Any difference between fuel rails (CJ, KG etc.)?
12-09-11, 03:57 PM
#1
Any difference between fuel rails (CJ, KG etc.)?
I am trying to put together a fuel system to got with my single GTX35R. I already have a supra pump and I am thinking to keep stock primaries and rail. I will buy ID2000 or Bosch2000 injectors and a secondary fuel rail.
CJ motorsports rails look good but I think they are sold in pairs. I emailed them asking if they only sell the secondary rail but no reply so I am thinking to stick with the cost effective and tested KG Parts rail. Are there any other rails I should consider or go ahead and get the KG rail? And is there any point getting a primary rail for stock 550s other than looks?
CJ motorsports rails look good but I think they are sold in pairs. I emailed them asking if they only sell the secondary rail but no reply so I am thinking to stick with the cost effective and tested KG Parts rail. Are there any other rails I should consider or go ahead and get the KG rail? And is there any point getting a primary rail for stock 550s other than looks?
12-09-11, 04:45 PM
#3
Wastegate John
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^^ The stock primary's are side feed injectors. There are no companies that I know of that make aftermarket side feed injector fuel rails, there would be no point.
Which rail you get really, IMHO, depends on what you want and how much you care how they look. The KG rail does it's job well, just does not look as good as the CJ rails do.
John
Which rail you get really, IMHO, depends on what you want and how much you care how they look. The KG rail does it's job well, just does not look as good as the CJ rails do.
John
12-09-11, 04:51 PM
#5
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CJM Primary rail will not work with your stock fuel injectors, its meant for top feed injectors.
The rails can be sold individually but the secondary rail will only mount up if the primary rail is CJM due to mounting clearances. So only the primary would be useable by itself.
The difference is just in how they are made, which is reflected in the difference in cost. Both perform the same function overall. CJM rails are billet machined from scratch. KG rails are cut from a length of universal fuel rail extrusion and drilled and tapped to fit the engine. Billet machining from scratch offers more flexibility in additional features, such as option integrated Y block and more robust mounting via straight through aluminum stands, and more space for cosmetic design... but of course requires more expensive machinery to build and more time to machine, hence the added cost.
In the end, a fuel rail as it functions is just a pipe with holes in it to feed your injectors. There is really nothing exclusive to them. Whichever meets your needs, purpose, visual appearance expectation, and budget, will do the job just as well as any other.
Neither brand will effect performance versus the other, and neither will cause the car to start on fire or anything. Just go with the least expensive option that meets all your needs.
BTW never got your email.
Charles
CJM
The rails can be sold individually but the secondary rail will only mount up if the primary rail is CJM due to mounting clearances. So only the primary would be useable by itself.
The difference is just in how they are made, which is reflected in the difference in cost. Both perform the same function overall. CJM rails are billet machined from scratch. KG rails are cut from a length of universal fuel rail extrusion and drilled and tapped to fit the engine. Billet machining from scratch offers more flexibility in additional features, such as option integrated Y block and more robust mounting via straight through aluminum stands, and more space for cosmetic design... but of course requires more expensive machinery to build and more time to machine, hence the added cost.
In the end, a fuel rail as it functions is just a pipe with holes in it to feed your injectors. There is really nothing exclusive to them. Whichever meets your needs, purpose, visual appearance expectation, and budget, will do the job just as well as any other.
Neither brand will effect performance versus the other, and neither will cause the car to start on fire or anything. Just go with the least expensive option that meets all your needs.
BTW never got your email.
Charles
CJM
12-10-11, 06:09 AM
#6
550cc primaries ID2000 secondaries, supra pump, fpr etc. are sufficient for a single turbo right? Do I need to overkill anything?
I sent 2 messages via the contact section of your website. Last one was 1-2 days ago.
12-10-11, 06:30 AM
#7
Wastegate John
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^ You can use a KG secondary rail with a stock primary rail.
look at post # 2 by theorie in this thread https://www.rx7club.com/3rd-generation-specific-1993-2002-16/where-fuel-setup-parts-list-979704/
550 primarys and ID 2000 secondarys are a good setup for most single turbo setups unless you are going for BIG power or are running E-85.
John
look at post # 2 by theorie in this thread https://www.rx7club.com/3rd-generation-specific-1993-2002-16/where-fuel-setup-parts-list-979704/
550 primarys and ID 2000 secondarys are a good setup for most single turbo setups unless you are going for BIG power or are running E-85.
John
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12-10-11, 07:13 AM
#8
The KG rails works perfectly with the stock primary, that is the purpose of the optional banjo adapter http://banzai-racing.com/store/fuel_rails.html
12-10-11, 11:20 AM
#9
My opinion, I would get both CJ rails with sleeves over the KGs and get Injector dynamics 725/1600 injectors. Not need to spend the extra $$$ for 2200.. With a GT35X I highly dought u will be maxing out the The fuel set up. I have 1000/2200 and it's waaaaaaay over kill.. 725/1600 would have been ideal..
12-10-11, 12:26 PM
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My opinion, I would get both CJ rails with sleeves over the KGs and get Injector dynamics 725/1600 injectors. Not need to spend the extra $$$ for 2200.. With a GT35X I highly dought u will be maxing out the The fuel set up. I have 1000/2200 and it's waaaaaaay over kill.. 725/1600 would have been ideal..
12-11-11, 07:36 PM
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12-11-11, 10:14 PM
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Everything from the firewall forward will be replaced with braided AN hose and fittings. I see a lot of people utilize a y-block to split fuel to feed each the primary and secondary rail. I am planning, for cost and hose routing solutions, to run from the OE hardline to the primary rail, out of the primary rail to the secondary rail, then into the FPR and back to the OE return hardline.
This is how the stock fuel system is setup so I know it will work, but I am curious what the advantages (if any) are to running a parallel feed setup where each rail is feed from the same split feed hose?
12-11-11, 10:35 PM
#15
did some people not read what he wrote ? "I am thinking to keep stock primaries and rail." he never said anything about going with a aftermarket primary rail and stock 550s...
i plan on either doing the 550/2000 or tje 725/2000 when i go single.
i plan on either doing the 550/2000 or tje 725/2000 when i go single.
12-14-11, 12:30 PM
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to run parallel is simply to reduce pressure drops across the system. any restriction inline the plumbing will cause a pressure drop across it, limiting the fuel systems ability to provide fuel to injectors on the other end of the pressure drop. on a setup like the rx7, where its a primary and secondary rail, its not quite a large of a concern, because the primarys and secondaries are essentially tuned seperately anyway. but cars with engines like a V6 for example, where all injectors are tuned off exactly the same tables unless individual cylinder tuning maps are utilized, it can cause uneven tuning. most people do not have the ability to log individual cylinder tuning to make adjustments as such.
a side feed rail and injector system is typically pretty restrictive in terms of flowing through it, because its not a large bore with injectors "T"'d off of it. The injectors themselves are smack dab in the middle of the bore/flow and typically create individual restrictions. I have never seen testing on the stock RX7 primary rail... but I can give an example where the Toyota 3SGTE inline-4 side feed rail experiences a pressure drop of a few psi measured from opposite ends of the rail. Look at this document put together by a popular manufacturer of 3SGTE fuel rails: http://www.wolfkatz.com/Articles/Wol...l%20Report.pdf
You can see the test results of various configurations between the stock rail fed like stock (in one end, out the other), or with the dual feed modifiation (in both ends, out in the center port which was originally used for the cold start injector that everyone gets rid of), or various aftermarket rail test configurations. One combo with the stock rail setup showed a pressure drop of 13psi across the rail. OUCH.
In a nutshell, to eliminate pressure drops in your fuel system overall, improves capacity/headroom in the fuel system with your given configuration (lines, pump output, etc). To eliminate pressure drops inbetween fuel injectors does the same thing, but also helps even-out individual cylinder (or rotor) tuning.
A parallel system is much ideal, especially if you are going to keep the stock side feed primary. Or at the very least, if you are using a larger bore top feed rail, then feed that first and put the primary behind it.
Referencing the document I linked above... you can think of the 3SGTE comparison and relate it to the RX7 easily. Think of the stock configuration which is in one end of the rail, and out the other, as your typical inline plumbing on the RX7. Then look at how improved the pressure drop is when using the "dual feed" plumbing on the rail. You can compare that to your RX7 with parallel plumbing because its like cutting the rail into 2 seperatly fed rails each having 2 injectors. Of course, you must still take this with a grain of salt simply because the sidefeed 3SGTE rail is not the sidefeed RX7 rail... the RX7 rail, innocent until proven guilty, may not suffer from the same pressure drops across it.
The topic can actually get much more in-depth if you wanted to start taking into account the resonances in fuel pressure caused by the opening and closing of fuel injectors in a system that is attempting to maintain a steady pressure.
a side feed rail and injector system is typically pretty restrictive in terms of flowing through it, because its not a large bore with injectors "T"'d off of it. The injectors themselves are smack dab in the middle of the bore/flow and typically create individual restrictions. I have never seen testing on the stock RX7 primary rail... but I can give an example where the Toyota 3SGTE inline-4 side feed rail experiences a pressure drop of a few psi measured from opposite ends of the rail. Look at this document put together by a popular manufacturer of 3SGTE fuel rails: http://www.wolfkatz.com/Articles/Wol...l%20Report.pdf
You can see the test results of various configurations between the stock rail fed like stock (in one end, out the other), or with the dual feed modifiation (in both ends, out in the center port which was originally used for the cold start injector that everyone gets rid of), or various aftermarket rail test configurations. One combo with the stock rail setup showed a pressure drop of 13psi across the rail. OUCH.
In a nutshell, to eliminate pressure drops in your fuel system overall, improves capacity/headroom in the fuel system with your given configuration (lines, pump output, etc). To eliminate pressure drops inbetween fuel injectors does the same thing, but also helps even-out individual cylinder (or rotor) tuning.
A parallel system is much ideal, especially if you are going to keep the stock side feed primary. Or at the very least, if you are using a larger bore top feed rail, then feed that first and put the primary behind it.
Referencing the document I linked above... you can think of the 3SGTE comparison and relate it to the RX7 easily. Think of the stock configuration which is in one end of the rail, and out the other, as your typical inline plumbing on the RX7. Then look at how improved the pressure drop is when using the "dual feed" plumbing on the rail. You can compare that to your RX7 with parallel plumbing because its like cutting the rail into 2 seperatly fed rails each having 2 injectors. Of course, you must still take this with a grain of salt simply because the sidefeed 3SGTE rail is not the sidefeed RX7 rail... the RX7 rail, innocent until proven guilty, may not suffer from the same pressure drops across it.
The topic can actually get much more in-depth if you wanted to start taking into account the resonances in fuel pressure caused by the opening and closing of fuel injectors in a system that is attempting to maintain a steady pressure.
12-14-11, 07:00 PM
#18
^^ Thanks a lot for this valuable information. Funny you gave 3SGTE as an example because I used to own a MR2. It had stock rail, 550cc supra injectors and an external bosch motorsport fuel pump and I did not have any fueling problems or did not notice 
Coming back to the RX7, the reason I want to go stock primaries with aftermarket secondary and ID2000s is the lack of tuners in my country who can tune my car. I am just trying to remove a possible tuning hazard out of the equation but according to others' feedback ID725s idle and behave like stock primaries so my other option would be CJ primary and secondary rails with 2xID725 and 2xID2000.
I found this thread and drawing about parallel set-up:
https://www.rx7club.com/showthread.p...el+fuel+system
If this is the better way to go (or added safety) about the fuel system, it doesn't look to hard or costly to do this, just few extra lines and fittings.
Coming back to the RX7, the reason I want to go stock primaries with aftermarket secondary and ID2000s is the lack of tuners in my country who can tune my car. I am just trying to remove a possible tuning hazard out of the equation but according to others' feedback ID725s idle and behave like stock primaries so my other option would be CJ primary and secondary rails with 2xID725 and 2xID2000.
I found this thread and drawing about parallel set-up:
https://www.rx7club.com/showthread.p...el+fuel+system
If this is the better way to go (or added safety) about the fuel system, it doesn't look to hard or costly to do this, just few extra lines and fittings.
12-14-11, 07:19 PM
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John
12-14-11, 09:05 PM
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Thank you for the information, phunk, very helpful. Makes sense about the side feed rail causing more resistance.
I was planning on running a fuel setup with the feed into the primary rail and then into the secondary, then into the FRP and back to the return, mostly to make routing of the fuel lines easier and save on some hose/fittings, but now I may rethink the fuel system.
I was planning on running a fuel setup with the feed into the primary rail and then into the secondary, then into the FRP and back to the return, mostly to make routing of the fuel lines easier and save on some hose/fittings, but now I may rethink the fuel system.
12-15-11, 08:08 AM
#22
That's what I run.
Inline versus Parallel setup doesn't really change much, truthfully.
I know I posted this in another thread just the other day, but here is my setup:
+ Stock Primary Rail (inlet & outlet tapped to accept AN fittings)
+ Stock 550cc Primary Injectors
+ KG Parts Secondary Rail
+ 1600cc Secondary Injectors
+ Removed FPD
+ Aeromotive FPR
+ "Supra TT" Fuel Pump
+ Modified fuel tank bulkhead
+ Rewired fuel pump (10ga wire all the way from the battery to the in-tank pump, with Bosch 30a relay)
Here's another shot of the primary rail:
Inline versus Parallel setup doesn't really change much, truthfully.
I know I posted this in another thread just the other day, but here is my setup:
+ Stock Primary Rail (inlet & outlet tapped to accept AN fittings)
+ Stock 550cc Primary Injectors
+ KG Parts Secondary Rail
+ 1600cc Secondary Injectors
+ Removed FPD
+ Aeromotive FPR
+ "Supra TT" Fuel Pump
+ Modified fuel tank bulkhead
+ Rewired fuel pump (10ga wire all the way from the battery to the in-tank pump, with Bosch 30a relay)
Here's another shot of the primary rail:
12-15-11, 02:29 PM
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just because someone hasnt (knowingly) blown an engine due to it, doesnt mean its not a possible issue... it just depends on how picky someone is. For me personally, if there is a pressure drop of 5 psi from the first injector in my setup to the last injector... that is not acceptable. For some it may be. The only way to argue it one way or the other is to actually measure the pressure drop or lack of pressure drop. Knowing that it exists in similar configuration with other platforms is enough evidence to arrise a concern or at least caution. But IMHO to spend the $40-50 and plumb it better to eliminate the possibility of pressure drop sounds even better than bothering to test for it and having to reconfigure later if the problem is found.
anyone who is currently running a series setup and havent caused engine damage with it is going to want to chime in and say it isnt an issue... well, thats isnt exactly solid information unless there is test data to support that. i smoke a pack a day and i dont have lung cancer yet.
there is good enough, and there is better. when the investment in better is so low, why not?
anyone who is currently running a series setup and havent caused engine damage with it is going to want to chime in and say it isnt an issue... well, thats isnt exactly solid information unless there is test data to support that. i smoke a pack a day and i dont have lung cancer yet.
there is good enough, and there is better. when the investment in better is so low, why not?
