Bought a C250CDi and it feels slow

[NISFAN]

So true. I come to the conclusion that Sport mode keeps the engine in the max power band with insufficient consideration to torque. I believe on the upshift that it is about 400 rpm too high - you can modify the settings in the 7G/7G+ to change these points (there's another post somewhere here that discusses this). I wonder more people have not done this because I reckon it would a make a more (+ve) difference to the feel of the car than an engine remap.

You prefer 'feel faster' to actually 'going faster'?

I would hope MB set up Sport mode to go faster.

 

[wilsodg]

I would hope MB set up Sport mode to go faster.

I hoped so too, but with max torque at something under 3k rpm ( and decreasing after), and max power at 3400 rpm why does sport hang on in there till 4k? If you upshift at 3500 it drops you right back into the sweet spot and you keep accelerating (hard).

I accept the point about feeling faster versus actually being faster but by upshifting earlier you do seem to maintain the surge, and I figure being pushed back in your seat is an indicator that you are accelerating harder than not being pushed back in your seat.

 

[NISFAN]

I hoped so too, but with max torque at something under 3k rpm ( and decreasing after), and max power at 3400 rpm why does sport hang on in there till 4k? If you upshift at 3500 it drops you right back into the sweet spot and you keep accelerating (hard).

I accept the point about feeling faster versus actually being faster but by upshifting earlier you do seem to maintain the surge, and I figure being pushed back in your seat is an indicator that you are accelerating harder than not being pushed back in your seat.

Good point, ideally the shift point would be matched (different) for each gear. Going from 1st to 2nd for instance the revs will drop more than going from 6th to 7th. Therefore the gear change point should be higher in the early gears, settling to near peak power for the the later gears.

The pushed in seat sensation can be deceptive, it doesn't necessarily indicate the fastest acceleration.

 

[V12]

The pushed in seat sensation can be deceptive, it doesn't necessarily indicate the fastest acceleration.

Yep, my work colleague can push me into my seat temporarily by his lumpy gear changes...

Sent from my GT-I9300 using MBClub UK

 

[Steve C250]

Aye this is a great forum

Which M3 did you have? S65 engine? Manual or DSG?

e92 manual with upgraded steering wheel that allowed for lap timing, G force meter, gear change timer etc..

Loved it, an before that I had the e46 SMGII convertible, an before that the Porsche 911 996 facelift an so it goes on lol

Now a heavy oil convert, so looking forward to giving my new car a little more umpth for when I wanna play lol

 

[Steve C250]

Steve You shouldn't have sold your Porshe

Never sentimental over cars, change them to often lol

 

[Steve C250]

Years ago I had a lowly 325i from work for a couple of months and then had to go back to my lowly diesel rep-mobile and it took me ages to get used to it again so I can't imagine what it must be like to move down from an M3!

On the MB front, I had an E Class when my C270CDi was last in for service. I was sure the paperwork said it was an E250CDi and I thought it went reasonably well. I was gobsmacked when I opened the bonnet at home to have a gander and saw it was a V6 350CDi, I wouldn't have believed that from driving it.

The initial convert has been testing, and believe it or not, but the merc is a harder ride than what my M3 was!!! So am also gettingnused to the new back ache after a long journey, but reckon the 18" wheels combined with the AMG suspension is just a little too hard for my liking, that said, it does hold well on smooth cornering, but bounces quiet a lot is I've noticed.

So the C250 Sport AMG is no sports car, more a modded C class made to feel sporty. Whereas the previous cars I've owned which are pure breed where both solid on the cornering and yet comfortable to go on long haul with too.

That said, I still love the look of this car, and have now bought a cover for my seat which is taking the sting out of the harsh ride, so it's all slowly coming together, and I will alsonadd this, ingot as many looks in this car as I ever did my M3's, so still enjoying that, and once I put my private plate on it to take the year off the car, it should look the dogs nuts.

 

[Steve C250]

Good point, ideally the shift point would be matched (different) for each gear. Going from 1st to 2nd for instance the revs will drop more than going from 6th to 7th. Therefore the gear change point should be higher in the early gears, settling to near peak power for the the later gears.

The pushed in seat sensation can be deceptive, it doesn't necessarily indicate the fastest acceleration.

I've now completed just under 600 miles since I picked it up this time last week, and I've tried everything to see where the sweet spotsnare to get the oil burner rolling a little more spritely.

The manual shift is the best waynto get the car moving, and once it is, it doesn't take too long to hit high speeds.

Gear changes using the paddlemshift gearbox has shown that in 1st 2nd an 3rd if I change up around 4k rpm and in 4th at 3kish the the drive is constant and consistent in how the car pulls straight through with little drop off of torgue.

It's early days yet, and although I haven't bought this car as a replacement performance car, as that would of been pointless, it is nice nether the less to see how these heavy oils perform.

My summery of the 250 thus far is if driven careful, a combined journey will return 52mpg ave, and urban will produce around 37mpg, so not as good as I'd thought it was going to be, but compared to my previous fuel bills, it's massively improving what's left in my wallet!

Was surpassed at the £86 fill up, that's a big tank at £1.40 per litre to fill, but one fill up has 'just' covered the miles I've done this week.

One thing is for sure though, use the right footy heavily, and this car drinks fuel!! Very surprised at just how massive a drop the car dives in economy if driven hard. So hence to say I won't be doing that too often until I get a remap done to improve how this car operates.

One things for sure, this thread has turned into a really interesting topic and discussion, and I really appreciate the feed back and input your all making.

Right, off to bed,

Steve

 

[NISFAN]

Got to ask Steve, did you have a go in a C350CDI?

In my opinion the V6 diesel is the best engine in the range, reasonably economical, and pretty quick. It also has more potential to be tuned than the 250 (which is already like a stage 1 tuned 220CDI). Sounds to me like the performance/economy balance of the 350CDI would perhaps have been more up your street?

 

[paul73mt]

I'll swap you

 

[Steve C250]

Hi guys, long time since I've had chance to come on and reply.

Well, I kept the car, had it remaped so feels more like I was hoping for, and on a run I am achieving 58mpg virtually every time, although I did take a picture of the dash where after a 178 mile trip i avergaed just over 59mpg which let's face it is where we'd all like to be.

Thus far I've covered approx 3.5k miles since buying the car, and according to the computer I am averaging 47.3mpg combined over those miles.

The remap only cost £210 and took 35mins for the company to complete. The difference is very telling, especially in manual mode, really does take off, and having got used to the 250 asnit was, which meant the M3 was out of my system, the car now feels brisk whilst return excellent fuel economy.

I've also had a Carlson upgrade done to the spot lights, and now have a new c204 unit fitted made by Carlson which includes HD LED running lights combined with the spot lights too. Looks great, will post pictures soon.

So yes, I'm a lot happier now, still think the ride is a little harsh, but I've even got used to that now.

Hope everyone is good, and I'll keep posting when ever I get time.

Cheers

Steve

 

[st4]

What's the power and torque figures now. It must have a very high specific power and torque now

 

[Dieselman]

had it remaped so feels more like I was hoping for, and on a run I am achieving 58mpg virtually every time, although I did take a picture of the dash where after a 178 mile trip i avergaed just over 59mpg which let's face it is where we'd all like to be.

If it was true...which it isn't.

Take 30% off that.

 

[st4]

If it was true...which it isn't.

Take 30% off that.

Which still IMHO isn't bad for a car offering well over 200bhp and probably nearly 400ft/lb peak torque.

 

[Dieselman]

Which still IMHO isn't bad for a car offering well over 200bhp and probably nearly 400ft/lb peak torque.

True, but not all the torque is being used all the time, which is why it gives nearly as good mpg as it did when standard.

I would be interested in the torque and EGT figures.

 

[st4]

True, but not all the torque is being used all the time, which is why it gives nearly as good mpg as it did when standard.

No, and neither is the power.

A common criticsm of the 250cdi is its quite laggy and has a short power band, I'd be curious to see if the remapping adjusts boost pressures and the points where the turbos start to come on.

i.e. what the power curve looks like before and after.

Normally with a map, you may expect to see higher peak figures higher up the rev range, at the expense of drivability, but not always.

I would be interested in the torque and EGT figures.

You think the EGT is going to be sky high?

Given the 250cdi is already in a high tune, I'd be really interested in knowing how they got on with this, and whether the map alters the injection, causing premature wear, overfueling and a big bill for four new ones.

 

[Dieselman]

You think the EGT is going to be sky high?

Yes.
I would expect the standard engine to be about 800c, so dump in 30% more fuel and what do you think will happen?

Pretty useful for cooking a fish supper on the way home from work though.

 

[BigSilverEstate]

If it was true...which it isn't.

Take 30% off that.

Hi, whilst I had read this before I think it is very interesting as many people have remaps done because of the gains in fuel efficiency and then presumably place some reliance in the obc readings to gauge the improvements. What is the mechanism that causes such dramatic over reading in a remapped car and what is the basis for the 30% figure?

 

[Dieselman]

Hi, whilst I had read this before I think it is very interesting as many people have remaps done because of the gains in fuel efficiency and then presumably place some reliance in the obc readings to gauge the improvements. What is the mechanism that causes such dramatic over reading in a remapped car and what is the basis for the 30% figure?

I made an assumption on 30% increased torque, which is often quoted.

To develop more torque the engine needs more fuel, but because the remap has knackered the ECU ability to work out the actual volume injected (because it uses a calculated amount per length of pulse-width), the ECU sees 30% less fuel being injected for the same output, but in reality the same amount of fuel is being injected on cruise and more on acceleration.

People love to be conned, makes them feel warm and fuzzy...

 

[wemorgan]

I've no axe to grind on either side of the debate, but I am a MPG nerd. I calculate the fuel used on all my cars, one of which is remapped. After the remap I noticed only a very small change in mpg. I have no OBD on that car, so I can't comment on the error of that. This small mpg change is dwarfed by the changes due to driving style and even ambient air temperature.

For me the remap offers occasional short moments where I can accelerate quicker than before. But mostly it makes no difference to how I drive and therefore economy.