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250 CDI Performance enhancement

20K views 33 replies 15 participants last post by  Bogrole16 
#1 ·
Looking at increasing the performance of my 250CDI.


From all the info on here it looks like the best options are:


Racechips Pro 2 - £199 on ebay
Upgrade - 47HP and 89nm torque
1 year engine warranty
https://www.racechip.com/shop/merce...kw-500nm.html?product=chip_pro2&is_selected=1


DTUK CRD2+ MultiChannel Diesel Tuning Box - £349 on ebay
Upgrade - 36PS and 85nm torque
3 Year "New for Old" System Warranty
DTUK® CRD2+ MultiChannel Diesel Tuning Box Mercedes SLK-Class SLK 250 CDI BE | eBay


What are people experiences? What is best? Pro's and Con's of each option?


Many thanks
 
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#2 ·
I have the same model as you and looked into maybe getting a bit more power.

Celtic tuning say they can re-map our model up to 255bhp and the torque up from 369lb/ft up to 410lb/ft. :grin:

The cost for this is £360, not cheap but the gains are pretty good if they achieve the claimed figures.
 
#14 ·
I have the same model as you and looked into maybe getting a bit more power.

Celtic tuning say they can re-map our model up to 255bhp and the torque up from 369lb/ft up to 410lb/ft. :grin:

The cost for this is £360, not cheap but the gains are pretty good if they achieve the claimed figures.



I had my 250CDI remapped by Eco Vehicle tuning in Hayling Island which are a Celtic Tuning dealer. I mention this as not only did the company drive all the way to Eastbourne (I live near Hayling Island but am working away over there) but also took the time to explain the process, what was changed and what I should expect.
As stated in the thread above, they quote 255bhp, without putting it on a rolling road it is impossible to validate this claim. However, my initial impressions are as follows:

1) ECO setting now feels the same as the Sport setting pre mapping.
2) The improvement in Sport setting is now similar to the difference between Eco and Sport on a standard car.
3) The car is more responsive off the throttle in both settings.
4) The engine seems to rev faster through the range. This might not be factual, but seems a seat of the pants feeling.
5) There is a clearer push in the back from the torque when you floor it and a surge in acceleration following each gear change.
6) It seems much faster initially off the line. This was something I also felt disappointed with the CDI as it feels like its trying to overcome a lot of weight, only just into its stride above 40mph.
7) Initial MPG seems to be 1-2mpg worse around town but similar on longer runs.
8) The whole car feels more exciting to drive, which ultimately is what I was looking for in a re-map rather than a "set" BHP improvement.

Therefore, I would recommend Celtic Tuning as a re-map and would definitely recommend Eco Vehicle Tuning as the customer service was brilliant.

Hope this helps.
 
#27 ·
A proper remap is best.

ECU Remapping Essex, London Engine Remapping Services

If you must have a cheap tuning box then DTUK are the best. If you want a proper tuning box then it has to be the Brabus D4 at £1400 fitted. Ouch!
Hi wja96 !

I have just looked on the Brabus website and cannot find anything for the 250cdi SLK only petrol variants with their tuning boxes have the discontinued this?
 
#4 ·
Why are you bothering with such small increases - all of which are 'claimed', with the small print saying 'up to'. Like broadband, the reality is a lot less.

If you are intent on 'more power', why? What do you want to do with it? Why do you not just maximise on what you already have?

The CDi is an embarrassment to Mercedes. They have to throttle it back so as not to have diesel show up the 350 and 55. Your engine has over 390ft/lbs torque! That is up there with the 55! So as to hold it back, Mercedes have to use a 2.4 final drive - and even this gives a point or two over 6 seconds 0-62mph! The upside of such a low final drive is that cruising at motorway speeds is a tad under 2000RPM.

So all that torque has been crushed. Fit a 3.0 final drive a la the 250 and 350, and acceleration will drop to about 5 seconds with a trade off of top speed down to 138 mph from 150, and cruising at 33mph per 1000RPM down from 41/1000 - ie motorway cruising at about 2500RPM. As the SLK is only a two seater, the possible max weight should not pose too much of a problem with the available HP to hold these figures.

If you were to put a higher final drive into the existing carrier housing, it would be pretty hard for the mod to be detected...
 
#19 ·
#6 ·
My son has has a Bluespark Automotive box on his BMW 435D and its made a huge difference. Either more go or better economy - you choose.
They also do a 30 day trial so if you don't think it works you can return for a full refund. Whichever box you choose, its best to get one that has two channels and so controls fuel and air. Cheap boxes just pump more diesel into the engine resulting in clouds of black smoke from the exhaust and problems with the egr.
Russ
 
#7 ·
The Bluespark box has a horrible reputation on Briskoda for poor customer service and for blowing up Fabia 2 vRS Twincharger engines. Now, it could be argued that that particular engine is made of chocolate anyway (something like 35% have been replaced under warranty for excessive oil consumption) but Bluespark just flat out refuse to accept any liability and continue to sell a tuning box they have to know is dodgy in that application.

Your point about the number of channels is valid, the single channel boxes match only the mass air flow sensor, so they add more fuel as the ECU calls for more air. The adjustable ones simply let you adjust the amount of extra fuel being added. That's linear with air requirement and when the amount of fuel exceeds the amount of air required, it generates soot in the exhaust. These particles of unburnt diesel are removed in modern cars by the diesel particulate filter. When the soot is excessive, it clogs the diesel particulate filter and the car stops.

Two channel systems also monitor boost from the turbo so they can effectively force more air AND fuel into the cylinders so they don't tend to suffer from the DPF clogging issue however on a twin turbo engine, like the SLK CDi250 they don't know which turbo is in use so they are either set to pull hard on the primary turbo and under-boost the secondary or they are underboosting the primary turbo and come in like a sledgehammer when the secondary boosts up. Neither is very satisfactory because one tails off and the other feels like epic turbo lag.

So, now there are three channel systems which monitor the MAF, the turbo boost sensor and the camshaft sensor, so it now also knows the engine revs. When it knows the engine revs, you essentially can map the air and boost to match the original responses of the car. So when the revs are low, you add less air and fuel because the turbo is smaller, as the revs and boost rises, you can add the correct amount for the bigger turbo.

This is what a proper remap does, and because it's written to the ECU directly it doesn't need the box. Three channel systems are MUCH better than two channel systems. Only DTUK has a three channel system. DTUK are resellers for the German manufacturer, DTE, so all the DTUK tuning boxes are TUeV approved and have rolling road printouts to verify their minimum increase claims.

By far the best add-on box is the D4 from Brabus which is a true second ECU that sits on the CANBus and reads all the signals from the car and ECU. This is one reason it is so expensive. It's sufficiently clever that it knows when you are in ECO mode and just gives you the extra 100Nm torque but if you turn off ECO you get an extra 35PS as well. It can only do that because it's reading the CANBus. If you can afford it, Brabus is the box to buy.

I do apologise for the epic length of this post, but sometimes you just need to explain stuff!
 
#8 ·
@wja96: Thank you for taking the trouble to to explain the differences between the options and offer a bit of insight into their merits and drawbacks. Good info like that isn't easy to come by especially as manufacturers are only really interested in pushing the benefits if their own products and the downsides of their competitors.

Ultimately the decision lies with the individual, but it's always best to be able to make an informed decision :smile:
 
#10 ·
Guys, thank you so much for all the insight, it's really helpful.

Unfortunately my budget doesn't stretch to a Brabus box at the mo.

It sounds like the best alternative is a remap. Anyone know who the best company is for this please?

If I was to go for a more affordable box, it's sounds like DTUK are the best option. Is there anyone who is running one of these on here?

Thanks
 
#11 ·
It sounds like the best alternative is a remap. Anyone know who the best company is for this please?
GAD Tuning (as linked above) are known and generally positively discussed on various UK Mercedes forums. Someone had a C-class that was taken from 204PS to 285PS and 650Nm torque. GAD are not advertising that on their website so it might not have lasted too long....

Personally, I like Shark Performance but I've not tried them for Mercedes remaps. Plus they're in Mansfield which is quite a long way from you.

Celtic tuning (mentioned/linked above) also have a good reputation and then you have the well-known super-brands like Superchips Bluefin although they don't seem to have a 204PS OM651 engine configuration.
 
#15 ·
I have also just had Celtic do a remap. The initial impression is much the same as above.
I hardly ever use the car in sport mode as I like the big push of torque you get in Eco mode.The biggest change for me is the low to mid rev range, it gives a real rush of acceleration similar to driving a big V8.
Rained all day yesterday so I couldn't use full power until I was in 2/3rd but a big improvement.
In summary it has lots more go at lower revs with little need to rev above 3000 rpm.
Economy on my 100 mile trip was 2-3 mpg lower. I was using the power a bit more than usual.
I used SJ Concepts in Newport. They have an offer on for November at £295.00
Will report more once I have put a few more miles on.
Thanks.
 
#16 ·
Unless I've misunderstood the posts above it's very interesting that you notice a difference in the E and S gearbox modes as my understanding is that you get the full 204PS only when you turn off the stop/start. So that might be a further pleasant surprise for you! The S gearbox mode just changes the shift-point of the transmission and changes the throttle response which is why the car feels so jerky in S mode.

On the Brabus box you get the full 600Nm torque but only 204PS in ECO mode (Stop/Start on) but you have to turn Stop/Start off to get the 240PS as well as the high torque. The Brabus box is very interesting as it's a proper supplementary ECU (it plugs in in series with the original engine controller and it reads all the values from the car's sensors in the same way the car gets the information originally so it knows when the ECO switch is turned on and off.

Is the Celtic remap done over the OBD port?
 
#17 ·
I have asked Celtic and it makes no difference to the power output if you are in Eco or sport. The output is not variable.
Was done via OBD port as far as I know.
'
Update after one week. makes no difference to MPG unless you use the extra performance.Mid range power is addictive. I'm pleased with the results.
 
#18 ·
Have you checked your fuel economy top-up to top-up or by the DIS?

The only way to get more power on a diesel is to add more fuel. The easiest way to add more fuel is to increase the fuel rail pressure but that only gets you so far so then you have to increase the duration of each injector cycle. The car MPG display works by counting injector impulses and because Celtic won't have told it they are adding more fuel at each injector pulse the car won't show the extra fuel usage on the DIS. So the only way to know the true MPG is to calculate it the old fashioned way.

I'm quite interested in Celtic saying the ECO button no longer has any impact as it implies they are not using the original engine mapping modes as intended but have turned up everything. Watch your oil level and listen out for the fans running hard after a drive (dropping oil levels and hot running are possible indications of. extra DPF regenerations).
 
#21 ·
I am, but as that involves stripping both apart and getting the micrometer out to check bearing and shaft sizes I'm going to pass! I was up for a 4 hour swap out and don't want to do a complete tear down of two final drives only to find the crownwheel and pinion are not interchangeable.

My plan was to remove the rear cover of the cdi diff and fit it to the 250 one. This would be required as the cdi diff has a wider rear mount (more than likely for preventing torque reaction) This was not possible as the original diff while looking the same with 8 torxs at the rear was actually far larger and therefore not interchangeable. With this in mind it is also unlikely that the pinion shaft is the same diameter/length as the smaller diff too.

The smaller diff housing can be "made to fit" but that would involve pressing a new rear l/h mount into the rear subframe. The mounting hole is there for it, so as you say, the subframe can be used for different models.
 
#22 ·
Are you sure the new diff is for your year SLK but just for a different engine? Post the part number on the new diff and I will see what the parts catalog tells us.

EDIT: I see now that you did post the part number of the new diff. From what I find in the EPC that diff is used in the lower powered SLK 200 (chassis 172.448) and not in the 250 gas. The diff used in the gas 250 with the 3.07 ratio is 203 350 71 14.

Both your car and the 200 show two rear sub frames were used. One of those two sub frames is the same between the two cars. It would be interesting to see which sub frame you have. Post your VIN and I should be able to confirm which sub frame you have. Note - the 250 uses the same two sub frames as the 200.

In any event it looks like the new diff is not robust enough for the torque of the engine.
According to this;

Mercedes-Benz Teilekatalog (Ersatzteile online)

A2033507514 is the correct part number for a 250 petrol and that is why I used this number. Maybe the list is wrong, but either way it has been tried and not worked out.
Regarding the robustness of the housing, I was thinking as the ratio was being increased the load on the pinion/crownwheel would be getting reduced so perhaps that is why the diff casing is not as robust as the 2.47:1 item.
Anyhoo. I'm not upset as it was only £57 so I'll leave it in my college workshop so my students can have a go at disassembling and reassembling as part of the course I teach.
 
#24 ·
The new one is a 3-channel system so it should be fine. Do be aware that most CDi250s make more than 204PS on a rolling road. My own one makes 225PS standard and 250PS remapped. It's one reason the chip tuners claims are made against manufacturers claimed figures.

DTE, who make the tuning boxes sold by DTUK in the UK, have all their claims verified by TÜV Austria and they claim 36PS power increase and +85Nm torque.

https://www.chiptuning.com/en/merce...172-403-204ps-150kw-2143ccm/powercontrol.html
 
#26 ·
I've had Celtic remap two cars for me, an Audi A4 S line tdi170 to about 215 ish bhp. Also a golf GTD170 to 227 ish bhp, the golf was a gtd mk6 with dsg gearbox.
Really transformed both cars, but very differently, possibly due to the golf being newer and dsg.
The Audi gained 8-10mpg and pulled from tick over all the way to the red line, fantastic transformation and made the car what it should have been from the factory.
The golf, well in drive (not sport) you pull out to pass a lorry at 50 mph, your doing between 80-90 by the time you pass the cab of the lorry and that's without using kickdown. In sport you can kiss goodbye to the front tyres in under 5000 miles, even with the trick diff it spins way to easy, and both wheels lite up and the traction control can't cope. But it'll embarrass most things 2wd from the lights..
Not sure I want to get my 2013 250cdi mapped, kind of like it as is at the moment....
 
#29 ·
Looking at increasing the performance of my 250CDI.


From all the info on here it looks like the best options are:


Racechips Pro 2 - £199 on ebay
Upgrade - 47HP and 89nm torque
1 year engine warranty
https://www.racechip.com/shop/merce...kw-500nm.html?product=chip_pro2&is_selected=1


DTUK CRD2+ MultiChannel Diesel Tuning Box - £349 on ebay
Upgrade - 36PS and 85nm torque
3 Year "New for Old" System Warranty
DTUK® CRD2+ MultiChannel Diesel Tuning Box Mercedes SLK-Class SLK 250 CDI BE | eBay


What are people experiences? What is best? Pro's and Con's of each option?


Many thanks
Well I am not experienced and I have been contacting and looking for information the reply I had from racechip tuning today is that it is a one channel connection so I will be avoiding that big time !

Secondly if check anothee MB forum the DTUK has been giving a lot owners limp mode after installation.

Also I spoke to a company that installs the Brabus D4 box and it is not intended for SLK so I am not taking that risk either.

I am personally going to look into a remap for my car if I go ahead
 
#32 ·
Brabus only officially supplies the D4 box through Mercedes in Harrogate (their official UK distributor) or directly from their head office in Bottrop. All UK Mercedes dealers can supply Brabus parts through Mercedes Harrogate but they generally just send you to Harrogate directly because they make no money on Brabus and handling the warranty paperwork is hideous apparently. Any other company is supplying a "grey" unit (probably from Eastern Europe) assuming its even genuine and they can't make it work with the SLK because the tuning box is a secondary ECU and it's basically coded for the specific model of car. Contact Brabus if you want an SLK one. Just because it's not listed on their website means nothing. These people exist to make custom parts. They'll make you ANYTHING you can afford.

I would always go with a proper remap if I actually owned the car.
 
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