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Whats happening when you forget to check base timing

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Hello all,

i’m curious about what can happen when you forget to check basetiming when you just built you engine complete (RB26) and cas sensor was off? Did nothing on the tune so the timing was locked. Cab you tune further with that tune without checking base timing?

Also it have a new higher headkasket and the camgear degrees are done.

can anyone tell me that??


You can stop at anytime and check the base timing. If you had tuned the ignition and found the basetiming was off, you could offset your entire ignition table to compensate.

If I read the question correctly, you've rebuilt the engine and haven't confirmed the ECU and physical "TDC" are the same after the rebuild?

Best case scenario it is the same and hasn't moved; less good, it is costing torque/power because it isn't optimised; worst case scenario you are damaging your engine.

Besides the above, you should always verify the TDC point as it gives a consistent reference point for changes, the next rebuild, for using your map in another vehicle - or vice versia, etc.

Yes for safety sake its worth the 15 minutes to verify base timing. The available adjustment of the CAS is pretty significant in terms of timing. I just rebuilt my rb26 because the previous owner ran with detonation and ruined the engine.

On an engine with an adjustable CAS it's a good idea to move it to the maximum advanced setting and then sync the ECU so the ignition timing at the crankshaft matches the ignition timing in the software. Doing this will result in less advance (not more advance) if the CAS ever gets adjusted by an uninformed mechanic, or somehow gets loose and moves while the engine is running. That said, I've heard from experienced tuners that switching to a crank-mounted trigger wheel is worth the cost on RB engines. OEMs quit using 'crank' sensors mounted on camshafts a long time ago.

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