articfriends

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Back working on this since Thurs morning, beating head agaianst wall trying to get to root of different AFR's from batch A to batch B. Thurs swapped ALL batch A injector plugs to Batch B injectors and all batch B to batch A injectors, made pull, 3000 rpm's-2.5 to 3 afr points difference and it followed the harness so now 2,3,5,8 were 10.5 +/- .5 and 1,4,6,7 were mid 14's. Completely converted motor to a mefi4 harness, took a mefi4a ecu that has 4 hours on it, manually transferred all the data from a mefi3 to mefi4a (not easy, you have to open XDF file, open old tune, open new xdf file, open new tune, paste info then repeat, again, and again etc. Plugged ecu in, fired motor up, pulled to 3000, batch 2358 at 11.5, batch 1467 at 14.5 BUT once they reached 4200 they evened up and did NOT switch on top like mefi3 did, remained within .7 or so to 5800 rpms. BTW, motor made 560 hp and 580 ft lbs of tq like this, wtf, wtf, wtf! Flashed a SECOND mefi4a, made pull, same difference between batches.
Swapped injector leads from 5 to 7 and 7 to 5, made pull, cyl 7 and 8 within .5 afr top to bottom. Spoke with Bob at Mefi burn, spoke with Mr gadgets about what it would take to just fire ALL 8 injectors from same batch (desperation), external injector driver would be the answer triggered by one injector driver ciruit BUT all external injector drivers are built for low impedance injectors when I looked. At this point dumbfounded that 4 different ecu's and 3 different harnesses could all have similar problem. Turned off Knock sensor, made pull, no difference, turned off every sensor in programming and made pull after each change, no difference.

articfriends

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So Friday swapped everything BACK to mefi3, added fuel on lean batches to where safe , ignored rich batches for now, took the power back from 560 to 540 hp, runable but would have pig rich cylinders at certain speeds, fully intended on soldering both batches together and running off one injector driver, Bob at mefiburn said it would be a good experiment and should work BUT I envision boat getting hot and quitting/burning up ecu or injector driver while out on the water, not convinced it would be such a great idea. Tried uploading another mefi3 500 efi tune I have but it would get to 96% and error with Checksum error message.
Today I went to interior shop that has my 33 scarab with 500 efis, tore a 3rd mefi3 ecu off one of my motors, stuck it on dyno unmolested, motor went to 17-1 during a pull, found that odd since 500 has SMALLER injectors than this 502mpi. Cranked fuel pressure up to 75 psi since I really wanted to make apull with this ecu without changing tune at all. Made a pull, afr's were a little rich in some spots, a little lean in some spots BUT drum roll, THEY WERE ONLY .1 TO .7 POINTS APART, NOT 2.5 TO 3!!! So, do I have 4 bad ecu's?? NFW, won't buy that!
Opened up the stock 500 efi tune and current tune I been running on this 502, opened every flag, scalar and tables and compared. Found a flag called "staggered injection skip double fire" checked on 502 tune but NOT on 500 efi tune, also found "fuel detonation control enabled" flag set on 502 but NOT on 500 efi. Changed the flags on 502 tune on those two boxes to match the 500 efi tune, Swapped back to first mefi3 ecu I was
working with and flashed tune back in with these changes, made pull, motor went lean, good or bad at least SOMETHING changed. Cranked fuel pressure back up enough to make a pull without hurting the motor and bingo, afrs .2 to .7 or so apart, not 2.5 or 3 points. Not sure even what those 2 flags eaxctly do but they obviously screw with injectors banks in some way. Now motor has to be re-tuned BUT at least the afr's are even enough to finish, this has been a battle!!!

SB

iTrader: (1)

Interesting.....

I don't know Mefi programing, so the following is talking out loud to maybe help you think things out.

Looking into the Flag called "staggered injection skip double fire"

Staggered Injection is another term for bank to bank batch. So, that's easy to understand.
Staggered fires each group of injectors 1 time every crankshaft revolution. Therefore each injector fires 1 time every crank revolution.
TBI fires each injector 2 times every crankshaft revolution.

As we know, Mercruiser uses one of two systems on their motors , either MPI (staggered inection) or TBI (typically 2 injectors per motor).

Obviously the fuel strategies would be very different from each other. Including of which, tbi's are mounted on dual plane intake manifolds, where one plane typically needs different fueling than the other plane.

Would that explain the term ?

SB

iTrader: (1)

Man, tough to find info on the net...had to try all different search terms.

This should help, even though different ECU:
http://www.thirdgen.org/forums/v6/58...ngle-fire.html

articfriends

iTrader: (1)

Dont know though IF checking "staggered injection" (skip double fire ) turns it on or off, to further cloud things I looked thru every tune I have in my spare lap top at my wifes house this morning and this is what I saw:
Merc hp 500 efi tune from my new boat and customers fountain both have it turned off from factory
A factory ramjet 502 has it turned on (mefi4a)
A factory ramjet 350 has it turned on (mefi 4a)
my 650 hp 540 na tune has it turned on (mefi 4b)
my 1115 hp blower tune has it turned on (mefi 4a)
my 600 hp Pontiac 455 mefi 4a has it turned on (mefi 4a) derived from ramjet 502 base tune
a customers unlocked hp 500 innovation tune has it turned ( this is tune this 502's tune was based from since it allowed me to set rev limiter any where I wanted and merc hp 500 efi wouldn't let me get past 5700 no matter where I set it.
So not sure why, how or what its exactly for, why turning it off leaned my motor out 2-3 points BUT made afrs match (it was obviously adding fuel BUT not equally even though volt meter and oscilloscope showed BOTH batches identical)
Going to set the flag tomm for fuel detonation control enabled and make a pull and make sure it doesnt spread the afr's to ensure it IS this flag, will post what I find, Smitty

sutphen 30

your going to make me turn the toughbook on and look at all the tunes I have.my afrs are really tight on mine.

SB

iTrader: (1)

Alright - single fire mode is used when the ms is too low in double fire mode to control an injector at idle speeds.

articfriends

iTrader: (1)

You probably read the same stuff i did, i understand the concept and why you would do it, not sure if checking the flag makes it double fire or makes it skipit. What i DONT undetstand is why changing it one way or the other would make the fuel batches go 2.5 to 3 afr points apart on bottom and top?

SB

iTrader: (1)

Yeh, I know. A Main issue with researching that and other things is that all ECU's do things different to try to make it all work.

Example: Some of the ECU's when on single fire will switch back to double fire at some transition point. I had read where this transition point with a certain ECU was driving a few people nuts. Other ECU's on double fire would start to lose control of the injectors at certain higher rpms.

Also, some single fire set up's would have varying A/F ratios because of what the intake valve is doing while the injector is firing. The double fire would not run into this as much.


Unfortunately, unless someone has a clear answer, is to do what you are doing so that it does work, and then figure out what caused what and thus how it works. Doh !

As Yunik has said, if your results don't prove your theory, get another theory. LOL and Ugggh.

Again, I'm ust trying to brainstorm with you (not on your level with this ECU) and see if your brain locks on to something.

Edit in: And yeh, what the hell does 'skip' mean ? For ever ? Or for when, where, why , what ? Damn !

articfriends

iTrader: (1)

More testing, checked staggered fuel injection, skip double fire and re-pulled, instantly 3 afr points difference at 3k so its NOT fuel detonation control enabled, its definately the first. made pulls all day yesterday. Tune totally lean everywhere after checking turning this flag off. Talked to Bob at mefi burn, he wasnt 100% positive from what I got out of him IF it turned it on or off BUT the tune ended up needing 8-12% more PW everywhere to get afrs at target so I am of the mindset it turns double fire ON, the reason why is IF your ms at 5500 was 10 ms/100 map and it fired the injector twice theoretically injector would fire for 5ms twice BUT when you add in .the dead band of .9 or so ms you would end up with 1.8 ms of deadband which would make it act like setting the pw at 9.1ms or so, hence the need to change it from 10ms to 11 to get previous afr, at least thats my theory. Why it evens up the afr's that were so far apart, PFM, I just dont know!
Motor make about the same hp, 555 heat soaked but got into the 585 ftlbs of tq hot so it helped tq go a little higher, fine tuning today and doing some testing on a experimental hp 500 air cleaner, will post more when I have it, Smitty