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Discussion Starter #1
Just bought a 2001 SLK 320.

Sprint Booster is an obvious thing to try.

But what VFM do the multitude of rechip / remaps available on the web actually represent ? Numerous websites claim up to 20 bhp ! Old heads on various forums reckon more like 5 bhp on top end for 200 hp NA petrol engines. However, that's just the top end, what's the effect on the fuelling through the bottom end and midrange. Dyno's for these things are almost non existent ! Is that cos there all crap ?
 

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Discussion Starter #3
Yes, I agree. By Dyno's I was referring to the the same proof you referred to as 'dyno sheets'.

Good old dynojet kits for bikes always included a power curve graph in the box and after you fitted the kit you could believe it because it actually worked. Very suspicious that all the websites claim bhp gains but none have any before/after power curves as proof that it works.
 

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Discussion Starter #4
Suppose my point was that sometimes appreciable gains can sometimes be made in the botom end and mid range by optimising the fuelling/ignition/etc. curves for power rather than to suit the latest enviro fascists regulations. If these re-chips / remaps actually can do that then there may be some value in them ?

Just brings you back to show me the dynos man ?
 

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Discussion Starter #5
OK - So I like talking to myself, you get better answers.

So what do the experts have to say about FSE's ? For the rest of the world, that's the UK acronym for the aftermarket fuel pressure regulator valve that you can buy and plug into the fuel rail and allegedly gives more fuel pressure (at the expense of a rich mixture and less mpg) and hence more power under acceleration ?
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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rt0,

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You wont get far on here as its not a very engine techie forum. I will answer the questions I think you already answered yourself. Fuel pressure device is a waste of time and a bad idea rather like a 2lb hammer to adjust a wrist watch. Chip on a n/a, effect is much like any other application ie it usually feels to drive a bit nicer but not detectably faster. Some have reported they couldnt tell any difference.
 

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First of all, welcome from NW Blighty .. :)

OK - So I like talking to myself, you get better answers.?
JB seems to be talking to himself too.....:confused: Always useful to update your profile so people know where you are and what car you have.

So what do the experts have to say about FSE's ? For the rest of the world, that's the UK acronym for the aftermarket fuel pressure regulator valve that you can buy and plug into the fuel rail and allegedly gives more fuel pressure (at the expense of a rich mixture and less mpg) and hence more power under acceleration ?
Increasing fuel pressure will result in greater fuel flow through the injector at a given pulse width. In open-loop mode (usually only happens at full throttle and in current generation engines increasingly doesn't happen at all) this will cause a richer mixture which may lead to an increase in torque/power, depending on how the engine is mapped. There would be a little more charge cooling, so this is usually a good thing.

As soon as the ECU changes back to closed-loop mode, any nominaly increase in fuel delivery caused by higher rail pressure, will be adjusted out by a reduction in injector pulse width.

Generally with engine tuning, the main challenge is getting more air molecules into the cylinder. This is why turbo/super charging is so effective and why fitting high lift cams with more overlap is common in racing engines. Getting more fuel in is easy.

The next challenge having got more air and fuel in, is achieving a controlled combustion to take advantage of the extra energy available.

Then hopefully the manufacturer has built in some additional mechanical strength in the bottom-end and extra cooling capacity.

With modern vehicles that are optimised around the prevailing emissions regulations, and fuel economy/CO2 footprint, there isn't much spare capacity in the engine design. This is borne out by the trend towards higher power density, where 100hp/litre is not as uncommon as it once was in production car engines.

You may have some spare in your 320, but I'd be surprised if there was much in the way of real performance benefits from a simple remap.

These guys claim 13hp increase...
http://www.superchips.co.uk/search?make=22&fueltype=1&model=334&variant=1128

Good luck..
 

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Welcome from NE England. It's not difficult as JB and GeeJay have said to fill in your user profile.
 

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Does this re-mapping add extra stresses to the engine and introduce added shaft power that manufacturers and engine designers haven't necessarily allowed for in their calcs?
Welcome to the best SLK forum from the North West UK
 

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Discussion Starter #13
Profound apologies to all for not filling in the all important forms in triplicate - now you know I live in the UK that will make all the difference, unless you also need to know I like sewing and gardening to give a fully informed opinion.
 

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Discussion Starter #15
Does this re-mapping add extra stresses to the engine and introduce added shaft power that manufacturers and engine designers haven't necessarily allowed for in their calcs?
Welcome to the best SLK forum from the North West UK
Any extra power or torque produced in an engine will increase the stresses on some of the engine components. But the increases we are talking about are so low (5% max from a remap+air filter+chav exhaust if you are very lucky) that any detrimental affect on the fatigue life of the components is nil or negligible. This is because steels (con rods, valve gear etc.) do not suffer from fatigue failure at all below certain threshold stress levels and most engines (eg. F1 as an exception) are designed to be below that threshold and therefore will never actually fail. Of course this does depend on quality control of the material - which these days is pretty good.

Good example is turbo diesels where the power generated in the the next model is sometimes 20% higher than the last model (eg Audi 2.5 TDI went from 150 to 180 bhp from the same engine). But the same engines still last forever at the higher power level.

Seems the SLK 320 engine is pretty well sorted and does not benefit appreciably from 'tuning' ie. if you want to go faster then you need a bigger engine.
 

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Discussion Starter #16
First of all, welcome from NW Blighty .. :)



JB seems to be talking to himself too.....:confused: Always useful to update your profile so people know where you are and what car you have.



Increasing fuel pressure will result in greater fuel flow through the injector at a given pulse width. In open-loop mode (usually only happens at full throttle and in current generation engines increasingly doesn't happen at all) this will cause a richer mixture which may lead to an increase in torque/power, depending on how the engine is mapped. There would be a little more charge cooling, so this is usually a good thing.

As soon as the ECU changes back to closed-loop mode, any nominaly increase in fuel delivery caused by higher rail pressure, will be adjusted out by a reduction in injector pulse width.

Generally with engine tuning, the main challenge is getting more air molecules into the cylinder. This is why turbo/super charging is so effective and why fitting high lift cams with more overlap is common in racing engines. Getting more fuel in is easy.

The next challenge having got more air and fuel in, is achieving a controlled combustion to take advantage of the extra energy available.

Then hopefully the manufacturer has built in some additional mechanical strength in the bottom-end and extra cooling capacity.

With modern vehicles that are optimised around the prevailing emissions regulations, and fuel economy/CO2 footprint, there isn't much spare capacity in the engine design. This is borne out by the trend towards higher power density, where 100hp/litre is not as uncommon as it once was in production car engines.

You may have some spare in your 320, but I'd be surprised if there was much in the way of real performance benefits from a simple remap.

These guys claim 13hp increase...
http://www.superchips.co.uk/search?make=22&fueltype=1&model=334&variant=1128

Good luck..
Yep, if there was any more easy power to be had it would already be there.

Thanks for the insight on the control loop on modern engines. I have worked closely with PID controlled closed loops on other applications and often wondered how modern car ECU's actually control the mixture etc.

So in summary, we can say with some confidence that if FSE's were any good our well experienced friends, the automobile manufacturers ,would already have fitted them as standard !
 

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I wouldn't bother with an FSE on my car.

Essentially I'm not interested in messing around with a car that cost millions to develop only for me to put some widget on it that was developed by a bloke in a shed in his back garden that is 'claimed' to give some marginal performance benefit that I don't need.

As for the diesel example, yes increasing power by re-mapping tends to have few issues for the engine. Indeed for the VW/Audi TDI engines are very similar between the 115, 130 and 170 hp versions. The clutch isn't the same though. How about the dual-mass flywheel, the gearbox or the brakes or the wheels and tyres or the suspension.....?

It's a bit like overclocking your PC, it's often possible to access that little bit of extra performance that's there because manufacturer built in a little safety margin. Except that when your PC goes breasts uppermost it's only an inconvenience.

Peace. Mod away mate, mod away....
 

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Discussion Starter #18
Fair enough, sometimes power gains by manufacturers (on turbo engines) may mean enough power increase to mean other mods to the engine/powertrain are necessary, but most of the time there is deliberately plenty of spare capacity in all the components to take the extra load. Otherwise myself and all the other purchasers of turbodiesel booster chips would have being reporting engine failures long ago which clearly has not happened.

Would it be impolite of me to ask what academic or professional qualifications in engineering that you hold to issue such purely objective proclamations on the subject ?

Peace, My Sweet Lord, Hare Hare etc.

Regards,

rt05492.

PS Are you by any chance employed by Mercedes Benz ?
 

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Would it be impolite of me to ask what academic or professional qualifications in engineering that you hold to issue such purely objective proclamations on the subject ?

Peace, My Sweet Lord, Hare Hare etc.

Regards,

rt05492.

PS Are you by any chance employed by Mercedes Benz ?
No I don't work for Mercedes Benz. As you say my observations and comments are intended to be objective (thank you, I'll take your remark as a compliment) and I am qualified to make them, though I'm not interested in explaining my professional credentials or affiliations on an internet forum. If we ever meet up at sheep hunt, I'll clue you in.

Have a good Christmas and again, welcome to the forum.
 

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Discussion Starter #20
No need to get personal about the sheep mate, a lot of my best friends are sheep and would be very worried if they thought they were being hunted by humans.

So can we agree to disagree that chips / remaps / filters / chav exhausts represent pretty bad VFM for normally aspirated Merc petrol engines and leave that as a benchmark for other future SLK owners to follow ?
 
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