MAP Sensor signal VERY Noisy
 

MAP Sensor Issues

The Application is for a Rotary Engine (2 Rotors) with Dual Throttle Bodies, Each Throttle Body Feeding Each Rotor (No Plenum)

Rotary Engines have very strong and abrupt intake pulses.
(This is not an issue in “stock” intake applications since there is a plenum to smooth out the intake pulses)

Originally when the Haltech E6X was installed, the MAP Sensor was connected to one of the TB’s. The Vacuum signal was too noisy (pulsations) to give a consistent reading to the E6X.

Then I put a short tube (1/8 inch I.D.) from each TB, connected to a “Y” connector which then feeds the MAP Sensor with a 3/16 in. tube (I foot long).

That gave better results, but the signal is still too noisy as can be seen when looking at the fuel maps in the “online” mode.
For Example, at idle you can see the little arrow bouncing from one bar to the other. It typically hops across 2 to 3 bars.

Any guesses on how to fix this?

I was thinking of a small “expansion chamber” in the line leading to the MAP Sensor.
Like a small plenum that will hopefully act like a “Pulsation Dampener”

I can’t find something to use for this, so it would need to be fabricated.
Too Big or Too Small is a problem, not sure how big to make it.

Any suggestions?

Also - does anyone have an electrical schematic for a MAP Sensor?
I can not find one anywhere.

Thanks,
Steve

It's normal for the vacuum to fluctuate a bit at idle. Even on a stock engine it's normal for the indicator to jump between two bars. I just completed an install on a rotary with twin 50mm TWMs and don't have an issue at all. The idle is remarkably steady with the same vacuum routing that you currently have.

If you do have a problem stabilizing the idle there is a feature with the Haltech just for this situation. In the fuel setup page enable the zero throttle map. Then open it and tune it to stabilize your idle. It allows you to program a fuel curve just for a zero throttle situation. The ECU will disregard the MAP sensor and it's fluctuations at idle.

Map sensor isnt deffective, its just that when you have a ported 2 rotor engine with ITB's there's simply too much pulsation on it. You can use the line between the 2 runners (after the throttles) to balance the pulses, and also put a small filter in line so it stabilizes a little more, but you should also use the zero throttle map like ludwig said.

What type of porting?
Rpm at idle?
Vacum at idle?
Ignition timing at idle?

What kind of filter are you referring to?