making vortech fmu adjustable
 

The fmu increases fuel pressure in direct relation to boost pressure. So if one could restrict pressure at the fmu input, it would modify this relation. IE the stock 12:1 ratio could be modified to 6:1 if one could restrict 50% of the pressure signal.

So my plan is to source and install an adjustable pressure reducing valve before the fmu signal input, effictively creating an arfpr.

Could there be any issues with the prv in vaccum? Anyone try this?

Assuming I can find an approprate prv, I'll give it a shot this weekend.

A simple restrictor isn't enough, you'll need a variable bleed after the restriction, kind of like the cheaper MBCs. Wouldn't this tend to produce a fairly non-linear response curve however?

You can buy "recalibration kits" direct from Vortech to alter the pressure ratio. Here's a link to their page: http://www.vortechsuperchargers.com/.../fuel_fmu.html

You could probaby use a needle valve with a one way check valve on the end. but it's way easier to buy a recalibration disc. Takes about 5 minutes to swap, and chances are you can do it mounted, at least I can.

my mbc works well with my afpr and keeps me from flooding the motor on the low end boost levels now that i have bigger injectors.

are you saying you have a boost controller plumbed into the vacuum source of your AFPR?

yes as of my walboro255 hp install on sunday night. all part of my trying to tune around the higher base fp. so far so good. + my boost is abut 1 lbs higher thanks to the lenght being away from the WG abit more.

eventualy i will get a nice electronic one to get even more control but for now my cheapo 10 dollar mbc does the job ok. a more controllable unit would be better. What would you recommend for the best control.

guess it would work. same idea as a needle valve.

A pressure reduce valve isn't a simple restrictor. It reduces pressure at a ratio IE it lets a determined portion of the pressure through and bleeds the rest. Maybe I've got the term wrong, but I think it's called a non sustaining pressure reducing valve.

A mbc would kind of "delay" the boost signal, probably creating a lean condition until it opens.

I didnt think of a needle valve. I think that it would produce a similar result as changing to a different disk. But an infinately adjustable valve would be better than changing out fixed ratio disks or needles... and I missed out on the FM BEGi's.

Plus, I don't have the disks I want, and can't get them before I go to the dyno Monday.

try the mbc if it works then use it if not you are only out some line and a vac tee

An electro-pneumatic transducer will translate a voltage or a current into a pressure. They are commonly used for spray control.