Info about power loss to rear wheels and my NEW M5 HP numbers. - The Unofficial BMW M5 Messageboard (m5board.com)

Apples · 4th November 2001, 06:47

I found out from the techs at Nowack that there is a 40hp loss at the rear wheels for the M5.
I was of the thought that it was more of a percentage factor.....wrong .......but the loss you get in the drive shaft to the rear wheels stays a constant, no matter what power the car has.
This only applys if all of the drive shaft/diff/wheel size/ wheel weight are same as stock.
The only very slight difference is that they use BBS LM 19 for their dyno demo car. They would be of a very similar total height and weight to the OEM wheel/tire package.
The engine i sent them only was running with a total of 390hp max.
I had some blow by in the cylinders as some of you may remember a few months back, and this had let quite a few horses out of the gate, i think around 30hp The reason i say 30 is that i had also reprogrammed the ECU to add the OEM 394hp which SHOULD have given me about 420 hp.
I think that the loss was because of a weakness in engine rings and that it needed a better and longer run in procedure.

Nowack sent me the dyno of the new engine the other day and they said it's max was 470hp at the rear + that 40hp = 510hp.
They also said it was the strongest one that they have built yet.
I asked how it run out on the road and he (Stefan) said that it was brutal from 4000rpm onwards. All he kept saying was that it will punch you into your seat from then on..............sounds good to me.

That measurement (510hp) was the max the car would get sitting in a stationary position on the dyno. They said it would find around an extra 30hp when driven at high very speeds 150mph+ because of the air being rammed into the engine.
Boy i wish we had some unrestricted roads.
That's it for now......time to sign of from Down Under.
APPLES

Bart Carter · 4th November 2001, 09:13

Apples,

I have thought for a long time that HP loss after the Flywheel was more of a flat number, not a percentage. I usually figured 45 HP for a high performance car. There are a lot of experts that use a percentage. Of course they usually give a range, not an exact percentage, like 15 to 20 percent.

I can see increased friction due to a heavier application of torque, but not as that high of a percent.

DrJimM5 · 4th November 2001, 16:00

If the 40 HP loss is true, then there may be multiple M5 engine problems. A few of us tested our cars together and did no better than 324 RWHP, with most runs being less than that. I wonder if the blow-by that Apples mentions is a common thing that may be affecting multiple cars. Anyone have any idea how it can be tested for?

Jim

Bart Carter · 4th November 2001, 19:21

Jim,

I remember that there is some problem about getting an M5 to run on a dyno above 6,000 RPM due to its program. Is this accounted for? Does this happen?

If this was so, it would indeed account for lower readings.

If you compensated for this, how is it done?

Or, oh-my-God! Maybe M5 clutches slip under load!

Maybe I shouldn't joke about this.

Seriously, is there this 6,000 RPM dyno ceiling?

Apples · 4th November 2001, 19:42

Dr Jim...
I don't like to here you say those sorts of things Jim. But as you may have thought there my be a few different things that don't really show the TRUE power of the engine.
The dyno that you all may have used may not have been calibrated properly, operating temp of engine and other parts not warm enough. I don't really think that there would be any cold engines on the dyno.
Poor conditions for doing the tests, hot /humid.
The person running the test would also make a difference.
I think all tests must be carried out in 5th gear to have it a 1:1 drive to the final gear. I had mine tested a few months back and it was ran it 4th gear......i don't know how much off a difference that would make??
I asked one of the service guys at the shop i go to if you could find out if there was any way to test for loss of power, i asked if a compression test would show up anything, but he didn't really think so.
I certainly hope that there is a accurate way of testing M5 engines to see if there is a HP difference in those engines from what BMW says it should have..+-3%.
This whole thing is almost a never ending bunch of endless loop questions.
There are plenty of top Dyno testers in OZ at the moment that maybe able to help.......I will look into this. I will also try and find the best guy in BMW in OZ to see if he can help.
Dr Jim .....My thoughts are that we need to try and eliminate as many of these variable factors.
1...We need to find a very respected Dyno facility in the city/state that the owner lives in and try and get as many as possible if not at the same time to help reduce the weather factor.
2...Talk to these Dyno shop owners and find out really what could be up with the testing procedures that show these big differences of power.
3....Find out if there is a dyno the seems to be the most reliable in doing consistent tests.....We may have to look into this more?
I had my car ran on a Dyno Jet in Orlando and Nowack use a Dyno Jet as well....but i don't know if there the same model?
I know I've seen other owners trying to get together and do runs......but how did they go...what power runs did they get?.
Ask if there are any other high powered cars out there that don't seem to show much of a difference in power loss or difference that they have tested.
Do you think that in each state or area/country that we live we should really try and accumulate as many "group" runs as possible while the weather is getting better...5 or more cars in each group run would be good.
That may not be too hard as there seems to be plenty of small pockets of owners in most main cities in the US.

Do you think we soul run a poll on what the HP power other owners have got from the rear wheels on their cars?
This should give a bit more of an insight into what we are finding as the normal or what is the variance in power.
As you may have read in the past, Nowack have found a decent percentage of the M5s they pulled apart to have this "blow by" and wouldn't touch the job once they found this problem in the engine. I could think that BMW know whats going on.......i would hope so. This could be a very serious problem for them in the next few years.
Let me know what you think......and lets see if we can get a POWER poll going.
APPLES

Bart Carter · 4th November 2001, 19:49

The easiest way to dyno your car is to run the quarter mile and see if it does 107 in the quarter.

If you run at a high altitude, have excessive heat or humidity, etc., you can calculate the differences.

Apples · 4th November 2001, 20:22

took me that long to knock up my last post of mine that Bart slipped in there........sneaky bugger.
The answer is that you need to pull fuse 17 and 30 to shut off the DSC. Once you do that then it will run to your cars max.
What go me concerned was that i had the Powerchip in my car from Feb last year, and when i had it tested this summer it should have given me something in the realms of NO less than 410hp from the base 394 hp. I wonder if i had kept it stock what it would have run? I had it tested this summer and they got 344 rwhp and 332 torque. This was not real good considering the ECU upgrade. Then i thought i must have not reprogrammed the ECU right.........but i did, because the dyno sheet showed it running till 7,000 rpm a few hundred more the stock
Nowak said that they have seen it as low as 360hp at the engine and in one M5, and a high of 404hp.
Now i compared my run 4 months ago to Nowack and they said it had 350 rwhp. Thats pretty close to my US test as far as I'm concerned.
APPLES

droid42 · 4th November 2001, 21:25

Apples,

The comment about transmission losses staying exactly the same regardless of engine power isn't strictly true.

If you increase the rate at which the transmission spins, you will increase the frictional losses hence the power lost. If you get more power from your engine by making it rev. higher you will definitely increase the transmission losses due to higher frictional losses.

Ian.

Apples · 4th November 2001, 23:27

Ian....i'm not quite sure what you mean....please help me l'm just a bit S-L-O-W...

So lets draw a scenario...two M5s are both driving down a road together at 100mph, one has 400hp and the other 500hp. It may vary the amount of power needed to get each one to 100mph because of air flow and friction , but from the fly wheel on, they both will have to move the same weight as each other, therefore the constant 40hp real wheel loss thats been established because of the fly wheel/drive shaft/diff loss. This is was shown on Nowacks dyno sheet that they sent me. I think that the 40hp loss is found from letting the car off the throttle at the end of the run, and then seeing how long it takes for it to slow down over a certain time then you get that number.
I hope you understand what l'm trying to say....abuse me if you disagree

APPLES

droid42 · 4th November 2001, 23:52

Apples,

One simple thing to remember here ... not a single rolling road in the world can accurately measure transmission losses. The ONLY way to measure flywheel power is to take the engine out and put it on a true engine dynomometer.

Another thing to remember ... measuring transmission losses during overrun is completely and utterly innacurate/pointless. Why? Because the engine is generating absolutely no power during overrun so how would you ever tell whether or not different power caused different losses?

My point about transmission losses increasing with revs is due to the fact that transmission losses are primarily due to frictional losses and (obviously) the faster you spin a set of gears, the more loss due to friction will occur. (You'll never make a fire by rubbing two pieces of wood SLOWLY against each other will you?)

Here's a good link with an essay from someone who really knows what they're talking about and can explain it much better than I can:

Power and Rolling Roads

Ian,