Ideas on possible fuel system upgrade

[EllowViper]

SHould have taken pictures of my current set-up. Have basically duplicated what Tim has described although I merge the two pumps outside of the tank. I am running off the stock pump with the Walbro mounted side-by-side in the canister. Fuel pick-up for the Walbro is through a corresponding hole in the bottom of the canister where the stock P/U is located/fed (still inside the plastic mesh on the bottom of the canister...just offset from the Walbro P/U) so I don't drain the canister when the Walbro comes on. I have a -AN6 bulkhead fitting out the top of the canister for this pump. Straighforward connection. WIring comes out the top as well and goes to my W/M relay so I only pump x-tra fuel when W/M comes on. Now the interesting part. I removed the stock connection on the top of the bucket (filed it off flush) and drilled/replaced with a fuel cell -AN6 fitting. No going back at this point since you basically wreck the ability to re-install the stock fuel lines. Now the tricky part is that on the inside of the canister (where the stock system feeds fuel into the regulator and poops fuel out to the stock connection) this area is under pressure unlike the Walbro bulkhead fitting. You will only understand this situation if you have taken apart your regulator inside the basket. You will know what I'm taking about once you get there. Nonetheless, the regulator system is a very simple design that I desired to keep. So with the knowledge that I needed to get an -AN6 fitting to work where the stock line had been, I opted to try a -AN6 fuel cell fitting that had a radiused inlet on the tank side and an-AN6 fitting on the output side. It actually held pressure and worked! So at this point, I have two -AN6 male fitting on the top of my canister ready to be connected to the single -AN6 line going to the fuel rails. I used a two-into-one -AN6 fitting and ran the lines. One thing that I planned for but did not need is a backflow preventor. The Walbro actually has a backflo preventor so I didn't end up using the JEGS one that I had picked up. When the Walbro comes on, it feeds into the common stock replacement line and additional fuel from the stock pump simply gets dumped back into the canistor(just like OEM). I put a intermittent switch on my pillar pod so I can test the relay and actuate the Walbro from the driver's seat. At idle when I do this, the stock regulator keeps up just fine and the fuel pressure stays at around 60-65. SO the ability of the stock regulator to dump excess fuel is pretty good. I was initially concerned that running both pumps at the same time under little load might pump more fuel than the regulator could handle. Not the case based on my testing. Again, the biggest challenge for me was getting a leakproof -AN6 fitting located where the stock plastic injection molded fitting was. So far my approach has worked.

 

[CWhiteRun]

That's interesting. I ran out of fuel at 635 rwhp on the stock fuel pump+BAP and the 8 pound pulley (stock motor).

Bottlefed...where you using water/**** when you put down those numbers?

 

[Red Snake]

Bottlefed...where you using water/**** when you put down those numbers?

He can correct me if I'm wrong but I think he made better numbers on a 6.5 pulley because he has ported heads.

 

[BOTTLEFED]

That's interesting. I ran out of fuel at 635 rwhp on the stock fuel pump+BAP and the 8 pound pulley (stock motor).

I was on 6.5# but with JM heads and Arrow RRs

and yes, W/M
two 325cc nozzles and 50/50 mix coming on 100% by about 4psi

 

[BOTTLEFED]

Eric,
thanks for replying on here. Great minds...

I think your setup proves that my idea my just work. I'd like to see any pics you took of your canister and pumps.
Did you go with -6an for a reason?

I'd still like to hear more ideas on this setup.

 

[AndyMac]

Like someone already mentioned, the walbro has a built in check valve so you would have a redundant system adding the check valve. I also don't know if I like the idea of mixing different pumps to run in parallel.

I like where you're going, and agree that just because we drive a "Viper", doesn't mean everything we do has to cost $$$$$ to be functional. I've gotten grief for building a TT system for less than some pay for a set of tires. (Won't make 1200whp, but turns my NT05's into mush under 60mph)

The fuel system is my winter project so I can start turning the boost up some more. My main issue with running a return-less system, is that if I'm running 25psi of boost, my fuel pressure is down to 30psi, which basically cuts my injector flow rate in half! For me, I need to have a boost referenced regulator. In your situation, if you're only running 10psi tops, having a fuel pressure of 45psi is still adequate, and you just have to worry about flow.

The paxton fmu and dual external walbros seems sketchy, but I am told are very capable (800whp) being fed by the stock fuel pump and using stock lines.. I am considering the paxton design, simply because I have a RT/10 and removing the tank/fuel pump is a PITA..

Anyway, if there is a way to build a cheap/capable/reliable fuel system, I will find it.. lol

Good luck,

 

[EllowViper]

I was considering a boost referenced set up initially but read quite a few articles on the pros/cons of a return system for our basic street set-ups. Bottom line is that I didn't want twin Walbros running all the time and basically returning 90% unused fuel back to the tank after being pumped to the front, heated, pressure built up and then run it back to the tank to repeat the basic cycle. During high boost demand...OK...good idea (thus our current idea of having an additional pump cycle on under boost), but for 90%+ of our street driving, the pressure and capacity is not needed. I also needed to take into account the fact that the return line needed to be as big (if not bigger) that the primary feed line due to the fact that when you heat fuel, it expands and if your engine isn't demanding the additional pressure/flow, and you have too small of a return line, vapor lock or worst can happen. When we are idiling or just crusing around, heat sink in the fuel line/rails can be significant. SO if I run a dead head system any heat induced pressure is bled-off right at the tank within the OEM FPR. If I can increase flow and pressure at the tank simply by plumbing an additional "on demand" Walbro, I get the benefit of "stock" flow and pressure for 99% of my driving and when I hit a boost situation, the flow is increased yet at the same OEM regulated pressure. Given the PSI we are running (12 in my case). My delivered pressure at the injector nozzle is around 48-50 PSI given the 62 PSI readings on my electronic fuel pressure gauge. Running the Siemens DEKA IV 60 lbs injectors (flow rated at 43 PSI). The injectors are well into their sweet spot in regards to flow and duty cycle. Somewhere in the range of 40% from stock so 60% duty cycle. Like you state, if we were running 20+ PSI, a boost referenced system would have been the order of the day...but probably still would sequence in the additional pump "on demand" so I'm only exercising the system to its true potential when its needed. Good discussion.

 

[vprtech]

We have worked on, repaired, and rebuilt many fuel systems at our shop. I would say that sumping, or running a pump pickup to the bottom of the fuel tank with no surge tank or fuel reserve is a unacceptable. Let me clarify one thing about the factory fuel pump, it has two separate functions in the fuel pump module. Any fuel that is pressurized in the fuel system (fuel lines) is drawn directly from inside the fuel pump module, not from the bottom of the fuel tank. There is a small jet that forces fuel through a plastic tube that creates a venturi action that pulls and fills the bottom half of the pump module. The module acts as the surge tank or fuel reservoir, ensuring that the fuel pump is always submerged in fuel whether you are cornering, braking or accelerating . The filling action in the stock fuel pump module is lessened as the head pressure in the fuel line drops. In some situations, such as running additional fuel pumps in series with the stock fuel pump, the pressure can drop enough that the fuel filling volume drops below the volume of fuel leaving the pump module, causing the fuel supply inside the module to dry up. In these situations, a fuel pump voltage booster is an excellent solution. I have not personally seen a fuel pump failure using a variable voltage type booster, and am curious as to why some people are against them. Ford Mustangs cannot really be used as a comparison, as the pumps are pulse width modulated to control fuel pressure and volume. In regards to running the extra pump parallel to the stock unit, maybe you should consider using this in conjunction with a voltage booster.

- Chris

DC Performance: Proven Performance

 

[BOTTLEFED]

Eric,
You know I totally agree with you. There are actually a lot of possible advantages to this type of setup, besides the inexpensive cost. As I've said before, some Viper owners think they need to spend $$ to get piece of mind, not understanding the actual reason for buying it.

Chris,
Thanks for taking the time to post. I think you have made some good points on the possible pickup issues. I'm still on the fence of whether to have the additional pump pick up from the inside or outside of the canister. I highly doubt that the Walbro could drain it in the time it would be running if it was replenished constantly by the stock pump like it should be. I haven't measured the capacity, nor do I know exactly where the pump maintains the fuel level in the canister, but it seems like a liter would be a safe guess.
So that would mean you would have to have your foot into it long enough to use a liter of fuel in one WOT burst. Since 4 liters are in a gallon, and at WOT you might get as low as 4mpg (this is dependent on many factors such as HP and AFRs). That means you should be able to go 1 mile before draining the canister dry. There aren't many times you would need to worry about running the pumps dry. You also have to realize that all the fuel being returned is getting dumped back into the canister and refilling the level.

I was planning on retaining my BAP for this setup. It would only be on the stock pump though.

That electronic FMU sounds really cool, but at $550, its a little out the price range I'm looking at for this setup. I think the w/m pump progressive controller I'm thinking of using should work just fine. Or just borrowing Eric's idea of teeing off the PWM of the VEC for control.

 

[EllowViper]

I would be concerned if the additional Walbro was stealing fuel out of the basket. Not the case ( I wonder if 96-02 have the same design...I'm thinking not). When I turn my basket upside downand look at it. There is oh maybe a three inch plastic mesh cap that fits into a recess in the bottom of the basket (flush with the bottom of the basket). The stock pump gets fuel from the "gap" created where this mesh fitting is and the bottom of the basket. Maybe a 1/4 inch gap. For my Walbro pick-up, I simply drilled a maybe 3/8 hole in the bottom of the basket for the stub to "friction fit" into. So it actually draws fuel from the bottom of the tank (next to the stock pick-up) from the outside of the canister but on the inside of the mesh fitting. Hard to describe but suffice it to say, I retained all the engineering functionality of the stock system with just the addition of a Walbro that feeds from the outside of the canister but on the inside of the mesh screen. Again, hard to visualize without pics. As Tim mentioned, the canister holds a lot and is constantly being overfilled with excess (pressure relieved) fuel. When I tested my relieve valve with compressed air, it can pass a lot of volume back into the basket.

 

[BOTTLEFED]

Yeah, none of that sounds the same as the canister/module I have.

here is a pic that I had of the newer (00-02?) style module - I think this may have been from you, Eric

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and here are some pics of mine (97)

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You can see they are very different.
It almost looks like the newer style has the regulator molded into the top. And for some reason it has a lot less crap on top.
I had to cut that large hose to get it out because I couldn't figure out how to disconnect it. My guess is its a drain-back from the fuel filler neck.
The other, smaller hose connection is like a vacuum/pressure relief. I'm not sure of its purpose.
I like the newer style hose (corrugated plastic line), instead of the black plastic line in the older module.

 

[EllowViper]

Wow. Those are completely different. Yes that is my basket when I just had the Walbro in it as a replacement to the stock one. I think the one I have is a much simpler set up than the older ones.

 

[vipzilla]

hmmmmmmmmm

 

[Dan Cragin]

The earlier pump has the fuel filler breather hose routed into the top of the module. The later cars had the breather hose routed into the top of fuel tank. One important point to consider that Chris mentioned earlier, the pump has a dual function, one is to fill the pump bucket and the other is to supply fuel to the engine. Many pump modifications delete the function of filling the bucket, and will cause the vehicle to starve for fuel (more so in corners) if it does not have more than a 1/4 tank of gas.

 

[Knight Viper]

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What is the best way to get the best of both worlds? I have a triple fuel pump hanger but it doesn't have the benefits of the stock basket. It will be supporting a 2.8L Roe (@12lb's) and hopefully TT in the future. it's out of an RT/10 so I'd like to set it up to not have to worry about upgrades in the future.

 

[Dan Cragin]

You will want to make a fuel basket and have a dedicated pump that fills the basket to supply the pumps.

 

[Knight Viper]

Thank you Dan.
Where is the tread that showed the Roe twin pump set up? I know I saw it here recently but when I went to read it I couldn't even find it using a search.

 

[EllowViper]

Man...this thread brings up some memories! My original twin 'on demand' set-up is still going strong.

 

[latamud]

EllowViper, trying to PM you, your inbox is full. Bart

 

[mbccenter]

EllowViper, trying to PM you, your inbox is full. Bart

I have a complete set up for a gen 3 I am taking out this week