I'm with Proppy on this, but will elaborate. Built a weird blower motor myself, and gotta tell you this , theres a LOT more to it than just the blower itself. Take the sublime warning in Enginedoctors "moron" post. It isn't cheap to do this even HALFWAY right.
Most times we here tend to tell everyone what WE would build or WISH we could build, but in this case theres not a lot of wiggle room. Not only does the bottom end need to be as bullet-proof as possible, head flow, gaskets, o-ringing.......all come into play, then you have the ignition issues, particularly if you're going to run pump gas. Many I know are running severely retarded ignition timing to avoid detonation at everyday use speeds, and CAN crank that up when at...say....the Tom Papp memorial or the Yuma power tour or something speshul running race gas or avgas. Counter productive to my thinking.
Just an FYI, was poking around Mallory's website the other day and never knew this. Their HyFire 6, not the 6A or 6AL, has the capability and special harness available to advance/retard ignition timing based on rpm and boost levels for blown and turbo engines. Can be user customized as well, without some box the size of an 8x8x16 concrete block or require a laptop to program the silly thing.
All that being said, now understand this. PSI of boost is really back pressure measured at the intake manifold. Normal atmospheric pressure is, as I remember it, is around 7 PSI, which would be zero on any boost gauge. So ANY pressure registering on a boost gauge is ABOVE that number, whatever it is. Boost will increase with RPM, basics yes, but when boost numbers get into the rediculous digits, its really showing inefficiency in the system. Now, top fuel cars, drag boats, many more, get into or close to triple digits, but their entire gig is 1000 feet at a time no matter what the cost, with millions of dollars on the line. They also rebuild the motors every run and can afford to destroy a $200+k engine or two. Volumetric efficiency, durability, and low maintenance go completely out the window in applications like that.
I think I had some guy try and challenge me here very recently on this information, and I ignored it, but Proppy and I did a LOT of research on building blown E-85 engines which is what I ultimately went and did. All the physics remain the same, whether on pump gas, E-85, Alcohol, Nitro-Methane, whatever. You will be battling detonation when you are at the edge of your chosen platform. With E-85, Alcohol, or Nitro, you can get away with a LOT more compression and overdrive rates. No matter what fuel platform you build the engine for, if you want to be at the ever loving ragged edge, be my guest, crank the PSI up and replace/rebuild as often as necessary. I think that guy was talking in the 20 PSI range which is CRAZY to me in a pleasure boat, or car for that matter and was asking about using block fill.
I beleive, with a solid engine for the given fuel and platform, at the top of the RPM range, you should be looking at 10-15 PSI on the gauge if you're into performance and rebuilding somewhat often. On a boat, that would be every year unless something stupid happens. For longevity, keep it at 5-10PSI. The HP difference between the two is negligeable IMHO. Still a LOT of planning, building and hardware involved in building a reliable and daily usable blown engine in that category.
Just my LONG .02
Ray
