rolling road outcome figures

[arkamelis]

hi all
had my 2001 w210 e320 cdi, put on a rolling road today, unfortunatly there was a issue with the gear changing at some point so the guy couldnt give a reading at a certain range. please took a look and give me your opinion.

 

[arkamelis]

anyone that understands it please let me know, is it good or bad. the man said its giving out about 200 bhp

 

[corned]

That doesn't look too far off the mark to me.

If you have a peak of 155 bhp at the wheels, then I think you're doing alright. What is the flywheel reading from the manufacturer's spec for that age of 320CDI motor - 195-ish?

The torque figure looks a little down on manufacturer's spec, but then again I don't know how torque translates through to the driving wheels.

It's a pity there are no values below 2500rpm as this would presumably have shown higher torque figures. Usually diesels show peak torque somewhere between 1500 - 2500 rpm - just the bit you are missing from the graph!

Personally I would have stayed there and figured out why the lower results did not show up. The gearchange issue?

Unfortunately you only have half the story!

 

[Stratman]

......... I don't know how torque translates through to the driving wheels...........

Power = Torque x Revs

 

[maddog]

Pretty much useless imo even worse than mine i love how the figure is just written in

If there was an issue with gear changing then i presume its an auto , 45hp losses from the wheels to the flywheel on an auto is laughable more like 60-80 i'd say but rundown losses arent easy to calculate with an auto

Put it on a decent dyno with someone who knows what they are doing if you really want to know

Compare that to a chart from a dyno dynamics dyno

 

[Uberwagon]

As an example, when a 500E producing 326hp is put on the dyno the usual wheel figures are 260hp +, so the HP figure seems reasonable.

As for the torque, that seems rather low but the graph doesn't seem to make much sense.

Dave!

 

[arkamelis]

so ive paid £ 50 for nothink ? the guy said he will put it back on once i have had the remap done, so i can compair the results of remap, but from what you guys are saying, i dont have the right information to begin with. the garage did look abit dated. he said the problem was he was trying to get the car up to a certain revs, but it kept changing gear, so he couldnt get a proper reading at this certain point. How much is the rolling road at dyno dynamics. can anythink be worked out from the print out of mine, and should i go back to him once iv had the remap done

 

[corned]

I think the root of the problem is that either you or the garage (or both!) don't understand the requirements of the car on a dynomometer.

There are issues with the electronic stability control devices, and other systems no doubt. This is why there is a dyno setting on the cluster to allow the dyno to record proper figures.

What you needed to do (and the garage should have known this if they know what they are doing) is to set dyno mode in the cluster prior to putting the car through this test.

I bet the results would have been different. I.e. a full set of figures in the results. Maybe that's why the torque figures look to be down?

Or did they set the dyno mode beforehand?

 

[Bobby Dazzler]

so ive paid £ 50 for nothink ?

Probably.

As Corned suggests, without using dyno mode then it would be almost impossible to dyno the car. A car with an auto box even in dyno mode is difficult enough because it tries to kick down.

If you really want to put your car on a rolling road it might be a good idea to join a bigger event run by a car club at a well regarded outfit. That way it's usually a touch cheaper and you have something to compare your graph to.

I put my C-Class on a dyno once, and mine was 296 bhp at the wheels.

Here's the graph I was given:

And here's the car on the chassis dyno:

The organiser of the event (not rolling road operator) uses the following to approximate flywheel power for RWD cars: add 10 bhp to the wheel figure and divide the result by 0.88 - which at 296 rwhp works out at 348 bhp at the crank. Pretty blooming close to the published figure of 349 bhp.

In the past I have used 18% transmission loss as a rule of thumb for manuals, and I would expect a little more on an auto, maybe 20% - this works out between 361 and 370 bhp at the crank.

Taking this range of estimated crank figures into account I think 296 rwhp is probably about right for my car.

 

[Bobby Dazzler]

PS It looks like the rolling road has just taken measurements every 500rpm and plotted a crude graph in Excel. If you look at the other examples posted in this thread, the measures are taken at much smaller intervals giving a better view of the curve.

 

[arkamelis]

carnt find the secret menu

 

[corned]

Sorry - my bad. I had forgotten that yours is a 210 not a 211. (Just read your thread in Electronics.)

But the dyno advice still stands - you need to ensure the car is set up to work on the dyno. If pulling the ESP fuse is the way to do it, then that's fine.