John,
I must not have stated my case clearly. I certainly feel there will be a
significant low rpm horsepower gain. And because of this, increased
performance in Autocross where acceleration is important. I don't feel the
top end increase will be as significant, because engine breathing will be
limited by the smaller valve sizes.
Dick
----- Original Message -----
From: "John Whitling" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Monday, March 05, 2007 10:56 AM
Subject: Re: [F500] Re: FM alert, VEE engine magic
Chuck
I wasn't questioning the rules settings in this case. I was commenting
on Mr Hensley's idea that increasing cubic inches, with no other
changes, wouldn't result in a better motor. My point was that on the
contrary, it results in a better motor across all ranges, not just
something like better peak HP or better peak torque.
Still, it's interesting to learn about the thought processes involved in
engine aspects of the rules changes. Since the new rules have been
published the Vee guys have stayed pretty tight lipped about the motor
changes. Secretly they now smile when they go to sleep at night. Some
are even openly giddy.
Chuck Voboril wrote:
John, we started with pro engine builders and their ideas rather than
the other way around.
1915cc did not originally come from the Solo-Vees nor the MAC.
The idea of allowing a 1915cc low compression motor at the same valve
size and caburation as presently allowed was suggested to us by an
engine builder to economically provide our dual goals to both get
actual peak HP into the 120 HP range AND to also to provide a wider
useable HP operating range ( in response to CVT envy :->).
The simple displacement-only approach also has the attribute of not
requiring race gas.
The current data we have is that all the legal 1600cc motors out there
now have between 90 and 100 HP under the present rules. We hear a few
member claims of 110 HP and then we have the the John MacDonald
stories of 124 or whatever HP.
There are NO engine builders so far that have said directly to us that
they have built a 120+ HP 1600cc motor with 9:1 compression, 39 mm
intake and 32 mm exhaust, and single carb.
If one does simple proportional scaling for HP from increased
displacement with no other adjustments, the 1915cc vs 1600cc would
take 100 HP to 119.7HP.
A usual by-product of increased displacement is increased compression,
but in this case, we are restricting it to the original 9:1. This is
accomplished by using the correct thickness shims between the head and
barrel to adjust the compression (just as can be done on a 1600cc motor)
In practice, with everything else remaiining the same, increased HP is
usually less than predicted by straight proportion due to the
increased frction.
Below are more references, if you are interested:
Primo (a top VW engine builder) has said said with a single two barrel
carb, stock exhaust valves and the rest of the package, the motor
should be the mid to upper 90 hp. He said if somebody did have 120
HP, they would easily be blowing past a motor like this.
Primo also referred to the book he called the "VW hot rodder's
bible". In "How To Hot Rod Volkswagen Engines by Bill Fisher", go to
the dyno chart on page 36. The engine was 94 cc bigger than the
Solo-Vee engine with larger valves than what they have, 40 mm intake
and 34 mm exhaust (Solo-Vee is 39 mm and 32 mm). This dyno report
engine also had dual (dual port) carbs, Solo-Vee only have a single
carb. The test shows the engine's max hp was 109-110hp at 5,700rpm
for only 300rpm then drops off. This is definitely a better package
than what the Vee's have and is still only 110hp.
Now, that said, this 1915cc concept can certainly still be disputed in
the input from the membership process.
I suggest providing your assumptions on the engine build-up and your
engine builder/book sources in your letters.
Chuck
From: John Whitling <[EMAIL PROTECTED]>
Reply-To: [email protected]
To: [email protected]
Subject: Re: [F500] Re: FM alert, VEE engine magic
Date: Sun, 04 Mar 2007 09:44:35 -0500
Richard
I have yet to find any engine builder that subscribes to the notion that
adding 300cc to a 1600 cc motor (all else being equal) won't add peak
horsepower and torque, substantially across the range. Cubic inches is
very much like compression .. it increases not only some peak HP number
but bumps up the entire range. If you find that engine builder I would
like an email address or phone number so I can hear him say it.
The MAC's resident tech, Chuck, may want to weigh in on this claim you
make. Maybe he can clear up the conception that adding 300cc will not
make a substantially better motor.
[demime 1.01d removed an attachment of type text/x-vcard which had a name
of jwhit.vcf]
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