Hi, I was wondering if stock B16 cams would take advantage of a compression increase and what would be the maximum compression to run before it starts to be undercammed.

I've seen a stock head B16 on E85 make around 165whp running 12.5:1 compression with basic I/H/E. It responded well on retarding the exhaust cam timing and not much effect on changing the intake cam. My reasoning behind that is the engine responded well retarding exhaust timing to bleed of compression meaning that it was undercammed even on E85.

When selecting aftermarket cams, builders increase compression to compensate for the loss in dynamic compression that cams with a higher intake opening ABDC degree spec give, and ideally you would maintain the dynamic compression close to the original static compression value whan doing this. On a stock B16 you have a 9.4:1 dynamic/effective comp ratio with stock cams (40 degrees ABDC) and stock compression. Will an increase in static compression to about 11:1 be beneficial seeing that it would bring DCR close to standard static CR? Is a mild increase to say 10.5:1 and adjustments in cam timing have basically the same effect on this scenario? Any insights on this?

 

Intake valve closing event retarding is what "bleed" out compression i.e. decrease dynamic compression, not exhaust.
The reason why engine reacting to exhaust cam retarding is probably increased overlap, which always have a positive effect with small cams.

 

I see. It does make sense, I got confused. Do you think the same gains could be achieved on another engine running much lower compression (12.5:1 vs 10.5-10.8:1) with the same stock cams on either setup?

Even with such a high CR the engine is not undercammed with stock cams and will actually take advantage of the increased CR? It's known E85 likes high CR engines, but again the stock cams are still the limiting factor.

 

No, because overall effiency is better in higher compression engine.

Camshaft profile determine engines desired nature, fuel set the limits for combustion progress. What is the highest pressure for optimal burning and how much it is possible to get energy from it.