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-   -   Limiting boost without changing pulleys (https://www.miataturbo.net/supercharger-discussion-38/limiting-boost-without-changing-pulleys-16674/)

oreo 02-15-2008 10:44 PM


How about restricting the air before the SC
one of my winter projects, is to try to integrate a drive by wire throttle body before my standard throttle body.

the megasquirt has boost control targets related to engine rpm and throttle position. it outputs a pwm output based on initial settings, but will modify the pwm output if the boost is higher or lower than the target.

the throttle body, has a motor with a spring on it, and 2 pots (like a tps) which provide position information.

I am working on a small uP to convert the pwm to position.

I originally considered the blow off valve, or the possibility of controlling the sc bypass valve. Either way is fairly complicated, and I figured I would have a better chance of success with the controlability of a throttle body.

In my case, I have room for an additional throttle body, and have purchased a rather large one, since I don't want to restrict the intake in any way.

RacingGreen 02-16-2008 04:26 PM

Do you have an M45 with an external bypass block?

If so, you could simply turn the screw which presents the stopping point for the flapper plate a few times.

This ways, you can prevent the bypass from closing completly and you'll get al lower boost.

No additional parts needed except a screwdriver

oreo 03-29-2008 11:21 AM


simply turn the screw which presents the stopping point for the flapper plate a few times
This ways, you can prevent the bypass from closing completely and you'll get al lower boost
I don't think this will reduce the boost in a linear fashion. I think you will reduce your low rpm boost greatly, and your upper rpm boost by a smaller amount.

my car has a quite small diameter bypass, and when I wire it open, at high rpms, I still get about 5psi boost, while at low rpms where I normally get good numbers, practically nothing.

still will work though...

patsmx5 03-31-2008 03:39 PM

I'm planing to put EBC on my dual SC setup. I have bypass valves that will open (recirculating the compressor and killing boost) with either vacuum or boost. I plan to use a line from the charge pipes(they will always be under boost) and run that to the boost solenoid, then T off to each bypass valve. My question is would I need dual solenoids more than likely or would be just the same as if I only had one bypass to operate?

IcantDo55 03-31-2008 08:58 PM

Shawn, I don't know if you know Joe C. or not but he is trying something on his SC vette that might intrest you.

http://www.tidewaterracing.com/forum...threadid=32465

He's a great guy and alway up for car conversations.


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