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Discussion Starter #1 (Edited)
Will the AFM from a 2.5 Milano at least start / run a 3.0 Verde?

Need to do a quick test...
 

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An AFM from a 2.5? if so the answer is Yes. I ran with one on my 3L for a while and I did not notice much difference between it and the correct one.
 

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Can't be a difference between an AFM from a 3.0 and a 2.5.
 

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Can't be a difference between an AFM from a 3.0 and a 2.5.
They have different part numbers so presumably there is a difference but it was not noticeable to me when I drove the car.
 

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Come on there can't be any difference between a 3.0 & 2.5 Bosch system. Maybe the AFM is set one more sprocket? The displacement justifies no upgrades in the injection system. All parts work in both cars, I switched 2.5 to 3.0 & 3.0 to 2.5, ecu's, afm's you name it, and I've done this many times and there is "NO" difference. Part numbers, yea right?
 

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How about an AFM from an 85 BMW 325e? Looks physically the same. 2.7L displacement vs. 2.5L. My Milano Gold has a bit of a driveability funk, and I figured why not try the known good AFM out of the BMW? At least as a troubleshooting measure.
 

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Come on there can't be any difference between a 3.0 & 2.5 Bosch system. Maybe the AFM is set one more sprocket? The displacement justifies no upgrades in the injection system. All parts work in both cars, I switched 2.5 to 3.0 & 3.0 to 2.5, ecu's, afm's you name it, and I've done this many times and there is "NO" difference. Part numbers, yea right?
There are definitely differences, in both the fuel ECU and ignition control ECU.

In fact, you cannot even plug a 2.5 liter ignition control ECU into a 3.0 wiring harness as the connectors are not the same.

Here is what I know:

1) The "fuel cutoff" is at 5,800 rpm on a 3.0 fuel ECU and 6,300 rpm on a 2.5 liter fuel ECU.

2) The "spark cutoff" is at 6,300 rpm on a 3.0 Ignition ECU and 6,800 rpm on a 2.5 Ignition ECU. The 3.0 Ignition ECU was advertised as being "digital" and has a different connector.

3) The fuel maps are different, but it's not as simple as 3.0 being richer. I think the 3.0 is richer at lower rpms but the 2.5 is richer at the top end (as it has a to fuel for a higher limit).

It is true that you can swap the fuel ECUs and see very little difference in running the car in casual driving unless you have a wideband o2 sensor to keep a close eye on the mixture.
 

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I totality agree there are some differences, but most of the components are the same. We all adjust our AFM's for better performance, maybe we are just making them 3L AFM's by adjusting them ourselves. As far as the ecu, they are different, but a 2.5 system sure can run a 3.0 just fine. As far as the rev limiter altered EPROMS can be bought to fix that. I have 2 ecu's that came with GiGi and changed them and drove the car, of course the one that was altered performed better, but it wasn't huge. It more about the engine & drivetrain upgrades to me that make an impact in the performance. My 85 GTV-6 with a 2.5L is proof of that, and GiGi as well. I believe though the 85 with the 2.5 can beat GiGi. though I haven't driven her in 5 years.
 

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One resistor has to be changed to raise the rev limiter on the fuel ECU. I posted pictures and details a couple of years ago. The ignition module is more difficult. It uses a crystal controlled oscillator that controls both the rev limit and the advance curve. Tom Zat changed that in his modified ignition ECU.
You can get rid of the ignition rev limiter by shorting the input of the board to the output but you also have no advance curve. That may be OK for a race motor if you can get it started.
 
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