Hey all - after abusing my car most of the day at the Woodward Dream Cruise, I seemed to find that it's difficult to rev the engine at a standstill past 4,000 rpm. Is there a rev limiter at work here?

Reason I ask is, after a few unsuccessful burnout attempts... I was a little more curious.

Traction control was off.

Thanks for any input.

-- Darren

- '05 conv. K+N + #14220

 

Yes there is. Currently not able to completely eliminate the issue. You can pull the TC fuses which will allow you to 5,200 rpm before the engine cuts. This is the only way we can currently get a fairly descent dyno, though still not at the redline.

There are a couple of us working on the problem. It has to do with the speed sensors in the front wheels and elsewhere, which also activate the ABS and other parameters of the many computer systems.

 

The ECU limits the number of revs allowed at a stand still for self preservation and engine longevity.

Neither the C32 guys nor the SLK32 guys have issues dynoing their car. Not sure what the deal is with the crossfire.

 

Its the Crossfire ECU that has some extra 'rationality' checks on the various systems in the car. As well as just looking for open and short circuit sensors it checks to see that the sensor signals are appropriate to the conditions based on the state of other systems in the car. The CAB (Controller Anti-lock Brakes) constantly checks the differential between the front and rear wheel sensors and imposes a 5,000 rpm limit if the fronts are stationary in relation to the rears. Its actually even more complicated than that as it ties in with some of the emission systems too, but that's another story.

The SLK's have a 'dyno' mode that can be set via the multimode dash display (which we don't have) that disables this CAB 'feature' until the ignition is cycled.

 

Yeah< What He Said !!! Lol

 

No they do not. There is no 'dyno mode' and there is no multimode dash display to set in the SLK32. At least not the R170 (which is the model the Crossfire is based on).

 

Well I have read this on the several German MB forums and there is instructions on how to do it, I believe the display is the in the dash cluster like our milometer. Admitted, some references are to the 350 not the R170 but others refer to other 320 powered Mercs:

"Well, Benz lovers, we found a way.

Here's how. To start, turn the ignition key to the first accessory position, making sure the dash display shows the odometer. The SRS airbag light should be on. Press the trip odometer reset button three times rapidly before it goes off. If you do this right, a screen will appear showing a voltmeter. Then press the "up" arrow on the left side of the wheel twice to take you to the "ESP dynamometer test" screen. Using the plus (+) button on the right side of the wheel, select "on." And then start the car. Warnings will appear informing you that the ESP, ABS, and BAS (brake assist) aids are now turned off and you're on your own."

Even the Crossfire will display other information here. By holding the trip reset in combination with the ignition key.

 

No steering wheel controls on the R170 (SLK230, SLK320, SLK32).

What you are referencing is from the R171 & possibly the C32.

There is no dyno mode in the R170.

 

OK, I stand corrected. There are definitely 320's that have been dynoed though.

 

If you have any clues how to figure it out, please let us know... I'm tired of running partial dyno's at 5,000 rpm.

 

The SLK guys have not had any trouble on the Dyno. There are a number of dyno's posted. They have to do nothing special.

Which is the whole reason I have inquired on a number of occasions about the problem dyno'ing the Crossfire and am trying to figure out what the difference is.

 

What we really need is a technical manual for the R170.

 

Your best bet is to get an answer from EvoSport in California, Kleemann in Colorado or Renntech in Florida. They are the only one's I know that have much experience Dyno'ing MB vehicles. Ask to speak with their Dyno tech. Neither place has done a Crossfire to my knowledge.

Let us know what you find out.

 

There are a number of places that have experience dyno'ing MB's. The difference between them and the ones mentioned is that the ones you listed are aftermarket manufacturers.

The MB boy's had a dyno day in Atlanta a year or so ago. They dyno'd:

4 SLK32's
2 SL65's
3 SL55's
A couple of C32's, C55's and CLK55's.

Everyone got 3 full runs. If I remember correctly the SLK32 guys were putting down between 292-300 hp.

 

Ok, so how 'bout putting a call into them and answering the question for all of us...

If you need me to feed you the questions, I will be more than happy to ... WE CALL THIS PROACTIVE AS OPPOSED TO INACTIVE. Or if you like, I'll call them... Give me names and #'s.

 

I don't think we are disputing that MB's can be dyno'ed, we know this is the case. They do predominantly seem to be auto's though - perhaps this has something to do with it. Has anyone tried dynoing an SRT or auto xfire?

 

Have you checked into finding someone with an AWD dyno? That should eliminate the rev limiter issues since it keeps the front wheels spinning at the same road speed. Check here: http://www.mustangdyne.com/locator.htm. Look for the ones that list an AWD model. There is one in Oxnard and a couple in Orange County. I'm sure there are bound to be more AWD dynos in the LA area.

 

My run was done on a 4 wheel dyno, but that just allows for a 4WD vehicle to run all four wheel on the rollers - the 'spare' rollers are not driven like the brake testing rollers. I have now cut in to my ABS loom to fit a widget to feed the front wheel sensor inputs on the CAB. I will be testing this if I get some time this weekend.

 

Perhaps you don't know that AWD dyno's don't have powered front rollers... They are for vehicles that have power to the front and rear wheels which drive the rollers... Woody, do you concur ?

 

I could be wrong, but I thought some of them have the rollers connected with a belt so each sees the same road speed. A lot of AWD cars these days have traction control that can transfer torque from the front to rear when it senses slipping. It seems like these cars would have the same problem as ours if the two rollers were driven independently.