502 Mpi Problems???????
 

Ihave a 2000 502 mpi, installed new stainless marine exhust, vortec flame arrestor, and arizonia speed ecu and vortec flame arrestor. Here is the questions I changed the fuel pressure from whatever stock was to about 46lbs, and Iam getting water in the rear cylinder, has anyone else changed the pressure when they installed headers???? Ireally think 46lbs is a little much and that the rear cylinder is fouling out then it starts sucking water. Whent on the board before and no one knew what pressure was stock or what to set it to. Call arizona speed and vortec and both say about 46lbs to start and some may need up to 52lbs. If you installed headers and flame arrestor PLEASE let me know if you also had to change the pressure or if you left it stock. :confused:

stock is 43 psi, seems unlikely the change to 46 would foul out a cylinder seems more likely reversion from new headers or a gasket leak etc.

Basically for 30 more hp the engine needs that much more fuel.

Arizona speed and marine told me I was fine just doing the ecu

Oh I thought they told you to increase fuel preasure to since stock is 43 psi

"Call arizona speed and vortec and both say about 46lbs to start and some may need up to 52lbs"

I have the same set up as you do. Stainless marine exhaust, flame arrestors and ecu reprogram.
Arizona speed & marine told me that there should be no need to adjust the fuel pressure in the area I boat in which is 100' above sea level. They told me that at high altitude it is sometimes necessary to increase the fuel pressure. I never installed the regulator, I just verified that I had 43 lbs. on the stock one. I had a surge in speed when I shifted in and out of gear so Jim advised me to set the IAC's to 35 with the boat in gear. This solved the problem. I have never had reversion with stainless marine exhaust. I have installed 9 sets. I capped my Y pipes with 3"pvc plumbing caps and went straight out the transom. I don't know if you have captains call or not, but you could be getting some water sucked up from the Y pipe. I picked up 250 rpm with the add on's and 2.5 MPH. Good Luck

hi
 

have a 31 formula twin 502s did manifolds ecus vortech and regulators im running 50 psi no water you have other problems i gained 8mph on gps

Tommy V- Your results are stunning to say the least....now you should try the runner extensions and additional programming for another 8 mph gain.

I have straight exhust with no silent choice. Really wanted someones elses opinion. Ran the boat the first time and found water in the manifold, pulled the exhust on the one side where I found the water on the plugs, air tested both the riser and manifold, found no problems or leaks! Install the manifold ran the boat for a good hour pulled the plug and found no water. I'm thinking that I fixed the problem. Then I take the boat out this past weekend run the boat about 12 hours in three days pulled the plugs and found water again. Now i'm like what the f*** could this be. The only thing I found and I don't know if this matters is the riser clamp came a little loose? Checked all the bolts, (good) tighten the riser clamp and changed the plugs. Now I ran the boat at idle for about 2hrs (changed the oil 4 times) and found no water. I really appreciate all of your help, I needed to hear from someone else to see how theirs ran with the same set up. Does anyone really think that if the riser clamp came a little loose that it would cause reversion. (not loose enough to wiggle, but not as tight as the other side with no problems) Also have you guys with the same set as me ever tried the ac rapid fire plugs?

hi
 

liquiod lounge where do i get these runner extensions ???email me the info at [email protected]

Running a 97 502mag MPI with AC rapid fire plugs. No real performance gains noticed as I can tell but it does seem to idle better and help with black transom some.

i think the runner extensions are only used on the hp500 intake, but call Boost Power they sell all the kits and parts needed

forgot the # it is 805-376-6077 or www.boostpower.com

I don't want to be a purveyor of bad info here....sorry said it tongue in cheek.:rolleyes:

no problem smart a""es every where

Tommy- Not to offend and I'm not saying your not going 8 MPH faster, but it sure the hell isn't from the Vortec MPI kit. To be fair, the $50.00 adjustable fuel pressure regulator [best part of that $1000.00 kit] might be helping your SM manifolds add an optimistic 25HP per engine. In a 31 Formula [nice boat BTW] 50hp would be almost unoticable... 2 -3 MPH? Maybe if your lucky. What could be in that kit to give you the 120hp minimum to push that boat 8 MPH faster? Let's start with the highly acclaimed "billit" flame arrestor with claimed 35% increase in airflow: It dosen't matter if it flows 200% if the throttle body and motor can't pass it. I have taken my stock flame arrestor off , ran the boat and no difference. Additonal HP : about 0....no, I'll give it 5hp because it really does look cool. Next up The MSD Ignition Amplifier: Never proven to make more HP, some say cleaner transoms, better idle & tip-in; probably so. Additional HP: about 0. Next [and my personal favorite] "The Reprogrammed ECM" this mysterious and miserably programmed black finned box, just waiting for some wizard to tap all the horsepower lurking inside. Let's see what this does: after spending $1500.00 in reprogramming [2 from the Grand Wizard himself] I concluded it doesn't do ****. Granted these were on modified engines, but your fuel/air ratios that come in the little black box are fine as is. But you say now I got a 5400rpm rev limit.....thats fine but since your stock valve springs are approaching their limit a 5000rpm's
continuous, what good does this do you? How about the more agressive spark curve? You might get a little better acceleration and almost nothing on top. Additional HP: about 5....No 0! Because for most boaters, this is a scam! Next and last "Maxfow fuel Optimizer": The 50.00 secret of this 1000.00 kit. It allows you to make other small changes to you motor such as exhaust manifolds, SMALL cam increase,etc...it increases the regulated fuel pressure tomatch the increased air flow of the modification. Changes must be kept conservative or you will quickly run into expensive road blocks i.e.: throttle body, manifold,etc. Additional HP: Depends.

Let's add this up.....roughly 0 horsepower [give or take 10 to compensate for my personal bias]Oops, almost forgot, we got 25HP each engine from the less resrictive manifolds.

Tommy, let's say I believe your 8 MPH gain [I think I might]. Heres my theory: 50HP total from the manifolds, 140# less weight in your bildge from the manifolds...your boat might really like the slight change in CG also. The days when you compared top speed the conditions were suitable/unsuitable for speed, other weight in boat, etc. Were props changed? Going from a bad prop for your boat to an excellent prop for your boat could mean an 8MPH swing in itself. I just don't think It came from the EFI kit.

Hope you still don't think I'm a smart**s. I really want to earn "the Boater's Consumer Ombudsman" award. Take care, Berg:cool: