Boostdriven
10+ Year Contributor
- 622
- 14
- Jan 7, 2010
-
Pasco,
Washington
Just want to share few ideas with those who are logging the exhaust pressure with a MAP sensor.
One issue that I had was a constant accumulation of water from condensation in the exhaust inside the MAP sensor. Another issue was a jumpy signal in the log, it fluctuated few psi due to a rapid change of pressure of pulsating exhaust.
I use a GM 3bar MAP sensor and used to have it positioned with the air nipple sitting horizontally, this allowed water to accumulate in the sensor. So few days ago after some thinking I remembered that every map sensor that I've seen on a factory vehicle is always positioned with the air nipple pointing down. This would allow any condensation to drain out of it. To fix this I built a bracket to hold the MAP sensor with the nipple pointing down. Important thing to keep in mind is that the MAP sensor has to be placed above the feed port on the manifold so any condensation in the sensor will drain to the manifold.
Originally to fix the water problem I figured I would just put a T fitting in the rubber hose pointing the T fitting down. From the T fitting I would run another piece of hose in to some kind of a container/catch-can. The idea was to allow water to drain through the T fitting in to that container but as I got to thinking about it I realized that I already had my MAP sensor located higher then the feed port on the manifold and still was getting water in the sensor. So the idea of a drain container wouldn't of worked but it generated another idea. If I use a drain container it should act as an expansion tank and absorb the shock of a pulsating exhaust and possibly give a more stable line in the log.
So after work today I built what you may call a "contraption"
For the expansion tank I used an empty CO2 cartridge from a BB gun and tig welded a piece of 3/16" tube to it. I put the T fitting in the rubber hose pointing up with a short piece of hose going up to the CO2 cartridge (expansion tank). The reason for the T pointing up is the same as for the MAP sensor so condensation would drain down out of the expansion tank. When I took the car out for a test drive the E-map line in the log was just as stable as my boost line.
Currently my E-map setup consists of 1/8" copper line about 16" long which runs from the manifold to a 3/16" rubber hose about 8" long which connects to the MAP sensor. In the rubber hose I have the T fitting that goes up to the expansion tank. I use a regular copper line that you can buy at a parts store for a mechanical oil pressure gauge. I attached a picture of my current E-map setup.
Few tips for those who are planning on getting an E-map setup. When you drill and tap the manifold don't just screw in the brass fitting in to the manifold. The heat will weaken the soft brass and eventually the fitting will get loose. I like to use about an 1"-1.5" steel extension (male-female) screw that in to the manifold first then screw the brass fitting in to it, this will keep some of the heat from the brass fitting. You can buy the metal extension from any hardware store. If you don't have a way to build a metal expansion tank, you could possibly use a plastic fuel filter inline of a rubber hose. My only concern is that by the time the filter would pressurise, enough hot exhaust would enter it and possibly cause the plastic to melt. You could probably use a smallest size metal fuel filter but you would have to position it vertically so condensation would not accumulate in it.
Hope this helps you my fellow tuners
One issue that I had was a constant accumulation of water from condensation in the exhaust inside the MAP sensor. Another issue was a jumpy signal in the log, it fluctuated few psi due to a rapid change of pressure of pulsating exhaust.
I use a GM 3bar MAP sensor and used to have it positioned with the air nipple sitting horizontally, this allowed water to accumulate in the sensor. So few days ago after some thinking I remembered that every map sensor that I've seen on a factory vehicle is always positioned with the air nipple pointing down. This would allow any condensation to drain out of it. To fix this I built a bracket to hold the MAP sensor with the nipple pointing down. Important thing to keep in mind is that the MAP sensor has to be placed above the feed port on the manifold so any condensation in the sensor will drain to the manifold.
Originally to fix the water problem I figured I would just put a T fitting in the rubber hose pointing the T fitting down. From the T fitting I would run another piece of hose in to some kind of a container/catch-can. The idea was to allow water to drain through the T fitting in to that container but as I got to thinking about it I realized that I already had my MAP sensor located higher then the feed port on the manifold and still was getting water in the sensor. So the idea of a drain container wouldn't of worked but it generated another idea. If I use a drain container it should act as an expansion tank and absorb the shock of a pulsating exhaust and possibly give a more stable line in the log.
So after work today I built what you may call a "contraption"
For the expansion tank I used an empty CO2 cartridge from a BB gun and tig welded a piece of 3/16" tube to it. I put the T fitting in the rubber hose pointing up with a short piece of hose going up to the CO2 cartridge (expansion tank). The reason for the T pointing up is the same as for the MAP sensor so condensation would drain down out of the expansion tank. When I took the car out for a test drive the E-map line in the log was just as stable as my boost line. Currently my E-map setup consists of 1/8" copper line about 16" long which runs from the manifold to a 3/16" rubber hose about 8" long which connects to the MAP sensor. In the rubber hose I have the T fitting that goes up to the expansion tank. I use a regular copper line that you can buy at a parts store for a mechanical oil pressure gauge. I attached a picture of my current E-map setup.
Few tips for those who are planning on getting an E-map setup. When you drill and tap the manifold don't just screw in the brass fitting in to the manifold. The heat will weaken the soft brass and eventually the fitting will get loose. I like to use about an 1"-1.5" steel extension (male-female) screw that in to the manifold first then screw the brass fitting in to it, this will keep some of the heat from the brass fitting. You can buy the metal extension from any hardware store. If you don't have a way to build a metal expansion tank, you could possibly use a plastic fuel filter inline of a rubber hose. My only concern is that by the time the filter would pressurise, enough hot exhaust would enter it and possibly cause the plastic to melt. You could probably use a smallest size metal fuel filter but you would have to position it vertically so condensation would not accumulate in it.
Hope this helps you my fellow tuners
