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Relocating the MAF into the charge pipe.

6061 Views 21 Replies 7 Participants Last post by  5banger
I should make my own mod thread for all of my mods but I don't plan on doing much. I just want to do some few simple mods to aid in tune accuracy and consistency. The best mpg's is the main goal because I have another vehicle that fulfills my power needs.

The reason for this mod is to allow the maf to see the actual airlow the engine will be ingesting. The problem with having the maf at the inlet of the compressor as opposed to in the cold side charge pipe is there could be a huge airflow difference between what the maf is reading from what's actually in the charge pipe due to pressure drop and IAT differences. If I move the maf into the charge pipe, the maf will see the true intake air temps and a more consistent airflow reading improving maf tunability throughout the operating range. Iat's can differ 30*+from the inlet tube to the charge pipe so the ignition timing tables will control timing much more acurrately and consistently as well.
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Didn't have all this stuff with a carb, venturi effect would suck the correct amount of fuel depending on the jet size. But unfortunately, only good at sea lever, really noticed this when driving in Bogota, Columbia, carbs are running rich and the air is thin with a super strong odor of gas in the air. Airplanes compensated for this with a mixture level, but you sure had to learn how to use it or would carbon up your engine or toast it.

Better carbs have a bellows installed that would expand with altitude that shoved tapered rods into the jets, the calcuations for this would drive you nuts. Tried to maintain a 14.7:1 air fuel ratio, but only good for steady driving, when you hit the gas, this would decrease the AF ratio to 12:1 to gain more power, for this, an accelerator pump was added.

Essentially, a throttle body is just like a carb except fuel was removed. So a MAP, MAF, IAT, and a barometric sensors were added to control injector dwell. Timing advance or retard is yet another issue, centrifugal and vacuum advance was replaced by a combination of these sensors as well as adding anti-knock sensors. All these work in combination together with mass calculations done by a computer.

But mostly in so-called open loop mode, O2 sensor is worthless until the engine reaches normal operating temperatures and driving at a constant speed. Open loop does take over when you hit the gas, O2 sensor is way to slow to keep up with this.

All these sensors are working with harmony with each other, with OBD I open loop loop parameters would learn from closed loop parameters. This correcting data was stored in RAM, but if you disconnected the battery for a second, this data would be lost. Had to drive your vehicle at least 20 miles to relearn. Ha, had fun with this by calibrating all of the sensors so there was nothing to learn.

With OBD II, stored in flashram, so this data was not lost when disconnecting the battery.

But just saying, your MAF is working in harmony with all the other sensors, if you fool with it, not only breaking EPA regulations, but also risk either carboning up your engine or toasting it. Best to leave it stock.
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