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Tech Specialist
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Discussion Starter #1
I recently came across a post here where the owner of a truck installed not 1 but 2 Walbro GSL 392 pumps.

http://www.cumminsforum.com/forum/3...o-gfs-392-install-pics-allot-information.html

He states:

Here is a pic with 1 pump installed, (most of you will probably need or want one pump) and also a pic with 2 pumps installed. Since this is a bypass* system, and my fueling mods aren’t that far down the road, I decided on installing 2 pumps now. For reference, 1 pump should supply about 75GPM at 0 psi. 2 Pumps should supply about 150 GPM at 0 psi. (There is a flow graph at the end of this install.)
Ummm.... everyone can do whatever they want, but a few things should be pointed out here.

1) Provided the '392 is getting a decent voltage (14V), it will be putting out 70 or so GPM at 15-20 PSI.

2) A 600 HP Cummins running a BSFC of 0.400 pounds per HP hour is using 240 pounds a fuel per hour. Diesel weighs 7 lbs per gallon, so 240/7 = 34 gallons per hour.

So even with the most extreme fueling mods, there is very little reason to be running 2 pumps. In fact it is complete overkill. This has actually been proved on several high power Cummins engines, some dynoing over 800HP on a single Walbro, keeping the fuel pressure over 15PSI when a suitable regulation system is used.

Just thought you might like to know.
 

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Tech Specialist
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Obviously, I disagree with you on your definition of "Overkill".

I'd at least think you would be happy to see someone doing this with Walbro pumps. You seem to be as enthused about them as I am.

Overkill for what?

Do you know what my HP and Torque goals are?

Do you know what the HP and Torque goals are for the people reading this?

I'll give you that 2 Walbro pumps will supply WAY more fuel than you can burn under say, 700 HP.

After that, I'm pretty much going to want to have that warm, fuzzy feeling only a lift pump (Or pumps) that deliver more fuel than my diesel could EVER burn give me, and I would think anyone else would want that comfort, too.

Matter of fact, I would want ALL the overkill I could get at 700+ HP, not just fuel delivery, because that's right about where stuff starts getting REALLY expensive when things go wrong!

Is it "Overkill" to spend an extra $130.00 for another pump, when you could be faced with thousands of dollars in CP3's?

To me, there's a big difference from the "paper" world of your calculations and the "Real" world, where Me, Dodge, Cummins, CP3, and MY Wallet live.

"Overkill"?
If I built everything with the minimum to accomplish the task, how reliable is it?

Please note, this is just an explanation of why I would want the "Overkill", and I'm not diputing the fact that 2 pumps or 150 GPH, (whatever) is more than necessary for under 700 HP.

It seems what you call "Overkill" I think of as "Insurance".

I guess another way to explain it would be "Levels of Comfort Factor".

Apparently, you'll run right up to the ragged edge of 800 HP on one Walbro pump. You have a high Level of comfort factor with that. You back that up with mathematics, etc. and it secures you in your foundation of comfort.

I think that is great.

However, For me to have that same level of comfort, I want more than I need. Too many times life in the world I live in has taught me that when you step up to the plate, you better not find anything lacking or it's gonna get expensive. If it costs a little extra to get a lot more insurance, I'm on board!

If I ever do come to terms with the 2 pumps is overkill at 150GPH, I can always take one off, having not done any damage, and just run 1.


I guess in closing I can say that you sir, do not define what is "Overkill" for me or anyone else but yourself.

Respectfully,
 

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Premium Member
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Just remember if we all did the same thing life would be boring...
 

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Tech Specialist
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No. Lloyd isn't sponsored. He just went to a different setup. At least he claims not to be sponsored. Why do you assume that since he switched that money was involved?
 

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Shiftin Fool
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from what i know about lloyd he isnt sponsored by anyone! or he doesnt lead on that he is.
 

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PA VP ONE TUFF O3
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sorry to change the subject motorracer057 please tell me thats your fourwheeler if so send some pics and specs of it

I dont really say there bashing just a heated argument and both of them have tons of good info

thats why i am hoping they can answer some of my questions i posted
 

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Tech Specialist
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Why do you assume that since he switched that money was involved?
I assume nothing.

I asked a question.

Thank you for the answer... I think.
 

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Tech Specialist
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would you need to bypasses if not i might try this set up if it would make the walbros live longer than adding the shim kit to them
You only need one bypass.

Also, I don't think running 2 of them instead of shims is going to improve longevity any, at least not that I'm aware.
 

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:popcorn::popcorn:
 

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Tech Specialist
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I assume nothing.

I asked a question.

Thank you for the answer... I think.
It was more the way you worded it that I was replying to. It seemed as if since he switched to a different fuel setup that money was instantly involved instead of lloyd maybe just wanting to try something. That's all.
 

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Tech Specialist
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2,117 Posts
what about getting the performance shim kit.
i mean if the bypass is set at 22 psi so wont it be letting fuel out at least with the shim kit you will beable to hold well not hold but 40+psi
Missed this one.
Sorry. :beer

I have the performance shim kit, but am not currently using anything out of it.

I don't think the CP3 likes to see an abundance of pressure on it's input side.

My current setup holds about 19 PSI at idle, and sucks down to just 17PSI at WOT, measured right at the input to the CP3. I'm actually happy with that.
 
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