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I'm currently tuning a Suzuki Swift Sport but experiencing something very strange with the manifold pressure readings I am seeing. We are utilizing the onboard map sensor on the elite 1500.
Basically the issue is I am seeing the MAP reading fluctuate very largely and going to atmospheric pressure with very small throttle openings. This is making it impossible to tune the engine in steady state on the road using left foot braking. Furthermore if I do somehow get the engine tuned properly then it will be acfessing wot target afrs when cruising hence fuel economy will suffer badly.
What I am thinking to do is use alpha n for the fuel table but then what about the ignition table? Can anyone shed some light on why this might be happening? The car is running the stock suzuki intake setup, single plenum.
Are you taking the pressure reference from the plenum or a port right next to where the throttle sweeps? It sounds like your signal is from a throttle progression port.
I will take a photo of where the vacuum line from the haltech onboard map is plumbed. It seems to be very close to the throttle body. I think you've made a valid point....the location may be the issue
See attached photos
Its a bit hard to work out where that all goes. Definitely make sure it isn't a common port with brake booster. I'm guessing it might be time consuming to pull the throttle boy off but if I wasn't sure I think i would want to trace all the ports through to see where they come out on the inside/what they are shared with. Avoid emissions or brake booster. I'm not sure if you model is port or direct injected, if port injected and manifold pressure refetenced regulator, fuel pressure reg reference line is better than nothing if there are no other decent acess points/ports on the throttle body or manifold. I don't think you should have a problem using speed density on a modern engine that doesn't have a wild cam/valvetrain setup if you get a decent reference.
I temporarily removed the crank case pcv and took a tap where that would normally go which is on the complete opposite side of the intake manifold....same thing....zero difference. I think this is a characteristic of this engine .....it had a variable intake flap as well which varies plenum volume....this was not active however when seeing the map reading fluctuate with small throttle opening. I have now resorted to tuning the car with tps as load on fuel and ignition tables....I may even have to use a 4d overlay for fuel .....very very strange this engine...