Now if you want to make some more power cheap, how about a little water
inejction from 4000 to 6000 and then advance the timing three degrees. You
won't have to go deeper into the corner, 'cause you will be GONE.
----- Original Message -----
From: "Jack W. Drews" <vinttr4@geneseo.net>
To: <fot@autox.team.net>
Sent: Tuesday, December 09, 2003 7:18 PM
Subject: cylinder head flow
> The last one was so much fun, let's try another one.
>
> There is a site on the internet that deals with increasing motorcycle
> performance by creating high velocity ports. You can read a bunch of
> articles at
>
> http://www.mototuneusa.com/homework.htm
>
> by a guy who has great success making motorcycle engines perform much
> better by making the ports much smaller at the curve. Read the back issues
> or articles. Basically he fills up the short side radius with epoxy. The
> reduction in port size is startling but he claims that the port velocity
is
> so much higher that more hp and torque are produced.
>
> Well, I tried it on TR4 heads. I started filling the port at the short
side
> radius, and with each step of filling it (reducing cross section), I
> measured flow on the flow bench. What I found was that I could reduce the
> diameter of the TR4 port at the bend (only) from its stock 1-1/2" until it
> was down to 1-1/8" before flow started to drop off!!!!!! I have a
> cross-sectioned head with modeling clay duplicating what I did and will
> send a digital photo to anyone interested.
>
> What conclusions should we draw from this? My own conclusion was that
there
> isn't much air following the inside or short radius. It's all packed to
the
> outside (not surprisingly). So flow stays the same if the short side is
> built up, but just the opposite happens if the short side radius is
> improperly flattened out -- then flow decreases.
>
> Just to close the loop, though, I took my car to the chassis dyno shop and
> ran back to back runs with my current head and with the restricted head.
> The engine had about the same hp and torque with both heads. I can't
> explain this result. Perhaps something else in the system was the
> resticting factor. As I've said before, port work is a very humbling
> experience.
>
> Going back to the Motoman's article where he actually shows dyno curves, I
> see that the biggest gains come between 7000 and 14000 rpm or so, although
> the percentage gain looks to be the same. My tests were run through the
> range of 3500 to 6200 rpm. I don't have a billet crank so that's where I
> run my engine. Maybe the high velocity port approach only works out with
> high rpms. I don't know. I got tired of making chips. However, I did see
> another approach at my local machine shop today that I'm dying to
> try.............
>
> uncle jack
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