Why is the AAM fuel return line needed???
Why is the AAM fuel return line needed???
What is the difference of running AAM fuel return line + 440cc injectors + walbro 255 VS. Stock fuel rails/system + 440cc + walbro 255?
I understand the aam fuel return line comes with better fuel rails/bigger lines so it flows better compared to stock but can't I just make up the difference by adding bigger injectors with the stock rails?
The only difference I see is that with the aam fuel return line it might be good for 440hp out of this setup compared to stock with 440c/walbro it might only get 400hp. Is that worth 1g if I'm trying to stay at 400hp?
I understand the aam fuel return line comes with better fuel rails/bigger lines so it flows better compared to stock but can't I just make up the difference by adding bigger injectors with the stock rails?
The only difference I see is that with the aam fuel return line it might be good for 440hp out of this setup compared to stock with 440c/walbro it might only get 400hp. Is that worth 1g if I'm trying to stay at 400hp?
Last edited by Mr_pharmD; Sep 29, 2006 at 09:05 AM.
Little reading goes a long way. This was written by phunk - and can be found just a few posts down. If that doesnt justify a fuel system on your car I dunno what to say...
Originally Posted by phunk
A nice fuel return system offers many benfits in design to accomplish one very important task: To provide steady and equal fuel pressure to all 6 fuel injectors.
Each restriction in the fuel system (and the stock 350z / G35 contain many) will impede on the overall maximum capacity of the fuel pump at its given voltage. Many think that fluid dynamics say that a chain is only as strong as its weakest link, and increasing flow through some parts of the fuel system will not help if other parts are still more restrictive. Well, this is not a chain folks. Duration and count of restrictions DO MATTER.
The largest restrictions in the factory fuel system include, but are not limited to, every transitional joint quick-clip connector (very small inside diameters), and the pipeing that is feeding the factory fuel rails. The CJM S1 fuel system eliminates every single restriction in the entire system aside from just one remaining factory clip-on connector. The S2 system eliminates that final restriction.
Testing has proven that above 450rwhp, the factory fuel system starts to run into pressure maintainance issues, and you will start seeing substaintial pressure drops by redline... this limiting fuel system capacity.
The other issue addressed, as mentioned, is equal fuel pressure. Having uneven fuel pressure supplied to each injector is risky business. Since your A/F readings are an average of the cylinders in that bank, you do not see that some cylinders are running different A/Fs then others. This pressure gradient will not be visable during lower injector pulse duration moments, such as cruising and idle. But the closer you run to the max, the more this problem will exagerate itself. The factory fuel rail feed pipes are extremely biased and poor flowing. This will cause uneven pressure from one rail to the other, and then limit the rails ability to maintain proper fuel pressure when the injectors are rapidly draining the fuel. You are running risk of uneven fuel pressure from one end of the rail to the other.
The fuel return systems address this issue by substainally increasing flow to the rails and allowing the transfer of fuel into the rails to increase greatly. The second part of eliminating this problem is by putting the fuel pressure regulator after the fuel injectors, rather then before. This ensures that as long as your pump and lines are keeping up with your flow demands, your fuel pressure minimum at the end of the rails will be at your regulator setting. These systems also have a positive side effect of equal pressure balance between each rail. This takes place since the fuel source is split into 2 to meet the rails, and then joins back into 1 after the rails again. Having them connected side to side before and after the rails allows pressure balance.
Another benefit of the return fuel system is the 1:1 ratio regulator. The fuel pressure regulators will maintain an equal pressure differential between the fuel rails and intake manifold. This makes it easier to idle and tune for larger fuel injectors, since at idle your fuel pressure will drop, and in boost it will increase. Having fuel pressure remain the same at all times reduces top end capacity of the fuel injectors, and makes it harder to idle them since the higher pressure will be forcing too much fuel thru the injectors at their lowest responding pulse width.
Last but not least, a proper fuel return system offers you adjustable fuel pressure, which aids in A/F tunability... and also allows for minor end user adjustment to the overall A/F when needed... without having to always take it to the tuner or hook up the laptop and spend time tuning the EMS.
Each restriction in the fuel system (and the stock 350z / G35 contain many) will impede on the overall maximum capacity of the fuel pump at its given voltage. Many think that fluid dynamics say that a chain is only as strong as its weakest link, and increasing flow through some parts of the fuel system will not help if other parts are still more restrictive. Well, this is not a chain folks. Duration and count of restrictions DO MATTER.
The largest restrictions in the factory fuel system include, but are not limited to, every transitional joint quick-clip connector (very small inside diameters), and the pipeing that is feeding the factory fuel rails. The CJM S1 fuel system eliminates every single restriction in the entire system aside from just one remaining factory clip-on connector. The S2 system eliminates that final restriction.
Testing has proven that above 450rwhp, the factory fuel system starts to run into pressure maintainance issues, and you will start seeing substaintial pressure drops by redline... this limiting fuel system capacity.
The other issue addressed, as mentioned, is equal fuel pressure. Having uneven fuel pressure supplied to each injector is risky business. Since your A/F readings are an average of the cylinders in that bank, you do not see that some cylinders are running different A/Fs then others. This pressure gradient will not be visable during lower injector pulse duration moments, such as cruising and idle. But the closer you run to the max, the more this problem will exagerate itself. The factory fuel rail feed pipes are extremely biased and poor flowing. This will cause uneven pressure from one rail to the other, and then limit the rails ability to maintain proper fuel pressure when the injectors are rapidly draining the fuel. You are running risk of uneven fuel pressure from one end of the rail to the other.
The fuel return systems address this issue by substainally increasing flow to the rails and allowing the transfer of fuel into the rails to increase greatly. The second part of eliminating this problem is by putting the fuel pressure regulator after the fuel injectors, rather then before. This ensures that as long as your pump and lines are keeping up with your flow demands, your fuel pressure minimum at the end of the rails will be at your regulator setting. These systems also have a positive side effect of equal pressure balance between each rail. This takes place since the fuel source is split into 2 to meet the rails, and then joins back into 1 after the rails again. Having them connected side to side before and after the rails allows pressure balance.
Another benefit of the return fuel system is the 1:1 ratio regulator. The fuel pressure regulators will maintain an equal pressure differential between the fuel rails and intake manifold. This makes it easier to idle and tune for larger fuel injectors, since at idle your fuel pressure will drop, and in boost it will increase. Having fuel pressure remain the same at all times reduces top end capacity of the fuel injectors, and makes it harder to idle them since the higher pressure will be forcing too much fuel thru the injectors at their lowest responding pulse width.
Last but not least, a proper fuel return system offers you adjustable fuel pressure, which aids in A/F tunability... and also allows for minor end user adjustment to the overall A/F when needed... without having to always take it to the tuner or hook up the laptop and spend time tuning the EMS.
Originally Posted by Mr_pharmD
What is the difference of running AAM fuel return line + 440cc injectors + walbro 255 VS. Stock fuel rails/system + 440cc + walbro 255?
I understand the aam fuel return line comes with better fuel rails/bigger lines so it flows better compared to stock but can't I just make up the difference by adding bigger injectors with the stock rails?
The only difference I see is that with the aam fuel return line it might be good for 440hp out of this setup compared to stock with 440c/walbro it might only get 400hp. Is that worth 1g if I'm trying to stay at 400hp?
I understand the aam fuel return line comes with better fuel rails/bigger lines so it flows better compared to stock but can't I just make up the difference by adding bigger injectors with the stock rails?
The only difference I see is that with the aam fuel return line it might be good for 440hp out of this setup compared to stock with 440c/walbro it might only get 400hp. Is that worth 1g if I'm trying to stay at 400hp?
bing
https://my350z.com/forum/forced-induction/219408-best-return-fuel-system.html
bang
https://my350z.com/forum/showpost.ph...5&postcount=29
boom
Originally Posted by phunk
A nice fuel return system offers many benfits in design to accomplish one very important task: To provide steady and equal fuel pressure to all 6 fuel injectors.
Each restriction in the fuel system (and the stock 350z / G35 contain many) will impede on the overall maximum capacity of the fuel pump at its given voltage. Many think that fluid dynamics say that a chain is only as strong as its weakest link, and increasing flow through some parts of the fuel system will not help if other parts are still more restrictive. Well, this is not a chain folks. Duration and count of restrictions DO MATTER.
The largest restrictions in the factory fuel system include, but are not limited to, every transitional joint quick-clip connector (very small inside diameters), and the pipeing that is feeding the factory fuel rails. The CJM S1 fuel system eliminates every single restriction in the entire system aside from just one remaining factory clip-on connector. The S2 system eliminates that final restriction.
Testing has proven that above 450rwhp, the factory fuel system starts to run into pressure maintainance issues, and you will start seeing substaintial pressure drops by redline... this limiting fuel system capacity.
The other issue addressed, as mentioned, is equal fuel pressure. Having uneven fuel pressure supplied to each injector is risky business. Since your A/F readings are an average of the cylinders in that bank, you do not see that some cylinders are running different A/Fs then others. This pressure gradient will not be visable during lower injector pulse duration moments, such as cruising and idle. But the closer you run to the max, the more this problem will exagerate itself. The factory fuel rail feed pipes are extremely biased and poor flowing. This will cause uneven pressure from one rail to the other, and then limit the rails ability to maintain proper fuel pressure when the injectors are rapidly draining the fuel. You are running risk of uneven fuel pressure from one end of the rail to the other.
The fuel return systems address this issue by substainally increasing flow to the rails and allowing the transfer of fuel into the rails to increase greatly. The second part of eliminating this problem is by putting the fuel pressure regulator after the fuel injectors, rather then before. This ensures that as long as your pump and lines are keeping up with your flow demands, your fuel pressure minimum at the end of the rails will be at your regulator setting. These systems also have a positive side effect of equal pressure balance between each rail. This takes place since the fuel source is split into 2 to meet the rails, and then joins back into 1 after the rails again. Having them connected side to side before and after the rails allows pressure balance.
Another benefit of the return fuel system is the 1:1 ratio regulator. The fuel pressure regulators will maintain an equal pressure differential between the fuel rails and intake manifold. This makes it easier to idle and tune for larger fuel injectors, since at idle your fuel pressure will drop, and in boost it will increase. Having fuel pressure remain the same at all times reduces top end capacity of the fuel injectors, and makes it harder to idle them since the higher pressure will be forcing too much fuel thru the injectors at their lowest responding pulse width.
Last but not least, a proper fuel return system offers you adjustable fuel pressure, which aids in A/F tunability... and also allows for minor end user adjustment to the overall A/F when needed... without having to always take it to the tuner or hook up the laptop and spend time tuning the EMS.
Each restriction in the fuel system (and the stock 350z / G35 contain many) will impede on the overall maximum capacity of the fuel pump at its given voltage. Many think that fluid dynamics say that a chain is only as strong as its weakest link, and increasing flow through some parts of the fuel system will not help if other parts are still more restrictive. Well, this is not a chain folks. Duration and count of restrictions DO MATTER.
The largest restrictions in the factory fuel system include, but are not limited to, every transitional joint quick-clip connector (very small inside diameters), and the pipeing that is feeding the factory fuel rails. The CJM S1 fuel system eliminates every single restriction in the entire system aside from just one remaining factory clip-on connector. The S2 system eliminates that final restriction.
Testing has proven that above 450rwhp, the factory fuel system starts to run into pressure maintainance issues, and you will start seeing substaintial pressure drops by redline... this limiting fuel system capacity.
The other issue addressed, as mentioned, is equal fuel pressure. Having uneven fuel pressure supplied to each injector is risky business. Since your A/F readings are an average of the cylinders in that bank, you do not see that some cylinders are running different A/Fs then others. This pressure gradient will not be visable during lower injector pulse duration moments, such as cruising and idle. But the closer you run to the max, the more this problem will exagerate itself. The factory fuel rail feed pipes are extremely biased and poor flowing. This will cause uneven pressure from one rail to the other, and then limit the rails ability to maintain proper fuel pressure when the injectors are rapidly draining the fuel. You are running risk of uneven fuel pressure from one end of the rail to the other.
The fuel return systems address this issue by substainally increasing flow to the rails and allowing the transfer of fuel into the rails to increase greatly. The second part of eliminating this problem is by putting the fuel pressure regulator after the fuel injectors, rather then before. This ensures that as long as your pump and lines are keeping up with your flow demands, your fuel pressure minimum at the end of the rails will be at your regulator setting. These systems also have a positive side effect of equal pressure balance between each rail. This takes place since the fuel source is split into 2 to meet the rails, and then joins back into 1 after the rails again. Having them connected side to side before and after the rails allows pressure balance.
Another benefit of the return fuel system is the 1:1 ratio regulator. The fuel pressure regulators will maintain an equal pressure differential between the fuel rails and intake manifold. This makes it easier to idle and tune for larger fuel injectors, since at idle your fuel pressure will drop, and in boost it will increase. Having fuel pressure remain the same at all times reduces top end capacity of the fuel injectors, and makes it harder to idle them since the higher pressure will be forcing too much fuel thru the injectors at their lowest responding pulse width.
Last but not least, a proper fuel return system offers you adjustable fuel pressure, which aids in A/F tunability... and also allows for minor end user adjustment to the overall A/F when needed... without having to always take it to the tuner or hook up the laptop and spend time tuning the EMS.
Originally Posted by Alberto
Little reading goes a long way. This was written by phunk - and can be found just a few posts down. If that doesnt justify a fuel system on your car I dunno what to say...
damn you bastard.. you beat me to it
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So is it only worth well to get the aam fuel return line if I'm making over 450hp? So, if i'm not making over 450hp, can't I just add an universal fuel regulator to the stock rail and adjust the idle back down to 52psi if there is an increase in fuel pressure?
Originally Posted by Mr_pharmD
So is it only worth well to get the aam fuel return line if I'm making over 450hp? So, if i'm not making over 450hp, can't I just add an universal fuel regulator to the stock rail and adjust the idle back down to 52psi if there is an increase in fuel pressure?
but contact phunk, the one that wrote that write up, he is a cool guy and takes pride in his work, he owns cj motorsports, go to xxxcjmotorsports. com and check his systems out.
a lot higher quality work for sure
a lot higher quality work for sure
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