally rely on their numbers, but they are great baselines for "before and after" type situations if you go to the same shop.

Troy

Originally posted by onovakind67:
The 1000+ hp cars are mostly big inch PSCA cars on nitrous. We have a knurled roller that's about 1-1/2 years old. [/QB]I'll have to seek one out like yours. Is it the same model that Harold Sutton mentioned? I must have been on inferior dynojets - I will find out what model/roller size they had.

***Edit*** page 86, Oct 2004. Latest edition of "MOPAR Action" (received in yesterday's mail) has an article that discusses the differences between chassis dynos as part of a feature on an engine buildup. I think he mentioned those names in that article. That magazine, by the way, beats Hot Rod and any of the Chevy magazines for style and content by a mile.

My $0.02

Hi 66 283, I was very impressed with your car from the Memphis video i watched. That 632 is a torque monster. I'm assuming you have a nearly stock style suspension on your '66 Chevelle. I've also noted that the ladder bar cars seem to want to pick up the front end more than the stock style and plant the tires better thus eliminating the tendancy to spin them on the Dynojet rollers. That black Camaro that made almost 1100 RWHP runs low 8's at 170 MPH but had no trouble putting down big numbers on the dyno as it has the ladder bar suspension. The newer Dynojet here at Performance Automotive can hold my sons car but is the only one so far that could and we didn't spray it. On the Werx Motorsports Dynojet at Springfield we had to go above 5000 RPM before begining the "pull" and then the converter didn't multiply the torque and a good reading was obtained (888 H.P.) with a 275 shot. (636 H.P. raw). My son has changed N20 plates from the "cheater" to a "Big Shot" and the car seems to have picked up some. He outran a blown mustang a couple of weeks ago that had run 9.44 but the "stang" got greedy and turned the blower up onto kill and couldn't get down the track.

harold,

Sadly, I have a ladder bar but I set it on kill and grossly overpowered the track. It was a last minute decision to run on friday night and I've seen better prep at home on "street" night.

my car just killed the tires all the way. I left on EIGHT degrees of timing and it hit the 7700 rev limit in 5 feet, then lifted, went into second and hit 7700 in another 5 feet, then dumped it in third and had to stab it twice and it didn't really hook up until 1000 feet. On playback the RPM decreased from 100 feet out until 1000 feet before starting to climb again. (spinning less and less until it finally hooked)

I am making some chassis changes this summer and am planning for mid to low 8's next time out.

I must have been on an inferior dynojet, smaller roller etc because we tried but I just spun. I also brought my car up to 5000, eased into the throttle, and then hit the nitrous.

I was spraying a lot more though, between 400 and 500hp depending on how you rate it but I exceeded the dyno limit and don't REALLY know what it made because the data is a scatter.

I was down more than 10mph at 660 from what I run at home then still went 157 so I think the car would have gone 165 if I hadn't lifted 4 times and short shifted to 3rd. It weighed 3932lbs so you can do the math!

As far as I know about the 273 hp out of the pickup truck, SAE NET horsepower (how we currently measure and advertise hp on new cars) is measured with the engine in the vehicle with all the accessories at the end of the driveshaft, but before the rear end and wheels.
Drag from disc brakes and turning the rear end parts could account for the difference in the advertised late model pickups power and the power at the rear wheels.

IMHO If you can't lock your converter at WOT or have a stick trans, chassis dyno #'s themselves are not indicators of power but only tuning tools-- obviously you will get some sort of range, but aside from that, its nothing you can use to measure actual power.
Engine dyno's I have some faith in (and probably a dynepack if I get the chance to use one) as long as the operator is legit. The guy who did mine said he could switch a few testing parameters and spit 70hp more out of my dyno reading, without ever touching the engine.

just my .02

matt