EFI tuning question
 

I'm just looking for multiple opinion on tuning a procharged 502 engine. What do most tuners consider a "safe" AFR? My boat is currently around 11.2-11.5 at WOT and leaving black residue all over the back of the boat and swim platform. Timing is conservative and shows no sign of detonation. EGTS are creeping up but I hear that EGTs are a thing of the past and not a good indiction on tuning a boat engine. I would like to lean this boat out a bit maybe around the 12.2 range or so at WOT. Running through the mid range I'm see AFR not under boost ranging from 13.2-14.0 but anything about 2500-3000 it starts dropping down and eventually leveling out to the 11.5 range.


Whats everyone opinion on this?


Boat info
25 Baja Outlaw
510ci BBC
GM aluminum heads
custom camshaft
80lb injectors
M1 procharger at 4-5psi
Aeromotive fuel system

Not that it's right, but I run 13.8 idle, 12.9 cruise, 12.0 wot.

To me your numbers sound about perfect. keep in mind that when you have a afr of 11.5-1 you may actually a cylinders as lean as 12.0 being they are all averaged. Has the cold start enrichment mode been defeated in your ECU? Most the time with prochargers the stat is removed, the engine runs around 100 degrees and efi won't come out of the cold start mode until its at 140 or higher stock , Smitty

I'm with Smitty. Your afr's aren't that bad. You could possibly lean it a little, but I wouldn't go crazy. It's certianly not enough to soot the transom. I would guess that the black you see is from oil. Are you still running the little metric rings? Is it consuming oil?

80 lb injectors are a little large for the setup and may make fine tuning a little tricky. They move a ton of fuel and can become very touchy, especially down low where the pulse width is so small.

As for egt's, you certainly need to take them into consideration. They are going to determine how much timing you can get away with. Add timing until the engine starts to just hit the knock sensor. By running "safe" timing numbers, you are elevating the egt's. That will actually make the engine more susceptable to hitting on the knock sensor. A little more timing will also help to lean the engine a touch. There is no set amount of timing. There are rules of thumb to start with, but every engine is different. The combustion chamber design, cam size, cylinder pressures, etc. will all determine how much timing it will like. That is the big advantage to putting it on the dyno. You can play with timing until the engine no longer responds with lower egt's and increased power while monitoring all 8 egt's.Generally speaking, those things will happen before it gets all over the knock sensor to badly.

What is the comp. ratio? How much boost?
Eddie

Engine isn't using any oil. the compression ration is 8.8 running 4-5lbs of boost.

that engine combo and aluminum heads,i'd be running at least 31 degs of timing,probably pick up 40-50hp on the top end.mid range timing i'd be at 34 degs.
i'd monitor the knock sensors and watch what there doing,if anything(good tuning).

What is the A/F ratio at idle?

13.2-13.8

Ok I had the boat out this weekend and watched the wideband a little closer. Air fuel ratio drops to 11.2-11.6 at WOT and stays around the 12.2 range out of boost. The boat continues to leave a soot on the back of the boat and swim platform. fuel pressure at idle is 43psi and climbs over 50 under throttle. I'm thinking of trying to take a couple more PSI of fuel pressure out at idle and hope it leans out up top. The boat at normal cruising without making boost leaves almost no residue on the boat. It only builds up under full throttle while making boost.

Also keep in mind that 11.2-11.6 afr is with only 3-4 psi of boost.

are you running a rising-rate fuel regulator that increases the pressure under boost?

yes

there will likely be a few chime in with that new information. I ran one myself and got rid of it 2yrs ago because I couldn't keep it consistent. What MEFI ecm are you running?

Mefi 3

you should be able to get rid of that regulator and tune into boost with the Mefi3. Fuel pressure remains constant and I bet your sooting issues disappear, unless you are seeing oil as Eddie mentioned before

I did notice this weekend that the valve cover vents to the intake of the blower. I might route that into a catch can and see if that helps.

that's a cheap vacuum pump and i doubt the cause of what you're seeing. if you're getting too much oil out of there you may have a blow-by problem

Let me ask you this...

does it soot on a run without going into boost? do you go into boost coming on plane?

Little to no soot not under boost. No boost getting onto plane.

one of the pros can chime in but I would bet the rate at which the regulator comes in under boost is very aggressive. That in itself may lead to the sooting problem since your afr seems to be good. I ran one from Bell Engineering and although it was a superior product compared to the one ProCharger supplies, it was very temperamental and a real pita to to keep tuned. Day to day weather changes would affect it so I went to mefi4 and did away with it altogether. I'd be interested in seeing your fuel map with the 80lb injectors.

So what should my target air fuel be? Think I would be ok bringing it up to 11.8-12.0?

That would be up to you. I run mine in that range but do not make extended runs at wot.

As mentioned, how long do you run at wot, if its for 10 seconds it will be fine, if its for 5 or 10 minutes you might want closer to mid 11's. Also, your cylinders may vary, one might be at 11.2 and one might be at 12.0, you are seeing a average of one side, if you do have a hot cyl and you lean it out too much you know what will happen. I have been running a blower motor in my boat for over 10 years, I have never melted one down yet but always set my afr's in mid 11's. Another point you made though was you are only running 3-4 psi of boost, if you decide to lean it down it will not be as much of a chance of meltdown with that low of boost. Drop your wot fuel pressure slightly until you see afr's a touch higher, stop and pull 5/7 plugs (the ones I think I remember hearing are lean the most) and see how they are looking , good luck, Smitty

I'm not a fan of changing fuel pressure to adjust AFRs. To me it's a global change / band aid. I like to get the base BPW/MAP tables set, then use the other global change tables to adjust AFRs as needed.

Ditch the rising rate regulator if you have it and do as Griswald mentioned.

For reference I run 12.5-12.8 WOT but on a N/A motor.

I too would be interested in seeing the fuel MAP with an 80 lb injector, specifically at or near idle / no load.