tomcat

You're talking to the right guy in Smitty.

Just a word about increasing fuel pressure. Flow will only increase in proportion to the square root of the pressure increase. Increasing fuel pressure from 45 psi to 65 psi only increases flow by 20%. That's not enough to keep up with most supercharging situations so you have to reprogram the ECU to increase pulse width anyway. I always recommend to buy bigger injectors and be done with it, especially if there are any plans for future upgrades.

articfriends

iTrader: (1)

These set-ups we are dealing with aren't quite perfect,the way your saying to do it would be ideal but in most cases would require a completely new ecu/computer and harness. Look at my set-up for example,I'm running a 2 bar map sensor and a mefi3 controller which is custom programmed to open injectors up close to their limit when I'm in the upper rpm ranges. The mefi 3 will only fire high impedance injectors,the biggest injectors that are high impedance are 63 lb per hr (which I have already switched to). At a steady state fuel pressure of lets say 45 or 50 psi with no boost referencing where the ecu takes care of the extra fuel demands by opening up the pulse width based on manifold pressure sensed by the map sensor I would need 96 lb per hour injectors to support the hp level I'm at. My ecu won't drive them. So instead of spending 2000$ dollars on a new computer,plus the bigger yet injectors plus harness,software and then programming and most likely a laptop too (which I don't own) I boost reference the fuel pressure when I go into boost and even go a step further and boost the fuel pump voltage at 5psi of manifold boost.Yes it is somewhat crude but it works pretty well once set-up properly. Now on the other hand just boosting the fuel pressure without re-programming the ecu and adding a 2 bar map sensor is really a crude way to add extra fuel and is inviting trouble but in some of these near stock applications running 5 psi of boost it can work although I have never believed it to be real safe. I'm not sure if you were aware of all of this so I posted it so maybe you could gain a better understanding of what we are trying to do,Smitty

articfriends

iTrader: (1)

I'm running the aeromotive eliminator pump myself,I was running a essex pump which was better than the original a1000 I started with. The aeromotive eliminator still couldn't keep up with what I'm doing thats why I added the kenne bell voltage booster. I could have went to a weldon pump or the aeromotive pro series but when I bought my eliminator pump aeromotive didn't have the voltage controller for the pro series yet which lowers the pump output when your not getting on it and talking to them they reccomended against using it in a continuos duty application plus I knew that the pro pump or the weldon pump would put out more than my regulators could bleed off when not in boost and I didn't want to replace and re-plumb everything AGAIN (I had just went from rubber hose to braided hose and bought new regulators).
On a side note-I use the stock fuel pump wires from the merc mpi harness to trigger a 50 amp bosch relay thats wired with 10 gauge wire directly to alternator/battery cables,don't make the mistake of trying to run ANY of these bigger pumps off the merc power because you will have a voltage drop and pressure loss,especially at WOT (this isn't necesarily directed towards ao-2600,this is just something I want to remind ANYONE following this thread who may also be doing something similar),Smitty

articfriends

iTrader: (1)

I love showing off the twin rail injector set-up I cobbled together so I couldn't resist posting yet again another pic of it-Smitty

BenPerfected

Smitty,
I am impressed with what you have accomplished with you EFI system. I have toyed with an offer of working with Keith Eickert on an EFI system on my set up, but know it won't be push button. Your system and hours of re-rigging and experimenting remind me why I am staying with a carburetor!

HARDCORE A/O

Thanks Smitty. I have actually completely re-wired my boat and I have a 30 amp relay with a dedicated 10 gauge supply to my pump. I have the relay triggered by the key switch so the pump comes on when the key is turned on. Trust me, I'm an old nitrous racer so I'm pretty anal about the fuel system!
You have highlighted though, the fact that with a blown EFI setup and, consequently, much higher fuel pressure than a blow-thru carb setup (say 45-65psi @WOT vs. 12-20psi @WOT), you are going to need a much bigger pump. This is so because pumps are rated at a certain flow at a certain psi- for eg. the A1000 is rated at 600lbs per hr. @45psi but the flow is without a doubt much higher than 600lb/hr at 20 psi. To illustrate my point, Aeromotive says this pump is good for 1100hp on a forced air carb motor but only 800hp on a forced air EFI motor. (This obviously is because of the difference in fuel delivery pressure, cause we all know that an EFI setup is more efficient with fuel!)
I haven't seen any issues with my A1000 as yet but admittedly I haven't even been able to hold the throttle down for too long because it runs right to the limiter at 6600 RPM so quick I have to back it off. I'm trying to get the right prop on the boat and I hope theEliminator will be big enough for me, since Aeromotive claims this is big eneough for 1500HP forced air carb motors (and 1100HP EFI blown motors).
All in all, I am very impressed with your setup but I couldn't agree more with what Benperfected is saying - after all the help and guidance that I've gotten over the years from you guys (Smitty and Tomcat in particular) I've finally got a carb setup that seems to produce a linear AFR throughout the RPM range, so I think I'll stick to it now rather than pull more hair out with an EFI setup!!

articfriends

iTrader: (1)

I assumed you had EFI,its great that you got a carb to work as good as you have as it is also quite a challenge with a blow thru system to get it right. Keep us posted on how it works out,Smitty

HPJunkie

Good Thread I just started using my LM 1 and so far so good. I cant wait to try a run , then Ill be like you guys ...Questions start flying!

HARDCORE A/O

Thanks Smitty. Weather looks good today so I might give it a run later and let you all know how it goes. When I get all the data I need I'm going to start a new thread on blow thru carb mods.
BTW:On the point I was making on fuel pressure vs. volume:
According to the info on Jegs website, the Eliminator Pump flows 800lbs/hr @ 45 psi and over 1,000lbs/hr @ 8 psi, so its easy to see how these pumps are more than sufficient for just about any carb motor.
HP: Good to hear you got the LM-1. These things are a godsend. I just bought the Innovate XD-16 Gauge, but I've just now discovered that I still need at least the LC-1 cable to connect it to the 18' extension cable I've got. I'll probably just buy the LM-1 RPM kit as well so that I can do just about anything I need. The good thing about the XD-16 is that it is an LED gauge which gives you better "real-time" visiblity of your AFR, cause we found it was hard to read of the LM-1 in the boat because the glare made it hard to read off the LCD display. Just another option to consider! Let us know how it goes.

Griswald

Took delivery of my newzed boat today.........couple of questions.

502MPI, M-1 Procharger with FMU, SX pump (not sure which model)

1. On the FMU - how should this thing be plumbed? On my motor, the top port went to the stock fuel pressure regulator and the bottom port was simply stuck into the inlet side of the procharger. This can't be right. Can someone tell me how they have theirs plumbed?

2. The motor is leaning out. Pump is currently wired to the factory harness and I plan on putting it on a dedicated ckt tomrrow. 30psi and as soon as you bring it off idle, fuel pressure drops to 27psi. Never goes up. Also noticed the battery voltage was 10.5 and doesn't appear the alternator is charging. I'm sure the pump isn't getting enough voltage. This could contribute to the low fuel pressure, couldn't it?