Why is our MAP sensor in the ECU box?
#24
I thought the standard vacuum line to use for the MS was the one on top, near the throttle body, not the one at the back of the manifold? That's the one I'm using, I've probably got 2 feet of vacuum line inside the engine bay so that it's routed cleanly and has enough slack.
FWIW, the 4 bar MAP sensor sold by DIYautotune is a chip on a board, it's designed to go inside the ECU case, not in the engine bay. You may be thinking of the GM 3 bar MAP sensor which is a weather-sealed standalone module. I have the 3 bar GM sensor (I'm running 230 kpa, so the 250 kpa built-in sensor doesn't have enough headroom), but I have it in the glovebox with the MS3. Putting it in the engine bay would be marginally superior, but not enough that I'm inclined to go to the effort of moving it.
So the short version of the answer is that the MAP sensor is in the ECU box because mounting it externally is not enough of a win to justify the increased cost, effort, or complexity.
--Ian
FWIW, the 4 bar MAP sensor sold by DIYautotune is a chip on a board, it's designed to go inside the ECU case, not in the engine bay. You may be thinking of the GM 3 bar MAP sensor which is a weather-sealed standalone module. I have the 3 bar GM sensor (I'm running 230 kpa, so the 250 kpa built-in sensor doesn't have enough headroom), but I have it in the glovebox with the MS3. Putting it in the engine bay would be marginally superior, but not enough that I'm inclined to go to the effort of moving it.
So the short version of the answer is that the MAP sensor is in the ECU box because mounting it externally is not enough of a win to justify the increased cost, effort, or complexity.
--Ian
#27
Ok, stupid question incoming, but I have yet to come across an answer to it and I been wondering about it since I learned about speed density control.
Why does a speed debsity system care what the outside pressure is? 70kpa in the intake manifold is 70kpa. I can't wrap my head around why a second sensor is needed to compensate for altitude. Although I know that it is fairly often needed. Am I just thinking about this too simply and missing something?
Why does a speed debsity system care what the outside pressure is? 70kpa in the intake manifold is 70kpa. I can't wrap my head around why a second sensor is needed to compensate for altitude. Although I know that it is fairly often needed. Am I just thinking about this too simply and missing something?
#28
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because the load has also changed between those two point, and thus the fueling requirements have changes as well. Your whole fuel map would shift if you tuned at a high altitude, and then again at a low one. The baro corrections are actually correcting for the changes in VE (exhaust pressure, throttle position, crankcase pressure, humidity, etc).
#29
because the load has also changed between those two point, and thus the fueling requirements have changes as well. Your whole fuel map would shift if you tuned at a high altitude, and then again at a low one. The baro corrections are actually correcting for the changes in VE (exhaust pressure, throttle position, crankcase pressure, humidity, etc).
But since the exhaust pressure and other things change as well, the VE of the engine changes so it isn't taking in x amount of oxygen for x density, it is taking in some other amount (z maybe) and needs the fuel to change. Yes?
#33
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And this is the type of MAP sensor I was talking about: https://www.summitracing.com/parts/f...2KAaAqcd8P8HAQ
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