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Convert MAP-based tune to Alpha-N

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I've got a Radical SR8 (V8 ITB engine based on a pair of Hayabusa cylinder heads) that's currently running with a MoTeC M150 (GPRP-based firmware) and is using a MAP sensor for the load axis in the VE table. The car runs reasonably well, but it idles at 87kPa, so there's not much fidelity in the tune.

I'm considering switching the load axis to throttle opening, to see if I can get a bit more fidelity in the tune at lower engine speeds. I'm wondering if anybody has any experience with the M1 ECUs doing such a transition. Is it just a matter of setting up the axes, and using the same VE values?

I do have a fuel map from the original ECU (pulse width in ms over throttle percent and rpm) The OEM TPS - fuel map is fairly flat compared to the M1 MAP-based VE table (which has an enormous hump at 100 kPa and 9800 rpm).

Any thoughts? Is there a method to convert the fuel map to VE?

Thanks!

John Parsons

And so, to answer my own question (with some Tech support from MoTec). See

https://www.motec.com.au/filedownload.php/CTN0036%20Multi%20Throttle%20Tuning%20Method.pdf?docid=597

The net result of this change is to tune to the desired lambda by filling in the Inlet Manifold Pressure Estimate Main table until the Exhaust Lambda matches the Fuel Mixture Aim. You can even do this with closed loop (to reduce chances of ultra-lean conditions) by using the Exhaust Lambda (Bank 1) Normalised.

I now have a perfect tune at idle. Dyno time next week to fill in the rest of the table.

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