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Message: <blockquote data-quote="shiroitenshi" data-source="post: 3194122" data-attributes="member: 27518">About CR, you have to measure the volume of the dome and combustion chamber, can guesstimate based on ready specs,but some heads already milled when bought second hand, so sometimes it can be a little higher than initially thought. That's why measuring is probably the most accurate way to get it. The curious thing is that most mechs here deem it 'unnecessary'. when most high buck builders do it, even for their own race engines running specs they probably built dozens of times.With most aftermarket pistons 84mm +2cc and below, if street spec, and with stock head (unmilled) and block, should be a little below 12CR with stock 89mm crank, but if running aftermarket cranks like 92/95mm, that number easily goes up to 12-13ish with the same piston.You can also use the compression gauge to estimate compression, but it's a crapshoot because the numbers reflect how well your engine is sealing, not the compression. If you have a leaky 13CR engine, it may give compression readings of a healthy 11-12CR engine.Example, a 11CR B16 with a tight ring gap gets 230, while a 11.8CR B20 with looser ring gaps get 245.Really high compression engines with tight ring gaps can hit 300+, which is out of the range of most common compression testers mechs have out there. But the engine will heat up easily and given time, warp heads, lose sealing, seize, etc.Anyway, for the rod stroke ratio, it's all about having a tall enough block and a piston with a wrist pin high enough. I haven't seen anyone using a piston with a wrist pin sitting right under the oil ring (not actually under, but close), but theoretically I think the engine should consume oil a bit. But that's theoretical, in practical use, I'm not sure the effects of having an oil ring sitting on the wrist pin hole.But haven't anyone considered the losses associated with having high rod ratios? low rpm torque will be lower with those setups, which is all good if it's a race engine seeing high rpm, but for a daily driver seeing low rpms?Thankfully the B20B has oodles of low end torque to sacrifice. I wonder if anyone has ever compared a B16A and B16B stock engine torques? Based on the rod ratios, the low end should be a lil worse for B16B due to it's higher rod ratio.Anyway, SFL.Considering the amount you put on your engine, isn't that extra expense of having proper engine management worth it? I mean, with simple management retailing like half of what your cams costs.. IMO, it's certainly a minor expense, isn't it?Sure you can crank up the fuel pressure and play with the static timing, but in the end you'd end up with a very narrow powerband, and probably foul your plugs and rings running to rich. But if you're risking running lean, that's another matter, and another set of risks.Your build though, so it's still your choice. Good luck with your build.</blockquote>

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