Hondata

This was a stock B18C5 motor with water/meth cooling until detonation blew a hole in one of the pistons at ~12 psi (JRSC and stock internals)

The block is now Benson sleeved with Eagle H Beam rods and CP 9.5:1 pistons. My question is, how does the timing from my old map need to change in order to better suit this motor?

Stock was 81mm, this is 84mm. I calculated the change in displacement and have adjusted the fuel multiplier to get me close for base map purposes. Thus far, I have not adjusted the timing. My builder (Benson) told me that I will be able to run much more timing than the stock motor due to the lower and safer CR. That is fine and I will do the boost tables on the dyno, but as far as for the part throttle columns of the tables, how should timing be adjusted?

I haven't seen any guides or suggestions on how timing is affected by larger displacement or changing the compression ratio. Will running the same timing maps from the B18C5 with JRSC suffice, or will that cause problems?

EDIT*

If this matters, no flow changes were made to the head; however, Inconel exhaust valves, upgraded valve springs, bronze guides, new steel retainers, seals, etc were installed (all Supertech).

Please advise.

Part throttle should matter much, but everythign else will need to be tuned on the dyno.

Timing can better be tuned on a dyno; can be done on a EMPTY deserted street but is time consuming.

1) Part Throttle Sweeps

Start with a conservative timing map. Tune the AFRs. The timing curve should APPROX be the inverse of the fuel curve. Where fuel increases, timing increase should be flatter or even drop.

Do a part throttle pull. Take out (retard) may 2-3 degrees* across the board. Note where (i.e at which r.p.m.s, paying attention to fuel curve) where torque drops, stays the same or increase. Adjust the timing accordingly. Repeat. Repeat. Repeat

*this safer than adding timing.

2) Minimize INJ/Duty at a constant cruise speed/part throttle, by adjusting timing - data log it.

3) Steady State Dyno (spark hook test) - do a google - that how the OEMS and semi-pros do it.