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Which fuel rail routing would you choose, and why?
So our Dad & Son project is nearing “first start”, and we are up to plumbing the under-bonnet fuel lines. We have a radium fuel rail, and a Turbosmart fuel pressure regulator. But we have 2 different ways of routing the lines - could folks please chime on which option they would choose, and the reason why:
https://cimg2.ibsrv.net/gimg/www.mia...a62afcd7b.jpeg https://cimg3.ibsrv.net/gimg/www.mia...ea59eff24.jpeg our context is: built engine, GTX2867, ID1050X. Cheers :) |
Originally Posted by ninerwfo
(Post 1464666)
So our Dad & Son project is nearing “first start”, and we are up to plumbing the under-bonnet fuel lines. We have a radium fuel rail, and a Turbosmart fuel pressure regulator. But we have 2 different ways of routing the lines - could folks please chime on which option they would choose, and the reason why:
https://cimg2.ibsrv.net/gimg/www.mia...a62afcd7b.jpeg https://cimg3.ibsrv.net/gimg/www.mia...ea59eff24.jpeg our context is: built engine, GTX2867, ID1050X. Cheers :) |
Typically a dual feed is preferred if you've got the room and ability. You're power levels and fuel requirements will play some part in your decision.
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I use a straight through for reduced failure points and packaging with my M-tuned rail and square top manifold. I'm only running a built 11:1 VVT motor (NA of course) with stock VVT injectors, so my fueling demand isn't high.
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Less points of failure with flammable liquids is my vote, so B. Stock rails are easily good for 400whp with one inlet so...
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I went the dual feed route. but I tried to do it as cleanly as I could. Yes It was more joints/ places to leak but I figured Id just do it "right" cause the last thing you want is to go lean on 1 side.
I got 2 90s right off the rail and straight theu the manifold to a tee then to the stock line. |
I went with B. Easier to plumb and less failure points |
These are all great replies with logical reasoning behind them, much appreciated. But a clearly superior choice doesn’t seem to be emerging - ha ha! If if it helps clarify, we are indeed aiming for more than 400hp, hence the fuel reg and non-stock rail. Is it a drawback of Option A that the rail outlet is so close to one end? Would the fuel just go in the top of the rail and right back out again? The Option B drawback is a lack of dual feed - but is it possible for B to go lean if fuel is going in one end and out the other? It is my poor understanding of “flow” and “pressure” that is causing the confusion here. Assuming we get all our joins spot on, what would be best for performance? |
Flow will take the path of least resistance. In this case the injectors are the easiest path. The FPR will have a base pressure lets say 60psi for example. So you will be forcing fuel through one or both ends of your rail and the line to the FPR will be blocked and act as an extension of the fuel rail until you hit you pressure and it can bleed it off to what you want it to be.
Take it with a grain of salt since my flow knowledge is from the hydraulic industry. But the principals are sound. |
Ahh, actually that is helpful, thanks Mattrussel👍. So from that, would it be true to say that in Option A at full tilt, the fuel reg will be holding up the pressure, such that the path of least resistance is NOT in the top and straight back out the outlet? If so, that seems to negate the main disadvantage of Option A (setting aside number of joins)? |
dual feed is pointless.
show me 1 person who actually: 1) exceeded the capacity of stock fuel rail, let alone larger aftermarket one on a BP 2) leaned out any cylinder ever with oem fuel rail routing I won't hold my breath. So yeah, option B |
Stock rail, flow through, E85 here. I've virtual dyno'd as high as 380whp with no apparent issues. Theoretically that flow would put you close to 500whp on regular gas.
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Dual feed is pointless. If you aren't getting enough volume to pressurize the rail from one end to the other then there's no effectiveness in having an FPR. If you have, for instance, 56psi at the FPR then that's what you have at both ends of the rail and maybe only fractionally less, if any, than what you have at the pump. It's the point of having a regulator.
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But hey, if you wanna do this the "right way", you should consider the BEGi octopus QUAD FEED fuel system with complimentary fuel leaks and 100% guarantee of failure and death :D
You will die with equal injector distribution |
Originally Posted by 18psi
(Post 1464730)
But hey, if you wanna do this the "right way", you should consider the BEGi octopus QUAD FEED fuel system with complimentary fuel leaks and 100% guarantee of failure and death :D
You will die with equal injector distribution /little girl from the commercial |
Dual feeds were probably something carried over from returnless V8's (like LSs). I know a guy who burned up I don't know how many motors in his T1 C5 Vette due to last cylinder leaning out at higher RPM. We finally convienced him to go with a dual feed or return system it was never an issue. That being said, its not something 99.5% of Miata's need. It was just a way to sell more fuel rails and fittings.
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Begi did scientific testing and research/development on this, and the exact factual data is as follows: "we did it, therefore clearly you need this". Hard to argue with facts and data.
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18psi, thanks for the Begi suggestion, but it’s not feasible - the accident investigators would rule cause of death as “suicide” when they saw the kit in the wreckage, so the wife would get no life insurance payout. |
Sixshooter, non-sarcastic thanks for your comment. Of course - if the FPR is indeed regulating, then the dual feed is moot. Nice. |
I built a duel feed rail once because I had free time, machines, and free stock with a motorcycle ITB setup.
That said, It is not needed with the Radium rail. Put a Radium or stock damper in the middle hole. Then use your second drawing. Plenty of people use the stock rail to more HP than the tranny and diff can take. I bought a Radium only to go to a return system, and it will flow tons with a 1 in 1 out setup. Use your second drawing. |
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