Fiddling with the MAP sensor is a little more complex.
There are two ways a EFI could react to changes of the driver. The simplest ist called alpha-n.
Alpha stands for the angle of the Butterfly in the manifold. n for the rpm. So if I turn the gasgrip, the Butterfly opens and the TPS (Throttle position sensor) sends the new angle to the EFI. The EFI looksup in a map, how much gas should be injected at the current rpm, and good we are.
The other method is Speed density. For this we need a MAP (Manifold air pressure) sensor. It measures the ambient air pressure before we start the engine. Then it measures the changing pressure inside the manifold relating to ambient pressure while we turn the grip. The changes are most pronounced in areas, where we have a lot of throttle movement. So in low speed. In high speed the Throttle is nearly all open all the time, so the pressure difference is low. And then unusable as a sufficient sensor signal. The MAP sensor indicates the load of the engine. More load means more gas necessary. The ECU looksup in a map, how much gas it has to deliver at this specific load.
The load is different, if you pull the trigger and have large alpha differences in low gear or in high gears. Or driving on a plane road or climbing a mountain pass.
Both philosophys work best at their specific range. Speed density is good for low and crusing speed, as the pressure differences are big. Alpha-n works best at large throttle openings, where the pressure differences are low, but the change in throttle position is still a valid data.
So the Keihin ECU does exactly that. It works with speed density in low areas and switches to alpha-n in higher areas.
What about fiddling with the map sensor. One could think that by changing the voltage output of the map sensor would change the mixture in lower/cruising areas. That is not the case. First of all the MAP sensor just measures differences to the first ambient pressure of the not-running bike. So if I change the voltage, it would just measure another ambient pressure and the changes would be equal.
If I fiddle more and change the voltage after the bike runs, it would work for a while. But the EFI remeasures the ambient air pressure while running. This allows the engine to adapt to height changes while driving up a mountain. This measurement is done at a preset angle of the crankshaft, where the MAP pressure is most likely the ambient pressure.
There were aftermarket devices on the market which fiddled with the map sensor data. But they were expensive and not as effecticve as the simple Booster Plug devices.
It could be that another MAP sensor with a changed characteritic could make a differnece, but that depneds on the EFI programming. And as far as I know all MAP sensors are mass produced and quite equal.
When I tune the Keihin EFI with a powertronic or eual device, I dont have to think about what system is used, the EFI tuning system presents me an calculated value (sometimes called FTC ore otherwise) that combines both methods to a single Load-value.
Lemma1:
The easiest fix for more fuel in the whole rpm band would be a 10% bigger fuel injector. I have done it on several bikes. But it only works in Open-Loop operation (no Lambda sensors).
Lemma 2: When you use overpressure systems (Turbocharger or compressor) you have to have an Alpha-n regulation.
Topic: Booster plug (Read 2977 times)