Anyone tune on a chassis dyno ?

I will probably have my car back together right about when it's cold and snowing....thinking about chassis dyno to get it dialed in. Any one do this ?

We tuned our Duster on a chassis dyno. Got the tune close, but didn't keep beating it to death to find every last HP.

However, when we went to the track we had a good starting point, which we wouldn't have been near as close to without dyno'ing it first.

Ended up with 650 whp on motor, and 905 whp on nitrous.

If you have a high stall converter you will have limited info. Forget the numbers until the slip is minimal. The actual hp & torque numbers don't mean anything - just look at differences run to run.

One time I made 26 pulls in a half day. At the end of the day initial tune was spot on and cracked a head while tuning.

I'm a huge fan of chassis dynos. They allow you to for the most part dial in your a/f ratio and at the same time, find out what kind of power you're making across the power band. Some people have criticism for chassis dynos and believe there are too many variables to accurately gauge real power output...and I don't want to entertain that argument here.
What I can say is that chassis dynos are great for tuning and I believe there is enough consistency with dyno brands, like dynojet, to feel confident about the power numbers the dyno reports. Converting these numbers to engine power at the flywheel is just an estimate based on drive train loss, but one could argue that (knowing) what you have at the wheels is the more important number.

I am dealing with a new engine combo to me, yes I want to get the a/f dialed in and the timing dialed in. I'd rather do it on a chassis dyno than on the track, still got to deal with getting 275's to work.

Chicken LOL

I use a chassis dyno a LOT. Did an EFI conversion on a TS car earlier in the year. The quickest pass it had ever made with carbs and two nitrous kits was a 4.16 in good air..........I did all the EFI tuning on the chassis dyno, including lighting both stages of nitrous. He put it in the trailer, headed to Dallas for PDRA season opener, with NO track time. First pass, right off the trailer with the chassis dyno tune, was a 4.17 @ 171. Has since been a 4.10 on two kits in really good air

I also tune Chad's car on the chassis dyno. It has 4 kits, but have only sprayed the two small ones on the dyno. It makes over 1400 to the tire on the first two

Do your research and talk to some dyno shops. The dyno must be a load dyno for sure. Don't tune with say a Dynojet inertia only dyno. Look for a shop with a Mustang Dyno or equivalent. See how they tune. Are they just doing your AFR. Do they adjust timing and retune accordingly. Do they just sweep test an step test under load. Hopefully both. Guys like Monte seem to have good handle on it. He has the numbers to prove it. Contact him i'm sure he can point you in the right direction. I personally like sampling individual cylinders with sweep and step tests with high speed 4-5 gas analyzer. But that's just me and my experience is EFI Harleys. I also don't agree with one AFR across the board is right or the Lean Best Torque theory. But YES a good chassis dyno tune is worth it.

Gets ya close and IF there`s an issue, it`s easier than in the car to fix.......

Chassis dyno is a good tool but you can get wadded up in a hurry if you aren't prepared. I added tie down points to my car as well as a couple of O2 bungs that were easy to reach so the car would be easier to get mounted up on the dyno. The chassis dyno works a lot better if you have a manual trans. You'll also want to use a radial street tire and don't be shy about putting some tire pressure in it.

Maybe you should do some research on Dynojets before posting.

I have and know what I like in a chassis dyno. In regards to a DynoJet dyno. I only reference them by their inertia dyno in my post. I just used them because of the brand is commonly recognized. But anyway if you can tune or know someone who can tune with a inertia dyno with no load control. Power to you or them. In regards to DynoJets load control dyno. Lots of people use them. I prefer a Mustang load control dyno. I like them because of the low inertia roller with. IMO better load control eddy current brake. The DynoJet uses Large heavy roller with their load control eddy brake dyno. I'm not downing DynoJet. They just are not my choice.

It makes my f**%ing blood boil when I read its inertia only about Dynojets.. I had an early model 248 , and it was loading as they all were. It had proportional air brakes that I could load the car against and hold it at tire speed, engine speed or % load.. I don't think the people I bought it from even knew it was capable of load holding. The new dynojets have the same load hold, or you can order eddy brake, that gives you real time torque output. The roller is 2 feet in diameter, its weighted, but serves several purposes: first it allows the the dyno to have a fixed calibration for cross dyno repeatability, that can't be monkeyed with, second is for contact patch, and it doesn't destroy sidewalls of the tires with excessive loading, really an important aspect when it comes to road racing.

You don't need radials, nor a manual trans to get good chassis dyno results. We dyno big tire drag cars all the time. All you need to do is put plenty of air in them, so it doesn't crush the tire and chunk it. Other than that it is a non issue.

The "inertia" dyno thing is just something guys toss around who don't know how to set their dyno's up for power. You can "lie" to a chassis dyno. All you are trying to do is control the rate of acceleration. So if you tell the dyno that the car weighs 4000lbs, when it really only weighs 3000lbs, you will get more control. Many ways to do it.

As far as the power numbers it spits out........I could care less. I am TUNING, not trying to get a sheet to brag to my buddies about. If I make a change and the power increases, we went the right way, no matter what the total output number is. That is really just a meaningless number

I brought my car to a dyno once, it was a "load" dyno...Every change I made to the car on the dyno that had it pick up there, slowed it down like crazy at the track. Needless to say, I am not a big fan of dynos, unless of course the load dyno had something to do with it

On the "adjustable" dyno's that's probably true.. The dynojet has no inputs beside the firing cycle degrees to set the tach input. I guess you could try putting the weather station stack in a toaster oven if you were so inclined to mess with the output, but the altered data would be naked in the run file.

Great way to sell dyno time, change correction factors, show the customer a positive gain no matter what the car really did..

My car has a racepak. I don't care what the dyno says honestly. I just st want to tune my a/f , timing and keep upping my nitrous until I have a clean "NO" jet tune in my plate. I really don't care what the dyno says.....
That being said,Mehta type of tie down points are required on my car .?

Can somebody please explain that one to me? If the car is stationary, what does the dyno care what it weighs?

The rollers provide resistance, so I am assuming that you can change that and change how it corrects itself.