Manifold pressure restrictor

Hello all,

I have been looking for an manifold pressure restrictor fitting to put on the manifold pressure port of the engine in case anything breaks in the line or gauge I don't want the engine to run super rough. Garmin recommends using an Omega PS-8G pressure snubber on the manifold pressure gauge. Unfortunately I can't find any specifications on this particular unit as to temperature. It appears that it might be okay in this location but the Omega instructions recommend having the PS-8G located at the gauge. Has anyone used an Omega PS-8G attached to the engine?

https://www.omega.com/en-us/sensors...g-accessories/pressure-snubbers/p/PS-SNUBBERS


Thanks,

Bryan

I installed it on the firewall between the Van's manifold block (VA-168) and the Manifold pressure transducer (Kavlico).

I added one because I was seeing pulses in the MAP when the engine ran at or below 2400 RPM (IO-360-A1B6).

Cheers!

B

Snubber

Brian: just curious, what size hose do you have between the cylinder and the manifold block? Thanks

Don Broussard
RV9 Rebuild in Progress
57 Pacer

Could be as simple as a 1" aluminum rod OD same as hose ID, drilled a .040 hole through it. Cut the hose, slip in the restrictor & clamp it down.

cajunwings said:

Brian: just curious, what size hose do you have between the cylinder and the manifold block? Thanks

Don Broussard
RV9 Rebuild in Progress
57 Pacer

Click to expand...

Very similar to the VA-133 (steel braid over rubber, steel AN flare nuts on each end), but about 6" longer as I recall.

I ran it from the #3 cylinder primer port (see VMP kit install) parallel to the VA-133 along the top of the firewall recess to the manifold block.

McMaster-Carr snubbers

McMaster-Carr also has snubbers. Love that name!

https://www.mcmaster.com/snubbers/gauge-vibration-dampers/

You can safely use automotive vacuum line along with a brass barb fitting for the head. The amount of vacuum needed for a gauge or timing only needs a 1/8" ID vacuum line and no special fittings.

For the restriction, I used a -4 soft rivet cut off the head and drilled a .040 hole. Cut the vacuum line anywhere in the rise so any fuel in the line will flow back to the head. Mark the location so you can find it later if it needs cleaning.

I had the McMaster-Carr snubber recommended from VAF installed when my G3X was put in (just got it back last week). Garmin MAP sensor. While the MAP is rock-solid, it has a big delay in changing the reading after a power change. Any of you seen that? Could it be the snubber causing it?

MAP Lag..

I see a similar delay, and I'm using the Omega PS-8G snubber recommended by Garmin. I suppose that's to be expected.

Another option to reduce the pulses is to install a plenum or similar chamber upstream of the sensor -- I saw someone on the forums did that; need to find it, or drill & tap a hole into the intake plenum and use that as the pressure source.