502 EFI with side whipple help needed
 

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.
https://cimg4.ibsrv.net/gimg/www.off...e29264c348.jpg

https://cimg6.ibsrv.net/gimg/www.off...9c36773b1c.jpg
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

what kind of IAT's are you seeing? On the ones I dynoed with extra injectors the BSFCS even with "good" afrs everwhere kinda sucked (mid .650s to low ,700s at wot), that was tuned for 12.0 or so at beginning of boost and into mid 11.5s at top at 8 or 10 lbs of boost

so upgrading to a Mefi4b I can delete the injectors at the throttlebody? I removed the throttlebody today and inside the supercharger I had raw fuel piling up.

my understanding is those injectors helped “cool” The whipple?

I would post some pictures but apparently I don’t have 10 posts yet so I am not able too

A mefi4b wouldn't change whether or not you choose to add fuel at throttle body, it would, however allow you to have a "cleaner" tune overall. In a boat application their are 3 reasons a mefi4b is better than a mefi 3:
Spark/fuel tables end at 6000 rpms in a mefi3 , they go to 9000 on a 4b, so IF you want to build a motor that runs past 6k with a mefi3, you have to put whatever you want from 6000 up in AT 6 k and it is what it is.
Boost multiplier table, a mefi3 can be configured to use a 2 bar map sensor BUT the boost/fuel multiplier table ends at 150 kpa (7.35 lbs of boost) AND is 1 dimensional, ie, if you add 20% fuel at 140 kpa, its adding 20% any time it sees 140 kpa, whether its at 3000,5000 or 6000. A 4b table is RPM vs Boost , it can be set to add 10% at 140 at 3000, 14% at 140 at 4000 etc PLUS it goes to 200 KPA so it can taylor fuel multiplier all the way to 14.7 lbs of boost.
Spark vs boost table is same way
So if you NEED to add different amounts of fuel on a mefi3 under boost at different rpms, you have to do it in the100 kpa box in regular fuel tables. Problem with that is IF your not actually IN boost, that extra fuel you put in is still going to be there. Its npot terrible, Ive tuned some boosted mefi3 stuff that ran fine, just alot easier using a 4 and tailoring the fuel where it wants and needs it. Mefi4 does alot of other things too, but these are the big ones , Smitty

Got it. I might actually upgrade just to be on the safe side and get a better tune for better performance. Let me ask you this, are you still tuning MEFI3? If so what would you say about me mailing it to you(if thats possible) My motor basically has been refreshed and I did go with a roller cam. I had a guy tune it here in Havasu. He is the only person in all of Havasu that has the cable to tune MEFI3 (every shop i called has said the same thing, her is the only one that tunes Mefi 3). He did not build my motor but I had him turn it on the water. I do you have a welded bung And we did run a meter while tuning. Since he has to do it is still running very rich and I told him. Even while tuning at high RPM the boat sputters. It’s to a point where now it is doing it at Low RPM.

I talked to the gentlemen that tuned it and he is telling me to check timing, ignition coil(changed, spark plugs(changed), fuel Pump (brand new Aeromotive), fuel pressure regulator (new). It seems like he doesn’t want to turn it again or fix it. One thing that I do know is when we were on the water he did not check timing. He is making it seem like his Tune was spot on.

Update:

So I take out piggyback and wiring. Looks like the gentleman that built my motor did wire the injectors to bank one and bank two. But he still managed to connect the piggyback and wire it all up. DONT KNOW WHY!!

The gentleman that refreshed my motor and I are not on speaking terms so I did not know or wanted to ask him. It’s a long story!

The piggy back should be separate from the engine injectors..mefi3 or 4 can run 5 high impedance injectors per driver, there are two drives in the mefi3 and mefi4.

so are you saying you are firing the auxillary injectors off your 2 batches AND have the piggy back whipple computer? Are you sure your not looking at the TPS and IAC extensions running from your harness out to your TB?\

I am not using the piggy back at all. My boat never had it. I wired this two injectors in myself, one to each bank.
https://cimg7.ibsrv.net/gimg/www.off...67dd831aa.jpeg

Correct. So what he did was wire (taped into) both Aux injectors to the #5 and #7 injectors. When i took off the plenum i seen the injector connector that comes from the piggyback harness zip tied and Not connected. The TPS and IAC extensions were there but for time reason he tapped into those wires and they were connected to the piggyback harness. It was a complete disaster.

i am trying to post pics but unfortunately it will not let me. I just don’t understand why the piggyback was wired and he tapped into other wires.

With the piggyback being wired and the injector plug not connect (because he tapped into the 2 batches) throw off the MEFI when they were trying to Tune?

That is how mine was wired. Look at my previous response to Articfriends. This guy had a mess in the harness.

in the pic you sent of your fuel lines. The last pic have a read air filter. Is that for your vent hose?

https://cimg6.ibsrv.net/gimg/www.off...01db185e10.png


That blue wire was tapped into the TPS extension and was running into the Piggyback harness.

you can also see i am holding the IAC extension, the purple and White wire were tapped into that extension and connected to the piggyback harness as well.

Yes that hose and filter are for my IAC vent. I believe the piggy back is wired that way so it can do its thing. I have the install pdf I can email you like.


Tim

nothing that bothered me.,my set up is far from stock.all the openings in the air flow thru the intercooler were opened up and smoothed out big time.most boost I see w/ the smallest pulleys are about 4.5-5psi.eventually I'll go to a 9-9.25" crank pulley.

I have a PDF, thanks for the offer. I just need to get the tuning right now. I took out the piggyback and got it all cleaned up. Here is a look at my spark plugs. This was after about 2 hours at just idle.
And i did end up switching plugs to a NGK

https://cimg8.ibsrv.net/gimg/www.off...e48a34bdae.png

So oit sounds like the piggy back was abandoned and injectors wired in, it was just never removed. It really WOULDNT affect the mefi tune, your tuner would just be tuning off the tailpipe readings yielded by the 10 injectors is all. Were his afr targets extremly rich? One mistake I have seen is IF somone put a crossover on and engine temp varies BUT they never blended out the ect table above 100 degrees it could make you run rich. Lets say it WAS 112 out, water was 90 degees, engine was running 140 or 150, he tuned for a target of lets say 11.5-1 under boost. Now, your running the boat BUT waters still "cold" compared to normal, motors running at 100 degrees, the ect table would richen it up by adding un-needed fuel. just a possibility, Smitty

Great Point! That is something i have always wondered about with the crossover. In Havasu the water in currently still cold and when he tuned it last year it was in August and water was alot warmer. Also, Havasu is connected to the river in which the river water is ALWAYS colder.

Hey Tim,

I would love to have a copy of the pdf. I can PM you my email address.

Thanks!

sent!

zzzzzzzzz