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Old 22-03-2005, 06:41 PM
max_torque max_torque is offline
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Default Resevoir level sensing in a competion environment

Does anyone have any experience of using water resevoir level sensing systems in a competion (specifically rallying) environment. My concern with a float type arrangement is with it's durability under high G loading, and accuracy under negative G conditions (ie when car is flying!)

I plan to use an optical sensor (IR reflectivity prism type), and to damp the output by some margin to determine a "true" water tank empty signal?

Also does anyone use a "dry pump sense / auto prime" logic to detect when the system is empty and if it needs to be primed? My concern here is that if i run out of water, and the resevoir is refilled in service, it's easy to forget simple things like checking the system is primed. This could be a particular issue for me becuase to optimise the vehicles CofG the tank is mounted under the drives seat, both low in the car, and a relatively shallow design of tank.

Inital thoughts were a "key-on" routine, involving opening a low back pressure return line (via solenoid) that is T'd from directly up-stream of the HSV, then running the pump for say 10secs, (returning any water back to the resevoir) closing return line, then deciding if another prime sequence is required by the systems pressure rise response. In conjunction with a no-water / system fail error light, that would illuminate after a certain number of failed prime attempts, this should guarentee a propely operative system before leaving service????
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Old 22-03-2005, 09:03 PM
Richard L Richard L is offline
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I did some work on the in the early 02 devising a feed back system to purge the air out of the water line duringin racing condition but never got further then protoyype stage - the engineer moved to another team and the project was shelved.

The detection of water level in the tank is not as critical since the accuracy of signal from the sensor is not consistent under racing conditions due to the g-force. So the only way forward is monitoring the water line pressure against PWM of the injection valve. The pressure pulse on the line, however small, should have a direct correlation with the opening time of the water injector valve.

In the presence of air, the two signals fall out of sync, a secondary valve will open to purge some of the air out of the system whilst switching the water line to a charged accumulator and keep the water supply going.

The same system can perform the task at start up - normally done manually by a navigator pressing a purging valve when a warning lamp comes on.



The optical detection system is good but complex - as mentioned, you need some smoothing circuitry.
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Old 23-03-2005, 02:50 PM
max_torque max_torque is offline
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Thanks for that insight, i guess my main concern is not actually getting an aerated water feed duing operation (i have a small "swirl pot" that is filled by a lift pump, this swirl pot is tall and thin, and mounted vertically, and should easily centrifuge out any air picked up from the main tank during cornering etc), but to ensure that the system will always be ready for operation at the stage start, minimising the time delay/error between a comanded water flow and a real water flow quantity.

My main concern was to "idiot proof" the system, all my experience of motorsport to date tells me that most errors are human, and could be easily avoided by better system design / integration. Complexity as such is not a major issue, but reliablility is, so the system needs to find the balance between these too. I suspect that solid state electronics, if properly designed and integrated are more reliable than a stressed service crew, desperately trying to get the car out on time!
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