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Discussion Starter · #1 ·
Anybody ran dual walbros with stock fuel line + return? My single walbro cant keep up on long highway pulls and I want a quick fix for it. I think I leaned out slightly because of it and hit quite high EGT's. Gotta check my compression this week.

After all, isnt the 255l/h pump rated 500hp crank? I'm pushing more than that...
 

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i think the meth should help with you running lean up top.

Also, do you have a aftermarket fuel pressure gauge?
if the pressure is falling off, you know it won't be able to keep up.


I got a buddy who's building me a carbon fiber dual intank hanger, and he suggest just running a new braided line to the fuel rail.
 

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Krister said:
Anybody ran dual walbros with stock fuel line + return? My single walbro cant keep up on long highway pulls and I want a quick fix for it. I think I leaned out slightly because of it and hit quite high EGT's. Gotta check my compression this week.

After all, isnt the 255l/h pump rated 500hp crank? I'm pushing more than that...
one walbro is good to about 600 crank ponies.

as for stock fuel line. It will work. Just be aware that the pressure the pump itself see will be HIGHER by a larger margin then going with bigger fuel lines ;)

IE if the FPR show 50 psi with a stock line and walbro, the walbro will probably see about 52 psi at its outlet.
 

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If you still have the fuel pulsation dampener, eliminating that helps a lot.
 

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Moderator, l337 M0d3r4t0r
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I know, that the more pressure i turned up the less fuel I was getting as the pump was running out of steam... For instatnce running 22.8 PSI at 40 base pressure would cause me to barely go lean but if I went 50 base I actually ran leaner probably because the walbro can't flow enough fuel at that high pressure.

Walbro is good for 600 crank if you can keep the fuel pressures low enough but the problem with high base pressure and high boost is you get up to 80-90 PSI of fuel pressure.
 

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25psi = 14" brakes :)
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I'm in this same boat.
I just bought some 780cc Delphi injectors, and ordered a 255lph pump to supplement my Walbro 255lph. (Same pump rate, but it's the RX7 pump that is cheaper...)

Anyway, I'm debating to either add a return line in the middle and feed the rail on both ends. I still have the cold start injector, or I'd just use that hole.

Another option would be to enlarge the stock feed fitting size by tapping it larger, and then going to one feed that is fed by two fuel lines and put the Y fitting that joins them together just before the fuel rail...

To run another fuel line, I'm just going to use the existing vapor return hard line that is just capped off at this point. (I do not have a vapor canister anymore.) The more I think about this, the more I might just end up going this route.

Is there any possibility of one pump over powering the other, and burning themselves up if I combine the output of both into the one stock fuel line with a "Y" fitting inside the tank? I'd think that the stock line should flow plenty of fuel, and I'm going to replace the fuel filter too just to be sure it's not full of crud after so many years of use.

So what do you guys think?
Dual feeds from both ends of the rail with a center return?

Or will I be fine with two lines, a Y fitting and larger single end feed?

Or am I making a mountain out of a mole hill, and should just combine the pump outputs inside the tank, and leave my already upgraded feed line alone? (I've repalced the dampner with a AN fitting, and have no J tube, just the Areomotive AFPR and it dumps directly back to the return line now.)

This is my current setup line wise. I belive the feed is AN6.
 

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i think i'm just running a y block in the tank, feeding to one line all the way to the rail, then another y block into the stock rail.
Tapped for dual feed of course, and a single return in the middle.

I know most mk4 guys go this route, and it seems to work flawlessly.
A lot less headaches imo.
 

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Discussion Starter · #10 ·
ZaZZn said:
I know, that the more pressure i turned up the less fuel I was getting as the pump was running out of steam... For instatnce running 22.8 PSI at 40 base pressure would cause me to barely go lean but if I went 50 base I actually ran leaner probably because the walbro can't flow enough fuel at that high pressure.

Walbro is good for 600 crank if you can keep the fuel pressures low enough but the problem with high base pressure and high boost is you get up to 80-90 PSI of fuel pressure.
I have 30psi base pressure with the line hooked up.

Maby the leaning out was because of I had only a quarter a tank of fuel? Because I did several pulls to 150mph and no leaning out, but when I went to 175mph the car bogged up top and I checked my EGT's the peak was at 1100 celsius.. I glanced at the ZT-2 display every second or two, so it cant have been that high for a long time.
 

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Bosch -088

forget the walbros. yes the MKIV use them. Well they don't have metal gas tanks ;)
 

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Beats and Rhythm
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Krister,

Walboro's are not known for their longevity in life. Many of them do fail after a year or so of use (hard use like you are putting yours through). People may argue this but of course you must come to the conclusion that its a $100 fuel pump.

Of course your fuel lines may be a part, the stock lines are very small and its always a good idea to expand the size a little to ensure sufficient fuel delivery to the rail and injectors.

Your probably maxing the Walboro out, running dual pumps would help out alot taking the strain by half. But as stated earlier, you run into the stock line sizing.

-Jonathan
 

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Madd Tyte JDM yo ®
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if you plan to use a single feed line, you may want to do what i did.

i removed the stock soft line from where it connects to the factory hard line. the factory hard lne uses a metric inverted flare tube nut connection. i removed EVERY piece of factory fuel line between the factory hard line and the rail. i also removed the stock AFPR and Cold start injector setup and the J-tube.

first thing you need to do is cut the Female inverted flare off the factory soft feed line. cut it off flush w/ the female fitting. drill this out to 8mm ID. stock ID is 5.62mm IIRC. then, get a STEEL -6AN male fitting. braze this -6AN to the Female inverted flare that you just drilled out. 8mm ID is only about 2mm smaller than the -6AN you brazed onto this. however, if you drill out the Female inverted flare, you will not have enough of the flare to seal against the factory hard line when you reinstall the fitting.

you should now have a custom Inverted flare-to-6AN adaptor... soemthign i have not been able to find anywhere for sale. so now make a 28" long -6AN hose. use a straight -6AN female on one end (to connect to the new adaptor). then use a 90* -6AN hose end to meet the fuel rail. remove the stock feed line and FPD. this is a 14mm x 1.5 thread pitch.

actually, read my thread. i have pics and everything. this will allow you to get the MOST out of you factory fuel line and rail.
http://www.supraforums.com/forum/showthread.php?t=371814
 

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when this baby hits 88mph
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another option instead of the IV adapter is use a compression fitting.
 

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Madd Tyte JDM yo ®
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good point dave. ive never been a huge fan of the compression fittings. do they hold up to 100psi of fuel well?

do they ahve adaptors that go from compressoin to -6AN 37* flare seat?
 

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when this baby hits 88mph
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flubyux2 said:
good point dave. ive never been a huge fan of the compression fittings. do they hold up to 100psi of fuel well?

do they ahve adaptors that go from compressoin to -6AN 37* flare seat?
i havent tested them that high haha. ive never had any problems from mine, but no longer running that setup.

yes, thats the size that was used. it was a jic fitting, but still 37* seat. be careful not to get the 45* seat as i believe they make those too.
 

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Madd Tyte JDM yo ®
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yeah, the 45* seat is a standard flare. All JIC's are supposed to be 37* seat. and AN is just a common street name. JIC is the industry name as far as i can tell. i just go in and tell them -6 JIC everytime. JIC hose making typically involves LONG radius hose ends and teflon lined hose, not EPDM like AN hose. so while the ID of the JIC and AN hose is the same, the OD is different. so i found out that i couldnt get -6 JIC hose ends crimped to -6AN hose. weird quirks within the hose-making industry. im fortunate to have a local guy who is a complete guru when it comes to hoses-and-tubes (his shop's name :rofl: )

i probably wont be seeing any higher than 80psi, but overkill is a good thing sometimes. at some point, i may end up offing the stock hard line since its only equivalanet to a -5AN (5/16" ID)
 

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25psi Bliss
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I'm not a big fan of dual intank pumps, especially Walbro's. Why? Firstly, I wouldn't trust the reliability of the Walbros. (2) Once the vehicle's integrity is contngent on adequate fuel supply, and one single pump isn't sufficient, then the performance of each pump becomes tantamount. - So, if one fails, how will you know / detect it's failure before serious engine / performance issues arise?
My suggestion - (1) modify the fuel tank to accept a rear sump system, and plumb in an aftermarket external pump(s), or (2) get a single intank pump capable of supporting your performance goals.
 

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7m power
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the way i did mines is that i cut the rubber hose that comes out of the hardline and put a compression fitting and ran a -6 line from there to the rail
 
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