Jos,
Congratulations on getting your pride in the air, and safely back onto the
runway every time!
I, too, had significantly lower temps on the two front cylinders than on the
two rear ones, until I realized that the cause was mainly air cooling of the
front temperature sensors. I have the Grand Rapids EIS with ring type
thermocouples, too small to put under the spark plugs so I have put them
under bolts where the two Rotax VDO senders otherwise are fitted, plus under
bolts on the two other cylinders. I cured this problem by insulating the
thermocouples (on all 4 cylinders) by red, heat resistant silicone from
Locktite, smeared liberally on the exposed parts of the thermocouples after
fitting and on the bolt heads and immediate surroundings.
As an example, this morning's flight showed the following (912S, cooling
shroud, sealed):
- Outside air temp: 17 C
- CHT Cyl 1-2 (front): 62 - 69 C
- CHT Cyl 2-3 (rear): 73 - 76 C
I have also noticed that the four (2 x 2) front fitted spark plugs have
signs of running colder than the rear ones.
Since you have thermocouples under the spark plugs, which are recessed into
the cylinder heads and therefore more shielded from direct air cooling, your
situation (and possible cure, if due to same phenomenon as in my case) may
be different.
Last winter I installed the oil thermostat approved by Rotax, since my oil
temps where too low even when blanking off 50% of the cooler (need some area
open for the cockpit heat intake). Works very well, oil temp always abt. 95
C in cruise (i.e. above 100 C when returning to the oil tank, which is good
for water evaporation). Today, at top of climb of 2000 ft it reached 100 C
(highest CHT 109 C). I use 50/50 water/glycol.
Regards,
Svein
LN-SKJ
----- Original Message -----
From: "josok" <josok-e@ukolo.fi>
Sent: Tuesday, August 21, 2007 9:32 PM
Subject: Europa-List: Re: First solo
>
> Thanks Raimo, and all the others who answered in email or forum.
>
> Yes, at least in our conditions the exceptional cooling system Pertti came
> up with, seems to work. Today i climbed at 100% power to 9500 feet, OAT -5
> and had 120 C on oil, don't have a coolant meter, the hottest CHT was
> around 130 C under the spark plug. Then on 55 % a long descent, lowest oil
> temp was 65 C. 0 % power will probably produce lower temps, but i forgot
> to try that for some reason :-) There is however an annoying difference,
> especially on climb out between the front 2 and rear cylinders. Today it
> showed 40 C difference. Number 3, above the turbo and air inlet is always
> the hottest. I suspect the naca scoop and the shroud over cyl 3 to work
> against each other. Maybe i have to close the gap around the air filter in
> the air filter chamber. Anybody to offer any insight before i try?
>
> Regards,
>
> Jos Okhuijsen
>
>
|