Dan M Posted April 3, 2009 Share Posted April 3, 2009 Since this is an EXPERIMENT, I'll be trying various combo's and different air gaps (and thermo-compound) until I have a better understanding of what the ranges of limitations and optimums are. With low or no air gap and thermo-compound in there, this is as direct a thermal connection as may be had. But since the thermal inertia of the thermistor is so infinitesimally tiny, as you've observed previously, running with an air gap may "smooth out" unwanted temp spike reads, while still providing very accurate overal reads without appreciable lag time in response to temp changes. I hope to gain more clarity on this later. I'm thinking you have the hot set up so to speak right now. The sensor is designed for air. Thermo paste is adding mass so it may hinder it. I guess that is what experimenting is about. What I really like about all of this is it is lending some credence to early musings from about 30 pages ago when the naysayers were dismissing it as nonsense. Of course they still will..... Link to comment Share on other sites More sharing options...
Greg Field Posted April 3, 2009 Share Posted April 3, 2009 You would be entirely remiss if you did not also experiment with different gasses at the different gaps until the transfer rate matches the mapping of your bike perfectly and compensates for the (probably) worn valve guides. Or perhaps the whole system was really designed to work with the atomsphere from another planet? Or perhaps with the air density at a certain altitude? Don't think the Italians wouldn't pull such a stunt just to personally confound you, personally Commendatore Ratchethack. Link to comment Share on other sites More sharing options...
raz Posted April 3, 2009 Share Posted April 3, 2009 Weight, ~1 gm. gram-meters? That would be a unit of torque. I didn't expect you to make such uncool mistakes Ratch Other than that, ok, thank you, it is interesting. And wierd. I'm puzzled the oem ecu is so sensitive to exact head temperature, I can't see the reason. There is an easy to understand correlation between air temp and fuel mixture by weight, but I don't get why engine temp would need much attention, except for compensating for condensation at cold temps. Link to comment Share on other sites More sharing options...
Skeeve Posted April 3, 2009 Share Posted April 3, 2009 ... I'm puzzled the oem ecu is so sensitive to exact head temperature, I can't see the reason. There is an easy to understand correlation between air temp and fuel mixture by weight, but I don't get why engine temp would need much attention, except for compensating for condensation at cold temps. The retained heat in the cylinder head will affect such diverse factors as preheating of the fuel-air charge, flame front propagation speed, quenching, etc., and these in turn will affect how fast the motor turns (& how well it burns) at idle [which is a key regime in emissions testing.] Link to comment Share on other sites More sharing options...
Guest ratchethack Posted April 3, 2009 Share Posted April 3, 2009 gram-meters? That would be a unit of torque. I didn't expect you to make such uncool mistakes Ratch Well spank me naked! Here's some evidence that someone's actually reading! I must've written "g." a bazillion times in 4 yrs. of undergrad Chem and Physics, but I reckon it was one too many decades back. Thanks for the correction, Raz. Prev. post edited. Link to comment Share on other sites More sharing options...
dlaing Posted April 4, 2009 Share Posted April 4, 2009 Greg's books covered revolutionary bike designs Link to comment Share on other sites More sharing options...
dlaing Posted April 4, 2009 Share Posted April 4, 2009 I'm thinking you have the hot set up so to speak right now. The sensor is designed for air. Thermo paste is adding mass so it may hinder it. I guess that is what experimenting is about. What I really like about all of this is it is lending some credence to early musings from about 30 pages ago when the naysayers were dismissing it as nonsense. Of course they still will..... (not that you are stupid!!!) I see some room for improvement, but I think I'll be ordering one of these sensors! I'd consider replacing the brass threaded piece with an aluminum one, and I might pursue something other than the Delrin, but I don't know what....glass? I am having trouble with the photo, is the GM sensor threaded?, if so, what is the thread size/pitch? Link to comment Share on other sites More sharing options...
gstallons Posted April 4, 2009 Share Posted April 4, 2009 The GM sensor is a 3/8" NPT thread Link to comment Share on other sites More sharing options...
Greg Field Posted April 4, 2009 Share Posted April 4, 2009 Greg's books covered revolutionary bike designs Dave: That's clearly a photoshop job 'cause Harley never fitted whitewalls along with square rims. Link to comment Share on other sites More sharing options...
Dan M Posted April 4, 2009 Share Posted April 4, 2009 (not that you are stupid!!!)I see some room for improvement, but I think I'll be ordering one of these sensors! I'd consider replacing the brass threaded piece with an aluminum one, and I might pursue something other than the Delrin, but I don't know what....glass? I am having trouble with the photo, is the GM sensor threaded?, if so, what is the thread size/pitch? The GM sensor is not threaded. It is designed to push through a grommet in a plastic air box or duct. I believe RH is securing it in his holder with a set screw. Link to comment Share on other sites More sharing options...
Guest ratchethack Posted April 4, 2009 Share Posted April 4, 2009 The set screw secures the threaded brass conductor stud. The GM sensor has no threads, as Dan noted. It was about .02" too large in diameter to fit the .5" bore I put in the holder, and has ribs on it that I sanded down until it was a "just right" secure, interference (push in) fit. Link to comment Share on other sites More sharing options...
gstallons Posted April 4, 2009 Share Posted April 4, 2009 The GM sensor is a 3/8" NPT thread I stand corrected. I was thinking of the coolant temp.sensor. The part in question is an air intake temp. sensor. Link to comment Share on other sites More sharing options...
dlaing Posted April 4, 2009 Share Posted April 4, 2009 You would be entirely remiss if you did not also experiment with different gasses at the different gaps until the transfer rate matches the mapping of your bike perfectly and compensates for the (probably) worn valve guides. Or perhaps the whole system was really designed to work with the atomsphere from another planet? Or perhaps with the air density at a certain altitude? Don't think the Italians wouldn't pull such a stunt just to personally confound you, personally Commendatore Ratchethack. Some sort of powder may be the ticket. Higher mass than any gas, but lighter than goos, the thermal diffusivity number for powders could be ideal if they offer high Thermal Conductivity. Diamond has better conductivity than copper or aluminum. I am not sure how good the conductivity is in powder form, or what the best source might be, or even if it is at all economical. Graphite would surely be more economical, and offer qualities that may work better than goo. Boron Nitride may be another option. But getting it to fill the chamber for consistent temperature readings could be challenging. You would need a sealable fill hole. But if the gap area is small enough, the mass of a thermal paste should be pretty minimal. I know some of the thermal pastes I have scraped from heat sinks are pretty light and dry. Link to comment Share on other sites More sharing options...
Greg Field Posted April 5, 2009 Share Posted April 5, 2009 Yes, diamond. Perfection will require that the sensor holder be carved from the Hope diamond. Link to comment Share on other sites More sharing options...
gstallons Posted April 5, 2009 Share Posted April 5, 2009 And while we're at it, make the sensor adapter out of platinum. Link to comment Share on other sites More sharing options...
Recommended Posts