merc mefi 3 question
 

Anyone know who can remap mefi 3 computer?

Thanks

to a stock tune or custom application ??

Need custom tune,mild cam put in and lower vacuum is screwing up idle.

try Jim at Ozaek Speed and Marine,

Just having an issue with your idle? Whats happening? Tuning the idle can be a pain in them, I went through a bunch of **** setting my idle up. And that has to be done in the boat

Mark Boos @ Precision Marine or Dustin Whipple if you try and do it by mail. You would be better off if you could find someone that could tune it on the engine and in the boat.

Can't tune idle unless they have the engine or boat. I bought tuning software and tuned the idle myself with direction from Bob Radke. Bob did my actual tune, but you have to see what the motor is doing at idle to see what corrections need to be made to make it idle right. You have to sync your throttle blade percentage with your tps voltage, and you have to adjust your butterflys to get your IAC counts in the correct range. When we installed my 502mag mpi in my old boat we had to completely redo the idle cause of how the map was vs where the new motor wanted to idle with the cam etc... Its not really that difficult, time consuming yes, and have to have a general understanding of what does what. Great example is if the idle is set to 700 in the ecm and you have the butterflys open to say have it at 800 it will hunt around to find 700rpms buy taking timing away, adding timing, etc..If you tell me what exactly its doing I may be able to help, and also if you have a scan tool you take IAC, TPS voltage, and TPS blade percentage reading as well to see what they are doing.

Thanks for the response
Have a running rich and hunting at idle problem only
after lots of time determined that map sensor voltage is too high due to lower vacuum at idle
also injector pulse with is higher at idle dumping more fuel, believed to be caused by the map sensor.
If i remove the map sensor and supply 15'' of vac. it idles perfect at 600.

What is your water temp sensor reading? and what is your fuel enrichment set at? Fuel enrichment is like a choke, so what it does is say it is programmed to run a thermostat, your fuel enrichment may be set at like 40C, and its a graduated scale. Your map sensor is the main component that your ecu determines what to do, all the other things like throttle percentage, water temp sensor, etc... make small changes. What LSA is the cam ground on?

I will be the black sheep here but I found idle to be the easiest to tune. Assuming you didn't make changes to linkage, sensors etc and have base timing set change the BPW to get the AFRs in line. Once that is done see what the IAC count is. If you have a two stage throttle body getting the IAC dialed in is cake. I adjusted the second stage about 1/8th turn and it brought the count down. The second stage doesn't affect the TPS sensor so no calibration or tweaking is required. The big CAVEAT is that you have a two stage throttle body with independent adjustment of both stages. Change ONE variable at a time.

I wouldn't touch the fuel enrichment table at first since its a global parameter.

Water temp sensor is working all other readings on the computer are fine set tps at .8v as per high end of specs
only thing off is the map sensor at idle volts are too high and also is injector pulse is high. which I believe is why it is loading up so bad at idle
Does anyone make a map sensor that has different values that may help? Someone suggested a v6 module

Trash thanks for the input but you are talking way over my knowledge, Always willing to learn, I don't know what a two stage throttle body is, but mine only has a butterfly a tps and a iac. my laptop reads the iac desired and iac actual and they match so i assume it is working properly

I grew up on holley carbs but am slowly learning efi

Thanks to all for taking the time to respond.

He is referring to the double blade throttle body, when you look at the throttle body there is 2 holes and each have a blade in them. the tps works directly off on of them, and the other you can adjust a certain amount with out it effecting the voltage. Voltage at .8 is to high, you want that voltage .6 maybe even a little under or a little over. You want your IAC counts at idle to be 0-10, but i found 8ish worked well. You can see the effects of everything if you watch your timing advance, and iac when its trying to idle. when it stumbles down you will see the IAC counts go up, that is the IAC opening to provide air to bring the idle up to where it wants it, along with some timing advance. Then when it surges up you will see the IAC counts start to come down, and the timing advance should go negative when bringing idle down. Pretty cool actually when you see it all work together. I have the software so I can watch it on the computer and have all the reading on 1 dash board. The V6 module is in the distributor. I am unsure if there is anything out there for a different value MAP sensor, and not sure I would do it if there was as thats the Pinnacle of what controls your air fuel mixture. Your fuel table is going to determine how much fuel to add based on your MAP reading (a few other readings 2 but this is the main reading it uses), so my suggestion is that it needs to be set up with 02's and have the fuel tables set up based on the map readings it is seeing.

What are your cam specs, in particular the LSA? this is very important in this scenario, as you may not have a fuel injection friendly cam and that is your whole issue. I ran a 588/596 lift, 236/242 duration on a 114LSA and had no issues with MAP readings. A buddy runs twin 502 mag set ups in his sonic, and has no issues with 620 lift cams with a little more duration then the one that was in mine and on a 114LSA.

Action, Sorry didn't mean to raise more questions but Ealesh33 answered them. You may have a single blade (single stage) throttle body which might make bringing the IAC count down slightly more involved, but NOT impossible. But first you need to get a wide band O2 on it to read the AFRs. Don't try to look at plugs. Once you have the wide band hooked up you will never go without it. Mine is installed in place of my fuel tank gauge! I run it continuously.

Anyhow, back to topic, many can tune the MEFI 3 or you can do it yourself. There are several in this forum who can do it. The choice is yours. I will also echo Ealesh33's cam advice, the wider LSAs tend to be more tolerant to EFI sensor inputs around idle, short answer they idle better. If you are rich or loading up at idle the wide band should show that, something likely in the 10-12.0 region would cause this. If I crank my BPW up so the idle AFR is 10-10.5 the motor sounds like a top fuel motor, IAC surges full throw etc. Trimming it back to the 12.5 (cold motor) to 13.8-14.0 (warm, no load idle) the IAC settles down to 0-10.

Hope this helps.

did you ever find out why the map reading was so hi?

I just saw this, sounds like it had 2 bar map sensor with ecu set to 1 bar, Smitty