Hi guys! Im a new guy posting here so go easy on me, hehe.
Ok my question involves tachometers...tell me if Im right in thinking this: Tachs operate on variable dc voltage...the higher the voltage (up to a point), the higher the needle moves...correct?
Here's the reason Im asking...I've got a 99 Tahoe that I recently installed a Hot Ait Intake on....(open element sucking engine bay air). What Im thinking is, that I could mount a 12vdc fan, say about an 80mm on the fender hole where the stock airbox sucked its outside air from. Powering the fan off the point where the tach is being fed from, thus, the fan would spin slower while the engine is at idle and faster when your mashing the pedal. Reason being to suck in cooler outside air and blowing it directly onto the filter element.
I know it sounds like a real dumba$$ idea, but for taking the cheap way, and if whatever it is feeding the tach could hanlde the tiny bit of extra load I think it would be benficial. Im asking here because I have no idead if its the coil or the distributor that feeds a tach, or even if Im right about the whole tach operating thought.
What do you 12v gurus think?
THANKS!!!
so what your wanting to build is an electric blower, you do realize you'll get no benifit from it right? if you use the tach signal your tach may not read correctly (fans use quite a bit of current) a real easy thing to do is go to home depot and get some pvc pipe the right diameter and extend your intake to in the fender (still won't gain much about 2 hp is the norm)
get some cardboard out. cut out peices of cardboard to isolate the filter from the engine's heat. Once you got it all pieced together, go to homedepot, and get some sheet metal. Cut the metal do the same shape as the cardboard and mount it in your car. That way it'll prevent the heat getting to the intake.
I may be talking out my ass but the tach signal is a ppr (pulse per revolution) that is then converted into a varying voltage to controlt the gauge. At leas this is how I believe my ford works, there is no voltage on the tach wire. *if* you did wire up a fan you would have to wire it in the gauge cluster. That could require some delicate solder. And what if the voltage of the tach is too low. Most computer fans won't spin at voltage under 7vDC. There are a lot more variables and no good fans that will actually supply any good air flow. IMHO it would be best to extend the tube to the fender or build shielding like mentioned above.