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John Appel

MAP sensor on Individual Throttle Bodies

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On our twin cylinder motorcycle engine we have two throttle bodies.Engine has equally spaced firing intervals. Because of ITB we are using TPS for the load axis on our fuel and ignition tables. The EFI tuning books say using MAP for load axis on ITB engines does not work because there is no plenum chamber to smooth out the vacuum pulses from each port.  In our inlet ports we have tappings for vacuum pipes. Currently we have these plugged up. I have been told that even though we are using TPS we should still connect the two vacuum tappings to the Link G4 Storm using a Y junction and rubber hose. This would smooth the pulsations to some extent but not much. Can the Link make sense of such a highly fluctuating signal. Does it have some form of electronic smoothing circuitry to deal with this problem. How does the Link make use of this vacuum signal when I am using a miilisecond base fuel table and TPS for load. Any advice.

 Regards, John

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I used map for load on my 350Z with Individual Throttle Bodies, I've run 6 separate lines back to a manifold this then goes to an inline fuel filter which was big enough to smooth the pulses out it's a bit erratic on idle but past that it's fine

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3 hours ago, John Appel said:

On our twin cylinder motorcycle engine we have two throttle bodies.Engine has equally spaced firing intervals. Because of ITB we are using TPS for the load axis on our fuel and ignition tables. The EFI tuning books say using MAP for load axis on ITB engines does not work because there is no plenum chamber to smooth out the vacuum pulses from each port.  In our inlet ports we have tappings for vacuum pipes. Currently we have these plugged up. I have been told that even though we are using TPS we should still connect the two vacuum tappings to the Link G4 Storm using a Y junction and rubber hose. This would smooth the pulsations to some extent but not much. Can the Link make sense of such a highly fluctuating signal. Does it have some form of electronic smoothing circuitry to deal with this problem. How does the Link make use of this vacuum signal when I am using a miilisecond base fuel table and TPS for load. Any advice.

 Regards, John

I wouldnt bother with map sensor as long it is an NA-engine. I prefer using TPS as load with ITB. If it is turbo, then use both map and tps. 

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John,

As per bsh's comment there in most cases there is nothing to gain from a MAP sensor for an NA ITB application, with two main exceptions:

  1. If you have an idle control valve that bleeds air past the throttle blades then a MAP sensor will help account for this and keep AFR more consistent at idle.
  2. If you have an air box that is restrictive or sees significant aerodynamic pressurisation then I like to have a MAP sensor connected to the air box to account for that (probably more correctly called an airbox absolute pressure sensor in this case but it its set up as a MAP in the software).

Many other brand ECU's dont have a built in baro sensor you will see many people will recommend fitting a MAP (even if not connected to manifold) with ITB's to account for baro changes.  Since all Link ECU's have a baro sensor built-in, this is already taken care of - you just need to set the fuel equation load source to BAP. 

 

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3 hours ago, John Appel said:

If I remove the vacuum hose from the ports to the Link should I block up the pipe on the Link or leave it open.

 John

If you have a Monsoon with a built-in MAP sensor then I would probably plug it to keep it in good condition.  Make sure the equation load source is set to BAP and turn off the MAP sensor to prevent anything like a MAP limit or similar causing confusion in the future if it ever gets pressurised.

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