mefi4b vs mefi 3
#1
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mefi4b vs mefi 3
I'm hoping to go to the dyno fri at Crocketts,I have been using a mefi3 to run my injection until now,My new cam and valve train (thanks to RMbuilder) is expected to pull past 6000 rpm's. A mefi3 is not capable of supporting fuel tables or programming past 6000 rpm's,I recently bought a mefi 4b that I plan on using,is there any thing it won't do or will be a problem compared to my old ecm other than re-pinning some terminals in my harness? I have been told it will support fuel tables/programming well past where I need to run my motor,Smitty
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I purchased the 4b and the ingenious software from AZ Speed and the fuel table in the software goes to 9000. I didnt buy the 4b wiring harness so had to re-pin my MEFI 3 harness to work with the 4b (fun times).
Havn't run the boat yet since the change, but hope to this weekend. Also have a wideband and pyrometer to help tune while running.
Turned the key after getting everything wired and so far all seems to be ok as I have no codes and everything that happens with just the key on still worked. Will be starting on the hose before heading to the lake just to be sure.
I havent posted much here, but have gotten a ton of info from the site and hopefully can contribute some with this.
Havn't run the boat yet since the change, but hope to this weekend. Also have a wideband and pyrometer to help tune while running.
Turned the key after getting everything wired and so far all seems to be ok as I have no codes and everything that happens with just the key on still worked. Will be starting on the hose before heading to the lake just to be sure.
I havent posted much here, but have gotten a ton of info from the site and hopefully can contribute some with this.
#5
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The biggest diff is in the rpm range and boost amount. The mefi 3 is limited in boost and rpm (rpm 6300, boost app.14 psi), where as the limit in the mefi 4 is not an issue anymore since it is so high. (rpm 9000, boost app. 28 psi) If it is a supercharged motor, than you will have MUCH better control over the fuel curve with the 4 when under boost. The 3 only uses a multiplier to control injector times when under boost, where the 4 has seperate boost tables. Hope this helps, Eddie.
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The biggest diff is in the rpm range and boost amount. The mefi 3 is limited in boost and rpm (rpm 6300, boost app.14 psi), where as the limit in the mefi 4 is not an issue anymore since it is so high. (rpm 9000, boost app. 28 psi) If it is a supercharged motor, than you will have MUCH better control over the fuel curve with the 4 when under boost. The 3 only uses a multiplier to control injector times when under boost, where the 4 has seperate boost tables. Hope this helps, Eddie.
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I wish I had known the mefi3 could have went 6300 because we (me and Crockett) programmed mine to go 6000 on the dyno last time and I have been on rev limiter quite a few times. I would have had him take it to 6300,thanks again,Smitty
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You can set the rev limit to whatever you want in the MEFI 3 or any generation of the MEFI controllers. For example, the MEFI 1 spark table stops at 3600 rpm and the fuel table stops at 5200 rpm, yet you can run the engine much faster if you want, it will just use the last value at the top of the table.
Bob
Bob
Last edited by MEFIburn; 07-11-2007 at 08:44 PM.
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