<VV> Carb Rebuilding (added...Fuel Efficiency)

[Shaun McGarvey]

This is the kind of thread I wade through BS for years to find. Thanks Mike!

yea, Vairily ... Shaun

----- Original Message ----- 
From: "Jim Burkhard" <burkhard at rochester.rr.com>
To: <Mikeamauro at aol.com>
Cc: <virtualvairs at corvair.org>
Sent: Sunday, May 18, 2008 9:44 AM
Subject: Re: <VV> Carb Rebuilding (added...Fuel Efficiency)


> Mike -
>
> Excellent commentary!  It's good to see somebody making good use of
> modern technology to improve carb tuning techniques.  The Innovate
> products are good ones at a great price -- we even use them at work
> for non-critical development.  They are every bit the equal of the lab
> grade wide range systems offered by ETAS and NTK, with the exception
> of a very *slightly* slower response time.  The difference in response
> time might matter for OEM direct injection, but not at all for carbs
> or even aftermarket tuning.  Keep posting more details on what you
> learn re the carb tuning -- the wide band sensors are much better
> tools than were available OEM engineers in the 1960s.  Watching how
> the carbs perform during transient maneuvers is of particular interest
> to me.
>
> Jim Burkhard
>
> Mikeamauro at aol.com wrote:
>>
>> "...The lower the float level, the leaner the high speed mix. Do not 
>> apply
>> pressure to the needle in the seat when doing this  adjustment..."
>>
>>
>> Actually, checking using wide-band instruments, I've found float  level 
>> comes
>> into play a lot earlier: from just off idle transition, and  throughout 
>> the
>> mid-range. Nearing WOT, I'm sure the fuel level pays a part, but  with 
>> fuel
>> enrichment circuit equipped carbs, once enrichment kicks in, it's a 
>> little more
>> difficult to separate out what can be attributed to float  level, and 
>> what is
>> enrichment. By tweaking (lowering) the float levels,  I've been able to
>> maintain (at around town & cruse speeds), between 14  to 15 A-F ratio. 
>> The car I've
>> done this with is a 110 with PG and dual  exhausts. I've installed 
>> in-cockpit,
>> dual wide band digital instruments (by  Innovate), so I can see what is
>> happening under all conditions,  side-to-side. Before float tweaking, 
>> even after
>> reducing jet sizes to  under OEM speck, I could never get the system to 
>> run
>> leaner than about  13.5. This speaks to the fact that jet size is most 
>> influential
>> under WOT  conditions. Another thing I'm trying, to lean things up a bit, 
>> is
>> to make  the enrichment needles a little heaver: I've filled the 
>> depression in
>> the tops  of the needles 1/2 way with soft solder. OBTW: this and all my
>> other  Corvairs are Safeguard-equipped. If you do not have a Safeguard, 
>> or Clark's
>>  knock sensing device, be extremely careful in your leaning attempts.
>>
>>
>> Mike Mauro
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