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Need recommendations on End of Injection timing and Lambda targets for large overlap cam and Alpha N

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Hello all,

I am trying to set some generic targets for Lambda at idle and some starting numbers for End of Injection timing parameters.

Looking to kick the engine over soon and test out the test advance and CRIP settings for accuracy and adjustments as required.

Running Alpha-N on a Motec M8 with 42lb injectors on a 455 Oldsmobile.

For now, I assume that the overlap will be large enough that the Lambda reading will falsely show lean at idle, so I have moved the targets up from 1.00 to 1.15 to hopefully compensate for this.

Thoughts on this?

Also, I have been looking at delaying the end of injection points to help with pushing fuel out the exhaust valve during overlap.... but, I don't know what numbers to try for this effort.

My current setting is 295 degrees BTDC at 1000 rpm.

Any thoughts on this number?

Thanks in advance!

I get your logic on the Lambda target, but when trying to get an engine running for the first time, it's much easier and will run smoother if it's a bit rich. I think you should target Lambda 0.95 - 1.0, until you know there is reason not to (like the plugs are fouling after idling for 5 minutes).

270 - 300 degrees is a good fuel timing for low RPM.

Thank You both for the considerate answers and reference! I have changed the Lambda table back to target 1.00 for now and we will see where it is at after I check and adjust the CRIP and we hook up the exhaust and lambda sensors so we can start it up for the first time on fuel injection. At least we know the Engine is all good as it was broken in on the dyno and ran with a carburetor and regular GM HEI distributor.

To optimise end of injection timing it’s good practice to graph it out in relation to intake valve opening to see if you’ll be injecting on the back of a closed valve. You’ll have to take into account the distance from the injector to the back of the valve too.

One method to tune injection timing on the dyno would be to use a gas analyser and pay attention to UHC and MBT theory being if injection timing is out they’ll be a higher UHC content as unburnt fresh charge will be exiting the exhaust. If you’re running an NA engine with an open intake, visually monitoring fuel stand off will help as there will be a cloud of fuel vapour hovering over the trumpets at certain speed due to the injector injecting on the back of a closed valve.