Possible to change rev limiter ?

Gazwould

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C250 CDI .

4,500 rpm is too high as these engines make peak torque early and peak power as early as 3,500 so going to 4,500 is a waste .

Possible to change to lower rpm limiter ?
 

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Change up early if you have a manual, if it's auto it will change up before rev limit so not sure on the problem.

You don't want to cut the limiter to peak torque or power
 

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If you don't like the power curve, have it remapped... but thinking back to my 220 CDI- with the same engine as yours, I can't think when I'd approach the rev limiter even when driving spiritedly.
 

L John

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I'm guessing the OP means he wants the gearbox to change up earlier, not that its hitting the rev limiter.

Going beyond peak torque is absolutely normal, your car will have more horsepower further up the rev range than at peak torque RPM.

The rev changes are set for optimum acceleration by Mercedes designers.
If you're towing and need the torque it will still do fine even when it passes peak torque revs.
 
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Gazwould

Gazwould

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I seem to find it wants to over ride my manual flappy paddle + when on full throttle letting it go to pointless 4.5K rpm.
 

thebiglad

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Hi Gaz, am I right in thinking you actually would like the gearbox to change into the next gear sooner ? If so, when you get to for example 3500 rpm just release the accelerator a small amount for a second and she'll change up.

I'm not familiar with the autobox in your car, but assuming it has multiple 'modes', try switching to 'comfort' and use your pedal to change gear when you want.

If you use the steering wheel paddles you are over-riding the designed-in change points.
 

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I had exactly the same problem with my Audi Allroad. Peak power (judged by the "butt-Dyno") was about 3300RPM, but the 'box wouldn't change till way past 4500.

The gearbox clearly wasn't calibrated (properly) for that engine, but I never did get any answers as to whether it could be changed....
 
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Gazwould

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Cool , not use to auto , I'll try the slight lift off .

The flappy didn't change up early on full throttle , normal driving it does .

Will have to experiment again , you run out of road around here trying !
 

LostKiwi

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Rev limits can be reprogrammed but you'll need a custom remap to do it.
 

alexanderfoti

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Rev limits can be reprogrammed but you'll need a custom remap to do it.

As above, its possible, but will need a remap to do.
 

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Trying to change up when your accelerator is past kick down won’t work, if you use a little throttle control you can easily keep the car in peak torque/BHP, a map will help and do it for you but just refining mark one right foot will also work wonders
 
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Gazwould

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This is it , instead of the lag of a kickdown , rev tits.. change up then progress , I find progress is made part throttle riding the wave of low rpm torque.
 

LostKiwi

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When you press the throttle there is a click at the bottom of the travel which is the kickdown switch. If you press the throttle to just before the click it won't hold gears quite so long.
In terms of reprogramming that will require the transmission ECU to be reprogrammed - I seem to recall a place in Kent can do this.
 

alexanderfoti

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When you press the throttle there is a click at the bottom of the travel which is the kickdown switch. If you press the throttle to just before the click it won't hold gears quite so long.
In terms of reprogramming that will require the transmission ECU to be reprogrammed - I seem to recall a place in Kent can do this.

I find, if you roll onto the throttle, without pressing the kickdown, it doesnt change down as readily.
 

L John

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Isn't that the same as LK was saying?

i.e. Pressing the kickdown is more likely to drop to a lower gear and hold it for longer. Just before the kickdown button will be less likely to change down and will change up a tad sooner.
 

alexanderfoti

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Isn't that the same as LK was saying?

i.e. Pressing the kickdown is more likely to drop to a lower gear and hold it for longer. Just before the kickdown button will be less likely to change down and will change up a tad sooner.

I mean rather than jamming the throttle down quickly vs slowly rolling into it,both without pressing the kickdown switch.
 
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Gazwould

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So it's ECU or TCU controlled , or both ?
 

alexanderfoti

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The rev limit of the engine is ecu controlled.

The changing rpm limit is tcu controlled.
 

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when changing gear you and or the manufacturer have to compromise between the time it takes, what the next ratio is geared to and the expected use of the vehicle

on an auto, holding on a bit long could be because the hardware/software is slow and gear change speed is long (standard in most brands) and when if finally realises what to do, it needs to have good drivability in the next gear ratio...

by the time you are trying this hard a number of other factors matter quite a lot
atmospheric pressure
prevailing wind direction
spec of fuel in the tank
up or down an incline
loading of the vehicle
the ratios in the box
tyre pressures
time from last service
condition and previous use of the vehicle

if you have the family on board with luggage, its 500 mile to the next service, the wife put asda fuel in it and you are going up hill into a headwind trying to get safely back on your side of the road before a big lorry comes, do you really want it changing up at 3000rpm so you die - or rather make good progress and enjoy the trip out with your loved ones?
 
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L John

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… do you really want it changing up at 3000rpm so you die - or rather make good progress and enjoy the trip out with your loved ones?

Exactly that, full pedal is set up for best acceleration.
As I said earlier, more horsepower is further up the rev range than peak torque RPM.
I don't think the OP understands why it's set how it is.
Many people don't understand how torque and horsepower are different animals.
A race hose and a plough horse may have the same power but they use it in different ways.
 

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