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Old 10-06-2006, 07:09 PM   #1
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Default 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.
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Old 10-06-2006, 07:29 PM   #2
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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
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Old 10-06-2006, 07:39 PM   #3
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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.

Last edited by Braineack; 10-06-2006 at 08:13 PM.
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Old 10-06-2006, 10:17 PM   #4
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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.
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Old 10-06-2006, 10:49 PM   #5
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are you saying you have a boost controller plumbed into the vacuum source of your AFPR?
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Old 10-06-2006, 10:58 PM   #6
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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.
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Old 10-06-2006, 11:02 PM   #7
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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.
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Old 10-06-2006, 11:16 PM   #8
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guess it would work. same idea as a needle valve.
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Old 10-07-2006, 01:14 AM   #9
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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.


Quote:
Originally Posted by Joe Perez View Post
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

Last edited by Ben; 10-07-2006 at 01:41 AM.
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Old 10-07-2006, 01:26 AM   #10
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Quote:
Originally Posted by braineack View Post
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.
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.
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Old 10-07-2006, 02:15 AM   #11
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try the mbc if it works then use it if not you are only out some line and a vac tee
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Old 10-07-2006, 02:16 AM   #12
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Quote:
Originally Posted by magnamx-5 View Post
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.
An electro-pneumatic transducer will translate a voltage or a current into a pressure. They are commonly used for spray control.
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