Date: Wed, 16 Aug 2006 21:38:07 -0400
Reply-To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject: Re: Carb conversions?
In-Reply-To: <20060817012002.11815.qmail@web37410.mail.mud.yahoo.com>
Content-type: text/plain; charset=us-ascii
My comments were meant mostly to compare aftermarket kits to OEM
installations. Many vehicles had carbs through the 80's. Almost all from 81
on had these carbs somewhat computer controlled to support the O2 sensor
which was needed for the 3 way catalyst for NOx reduction.
Carbs can be good and they have their place. I just don't think the kits are
a fix for lack of troubleshooting.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Mike Rouby
Sent: Wednesday, August 16, 2006 9:20 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Carb conversions?
Hi Sudhir,
In these VW applications, the kits are made for the VW engines specs, so
they're not far off and can be dialed in with relative ease (unlike your
generic carb in a custom app). A V6 90 deg stock Rochester carb would've
ran really good in your case.
Another thing to consider is that while you may not feel that carbs do not
belong on modern engines, consider that VW sold these engines in Europe with
carbs (both air-cooled and water cooled) for sometime. Only the US market
got EFI from early-on.
Sudhir Desai <sudhir.desai@GMAIL.COM> wrote:
I ran carbs on my 3.4liter chevy conversion. I would never ever want
to subject other people to the problems of which I ran afoul.
One of the fun problems was a very rich condition at idle which
created a perfect mixture at WOT. If I rejetted the carb for proper
running at low throttle/ low speed, I would go into fuel starvation at
high rpms (not a good thing).
Another problem was that I had to change up the rods and jets to pass
emissions. I was lucky that I purchased an Edelbrock carb with their
easy change fittings.
~I don't mean to totally da byen on anyone, but I really do not feel
that carburation belongs on a modern automobile.
For the same price, you could build a Megasquirt. :)
Sudhir
On 8/16/06, Mike Rouby wrote:
> Dennis,
>
> Many valid points. Some of those you make sound a lot worse than it really
is, but granted the 'potential' is there for such issues.
>
> As for the "preheat" issue with center mounted carbs, Weber makes a remote
snorkel to suck heated air and resolve this issue. If you live in a cold or
rainy climate, I would highly recommend one. Plus in the Vanagon application
it may allow for better fitment anyway.
> http://www.jameng.com/products/images/99217.090.jpg
>
> I take it you're an EFI fan. Thanks for the counterpoints. Most
appreciated.
>
> Dennis Haynes wrote:
> I have had experience with many carb set ups for many cars over the years.
> While carburetors appear to be an easy solution to FI issues there are
many
> drawbacks. Worse, most conversions do not address issues that OEM carb set
> ups used as early as the 60's. Most kits are strictly, make it run,
limited
> use fair weather installations. Here is a list of features most kits for
> VW's are lacking.
>
> Throttle Dashpot or positioner! When the throttle is closed for idle,
direct
> vacuum is used to draw a fuel mix through the idle circuit. If over
running
> the engine such as going down hill, this device delays throttle closing or
> may even hold it open so that fuel is not directly sucked into the engine
> without some air for it to burn. Can we say backfire, raw fuel in
cylinders,
> black smoke?
>
> Choke pull off/Heater! Moist after market either do not have chokes, or
the
> choke is operated by heater element, not engine temperature. Further,
start
> engine for short time, shut off while choke is still closed and throttle
> held open and gravity will empty the fuel bowl directly into the cylinder
> with an open valve. On the type 2, this is real fun as the entire fuel
tank
> can drain into the engine. BTDT! Can we say Hydro-Lock?
>
> Idle Shut Off Solenoid! I like the lack of this one. Yea, go turn off the
> engine. After a long hard run, Hope you a manual trans so you can pop the
> clutch in gear and get it to stop Dieseling!
>
> Manifold heat! This is a real problem in winter with center mounted carb
> kits. The fuel will sort of puddle in the manifold. Can we say flat spot?
> Oh, no intake air preheat either. You drive along for 10-15 miles and the
> engine just stops. You coast to the side and a few minutes later it runs
> again like nothing ever happened, for another 10 miles. Vaporizing fuel +
> what? Refrigeration. Add moisture in air and can we say carburetor icing?
>
> EGR ports! Air cooled Vanagons will miss this one. Excess NOx, burned
> pistons.
>
> How about proper porting for 2 stage distributor advance?
> Crankcase Breather the works?
> Fuel Vapor control!
> Air filter with adequate flow and the ability to trap dirt!
>
> Oh, I can go on.
>
> Dennis
>
>
>
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