Drivetrain losses:

Real km/h against tacho km/h:

Look here for dyno sheets with Subaru Impreza's.

The difference between 4 WD and 2 WD drivetrain loss.

My car has been on a dyno what could see the flywheel hp., and drive train loss.

The max. drive train loss of my vehicle was: 66 hp. at 167 km/h.

Because I thought this was very much, I asked the guy of the dyno, how this was possible. He told me that most of the drive train loss is due to the friction of the tires/road. The part of the tires is ± 75 % of the total drive train loss, he said.

So actually we can speak of drive train loss and wheel friction loss.

If we take these numbers and make an calculation, we see:

66 hp. X 75 % = 49.5 hp. loss due to the FOUR (measured) wheels.

So now we have another 16.5 hp. loss left, due to the drive train/4 WD tranny itself.

An 2 WD does have an average total drive train loss of ± 33 hp.

33 hp. X 75 % = 24.75 hp. loss due to the TWO (measured) wheels.

Now we have another 8.25 hp. loss left, due to the drive train/2 WD tranny itself.

If we drive on the road, an 2 WD car has to move 4 tires, just like the 4 WD, so now we get:

2 X 24.75 hp. = 49.5 hp.

And what do we see here: This is equal to the 4 WD car.

This calculation is showing us that the total drive train loss

2 WD = tires 49.5 hp. + drive train 8.25 hp. = total 57.75 hp.

4 WD = tires 49.5 hp. + drive train 16.5 hp. = total 66.00 hp.

Total loss on an 200 hp. car:

2 WD = according dyno results: 33 hp. total drive train loss, because only two wheels are measured. And 33 hp. on 200 hp. is making an total loss of 16.5 %. This is what you see at most magazines, but on the road it lookes like this:

2 WD = 57.75 / 2 = 28.875 %.

4 WD = 66.00 / 2 = 33.000 %.

Please note, this is an calculation with an 200 hp. car, at ± 170km/h. With higher speed levels, drive train loss is growing with the speed!

Of course, we do have a difference, ± 8 hp. or 4.125 %, but the total difference between 2 WD and 4WD is not as dramatic as some people try to make us believe.

The relation between turbo pressure and power.

If things go well you should get 10 % more power for every 0.1 bar more boost pressure....if things goes right

This 10 % more power should be taken from the non turbo version of the same engine!

Example:

2 Litre, 16 valve, turbo with 0.7 bar pressure delivers 208 hp.

If we crank up the boost to 0.9 bar, we should get 20 % more power.

So, 2 litre, 16 valve without turbo version does have 156 hp.

156 hp X 20 % = 31.2 hp.

If everything is going like it shoud be, this turbo engine, with 0.2 bar mere turbo pressure, should deliver:

208 + 31 = ± 239 hp. with 0.9 bar.

If this isn't matched with this turbo engine, than this does mean, this engine cannot handle 0.2 bar more pressure.

Now, we can do two things:

Lower turbo pressure, or:

Find the reason why this isn't matched, example: deliver more fuel or better exhaust or better air supplie, etc...

So, this is what people told me, if they were wrong, I am wrong. If you know better, please let me know. I am never too old to learn.