Question ? How does a tuner know, or better yet - the customer know - that the dyno #, they were just told is accurate ? There's all this talk of one dyno doing that, the other "SAE" corrected one doing this ... etc ... Anyone wanna tackle the issue ? :confused: :D

 

How do you calibrate a dyno? Good questions! Try several dynos of the same model and type, at the same control conditions as in a lab, then you may get some conclusive results. Or just take it as a point of reference and brag on the forum! :) :) :)

Good Luck!

 

I have never witnessed a dyno-does it beat on the engine by excessive
reving or rapid acceleration through the torque curve?. Could a local dealer do it? How much? Thanks- Tom :eek:

 

I think as long as you go have your car dyno'd where the operator does not have a vested interest in having your car come out with high hp #'s you are ok. It is a good tool to give you a base # and then make your changes and re-dyno to find out if your changes were effective.

Track times are what really matters.

 

For the price of two Dyno sesions you can buy a G-Tech Pro and get your own results with a consistent baseline.
Jeff

 

It's the equivilent to flooring your accelerator in fourth gear and running up to redline on the road. Won't hurt your car any more than that. A dealer could do it if he had a dyno, but they don't have dyno's at dealers. Most performance shops that have one charge about $70 for two or three pulls (they run them about a minute apart). You can usually get them once every couple of months to set up a "dyno day" where they will do it for half price if you get minimum of ten cars.

 

Just had mine dyno'd for the first time. I stood there and watched and afterwards the machine spit out the sheet. I dont think the operators can mess with the graph that comes out other than maybe dynoing in a lower gear to get fake numbers. The only sure way to artificially inflate numbers is to go with smaller diameter tires. For the dyno to be accurate, it has to be performed in a gear with a true 1:1 ratio. On my ZO6 it's 4th gear. If I were to go with smaller diameter tires, I would get higher dyno numbers. Just the opposite happens it you go to larger diameter tires.

 

Let's be straight up here.

If all an operator is really trying to show horsepower, you can tune the car excessively lean (you wouldn't drive it on the street this way) to push the high end of the rwhp range, and then "detune" it before they give it back to make it safe. This can show higher numbers than what you will get.

Second, simply using a MAFT, I've made over 20 rwhp by simply running the car rich on the dyno, and then turning around and running it lean (2% rich and a couple of pulls back to 4% lean).

The size of the rear tires used can effect the torque numbers.

The long and short is you could if you choose, mess with the dyno numbers. Personally I've never seen it done at any shop I've watched dyno's being run. The changes necessary to make the high numbers we experienced were part of a learning experience on how the PCM resonds to AF changes and simply experimenting with the MAFT and how the LT Trims offset it with some normal driving very quickly.

The key is to autotap your car before, during and after the dyno run and look at your o2 numbers and LT Trims. These will be the tell tale signs.

Hope this helps. I'm sure kewlbrz can add more insight.

 

I was told that by simply adjusting the atmospheric conditions in the computer, (temp and humidity), a shop could get the numbers to "dance".

 

There are not many dyno's that you can do that on. Most of them are locked into a weather station that reads actual barro and temp and humidity...
Whos dyno can you manipulate the correction factor of????

 

Wouldn't want to say as I have no real proof ...

I understand that some of the older dynos that give the operator the ability to input the numbers manually. There are not too many of those and I also understand that the newer dynos are set up like you said. I would say that the majority of dynos are correct and the operators are honest.

I would also add, based on my experience, that you should get your car dynoed (if it matters to you) on two different dynos, under similar circumstances, just to be sure there are no large discrepancies.

 

Tire pressure will manipulate data as well.

RG

 

I also heard this....in what way?

 

As part of my new "no controversy" forum attitude, ;) I have stayed away from these type of subjects, ....... but, I can't help myself with this one, especially being known as the "DynoKing" :lol: . If someone really wants to fudge with a dyno, they can, but, for the most part, people just don't do it. Their's just no real advantage. People usually start the "fake dyno" theory when a tuner comes up with abnormally high #'s, just like we did on my car. That's why I offered to dyno on several different dynos in front of whomever wanted to watch. And guess what, I got the same #'s everywhere, with the usual tolerances. Dyno's should be taken with a grain of salt though. While they are not the end all, they are the best barometer to measure by IMO, if you know what you're looking at. Some people disagree and say track times are what counts. IMO, track times are too subjective to variable conditions, like weather, driver skill, track prep, tires, etc. An SAE correction is pretty much accurate as you're going to get. I'm sorry, I'm not going to tear a beautiful car apart, just so I can "legally" run my car in the 1/4 mile. If you do, that's great, but don't hammer the guys like myself who don't. To each his own. That's my story and I'm sticking to it. :smash: :D :cheers:

 

This is a total myth on "regular Corvette street tires". We did this test on my car, with Yokohama AVS Sports, raising the tire pressure from 24lbs to 42lbs. We picked up 0 hp and 0.5 TQ. Racing tires, which usually have tremendous sidewall flex, can make a difference on the dyno most definately, but not regular street tires. :cheers:

 

I think instead of looking for dyno improprieties (which I suppose are possible, but feel are not very common) you should pay very close attention to the details of particular setups.

There’re so many little (and sometimes not so little) things to “watch for”
I’ll give a few examples for NA application:

<LI> Cam: Cam size, hydraulic vs. solid
<LI> Heads: LS1 vs. LS6, Level of porting, valve sizes
<LI> Headers: We have a wide range of headers aval. now: shorties, 1 5/8, 1 ľ, 1 7/8 long tubes, different tube lengths…
<LI> Exhaust: Cats vs. No Cats, diameter of the pipes, through the mufflers vs. cut out
<LI> Intake: LS6 vs LS1 vs. custom
<LI> Other: Things like CR, timing vs. octane used make a pretty significant difference….
Etc…

As you can see all those “little” things can make a extremely huge variance range between “similar” packages.



[Modified by EuG, 1:07 PM 2/21/2002]

 

I agree with EUG that you have to keep an eye out for all the little details before you go comparing one package's dyno results to another.

A few VERY IMPORTANT things to keep an eye out for, especially on head/cam package dynos, are Compression Ratio, what RPM this max HP number was achieved at, and what octane of fuel was used.

It isnt hard to squeak more power from a heads cam package that is cammed to peak in power at 7400rpm with a 12.0 compression ratio and 104octane. Would it be realistic and reliable to make power in this way on a stock bottom end when longevity is a concern? :nono:





[Modified by MattG, 1:17 PM 2/21/2002]

 

One aspect of the dyno compared to real road behavior, is that the load a dyno puts on the rear wheels is different than the load the car will have on the road.

Another aspect of dynos is that software revisions (good or bad) can change the way a dyno outputs numbers.

As Bill said, to be assured of optimal tuning for road performance (not dyno performance), OBD-II diagnostics of real world conditions are needed. Dyno tuning will get you real close, but because of many variables will not be optimal for the road or track.

 

Thank you Kewlbrz!!!

I have tried to tell a few customers that dyno tuning is not as good as road tuning and I was met with nothing but sketicism. Most though I was saying that because I do not own a dyno, although we use the shop down the roads dyno very often....

Anyway, Thanks,

 

tom you are in look. A dyno day is set in NH in April. Look here http://forums.corvetteforum.com/zerothread?id=241907