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MoTeC M130 Rich Transient (Fuel Film Disabled)

MoTeC M1 Software Tutorial

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Hello everyone, this is my second time tuning one of my vehicles using a MoTeC M1 ECU. I have a issue that I never faced before on this most recent one, and that is my air fuel ratio is very rich during transient conditions, especially during free revving: on neutral or when the clutch is engaged.

The fuel film sub system is disabled, when enabled issue worsens as in the AFR becomes even richer and the transient response becomes worse.

The engine runs fine at part throttle, WOT, cruising. Transient conditions when in gear are fine too, the response is great when it is in gear.

Vehicle: 2001 Toyota Land Cruiser 100 Series with the GEN 2 1FZ-FE Engine, naturally aspirated. Running on pump gas, 93 Octane.

I ensured all the parameters are correct:

1. Engine Displacement (In my case 4.65L)

2. Injector calibration (In my case: ID1050)

3. Default Fuel Pressure (40 PSI, Ambient Referenced)

Furthermore I have confirmed and played around with the following:

1. That the TPS sensor is calibrated correctly and that it is not fluctuating in an uncontrolled manner.

2. The engine charge cooling gain (raised it and lowered it to see if it may fix the issue)

3. Isolating the cells in the fuel map that is reached during the transient conditions during free revving and moving those up and down. This is where it gets really problematic since I can manage to lessen the issue a bit by lowering the VE numbers in those cells BUT during normal use it will run too lean, so I cant imagine the issue lies in the fuel table unless I am not aware of something.

4. Playing around with the fuel timing, more specifically the Fuel Timing Primary Main, Fuel Timing Primary Limit and the Fuel Timing Primary Makeup. The Fuel Timing Primary Limit and the Fuel Timing Primary Makeup have significant effects on the transient response (AFR and Feel) but moving those around up and down only really changes the feel, it still does not solve the issue. Moving the Fuel Timing Primary Makeup from 190 to 380 does stop it from going rich BUT the transient response becomes way slower.

When I say too rich during transient I mean it goes down to 9 or 10 AFR.

Any help would be appreciated, maybe I am missing something.

What firmware package are you using? Do you have a log you could upload showing the problem?

Is Closed Loop Fuel Mode enabled? If so, have you tuned the Fuel Closed Loop Period? What is the Fuel Closed Loop Control Trim Minimum (and Maximum)?

Since the difference in free reving and transients in gear, is the rate of acceleration in the engine, are there any Engine Speed Reference Diagnostics or Engine Speed Pin Diagnostics in those cases?

The interaction between makeup and limit values will influence whether a second injector pulse is allowed or not. If the makeup angle is higher than the limit value, it will add additional fuel on a second pulse if calculated that its needed. In practice most combinations are best off having the makeup pulse set lower than the limit to disable it from happening.

If you efficiency table is well tuned, do you have inlet manifold blend and decay values set to non 0 values? If so this will allow the efficiency estimate main table to be referenced in these circumstances, and if this is not well tuned, it can influence fuel. If this is active, if you put inlet manifold pressure and inlet manifold pressure sensor on a timegraph, you will see these values deviate and return to the same value on the transients.

Does your setup run a fuel pressure sensor? If it doesn't, do you run a stock fuel pressure rail and regulator? Im guessing based on the injector size (unless they are way oversized for your application) that you would have a fair bit of fuel pump flow too.

Depending on the regulator and return line in the car, you may also have a very non linear fuel pressure differential, which would deviate a lot from estimated fuel pressure.

Fuel temperature estimate can also cause error in the fuel model, particularly as most leave it at as a static value, but this has a greater impact on starting and when the fuel film is active.

Lots of great suggestions here already.

Is there any chance what you're seeing is based on combustion as or after you've lifted throttle?

I ask because when briefly stabbing at the accelerator pedal in neutral the time to rev is often so brief that much of what you see in the lambda trace may be occurring after you're released the accelerator.

Have you tried testing this with higher base fuel pressure? Those injectors seem to operate more happily with with a bit more differential pressure.

Pardon if none of this applies, but without a log we aren't clear on what you're seeing.

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