Having a hard time keeping my engines idling when shifting into gear, throttle position is at 0% when closed, moves almost immediately when opened, AFR is around 14:1 nuetral, 12.5:1 in gear. Motors have some decent cams in them, idle around 900-950 rpm and the steps are almost 0 in neutral. This is a MEFI 1 system, anyone have any tips on idle gain settings or anything?

You should be able to advance the timing enough @ idle to tame those cam a bit...the boats doesnt need any power up to 1400 rpm...a bit like the guys running a v6 module in there v8's. I have not been in mefi1 but im sure the timing tables can be modified. Just use a vacuum gauge and advance the timing to obtain the highest manifold vacuum level at the lowest engine speed

I have advance idle correct already in place up to 10 degrees, and it drops around there. I am looking for a certain scaler if people are changing to help out the drop in rpm when it falls in gear.

Take it to 18/20 as long as it runs smooth and and tames the pulses that's all that counts.....then re adjust back around 1400 rpm. I am talking about burning a new tune not adjusting the timing at idle on your existing tune...So when you start the engine she advances immeditaley to say 15 degree's then as the engine approaches 1400 rpm she will retard back to normal timing or what ever curve you desire.

http://www.masterenginetuner.com/ls-big-cam-idle.html


f you have the air/fuel ratio set properly and your engine can idle somewhat decently, even if it's by holding the throttle pedal down off closed-throttle to keep the engine from stalling, you can begin by setting a ball-park ignition advance value. For mild cams, an idle ignition timing advance of approximately 16-18 degrees will do. For medium cams, try within the range of 18-22 degrees of advance. Wild, lumpy cams may require 24-30

There really isn't much definition in these tables to be doing much more of what I have already done in the tables other than just having it rich most of the time, if you are familiar with MEFI 1 system, you would know what I mean.

Ive only played with 3 i guess a call to OBD would be in order

Need more info. What year was the motor / MEFI combo prior to modification? What is the motor? Big block? Small block? Iron Duke 4?

What are the current modifications (I need everything, all the data)

What cam specs? What is your IAC counts at idle no load / neutral?

900-950 is pretty high. What out drive?

1996 I think 502.

Stock 502 with custom Erson roller cam, roller rockers, , valve springs, Stainless marine dry exhaust.

If I recall correctly, cam specs are 244,[email protected], 114 LSA.

IAC counts no load is under 10.

Bravo 1 running 5 blade labbed Maximus.

Do you need to run the idle that high with dry exhaust?

Does it stall immediately when put in gear or surge then stall? What are you idle no load kPa/rpm values and in gear idle kPa/rpm values for BPW and advance?

What base timing is set and does that match what is in your tune?

Sorry for all the questions but I'm trying to narrow down which avenue to go. FWIW I've never tweaked any scalar or constant for any transient modifiers as I never had the need too.

Will it stall with a different (smaller pitch/diameter) prop?

That cam duration is huge for a marine 502 engine. Engine probably needs to spin 6000rpms to make peak hp with it.