CHT sensor extension, Curious, does it work? Who uses one? Options

[malcolm2]

I want to cover all my bases here. I have purchased the new GB CHT sensor from 914Rubber to try.

So, I think I will buy a spacer from Brad Mayeur to have the option. From what he says it should:

"Porsche 914/4 Cylinder Head Temperature Sensor Extension.

This little device slows down the heating of the sensor and improves warm up drivability."

I do have "warm up drivability" problems = Low idle RPM until the VDO CHT hits about 250*F. So it seems like my problems don't need the warm up to slow down, it needs to SPEED UP. (IMG:style_emoticons/default/WTF.gif)

914LTD.com





Also found on RATWELL (scroll down to WORKAROUNDS)http://www.ratwell.com/technical/TempSensorII.html#parts

[pbanders]

See my edited response above.

BTW, it's nearly 100 deg. F here today, gotta love late October in Phoenix. I was out doing some errands, and I drove the 914, so I got several chances to try different hot start techniques.

What worked best was to start with key off, then slightly crack open the throttle 1/4 of the way or less. Turn the key and crank, and hold the throttle steady until it starts, then back off slightly to keep the revs from going up too much. Now, hold the throttle at 2000 rpm for about 20 seconds to clear the plugs and get the heads warming up. Now, slowly close the throttle until you reach idle, it should be reasonably stable.

If it ever cools off, I'll make the switchbox I describe in the posting above. With a more complex switching arrangement, you could make the box capable of lean or rich mixture.

[BeatNavy]

What worked best was to start with key off, then slightly crack open the throttle 1/4 of the way or less. Turn the key and crank, and hold the throttle steady until it starts, then back off slightly to keep the revs from going up too much. Now, hold the throttle at 2000 rpm for about 20 seconds to clear the plugs and get the heads warming up. Now, slowly close the throttle until you reach idle, it should be reasonably stable.

If it ever cools off, I'll make the switchbox I describe in the posting above. With a more complex switching arrangement, you could make the box capable of lean or rich mixture.

Did that exact technique this afternoon after filling up at the gas station, Brad. Started like a champ, and I sort of feathered the throttle for about 30 seconds until idle stabilized. It's manageable....just slightly annoying.

EDITED response: This is what I get when I post too late at night and after my third glass of wine. The effect of CHT resistance on mixture is the higher the resistance, the richer the mixture. If you ADD resistance inline to the CHT, you're just going to make the mixture even richer and make it worse! What you want to do is add resistance in parallel to the CHT, which will have the effect of LOWERING the resistance the ECU sees, and making the mixture leaner.

I'm glad I'm not the only one here who enjoys a second, or, ahem (IMG:style_emoticons/default/shades.gif) , third, glass of wine while hanging out here (IMG:style_emoticons/default/smile.gif)

I was wondering if there was some way to meter more air in during the warm start process - almost like creating a temporary vacuum leak during the 30 seconds after warm start, as with the AAR at cold start.

[pbanders]

What worked best was to start with key off, then slightly crack open the throttle 1/4 of the way or less. Turn the key and crank, and hold the throttle steady until it starts, then back off slightly to keep the revs from going up too much. Now, hold the throttle at 2000 rpm for about 20 seconds to clear the plugs and get the heads warming up. Now, slowly close the throttle until you reach idle, it should be reasonably stable.

If it ever cools off, I'll make the switchbox I describe in the posting above. With a more complex switching arrangement, you could make the box capable of lean or rich mixture.

Did that exact technique this afternoon after filling up at the gas station, Brad. Started like a champ, and I sort of feathered the throttle for about 30 seconds until idle stabilized. It's manageable....just slightly annoying.

EDITED response: This is what I get when I post too late at night and after my third glass of wine. The effect of CHT resistance on mixture is the higher the resistance, the richer the mixture. If you ADD resistance inline to the CHT, you're just going to make the mixture even richer and make it worse! What you want to do is add resistance in parallel to the CHT, which will have the effect of LOWERING the resistance the ECU sees, and making the mixture leaner.

I'm glad I'm not the only one here who enjoys a second, or, ahem (IMG:style_emoticons/default/shades.gif) , third, glass of wine while hanging out here (IMG:style_emoticons/default/smile.gif)

I was wondering if there was some way to meter more air in during the warm start process - almost like creating a temporary vacuum leak during the 30 seconds after warm start, as with the AAR at cold start.

You could do that, but if you're got something that can do that, like a solenoid-controlled air bleed, if you did it right, it could be the basis for an idle stabilizer, too. I'd eventually like to poke around and see if there's something out there that I can find, or maybe adapt an existing idle stabilizer to our cars.