It's Difficult To Make Hard Heads "Soft"
There seem to be more people each day that only understand "old technology"
regarding superchargers and the actual combustion process. Perhaps a history lesson is in
order, however, attempting to educate those who have brainwashed by the "old
school", is pretty much a lost cause and in the timely words of Pat Ganahl, "If
you don't listen…you're probably going to get beat."
Some folks simply do not understand blower or supercharger technologies. Roots blowers
have been around for a century now, so the "blower" process is hardly new.
Supercharging with Roots style blowers has been associated with automobiles and high
performance engines since the very early days of their inception. Over the years, other
forms of forced induction have become somewhat more popular due to higher specific
efficiencies in their particular applications and environments.
When thinking of Roots blowers, most have always pictured the units designed and
manufactured by GM. One look at a Funny Car, or Top Fuel engine and one's vision is
immediately drawn to that "big thing" on top of the engine. They work very well
in these chaotic applications where fuel is run through the blower, as well as directly to
the manifold runners and ports of the cylinder heads. Are these blowers efficient? No way.
Eaton's redo of the old Roots changed everyone's thoughts about this type of blower
almost immediately when introduced to the industry in the mid 80's. One reason that they
were so readily accepted was the fact that Eaton has been a member of the Detroit Mafia
forever, and the big 3 have no reservations in dealing with them. The other reason is the
simple fact that Eaton's new "twist" on the design produced previously
unheard-of efficiency combined with inexpensive costs.
Efficiency with blowers is comprised of several noteworthy performance areas: package
size, less parasitic drag on the engine crankshaft, greater specific output (CFM), and
less heat generated producing the "boost". Now, there's no question that
generating pressure does cause heat build up in whatever media you're compressing. If one
simply applies old thought to this dilemma, why was Eaton able (after a century of
development) able to produce a unit that does it all so well. Perhaps the engineers at
Eaton felt that the "old notions" were exactly that, and if totally reexamined,
the efficiency could be improved. The point is that they didn't stop development because
"the book of experience" said you can't do better. So, perhaps if Eaton was able
to produce greater efficiency and lower charge temperatures with a production line
component, there could still be some more gains out there in a low production unit,
especially if "the book" is ignored. Hell, if Columbus had read "the
book", he'd have never attempted to sail laterally.
Bottom line is that the overall efficiency of superchargers will continue to climb,
and, perhaps the rules governing mechanical compression will eventually need amending.
Now, lets talk about compression ratios a little. This seems to be an area that some
portions of the IR community are really struggling with. I'll attempt to shed some light
on this and should it fall on a few receptive ears, perhaps some won't be doomed to
"old technology" forever.
Over the course of history, there have always been limits that have been placed on
performance. The four minute mile, the sound barrier, etc, etc. They have all fallen and,
in many instances, most people have, fortunately, never looked back.
If the "old" formulas regarding compression ratios and detonation are set in
stone, why can modern engines run more efficiently than old valve in block engines?
Compression is compression and the pressures are the same, right? How were NASCAR engines
running 19-20 -1 compression ratios (before rule limits), when the gas and overall engine
configuration haven't changed for 20 years when 12.5-1 compression ratios were the limit?
Once again some of the import crowd have chosen to read the same old worn-out book and
ignore what differentiates their cars' engines from less sophisticated others… The
shape of the combustion chamber. It's amazing how folks who rally around such
sophisticated engineering can at the same time be locked into believing rules that no
longer apply to pressure and combustion, perhaps it's a result of spending too much time
playing with "computer engines", rather than paying attention to the real thing.
Please don't infect the professional racing community with, "stop development, the
rules say we can't proceed any further" ideas.
Why are some engines able to handle higher compression ratios than others? Engines have
fortunately never read those "old books", and defy the "old rules"
regularly. The reason is "shape dictated combustion." Compare a thirty-year-old
head configuration to a contemporary Honda cylinder head. Do the chambers look the same? I
doubt it. But wait, the mechanical geometric compression ratio is the same, so they should
detonate at the same time and each should only tolerate the same amount of boost according
to the book that you folks have chosen to read. Once again, don't tell the racing engine
builders about that book, or we'll be running speeds that are reminiscent of the 50's.
If the combustion chamber and piston are correctly configured, the amount of static
compression is almost without limit and the detonation resistance can be almost limitless
as well. The quality of the inlet charge is admittedly important, but if an engine running
a manifolded 4 bbl. carb can run 20-1 CR, it's safe to think that a port injected engine
could be even more efficient. If we run 16-1 to 18-1 in street engines without detonation,
it must be luck. We don't even measure the mechanical compression ratios of most engines
we build, as the chamber / piston dictate detonation tolerance, and the CR numbers are
next to useless. Our typical blown engines have CR'S over 12-1, and they still tolerate
over 20 psi and love it. How can it be? Perhaps, had you all ever read about, or worked
with engines producing 1hp / cc of displacement dependably on gasoline, you wouldn’t
be so reluctant to look to "other" sources of information.
Enough of the static compression stuff…it's not worth any more time. The place
that this market has really missed is that of dynamic compression, or cylinder pressure.
Now, if you want to talk CR'S, begin with something meaningful for a change, as the static
ratio really doesn't mean beans when dealing with the real world.
It's very easy to build an engine with 30-1 CR that'll have the same dynamic CR as an
identical engine with 9-1. You folks have apparently completely forgotten the role that
the cam and the head's breathing ability play in this equation. The camshaft and breathing
capability controls the dynamic compression ratio and the static ratio has little to do
with anything, when comparing apples to apples. Static compression is only meaningful if
the engine is not running and the last time I checked, static engine stats don't mean much
in the real world and the only races they win are static as well.
During the early '70's when gas quality and availability were equally poor, Crower and
numerous other companies introduced piston and cam kits for SBC'S that raised static
compression ratios to 15 to 1 and the engines were extremely tolerant of the gasoline
quality. The reason that it worked without detonation was the camshaft design. So if you
folks want to really discuss the "real world", the issues that count for
"real" should examined and static compression ain't one of them.
Dynamic compression ratios these days are "what combination works best"
(unless the application is a game where "make-believe" engines compete on a
computer screen). Driving cars powered by computer games is about as rewarding as racing
dynamometers and flow benches, so don't count on making any prize money.
If nothing else, you owe it to yourselves to delve deeper into the "real"
workings of a high performance engine. The people who are feeding all you this
"old" data would surely be offering some cutting edge components to all forms of
motorsports if they were really on top of modern technologies. I fully recognize that
certain brands of import cars wouldn't be sold in the US had it not been for their hard
work, but their recent conservative performance indicates that they have fallen far behind
the curve of today's technologies.
There will be several articles which will more thoroughly address the specific topics
brought forth on this commentary and we feel that many are going to be in for an eye
opener, and perhaps a bit of mind opening as well.
As far as controversy regarding our concepts go, it should be apparent to most that
there's not a whole lot that we do that's not controversial, and were it not, we'd be back
in the middle of the pack with the other also-rans. Time has proved our innovations'
validity time and time again, so take your best shots, cause our record has always been a
winner.
- The Old One, May 1999
