greg_moreira
Very Senior Member
Posts: 3262
Reg: 10-06-03
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04-20-12 06:12 AM - Post#2217195
In response to gotta56forme
I haven't run the numbers, but a question for the more learned of you would be... considering that it sounds like he is going to have a high SCR, is he going to have a workable DCR with his chosen (for now) voodoo cam so that he will be able to run premium gas or below? I'm wondering if the parts choices are hinting at a high DCR and that it will be too high for pump-friendly gas based on what we seem to know right now...
Just to talk about DCR for a second, remember that its only a guideline and not a guarantee.
Cylinder filling hugely dictates what happens. If you had no cylinder filling at all, you couldnt create any cylinder pressure regaurdless of how high the compression ratio is. Even if it were 14:1 compression, compressing nothing 14 times still makes no cylinder pressure.
On the reverse of that....even with low compression and a low calculated DCR, a blower/turbo motor can still build very high cylinder pressure. The cylinder pressure is a function of the blower/turbo filling the cylinder, regaurdless of how low the static and dynamic comp is.
Even in terms of a naturally aspirated engine, the difference between 80% to 95% VE can make one engine more sensitive than the other even if they both have the same static and dynamic comp.
So yeah there isnt really a clear cut line as to what DCR should really be. Only a decent general guideline for the average engine. With all that said though... if this combo stayed exactly as proposed, 11.5:1 or more compression definitely would not be safe to run with the lunati cam.
But he did say he is now going to change pistons. If we use a piston that brings the compression down to 10:1 then Id have no worry about 10:1 comp with this camshaft.
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