Fine Tuning RaceChip Pro for 250CDI - Mercedes Benz SLK Forum

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#1 Old 10-04-2015
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Fine Tuning RaceChip Pro for 250CDI

Hi!

So I've installed a RaceChip Pro to my 2015 R172 250 CDI with 7G Trinidad and on the whole I'm pretty pleased with the results. It's on 5000 miles now, with 3500 of those with the chip fitted.

There's no noticeable drop in MPG (I'd actually say there's an improvement on long trips) the flat spots have gone and the torque up to 2500rpm is wonderful!

However... It's in a pretty low setting and even in this setting I'm getting an engine warning light on occasions. I've reduced the settings a couple of times but it's happened again this weekend. The conditions that seem to throw the error up are as follows:

Usually after a longer run (45+ mins on the motorway/A-roads)

Accelerating from mid power at speed to full power/torque at low revs

Happens regardless of gear box setting

The car goes into limp mode, limiting the power and preventing me from changing gear on the paddles.

After 48 hours, it resets itself and I'm back to business as usual.

I wondered if anyone else had experience and could share their settings with me?

Thanks in advance.

Elliot.
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#2 Old 10-04-2015
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Originally Posted by Whiplash View Post
Hi!

So I've installed a RaceChip Pro to my 2015 R172 250 CDI with 7G Trinidad and on the whole I'm pretty pleased with the results. It's on 5000 miles now, with 3500 of those with the chip fitted.

There's no noticeable drop in MPG (I'd actually say there's an improvement on long trips) the flat spots have gone and the torque up to 2500rpm is wonderful!

However... It's in a pretty low setting and even in this setting I'm getting an engine warning light on occasions. I've reduced the settings a couple of times but it's happened again this weekend. The conditions that seem to throw the error up are as follows:

Usually after a longer run (45+ mins on the motorway/A-roads)

Accelerating from mid power at speed to full power/torque at low revs

Happens regardless of gear box setting

The car goes into limp mode, limiting the power and preventing me from changing gear on the paddles.

After 48 hours, it resets itself and I'm back to business as usual.

I wondered if anyone else had experience and could share their settings with me?

Thanks in advance.

Elliot.
Hi Elliot....
Good to see another member tuning their car!!
You're gonna need to take it down a few notches... There's another member with a RaceChip who should chime in shortly. He's had his in for a year.
I've got another brand of box done by my local tuning house... dyno'd to 239hp 373NM... rapidly approaching 10k miles and never looked back, love it!
Uz
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#3 Old 10-05-2015
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Originally Posted by Whiplash View Post
Hi!

So I've installed a RaceChip Pro to my 2015 R172 250 CDI with 7G Trinidad and on the whole I'm pretty pleased with the results. It's on 5000 miles now, with 3500 of those with the chip fitted.

There's no noticeable drop in MPG (I'd actually say there's an improvement on long trips) the flat spots have gone and the torque up to 2500rpm is wonderful!

However... It's in a pretty low setting and even in this setting I'm getting an engine warning light on occasions. I've reduced the settings a couple of times but it's happened again this weekend. The conditions that seem to throw the error up are as follows:

Usually after a longer run (45+ mins on the motorway/A-roads)

Accelerating from mid power at speed to full power/torque at low revs

Happens regardless of gear box setting

The car goes into limp mode, limiting the power and preventing me from changing gear on the paddles.

After 48 hours, it resets itself and I'm back to business as usual.

I wondered if anyone else had experience and could share their settings with me?

Thanks in advance.

Elliot.
Hi Elliott,

How many connections are on the wiring harness? There are usually 2 or 3.

The main cause of the EML coming on is over-pressure on the fuel rail. The high pressure fuel pump is being asked to provide too much fuel pressure so it's erroring out to protect the £2000+ fuel pump.

If you don't clear this error then it will trigger an alert when Mercedes plug it in a service time. So get yourself a £20 OBD fault clearing gimmick from eBay and remove the error.

If it has only one connection, then it's junk, chuck it away.

If it has two connections then it's slightly less junky and you can try turning it down to the lowest setting and thrashing the car. If you have no EMLs, turn it up one setting and do it again. Keep going until you trigger an EML then turn it down to the last setting that didn't give an EML. On a bad dual channel box that can be the OFF setting.

Most tuning boxes are junk. You can often hear an increase in noise from the fuel pump (a tappety noise) and that's bad.

I'm only aware of 2 decent systems in the UK - DTUK have a 3-sensor box and Brabus make a proper CANBus interceptor box that piggybacks onto the original ECU.

I apologise if this sounds harsh but do you really need the extra 40bhp and 100Nm torque? If you do then the Brabus box is £1700 installed and it's really the only sensible option on a brand new car. I assume that this is your own car, not one on finance, PCP or lease because if it is owned by someone else it can get very unpleasant indeed if you get caught out.
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#4 Old 10-05-2015
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Originally Posted by wja96 View Post

Hi Elliott,

How many connections are on the wiring harness? There are usually 2 or 3.

The main cause of the EML coming on is over-pressure on the fuel rail. The high pressure fuel pump is being asked to provide too much fuel pressure so it's erroring out to protect the £2000+ fuel pump.

If you don't clear this error then it will trigger an alert when Mercedes plug it in a service time. So get yourself a £20 OBD fault clearing gimmick from eBay and remove the error.

If it has only one connection, then it's junk, chuck it away.

If it has two connections then it's slightly less junky and you can try turning it down to the lowest setting and thrashing the car. If you have no EMLs, turn it up one setting and do it again. Keep going until you trigger an EML then turn it down to the last setting that didn't give an EML. On a bad dual channel box that can be the OFF setting.

Most tuning boxes are junk. You can often hear an increase in noise from the fuel pump (a tappety noise) and that's bad.

I'm only aware of 2 decent systems in the UK - DTUK have a 3-sensor box and Brabus make a proper CANBus interceptor box that piggybacks onto the original ECU.

I apologise if this sounds harsh but do you really need the extra 40bhp and 100Nm torque? If you do then the Brabus box is £1700 installed and it's really the only sensible option on a brand new car. I assume that this is your own car, not one on finance, PCP or lease because if it is owned by someone else it can get very unpleasant indeed if you get caught out.
Thanks for your help. It's certainly good to learn a little more about the mechanics involved here and what the OBD is doing to protect the components.

Call it my ignorance but I'm unclear on what you mean by 'connections.' Is this the number of ports on the chip, wiring harness or is this something to do with how the chip works?

The RaceChip came recommended by a Mercedes employee but obviously that's no guarantee that it's kosher or that it won't lead to damage. I'd rather be safe than sorry. I'm going to reduce it to it's lowest setting for a drive from the midlands to the Cairngorms next weekend and maybe tinker with it over the course of the week as it'll be doing some lengthy journeys while we're up there.

Uz, thanks for the your help too. I'm going to make contact and see if there is any advice or experience I can take form him too.

If push comes to shove, I'll remove it. It's a shame though as it's proven a genuine improvement in the cars flat spots and slightly sluggish gearbox responses - Clearly there is a trade off though...
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#5 Old 10-05-2015
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By connections I mean how many places it plugs into the cars wiring loom.

The most basic systems plug in only to the fuel rail. All they can do is increase the fuelling over standard so if the car calls for 100mg of fuel the box intercepts that signal and tells it to add 110mg of fuel which is fine but it does tend to just make particulates which messes up the DPF. Not a good thing!

The next type of system plug into the fuel rail and the turbo boost sensor so it has some idea of how much air the car is adding so if it wants 100mg of fuel and it's making no boost, the ox adds no extra fuel. If the car is making 1 atmosphere of boost it will add 110mg of fuel and at 2 atmospheres of boost it might add 125mg of fuel. So you get some aspect of the fuel to air ratio being maintained which limits particulates and makes more power safely.

Finally, the three sensor systems add a sensor on the camshaft so they know the engine speed. If you know the engine speed you can plot the boost for any given fuel input and you basically have a proper remap in a box. On the latest petrol tuning boxes they have anything up to 7 sensors so they don't melt anything.
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#6 Old 10-05-2015
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Originally Posted by wja96 View Post
By connections I mean how many places it plugs into the cars wiring loom.

The most basic systems plug in only to the fuel rail. All they can do is increase the fuelling over standard so if the car calls for 100mg of fuel the box intercepts that signal and tells it to add 110mg of fuel which is fine but it does tend to just make particulates which messes up the DPF. Not a good thing!

The next type of system plug into the fuel rail and the turbo boost sensor so it has some idea of how much air the car is adding so if it wants 100mg of fuel and it's making no boost, the ox adds no extra fuel. If the car is making 1 atmosphere of boost it will add 110mg of fuel and at 2 atmospheres of boost it might add 125mg of fuel. So you get some aspect of the fuel to air ratio being maintained which limits particulates and makes more power safely.

Finally, the three sensor systems add a sensor on the camshaft so they know the engine speed. If you know the engine speed you can plot the boost for any given fuel input and you basically have a proper remap in a box. On the latest petrol tuning boxes they have anything up to 7 sensors so they don't melt anything.
That makes sense. It has two plugs in that case.
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#7 Old 10-06-2015
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One other thing, if you are looking at fuel economy on the on board computer then it will be wrong with a tuning box fitted.

When the car works out your fuel economy it adds up all the fuel it has injected. If it has been calling for 100mg per injector pulse and the tuning box has been adding 110 then your fuel economy is wrong by that extra 10%.

The car doesn't know that because it's unaware you are injecting more fuel every injector pulse. And because the extra fuel is added by increasing the fuel rail pressure (more pressure means more volume) if the tuning box calls for enough pressure to damage the high pressure fuel pump, the fuel pump protection throws an error and the car goes into limp home mode, which is exactly what you are seeing.

So all the comments about the box being safe because it operates within the parameters of the car are nonsense. The tuning box is completely dumb in that respect. It just keeps asking for more depending on what setting you have dialled in. If you dial in too much, the EML comes on. The car isn't showing an error because something safe has happened, it showing an error because the cars own protection has kicked in or it has recorded an impossible value that it can't work with.

Those values are recorded in the system, hence my advice to buy a device to clear the fault codes. It will also stop you having to drive the car in limp home mode for 48 hours.
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#8 Old 10-06-2015
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This is very well put imo.

I, like many others, are sceptical of these magic boxes. They all claim extra power and better mpg. Mercedes Benz development is a pretty large and deep pocketed collection of specialists. I am sure if they could have found a few more hp for a few hundred bucks, they would have, But they have weighed everything up and given the best all round solution possible for the money I am sure.

Having said that, there are always trade-offs. It could well be that to get the best economy, they have had to allow some 'flat spots'. Now if your need is for a smoother accel;eration path and economy is second, then these little boxes come into their own, so I echo the advice: clear the codes and start off again at the lowest setting and gradually work up a few notches and get the optimum. This way you will be happy. Again, I echo the advice to pay concern to the pump - overloading it is not a good idea. And remember, diesels are more sensitive than petrol in the finer points of fuel delivery.

Interestingly, or maybe not(!), I think I have a chance of getting hold of a power box on a long term loan, the type that Brabus and Vaeth etc use. If I do get it, I shall do a before and after dyno just to show once and for all that the claims they make - even Brabus - are highly theoretical. I had a heated discussion with Brabus a while back regarding their claims on the B25 box. The chap there, Tobias, insisted that 50 extra bhp was normal, but could not (or would not) produce any dyno sheets backing this claim. But he says he has seen them (!). Then I rather took the wind out his sails by asking if the 50 claimed horses was on the crankshaft or at the wheels… They just do not realise that the machinery required to measure Crankshaft bhp is very expensive and only theoretically calculable on a dyno - the 7G box loses about 18-20% through the train, so that an extra 50 bhp at the wheels is some 60 on the crankshaft. Just not possible on an M271 engine! Exit left, Mr Brabus! Anyway, more later depending if I can get my hands on this box.
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#9 Old 10-06-2015
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Originally Posted by Hal Adams View Post
This is very well put imo.

I, like many others, are sceptical of these magic boxes. They all claim extra power and better mpg. Mercedes Benz development is a pretty large and deep pocketed collection of specialists. I am sure if they could have found a few more hp for a few hundred bucks, they would have, But they have weighed everything up and given the best all round solution possible for the money I am sure.

Having said that, there are always trade-offs. It could well be that to get the best economy, they have had to allow some 'flat spots'. Now if your need is for a smoother accel;eration path and economy is second, then these little boxes come into their own, so I echo the advice: clear the codes and start off again at the lowest setting and gradually work up a few notches and get the optimum. This way you will be happy. Again, I echo the advice to pay concern to the pump - overloading it is not a good idea. And remember, diesels are more sensitive than petrol in the finer points of fuel delivery.

Interestingly, or maybe not(!), I think I have a chance of getting hold of a power box on a long term loan, the type that Brabus and Vaeth etc use. If I do get it, I shall do a before and after dyno just to show once and for all that the claims they make - even Brabus - are highly theoretical. I had a heated discussion with Brabus a while back regarding their claims on the B25 box. The chap there, Tobias, insisted that 50 extra bhp was normal, but could not (or would not) produce any dyno sheets backing this claim. But he says he has seen them (!). Then I rather took the wind out his sails by asking if the 50 claimed horses was on the crankshaft or at the wheels? They just do not realise that the machinery required to measure Crankshaft bhp is very expensive and only theoretically calculable on a dyno - the 7G box loses about 18-20% through the train, so that an extra 50 bhp at the wheels is some 60 on the crankshaft. Just not possible on an M271 engine! Exit left, Mr Brabus! Anyway, more later depending if I can get my hands on this box.
Mine was dyno'd and verified Hal!
Uz
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#10 Old 10-06-2015
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Search on "optimistic dyno" to see how useful dyno's are for sales people.

If you had back to back runs then the % increase is valid but the absolute figures could be total nonsense.
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#11 Old 10-07-2015
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Originally Posted by wja96 View Post
Search on "optimistic dyno" to see how useful dyno's are for sales people.

If you had back to back runs then the % increase is valid but the absolute figures could be total nonsense.

The car had back to back runs over 3 hours at MSL while they adjusted the box settings.
The car actually makes slightly more 239hp on 373nm... it made 243hp on 373NM but the LOWEST reading was 239hp on 373 and that's what I've gone with.
It still hits 60 in 5.7 seconds (GPS stopwatch). It still hits 155mph. It wouldn't be able to if it didn't have that kind of power.
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#12 Old 10-07-2015
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Originally Posted by u_2504 View Post
The car had back to back runs over 3 hours at MSL while they adjusted the box settings.
The car actually makes slightly more 239hp on 373nm... it made 243hp on 373NM but the LOWEST reading was 239hp on 373 and that's what I've gone with.
It still hits 60 in 5.7 seconds (GPS stopwatch). It still hits 155mph. It wouldn't be able to if it didn't have that kind of power.
What did it make on the first run, without the box fitted?

There is a decent tuner in East Anglia, JabbaSport, who have an infamously optimistic rolling road. There was a guy on the Skoda forums who was claiming 260bhp from his 1.9TDi and he produced his JabbaSport rolling road plot to prove it. When it was pointed out that his car (140bhp standard) made 170bhp BEFORE it was modified he took it to Shark in Mansfield where it made 220bhp.

So an optimistic dyno will give you high start and finish figures but the relative increase is valid.
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#13 Old 10-07-2015
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Actually, I found it - it was 5bhp up on what Mercedes claim at 186bhp to start with so you could validly claim the increase from 186 to 239 is 53bhp or 28.5%. Which is a lot for a tuning box.

But it's just as valid to say the dyno reads 5 bhp high and your real power is 234bhp. It's still a 53bhp increase. That was my point.

You can make a dyno say anything. The marketing men love an optimistic dyno because it makes for great headline figures.
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#14 Old 10-07-2015
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Originally Posted by wja96 View Post
Actually, I found it - it was 5bhp up on what Mercedes claim at 186bhp to start with so you could validly claim the increase from 186 to 239 is 53bhp or 28.5%. Which is a lot for a tuning box.

But it's just as valid to say the dyno reads 5 bhp high and your real power is 234bhp. It's still a 53bhp increase. That was my point.

You can make a dyno say anything. The marketing men love an optimistic dyno because it makes for great headline figures.
It made 186hp on 271NM on the first run. Peak torque @ 3.5k (I THINK) I can't remember. I will dig out the dyno graph when I get home tonight. It used to hit 60 in 6.9seconds with me brake boosting to try maxing out the launch from a standing start... also, I did the dyno with the car running 99 Momentum from Tesco. Apparently that can make a couple of horsepower difference. The custom backbox also makes a minute difference also, but basically nothing. Other factors like temperature make a difference with the box also. It doesn't allow for the extra power when it's too hot (or cold) for that matter. On these cold morning starts, the car acts like stock, when it's too hot, it doesn't give me as much extra power either (boost drop.)

My uncle (Remapped E55 owner) strongly believes that MSL's dyno underreads slightly because he does Dyno days all over the country and he's getting 599HP out of MSL, but nearer 620HP from everywhere else he's been. But, that was enough power to make me puke the first time he took me out in it!! :P

If you are able to come down for the next SLK meet I will happily take you for a ride in the car and you'll notice the difference immediately. Hal, offer stands to you too if you're ever in these neck of the woods!
I've done 10k miles with the box in now.

Uz


Just noticed your most recent post, yeah even if it's over read by 5hp, it's still an amazing gain.... 230-240HP from a 1.8T, 10k miles no issues (except more tire wear from driving style) same fuel economy...
Bigger exhaust headers, intercooler that'll get another 5-10HP and that's the most this car will ever achieve. Then time to save hard for a 55!
There's a dude in Singapore who has Vaeth'd his 200 to the limit; remap / intercooler / exhaust and he's dyno'd to 249hp. I will dig out that thread on MB world and post it when I get a chance.
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#15 Old 10-07-2015
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Originally Posted by u_2504 View Post
The car had back to back runs over 3 hours at MSL while they adjusted the box settings.
The car actually makes slightly more 239hp on 373nm... it made 243hp on 373NM but the LOWEST reading was 239hp on 373 and that's what I've gone with.
It still hits 60 in 5.7 seconds (GPS stopwatch). It still hits 155mph. It wouldn't be able to if it didn't have that kind of power.
Sorry Uz, but you have been fed erroneous information.

Power, torque, acceleration and top speed combine to make a difficult subject. Power and torque on their own are meaningless figures. You need weight, gear ratios and the final drive ratio to make the complete picture.

The car manufacturer will determine what is optimum for its customers - eg for a small engined car, light body weight, 4 door shopping car, they will decrease the final drive ratio to produce economy at the sacrifice of top speed and acceleration. On something like an SLK2s, they will reverse this to a certain extent to give either acceleration OR final speed. You cannot have both! Here is where power comes in - you need power (bhp) to acquire both acceleration and speed. All this is done by altering the final drive ratio and nothing else.

So, a 200 has a 3.07 final drive giving 7 odd secs 0-60 and 147mph top speed. You can get the acceleration better through more power. You cannot increase the top speed as this is dictated by the RPM and the final drive (OK, you can increase the RPM, but this only by nitriding the crankshaft and steel conrods etc - an extremely expensive procedure) So your car will never exceed 147mph with the standard 3.07 final drive and limiter. To get 155mph, you will need to switch off the factory limiter (highly illegal) and then determine what the RPM allow on a 3.07 final drive and change it accordingly - maybe down to a 2.9. But this change will drastically reduce acceleration time.

Now the 55 has a 2.8 final drive BUT it also has an excess of power - some 400 odd bhp. This overcomes the drag of a 2.8 final drive to give a sub 5 second acceleration AND as it is a low final drive, able to produce the 155mph.

As WJA says, the dyno people - and sales people - will give the best figures. The first point here is 'what is being measured' - so you are told you have 239 bhp. Where? At the wheels or the crankshaft. What loading was applied to the rollers? More often than not, no loading is applied. In real life, the road condition and wind resistance will dramatically hit the acceleration times. If they tell you the bhp is at the wheels, this means your engine is producing some 300bhp at the flywheel. Just not possible I am afraid. I would ask questions of when the dyno was last calibrated and by whom. Most dynos are not regulated, so treat them as indicators.

By no means am I saying you do not have any increases in your figures, I am simply confirming what has been said already, and advising you to be cautious.

Now, if you were to have a genuine 50bhp increase at the wheels, and top speed is not an issue, you have enough to allow you to change the final drive to a 3.27 that would give you a genuine sub 6 second acceleration. This ratio was fitted to the early 250CGi cars but change in late 2013 back to 3.07 as the only difference in acceleration was half a second but there were a lot of complaints from owners (I think in Germany) that top speed was more important, so the drive was changed to 3.07!

As I say, a complex subject, and if I may observe, one that you are worrying too much on…your car is already nippy - why not leave it as is?
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#16 Old 10-07-2015
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Originally Posted by Hal Adams View Post
Sorry Uz, but you have been fed erroneous information.

Power, torque, acceleration and top speed combine to make a difficult subject. Power and torque on their own are meaningless figures. You need weight, gear ratios and the final drive ratio to make the complete picture.

The car manufacturer will determine what is optimum for its customers - eg for a small engined car, light body weight, 4 door shopping car, they will decrease the final drive ratio to produce economy at the sacrifice of top speed and acceleration. On something like an SLK2s, they will reverse this to a certain extent to give either acceleration OR final speed. You cannot have both! Here is where power comes in - you need power (bhp) to acquire both acceleration and speed. All this is done by altering the final drive ratio and nothing else.

So, a 200 has a 3.07 final drive giving 7 odd secs 0-60 and 147mph top speed. You can get the acceleration better through more power. You cannot increase the top speed as this is dictated by the RPM and the final drive (OK, you can increase the RPM, but this only by nitriding the crankshaft and steel conrods etc - an extremely expensive procedure) So your car will never exceed 147mph with the standard 3.07 final drive and limiter. To get 155mph, you will need to switch off the factory limiter (highly illegal) and then determine what the RPM allow on a 3.07 final drive and change it accordingly - maybe down to a 2.9. But this change will drastically reduce acceleration time.

Now the 55 has a 2.8 final drive BUT it also has an excess of power - some 400 odd bhp. This overcomes the drag of a 2.8 final drive to give a sub 5 second acceleration AND as it is a low final drive, able to produce the 155mph.

As WJA says, the dyno people - and sales people - will give the best figures. The first point here is 'what is being measured' - so you are told you have 239 bhp. Where? At the wheels or the crankshaft. What loading was applied to the rollers? More often than not, no loading is applied. In real life, the road condition and wind resistance will dramatically hit the acceleration times. If they tell you the bhp is at the wheels, this means your engine is producing some 300bhp at the flywheel. Just not possible I am afraid. I would ask questions of when the dyno was last calibrated and by whom. Most dynos are not regulated, so treat them as indicators.

By no means am I saying you do not have any increases in your figures, I am simply confirming what has been said already, and advising you to be cautious.

Now, if you were to have a genuine 50bhp increase at the wheels, and top speed is not an issue, you have enough to allow you to change the final drive to a 3.27 that would give you a genuine sub 6 second acceleration. This ratio was fitted to the early 250CGi cars but change in late 2013 back to 3.07 as the only difference in acceleration was half a second but there were a lot of complaints from owners (I think in Germany) that top speed was more important, so the drive was changed to 3.07!

As I say, a complex subject, and if I may observe, one that you are worrying too much on…your car is already nippy - why not leave it as is?
Hey Hal...
Thanks! The car is a hobby so I love researching all sorts into it..
Anyway, look, I know what I've got out the car.. there's always different angles of minutia to go into (and honestly, you know so much about this car it's amazing to read!) but the bottom line is, it's fast, the right brand of box is just as good as an ECU remap in my opinion, no issues yet... the numbers are what i've got out of the car.
When I get a chance, i'll go pro it to show you... I'd love to show you how it drives anyway, I think you'd like it considering your history with the M271 engine
Uz
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