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Been thinking about this… Can anyone confirm if the car in stock form has a #8 piston fuel starvation issue at the fuel raiil? If so that is an awfully poor design from the factory.
Does that mean every time you romp on the throttle you are effectively starving 1 or a few of the fuel injectors, Causing a lean condition and premature engine wear?
Looped fuel rail. Does it really help with the fuel starvation issue? Or is relocating the inlet location on the fuel rail a better idea.
Wondering if this is something everyone really needs to address.
Is it a problem with stock boost and tune? I heard of it happening but all of the ones I read had a bigger pulley or an aggressive performance tune. It's the main reason I'm afraid of the 77mm cluched pulley. It's just a risk I don't feel it's worth.
Is it a problem with stock boost and tune? I heard of it happening but all of the ones I read had a bigger pulley or an aggressive performance tune. It's the main reason I'm afraid of the 77mm cluched pulley. It's just a risk I don't feel it's worth.
Then that blows, So anyone who goes WOT is essentially risking leaning out the #8 cylinder even in stock trim.
So looped fuel rail even on stock motor? What about the fuel inlet at the #8 position. Is that the real cause? "I think" I've seen some put the fuel inlet between the 2 banks on the fuel rail. But, you would need fittings, welding removal of supercharger and a lot of work to do that.
Isn't the inlet of the fuel rail right next to cylinder #8...
Yes it is. That is one of the issues I suppose. A fuel rail is suppose to pressurize when the car is one so it is "suppose" to have same pressure at each injector. I know the looped fuel rail is suppose to equalize and I am sure it does something.
I think it might be because our cars run very high fuel pressure and maybe that fuel inlet at the #8 injector is disrupted when it takes a big gulp of fuel. I dunno. But, that sucks if it puts our engine at risk of failure.
How do you know it is fuel starvation causing those #8 cylinders to blow? Why not knock?
Looped rails does nothing to alleviate the problem, larger injectors does nothing there too. I have heard of someone increasing fuel to that cylinder via tune and ended up washing the cylinder....failed there too
This car came into my work in the spring. Stock pulleys, bad tune. No. 8.
Wonder who tuned it
Not sure but talking to a local well known tuner he sad it was a very " old school " tune. I guess you could see solder work on the m.e. board. The car will have a new m.e. with a proper tune and the block is now sleeved with forged pistons.
How do you know it is fuel starvation causing those #8 cylinders to blow? Why not knock?
Looped rails does nothing to alleviate the problem, larger injectors does nothing there too. I have heard of someone increasing fuel to that cylinder via tune and ended up washing the cylinder....failed there too
That's what happened to mine.. A washed cylinder...
How do you know it is fuel starvation causing those #8 cylinders to blow? Why not knock?
Looped rails does nothing to alleviate the problem, larger injectors does nothing there too. I have heard of someone increasing fuel to that cylinder via tune and ended up washing the cylinder....failed there too
In the OEM rail the lowest pressure reading will be at the feed inlet point. With a continuous rail, as is the case of the SLR, the pressure will be equal. That said, if the pumps do not provide adequate pressure and flow, all sorts of nasty things are possible.
One more thought, as I have said several times before, I am a great believer in the regular use of a high quality fuel system cleaner which also keeps the pistons, combustion chamber, spark plugs, and valves free of excessive carbon buildup. These buildups can act as a glow plug causing catastrophic pre-ignition. I remember cars in the 50's and 60's that would continue run after switching off the ignition as a result of glowing carbon deposits.
True, that is reason for looped rail and IMO the engineers for the slr (which had higher boost than a stock E55) made the looped rail to equalize the fuel along with bigger injectors. At stock boost unless you have crazy timing I doubt you would have issues.
If that was your #7 or (more likely) your #8, what gouges in the bore you saw probably wasn't a washed cylinder but the result of cylinder temps just beyond the threshold of failure.
The ring gap is very tight from the factory and is just fine for almost any environment in stock form. But when the boost is increased and timing advanced, cylinder pressures rise and the top ring is not made of magical billet unicorn horn it's just plain old humanoid steel albeit a high grade.
So physics demand that it expands ever so slightly and the tiny gap that was present at ambient temps disappears and the ring binds. This makes it twist what little it's allowed in the groove of the piston before putting significantly more pressure on the cylinder bore which causes those scratches.
If cylinder temps go higher still, what comes next is the outer parts of the cast hypereutectic piston just above the top ring get so hot that one of two things happens. Either pieces of the piston fracture and break off which has the effect of a wing nut dropped into a blender as it is ground into bits by the piston and valves, or there is no fracture just the entire piston expands to the point (only .002-.004 tops) where it seizes in the cylinder bore and maybe the rod snaps in half still trying to force the articulation .
Originally Posted by c55asleep?
That's what happened to mine.. A washed cylinder...
And here's a suggestion- send your injectors (or another set which are easy to come by) out to be cleaned and flow tested. Take the highest two and put them into #8 and #7 respectively. That way the slight variation in the flow always favors the leanest cylinder.
Just a thought. Definitely better idea than looping the rail as I don't think that's the reason #8 always goes lean....
And here's a suggestion- send your injectors (or another set which are easy to come by) out to be cleaned and flow tested. Take the highest two and put them into #8 and #7 respectively. That way the slight variation in the flow always favors the leanest cylinder.
Just a thought. Definitely better idea than looping the rail as I don't think that's the reason #8 always goes lean....
That's brilliantly simple chris. If the daamn supercharger didn't have to be removed then I would do this in a heartbeat. I guess when I do the water meth injection kit, Would be the best time for that.
So you are against looping the fuel rail? I can see what it's suppose to do and in theory it should help equalize both sides of the fuel rail.
What about moving the fuel inlet to the middle of the 2 banks? Im sure some guys already done that.
In the OEM rail the lowest pressure reading will be at the feed inlet point. With a continuous rail, as is the case of the SLR, the pressure will be equal. That said, if the pumps do not provide adequate pressure and flow, all sorts of nasty things are possible.
One more thought, as I have said several times before, I am a great believer in the regular use of a high quality fuel system cleaner which also keeps the pistons, combustion chamber, spark plugs, and valves free of excessive carbon buildup. These buildups can act as a glow plug causing catastrophic pre-ignition. I remember cars in the 50's and 60's that would continue run after switching off the ignition as a result of glowing carbon deposits.
What is easiest way to check fuel pressure? Besides tapping into some fuel lines and putting gauge. Lift bank seats and check the plugs for burn marks?
Or would it be how many miles on pumps and sending units? What if you have more then the recommended 60k miles and plugs look good no burn marks?
I got to auto zone and have used a fuel system cleaner. I think it was lucas oils brand. Would that be ok? Anything to look for when choosing and how often do you recommend?
True, that is reason for looped rail and IMO the engineers for the slr (which had higher boost than a stock E55) made the looped rail to equalize the fuel along with bigger injectors. At stock boost unless you have crazy timing I doubt you would have issues.
AGsilver brought up a good point with fuel system. It gets me thinking about fuel pumps and filters. What are your thoughts on mileage intervals.
I am past 60k but, last time I checked I saw no puddling and no burn marks on the fuel pump plugs. Am I good? Or should I change them by mileage intervals no matter what.
He's right on fuel pumps and fuel filters, use only the chevron brand fuel system cleaner. After 60k miles which is the service interval for the filters you should look into it because the pumps usually start working harder because of all the gunk in the filters
No way. I'm definitely not agianst looping the fuel rails since there's nothing bad that can happen as a result, I just don't think it solves the problem. Visualize pressurized air being forced into your plenum tanks ( the two formed aluminum chambers bookending the supercharger with raised AMG ).
Now understand that the #7 and #8 fire in sequence which results in the 8 getting the "sloppy seconds" of both air and fuel since #7 gets fed first ..with physics dictating that the air gets the short end of that stick instead of fuel.
Originally Posted by Max.H
That's brilliantly simple chris. If the daamn supercharger didn't have to be removed then I would do this in a heartbeat. I guess when I do the water meth injection kit, Would be the best time for that.
So you are against looping the fuel rail? I can see what it's suppose to do and in theory it should help equalize both sides of the fuel rail.
What about moving the fuel inlet to the middle of the 2 banks? Im sure some guys already done that.
There's a port on the front passenger side that you can check the fuel pressure. Also, you can remove the fuel rail and injectors without removing the sc.
I had moved the feed point to the middle and also looped my fuel rail. Ice killed my car not mechanical failure, lol.
There's a port on the front passenger side that you can check the fuel pressure. Also, you can remove the fuel rail and injectors without removing the sc.
I had moved the feed point to the middle and also looped my fuel rail. Ice killed my car not mechanical failure, lol.
Any pics of the modified fuel rail? Like what type of fuel lines, fittings, welding an fittings etc? Do you think its a must have?
He's right on fuel pumps and fuel filters, use only the chevron brand fuel system cleaner. After 60k miles which is the service interval for the filters you should look into it because the pumps usually start working harder because of all the gunk in the filters
Ok so then you should have some burn marks if the filter is clogged right? fuel pumps and filters need to be changed at same time? What is recommended to change at 60k. Both or just one?
10-25-2015, 05:25 PM
