Yes, I have experienced that 2-3# fluctuation. In my case I have traced it back to allowing the MBC to have too wide of an operating range between WG spring pressure and peak boost level.

Too little WG spring pressure will allow the flapper valve to lift up an down off its seat on the turbine housing. Thus, the fluctuation in boost level as the MBC tries to compensate and fight against exhaust gas pressures exiting the turbine bypass port. The WG spring is more effective at keeping the flapper valve on its seat than the MBC with its tiny diameter hoses ever could be. This of course is just a theory of mine. So, you can take it or leave it.

 

ok ill adjust it tomorrow. thanks for all your input.

read this though... on the stock WGA, I had zero fluctuation, just taper... and could hit 26+ psi on the "low boost" spring for my MBC.

I installed the Forge WGA, preloaded it, and with the low spring still in MBC, abd the MBC turned fully to lowest setting, I was seeing about 21psi. When turned up, max I could get was 24 psi out of the soft spring. I then swapped the spring, and the lowest I am at is 25/26 psi so to get to 27-28 there isnt really that much adjustment happening with the MBC.

 

As a practical matter, you can try different variations to try and find that "right" combo. For example, you could reinstall that stock actuator which had been doing an adequate job up until now and preload it a bit more. You could also try going back to the soft spring in your MBC.

 

the stock actuator had been preload maxed. and it wasnt doing an adequate job tapering massively so thats why i went this route.

ill play with it a bunch. with a big *** Koyo rad, **** gets hot and tight so I would love to do this adjustment as little as possible haha

 

I have the same setup as you as far as MBC and WGA and mine is set to 19psi without the mbc. Im running 35psi no problem. It starts tapering off to 30 at around 7k rpm.

 

weird. i wonder if my MBC is effed.

 

Personally, I am not too crazy about the Forge Unos. I use an el cheapo $70 MBC manufactured by Dejon. It has worked well for me over the past five years. If I had to purchase another MBC, I think I would get a Hallman unit. If I wanted to run 2 maps then I would get the Buschur dual MBC.

I think that maybe you should swap in a different MBC perhaps borrowed from a friend just to do a comparo on your Forge unit. Don't get me wrong I think that the Forge unit is a beautiful piece of kit.

 

i would rather it work right than look good.

 

I agree with you Brenner

 

I used to love my Forge WGA. I have three of them in fact. However, I now prefer the El Cheapo FP 18# HD WGA. Granted the Forge unit has slightly better resolution than the FP piece, but the FP WGA works fine for me.

In your case, with 28# peak boost, the FP 25# WGA would probably be a good choice. This is probably not what you want to hear though.

 

we will see what happens. i have a huge feeling now after all this talk it is the unos mbc.

i will swap to a friends hallman tomorrow see what happens. i dont have to run 28... ive been talking with my tuner about doing a lower boost higher timing tune instead, but to reach my goal, i was planning on running higer boost levels.

 

i just bought the forge wga hopefully it works for ok me

 

mollett, in some cases you'll need to cut about 3/8" of thread off the end of the actuator rod on the Forge VIII actuator so as to be able to reach the proper amount of WG spring preload.

 

Definitely, not a fun adjustment when the exhaust manifold is hot!

 

i think its for a 9 is that a problem (i just got a hta green and the fp v2 install kit) sorry about the newbie question