Originally Posted by markweatherill
Is there anything inherently *wrong* with the wax pellet or bimetal vacuum-door air mixing system referred to earlier?
The problem is precision and speed. It is a simple system, but here's a problem I foresee (please correct me if my assumption is incorrect):
15F, Cold Start at work. 100% HAI input off of the exhaust manifold / 0% Cold Air. The engine warms up and intake temps hit 100F after 10 minutes of driving in the city. 110F is reached and the machanical system opens the cold air tube and closes the hot: a rush of cold is introduced. IATs are now down significantly. The mechanical system takes a while to change back to a warmer mix. The result is a wider swing of temperatures and a potential for a low temperature average.
An electronic system would recover more quickly and precisely control actuators to instantly keep the temperature range in check. A threshold of 85 low and 95 high would be programmed to keep those servos busy, especially during higher engine speeds. With luck, 80-100 maximum range would be realized.
Basically, here's what I've come up with so far:
2 throttle bodies from a "U-Wrench it"-type place, and rubber tubing from perhaps a used vehicle as well (for the cold air especially and to fit the throttle body; hot air will utilize a metallic end source into a plastic or rubber tube. Both outputs will terminate into a 'Y' directly to the airbox. I'd like to run it farther up the flow, but the airbox contains the filter and is the only way to provide clean air.
Now the tricky part: control. At first, I'd like to try wiring a knob that, for example, ranges in motion from 9-o'clock to 3-o'clock. The "Noon" position will allow 50/50 mix where 7-o'clock gives 70 hot/30 cold and 9 = 100 hot/ 0 cold (and the same on the Noon to 3 on the cold side) -- or if that's too complicated, 2 knobs at first for each source.
To control the throttle bodies, servos or actuators will move the valves based on current from the knobs. Someone mentioned using actuators from an old fax machine. If that doesn't work, I could find a (recommended
) company that sells servos cheaply. Then badda-bing controlled intake temps.
The final stage: full automation. If this proves to be work, I'd like to use Red's example using products similar to those from Parallax to program a range from the IAT to move those servos without thinking about it
That is quite some system -- good work! Unfortunately for my setup, if temps go higher than 120F, then detonation, power loss, and an overall loss of FE will occur. I hear Saturns love high temps, though. For the Integra, this may be impossible in the summer when the CAI is in full ops and it'll get what it can, but for the remaining parts of the year, the mix should help.
Keep it coming folks -- good stuff. I can't go to sleep without brainstorming about this first. Call it what you will, but it's a version of cabin fever: not easily being able to modify the car in Winter!