When putting a new motor in my Mark 1 Tiger one of the other changes
which I wanted to make was the upgrade to a 4 BBL carb and manifold.
Since I had COBRA manifold laying around I decided it would be a
good match to the new cam being used. One of the problems encountered
however, was the Tiger temp sensor would not fit into the smaller
sensor hole used on the COBRA intake. After having no luck finding a
suitable adapter for the sensor, I found a temp sensor used on other
British cars, manufactured by Smiths, Part # TT6811/01, that would
screw right into the existing sensor hole. Taking a resistance
measurement of both sensors at room temperature however showed a
difference in the resistance measurements so a check would need to be
made of the temp gauge readings vs actual temps to understand if the
sensor was giving incorrect readings while in use. Using a Type K
thermocouple and an Omega temperature readout the following data was
obtained.
T/C location- inside upper radiator hose at radiator connection (ie
after the thermostat)
Engine at idle
160 F thermostat used
GAUGE READING T/C READING
START ---- 66
120 88
140 (60C) 102
155 118
170 166
176 (80C) 172
185 179
194 (90C) 190
200 196
212 (100C) 212
225 223
As can be seen by the data, the sensor is fairly accurate at the upper
ranges and the thermostat not being opened could account for the
deviation at the lower ranges. It appears that the above temp sender
is an acceptable replacement for the "real" Tiger sensor, at least on
a Mark 1, when a smaller sensor is needed. However, (time for the
disclaimer), I only tested 1 sensor and while it is probably
indicative of the lot, this has not been tested. If anyone has any
questions or wants to point out errors in my testing let me know.
A final note; I obtained the sensor from JAE in Santa Barbara 805
967-5767. They are Lotus specialists, but carry many British parts
that can be used on Tigers, (ie clutch and brake cylinders, SU fuel
pumps, oil gauge lines, fittings, sensors, etc), and are very
reasonable in price.
Jay Peterson
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