Is this right about my fuel and boost

[daltah]

I have my mbc set to 8psi and Im installing 440's now. As soon as I get my idle fuel pressure right like around 18psi or so is that all I need to do and then for every psi I raise the mbc to the sfmu will raise the fuel pressure with it?

 

[XMasta19]

kinda confused at what you're askin here...are you trying to say that you tune at 8psi, then turn the boost up higher and expect to still be tuned? it works the opposite way, tune for your highest setting, and the lower boost levels will be tuned in as well. meh, what am I talkin about...only time I went into double digit boost, I blew my motor

 

[napkinthief]

The sfmu raises pressure of the fuel based on the pressure inside the intake manifold. bascially, the pressure tightens up the internals of the sfmu, and creates pressure in the line, thus creating pressure increase in the fuel rail, thus, more injector power.

Your MBC should do nothing other than control your boost. your wg controls your max boost, while your mbc controls your minimum boost. the sfmu only controls fuel.

Yes turning up the mbc, from say 4-6 psi, the sfmu will notice there is extra psi in the intake manifold, via the vacuum hose that you should have tapped, and tighten up, resulting in the previous chain of events.

 

[XMasta19]

...mbc controls min boost? A boost controller is used to raise the boost level past the original setting of your wastegate. The point I was trying to make was that you can't just tune your fmu for 6psi for example, then turn the boost up to 10 or so and expect it to still work. You would have to change discs/springs etc I would think

XMasta19 for THE WINZ


EDIT: fyi - boost controller can only raise boost then lower back down...but never below wastegate setting

 

[XMasta19]

...thus the infamous wastegate mod

http://www.dsmtuner.com/forums/showthread.php?t=211040

 

[napkinthief]

I was pretty tired when I wrote that last night. A wastegate opens to release exhaust gases to control MAX boost. with the mbc, the mbc raises the max boost, not the minimum boost. Thanks for pointing that out X

I have a 12:1 fmu, so I beleive that is good to 12 psi. If I rebuild, I will toss it and go megasquirt, 1:1 afpr, and some nice 550s for 20 psi

 

[XMasta19]

I was pretty tired when I wrote that last night. A wastegate opens to release exhaust gases to control MAX boost. with the mbc, the mbc raises the max boost, not the minimum boost. Thanks for pointing that out X

I have a 12:1 fmu, so I beleive that is good to 12 psi. If I rebuild, I will toss it and go megasquirt, 1:1 afpr, and some nice 550s for 20 psi

please do not boost 12 pounds w/out a rebuild especially using a fmu

TRUST ME

 

[selmerguy]

please do not boost 12 pounds w/out a rebuild especially using a fmu

TRUST ME

Your 12:1 fmu with stock injectors is safe to about 8 psi not 12. I leaned out to a 13.3 afr hitting 10 psi with my fmu. That is not rich nough if you ask me.

 

[daltah]

Ok let me clear some things up. My block is fully built and the mbc raise the boost past the wastegate. My question was if my idle fuel pressure is fine with 440's at 8psi that all I need right? because if I raise the boost on my mbc the sfmu will raise the fuel pressure on its own correct?

 

[XMasta19]

you're askin the same thing still


so if you're tuned at 8psi, then u crank it up to 15 pounds...will it still be tuned?

 

[daltah]

yeah thats what Im asking

 

[selmerguy]

If you dont have a wideband and a way to log right now get one. That or a dyno is the only safe way to do what you are tring to do. If your 440s are tuned with a sfmu at 8 psi run 8 psi. Or log a little higher and see how your afr holds up. Work your way to 15 psi. You may have to change disks in your sfmu. The only way for you to konw for sure is to log it and see. It's not rocket science but there are to many variables for us to tell you if you are safe. Hope this helps.

 

[XMasta19]

hmm...I guess I didn't answer this post yesterday like an hr after you made it ?

 

[selmerguy]

hmm...I guess I didn't answer this post yesterday like an hr after you made it ?

.... Guess not x. Well some people need to hear from more than one person. I am like that too.