M4 dyno test by Sportauto 465hp/577 nm

[JoeFromPA]

Ok, this has been extremely helpful. So here's how I'm interpreting this now:

1. This dyno is super legit and the next best thing to a real engine dyno done under strict standards.

2. I am totally unequipped to understand and compare this dyno to any sort of normal dyno I'm used to seeing (i.e. dynojet).

3. Once past 3200 rpms on this dyno, we are seeing a pretty reliable torque and HP curve. However, I don' tknow how the numbers truly compare to what I'm used too.

[Boss330]

Originally Posted by s62

Maha dyno does not assume anything. It measures the parasitic loss directly during the deceleration. This is how it arrives at the flywheel power.

The numbers are definitely legit.

Some of you would argue the numbers not because of the drivetrain loss but because of the torque peak arriving after 3000 rpm. This is normal. You can not load the engine enough on a chassis dyno to obtain the torque curve published by the manufacturer. The latter is obtained on an engine dyno at a steady state! For instance, the engine is brought to 1600 rpm, then it is tested how much 'braking' it overcomes, the number gets recorded. Then it is brought to 1700 rpm, then 1800 etc. all the way up to redline. The increments may differ, but when the resulting numbers are put on a graph it looks perfectly smooth, linear and angular. Yes, it looks so because it is obtained from egine dyno testing at a steady state!

The only way you may get maximum engine torque at 1800 rpm in the car is in top gear and full throttle starting at 1000 rpm trying to climb the Eiffel Tower. In other words, it would never happen!

Very good explanation! Thanks

[mkoesel]

If true, we are over 150hp/L (155, even) putting it in rare company and reaching the target so many doubted when the I6 engine speculation began years ago.

[Boss330]

Originally Posted by mkoesel

If true, we are over 150hp/L (155, even) putting it in rare company and reaching the target so many doubted when the I6 engine speculation began years ago.

Good observation!

[Powaup]

Originally Posted by mkoesel

If true, we are over 150hp/L (155, even) putting it in rare company and reaching the target so many doubted when the I6 engine speculation began years ago.

Damn that's nuts. What other car has as much hp/L? I can't think of one

[jc05e46m3]

Originally Posted by Powaup

Damn that's nuts. What other car has as much hp/L? I can't think of one

Mercedes CLA-45 AMG

[JoeFromPA]

Originally Posted by Powaup

Damn that's nuts. What other car has as much hp/L? I can't think of one

Mercedes 2.0 liter in the CLA AMG, Subaru and Mitsubishi have made 2.0 liters putting out around 150 hp/liter for quite awhile....probably a few others. By no means common, but also not a new achievement in forced induction in terms of specific output either.

[solstice]

The Ferrari F40 just make a hint more hp from a hint less displacement ( 478 PS from 2,936 liter ). Pretty fat that the S55 is that close to the both famous and infamous F40, now if they could just offer this engine in a 2400 lb car, welcome back F40

[CanAutM3]

Originally Posted by Boss330

AFAIK, you want to look at torque to the rear wheels when looking at shift Points. As long as you still are amking more torque at the rear wheels at 7000rpm in the gear you are in than at 5500rpm in the next gear, you still want to hold on to that gear.

Going by torque at the rear wheels all shift points are above 7000rpm, but quite a few are not at redline (more like at around 7200-7300rpm I believe).

Even simpler, you want to shift at the point where power in the next gear is at least as high as in the current gear (not considering engine inertia).

[hoffa3]

sorry but did we figure out why such a big loss in HP to the wheels?

[ASAP]

I think if you look at the price and all else included... the S2K will win the hp/L argument every time. It's an NA 4 banger that made 120 hp per.

[ASAP]

Originally Posted by CanAutM3

Even simpler, you want to shift at the point where power in the next gear is at least as high as in the current gear (not considering engine inertia).

Unless I am not seeing something... looking at the WHP graph; wouldn't that still be below 7K rpm?

[CanAutM3]

Originally Posted by ASAP

Unless I am not seeing something... looking at the WHP graph; wouldn't that still be below 7K rpm?

Looking solely at the WHP line on the chart, you are correct.

However, I don't know what to think about those WHP and LossHP lines on the chart. 30% loss at max RPM does not add up. There must be something else involved.

[ASAP]

Originally Posted by CanAutM3

Looking solely at the WHP line on the chart, you are correct.

However, I don't know what to think about those WHP and LossHP lines on the chart. 30% loss at max RPM does not add up. There must be something else involved.

I agree, something doesn't add up. But... if the whp curve is right; then there is a sharp drop in power very early on, much earlier than previously ever shown which is dead on with my expectations. We have no idea how the flywheel numbers r calculated either.

[JoeFromPA]

Originally Posted by CanAutM3

Looking solely at the WHP line on the chart, you are correct.

However, I don't know what to think about those WHP and LossHP lines on the chart. 30% loss at max RPM does not add up. There must be something else involved.

I think they have to be looking at loss in a different way than we are used too...

An efficient RWD platform on a traditional roller dyno is expected to lose ~12% between engine and wheels. Here we have double that as an actual observed loss?

To me that margin of difference means we are looking at loss in two different ways.

[CanAutM3]

Originally Posted by JoeFromPA

Yes but it doesn't mean we sitting here are interpreting it correctly. Does that mean the MAHA dyno assumes a >25% drivetrain loss on a RWD platform and that is accurate? Cause that's how I'm reading that dyno. And why is torque already pre-calculated at flywheel levels? Is it reading it at the wheels and then increasing it to account for a 25% loss at peak levels?

This is a common missunderstanding. Wheel torque numbers shown on traditional chassis dyno charts are fictive numbers that don't exist in real life. Those numbers are simply calculated by dividing WHP by the engine RPM

In reality, you either have wheel torque that is multiplied by the gear ratio and final drive minus the drivetrain losses, or you have flywheel torque without drivetrain losses.

My guess on the Sport Auto chart is that WHP and "losses" whatever that is are measured. Adding both gives flywheel power and dividing flywheel power by RPM gives flywheel torque.

[ASAP]

Originally Posted by JoeFromPA

I think they have to be looking at loss in a different way than we are used too...

An efficient RWD platform on a traditional roller dyno is expected to lose ~12% between engine and wheels. Here we have double that as an actual observed loss?

To me that margin of difference means we are looking at loss in two different ways.

That doesn't change the way the curve looks on the WHP line.

[CanAutM3]

Originally Posted by ASAP

I agree, something doesn't add up. But... if the whp curve is right; then there is a sharp drop in power very early on, much earlier than previously ever shown which is dead on with my expectations. We have no idea how the flywheel numbers r calculated either.

Yes we do:

FlywheelHP = WHP + Losses (P-Mot = P-Rad + PSchlepp)

[CanAutM3]

Originally Posted by ASAP

That doesn't change the way the curve looks on the WHP line.

I think it does.

I am not sure that the WHP number we see here can be correlated to WHP numbers we see on other type of chassis dynos.

[ASAP]

Originally Posted by CanAutM3

Yes we do:

FlywheelHP = WHP + Losses (P-Mot = P-Rad + PSchlepp)

Why are losses different across the top part of the curve? That makes no sense. The WHP drops, yet the flywheel remains the same even though it's a higher rpm.

[solstice]

It does seem from the whp chart that power drops pretty significantly after 6k rpm. It does look enough to create a feel of running out of breath ( I did not say jerk ) even if maximum acceleration might be with shifts at 7k rpm. This make me continue to believe that significant short shifting is the most pleasurable way to drive this thing.

[CanAutM3]

Originally Posted by ASAP

Why are losses different across the top part of the curve? That makes no sense. The WHP drops, yet the flywheel remains the same even though it's a higher rpm.

I have no idea how this dyno works and what the "losses" represent. But the math works, at 7000RPM for example: 240 P-Rad + 120 P-Schlepp = 460 P-Mot.

I think the only numbers that we can really look at to compare anything are the flywheel power and torque numbers.