Date: Sun, 24 Oct 1999 10:11:08 -0400
Reply-To: Bob Donalds <bostneng@FCL-US.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Bob Donalds <bostneng@FCL-US.NET>
Organization: Boston Engine Exchange
Subject: Re: Questions for the Engine Builders Re: high lift rocker arms
Content-Type: text/plain; charset=us-ascii
CARY CHIANG wrote:
>
> Dear Builders:
> Please have patience with me, and hold the flames till I'm done...
> I seem to recall that a VW magazine this spring did an article on high lift
> rocker arms (maybe Fast German's?) on a modified Bug motor. The before and
> after dyno tests showed a maximum improvement of about nine HP at about 4500
> RPM (I think). My recollection of details is sketchy because I wanted to buy
> the rockers for my Westy but became disillusioned by the test results and
> discarded the article. Anyway, did anyone else read that article and can
> confirm my numbers? I realize a waterboxer is not a bug motor, but aren't
> they similar enough to draw a comparison (My ignorance of cam profiles, valve
> sizes, cylinder displacement etc. of the two motors not withstanding)? Are
> not the performance rocker arms the same? Forgive me for asking questions
> without knowing all the facts, but bottom line; is 9HP gain on one test versus
> 22HP on another using similar(?) motors reasonable, or am I all wet?
>
> Cary (Ready for the flames, 'cause its a dry heat!)
>
> Robert Lilley <Wolfvan88@AOL.COM> wrote:
> http://www.volks-motorsports.com/
> http://www.volks-motorsports.com/C-R_DynoManufacturer.html
> http://www.volks-motorsports.com/NewDynoResults.html
>
> If you look at the chart, adding the rockers "ONLY" added 22 HORSEPOWER at
> the wheels...
> (90HP + 22HP= 112HP A 25% increase in power on a STOCK engine)...
>
> Imagine the HP AFTER COMBINED with ALL the other mods I made...
>
> SO, adding 45% might NOT BE SO HARD after all folks...Plus with no additional
> stress only reduced stress on engine...
>
> Heads
> Cam
> Exhaust
> Crankshaft
> Flywheel
> Fuel pressure regulator
> Lightened valve train
> Ratio rockers
> Use of synthetic oils
> Friction reducing coatings
> Throttle body
> Match porting intake and exhaust
> Air filter changes
> Blueprinting parts
> Adjusted timing
> Plus CAREFUL assembly...
>
> A lot of little changes add up to a bigger change.
>
> Robert
>
> ____________________________________________________________________
> Get free email and a permanent address at http://www.netaddress.com/?N=1
Cary and the list
Adam wilk and Dean Kirsten Did a dyno test article with a new
stock scatt mexican
dual port engine in the March 98 hot vws. I used there numbers to learn
graph plotting on excel and although they did not mention it the engine
had compression ratio of 6.6 to 1 and they also left out what the oil
and head temps were for each test a varable that is to important to
leave out because I feel its important to say at what temps these
numbers where made at. Cooler head temps make more power always!
the total numbers of power output from the wilks testing where about
10% higher than the numbers I got so you cant compare differant dynos
and sessions to each other except in the most general terms
the idea of dyno testing is to change one thing at a time for
comparison. the wilk testing often had more than one change at a time
plus when I compare there graph to all the dyno tests I have done they
are very straight and uniform unlike my graphs. I cant help but find
this more than a liitle suspicious.
So what can we take from the testing thats usefull to waterboxer the
gain from the ratio rockers was aprox 10% thats consistant with the
testing Ive done on aircooled engines with dual kadrons and a stock cam.
the 1.9 engine has the same cam as the stock bug engine but the 2.1
engine has what I would call a hydraulic cam it has a pointy lobe more
lift and small change in the timing see Per Lindgrens web sit for the
diff specs on the 1.9 verses the 2.1 camshafts at
www.http:/menbers.tripod.com prelindgrin/ have not profiled the 2.1 cam
yet so I cant say what the duration is. the camshaft duration is
important to the drivablity of the engine and more important to the
power it makes. so it might be that the 2.1 cam can do better with the
high lift rockers but lift is only a small part of the picture. high
lift rocker put more strain on the valve guides the vanagon engine is
famous for eating intake guides they are short very short. everybody
must have heard about the cloud of smoke that some vans make in hard
turns its the intake guides.
high lift rocker also require more spring tension and on the testing I
did the heavy springs took 1/2 the gain made from the rockers for a
total gain of 3 hp. yes waterboxers have already got dual springs but I
feel its not enough for the ratio rocker
So lets apply some of this to Robert Lilleys engine mods do the
coatings used make the cumbustion chamber temps lower or higher? Im not
sure. Does the exhaust breathe better coated not if its hotter on the
inside of the pipe not in my mind. Do the rockers and the chip that are
mentioned make huge gains? maybe as part of the over all picture but not
alone. the cam used by Lilley was not a stock 2.1 and it may come to
life with ratio rockers because it has more duration. finaly if the van
is tested on a chassis dyno we would need to test at the same time on
the same dyno a van with a stock well tuned fairly fresh engine to
compare all the numbers too or the numbers by themselves dont mean much
I for one am looking forward to seeing the results
Boston Bob
www.bostonengine.com
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