For mustang tq is a reflection of hp vs rpm, so it's the other way around. Adding resistance to the rollers will not change the distance that tiny load cell arm changes in relation the power calculation from the correct rpm. So you can set vehicle weight to 10k and still get accurate hp figures, albiet in manner only experienced in tractor pulls.. Think of it as artifical inertia that is NOT measured by rpm vs. time but with a load cell. Then think of hp@50 as just an adder for that to simulate wind resistance as speeds increase as well as rolling resistance from the tires, designed to work specifically with the EPA default coefficients in the . INI file.. You can find them if you search [epa in that config file. Mabye if you go to some extreme weights you will get different numbers, but that would probably not happen on NA cars, and most likely only happen because the tune or turbo is not operating at normal conditions..

 

Great thread! Its funny how some tuners will post up dynographs of say 350whp and some people think their tune or mods are the $hit yet in reality their gains are the same or less than a tuner who posts up a graph showing a peak of 300whp. You have to first dyno the car bone stock and get a baseline before anything, otherwise you might be severely disappointed when your high whp car isn't performing like you think it should be. Also, I feel a lot of people look over the power under the curve and just look at the peak #'s. Big mistake.

 

its oke those guys usually doing nothing but show dyno charts with peak numbers... LOL

 

So how useful is the 'vehicle' coastdown test calibration for the parasitic losses vs the default curves? The default MD curves were only performed to 80mph when we received ours.

 

It becomes more usefull as the dyno gets older. 80 mph is fine. CFR states 50-40, 40-30, 30-20 is what is mandated if I remember correctly, although it is meant for transient driver trace emissions tests. Every dyno is different in the same sense as our cars..Keep up with maintenence and you should be golden..
*edit*
Now that I've re-read your post I think I know what you are asking, but the vehicle coastdown is different then dyno coastdown for parasitic check. I was talking about dyno coastdown. If you want to do vehicle the best way is to do it on flat ground in neutral. If you want to get the times and give me weight of your car I have a spreadsheet that gives me ABC coeff. and hp@50. This is more accurate then using frontal area and guessing rolling resistance ect. which is how they list vehicles in the pdf list. If you want to give me the data I'd be happy to give you the numbers to try, then you can verify by doing the same check with the vehicle on the dyno..
50-40, 40-30, 30-20 times
Vehicle weight as accurate as possible

 

In order to get accurate data on the Mustang the parasitic curve needs to be calibrated past or up to the top MPH that you will be seeing.

IE- If it is at 80MPH then you will want to take it to at least 100MPH. I have set the measurement in Supras and such up to 150MPH just to sure that we have enough room to get accurate measurements. Mustang has always told me that past the parasitic curve the numbers are not as accurate as you are not factoring in parasitic loss which seems to be big on the Mustangs.




Mitch

 

Just run the car at the drag strip. MPH is a great indicator of how fast a car actually is :-)

 

Yeah, the first thing the trainer said when he was looking through the settings was "Hmm, they only went to 80MPH when they setup the parasitic losses. Strange." I set it to 110mph and let it coastdown in neutral like the parameters suggested (with our EvoX) but the parasitic power curve was insanely high compared to the default. For example, the default curve was at 50hp@80MPH while the measured curve was at 80hp@80MPH. I will read up on it and do some more research, thanks.

 

Appreciate the info. Great read.

 

intersting. Dyno should be used for tuning.

 

Great comparison John. This is very helpful for the community.

Thanks,
Martin

 

That is always the best test of how much power the car is making.

Dyno's should just be used as a tool. I never understood why people get all hot and bothered over dyno numbers. I'd much rather get all hot and bothered over trap speeds.

 

wow so in theory i would make 520 on a dj since i made 463 on a md

 

figured i'd share here since i'm in a similar power range to a number of you folks.

had my stealth on a mustang dyno yesterday, made 432hp and 421tq.

tuned it on a dynojet 2 weeks ago, made 457hp and 424tq.

was cooler and a bit less humid 2 weeks ago... was surprised at the relatively small difference between the two.

 

I don't think I've ever actually laughed out loud while reading this site before.