MSefi.com read only forum (Jan.15,2018)

What can I do to use a MAP sensor on a twin cylinder engine that has uneven vacuum pulses unlike a multi-cylinder engine. A small vacuum tank to maintain and smooth vacuum? A restrictor in the vacuum line like I have to use when I use syncronizing mercury sticks?
I've heard this is a problem with some engines with alotta cam and overlap that don't make much vacuum at idle. They usually avoid the MAP from what I have read. It seems to me that a MAP is a good sensor to use if possible, no?

I would make a central tank or pocket like you said, and then get a signal out from there. Id its too noisy, I would thinnk adding a second tank would fliter out lot of pulses.


two lines in, one line between tanks, second tank, line to MAP
===(TANK)---------------------------------------(TANK)------------(map)

A small volume vessel, like a cheap, generic, 3/16" clear plastic fuel filter and a variable restrictor will work with applications like this. Small brass needle valves found at aquarium/pet shops work nicely. You need to increase the restirction just to the point of a fairly smooth MAP reading. I prefer to use this approach while experimenting with various MAP lag filter settings. The apps I apply this to are the Mazda rotaries; these have very violent intake tract excursions when running ITBs. Good success has been attained several times using the RC filtering approach detailed above.

-Mike

Thanks for the suggestion. The fuel filter will attach real easy as will the valve.