Help me figure this out
Help me figure this out Hey guys, here's the deal. I've been working on this project for a while now, and its finally running. As with any project, there's always some bugs to work out. And my last bug is this damn fuel system. It works fine for idle, part throttle cruise, but start getting even 1psi of boost and the fuel pressure starts falling fast.
Here's the setup,
Sumped stock tank
-10an feed thru inline filter to y-block
2- Walbro 255lph inline pumps to another y-block
(plumbed parallel to each other) (2nd pump will be hooked up on a Hobbs switch within a day or two)
-8an from y-block to another y-block before the rails
1 more inline filter between the two y-blocks
At the rails the y-block splits to feed each rail
Two -6an lines out of each rail to an Aeromotive Regulator
Single -6an return to the tank.
It holds pressure fine, even with only one pump running. I noticed the pressure drop with more throttle so I hooked up the 2nd pump. When I do that it only gives me about 5 minutes before the pumps start making all kinds of noises. This to me is cavatation. Nothing happens with idle or part throttle cruise conditions, but the fuel pressure still falls when I start getting into boost. Like from 43 to 23psi within a second or so.
Anyone have this happen to them? Or better yet, could anyone point out wtf's wrong with my setup?
BTW, the Aeromotive regulator is the -6an size with two inlets one outlet and I have the vacuum sourse routed to the intake.
Here's the setup,
Sumped stock tank
-10an feed thru inline filter to y-block
2- Walbro 255lph inline pumps to another y-block
(plumbed parallel to each other) (2nd pump will be hooked up on a Hobbs switch within a day or two)
-8an from y-block to another y-block before the rails
1 more inline filter between the two y-blocks
At the rails the y-block splits to feed each rail
Two -6an lines out of each rail to an Aeromotive Regulator
Single -6an return to the tank.
It holds pressure fine, even with only one pump running. I noticed the pressure drop with more throttle so I hooked up the 2nd pump. When I do that it only gives me about 5 minutes before the pumps start making all kinds of noises. This to me is cavatation. Nothing happens with idle or part throttle cruise conditions, but the fuel pressure still falls when I start getting into boost. Like from 43 to 23psi within a second or so.
Anyone have this happen to them? Or better yet, could anyone point out wtf's wrong with my setup?
BTW, the Aeromotive regulator is the -6an size with two inlets one outlet and I have the vacuum sourse routed to the intake.
Last edited by Fire67; Jun 6, 2006 at 08:51 AM.
Alright, removing the vacuum line netted me 5psi more base fuel pressure. And I can now get one more pound of boost before the fuel pressure starts falling.
So what Im seeing is that the fuel supply is fine untill I start getting into boost, then when those 60#ers start getting into more duty cycle the volume cant keep up.
I did the no-vacuum check with and without the 2nd pump on and just barely saw a difference in how much the fuel pressure drops. Without pump #2 it drops 20psi within a second, with pump #2 it drops about 15 right off the bat and then starts slowly falling to for the last 5psi.
So far Ive only brought this thing to about 2psi worth of boost @ approx 1/3 throttle. Which is exactly where the fuel pressure starts falling.
Im beginning to think one of my pumps is defective, so Im gonna run just pump #2 for another check. If it doesnt change anything I guess I should look elsewhere, but if it doesnt build even base pressure I'll know if the problem is with pump #2.
Any other suggestions would be greatly appreciated. Im at a loss right now as to what I should do.
So what Im seeing is that the fuel supply is fine untill I start getting into boost, then when those 60#ers start getting into more duty cycle the volume cant keep up.
I did the no-vacuum check with and without the 2nd pump on and just barely saw a difference in how much the fuel pressure drops. Without pump #2 it drops 20psi within a second, with pump #2 it drops about 15 right off the bat and then starts slowly falling to for the last 5psi.
So far Ive only brought this thing to about 2psi worth of boost @ approx 1/3 throttle. Which is exactly where the fuel pressure starts falling.
Im beginning to think one of my pumps is defective, so Im gonna run just pump #2 for another check. If it doesnt change anything I guess I should look elsewhere, but if it doesnt build even base pressure I'll know if the problem is with pump #2.
Any other suggestions would be greatly appreciated. Im at a loss right now as to what I should do.
Well, I spent a few hours yesterday going over everything and here's what I found...
Pump #2 has completely quit working, actually it was trying to work but made its last attempt for me as I was checking things over. It let out a loud few yelps and seized up. So with less than 300 miles on this pump, Id say its defective.
So Im going to order a new one, and I'll hook up this Hobbs switch with it when I get the pump.
So in a week or so I'll know if that was my problem or not. If not I'll be posting back up
Pump #2 has completely quit working, actually it was trying to work but made its last attempt for me as I was checking things over. It let out a loud few yelps and seized up. So with less than 300 miles on this pump, Id say its defective.
So Im going to order a new one, and I'll hook up this Hobbs switch with it when I get the pump.
So in a week or so I'll know if that was my problem or not. If not I'll be posting back up
Originally Posted by Fire67
Well, I spent a few hours yesterday going over everything and here's what I found...
Pump #2 has completely quit working, actually it was trying to work but made its last attempt for me as I was checking things over. It let out a loud few yelps and seized up. So with less than 300 miles on this pump, Id say its defective.
So Im going to order a new one, and I'll hook up this Hobbs switch with it when I get the pump.
So in a week or so I'll know if that was my problem or not. If not I'll be posting back up
Pump #2 has completely quit working, actually it was trying to work but made its last attempt for me as I was checking things over. It let out a loud few yelps and seized up. So with less than 300 miles on this pump, Id say its defective.
So Im going to order a new one, and I'll hook up this Hobbs switch with it when I get the pump.
So in a week or so I'll know if that was my problem or not. If not I'll be posting back up
How did you wire the pumps? Wire size?
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I hotwired them individually. I forgot to order a hobbs switch on time, so I had them both running continually at first. I noticed the pump noise got louder as the fuel got warmer after my first hour or so of driving the car, so since I was under break-in and had no plans to get into boost, I unplugged the 2nd one.
Now that break-in is just about wrapped up, I wanted to go into a little bit of boost to see how she feels. So naturally I reconnected the 2nd pump before hand, and got greeted with lots of noise after a few minutes and dropping fuel pressure the first time I tried leaning into it some.
When I got home last night, I disconnected the pump I had been running, and connected only the one in question. No FP at all, not even noise during the pump 'prime' time at key on.
Now that break-in is just about wrapped up, I wanted to go into a little bit of boost to see how she feels. So naturally I reconnected the 2nd pump before hand, and got greeted with lots of noise after a few minutes and dropping fuel pressure the first time I tried leaning into it some.
When I got home last night, I disconnected the pump I had been running, and connected only the one in question. No FP at all, not even noise during the pump 'prime' time at key on.
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Originally Posted by Nasty N8
Also your fuel line size is way to big for those pumps let alone just one. You will loose fuel pressure with too big of line as well.
Nate
Nate
Ive seen other 'similar' setups to mine with the same pumps and line sizes, thats why I went that route. Besides, at the time they were the only pumps besides Aeromotive that I could get flow charts for.
I wanted a big single but the A-1000 wasnt up to the task with the line pressures I need to run, and the Eliminator was just overkill. According to the flow charts I have on these Walbros, the pair should provide just over what I need for volume at my peak expected FP (boost reference)
I see your new pumps that you recently posted up about.. Have any flow charts for them?
Yeah, a -10 feed thru a fiter, to a y-block, and then -8an from the y-block to the pumps. Figure bigger would be better on that side of the pumps so there's no chance of starving them. I think I just got a bum pump!
About this Hobbs Switch, can I break the voltage feed for the pump with it? Or do I have to run wires to the rear mounted relay to break the trigger circuit?
It'd be much easier/nicer to just break the feed circuit up front so I can just run a short vacuum line to the switch.
About this Hobbs Switch, can I break the voltage feed for the pump with it? Or do I have to run wires to the rear mounted relay to break the trigger circuit?
It'd be much easier/nicer to just break the feed circuit up front so I can just run a short vacuum line to the switch.
Well, I got my new pump and Hobbs switch. I ended up wiring the hobbs switch to another relay to break the voltage feed circuit to the pump. And I just have one question about the switch itself.
Since it cant actuate the pump right at ZERO boost/vac... What are other HS users doing for the 'boost' signal.
I was thinking along the lines of how a FPR will lower FP with a vac signal, and how people get its boost reference signal from ahead of the TB to prevent this.
Im wondering, would hooking the HS to a similar signal that doesnt see vac. at all speed up the reaction of the switch?
Im worried that if I set the switch at .5psi (or whatever the lowest point possible is), that the time it takes for the pump to get going will have me seeing a low point in fuel delivery and therefore a lean point in the fuel curve.
Im also worried that the fraction of a second worth of vacuum between shifts will kick the pump off and on and also cause a lean point in fuel delivery.
What do you guys think? Am I just worrying about this stuff too much, or do I have a valid issue here?
Since it cant actuate the pump right at ZERO boost/vac... What are other HS users doing for the 'boost' signal.
I was thinking along the lines of how a FPR will lower FP with a vac signal, and how people get its boost reference signal from ahead of the TB to prevent this.
Im wondering, would hooking the HS to a similar signal that doesnt see vac. at all speed up the reaction of the switch?
Im worried that if I set the switch at .5psi (or whatever the lowest point possible is), that the time it takes for the pump to get going will have me seeing a low point in fuel delivery and therefore a lean point in the fuel curve.
Im also worried that the fraction of a second worth of vacuum between shifts will kick the pump off and on and also cause a lean point in fuel delivery.
What do you guys think? Am I just worrying about this stuff too much, or do I have a valid issue here?
Don't worry about super low boost activation....not enough hp produced there to warrant both pumps wide open. I set mine to activate at 4psi and it works fine at 700rwhp...no lean issues at all. If you want extra insurance, wire a connector in so you can bypass the hobbs at the track.
Thats a really good idea, didnt think of that.
My FP starts falling right at 1psi of boost without the 2nd pump, hence why Ive started worrying about this.
I'll hook up a connector for the track to bypass the hobbs, sounds like it would asssure no problems.
Thanks again!
My FP starts falling right at 1psi of boost without the 2nd pump, hence why Ive started worrying about this.
I'll hook up a connector for the track to bypass the hobbs, sounds like it would asssure no problems.
Thanks again!
