SB

Pretty sure OP has intercooler….i remember done water flow question he had. We’ll see. But if he does, 5-6 psi will prob make similar power (or more) that a cam change will do.

Brad Christy

SB, Tartilla,

There is an intercooler, and, yes, it is capable of 5lbs of boost.... With a pulley change. It is currently set up for about 3.5lbs, and I don't currently have plans to change that.


Thanks. Brad.

Brad Christy

UnderPSI,

The builder has software developed numbers and is reasonably confident we won't get reversion. As I've said, he's built many engines with custom cams. He knows his stuff. It's ME that has doubts, because the numbers seem close to what I've read/heard might induce reversion, and I'm asking for advice from people whose opinion on the matter I've come to respect.

I've also been told the cam is ultimately the limiter that I can relatively easily change to overcome some of the limitation. I'm asking for numbers. Not cam recommendations. Not alternative routes to the same end goal. Just cam numbers. That's it. Can we consider this a theoretical conversation?

I'm trying to understand the somewhat finer points of cam function. I see terms like lobe separation, lift @.050", lift @.200, duration, overlap, etc.... As I understand it, it's that overlap that is the root cause of reversion. The stock cam has 1° of overlap, with moderate durations and the Raylar cam has 4° with semi-aggressive durations. I guess my question is, can one shorten the exhaust and intake durations of the Raylar cam, which would be longer durations than the stock HO cam, but retain (or, at least, lean toward) the total valve-open duration of the Raylar cam (from opening of exhaust to close of intake), spreading the lobe sep, to close that overlap, and see gains in HP, torque and/or RPM?

Thanks. Brad.

Brad Christy

SecondWind,

I hear ya. It's not so much the noise for her, per se. She doesn't dislike it. It's the capacity to shut the noise down for conversations with people on other boats and such that she likes. We didn't have the option with our previous boat, and, now that we've got it, she likes it. She really liked being able to be on a Teams call for work, getting paid, in her bikini, with a drink in her hand, as we motored down the lake. I can't say I disagree with the logic.....

Thanks. Brad.

Brad Christy

Carnutzx2,

The builder is familiar. He's mentioned the relevance of "duration @.200" vs "duration @.050", as that indicates how quickly the valve opens and closes, rather than just how long it's open. Obviously, the longer its wide open, the more air will flow between open and close, but the more stress it puts on the cam, and valve train as a whole. I'd have to guess there's a limit to how fast one can close a valve without inducing valve bounce, or, at least, leaving the valve lofted "off-cam". I remember seeing a video from a company that discussed the science of this very thing, where they strived to approach zero spring pressure during valve closing, but not losing contact between the valve, rocker, pushrod, lifter and cam.

Thanks. Brad.

Brad Christy

Guys,

Playing around with a couple online cam simulators, and I keep coming up with the same thing. Punching in the numbers for the stock HO cam produces a negative 3° of valve overlap, meaning both valves are closed for 3° of rotation. Is this the case?

Thanks. Brad.

SB

Do a search under my name. I have written a lots if info / comparisons on black and blue motors’ cams overlap at .006” and overlap at .050” including how much is btdc and atdc. Crane said most important fig on reversion is overlap at .050 atdc.

Brad Christy

SB,

So, now that I've gone down that rabbit hole.... From everything I've gathered, as long as the exhaust valve closes at or before TDC, reversion is essentially impossible. Correct?

This is what the builder is proposing, in light of my concerns of reversion/SilentChoice. We are discussing turning up the wick on the ProCharger to 5lbs. I fully understand that boost is totally irrelevant at idle, where reversion occurs. Ignore the lift numbers. They were defaults that I didn't change. Otherwise, what would you think of these numbers?



Thanks. Brad.

SB

116LSA (lobe seperation angle) ? Never seen that tested. Interesting.

Brad Christy

SB,

That sounds like a “Don’t do that”…

It should have been 115. How do you think it would be re: reversion? I’d think the EC 1deg BTDC would eliminate the risk. Yes/no?

Thanks. Brad.