Quote:
Originally Posted by Gaz64
Hi Ed,
I like your thinking, and I enjoy reading your posts.
If, under boost, (15 psi in this case), we could double the air packed into the cylinder before the intake valve closes, then we "could make" double the power.
But with 12.5:1 compression, would you then think it would detonate itself to bits? Or the ignition timing has to retarded so much that the compression increase is hardly worth anything?
Note that they are running .900 valve lift, since the heads are the restriction to power.
Considering it makes nearly 800 on 12.5:1, I would be happy 1000hp on 9.5-10:1 on 15 psi for a street car. Imagine the manners, something your wife or good friends could drive with 5 psi.
Gary
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Thanks for the kind words, Gary. I could be wrong but I don't think I am when I say they will have to drop the compression and pull timing if they run any significant boost over the 8 psi number. At 8 psi (1.5 Bar or 1.5 atmospheres) the 12.5:1 compression will look like ~18:1 compression unless they stretch out the intake valve closing point.
Without reduced timing, an 18:1 c/r even for brief periods of time will severely detonate on 93 octane, It is possible to both stretch out the closing point on the intake cam and also drop the timing to likely be able to reach a detonation free space for say 2 seconds or so in the middle and upper rpm but the compromised timing will cost some horsepower down lower but still possibly put a big number up top.
My instincts say go to an 8.5:1 c/r run 2 BAR of manifold pressure, reasonable timing (very small retard), no delay or a very small delay in intake valve closing point and you should get pretty impressive numbers across the board.
The normal decrease in low speed throttle response and engine torque and an 8.5:1 c/r with a PD blower will be all but unnoticeable. With the immediate boost availability the PD design provides, the 8.5:1 c/r will immediately look like 17:1 compression. That's the good news. The bad news is the 93 octane has as much trouble with the 17:1 c/r as it has with the 18+: 1 c/r and it will most likely require some sort of crutching in the intake valve closing position and also the ignition timing.
I think it might be possible to soften the rate at which the timing comes in and also delay the intake valve closing on a decay style curve where the higher in the engine speed you go the greater the ignition timing and earlier the intake valve closing. this is the kind of stuff the ICE engineers and their first cousins down in the dyno cells are really good at noodling out — guys like us take more time and sometimes use a couple of parts up to get to the same or similar space.
I think the Godzilla may be the biggest bang for the buck (power-wise) in the entire Ford engine line up today. I really am interested in this next build phase they intend to put the engine through. I hope they are clear about things like c/r, timing and boost. Great engine at a very opportune time, love to see it with an aluminum block and heads.
Ed
p.s. Almost forgot. Your observation about the 0.900 lift cam could not be more on target. It is possible with the PD blower they might be able to soften the cam profile a whisker or so providing similar power potential while improving reliability.