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

Is there a limit on how long the vac line to the MAP sensor can be? I am looking at about a 12' through from manifold to the MS2 unit.

Thanks

Adam

12 feet???

That is a long way! If I needed to run that kind of distance I would use a hard line. (ie tubing instead of hose) I would also think that a vacuum line that long would tend to buffer the vacuum signal and might cause some issues with MAP response. Just a thought though.....

I imagine one of the experts will chime in here if I am wrong.

Ken

Bruce once tested this with a very long length, probably 10'-20', don't remember the exact length but and he had no problem with response. So its worth a try. I agree about the hard line, if it were mine, but Bruce used reg vac line. In fact if it were mine I would desolder the map sensr and run 3 wires from the box to the manifold. You can just leave the sensor tie wrapped in the wire harness, just tape the electrical connections.

Thanks for your replys. I will give it a shot with reg vacu lines (thatsa what I have on hand) and see what happens.

I am converting from MAF to MAP. How does a MAP work with boost? I am running a Eaton SC putting out about 7psi.

Thanks

Adam

FWIW, I like Al's suggestion for making the sensor 'remote' and running wire instead of hose, pipe etc.

Just 3 wires..... can be very small gauge..... easy to route....

Just curious, is this in a boat?

Ken

kjones6039 wrote:FWIW, I like Al's suggestion for making the sensor 'remote' and running wire instead of hose, pipe etc.

Just 3 wires..... can be very small gauge..... easy to route....

Just curious, is this in a boat?

Ken

No it's for a car, 1993 Ford Taurus. My dash/glove box/engine bay is full so I have the MS2 mounted to a sheet of aluminum that divides the passenger compartment from the trunk (no back seat).

Will try the tube first, if it does not work I will remove the sensor and mount it in the engine bay next to my boost sensor.

I am posting this incase anyone else ever has the same/similar question: It is for the MS 1 with V2.2 board but I am sure it is the same for all MS units.

"Don't worry about how long your MAP sensor vacuum hose is. Intuitively it seems that shorter should be better. However, a few people have done tests to see how bad the effect of a long hose was on vacuum signal propagation. With a ~100 foot (~30 meters) coil of rubber tubing in between the MegaSquirt® and the engine, the result was that no delay was apparent. This was with about a 10 millisecond resolution clock. The reason for this is that air has so little inertia that it moves very quickly in response to a vacuum (this is how we fill the cylinders, after all!)."

The above was found at the following link: http://www.megamanual.com/v22manual/mwire.htm

It is at the very bottom of the MAP Sensor section.

Thanks everyone!

Adam

My concern is that the line may become pinched or that the tube may be puncher over time. I am mounting it on my relay enclosure and running the wires in my db37 loom.

Don't use rubber hose. Use Nylon type hose. Most all modern cars use this type of tubing. It will not crack, split or deteriorate over time.
Also harder to pinch it closed.