Fuel Pump Duty Cycle

[obxdude018]

I am digging into this fuel issue of mine, I have two fuel pumps here one I received from Jeremy@S&H and one that I made myself. I am using 405 pumps. I have been having problems with the pump maxing out at WOT, I have contacted Bobby about this previously and Lito(who is doing the tuning) knows as well. I also have upgraded the fuel lines to -8 with the Fore Fuel Filter. Today I put the pump in that I bought directly from Fore Innovations and I received much better numbers however in both logs the pump hit .75 which if I remember correctly means there is an issue with the pump or wiring. At 5834 rpms, the fpdc read .442, which is good and bad, it's much higher than what I would like, however that is first time I have been able to make a complete pull without it maxing out.

 

[Fullboogie]

Well, .44 is not near maxed out - it's only 88% duty cycle. Depending on your combination, that may be just fine. I run 91% duty cycle on mine.

 

[obxdude018]

I am going to be lowering the boost down on it slightly, I was pegging 15psi on a stock block, ouch. However, I would think with the Fore Innovations fuel filter and -8 fuel hose and a pprv delete that number would be lower. I should be hearing back from Lito or Bobby shortly. However, I am still pondering the .75 reading as I know that is some type of issue.

 

[05yellowgt]

You are running pump gas or E85? I'd imagine you'd be much lower than that if running pump gas.

 

[obxdude018]

Yep 93

 

[702GT]

I had a similar problem with a Walbro 255 (brand new). The pump was maxing out way short. It ended up being a dead hole, the pump was dumping its life at the car because the tuner told it to. A wideband can't recognize raw fuel, so instead of showing an ultra rich condition it was showing lean because the wideband does recognize fresh air, which was being pumped via blower into a dead hole and into the exhaust, making the tuner think the car was lean so he kept adding more and more fuel until the pump was maxed out.

Hope this situation may help you out.

 

[05yellowgt]

what base pressure is being set in the tune?

 

[obxdude018]

To be honest, I am a complete noob when it comes to tuning, I know what to be careful of and look for and I understand what the PID's mean, however knowing what the base pressure is set to is past my radar.

 

[Fullboogie]

Are you logging on the laptop? You can log fuel pressure.

 

[Bobby]

I have been thinking about this for a wile. Did you look over everything in the hat to make sure there isn't a pin hole somewhere that was missed. I am just at a loss right now and wish I was there in person to look at this. Maybe then I could see what I am missing.

 

[obxdude018]

I have been thinking about this for a wile. Did you look over everything in the hat to make sure there isn't a pin hole somewhere that was missed. I am just at a loss right now and wish I was there in person to look at this. Maybe then I could see what I am missing.

This is what I did to try and rule any of that out, I took the walbro 405 and prefilter out of the hat that I received from Jeremy and did the mods to my old stock hat. Then I put the new pump I got from Fore into the hat I received from Jeremy and I got much better results. However once in each log it hit .75 which I can't exactly remember what that means when it does that.

 

[Mustangfan]

Sometimes when you log it will hit 75. It's just an anomalie. When I datalog, then do a sort there are always a few 75's in there. I think it's just an error I don't think because your seeing a few 75 pop up your maxing out your pumps. I am on rock solid tune with a max 84% duty cycle, I've had my car on dyno and had a couple tuners review my logs.