1- if they were using the "wrong gear" why did the results look so close to expected?

2- Just judging from dyno sheets I've seen on cars w/autoboxes there is some correction for not being in a 1:1 gear. The graphs are comparable in all gears leading me to think there are (?) software corrections or something to account for this.

I still maintain the real test is on the road. If two cars do a punch-off, say 3rd from some speed to redline, then we know (especially if they are the same model). 0-60 or 1/4 starts to involve driver error - road racing inducing the most driver error possibilities (and interest, IMHO).

well, I've learned a lot so far. Any intentions of backing up this data with some on the road testing? ;-]

 

on number one..

I saw alot of people using 15% correction factors for the quattro cars... which is a little forgiving..

on the quattro your looking at more like 25%... and on the FWD maybe 15% if lucky but probably closer to 20%...

lets take the stock 180fwd shall we? 161 hp. Using the forgiving (but most likely way off) 10% you get about 180hp at the crank on the nose... which looks right eh? But as I said... your most likely more like 15 to 20% drivetrain loss on the FWD... Lets take 180 crank hp and work drivetrain loss from there with 15% drivetrain loss you would be around 154 at the wheels, with 20% drivetrain loss you would be at around 145 at the wheels.

Those numbers are more representative of what The car would have dyno'd if done in 1:1 (4th gear) as it should have been done. The very forgiving 10% drivetrain loss correction makes up for the overrated wheel hp figures given by dynoing in 3rd gear.

not sure if that makes sense or not?

basically.... Correctly corrected with a more realistic drivetrain loss gives you about what it would have dyno'd if done correctly in 4th gear or whatever gear those damn things are at 1:1 in

LOL

 

I agree, TTroll: If you're trying to figure out what the car will do on the road, drive it on the road! But you run into the same kinds of problems with testing consistency, standards, stuff like that. And assembling a mess of cars in a place where you can do high-speed road testing is a challenge! (Quattro Club driving schools are a good way to do it.)

Plus, real-world road tests are punishing on a car. Drag launches are tough on clutches. Road racing is tough on everything. The dyno is much more gentle, convenient and safe, although it's obviously just a simulation of really driving the car.

--Dan<ul><li><a href="http://www.machvw.com">Mach V Motorsports</a></li></ul>

 

Dan,
One doesn't have to do race launches. In my street racing days we always did rolling starts (punch-off, if you will). Sort of like cruising with a guy on the freeway and then hammering it.
I guess all testing situations have some challenge to make the test repeatable - even the dyno situation is not perfectly repeatable. Nor available all the time.
D,
The absolute # is basically worthless. So many factors determine "drive-ability" that any given # is just a #. (Unless, of course, the game is to have the best dyno #.) The comments I have heard from TTers about how much smoother the car is mean a lot more.
example 1: a small motor making 250hp @ 8000 - with the torque peak @ 7000.
example 2: a big motor making 250hp @ 5000 - torque peak @ 2500.
Simplifying to extreme - both give the "same" potential performance. Which one is going to live longer? Which is easier to drive on the street? Which would give better performance under normal conditions? (few of us cruise to the market @ 5500rpm)
Besides they were all tested under the same conditions (right or wrong) and what they wanted to know was which exhaust and/or chip works.
just a few thoughts of my own.
hasta

 

I spent some time reading the dyno posts today, and came away with considerable information, as well as some mis-information, and some theories expressed as fact.

As strongly as you support your view, which is challenged by others who are either in the industry or know the science, you are, in my opinion, firmly lodged in the "Don't confuse me with any facts, my mind's already made up." camp. It's your way or the wrong way. As someone here said in his signature, minds are like parachutes; they work better open.

This subject of driveline and chassis dyno efficiencies is not a black and white issue.
If you have not, reread the others' posts and the links. Please try to do it with an open parachute.

You seem to have a great deal of knowledge. Many of the people here do too. I, for one, now find myself questioning your *facts*. In other words, you are losing your credibility with me. I hate it when that happens.

 

a quote from a friend.... who's been dyno'ing cars for a LOONNGGG time in detroit

"We always want to run in whatever gear is closest to 1:1 in order to reduce the effect of transmission ratio on torque output and gear reduction losses. We do this all the time just as another way to be more consistent and accurate."

that is ALL i'm saying... although sometimes I cant get things to come out the right way. That is not a theory...it is a fact. You can call any established dyno shop thats been around for years (hell I'll even give you phone numbers)and has experience with several different cars (race and street) and ask why you want to run in whatever gear is closest to 1:1. Call LaRocca performance, dynotech racing, detroit speedworks, Dyno Edge... johnson motorsports (that guy is a master on the dyno)

sorry if I come off as a bitch or whatever.... but I come from a group where dyno's and "dyno days" are a daily commonplace event... and the 1:1 thing, and the reasoning behind it, is common knowledge even among those that havnt had their car dyno'd. Driveline percentage losses are also a commonplace knowledge. Yes if you want to get into picky detail... you can get into tire pressure and diameter discrepencies and oil viscosity and rotational mass and on and on about how it could effect things as well. As you said.. that IS a black and white area, and i'm going to leave it as such. But the subject of the 1:1 gear run and the effects of anything other than, are quite commonplace knowledge to those in the industry.

If that causes me to lose credibility with you, fine by me.

 

heard