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Twin Walbro's :)

Matt Bachand

Matt Bachand

Depends on the 6.5
Messages
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22
Location
Worcester, MA
Since I have 2 Walbro's, and don't want to sell one due to the 1 in a million being me who had a failure, lets talk about plumbing them up.

In parallel, what would it do to fuel pressure?

What about in series?

Right now I have 5 - 6 before the IP, the flt mgr and racor are taking over 5. Filters are 8 months old and I suspect took a beating. Fuel pressure at water drain pegs out my 10psi handheld gauge fast. Anyhow....

Both pumps being after the racor, and before the primary filter, plumbed in parallel should split the racors resistance, and split the flt mgrs too?

What about in series?

The first walbro would take all the racors hit, but It would probably just make the 2nd walbro work easy until demand is called, then I can't see much benifit this way.

The other option is putting it in the engine bay, after the flt mgr, before the LP, but not sure if that is recommended for IP health? Can't see why it would hurt, unless the walbro came apart (there must be wear particles)... last chance screen on the IP??

Now that all my plumbing is fresh rubber, and I have the 2ndary walbro, this is free and fast... I would like 10psi going into my IP for some reason.

Turbine Doc, you have 2 pumps wired in parallel, walbro and heath HO I believe, what does your fuel pressure do at the IP different then when just running one or the other?
 
What about in series?

This will double the pressure. Pressure is referenced off the pump inlet. So feeding a pump 7 PSI will make 14 PSI on the outlet. Spring will not pop off till it sees 7 PSI difference from inlet. A pump failure becomes a restriction for the other pump. Trash coming from the 1st pump failing would ruin the 2nd pump.

2 pumps wired in parallel:

This is the only way to go.
 
If I'm not mistaken Tim only runs one pump at a time. The spare has a check valve so it can't flow back to the tank. He can supply power if the main pump fails. IMO running two, either in series or parallel is a waste of a pump. Running in parallel will double the flow, I'm not sure if the relief valves will allow the pressure to double in series.
 
It wont help overcome some of the pressure loss of the filters?

Waste of a pump could also be having it just sit there on my shelf....
 
I was hoping you would send it to me, then it's not wasted:D. You can PM me for my mailing address.:rolleyes5:

Unless your gauge shows less than 1 psi at WOT I wouldn't worry.
 
NVW said:
I was hoping you would send it to me, then it's not wasted:D. You can PM me for my mailing address.:rolleyes5:

Unless your gauge shows less than 1 psi at WOT I wouldn't worry.
Click to expand...

I'm not worried, Thats why this is the performance section! All the plumbing work got really easy now that the hardlines are gone.

Leo, you cheap bastard... open that wallet up already!:nono:

A check valve at the end of each Walbro is ideal. Would keep it primed.
 
Sounds like more of a filter problem ? I can easily make 13 psi with a Holley blue pump and it has a internal regulator that can be adjusted,do you know what psi and gph the Walbro is rated at,I know they make some pretty huge gasoline ones.
 
Supposedly 10-12 psi 65 GPH.

These have a spring stiffness controlles the pressure. Pretty good design, only 3 parts inside, flow on fail.

When installed was with fresh set of filters, so I'm basing the PSI on that. 5 - 6 is good, but I would like more. When climbing steep highway grades it will drop down to 2 or so. I want it to have more when its working its hardest.

I think it was a tad higher when filters were fresh, but I'll wait till it hits 1 to change em out. My needle doesn't even budge below 5 80% of driving..

So in parallel the pressure probably wouldn't drop at all, just stay very close to 5-6.
 
You could have cavitation in in front of the pump if your pre filter is too tight and or clogged,a clogged filter after the pump shouldn't change pressure at idle,just full throttle,I would also adjust the spring. I don't have filters in front of any of my pumps,good for flow but you take a chance on the pump. I struggled with cavitation for a long time on a gas 305 vortec that I converted to a inline pump,it had a pre filter, but this wasn't the problem,there was a restrictive check valve in the Airtex plastic canister,about a 1/16 inch hole,after drilling and removing this the pump went from very loud to very quiet. Also the truck ran a lot better.
 
I dont think youre going to get any more than 10psi out of it either way, since it stops pumping when it hits 10psi. But either way you put them will be more reliable and be able to sustain your 10psi better.

If they are in series and the second has 10psi behind it, it just wont do anything, it wont draw any current until the pressure in front of it drops below 10psi then it will kick in.

if they are in parallel will pretty much trade off doing the work.

I also have two of them, an extra on the shelf.
 
Perhaps fixing the restriction is the way to solve this 2 PSI with a single pump.

Specific to going WOT and loosing pressure...
The relief is closed on the pump if you are down to 2 PSI across the pump. You need more fuel flow to keep the pressure high. In parallel gives you the flow to keep 10-12 PSI. It also adds a fail over pump.

Now if you are measuring after a filter then a restricted filter could cause the pressure drop at higher flow rates. More pressure from series pumps could implode the filter. Pressure can also over come the restrictions like 1/4 fuel lines etc.

I can't see a 6.5 going through 65 GPH. So I suspect something is restricting flow. You need pressure to get fuel through a restriction and this would be series pumps. Unless you have vapor lock from a restriction/air leak before the pumps. This has to be fixed as no amount of pumps can overcome that. But 20-24 PSI to the IP... can the vent wire take it?

The fuel tank stocking or a gravel screen is enough for before the pump. The trade off for restriction before an electric pump is not worth it. Restrictive fine particle filters on the pressure side of the pump. Electric pumps don't suck. Push like crazy but can't hardly pull fuel from the tank. This is why we have the in tank gasoline pumps. Ye old mechanical engine driven pump could really suck though and eat all kinds of trash no problem. If it wasn't for vapor lock...

Think of the pumps like batteries. You get amps/flow or pressure/volts.

http://www.rx7club.com/forum/showthread.php?t=815860

http://www.thinkauto.com/electricfuelpumps.htm
 
I dont know if the Walbro will run higher in series, they dead head at 10-12psi, so you cant get more than that out of them. I dont know if the input is 10psi if they then dead head at 20psi. I guess that would be a good test. If the differential tips some switch then yes, but if its only on backpressure then no.

The factory fuel filter manager is the restriction, drops a few psi, so you can measure 10psi before the filter and Walbro isnt working hard because on the other side of the filter its only 7psi. Because the filter causes the pump to dead head it doesnt push a proportianal amount more fuel when pressure on the other side goes down where there is more flow. I removed the heater coil inside the filter manager and it helped some. Not the heater itself, just the spiral coil that really clogs the fuel input shaft.

To get more pressure to IP, need a pump that outputs more pressure.
 
I honestly notice great pulling and responsiveness today after FTB. Sustained 5-6 PSI fuel pressure is noticieable to me in seat of the pants power. In fact, it shifted harder a few times, and I caught myself doing 70 climbing a very steep highway grade, and the killer is I was only pushing 7 boost. Usually Keeping boost at or under 9 limits my MPH's...

I dont' understand it, nothing changed, but doing FTB. I honestly didn't expect any performance gain, but trust me its pulling like a bastard all of a sudden... I'm honestly going to fast for the roads, feathering the pedal as I always have. Its not placebo either. Throttle is snappier.

This leads me to believe that there are WOT gains keeping pressure high. I think you don't have enough pressure at 2psi.

I havn't read any where else that people noticed gains, so I didn't expect anything. Maybe because I'm always heavy, without a trailer and I drive this so much I can pick up subte differences? An empty pickup truck may not notice as easily, and by the time you load up a trailer there is enough of a change there to throw things off. I'm inching towards 10k, @ 9750 last time I "emptied" out. No trailer, so its no trailer hitching weight, same ol heavy truck.


This makes me want 5+ PSi at Heavy Throttle, which means I need 10 or so at IP at idle. Not buying a raptor.
 
Only running 1 pump at at time, did not install check valves since both pumps operate at same pressure more or less, I run the Walbro most of the time, the Heath h/o is my back up pump in case the walbro dies on me. Plumbed & wired in parallel, power to each comes from a dedicated relay, controlled by OPS/PCM signal
 
Matt Bachand said:
I dont' understand it, nothing changed, but doing FTB. I honestly didn't expect any performance gain, but trust me its pulling like a bastard all of a sudden... I'm honestly going to fast for the roads, feathering the pedal as I always have. Its not placebo either. Throttle is snappier.

This leads me to believe that there are WOT gains keeping pressure high. I think you don't have enough pressure at 2psi.

I havn't read any where else that people noticed gains, so I didn't expect anything. Maybe because I'm always heavy, without a trailer and I drive this so much I can pick up subte differences? An empty pickup truck may not notice as easily, and by the time you load up a trailer there is enough of a change there to throw things off. I'm inching towards 10k, @ 9750 last time I "emptied" out. No trailer, so its no trailer hitching weight, same ol heavy truck.




This makes me want 5+ PSi at Heavy Throttle, which means I need 10 or so at IP at idle. Not buying a raptor.
Click to expand...


Matt my boy, you know that discussion gpm(cfm :D) in another thread applies here also.

As far as nobody mentioning power gains, when I invented the FTB concept at the other site I made mention of the improved grunt several times but got beat up "it can't add any power" so figured it wasn't worth mentioning again.

My tests were backed up with readings of stalled or non increasing EGT at WOT with heavy load on engine at grade, max rpm of 2700 rpm and 800F post turbo EGT.

Once I did FTB same grade, and I was easily capable of 3000+ rpm same grade, and 1000+F attained. IP needs 1-2 psi at all times, more is better, to a point.

FWIW Bill's LSR ran Bonneville with one of my FTB fittings, I had wanted him to get some dyno #s from it, he just went ahead and installed it, how much Hp gain did it add, marginal probably, but FTB does allow the IP to use all the maximum fuel available from the lift, it's gph that does the work not psi.

The 4 holes as original sized in the inlet fitting were sized for a 185 Hp flywheel rating as was everything else on the engine, start pushing beyond that you have to up the ante on all the support systems as well including fuel, or you will be power limited.

Tim
 
I knew it would allow you more fuel when you exhausted supply, but figured I'd never push that hard to benefit. I was/am surprised by the added grunt at normal driving RPM's.

Are checkvalves plumbing supply?

The factory FFM is probably only rated for very low GPH that is probably the limiting factor here....

Installing 2 would just be silly, and putting a small racor up there somewhere may do nice.... then there is the heater issue.....

Maybe Mr walbro will just end up back on its shelf.....
 
Matt Bachand said:
Are checkvalves plumbing supply?
Click to expand...

In the size and low setting we would need I could not find one at an affordable price anywhere, saw several that would work in hydraulic and medical supply web sites tat could work but were very high $$$, you could cob one together from plumbing parts, but it would look like bride of Frakenstein by time you got all the fittings necked down to 1/4" tube.

I've not blown the check element out of my OEM style lift yet, I've been running almost 3 years now with the parallel pumps, key IMO that keeps it from doing damage is that the Walbro operates in the same pressures as the OEM pump does at idle when brand new.
 
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