|
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 |
Originally Posted by Young Performance
(Post 3713196)
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 |
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?
|
Originally Posted by dynojetresearch
(Post 3713650)
what is the a/f ratio at idle?
|
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?
|
| All times are GMT -5. The time now is 07:22 AM. |
Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.