Hey guys,

Did a search, some help but not much.

Just installed my Forge mbc today. Beautiful unit, and the install went well. After dialing it in, I got it to hold steady at 1.4 from roughly 3k to 5k, but after that it still seems to want to fall flat to 1.22 bar to redline. I installed the stiffer spring so that is not the issue. Do I need the JDM MR BOV in order to hold the boost better to redline?

 

It's been shown and verified that the stock turbo will taper no matter what.

Do a search and you'll see the data.

I thought that too.

I have the TurboSmart MBC.

That's just the way it is. All those people claiming they hold boost all the way to redline are spouting nonsense.

Put some load on the engine (4th gear pull) - let it spike to 21psi - this should hold 19~20 psi during the meaty part of your powerband.

 

You need a turboback exhaust. In my experience much of the taper was addressed by it. I still don't hold more than 20psi past 6k or so.

 

Try getting the Forge wastegate actuator with the red spring. I've heard that it will hold desired boost to rediline. I have the red spring but havn't been able to drive my car for a month because of a lack of a t-case. I'm getting one from Jon @ TRE and it should be in this week and I can let you know how it goes this weekend. If I forget to post just pm me.

-Dave

 

I am using our wastegate actuator with the red spring (19-24 PSI) and our Unos boost controller and my car holds 21.5 all the way to redline with the softer MBC spring with minimal adjustment! I can turn it up much higher if I wanted.

Each car will be different, and some may have slightly more taper than others, but the taper should be minimal at best.

Check to be sure that the MBC spring is seated on the adjustment base properly and that all of the hose connections are tight and possibly even use zip ties on them.

 

Anjapower: I have an Espelir DP, UR 3" HF, Espelir CB.

eve-slow: thanks, I would be interested in hearing how that goes

Mike: thanks for your time. The stiffer spring is seated properly as per your recommendation to make it wrap around the center piece and not just sit on it. All of the hoses are clamped down. I'll do a few more tests today and report my findings.

 

Did a few more trials today, mostly 3rd and 4th gear, under load.

During the heat today it held quite steady at 1.32-1.35 bar until 6k RPM, then fell flat, going to 1.25 then down to 1.18 right at 7k.