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EFI fitment

Weedy

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I guess this is my 1st post/ question here:

I am re-working an old 21' Daytona like jetboat. It was a 454 carb'd beast to begin life with.
I am building an aftermarket 8.1L style engine with Banks TT and HP efi.

The boat has 2ea 30gal aluminum tanks. They are top feed diptube tanks that I suppose fed the 454 one at a time.

I was going to implement in-tank fuel pumps and deadhead feed the engine from one tank or the other or both if necessary. The Turbo would require a boost referenced fuel supply and need both, so a two channel pwm pump control could be a winner. I though two independant pumps so as not to be stranded if one calved.

What do others do with dual tanks? Enlarge the diptubes to 1/2" and run 1 tank at a time thru a 6port and a regulated return.


Thoughts or cautions?
 

rivermobster

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FYI Imco makes -6 1/2 tubes for this kinna thing.

They worked well when we used em.

Good luck!
 

scottchbrite

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I had Anthony at ARA1 tanks build me a new tank with a #10 outlet in the bottom. I know it’s not coast guard approved blah blah blah, but most of a real hot rod isn’t anyway! I’m using a mechanical pump on E85 too. I use a small electric pump in one side that pumps over to the the main tank. Easy and no switching. I can’t worry about loosing prime.

I’d look at doing something like an in tank Walbro set up that bolts in like the modern car fuel tank and ditch the whole factory style dip tube. That way you could size it however you want. It would be all modular.
 

BDMar

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FYI. Any boosted application with a Holley HP EFI (assuming Holley by your "HP EFI") does not require a boost referenced fuel psi regulator. It will need a 1 or 2 bar map sensor. Just tune accordingly. When the boost raises the fuel psi, you have to account for that when tuning. One variable added to the equation.
Also if I'm reading it correct, you can't dead head the fuel psi. It has to have a return to maintain proper EFI fuel pressure.
 

DaveH

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i am a fan of in tank pumps in many applications.

you will have a horrible fuel pressure stability problem with those old un-baffled tanks......making for a very risky setup with a forced induction motor.

no reason not to go with in tank pumps, but careful attention needs to be applied to building in proper fuel baffling. there are a few kits out there for a drop in setup with their own baffling and they work "ok".

wouuld be nice to have an ECU that you can stage the pumps as the fuel supply needs vary greatly from idle to running under boost. if you have a constant duty system that flows enough fuel up top, you will be recirculating (YES you will need to return the fuel to the TANKS) most of the fuel when not under boost, heating up the fuel considerably.
 

Weedy

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It is an Holley HP efi. I am under the impression that turbo systems run a 1:1 boost referenced fuel rail regulator so that the effective injector drive pressure is constant regardless of boost. I plan to tune it with an O2 sensor on the turbo outlets before water is introduced and lock it down and remove the sensor when Im happy.

I dont think Im gonna run a sump fuel outlet on a family boat, just not worth the risk to me.

I too was thinking of an in-tank walbro-like non-return (dead head to me) system with a pressure sensor at each fuel rail ( like any modern car) I would run one to each bank with a manual crossover in case 1 side went down. The brushless variety will with a controller adapt to flow requirements and be adaptable to boost pressure...I believe.
 

Weedy

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Agreed, I will investigate adding some baffling instead of shiny valve covers.
 

DaveH

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to run a dead head system you must have PWM control of the fuel pumps. I dont believe (please double check me) that the holley system can do this. the vast majority of systems run a fuel pressure regulator and return.

even with your regulator manifold pressure referenced, the fuel demand still will vary great;y due to the injectors small opening times at low load vs high engine load. to do this with a dead head system is possible but more complicated to get the pressure stable through the range of operation.

there are some aftermarket fuel pump controllers that may work for what you are wanting to do. but i dont see the advantage as compared to a simpler return style system like most systems people use and are proven.
 

Weedy

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I need EFI fuel pumps anyways, as I don't think I will try and used the mercruiser Coolfuel ver ?? that I have with +2500hrs on it.
With a smaller EFI pump in each tank I can stage them or PWM them and have enough capacity for full throttle use. I believe they will be easier to control that 1 high power pump.

The Holley HP unit has at least 4 spare PWM outputs (2A max, so with a 32A Power mosfet)(30yrs in electronics I can build my own PWM switch) and then I can program it to modulate the fuel pumps to maintain pressure with rpm, load etc and offset it when boost pressure rises. I will try it NA first and thrash boat around with newly baffled tanks and a fuel rail accumulator and see if my fuel pressure logs look good before I add boost to the equation. The fuel pressure logs will show any dangerous pressure drops I think. Potentially I may need to upgrade to the Dominator for more outputs, but the CPU power is the same in each version.

Sadly, I have a lot of projects and a trip in the works so don't look for updates in a week kinda thing.🙃 I havent even finished the heads and valve train yet.
 
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