Is there any 3 bars mercedes map sensor?
our stock map sensor is 2.5 bar absolute pressure, so when we hit the 1.5 bars boost we get the high pressure code p0108.
i have a v6 3.7L with 55SC, with stock pulleys i was at 1.4-1.5 bars, car was tuned with 550cc and running good, now with 175mm lower, 84 upper and 750cc injectors (waiting for tune) the car hit the 1.5 bars at 2500/3000 rpm and cuts fuel cause i pass the map sensor limit and give p0172 system too rich codes and p0108 high pressure.

 

I think when you get retuned the tuner can up the voltage to the map sensor but as far as a bigger Benz sensor none available

 

Are you sure? I thought the slr runs 22psi stock.

 

it is called re-scaling the map sensor

 

SLR uses the same MAP sensor as the E55 and C32. Latest part number is 0051537228

 

Only problem with re-scaling: Good luck finding anyone that can do it on our platform: and make the car work (drivable)....


I pulled the upper pulley because I could not get a tuner to fix the issue: Over-boost Cut Out

I was going to build a MAP clamp, but finally just said **** it...

 

noooo don't tell me this

 

can we just install bigger map sensor plus bigger injectors and adjusting only the fuel graphs duty cycle?

 

I read on another forum.....
"I also have found a 3 bar MAP for our cars that is plug and play but would need tune scaling. The new 320/350 Diesel has the 3 bar MAP."
Maybe this will help?

 

 

That's a good find. The question remains. Who can program the ECU to see the extra boost and react accordingly?

 

Look up Map Clamp. You can run one so that when the map exceeds the voltage, it will still send the max allowable to the ECU and avoid the code. Split second performance and many others make them. Because our cars are speed density, the car is still tunable this way but you will need to do pulls not only at WOT, but also at slightly lower throttle positions until the clamp is inactive to get it to run perfect. It won't run bad if you choose not to do the part throttle pulls, but it will likely be rich.

 

what are the risks to go with a 3 bar map in place of 2.5 bar one without tuning for map tables, with only tuning for basics fuel, timing...

 

This will require remapping all the tables associated with the map sensor which are most of them. In other words, the risk is big. Talk to your tuner about it and see what they think.

I really think you need to consider a map clamp or a signal calibrator (see link below) since it will only be active when you are above approximately 17.5 psi. That is typically where the ECU hits the limit and shuts the fuel off. In all other cases, your existing tune will be untouched and therefore you can tune as you have initially suggested.

http://www.splitsec.com/products/calibrators2.htm

 

thanks i'll see.
our ecu cut fuel only above 1.5 bar(22-23psi), many times before i went to 1.4 and 1.5 bars, it only gives code high boost, but now when i hit past 1.5 bars it cuts fuel.

 

This makes sense. If both 2.5 bar and the 3 bar sensors operate at 0-5v, then the signal needs to be rescaled or the maps need to be adjusted. Adjusting maps is cleaner but the map clamp is easier.

 

so if we don't rescale the 0-5v map signal(with the bigger map), the ecu read lower boost and the fuel quantity will be lower, then we add necessary fuel by tuning, is there any problem??
ex: if the map voltage at 3v the ecu will see like 1bar but actually the boost is at like 1.5 bars.

 

You are correct. There is no problem, just more work for the tuner. Like I said above, I think this solution is cleaner but will take a bit more time to implement and test.

 

Update: i installed the mb diesel 3 bars map, but it did not work, the engine did not idle. so i''ll go with the map clamp.

 

Did you do anything with the MAP scaling or did you simply throw the new sensor on? Let me guess, It probably cranked, started, and died right?

 

no map scaling and yes cranked started then idle so bad like a failed map sensor.

 

That's exactly what I expected. The reason is because the ecu does not know how to interpret what the larger map is telling it. Once it is rescaled, it will do just fine, but it has to know how to interpret what the sensor is telling it.

 

As an arbitrary example, 0v equals no signal, but everything from 0.1-5v does not equal the same. The ecu is seeing a value above or (most likely) below what it is expecting to see and is interpreting it as a potentially catastrophic situation.

 

yap but like Bramage said no one can rescale it!

 

I call BS and say that no one has taken the time to play with MAP scaling. Half the battle has been accomplished in that a 0-5v sensor does exist that fits. Now we just need to either find a tuner that's willing to play, or get your hands on the software/hardware necessary to edit the values.