<VV> CHT data

[Roger Gault]

Remember that the VDO gauges are TC gauges, not Thermistors.  So, the VDO
actually reads the temperature difference between the ring and the connector
near the ring (about a foot away as I remember).  When I checked mine, it
looked like the VDO gauge reading assumes that the connector is at about
70F.  So, you might look at where the connectors are, and what removing the
shrouds did to the temperature in that area.  That might explain some of the
wierdness.

Roger Gault

----- Original Message ----- 
From: <AeroNed@aol.com>
To: <virtualvairs@corvair.org>
Sent: Saturday, October 23, 2004 8:51 PM
Subject: <VV> CHT data


> I've heard about lowering the cylinder head temps 50 degrees by removing
the
> lower shrouds. I wanted to see for myself. I have two VDO gauges. The
left
> sender is attached where the thermister goes. The right one is located
under
> the snap switch. With all the shrouds installed, the left temp hangs
around
> 300 and the right around 250. These temps change a little, maybe 20
degrees,
> with outside temp.
>
> Today, I replaced a failed t-stat (repo failed - ULTRA installed) so I
> decided to remove the other lower shroud to do this experiment. After both
shrouds
> were removed, I went for a spirited ride (what other kind is there?) to
get
> the CHT to reach a stabilized value. Sure enough, the left side dropped
50-60
> degrees, just like everyone said it would. The real interesting thing was
> that the right side temp didn't change at all from the 250 degrees it read
with
> the shrouds installed.
>
> I crawled under the car to see what I could see. I'd say that the airflow
> over the heads was the same on both sides. The airflow over the oil cooler
on
> the left side seemed very low. I went for another ride to get more data
(the
> fact the it was a beautiful day and driving the Corsa is lots of fun was
NOT a
> factor <G>). The second ride had the same results.
>
> I'm thinking that removing the lower shrouds on the right side had little
or
> no effect. The "restriction" on that side is minimal. The 50 degree
decrease
> in CHT on the left side is due to reduced airflow through the oil cooler.
I
> don't have an oil temp gauge, so this is just a guess. With the lower
shroud
> removed, the air flows in the direction of least resistance, over the
heads.
> When the lower shrouds are installed more of the air flows over the oil
cooler
>  and less over the heads which is the reason for the higher CHT.
>
> That's just my opinion, I could be wrong....
> Ned
>  _______________________________________________
> This message was sent by the VirtualVairs mailing list, all copyrights are
the property
> of the writer, please attribute properly. For help,
mailto:vv-help@corvair.org
> This list sponsored by the Corvair Society of America,
http://www.corvair.org/
> Post messages to: VirtualVairs@corvair.org
> List info: http://www.vv.corvair.org/mailman/listinfo/virtualvairs
>  _______________________________________________