tank conversion for EFI

[rlcleeds]

hi what do i have to do with the fuel tank to run injection . i know about fuel return pipe , pump etc but do i need a swirl pot or can i just run the return fuel back into the top of the tank

[baz]

you can run it straight into the tank(i think swirl pots are to take air out of the cooling system )
you can take the sender out and drill near it to put a fitting in then vacuum out the tank , if you desock the outlet at the same time you can rinse out the tank and free the flow

[GTJIM]

Swirl Pots inthe FI fuel supply are there to ensure that the high-pressure fuel injection pump has a constant fuel supply and does not try to pump air - fuel injection systems love air inte fuel - NOT!
Have a look at some of the aftermarket "Rice Boy" stuff that is available - with a swirl pot you don't need to modify your fuel tank just put the fuel return line into the top of the pot as there is usually a line there specifically for that purpose.
The important thing is to ensure that the swirl pot has a constant fuel supply that always keeps the high pressure pump inlet covered with fuel. Some sustems use a high volume but low pressure pump to transfer fuel to the swirl pot which then feeds fuel to the inlet of the High-pressure FI pump. Others just use a gravity feed to the swirl pot. Have a talk to some of the late model Neon/Honda/Toyota/Mitzi/Sub modified car locals and have a look in the speed shops that supply them for inspiration!

[rlcleeds]

jim , so from what you say the swirl pot is the way to go for performance ? but how much is the benifit from using the pot instead of doing it baz,s way

[GTJIM]

With Baz's method you still need to cut into the tank and construct a baffled area around the outlet so that the outlet remains covered with fuel at all times - just bunging the return line into the top of the original tank and using the original outlet is a disaster when the fuel sloshes away from the outlet under heavy cornering with a near empty tank!
A seperate "Rice Boy" Dash Pot ensures that this does not hapen without major surgery on the original tank - just have to put in a 1/2" gravity feed or hook up a high volume/low pressure pump to the original outlet and make some sort of overflow return to the original tank from the dash pot to keep the fuel level in the dash pot correct.
Have a talk to some locals about how they do it on thier "modern" cars!

[baz]

case of geo names i think jim
we would call it an auxiliary tank and for full performance we would mount it in front of the engine so there is an assist from gravity when accelerating (drag thing)
or i think you can get an accumulator tank (1 with a diaphragm inside to hold pressure) that keeps up the flow when you boot it

[GTJIM]

Originally Posted by baz case of geo names i think jim

Yes, Baz. Note that I have even called it two different names: "Swirl tank" and "Dash Pot"!! They sell here in anodised aliuminium or stainless steel. What ever they are called the effect is the same - to keep the high pressure fuel injection pump's inlet pipe always covered with fuel.

[namba209]

Folks, looking at the GT gas tank, if tank is more than a 1/4 full, a "surge" tank or reasonable facsimile is not required. The tank has a fairly deep sump in it already. As for the fuel return line, there was a lengthy discussion on that a while ago, that by running the return line into the top of the tank you will get a continual noise of return fuel running back into the tank. On my tank I welded a steel 1/4" line below the vent line tube, with a 90 degree bend that extended about 2" below the end of the filler neck tube. I plan to slip a hose over the end of the tube and clamp it so the hose will run the return fuel to the bottom of the tank, eliminating the noise caused by the continual flow back to the tank. My fuel rail bypasses at 50 psi, and my fuel pump bypasses at 70 psi, both will return back to the fuel tank through the same fitting at the filler neck.

[GTJIM]

Originally Posted by namba209 Folks, looking at the GT gas tank, if tank is more than a 1/4 full, a "surge" tank or reasonable facsimile is not required. The tank has a fairly deep sump in it already.

Ron, You would be amazed how fuel sloshes around in an unbaffled tank as soon as the tank gets a bit empty. In hard cornering all the fuel will climb up the left or right wall - likewise; fore and aft under braking and accceleration.
Going over railway lines will "stick" the fuel to the top of the tank!
With a carbed motor this interuption to fuel supply is covered by the carb fuel bowl but with FI set ups the fuel pump takes a great big gulp of air and pumps it up through the fuel rail with ghastly consequences!

[namba209]

Jim, I can't dispute that at all, and I was serioulsy considering a "surge" tank, my terminology from model boat racing, or "feed" tank from the aircraft industry, until I figured most of my driving would be freeway stuff, with an occasional blast forward to get up to the posted speed limit. For straight out "spirited" driving a full tank would be adviseable. But, I'm not leaving the possibility of needing one out of the question. I have a quart sized stainless steel filter housing with fittings laying in the garage that may end up being used for that necessity. It's just that there's not a lot of room left over in that area after the dual exhaust is put in.

[GTJIM]

Travelling at 70mph on the Freeway - a quick left-right flick to avoid a piece of 2X4 on the roadway and gaaaah! the motor cuts out because the fuel injectors are pissing air! It's your life ......... a proper "surge tank" is mandatory for a Fuel Injection system. Either built into the tank or a purpose built unit, correctly installed beside the fuel tank. Hash-ups will get you killed.

[baz]

ron if you have the room, put it up front with as jim said a high vol low pressure pump feeding it (+ a low pressure fuel filter ,then you can save the cost of those expensive canister filters ) then the high pressure pump fueling the engine
while you are on you can put the return into the surge tank as it dont need to go to the main tank

[namba209]

Baz, Jim, you've both got really good valid points, and started the creative juices flowing again. I have been in a quandry as to where I was gonna put the fuel filters and pump. Everyone knows, or should know, the best place for an electric pump is as close to the tank as possible. But the configuration of the GT tank having the outlet go through the sheetmetal in the rear, and the need for dual exhaust of the engine makes the options very limited in my case. The best scenario, in my opinion, would be, to have the fuel filters and pump next to the tank, inside the car, behind the fender well. But that's not feasible. The ideas mentioned of having a primary "boost" pump has some merit. There is room, maybe, up front behind the structure where the horns mount to put the surge tank, fuel pump and filter. I'll have to look and do the measuring to see if that can work. Also, with the fuel pump and fuel rail bypassing fuel back to the surge tank up front, I can eliminate some plumbing to return fuel back to the tank, maybe. Or I can run a vent off the top of the surge tank back to the originally planned return fitting on the filler neck. The possibilties boggles the mind. Thanx guys, it's back to the drawing board, again.

[baz]

you might need to do a return for when @ idle thinking about it as the surge tank will fill pdq unless you use a bypass pump as the priming pump

[namba209]

Right Baz, that's why I was thinking about a return/vent line to the orignally thought return line dump fitting at the filler neck. I do have a regular solenoid piston type bypass pump but I'm not sure if it would handle the volume. I guess a test setup would be in order to see if it could handle the requirements of the high pressure pump. Like I said earlier, back to the drawing board.

[oldopelguy]

I'll share my own plan with you guys at this point, either as a suggestion or just for your review, and you cna take it for what it's worth.

With the EFI system you have 2 basic fuel differences versus the stock Opel system, one of pressure and the other of volume. With a carburetor if the fuel comes in surges and sometimes has some air in it it's OK, the fuel in the fuel bowl makes up for it. With EFI there is no where to store fuel just in case there is a sharp turn uncovering the fuel suction or some other glitch in the fuel delivery system.

So here's what I came up with: I'm going to add a fuel return line to the tank, somewhere high enough to not have a lot of back pressure but not so high I get fuel running noises in the tank. Then I'm going to fabricate a new surge tank for the front of the car, with 4 ports in it and a sealed removable access hole. One port, low on one side, will be the fuel "in" port from the tank, and it will be supplied fuel from a very low pressure conventional carb style fuel pump. Another port, on the top, will be for a vent/return line going back to the tank to carry any gases and excess fuel back tot he tank. Idealy the ports and lines will be sized so that this tank is never really under any pressure, it just relieves back to the tank instead of building up.

The other fuel ports, then, will be the fuel out and fuel return ports from and to this smaller surge tank. The fuel will be moved, under pressure, by a conventional in-tank fuel pump mounted inside the surge tank pressurizing a short line to the fuel rail and then through a pressure regulator back to the small surge tank. These will be the only really pressurized lines on the whole system, and as they are short I can justify spending the $ on braided stainless for them to know they'll be safe.

With the pump mounted inside the surge tank, it should cut down on the noise, space, and some of the plumbing issues too. If all goes well, and I can get my favorite TIG welder to do the trick, I want to have a piece of 3"-4" stainless tubing 15" long or so split into two chambers, a top one and a bottom one, with the bottom one being the fuel surge tank and the top being the radiator overflow tank. That should make for super easy mounting and plumbing, and everything sneakily out of sight. If I can't get him to do it, I'm going to buy a 1-2 gallon poly fuel cell, convert it as required, and bolt it in place of the battery when I move the battery to the back. I also plan on adding a big spin-on fuel filter and bracket to the transfer line, to continuously clean my fuel system as I drive.

I've also been giving the electrical wiring of the fuel pumps some thought, and I'm pretty much set on an inertial kill switch for the high pressure surge tank pump and an oil pressure cut off for the transfer pump. In an accident both will shut off but they will both be completely transparent to the normal operation of the car.

[namba209]

That sounds like a good plan Stephen, especially the electrical cutoff switches. I'm gonna be looking into that too, but I want a fuel pump primer setup to move fuel, just in case I run out of gas. I was thinking, considering how far a gallon of gas will get you down the road, and I already have a possible candidate for the surge tank with fittings, a quart sized tank should suffice nicely. My plan, after thinking about it, is to have both the fuel rail and fuel pump bypass back into the surge tank. I'll only need three fittings that way, fuel in, fuel out and vent/pressure back to the fuel tank. My surge tank is a two piece water cartridge filter container held together with a marmon clamp with an 0-ring seal between the halves. My thoughts on it are, it was designed for R V water pressure up to 100 psi, so with the correct 0-ring compatible with fuel, I should be o.k., the fittings are already there and it is chrome plated to add to the appeal of using it.

I already have a circuit in the computer to turn on an oil pressure lite, so if I can use that ground to de-energize the fuel pump relay, I can prevent the pumps from putting out pressure and shut down the engine if the oil pressure goes away. But I'll have to bypass it for starting purposes. More mind boggling stuff.

[baz]

Originally Posted by namba209 I already have a circuit in the computer to turn on an oil pressure lite, so if I can use that ground to de-energize the fuel pump relay, I can prevent the pumps from putting out pressure and shut down the engine if the oil pressure goes away. But I'll have to bypass it for starting purposes. More mind boggling stuff.

ron run a wire from ign 3 (the starter circuit ) to the relay so when you turn to start it will power the relay and when you release on the engine starting the O.P. will be high enough that the circuit for the oil light /pump cutout will be out

[namba209]

Baz, I've rewired the GT and part of the computer circuits to integrate the two, I'll have to go back and see what I did and how to make it all work, using the oil pressure lite circuit as a fuel pump shutoff. I may have to open up some of the harnesses and do a bit of modification to what I've already done in that area. Darn, it just never ends does it?

[rlcleeds]

thanks guys you even started to ask the questions for me .
found this on evil bay would this save the messing about with the swirl pot ? would just need a return fuel ? haven,t checked dimensions yet http://cgi.ebay.co.uk/ws/eBayISAPI.d...MakeTrack=true

[Sportwagon75]

I think Rally Bob's thread had some interesting information on this topic. You might want to check out how he did the fuel pickups for his race car. You can find the thread here: http://opelgt.com/forums/showthread....Quest+Carlisle

[rlcleeds]

thanks for all the info .found this on evil bay. what do you think ? http://cgi.ebay.co.uk/ws/eBayISAPI.d...ADME:B:EF:UK:1

[baz]

that would do the trick and its pre crashed so its had its disaster before you get it