cal1

My suggestion is stay tuned to this thread. It seems to me you would have to go to bigger injectors and looped rail after adding the smaller pulley.

overZealous1

It was hard to see so small but it does look external so easy to do. Just run new fuel line off of filter and go up to rails with it. Then come off the new regulator and tie it into old regulator line going into tank.
Looks like there may be a pressure sensor so if you used a non raising rate regulator and matched stock psi it should fool it.

overZealous1

I agree. You are already past the 80% rule already. So good idea to get them.

amok55amg

overZealous I had a little trouble of getting a screen shot into a pic. for upload …… had to past it in a word????? I see what you mean and it's a very good thing all the items are outside the tank itself .... makes things easier ...... and sometimes the easiest way is the best way …. so will try this before doing anything ells:

Seeing nobody really have the definite answer on this phenomenon so as I see it, then everybody more or less ask: "Do I need looped fuel rail" - "do I need bigger injectors" etc. Well - I don't think the focus is on the right end here since if it's about gasoline (or the lack of it) which curses these detonations; then the question should be: "how do I make sure my engine gets enough gasoline?" ...... and then you should start at the start - at the gas tank and then work yourself forward.

First I think we should understand the needs. That will say we shall conclude how much gasoline a max. tuned sl55amg needs?

Then we will have to do the numbers with the standard gasoline set up .... this will say how much gasoline is it possible to deliver to the fuel-rail with the size of tubing and pump used in the original set-up?

This should be straight forward for somebody who knows stuff ....... anybody out there that knows stuff?

In the mean time I go with the flow ........ https://mbworld.org/forums/sl55-amg-...ml#post5561995

overZealous1

i have heard we use the same fuel pump as the veyron. if that is the case, no need to worry about the pump! it is a pretty big pump though. could be pulled out and tested for flow if someone was so inclined. the rail itself is pretty large. remove the inlet restriction and there is not much room at all for improvement.
for injectors, there are many fuel injector calculators all over the net. imo the 550cc injectors are still too small, but, it is what is tuned with the most so i assume it is a good balance of having a nice idle and still within a somewhat safe duty cycle. when i finally do a real dyno tune on mine we will see where the duty cycle actually is on my 550cc injectors.

amok55amg

well - I know we two talked about this orifice ... this "restriction" - and I said I will take care of it .... I will but this doesn't remove the "restriction" .... the same smaller diameter is to be found in the hose connected to the inlet of the fuel rail (red. "inlet restriction") ... and if you up grade the hose then it's the pipe itself from the pump that become the "restriction" ...... in other words; the "restriction" is all the way .... from the pump to the rail ....... but changing the piping and the hose is easy .... and should (?) be done whether you go for a full return fuel set up or not ...... but will be nice to have the "numbers" to lean at - when I go to work ..... then I know a guy there who can " do stuff"! also will check the pump flow ... must be possible to get the spec. etc. from the manufacturer .......

don't know if I'm offending anybody that reads this but again the problem is - the way I see it - that you have a engine that at some point in a limited range of time use more fuel than the system are able to deliver - the volume of gasoline is to small (and only the volume - the pressure is ok) .... what to do? putt in bigger pipes!

overZealous1

the freeflow amount of the pump would be pretty easy to figure, but pressurized flow is abit tougher.

the main reason to do a return set up is a more consistant fuel pressure to each injector. that is basically it. it helps consistent tuning. the rails on the stock set up is good sized. so, imo, mb did the best they could as it kind of creates a larger volume in the rails to pull from. but, the end injectors could see less pressure than the injectors closest to the fuel inlet. the rails themselves are sized big enough you will not need to make new bigger ones.
hence, the reason for looped rails. it is mearly one way to help try to make the injectors furthest away from the inlet see the same fuel pressure as the rest of the injectors. that is it. that portion has nothing to do with flow or delivery of fuel, which is the direction you are heading towards.
dia of the tubing or fittings is not all that needs to be considered. pressure can make a small opening flow as much or more as a large dia pipe/tube. a lot of the procharger set ups come with a booster pump that loops the fuel system with a one way valve and can create pressures upwards of 100psi in the rails to give the extra fuel needed without changing the size of anything, meaning injectors, rails, fuel pump. this is on returnless systems.

in other words, bigger pipes may do nothing to help save your motor from a lean condition. looping the rails only gives you a little safety of helping you know that each injector is seeing the same fuel pressure (thus squirting the same amount of fuel).
it comes down to tuning imo. i have never owned a chassis that remote tuning is so prevalent. i have done tons of work to mine and i know not to get into it for more than about 3-4 seconds till it actually gets tuned on a dyno. i have also heard rumors of some of the a/f ratios some tuners try to hit and then the customer is surprised and pissed it blew at almost 12/1 a/f with a blower working at near capacity.

there is lots of other things to be looking at for blown motors here than just fuel delivery, which imo is plenty for these hp levels.

cal1

Seems all the factors above could have played a part in the demise of a few engines. I seem to recall a number of years ago some owners asking tuners to push to the limit. Maybe that "limit" wasn't completely clear. Also, I recall some situations were someone had a specific tune, then added maybe an even bigger counter pulley w/o retune. Everything was fine until one cool dry night on a long hard pull, pop goes #8.

I know very little about engines, a mech did all of my modes, but understanding air pressures a bit, I wonder: Say a very agressive tune is done on a hot humid summer day. Now that car is running hard on a cold dry night. How big of a change could that make in AFRs?

overZealous1

here is a very good simple explanation of it.
http://www.kinsler.com/Cat_32_Pgs/Ca..._09_Pg_193.pdf

that is referring to mechanical injection though. our cars run a map sensor to compensate for these changes in density. but, if your tune is pretty far off, there is only so much room the stock ecu can compensate. for those who datalog, look at your short term and long term fuel trims. short term means how much the comp is compensating instantly. long term is what is being held in memory. if your short terms trims are high (scales 0-99%, the 100% being the limitation of the ecu compensation range, but will show - negative or positive) after lots of driving then you may want to get a retune.
if you can tune car close enough to keep your fuel trims down, then the ecu will have a larger compensation range.

cal1

Thanks OZ that link explains it well. I can certainly see how super dense air could be the straw that breaks the Camels back if everything else is pressed to the limit.

I can tell you from my days of flying little private planes, low DA causes a great increase in performance. Some from the engine, but mostly aerodynamic perform.

overZealous1

some of the older private planes had a dial to manually adjust fuel mixture on the "fly". lol

cal1

Absolutely! Big red mixture dial right next to the throttle. On landing and take off, the protocol was to go full rich. At altitude you could trim it out. Most of the planes I was flying (Cessna 150) made a whopping 100 HP on a good day.

amok55amg

In my ignorance I was of the impression the solution to this was to simply to make sure the engine had enough of gasoline – how naive I was.

What I have pick-up is just a few pointers of how complex a high performing gasoline engine really is. It is as a “Swiss watch” …. everything is tuned in a way which lend no room for error or any other “out of the way” modification that is not perfectly adjusted to play in this “symphony of power”. This contribution of mine is quit a read but there’s no short way to put light on this – In other words; if you have modified your car or are planning to do so; then please take the 10 minutes or so to read this.

Many of you guys on this Forum knows the following but I will just run it though for anybody who does not know much about it (like myself) and then I hope if I have gotten something wrong; or have left something major out; then the more experience of you will “tune in” for corrections and add information in a understandable way.

When modifying an engine as the M113 with is standard 500HK and increase it to 600HK or more you will have to make sure you’re having all aspects of the server consequences which can happen if things are not adjusted correctly. Having and driving a car in this “upper end” does not come whiteout responsibilities – any high-performs cars have to be cared and maintained on a regular basis. That will say when you have made your upgrades do not think for a second you just will be able to drive it for years to come whiteout any major maintain schedule to be followed.

Knocking
What can occur when things are not “playing correctly” is a phenomenon called “knocking”; also called knock, detonation, spark knock, pinging or pinking. (Knocking should not be confused with pre-ignition. They are two separate events; however, pre-ignition is usually followed by knocking – more about this later)

Knocking occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The fuel-air charge is meant to be ignited by the spark plug only, and at a precise time in the piston's stroke cycle. Knock occurs when the peak of the combustion process no longer occurs at the optimum moment for the stroke cycle. The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically beyond the engine design limits. If knocking are allowed to continue over time and under extreme conditions the engine can be damage or destroyed. Signs of this state are typically particle wear caused by moderate knocking, which may further passes through the engine's oil system and cause wear on other parts before being trapped by the oil filter. (Examine your oil filter/oil carefully – I’m not sure if there’s a magnet in the oil reservoir – there should be and if so; this should be examine)

Knocking can be prevented in many ways mostly of reducing the load on the engine – but that of curse are not what we are seeking! However the most important thing is the tune so make sure your tune is up-to-date at all times.

• The use of a fuel with high octane rating, which increases the combustion temperature of the fuel and reduces the proclivity to knock;
• Enriching the fuel/air ratio, which adds extra fuel to the mixture and increases the cooling effect when the fuel vaporizes in the cylinder;
• Cooling system has to be at maximum and controlled air intake temperatures are an important factor.

Pre-ignition
Then we come to Pre-ignition. In a spark-ignition engine it is a technically different phenomenon from engine knocking, and describes the event wherein the air/fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is initiated by an ignition source other than the spark, such as hot spots in the combustion chamber, a spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events. (make sure your sparks are the correct ones for your set-up and that they always are up to date)

In the case of highly supercharged or high compression multi-cylinder engines particularly ones that use methanol (or other fuels prone to pre-ignition) pre-ignition can quickly melt or burn pistons since the power generated by other still functioning pistons will force the overheated ones along no matter how early the mix pre-ignites. Many engines have suffered such failure where improper fuel delivery is present. Often one injector may clog while the others carry on normally allowing mild knocking in one cylinder that leads to serious knocking, then pre-ignition. Given proper combustion chamber design, pre-ignition can generally be eliminated by proper spark plug selection, proper fuel/air mixture adjustment, and periodic cleaning of the combustion chambers. Well - this fuel-thing is my “baby” and I will get back to this in the end but ells percussions are to be sure you have the correct injectors and have them cleaned at a regular basis together with you fuel filter – anyone up to clean the combustion chambers at a regular basis? ha ha ha

Causes of pre-ignition

• Carbon deposits form a heat barrier and can be a contributing factor to pre-ignition. Other causes include: An overheated spark plug (too hot a heat range for the application). Glowing carbon deposits on a hot exhaust valve (which may mean the valve is running too hot because of poor seating, a weak valve spring or insufficient valve lash).
• A sharp edge in the combustion chamber or on top of a piston (rounding sharp edges with a grinder can eliminate this cause).
• Sharp edges on valves that were reground improperly (not enough margin left on the edges).
• A lean fuel mixture.
• An engine that is running hotter than normal due to a cooling system problem (low coolant level, slipping fan clutch, inoperative electric cooling fan or other cooling system problem).
• Auto-ignition of engine oil droplets.
• Not putting oil in the engine

Worth to notice is that knocking induced pre-ignition because of the way knocking breaks down the boundary layer of protective gas surrounding components in the cylinder, such as the spark plug electrode, these components can start to get very hot over sustained periods of knocking and glow. Eventually this can lead to the far more catastrophic Pre-Ignition as described above. While it is not uncommon for an automobile engine to continue on for thousands of miles with mild knocking, pre-ignition can destroy an engine in just a few strokes of the piston.
Due to the large variation in fuel quality, a large number of engines now contain mechanisms to detect knocking and adjust timing or boost pressure accordingly in order to offer improved performance on high octane fuels while reducing the risk of engine damage caused by knock while running on low octane fuels. Various monitoring devices are commonly utilized by tuners as a method of seeing and listening to the engine in order to ascertain if a tuned vehicle is safe under load or used to re-tune a vehicle safely. (again – be sure your tune is up-to-date at all times)

As you see “our Swiss watch” has to be cared and nursed for in the proper manner and there’s probably lots of other things to be aware off but this is what I have picked up myself and I hope it will give any of you a little insight that could help you not to be one of the unfortunate members which engines have suffered server knocking/pre-ignition.


I promised to come back to the fuel issue and if we start by summing it up:

Fuel is transported from the fuel tank (via fuel lines) and pressurized using fuel pump to 5 BAR. Maintaining the correct fuel pressure is done by a fuel pressure regulator. The fuel rail is used to divide the fuel supply into the required number of cylinders. The fuel injector injects liquid fuel into the intake air

I have found that an engine with the standard set-up with 500 HK – standard fuel pipe with an inside diameter of ø6 mm. – and with a fuel-pump pressure on 5 BAR will be able to deliver 2,5 l. gasoline per minute.

A engine with 600 HK will need in the about 3,5 l. gasoline per minute on peak load.

A pipe with an inside diameter of ø9,77 mm. will be able to deliver 4 l. gasoline per minutes.

Gentlemen; these numbers speaks for them self!

RAWAMG

Very nice write up Klaus! Thank you very much

amok55amg

This is from my build thread and it shows the residual in the combustion chamber ..... this is a write-up for disaster if not taken care off

If anyone is worried about the state of their pistons + top-head an easy solution would be have the cylinder examine through the holes for the spark plugs with an endoscope camera .... compared to take the top off the engine this will give you’re the peace of mind in a cheap and quick way.


https://mbworld.org/forums/sl55-amg-...ml#post5722103