Davepar
Well Known Member
As a big disclaimer, I haven't flown with this yet. It looks like it will work good, though.
I was in a quandry as to how to connect up everything that needs manifold pressure (MAP). There's a 1/8" pipe thread hole on the back of cylinder 3 that needs to connect to a MAP sensor (mine is from AFS) with a 1/4" tube fitting and two P-mags with 1/8" tube fittings. The P-mag can be run without MAP, but it won't alter the timing as aggressively and thus won't be as efficient.
The prior tried-and-true method of connection is the IE VMP install kit from Vans for $55. It uses a flexible hose from the cylinder to a firewall fitting and the sensor is thus aft of the firewall. That would be OK, except the P-mags are forward of the firewall. Either the hose needs to be cut or some other fitting attached forward of the firewall. I also had a preference for installing the sensor forward of the firewall and thus only a wire would need to go through the firewall.
Parts:
AN840-4D nipple, 1/8" pipe thread to 1/4" hose (Aircraft Spruce and others)
High-Temp Silicone Rubber Tubing, 1/4" Id, 1/2" Od, 1/8" Wall, Black (McMaster Carr part# 5236K882, $1.83/ft)
Polycarbonate Single-Barbed Tube Fitting Reducing Tee for 1/4" X 1/8" X 1/4" Tube Id (McMaster Carr part# 5117K33, $7.97 for pack of 10)
Polycarbonate Single-Barbed Tube Fitting Tee for 1/8" Tube Id (McMaster Carr part# 5117K13, $5.52 for pack of 10)
The P-mags included some 1/8" high-temp silicone rubber tube, but McMaster sells that as well if you need it. The T's come in packs of 10. If anybody near Seattle needs them, I have 9 spare sets available for one beer each.
I mounted the sensor on the front of the firewall. It's designed to be in a car engine compartment, so I see no problem with it being fw-fwd. The AN840 fitting goes in the cylinder. The 1/4" tubing goes from the AN840 to the MAP sensor via the 1/4" to 1/8" reducing T. The 1/8" tubing and T then connect to the two P-mags. The hose is very secure on the T's and P-mags. On the sensor, I might use a small hose clamp. Spruce sells a "Herbie" clamp that looks good for this. The P-mags came with some similar plastic clamps that I used on the P-mag fittings, although I doubt they are needed there.
The one remaining piece of the puzzle is flow restriction. The AN840 needs to be altered to limit the air flow. The sensors should even out the readings, but it's also a safety measure in case a hose fails. I decided to epoxy an AN426AD5-4 rivet into the engine side of the fitting with a 1/16" hole drilled in it. Another option might be to fill the non-engine side of the AN840 with JB-Weld or weld it shut and drill through that.
Dave
I was in a quandry as to how to connect up everything that needs manifold pressure (MAP). There's a 1/8" pipe thread hole on the back of cylinder 3 that needs to connect to a MAP sensor (mine is from AFS) with a 1/4" tube fitting and two P-mags with 1/8" tube fittings. The P-mag can be run without MAP, but it won't alter the timing as aggressively and thus won't be as efficient.
The prior tried-and-true method of connection is the IE VMP install kit from Vans for $55. It uses a flexible hose from the cylinder to a firewall fitting and the sensor is thus aft of the firewall. That would be OK, except the P-mags are forward of the firewall. Either the hose needs to be cut or some other fitting attached forward of the firewall. I also had a preference for installing the sensor forward of the firewall and thus only a wire would need to go through the firewall.
Parts:
AN840-4D nipple, 1/8" pipe thread to 1/4" hose (Aircraft Spruce and others)
High-Temp Silicone Rubber Tubing, 1/4" Id, 1/2" Od, 1/8" Wall, Black (McMaster Carr part# 5236K882, $1.83/ft)
Polycarbonate Single-Barbed Tube Fitting Reducing Tee for 1/4" X 1/8" X 1/4" Tube Id (McMaster Carr part# 5117K33, $7.97 for pack of 10)
Polycarbonate Single-Barbed Tube Fitting Tee for 1/8" Tube Id (McMaster Carr part# 5117K13, $5.52 for pack of 10)
The P-mags included some 1/8" high-temp silicone rubber tube, but McMaster sells that as well if you need it. The T's come in packs of 10. If anybody near Seattle needs them, I have 9 spare sets available for one beer each.
I mounted the sensor on the front of the firewall. It's designed to be in a car engine compartment, so I see no problem with it being fw-fwd. The AN840 fitting goes in the cylinder. The 1/4" tubing goes from the AN840 to the MAP sensor via the 1/4" to 1/8" reducing T. The 1/8" tubing and T then connect to the two P-mags. The hose is very secure on the T's and P-mags. On the sensor, I might use a small hose clamp. Spruce sells a "Herbie" clamp that looks good for this. The P-mags came with some similar plastic clamps that I used on the P-mag fittings, although I doubt they are needed there.
The one remaining piece of the puzzle is flow restriction. The AN840 needs to be altered to limit the air flow. The sensors should even out the readings, but it's also a safety measure in case a hose fails. I decided to epoxy an AN426AD5-4 rivet into the engine side of the fitting with a 1/16" hole drilled in it. Another option might be to fill the non-engine side of the AN840 with JB-Weld or weld it shut and drill through that.
Dave
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