All,
I'm such a sucker. If the Hare-Krishna stop me on the street, I will always
politely answer their questions. So now Jim Swarthout asks some questions,
so I'm going to have a bash at answering some of them. WARNING: I'm
probably wrong on most of them, but would appreciate some kind souls to set
me right.
> 1) There were 2 reasons why electronic ignition was developed? Both
> answers pertain to the consumer, or auto owner.
It is cheaper to manufacture, install and maintain. Car manufacturers will
bend over backwards to save 1 cent on an item. An added benefit is that
distributor-shaft wobble is no longer a main issue.
> 2) Upon introduction: Hydraulic Camshafts were touted to be a technology
> breakthrough. Why? Was it really a ruse? Today many people believe that
> hydraulic cams have a grind profile that is far superior to anything
> that could be achieved in a mechanical cam. Is this True or False?
Hydraulic cams were introduced because they did away with the valve re-shim
at 500 miles on every new car. I don9t really know the answer to this, but
I would guess False.
> 3) What does an air pump, (smog pump), do? Explain the entire
> cycle...peripheral equipment!
Sorry, I ripped off all smog gear on my car. The air pump is a notorious
consumer of hp!
> 4) Why will roller rockers of an equal ratio open the valves further?
I thought we covered this in a thread last week? And I'm not convinced they
do. (Nomex suit on!).
> 5) What performance gains will you achieve by installing a long
> duration...(extended period of valve opening)..., high lift, camshaft in
> an otherwise stock engine?
The gains will come at high-rpm, because more gas-air mixture can enter the
combustion chamber than with the stock cam. Air has mass, and it takes a
finite duration to move it. The hi-po cam allows the valve to open wider
and for a longer period of time, allowing this mass to slide on in.
> 6) Why does an early Ferrari have a "true" 5-speed gearbox, but a 2003
> Toyota does not?
Why is an apple not an orange? Trick question? Ferraris built for mountain
passes, and Toys are built for freeway commuting?
> 7) Suppose you have two 152ci TR engines side-by-side; same, make,
> model. One engine has a compression ratio of 12:1 with a static
> compression of 90. The other engine has a compression ratio of 7.5:1
> with a static compression of 200. Which engine would you want in your
> car? Why?
Anyone on this list knows my love for power-bands and zero torque at low
revs. The 12:1 motor of course!
> 8) Is compression ratio related to static compression? Yes or No, and
> why?
Ooops. Better go back and read my books.
> 9) You're speedometer shows 60MPH. You're Tachometer shows 3000 RPM's.
> You're in 4th gear at 1:1 with a final drive ratio of 4:10. What is the
> outside diameter of your tires?
27.56"? (I can only remember PI to 3 significant figures). If that9s the
case, this is pretty close to a 215/70-15 tire.
> 10) What are the differences between a machined part, a forging, and a
> casting? Which is better? For what application? Be specific!
I'll take the machined forged part, please. Forging aligns the crystals in
the metal, for a much stronger part. But that does not mean it will fit or
look any better. Machining puts chunks of stuff on a lathe and turns them
for fit and finish. Sand casting can produce beautiful, but brittle shapes.
> 11) How are engine firing orders determined by the engineers? Is it
> rhyme or reason?
I always figured it was to minimize harmonics in the crankshaft, but I'll
defer to the engineers. But this is a good question: why do BMW & Toy
straight 6s have different firing orders? Length of crankshaft?
> 12) If the piston to be fired is approaching compression...(15 degrees
> BTDC)... and you have the timing set to fire at 10 degrees Before
> TDC...why doesn't the piston travel back down...moving in the direction
> from which it just came...?
Ummm, inertia from all the rotating mass?
Ok Folks, now tell me the real answers! A Man's got to know his limits!
Shane Ingate in Maryland
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