502 Efi - need for more speed
 

I'm running a 502 EFI in 24' outlaw. What does it take to get more speed?????

I'm running 66 to 68 PGS depending on conditions, but I've added EFI reprograming (more fuel), CMIs, Crane roller cam with lift of .544, Hardin Marine spark arrestor, prop labbed, etc. etc. and I may have gained 1/2 a MPH.?!?!?!?

I did check my fuel rail pressures, which ran 38# @ startup and steadily fell to 30# @ WOT --- Soooo I pulled apart the VST tank and cleaned the screen on the high pressure pump.

I then ran the boat and NO GAIN -- I did NOT check the pressures while running (this time) , but did so in frustration on the trailer on the ramp with lower unit in water.... and .... 38# at idle and up to 3,000 rpms ( I stopped @ 3,000 becuase without a load on the system I feared I could damage something).

Short of more cubes or a blower - what does a guy have to do??

MAV

Without a blower

Yeap - little to no gain over stock.

The original cam lost #8 exhaust - I replaced it with a crane roller cam & roller lifters.

MY cam is : Crane ...
13 HR 00078 duration .212 / .220
life @ .050 .543 / .564
lobe seperation of 114 deg.


Thoughts??? My pressure at speed and under load MAY still be down. I was just so frustrated on the water I didn't check it then - also my guage leaks during hook up - and I didn't feel like screwing with it - but after getting on the trailer - I couldn't leave with water without at least checking it there.

MAV

who mapped your ECM? sounds like they did not get a good calibration for you, did they tell you to run 38lbs? also what do your spark plugs look like after a run? are they white are they burning a nice tan/brown color? what is your ignition timing set at? and what kind of rpm's are you turning now on top end? maybe hitting the rev limit?

Maverick
 

Maverick1,
First off, I own a 24 Outlaw, you'll throw more money into this boat than what I believe they are worth to get that magic #. The 24 is a great "smaller" rough water boat. They as you know handle the rough real good for their size. The hull design is just not efficient for speed. I have a HP 500 in mine(+- 530hp) = low 70's. Check the post in Baja section & do a general search on the 24 Outlaw. One guy has almost a 1000hp in his & still has not hit 100mph. I am real happy with my Outlaw, but the fact is the hull is not efficient for flat out speed.
Good luck
PS try running a REV 4 prop made a huge difference. Also chat with Allan4 .

Sounds like fuel pressure is hurting you. It should not drop at WOT. In fact it should increase under load. I know the pumps used in the VST tanks don't flow much. That pump may just not be large enough. I've always replaced the VST system on the older engines I've modifed. Also, that cam is not going to give you any major increase over stock. The exhaust should wake it up a little. So, with your changes I would not expect more than 2-3 MPH anyway. Fix the fuel pressure before looking any where else for your problem

The camshaft is a real loser for a 502. I would think that it isn't as powerfull as the stock cam. How did you ever end up with it?
Dennis Moore

The cam choice was after over ten calls to the Crane Cams Tech line. I've since realized that duration around .223 / .234 would have made more sense.

My prop is a mirage 25 ( with a little work), rpms are 4,600 to 4750 depending on conditions.

How would you change the pump to get away from the VST tank???

MAV

p.s. - To everyone - thanks for the feedback!

Mav...You can switch it to the "cool fuel" arrangement Merc uses, or make up your own system. Install a fuel cooler and external pump. Route the return line through the cooler to the fuel seperator.

Formula....reprogramming the ECU increases the pulse width of the injectors, thereby richening the fuel mixture. Raising the fuel pressure further richens the mixture. However, raising the pressure does not increase volume. If the pump doesn't supply enough fuel volume, raising the pressure will hurt the condition. Also, raising the pressure effects the mixture accross the board, from idle to WOT. Reprogramming would normally only alter the fuel curve under load, leaving the idle alone. I normally don't mess with pressure if I reprogram, other than fine tuning.

I've tried two different mirage 23s and both gave me 5,000 rpms but no more speed and a poor mid-range.

Soooo, I've stuck with the 25.

next time out I'll check the pressure with the boat under load and see if my pressures are still dropping off as the rpms get up there.

MAV

the problem as several have already stated is the cam,,, you went smaller than stock 212/220 versus 224/224, hence, you have less power than before especially in the 4000-5000 range, the addition of CMI's and labbing the props probably gained you back what you lost from the cam so you broke even. The cam is your weak link now.

Mav, I agree the cam is not a good choice. But, if the fuel pressure is falling at WOT then the engine is leaning out and you're not even getting the full performance that is available with your setup.

Formula...the regulator controls fuel pressure by routing the excess fuel back to the tank. If the pressure is dropping at WOT, then there is no fuel being routed back to the tank since all available fuel is being used. You could raise the pressure to 60 PSI, but it would still drop to 30 if the pump cannot supply the volume required to maintain the pressure. To me that is a red flag. If you set the pressure at a point and it drops at WOT, then you don't have enough volume. Reprogramming the ECU to a greater pulse width would icrease the volume of fuel required. If the pump was already maxed out then it couldn't keep up and the pressure would drop. This could be what is happening. I know they use a different pump in the VST system that is VERY small and may not keep up.

One more question.

could my regulator have a problem?

The reason I ask is with the key on or idling the system will hold 38#.

But when I turn off the key the pressure will drop down over 2-3 seconds to 30# and hold there. ????

Thoughts??
MAV

Also, if the pump is lame ( I've already cleaned the screen/sock on the high pressure pickup in the VST tank) Is there an aftermarket pump that will fit in the VST tank??

fuel pump pressure
 

An electric fuel pump located in the VST pumps fuel to the fuel rail assembly. The pump is designed to provide fuel at a pressure greater that that required by the injectors. The pressure regulator part of the fule rail assembly regulates fuel pressure to the fuel injectors.
Unused fuel is returned to the VST....

Pressure should be 34-38 PSI and should hold steady when pump stops.

CHECKING REGUALTOR
 

Call us and we will fax you a system diagnostic sheet to check regulator

Dave

704-799-6666

Got the diag and will test.

I run the boat again and even though I've cleaned the filter/sock on the high pressure pump, pressure at idle is 38#, when shut off will hold 30#, running mid- range 34# and WOT pressure still drops to 30#!!!

WHat gives?????

regulator?? pump???

Help?

Really sounds like your fuel pump is falling on its face. I think I'd try adding a HP electric fuel pump in series with your current system.

An additional electric fuel pump will only fill the VST tank faster. It won't increase fuel rail pressure. I doubt that the VST tank is running dry. Fuel pressure dropping after shutting off the engine is a injector leak. It will run dirty for a few seconds on start up.

Plug off the return line to the VST tank (from the fuel rail) and run the fuel pump in the VST tank (jumper leads from the battery), don't start the engine.
With a pressure gauge on the fuel rail, it should have 60 PSI if it is good. Don't hold it there for very long or you will burn out the fuel pump. If it will put out 60 PSI the fuel pump is fine.

Reconnect the return line and run the fuel pump. Rail pressure should go up to approximately 38 PSI (engine not running, no leaky injectors).

If you add suction to the fuel pressure regulator, fuel rail pressure should drop to approximately 30 PSI (high manifold vacuum at idle closes down the regulator to 30 PSI fuel rail pressure).

38 and 30 PSI are not concrete numbers. Many engines test slightly lower and still run fine.

Dennis Moore

Dennis,
You don't think it's the factory fuel pump not supplying enough volume for his application? Sounds like it to me.

Short deration cam will creat more manifold vacume, right? Rag's

Dennis,

Thanks for the response. I've already run pressure with engine off and key on -->> 38#. Key off -->> system will hold 30# ALL of my #s are with vaccum line removed from regulator!! - so pressures should be max permitted by regulator.

Its running where the pressure drops to 30 that seems bad to me. Although, last saturday I ran the boat WOT and added positive pressure 5# (bicycle hand pump) to the regulator vaccum line - no change in performance --- so I guess more regulator resistance/pressure is of no help.

I'll try your suggestions.

Thanks.

MAV

PS Send me cost and address to get your BB chevy book. It's worth that cost to have you one the web.