Re: [T3] Compression Ratio Recommendations

["Shad Laws" <shad@lnengineering.com>]

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Hello-

> From what I understand, the Chrysler Hemi ran better on alcohol than
> gasoline.  

Now you're comparing apples to oranges... and, you have to clarify 
what you mean by "better."

Alcohol (methanol, not ethanol, IPA, etc.) tends to run cooler, 
primarily because of the high latent heat of vaporization and because 
it takes so much of the stuff to use up the air the engine breathes 
(roughly twice the amount of alcohol is used in place of gasoline for 
the same amount of air).

Alcohol also makes more power.  It's a totally different fuel, and it 
burns totally differently from gasoline.

Alcohol has a higher anti-knock rating.  This means that you can run a 
higher CR and/or more boost or whatever else and still avoid 
detonation.  To help this further, alcohol doesn't bog down the engine 
as much as gasoline when you run way too rich.  This can be used to 
make it even harder to detonate under tons of boost or something.

With regard simply to thermal efficiency alone (which is what my post 
was aimed at), if you took a gasoline engine and with no modification 
other than CPU reprogramming and/or rejetting, changed it over to 
alcohol, you will find that thermal efficiency itself drops.  If you 
go through and calculate the ideal heats of combustion for methanol 
and then gasoline, then take note of how much the engine uses for each 
fuel, you'll find that to make the same power with alcohol, you need 
to take up more stored chemical energy.  What relevance does this 
have?  Well, if your goal is high thermal efficiency, a lot.  If your 
goal is power, you probably don't care :-).


> I agree with most on Berg's principles.  He was right on most things
> back in the 60's and 70's, but todays knowledge and technology has
> long surpassed his theories.

I know I'm going to be flamed for this...

The only principles of Berg's I've agreed with are those that are dead 
obvious.  Most people already knew the ones he was correct about - he 
just put them together in a book as a part of his marketing.

Here are my general good and bad points on Berg:
-never succombed to cheap 3rd-world labor (all kidding aside, I give 
the devil his dues here - IMHO this is his single biggest plus)
-excellent marketer - he knew how to sell stuff
-didn't have too much remorse in bad-mouthing competitors products, 
even if superior, to make a buck.  Good marketing, but I don't agree 
with this practice.
-didn't have much of a technical background.  Combined with his 
marketing plan (talk loudly), this made for a lot of bad 
recommendations.

Just some quick thoughts of things he loved that I simply can't 
understand:
-ultra low CR
-semi-hemi heads
-DCNF carburetors (cornering even at regular speeds sucks... BTDT)
-dual carb linkage bolted to the fan shroud (which moves and vibrates 
entirely independently of the carbs...)
-5-speed trannies that require his special shifter ($$$) instead of 
having a simple centering spring to keep it in the middle of the H-
pattern with no force on the shifter like other cars... there are 
other design flaws in his kit, too... but his competitors got slammed 
by him <shrug>.

(getting out the fire suit)


> I really am enjoying this thread and appreciate the shared knowledge
> from Shad and John.  So Shad & John, what I need then is Shad's 94mm
> Birals with John's Superquench pistons, awaiting a good aluminum 
case,
> solid forged 84mm crank, h-beam rods, and a good cam....hey how about
> a roller cam.  What is anyones opinion of those?  And what heads? 
> Aftermarket fuel injection?
> Boy, I hope I have enough time to save enough money to build it this
> winter!

What you need all depends on your budget and your application :-).  
EVERYTHING hinges around these points.  Realistically, how much money 
do you want to spend?  What vehicle?  What purpose?  What life?  What 
do you want out of it?  

Take care,
Shad Laws
LN Engineering
http://www.lnengineering.com

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