Some FMUs are adjustable, some are set. For example the standard Vortech FMUs are available in settings from 4:1 to 12:1, and they also have the Super FMU which is adjustable. The Australian supplier for Vortech FMUs is CAPA (www.capa.com.au).
As for the boost controller, that could be used to stop the rising rate at a certain point if you are getting too rich but I can't see too many cases where it would be needed.
i have a vortec fmu with a 6:1 disk in it at the moment but it is still getting far to rich.
i thought that if i could reduce the fuel presure a bit i could get rid of some fuel, and get some moor power. My mixture drops below 10:1
Might want to try a 4:1 disc but you would have to be careful it doesn't lean out too much, aim for 11.5:1 under boost for a safe tune. An adjustable Vortech super FMU would be a good option but they cost a lot and still it won't be a perfect. I would put that money towards an aftermarket ECU and decent injectors, then you can easily tune any point of the rev range and get the most power, drivability and reliability.
Or correct maf and injectors...Say 42 Lb and maf ...
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Thats the tendency with rising rate / fmu's they tend to dump too much fuel..You are better off letting the eec control fuel...
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easiest way, install a boost control valve in the vacuum line and bleed off some of the air pressure to the fmu. adjust it while your on the dyno.. good way to acurately get the mixture you want. i have a 12:1 disc in my vortech fmu and bleed off in this method.. not the greatest method but the cheapest.. the best ill agree (though dearer) is bigger injectors, recal maf, and adjustable reg on fuel rail.. which is my next upgrade..
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