Power Output.

[Paulopt2248]

Recently the fuel consumption on my C320 CDi has increased by about 15% (at the same speed on the same roads) although performance does not appear to be affected.

I took the car to my local Mercedes dealer who supplied the car, and they confirmed that everything was working correctly, but they did do a remap of the 7g autobox.

However despite that the fuel consumption still seems to be far heavier than it has been for the previous 20,000mls (there are 22,000mls on the clock now). I had the car put on a dyno last week, and both the power and torque outputs were lower than the figures given by Mercedes....214bhp actual against a quoted 224bhp and 359lb/ft against a quoted figure of 376lb/ft.

The MAF and ERG are working correctly with no fault codes indicated. Has any member got any idea why the fuel consumption should fall so much with no apparant loss of performance.

Regards Paul
C320 CDi W203

 

[television]

The colder weather can dynamically reduce the fuel consumption, My SL 500 drops off a long way in the winter

 

[Alex M Grieve]

The colder weather can dynamically reduce the fuel consumption, My SL 500 drops off a long way in the winter

I endorse Malcolm's point here. If you watch the instantaneous consumption on the dashboard computer, especially in the first few miles until the engine is fully warm, the consumption suffers terribly in cold weather. I always thought diesels were immune to this (and are probably less affected than petrol cars) but it does happen and is quite significant, especially on shorter journeys if the engine is cold.

 

[Paulopt2248]

Hi,

Alex and Malcolm thank you both for your replies. However, the fuel consumption has not actually been heavier in the colder weather over the past 20,000mls. In fact it has been somewhat enhanced once the vehicle is warm. Colder air actually is more dense and with a turbocharged diesel it can actually ehances performance.

Do Mercdes like others have a tolerance margin of say 10% on their quoted power outputs, as I mentioned my vehicle has 10bhp and 17lb/ft less than quoted by Mercedes. And Mercedes tell me that they are usually 'right on the money'.

Perhaps it's something as simple as the air cleaner. I am awaiting a call from the top mechanic at my local dealership to discuss this.

Regards Paul

 

[dragon]

Because the auto choke is on until the car warmed up.

It nice to have the old fashion pull cable coke to enable/disable the choke. The last time I see it in a mark II Escort.

 

[television]

Because the auto choke is on until the car warmed up.

It nice to have the old fashion pull cable coke to enable/disable the choke. The last time I see it in a mark II Escort.

We have not used chokes in the past 25 years

 

[GCLTuning]

Recently the fuel consumption on my C320 CDi has increased by about 15% (at the same speed on the same roads) although performance does not appear to be affected.

I took the car to my local Mercedes dealer who supplied the car, and they confirmed that everything was working correctly, but they did do a remap of the 7g autobox.

However despite that the fuel consumption still seems to be far heavier than it has been for the previous 20,000mls (there are 22,000mls on the clock now). I had the car put on a dyno last week, and both the power and torque outputs were lower than the figures given by Mercedes....214bhp actual against a quoted 224bhp and 359lb/ft against a quoted figure of 376lb/ft.

The MAF and ERG are working correctly with no fault codes indicated. Has any member got any idea why the fuel consumption should fall so much with no apparant loss of performance.

Regards Paul
C320 CDi W203

This would not have been a REMAP. This will just be an Update to the COMM settings .

Its very common to have a smaller output than the manufactures quote there never right !! . We dyno'd a new Audi RS4 (58 reg) straight from the show room had 26 miles on the clock and was running 35 bhp under power. so we mapped its and got 13BHP over the quoted output. This should have had a total gain of 50 bhp over the manufactures output.


Kind Regards GCL Tuning

 

[Paulopt2248]

Maf?

Dear GL Tuning thanks for your post and information on power output.

I think I am going to insist that Mercedes change/try a new MAF sensor on the car as the power output being down is one thing.....but the loss of 15% fuel consumption at the same speeds on the same roads over 80 miles or so (journey done 8x) , is quite another.

From what I understand is that MAF sensors tend to go over a period of time and that things get worse gradually. So if the MAF were going down on my car it might not show up as a fault code.

Regards, Paul

 

[Paulopt2248]

Sorry my mistake... GCL tuning.

 

[rf065]

I was talking to someone who remaps ECU's, and on the dyno, EVERY mercedes they have dynoed, has produced more power than Mercedes claim for that model before any remaps. So they reckon MB are quite conservative about their power output figures.

Russ

 

[dragon]

It also depends how fast you have been driving, over 70mph it bound to get lower mpg. I drive at 55-60mph, I am getting 35+mpg. I am in no hurry nowsaday.

 

[Paulopt2248]

Power Output

Russ ...

Thanks for your post, while I accept that other makes might over estimate their power outputs... I was told that Mercedes are either 'right on the money' or their power outputs are in excess of what are claimed as you stated. So yes, Mercedes do seem to be conservative about their claimed power outputs.

My C320 CDi is actually 10bhp and 29lb/ft less than the Mercedes quoted power output for the vehicle, and fuel consumption has now increased by about 15%.

After some investigation my local Mercedes dealer has agreed to fit a new MAF sensor to see if that cures the problem. We shall see!.

Regards Paul

 

[GCLTuning]

We have never seen a car that's been spot on with figures there are many factors that play a part such as :
- fuel quality
- driving style/habits
- temperature (If dyno'd in controlled cell this can be adjusted)
- general wear and tear on older vehicle's
- servicing Ie oil,filters,plug's ECT
- tyres
- data logging of previous data (will have an effect if has an active re learn system)


All of these items will in some way effect performance.

Also the accuracy of the dyno (should be calibrated once a week)

Kind Regards GCL Tuning