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Old 04-11-2014, 12:46 PM   #1
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Default Using MBC on low-psi actuator vs. stronger actuator

My current setup is to have two boost settings - low and high, using an EBC solenoid running off a switch in the cockpit as a switch between vacuum inputs to the actuator - low boost runs an unimpeded vac line which allows wastegate to run at its own setting (7 psi or so for the Greddy actuator), high boost has an in-line MBC which raises the boost to 11psi or so. I like this because I can run a lower-power setting that stresses everything less for non-competitive events.

So far, that's seemed to work pretty well. I do get a bit of boost drop near redline, but it hasn't been drastic..
I think I jacked up my existing wastegate actuator during motor re-installation, so I'm looking into replacement actuators. Wondering if there is a drawback to getting a low-psi actuator so that I can maintain my low-boost setup and just use MBC for the high boost vs. getting an actuator intended to hold slightly higher boost?

I like the 6 psi actuator from ATPTurbo: Wastegate Actuator 6 PSI : atpturbo.com I would fab a bracket and modify the rod to be adjustable and proper length. Just wondering if I'm leaving something on the table by going with this vs. a 10 psi actuator for example..

Thanks
-Ryan
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Old 04-11-2014, 01:15 PM   #2
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its always better to run a boost controller rather than trying to achieve desired pressure with a higher spring wg, because even higher sprung ones start cracking open at low pressures robbing you of the oh so glorious violent boost onset that makes us all giggle like school girls
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Old 04-11-2014, 01:38 PM   #3
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I've been thinking about this exact setup lately. I have an HKS 12 psi wastegate actuator that I picked up last time I was in Hiroshima, and I also have the same 6psi actuator linked above. The HKS is on the car at the moment because of the higher boost pressure, but looks pretty ratty.

Ryan, if you wind up doing this be sure to post how you feel about it, I'll be doing the same.
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Old 04-11-2014, 01:45 PM   #4
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Depends on the desired max boost. Weird **** starts to happen if you run boost pressures approaching or surpassing 2x spring pressure, as a rule.
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Old 04-11-2014, 01:56 PM   #5
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Originally Posted by concealer404 View Post
Depends on the desired max boost. Weird **** starts to happen if you run boost pressures approaching or surpassing 2x spring pressure, as a rule.
On single port actuators, once you start getting to twice the pressure the exhaust manifold pressure can be enough to force the wastegate flapper open even if you completely disconnected the vac line from the IWGA. This is a huge problem with EFRs on on cars that flow serious air because the wastegate flapper is HUGE. If you want to run an IWG on a roadrace/auto-x car where you care about more than full throttle but want to run ALLOFIT, low psi spring, 2 port actuator, 4 port boost controller. With that setup you can pretty much run unlimited boost even with like a 7psi acutator using the boost to hold the wastegate closed.
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Old 04-11-2014, 02:00 PM   #6
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Yeah that all sounds complicated. All i know is that Turbosmart specifically recommended that i don't go over 200% wastegate spring pressure.

And my own experiences trying to run ALLOFIT on a 7psi spring weren't great.
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Old 04-11-2014, 02:08 PM   #7
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Originally Posted by concealer404 View Post
Yeah that all sounds complicated. All i know is that Turbosmart specifically recommended that i don't go over 200% wastegate spring pressure.

And my own experiences trying to run ALLOFIT on a 7psi spring weren't great.
Its not complicated. If you bought a 2 port actuator and a 4 port boost controller you just connected it up with a little bit more vac tubing that you would a normal setup. And your wastegate doody cycles will be like half as much as anyone else for the same boost level.
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Old 04-11-2014, 02:22 PM   #8
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I run EWG and an EVC2.

New spring was like... a dollar. 21psi wastegate pressure FTW.
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Old 04-11-2014, 02:24 PM   #9
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Quote:
Originally Posted by concealer404 View Post
I run EWG and an EVC2.

New spring was like... a dollar. 21psi wastegate pressure FTW.
But then you cant command low pressure...
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Old 04-11-2014, 02:28 PM   #10
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But then you cant command low pressure...

That IS low pressure.
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Old 04-11-2014, 02:29 PM   #11
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That IS low pressure.
Why do you even have a throttle pedal then? might as well just have a button.
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Old 04-11-2014, 02:33 PM   #12
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Because manpants.
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Old 04-11-2014, 06:16 PM   #13
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Because manpants.
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