BMW M5 Forum and M6 Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
418 Posts
Discussion Starter #1
I just from The Dyno Shop in the San Diego area (that is the actual name of the shop).

They use the Dynojet 248C dynamometer. We did the test in 5th gear (the best results are obtained when testing a car in a gear closest to 1:1. As it happens, the M5's 5th gear is 1.00!).

My M5's driveline is completely stock except for Dinan engine management and a Kelleners export version exhaust (slightly louder than its TUV-approved counterpart).

My first and best run (my two subsequent runs achieved less horsepower due to the "heat sink" effect -- one of these two subsequent runs was also done in the less-than-optimal 4th gear) saw 333.4 BHP @ 6100 rpm, with 325.7 lb/ft of torque in the 3300 - 3500 rpm range.

One of the reasons that I dyno'd my car was that I was extremely incredulous of the low BHP dyno numbers posted to the site last week . However, I did follow the advice on the site and removed fuses 17 and 30, and had no problem seeing 7200 rpm.

As a point of reference, I dyno'd my E55 when I owned it and saw 299-300 BHP.
Thus, according to my calculations, this represents about a 14% power loss from flywheel to rear wheels (Mercedes-Benz quotes 349 BHP for the E55). 14% is extremely efficient for a automatic-tranmissioned vehicle.

I don't believe that my Kelleners exhaust adds BHP or torque to my M5 (if anything it probably takes away a minute amount of power).

Therefore, I was hoping to see at least 338.8 BHP (which represents a 14% power loss from 394 BHP SAE). I believed that the M5's drivetrain with its manual gearbox should be at least as efficient as the automatic-transmissioned E55's. My measured BHP of 333.7 represents a 15.3% loss, while the measured torque of 325.7 lb/ft represents a 12.4% loss (as compared to BMW's stated torque of 368 lb/ft).

Oh well, I guess that I am splitting hairs!

When I am able to, I will post the actual graph and table of power and torque (in steps of 100 rpm).

After seeing the Tri-Flow link on the site last week, maybe they should re-dyno their M5 as their number seemed positively anemic!

Another interesting note: I saw maximum power at 6100 rpm when testing the car in the optimal 5th gear. However, when testing the car in 4th gear (where 8 less BHP was achieved), maximum BHP was achieved @ 6700 rpm (closer to the factory's quoted peak power @ 6600 rpm.

I guess that these rear wheel dynos are not an exact science (i.e. peak power numbers and the rpm where they occur, all differ depending on how much "load" is being pulled). Obviously, ambient conditions all influence (i.e. exterior temperature, humidity, engine room temperature, et al).

Just my $0.02
 

·
Registered
Joined
·
418 Posts
Discussion Starter #2
I made a mistake. Apparently this whole Dyno BHP thread began on The BMW Registry on 30 August 2000 under the topic "Horsepower" (and not on this site).

My apologies.

On that thread, a couple of people mentioned that the rear wheel horsepower ought to be in the 350 BHP range.

Maybe the M5 drivetrain has only a 10% loss from flywheel to rear wheels (wouldn't that be some incredible driveline efficiency?).

I wonder if I shot myself in the foot by installing the Kelleners export version exhaust. Maybe there is a price to be paid (read a decrease in power!) for this incredible exhaust note....
 

·
Registered
Joined
·
135 Posts
There were 3 of us in Houston that had our cars run on the dyno a couple of months ago. They ranged from 330 to 335 hp. These were done on a dynojet 248c also. Saw about the same torque numbers. One thing to keep in mind is that with OBDII you will get HP variations. The ECU is constantly modifying the parameters to optimize emissions. Though I have to say that all 4 of the cars are within a couple of HP of the mean.

As far as driveline losses, I have heard from 12 to 20%. My BMW mechanic says anywhere from 15 to 25%. I think 15% is a good number to use for a street car. It is probably optimistic. I have also been told by Dinan that they do not consider the Dynojet a true dynometer. They say it is an accelerometer because it does not load up the driveline sufficiently. They say a true dyno is like a Powerdyne unit that has dual rollers in the wheels and tha ability to simulate load conditions.

So there is my load of **** on M5 dyno runs.
 

·
Registered
Joined
·
101 Posts
I will be installing a 248 in my shop in January and then will be making many runs with two M5s (mine and a buddy of mines). Will post some averaged figures in Feb, plus some pre and post Tri Flo figures.

BTW I am putting the Tri Flo on only for the sound; I harbor no illusions about HP gains from aftermarket exhausts.

Steve

------------------
'00 M5
'99 R1100S
'66 GT350H/Paxton
'85 911
 

·
Registered
Joined
·
1,856 Posts
The Bosch chassis dyno at Kelleners assumed/calculated/whatever ~13.4% driveline losses.

Volker at Kelleners claims he's never seen a production M5 produce a full 400 (DIN) HP on their dyno, most have been a handful of HP short of that (as was mine at 1600 miles when it was tested there).

When you're talking about a percent or two, you get into issues of fuel quality, weather, temperature, etc. Dyno tests run in CA on pump gas benefit from low altitude, may suffer from high ambient temps and lousy oxygenated gas. The test in Dinslaken had good German super-premium unleaded and cool weather, but it was humid.

And according to Kelleners' tests on their dyno, 6th gear typically shows 13-14HP more than 5th, but you can't run a stock M5 out to redline in 6th due to the speed limiter.
 

·
Registered
Joined
·
106 Posts
I'm in San Diego, too; maybe I'll take my M5 (stock '00) to The Dyno Shop and have it tested on the same equipment. That'll give us a baseline to tell if the Kelleners exhaust is doing anything for you. Of course, variation in engine build quality, break-in of the aluminum engine, gas quality, etc, might cause some variation, too.

I'm very slammed at work right now, but I'll try to get down there in a week or two.
 
1 - 8 of 8 Posts
Top