Patrick, I am intrigued by the oxygen sensor and fuel/air ratio meters.
What sensors did you use and where did you mount them?
-----Original Message-----
From: owner-spitfires@autox.team.net
[mailto:owner-spitfires@autox.team.net]On Behalf Of Vic Whitmore
Sent: Tuesday, May 08, 2001 11:55 AM
To: Bowen, Patrick
Cc: Spitfires Maillist; pettisw@ms.nidcd.nih.gov
Subject: Re: Weber DVG venting the crankcase
Drawbacks? None that I know of yet. I took the car out for a "spirited"
drive
last night and as I alluded to in the email, the performance was noticeably
better. Part of this would be attributed to the Weber DGV, part to the
porting
and polishing, and part to the new exhaust. If you wanted to see if there
was a
performance difference due to the PCV, you could just remove and plug the
line
to the manifold and test drive it. Of course, you would have to tolerate the
oil
mess while doing it. I doubt you would find any difference as there is
really
not that much draw from the crankcase compared to what is coming in through
the
carb throat.
The drilling and tapping was pretty straight forward. Since the manifold was
aluminum, it was easy to work on. I don't advise doing in on the car as the
metal bits from drilling and tapping will fall into the intake passage. NBD,
as
you can vacuum them out if you have to do it this way, though.
As to the PCV valve, I don't recall the specific car but it was a small 4
cylinder type, probably a Nissan. I just looked through the display at my
local
Canadian Tire store and picked one that suited my needs. I'll look for the
package tonight and let you know which car is was designed for. Maybe I'll
pull
the valve out and take a photo of it for the web site too.
As a side note to everyone, you may have noted that I have an aluminum valve
cover. It has a vented cap on it. Although things seem to be running fine, I
intend to plug the small vent (about 1/8") as it could lean out the fuel
mixture.
There were many unknowns in my project as to how everything would work in
the
end. I wanted to remove some of the doubts and have some empirical
measurement
to base any actions on. So as part of my project, I have installed an oxygen
sensor and fuel/air ratio meter. Now I can see exactly how things are going
as I
drive. At idle, the mixture is rich (good). Cruising at 50 mph runs fairly
lean
(good economy). Under acceleration, the mixture goes rich (good
performance). I
am amazed (amused?) at how much variation there is in the mixture ratio
accross
the driving conditions. It isn't cut and dry 14.7:1 all the time. Trying to
get
a steady reading under one condition is difficult unless you can find a long
flat road for testing. I'll be monitoring this to see if any jetting changes
are
required, but it looks good so far.
Vic W.
"Bowen, Patrick" wrote:
>
> Great article by Vic, Thanks. I am wondering are there any drawbacks to
> doing this? I know the original setup feeds back into the carb as well,
but
> will this affect performance? Also how hard was it to drill and tap the
> hole (READ, what can I screw up doing this). Vic, you said you found a
pcv
> Valve the screwed in? I am not used to seeing those, can you give me the
> part number or car it came off.
>
> Thanks,
> Patrick Bowen
>
> This link will take you directly to the technical page:
> http://www.vicwhit.com/spitfire/spittech.html
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