flexus

Well Injureer you've pretty much lifted up some of the fog then

-i don't think the people at the dyno really know what overdrive is (not that i do)
- the car somehow did hit some limiter before the peak (at about 5250 as you said). The last times i went to dyno it (when it was running bad more than 1 year ago) they tried it in 4th, 5th and 6th and the limiter came in right at the end of 5th and at about 3500 revs in 6th. Repeatedly.
- i dynoed it once before at the same place back when i bought it, in 4th. It did 190hp then. They overlapped the graphs now and i could clearly see how the HP curve went up further the last time (with 190hp) than now. They didn't have time to redo it in 4th now/. There was a clear portion of revs where it was limited now that had gone up before.

Injuneer

Is your car an "export" model? If so, might have different speed limiter setting than the "domestic" models. Maybe the "255" entered into the speed limiter field is somehow interpreted as 255 kM/HR (160 MPH). That would correspond to the numbers you are quoting for 5th and 6th gears.

You indicated "I have no idea about correction. There was another line down there tho which said -hp loss-." Can you type out the full data in that part of the sheet? Hopefully they didn't attempt to plot flywheel HP rather than rear wheel HP, assuming some sort of standard drivetrain losses.

"1:1" means the transmission is in direct drive. The power is not going through gears. The output shaft is rotating at exactly the same RPM as the input shaft. The shafts are locked together (involving gears, but not sliding friction). "Overdrive" means the output shaft is turning faster than the input shaft. Overdrive is used to reduce engine RPM during cruise conditions, and to improve fuel economy. In your M6 trans, the gear ratios are:

1st - 2.66:1
2nd - 1.78:1
3rd - 1.30:1
4th - 1.00:1 (direct drive)
5th - 0.74:1 (overdrive)
6th - 0/50:1 (overdrive)

flexus

Afaik it's not an export, it was registered here first in 1998 and someone in the US owned it before.

As i said they haven't sent me the chart yet, but it had a low angle line plotted down there which represented drivetrain losss, they said it's calculated after the car reaches max rpm by letting it engine break down to low RPM.

I did know the M6 ratios what i don't understand is why people call it overdrive and go all when it's just another gear like 1st, 2nd, and 3rd. It doesn't imply a different mechanism, just a different ratio...

Injuneer

But overdrive is a different "mechanism" from the direct (1:1) gear. It involves a small power loss because the gears are causing friction losses, and inertia losses due to the mass of the gears and shafts that are rotating. In direct drive, those losses will not be experienced. The other issue with running in O/D is the limited ability of the rear wheels to accelerate the dyno drum quickly. It's going to slow things down. That reduces the energy used per unit time to bring the rotating parts up to speed, since they are accelerating slower. Different gears will produce different results. You want consistancy in the way you test, because the primary value of the data is to see the impact of changes to the total system. You can only measure the changes if the test conditions and methods are the same for all pulls. The "correction" is important, because that is a standard method to correct your results to a standard air temperature, barometric pressue and humidity. In the US we use SAE ot STD correction factors. I suspect in Europe they will be using DIN, EEC, etc.

What they appear to have done with the "loss" number is a coast down test. That test arrives at a numerical value for the inertial portion of the drivetrain losses. But because the coast down test puts the loads in "reverse" from the normal drive direction, it tends to eliminate the friction portion of the drivetrain losses, which are the largest portion of the losses. I would suspect you got about 18HP loss on the coast down test.

flexus

Along with the 3.73 I'm getting a madz28 OBD1 swap, wonder if it will show on the dyno