I have been fighting a battle with this thing for a while. I need all the help i can get.


So i got my 502 EFi (1994) rebuilt and added a side whipple. I also upgraded to a MEFI 3, roller Cam (stock cam was not a roller), rockers, valves, ditched the cool fuel and ran a adjustable fuel pressure regulator with return to the tanks. Also ditched the water pump and went with a crossover.


Once the engine was done i got it Tuned But The engine is still running very rich. My spark plugs are filled with Carbon. I think i found the problem but i could be wrong. The boat ran like crap at idle and smelled really bad like gas(like it was flooding) so i disconnected the injectors at the Supercharger rail. Once i did that about a minute of 2 later the boat was idling great! Now i ever went faster than idle because i know the blower needs them. I will add that i had all the injectors cleaned and serviced.


Here are my questions


1) Does anyone have experience with deleting the piggyback system? If so how do you do it?


2) is it possible to piggyback has the injectors stuck open? I heard of the computers going bad but i do you tell.


3) is there anything I can do to be sure those injectors are causing the problem?


4) My idle is around 1200rpm(its high), under the throttlebody there is a vacuum, when i put my finger on it the idle drops. Is there something that should be connected there?



I am currently not talking to the engine builder because of things that were stolen from my boat. So I am trying to figure it out myself before I take it to someone and throw another couple thousand.


any information is greatly appreciated!!!

You can delete the standalone. You wire one injector to any injector on bank 1 and the other to any injector on bank 2. You need to modify the fuel system. I have a side mount on a 502 myself and just did the fuel system over. Eddie Young @Young Performance Marine can fix you up!! give him a call.

Tim

Ive built several whipple sidemount mpis and tuned them both on my dyno and on the water. Yes as 941 mentioned, throw that aux computer in the trash so when it malfunctions one day you don't turn your pistons into ashtray's. There's two ways to wire the injectors, personally, Ive been tapping one into each bank as mentioned, running them all the time. I had a dyno customer, however, that did NOT like the idea that fuel could possibly puddle in the intake so he used a rpm activated window switch to power both of the auxiliary injectors (the ecu grounds them to fire them, they are normally powered all the time the motors running). We set the switch at 2400, a rpm he wont spend a lot of time at , of course in tune we had to reduce fueel signifigantly above the crossover point as his 2 extra injectors were 80 lb. Hope this helps, Smitty

When you say modify fuel system what do you mean? I did ditch the Cool fuel / VST and went with a Aeromotive Fuel pump and Adjustable regulator. My return runs back into the tank.

By tapping into the injectors, do you have any problems with how the boat runs at idle, does it run rich?

I honestly thing thats what is happening right now with my boat. It does feel like the fuel is puddling. Running the switch you installed and set to 2400 RPM wont the engine under 2400? I due drive the boat at idle a TON because I am asking because in Lake Havasu(Arizona) and it reaches temps around 115 during summer.

Besides that one customer with the switch, have any of the other motors you tapped into had any problems? I am thinking thats the route i am going to go.

The ecu will need to be tuned to run proper afr's as the two added injectors will fire with the factory eight injectors all the time. I ran the fuel system like this. My original setup had no added injectors. I added the two 80lb injectors in the throttle body and yes it was super rich. My ecu is on its way back from young should be here tomorrow. I will let you know how it goes.



Red is fuel supply arrows showing flow. Yellow is return.

Tim

Thanks Tim. That is pretty much the way mine is done. Except mine goes through the fuel rail first then to the supercharger. I had my fuel rail modified so it has a return on it.

and here for 11yrs I've never used the injectors at the throttlebody.I also have an mefi4b so controlling the fuel in boost is easy.

you guys need o2 bungs in your exhaust and then have it tuned on the water.you can tune via the mail(I'm doing that now w/ 1075's turned up to 1375hp),but you need to have an afr meter running and recording boost and rpm so the fuel curve can be dialed in.
I said if I had the program to tune the 555,I'd have it tuned in less than 30mins.

The ones where I ran extra injectors all the time would act like you picked up a little fuel from intake IF you free revved it after idling on dyno but we never noticed anything weird in boat, shutting them off at idle then turning them on and accounting for it in tune seemed to be "cleaner" overall, that customer hasnt put it in boat yet. no draw back to that i can see. Ive never used the aux computer on one but pretty sure they are off at idle too, Smitty