Hello.
I dyno'ed my car for the first time at a dyno meet arrangement in Denmark.

It made 344 crank hp... Its a w209 55 amg and i supposed too have 367 crank hp. The car is bone stock but i good condition, new plugs, oil, etc....

The dyno run was in 4th gear and the car was in dyno mode. Somebody have any idea where my last 23ponnys are? Because i was VERY DISSAPOINTED!!!

It also has 18x11" rims and rear tire size is 255/30 18

Had a race with a 2008 slk55 amg on the german autobahn. I had 250kg load with me and keept up with the slk without any problem.And another time alone with a Corvette c5 400 hp. And was equal.. Sooo is there something wrong withe the dyno perhaps??

greetings from Germany.

 

only way to read crank horse is if the motor is out of the car on an engine stand. so maybe it was 344 rwhp? with 18% power loss your looking at approx 406 crank hp.

 

no way a stock CLK55 is making 406 crank hp or 344whp. Must have been an error on the dyno.

If you are missing horsepower somewhere, try cleaning out your intake filters. if they are dirty, they may be robbing of you some power for sure

 

Mass Air Sensor on its way out ?

 

Tell the dyno shop to give you a print out of the wheel HP... without that print out there is no point to speculating to anything in this thread...

Get the print out and report back as to what kind of dyno it is, etc etc.

 

I have a printout and i will scan it later tonight and post it here as soon as possible.
The air filters is as good as new. just checked..
I actually have no idea of what kind of dyno it is. You can see it on youtube

http://www.youtube.com/watch?v=KhcNP0k_0NU

In the front there was a very small fan aprox 18" diameter and a half meter long. Cant bee seen on the video thoug..... The dyno dude said that the messuring was crank HP. Will post the Dyno sheet later toninght.

He also said that he had to put it into Neutral to messure the horse power???

And the dyno is a HPA..

 

the only way i can see them measuring crank hpwith this style dyno would be if the computer is factoring in the parasitic power loss thru the drivetrain. also just by seeing the video im at a loss as to why he held it at top power for over 30 seconds. no reason for this. peak power is measured and then your done. no need to run at high speed for extended times on a dyno. also the hood should be open to circulate as much air as possible as the car isnt moving.
us this as a learning experience and find a reputable shop with a dyno room and try again

from the sounds of the engine he peaked at 54 seconds mark and held it wide open until approx 1.24 seconds. no reason for this!

 

Hi Max.

344 crank hp isn't too bad!
You're probably down 10 or so hp.
Mine made 371 Crank hp with a cam, exhaust and filters.
I have a W208.
If you do a search for other dynoed cars your in or around that ball park figure.

Our cars have alot of torque and that is where we get our speed from.
Bolt on a few mods and you'll be happier .

 

A w208 clk 55 amg has "only" 354 hp stock while a w209 clk 55 amg should have 367hp stock. And mine is a w209.. So im missing some power..

 

Maybe it was a Maha dyno. I believe they can derive crank horsepower.

Another possibility is they were not using SAE measurement standards.

BTW, I don't think a 18" fan provides nearly enough cooling flow, and high temperatures can rob engine power.

 

I believe MB claims the 209 has 362 hp (SAE).

 

I believe some dynos can calculate crank horsepower by measuring drive train drag during coast down (in neutral).

 

that comes out to 344HP / 375tq , thats right on par with the W208 CLK55s (342/376) ... seems about right although I've never heard of that dyno brand so its tough to say what its drivetrain loss % is. It does appear to be an inertia dyno b/c after 6400rpm redline it does continue slightly in rpm after fuel cutoff which is typical of some inertia drum dynos.

You may be losing some HP simply b/c you need a basic maintenance tuneup, that should give you the full 362HP next time.

 

I can tell you for a fact you left a little on the table because of the wheels. Also did you do the Sneaky ECU Reset before the dyno?

 

How do wheel sizes effect hp on a dyno?

Also what is the correct drive train % ratio lost to use as when I recently dynoed my car the DD dyno worked out the drive train loss.

 

Dyno #'s are so trivial. Good for the ego I guess. Run her in the 1/4 mile and get back to us.

 

The drive train loss is probably somewhere between 10-15%.

Whatever correction factor you use, divide the wheel horsepower by that factor to estimate crank horsepower.

 

Dynojet = 18%
Dyno Dyn. = 22%

 

Why does the type of dyno matter? Isn't the issue the loss of power between the flywheel and the tire contact patch with the road (or with the dyno wheels)?

 

its much more complicated then that, all dynos read differently for different reasons.

The main difference is Loading vs. inertia dyno (there are lots of threads on it, use the search function to study up on the differences).

Hope that helps

 

I realize different dynos can give different power readings for the same car (given essentially equal conditions). But the percentage of power that is lost between the car's flywheel and the tire contact patch is not variable.

 

Yes it does depending if it is a loading dyno or not (please search). I don't want to turn this into a DJ vs. DD thread (there are hundreds of them out there).

 

I believe the majority of drivetrain loss is the result of how fast each drivetrain component is spinning, with the second biggest factor being "rotational mass" (rotational mass would be a constant). The third factor in drivetrain loss is the friction created by the interface of gears, but I don't believe its power drain exceeds that of either rotational loss or the loss of power created by rotational mass.

While there is no question that different dynos will produce different power numbers for the same car, I just don't believe the difference can be explained away soely in terms of "loaded" versus "inertia" measurement methods.

A "dyno specific correction percentage" would in my opinion be a better way to couch the issue, as it would include both drivetrain losses and a dyno specific correction.

 

The bigger the wheel, the more power you use up trying to get them rolling. I gained about 10 rwhp just by changing my wheels from 19's back to my stock 17's.

 

So standard wheel size (17") and a sneaky ecu reset would perhaps do the trick?
In which gear should it be running at the dyno? And "dyno mode" or with the Antispin off? And what includes a basic maintenance tuneup?

Thanx for all the answers