Fuel Rail DIY
02-07-2012, 03:43 PM
#26
MBWorld Fanatic!
The logic why this is a problem at 3/4th gear (and beyond) is the amount of time you spend at wot at high rpm... 1st and second are only brief moments at WOT so the fuel flow has time to catch up assuming it becomes deficient or the injectors go static. In higher gears you spend more time at sustained high rpm leaving more chance for the injectors to go static and for a fuel flow pressure drop to occur - and for longer periods of time, and so there is the possibility of going lean / detonating.
I still dont quite get the physics why the #8 cylinder should be the low pressure point in the OEM fuel rail but evidence suggests its the first cylinder to go for some reason, and so we have to assume there is more of a pressure drop here then elsewhere in the loop.
I think what is critical for us is making sure our cars fuel pressure is up to speed and our fuel pumps/filters are spotless. This is critical IMHO. I think if you have solid pressure / clean system you should be ok with OEM setup, but as we have seen there have been issues with cars going boom ....
I would say SLR injectors should be sufficient on OEM loop but closed loop and SLR injectors should be plenty of headroom. And of course there is the TTM alternative too.
Personally I have neither but then I dont have a very agressive tune... I just have not found a looped rail that looks OEM enough for me yet. On the injector side Kleeman swear you dont need bigger injectors even on K4 + gas flowed heads... so honestly I dont know what to think anymore.
I still dont quite get the physics why the #8 cylinder should be the low pressure point in the OEM fuel rail but evidence suggests its the first cylinder to go for some reason, and so we have to assume there is more of a pressure drop here then elsewhere in the loop.
I think what is critical for us is making sure our cars fuel pressure is up to speed and our fuel pumps/filters are spotless. This is critical IMHO. I think if you have solid pressure / clean system you should be ok with OEM setup, but as we have seen there have been issues with cars going boom ....
I would say SLR injectors should be sufficient on OEM loop but closed loop and SLR injectors should be plenty of headroom. And of course there is the TTM alternative too.
Personally I have neither but then I dont have a very agressive tune... I just have not found a looped rail that looks OEM enough for me yet. On the injector side Kleeman swear you dont need bigger injectors even on K4 + gas flowed heads... so honestly I dont know what to think anymore.
I've recently changed my fuel filter from the Bosch to Mann and my old filter was very clogged according to the blow test and it prob had 100k miles on it. My throttle response before the change was flawless and power was being applied instantly in all scenarios.
After this new fuel filter there is throttle lag and the car just doesn't pull as hard anymore and feels softer. All the data I read shows new filter should increase throttle response/mpg/power. Is there a possibility that a clogged filter somehow raises PSI and throws more fuel into the system or even raise power? What can this be? I didn't think it can be a MANN vs BOSCH issue..The best way I can describe it is like the car is always in the wrong and higher gear as before it was always instantly boom!
Thanks.
02-07-2012, 03:52 PM
#27
Out Of Control!!
The logic why this is a problem at 3/4th gear (and beyond) is the amount of time you spend at wot at high rpm... 1st and second are only brief moments at WOT so the fuel flow has time to catch up assuming it becomes deficient or the injectors go static. In higher gears you spend more time at sustained high rpm leaving more chance for the injectors to go static and for a fuel flow pressure drop to occur - and for longer periods of time, and so there is the possibility of going lean / detonating.
I still dont quite get the physics why the #8 cylinder should be the low pressure point in the OEM fuel rail but evidence suggests its the first cylinder to go for some reason, and so we have to assume there is more of a pressure drop here then elsewhere in the loop.
I think what is critical for us is making sure our cars fuel pressure is up to speed and our fuel pumps/filters are spotless. This is critical IMHO. I think if you have solid pressure / clean system you should be ok with OEM setup, but as we have seen there have been issues with cars going boom ....
I would say SLR injectors should be sufficient on OEM loop but closed loop and SLR injectors should be plenty of headroom. And of course there is the TTM alternative too.
Personally I have neither but then I dont have a very agressive tune... I just have not found a looped rail that looks OEM enough for me yet. On the injector side Kleeman swear you dont need bigger injectors even on K4 + gas flowed heads... so honestly I dont know what to think anymore.
I still dont quite get the physics why the #8 cylinder should be the low pressure point in the OEM fuel rail but evidence suggests its the first cylinder to go for some reason, and so we have to assume there is more of a pressure drop here then elsewhere in the loop.
I think what is critical for us is making sure our cars fuel pressure is up to speed and our fuel pumps/filters are spotless. This is critical IMHO. I think if you have solid pressure / clean system you should be ok with OEM setup, but as we have seen there have been issues with cars going boom ....
I would say SLR injectors should be sufficient on OEM loop but closed loop and SLR injectors should be plenty of headroom. And of course there is the TTM alternative too.
Personally I have neither but then I dont have a very agressive tune... I just have not found a looped rail that looks OEM enough for me yet. On the injector side Kleeman swear you dont need bigger injectors even on K4 + gas flowed heads... so honestly I dont know what to think anymore.
02-08-2012, 12:49 PM
#28
MBWorld Fanatic!
Yep I heard that before although I dont know why. If you think about it you got 4 injectors sucking fuel before the fuel makes it to the ends ... so why presure builds at the ends is a bit odd for me... also the further you are from the pump you will have more pressure drop too no?
If you think about it you got 4 injectors sucking fuel before the fuel makes it to the ends ... so why presure builds at the ends is a bit odd for me... also the further you are from the pump you will have more pressure drop too no?
02-08-2012, 12:56 PM
#29
MBWorld Fanatic!
You seem very knowledgeably on this subject maybe you can answer my question?
I've recently changed my fuel filter from the Bosch to Mann and my old filter was very clogged according to the blow test and it prob had 100k miles on it. My throttle response before the change was flawless and power was being applied instantly in all scenarios.
After this new fuel filter there is throttle lag and the car just doesn't pull as hard anymore and feels softer. All the data I read shows new filter should increase throttle response/mpg/power. Is there a possibility that a clogged filter somehow raises PSI and throws more fuel into the system or even raise power? What can this be? I didn't think it can be a MANN vs BOSCH issue..The best way I can describe it is like the car is always in the wrong and higher gear as before it was always instantly boom!
Thanks.
I've recently changed my fuel filter from the Bosch to Mann and my old filter was very clogged according to the blow test and it prob had 100k miles on it. My throttle response before the change was flawless and power was being applied instantly in all scenarios.
After this new fuel filter there is throttle lag and the car just doesn't pull as hard anymore and feels softer. All the data I read shows new filter should increase throttle response/mpg/power. Is there a possibility that a clogged filter somehow raises PSI and throws more fuel into the system or even raise power? What can this be? I didn't think it can be a MANN vs BOSCH issue..The best way I can describe it is like the car is always in the wrong and higher gear as before it was always instantly boom!
Thanks.
I expect a clogged filter in between tank and pump may affect pump pressure - as it puts more workload on the pump. I don't see how a clean filter would result in a pressure drop unless the flow spec of the filter is insufficient?
The only way a clogged filter will raise the pressure is if the filter sat on the boosted side of the pump (which I expect it does not), and even then the pressure rise would be between the filter and the pump not between the filter and the motor.
02-08-2012, 04:55 PM
#30
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Nice clean set up Grant!
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E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
CL55 UPD Cold Air Boost kit, UPD 3000 stall converter, UPD 77mm SC clutched pulley and beltwrap kit, Custom long tubes, UPD crank pulley , UPD suspension kit, UPD SC pulley, Aux. HE, Trunk tank w/rule 2000 pump, Mezeire pump, UPD 5pc idler set, Aluminum rotor hats.
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02-08-2012, 05:05 PM
#31
MBWorld Fanatic!
Yep I heard that before although I dont know why. If you think about it you got 4 injectors sucking fuel before the fuel makes it to the ends ... so why presure builds at the ends is a bit odd for me... also the further you are from the pump you will have more pressure drop too no?
If you think about it you got 4 injectors sucking fuel before the fuel makes it to the ends ... so why presure builds at the ends is a bit odd for me... also the further you are from the pump you will have more pressure drop too no?
02-08-2012, 05:21 PM
#32
MBWorld Fanatic!
there's no reason to add a loop with this set up...
02-15-2012, 10:32 PM
#33
Ok so at the risk of sounding stupid here, this DIY is simply taking some AN fittings, welding them onto the ends and placing a piece of SS braided between them so the fuel rail has a loop in it instead of terminating at the end? This is simply being done to equalize fuel pressure across all the injectors so you don't get a lean condition from the injector at the end not being saturated with fuel or suffering a pressure drop? Am I understanding this correctly?
I have worked on tons of higher boost Japanese imports but they have return systems and I haven't run across this. Is this a consequence of a returnless system?
Regards
I have worked on tons of higher boost Japanese imports but they have return systems and I haven't run across this. Is this a consequence of a returnless system?
Regards
02-15-2012, 11:27 PM
#34
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Ok so at the risk of sounding stupid here, this DIY is simply taking some AN fittings, welding them onto the ends and placing a piece of SS braided between them so the fuel rail has a loop in it instead of terminating at the end? This is simply being done to equalize fuel pressure across all the injectors so you don't get a lean condition from the injector at the end not being saturated with fuel or suffering a pressure drop? Am I understanding this correctly?
I have worked on tons of higher boost Japanese imports but they have return systems and I haven't run across this. Is this a consequence of a returnless system?
Regards
I have worked on tons of higher boost Japanese imports but they have return systems and I haven't run across this. Is this a consequence of a returnless system?
Regards
02-15-2012, 11:43 PM
#35
MBWorld Fanatic!
does anyone have the specs on the slr injectors? how off do you think the tune would be if we swapped those in?the car would go rich but would the ecu be able to pull enough fuel to compensate?
also what about just running a higher pressure regulator?
also what about just running a higher pressure regulator?
02-16-2012, 07:09 AM
#37
MBWorld Fanatic!
Thread Starter
Ok so at the risk of sounding stupid here, this DIY is simply taking some AN fittings, welding them onto the ends and placing a piece of SS braided between them so the fuel rail has a loop in it instead of terminating at the end? This is simply being done to equalize fuel pressure across all the injectors so you don't get a lean condition from the injector at the end not being saturated with fuel or suffering a pressure drop? Am I understanding this correctly?
I have worked on tons of higher boost Japanese imports but they have return systems and I haven't run across this. Is this a consequence of a returnless system?
Regards
I have worked on tons of higher boost Japanese imports but they have return systems and I haven't run across this. Is this a consequence of a returnless system?
Regards
02-16-2012, 07:18 AM
#38
MBWorld Fanatic!
Thread Starter
The SLR injectors can be used but are very hard to get hold of (VIN is required when ordering etc.) and they are $$$. Last time we checked +$150 each
Either way the tune has to be adjusted to scale for the higher flow injectors.
Fuel regulator - are you referring the the "regulator" on the fuel rail? If so this is actually a pulse damper that prevents hydro dynamic pulses in the rail as injectors close. I believe the SLR has 2 on the fuel rail it uses mainly due to the increased flow of the it's looped rail and higher flow injectors.
02-16-2012, 10:10 AM
#40
MBWorld Fanatic!
You are correct that the result is to try and equalize pressure and prevent starvation of the #8 cylinder in particular. HOWEVER even with a stock looped fuel rail the total volume required to supply all cylinders in higher horsepower cars is not sufficent. This is why there are some guys working on a high flow billet fuel rail.
Prior to looping the fuel rail it was the opposite, though not nearly as noticeable on the stock plugs. If what you say is true, at what power level would this change to a higher volume rail be required? Are there tests proving that this would be necessary?
If people are approaching power levels that would require this mod, wouldn't it be best to build a return system and increase fuel line size? Even if the rail is a monster would the stock lines and pump be big enough to feed it?
02-16-2012, 10:37 AM
#41
MBWorld Fanatic!
Thread Starter
At what horsepower level are you referring to? I haven't done scientific tests, merely datalogging and visual observation, but when I changed my plugs the other day the cylinders closest to the firewall appeared to be the richest (#8). This is with a looped stock fuel rail, TTM injectors, 185 pulley.
Prior to looping the fuel rail it was the opposite, though not nearly as noticeable on the stock plugs. If what you say is true, at what power level would this change to a higher volume rail be required? Are there tests proving that this would be necessary?
If people are approaching power levels that would require this mod, wouldn't it be best to build a return system and increase fuel line size? Even if the rail is a monster would the stock lines and pump be big enough to feed it?
Prior to looping the fuel rail it was the opposite, though not nearly as noticeable on the stock plugs. If what you say is true, at what power level would this change to a higher volume rail be required? Are there tests proving that this would be necessary?
If people are approaching power levels that would require this mod, wouldn't it be best to build a return system and increase fuel line size? Even if the rail is a monster would the stock lines and pump be big enough to feed it?
As for testing the inforamtion is available on another forum but I've sent you the link via PM.
02-16-2012, 10:48 AM
#42
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To be more conservative, any power above 450 rwhp based on dyno mustang (considering weather condition going hot) you will need to have higher flow injectors and also possibly closed fuel rail.
02-16-2012, 12:34 PM
#43
MBWorld Fanatic!
At this point with my current mods I am between 475-500 whp on a mustang dyno, my current fueling setup appears to be adequate, maybe even more than adequate considering that my plugs appearance shows that the BACK cylinders are running rich with the fronts appearing to be normal. I also notice through datalogging that AFR's are at a slightly rich 11.2-11.5.
I apologize for the noobish questions, just wondering if I need to look at upgrading the entire fuel system once I add headers, TB etc...
02-18-2012, 05:12 PM
#46
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grant, did you go with -8an fittings? i picked up a set of -6, and they are way too small, im returning those and going to a -8. i'm having my buddy do the work with a tig welder. i'll post pics once done.
02-18-2012, 06:20 PM
#48
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Most would prefer to silver solder (brazing)
Last edited by pearlpower; 02-19-2012 at 12:33 AM.
02-19-2012, 03:19 AM
#49
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Another option for those more adventurous would be to buy two billets, tap the ends to run lines, etc. Also would need hold downs, still affordable for a custom look
http://www.rossmachineracing.com/dash8.html
http://www.rossmachineracing.com/dash8.html
02-25-2012, 03:43 AM
#50
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Pic of my 2nd rail. This is for another members car. Picked up a used rail for fairly cheap, grinded down the bungs for clearance, used my miter saw to cut the rail, and then my Lincoln to tig weld it up. I go a bit heavy on the bottom as it is so close to the injector, polish both the outside and inside by the welds to clean it up after pressure testing it.
Seen a pic floating around where the bungs are not grinded down. This would make installation very difficult as the clearance on both sides is very tight. Just to clarify, I did this as a favor, not for profit, or interested in another.
Seen a pic floating around where the bungs are not grinded down. This would make installation very difficult as the clearance on both sides is very tight. Just to clarify, I did this as a favor, not for profit, or interested in another.
