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Discussion Starter #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/mercedes-benz/slk-classe-r172-from-2011/slk-250-cdi-2143ccm-204hp-150kw-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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Premium Member 2017 SLC200
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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.
 

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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...
 

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Discussion Starter #5
Interesting concept and sounds great, apart from I can't do that myself easily. Going back to my original question, which b0x do people think is best? Thx
 

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Registered 2013 SL63
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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
 

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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
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!
 

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@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:
 

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Discussion Starter #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
 

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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.
 

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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
If your budget doesn't run to a Brabus box does that mean you can't afford the increased insurance premium - or weren't you going to inform them?:frown:
 

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If your budget doesn't run to a Brabus box does that mean you can't afford the increased insurance premium - or weren't you going to inform them?:frown:
My insurance only went up £30/year on my old Audi TT TDi with a remap giving a less than 15% power increase (Admiral).
 

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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.
 

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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.
 

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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?
 

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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.
 

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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.
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).
 

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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...
Tried this mod yesterday, the diff from the 250 petrol does not fit the 250 cdi. The diesel diff is physically far bigger and apparently stronger. I thought I'd just have to change the back plate where it mounts but it is massively different so I just refitted the original.

Pics and more details here.

http://www.slkworld.com/general-discussion/255514-what-did-you-do-your-slk-today-168.html
 

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And if you look closely you will see I replied.

If you are knowledgeable enough to say the old diff is stronger, then you must be capable of changing the actual crown wheel and pinion thus leaving the existing casing and half shafts intact, no?
 
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