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Old 05-06-10, 06:41 PM   #1
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going from carb to fuel injection with carbed gas tank

I know there are people out there that have swapped their 1st gens to fuel injection. But I'm curious how they went about it with the gas tank.

Did you track down a gls-se tank or did you just use the carbed tank that was in there?

And if you just used the carbed tank was is just as simple as replacing the fuel pump with an aftermarket inline fuel injected pump and high pressure fuel line or was there more to it.

Also if you used the carbed tank, any concerns about the venting on the tank.

Any thoughts and input would be much appreciated
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Old 05-06-10, 08:15 PM   #2
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i am just starting to get all the parts together for my efi turbo 2 swap into my 85fb . i didn't even think about the gas tank. i will probably just weld on some AN fittings and run high pressure s.s. hoses. for the feed and return . as for the vent i will wait to see what someone else posts here.
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Old 05-07-10, 03:56 AM   #3
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best bet would be a lift pump to a swirl pot then Fi pump from there
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Old 05-07-10, 04:01 AM   #4
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You have 2 options. Add a low pressure high volume carb fuel pump and a surge tank, along with the efi pump, or have the tank modded for a 2nd gen in tank fuel pump. I have modded several S3 tanks to take the S4 in tank pump. I find it to be a cleaner and better system than 2 fuel pumps and a surge tank.

It's a bit more expensive to go with the modded tank, but safer in the long run, especially for turbo-ed engines. There should be plumbing diagrams in the archives for the surge tank setup.
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Old 05-07-10, 04:05 AM   #5
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Directfreak made 470whp with a GSL-SE tank and external pump. I have a plain jane -se tank with a bosch 044. Never had fuel issues. The -se has baffles that center fuel around the pickup, and rather large feed and return tubes.

Like I said, turbo'd at 250whp and no problems with mine, and I enjoy the twisties. Bigger, turbo, still no gas problems. If I ever run into starvation issues I'll build an external swirl tank with a carbed pump right off the main tank, but the -se tank is staying.
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Old 05-07-10, 04:30 AM   #6
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To repeat myself again, all tanks have a baffle plate that runs front to back, down the center of the tank. The SE tank has a sump cup that both the supply and return lines drop into. The 2nd gen sump cup is nearly 5 times the volume of the SE cup. None of the carbed tanks have the cup.

John, I agree, an SE tank is the minimum needed for FI with it's sump cup and larger supply/return lines. But Mazda went with the larger sump cup for a reason. I like the idea of the modded tank because it uses only 1 fuel pump and the in-tank pumps are very quiet. BTW there's no difference between 2nd gen NA and TII tanks.
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Old 05-07-10, 11:48 AM   #7
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You have 2 options. Add a low pressure high volume carb fuel pump and a surge tank, along with the efi pump, or have the tank modded for a 2nd gen in tank fuel pump. I have modded several S3 tanks to take the S4 in tank pump. I find it to be a cleaner and better system than 2 fuel pumps and a surge tank.

It's a bit more expensive to go with the modded tank, but safer in the long run, especially for turbo-ed engines. There should be plumbing diagrams in the archives for the surge tank setup.
do you have any pics or links to the modded S3 tanks. i would like to just stick with one pump if possible, the less crap the better. and that sounds like that might work the best for me.
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Old 05-07-10, 01:04 PM   #8
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check either in the archives or run an advanced search with trochoid's name and some other related string. a thread is here somewhere, with photos.
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Old 05-07-10, 02:29 PM   #9
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check either in the archives or run an advanced search with trochoid's name and some other related string. a thread is here somewhere, with photos.

i found his "comparing the FI vs carb" and dispelling myths thread, but i'm still not finding anything about putting the s4 pump in the s3 tank.

i'll keep on searching, maybe he'll be able to post the link here.

but after seeing that the newer tanks have the removable plate on top, im sure he was talking about using one of those.

i was more talking using one of the older style tanks, but there are probably tons more carbed s3 tanks with the removable tops out there then SE ones, so if i can retro fit one of those, it would work just great for me.
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Old 05-07-10, 02:44 PM   #10
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I haven't done a writeup on modding a tank for the 2nd gen pump. From a technical aspect, it could be done on any 1st gen tank but I've only done the S3 tanks so far.
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Old 05-07-10, 07:24 PM   #11
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so you were doing it to the carbed tank with the removable top then?

if that's the case that makes sense then. just more of a "make the 2nd gen crap fit into the 1st gen" kind of thing.

did you add any of the extra sump cups to the carbed tank?

and then what years did the removable top tanks come in? were they only 84 and 85?

because when i parted out a 84, it had the old style of tank in it, but i guess it could have been swapped out at some time.

thanks for the info
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Old 05-07-10, 07:39 PM   #12
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Originally Posted by mellow65 View Post
I know there are people out there that have swapped their 1st gens to fuel injection. But I'm curious how they went about it with the gas tank.

Did you track down a gls-se tank or did you just use the carbed tank that was in there?

And if you just used the carbed tank was is just as simple as replacing the fuel pump with an aftermarket inline fuel injected pump and high pressure fuel line or was there more to it.

Also if you used the carbed tank, any concerns about the venting on the tank.

Any thoughts and input would be much appreciated
\


I stayed with the stock 12A tank in my `83 when I went to Haltech EFI. Replaced the fuel pump with a Bosch unit. Stayed with the stock fuel lines except for the fuel return line, which is now the same size as the delivery pipe. Running a Cartech Turbocharger kit & no problems with fuel delivery to this day.
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Old 05-07-10, 08:39 PM   #13
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\


I stayed with the stock 12A tank in my `83 when I went to Haltech EFI. Replaced the fuel pump with a Bosch unit. Stayed with the stock fuel lines except for the fuel return line, which is now the same size as the delivery pipe. Running a Cartech Turbocharger kit & no problems with fuel delivery to this day.
So you just put your bosch inline pump in your stock location?

that sure would make it easy

guess I would just need to keep it over a half a tank if I'm driving it hard.
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Old 05-07-10, 08:48 PM   #14
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Pulled the small fuel pump out & put the Bosch in its place. I also yanked out the fuel filter & put in a EFI one from Mazda. I don`t know why you would have to keep your tank half filled or more. I have run mine down so low that when the turbo kicked in, the car fell on its face from fuel starvation. That`s when I knew, I was running way too low on gas. BTW, I was sitting on E.
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Old 05-07-10, 09:45 PM   #15
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Pulled the small fuel pump out & put the Bosch in its place. I also yanked out the fuel filter & put in a EFI one from Mazda. I don`t know why you would have to keep your tank half filled or more. I have run mine down so low that when the turbo kicked in, the car fell on its face from fuel starvation. That`s when I knew, I was running way too low on gas. BTW, I was sitting on E.
I just have always heard horror stories of people having fuel starvation and blowing a seal due to detention.

Maybe I'm not giving these motors enough credit.
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Old 05-07-10, 09:45 PM
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