Date: Fri, 29 Mar 2002 10:34:41 -0500
Reply-To: Robert Donalds <bostneng@FCL-US.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Robert Donalds <bostneng@FCL-US.NET>
Subject: Re: Performance Cams.....to cam or to ratio rocker....that is the
question
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Subject: Performance Cams.....to cam or to ratio rocker....that is the
question
> Robert and all other gearheads, ....first of all thanks to Robert Donalds
on
> all his work with performance upgrades....I know I'm a pain in his
> side....
but.
> Here is my question:
>
> Let's say one wants to get the benefits of ratio rockers without putting
> ratio rockers in and suffering excessive side load on the valve guides.
>
> The stock 1.9L cam grind is different than the 2.1L......But what is the
> lift and duration differences of each cam?
> Does the 2.1L cam profile work with digijet well?
The stock 2.1 does have more duration and lift
The 1.9 cam has the same profile as the bug with a harder gear. The total
lift on 1.9 - bug cam measured at the intake retainer is around (323ths)
(corrected for previous post) with a stock bug - WBX rocker arms. Some after
market stock bug cams have a few ths. more lift.
The 2.1 cam total lift on measured at the intake retainer is around 355 ths.
The 2.1 cam is also opens at .040ths lift 12 degrees sooner than the bug -
1.9 cam
I think that means the 2.1 cam has 24 degrees more duration than the bug -
1.9 cam
Web Cam say the difference is 26 degrees duration
> Can one duplicate the lift and duration of ratio rockers if one maps out
> the lift on a motor with ratio rockers
> and puts those numbers onto a cam.....therefore eliminating the need of
> ratio rockers?
The short reply is yes you could the reason it is not done is that Ratio
rockers a used for the most part by those who chose not to split the case
and change the cam
If you want to change the cam you would want more than just more lift as the
ratio rocker offers
The cam lobe if you spent the time to profile it with and without the ratio
rocker would be taller and only slightly wider at the top part of the lobe.
This would be good for top end and hard on the valve seats and guide the
valve would slam shut due to low spring pressure this would be considered a
poor redesign with little value
Adding lift and duration increase top end at the possible and likely expense
of the low-end power and transition to mid range. This is where matching
components is key to making more power threw out the range and retaining
drivability
> With ratio rockers, what is the lift and duration profile?
Again more lift and the same duration
> Can a cam be ground to those specs........to duplicate the retainer
movement
> without actually having ratio rockers?
Again yes but no value in this approach
>
> Is there a euro grind for the Vanagon?....
Not that I am aware of.
>
> Does the Syncro or Syncro 16 have a different cam profile than the rest of
> us commoners?
Non that I have ever seen
>
> Has anyone done a cam profile chart showing lift, duration, dwell etc for
> each cam for the vanagon?
Nothing so complete as to be presentable
I can't share everything
The WBX engine needs a cam that will work with the injection system both
stock WBX cams work with both injection system and the web 2.1 regrinds have
small changes in lift and duration so they also work with the injection.
Tossing in a non stock bug grind will most likely interfere with the vacuum
signal at Idle and mid range and make it impossible for the fuel injection
air flow meter to interpret this in a way that will let it meter the fuel so
as to pass the emissions at idle and above as some states require.
The point to adding a non-stock cam or rockers is to increase power. I
learned along time ago you can only force so much air threw a certain size
hole. Engines are air pumps and the restrictions to the airflow threw the
WBX engine cost or prevent the engine from reaching it potential power out
put. Let me make a list of the restrictions muffler baffles, cat converters,
exhaust pipe size, intake pipe, throttle body size (The 1.9 intakes system
and air flow meter is also much smaller). I would add to that air intake
temps it not a restriction you can hold in your hand unless you have removed
and are holding in your hand the cardboard hot air block off where the air
filter intake pipe exits the engine compartment. The next restrictions are
the intake and exhaust ports. Then the valves making the airflow around
these is tricky and the one place we want to influence the air flow the
most. The intake is bigger to let more charge in the exhaust valve is
smaller to restrict the flow out to the exhaust. This is done to keep some
old heated combustion gases in the combustion chamber and to influence the
direction of the exiting gases.
The best way to make a broader power range with an other wise stock engine
and not confuse the injection system is to establish air flow at lower lifts
and in doing this create momentum early on and build on that momentum as the
valve opens the result is a larger charge per breath taken each time the
valve open. This is known as the competition valve job. I have a friend in
the Heating and Air conditioning business he called this making the air
smarter. Thank you John
The air in the WBX heads and around the valves does not flow that
thoughtfully for lack of a better word. Or as I would say the stock WBX
heads don't flow worth crap for the first 200ths lift and the max lift is
355 ths or so. Check the air flow charts by going to my engine price list
and click on the link in the stage 3 engine description this chart show the
different air flows at different valve lifts for stock heads, head with
competition valve jobs, and heads with 3MM larger valves. This chart also
shows the lift you would get from ratio rockers at the different lifts. The
stage 3 heads flow chart are done on the heads in my own 84 2.1 engine. The
valve job is not just a milti angle valve job but instead is formed with a
one-piece carbide cutter that lets me do so much more than single angles
will allow. The port sizes in my heads have remained the same over all with
some mild shaping of the corners. I have spent the time and the money at the
flow bench to optimize the airflow. The bigger valves alone won't produce
these results the reactions I get when I let a fellow vanagon type drive
it is a subtle and repeated wow as they shift threw the gears.
The vans are unlike the smaller cars you need larger increases in power to
go noticably faster down the road
all rights reserved
Bob Donalds
Boston Engine exchange
http://www.bostonengine.com
