well maybe just throw cheap mbc on there, that way it could open up at a set pressure and keep your max fuel pressure down while allowing more fuel pressure in the mid-range

 

wait that would work opposite? huh now i'm confused

 

yeah, opposite. I'm crossing my fingers a 8:1 or 10:1 disc will allow the pressure to build faster at low boost, keeping the low/mid AFR richer, then the pressure regulator should cap the max pressure to the rail keeping the upper AFR in check. But we'll see tomorrow.

 

Well I wasn't able to make it work to my likeings. I think the regulator failed on me, as it can't hold pressure anymore :(

 

Honestly, I am starting to wonder if those things are worth it at all, I had a heck of a time setting up my BEGI unit to do anything but drown the motor with fuel. It might make more sense to use the emanage to run a pair of honkin' big extra injectors.

 

Well the thing that sucks about the FMU is that its only adjustable on pressure. But you see the stock ECU tries to keep the engine lean before 4k so to combat that you have to dump fuel on it since the injector on time is short. Once the car hits 4k the Injector on time increases and then the engine gets all the fuel it needs, but then tends to run too rich up top. I was generally seeing about 12.5:1 AFR's under 4300 and then past that it would dip to about 10.5:1 AFR's.

 

I think this idea has merit, but maybe a different approach with the BEGI unit.

Basically we want to set the rate of rise and cap the upper limit. The rate of rise is already adjustable (technically) via the needle valve. What if we drilled and tapped another hole to accept another barb for 1/4" vacuum line. A the end of the barb we have a MBC and a check valve.

That way we don't modify the incomming amount of boost. Once we hit the target set by the MBC we vent the additional boost while still maintaing constant pressure on the FMU. This works for a wastegate, I don't see why this wouldn't work here. Basically you have an adjustable relief valve on the FMU.

Pick it apart, or tell me someone already thought of it!

Jay

 

Or just T the MBC into the vac/boost signal line so it starts to bleed boost at whatever threshold you want, could even T in a boost gauge to set it up.

 

that usually means you need a restrictor on the line. Corky can send you one.

 

My situation improved after I ditched the standard check valve for a larger brake booster check valve (it was relatively easy to blow through). I picked up a smaller internal diameter vac hose for the signal line I am going to mess with this weekend.