docc Posted May 8, 2008 Posted May 8, 2008 I've done the brass sensor holder. Packed the space with copper jizz. I'm anxious to see if it affects performance or fuel economy. The sensor came out easily ("finger tight"), but the plastic holder was a bit#&. It took a combination of four wrenches to back the thing out. It never broke. I can't see how taping the fins could make a difference with the tip of the sensor immersed in copper against the bottom of the holder.
dlaing Posted May 8, 2008 Posted May 8, 2008 I can't see how taping the fins could make a difference with the tip of the sensor immersed in copper against the bottom of the holder. Think what happens to the temperature reading through the brass housing when you drive through heavy rain at high speeds. Not that I would tape my fins as I am not sure it is wise to let the sensor get that hot.
docc Posted May 8, 2008 Posted May 8, 2008 It looks like the finning would help protect the connector and wiring from head temperature heat while the tip of the pick-up is still in contact down deep.
Guest frankdugo Posted May 9, 2008 Posted May 9, 2008 hey pete,no good deed goes unpunished.there's alot of shit heads out there.thanks for all the info-keep it coming
Ryland3210 Posted May 10, 2008 Posted May 10, 2008 It looks like the finning would help protect the connector and wiring from head temperature heat while the tip of the pick-up is still in contact down deep. The brass adapter is quite massive, and conducts heat very well. I taped my fins to prevent the adapter somewhat from spot cooling that part of the head, thereby depressing the temperature of the sensor. I don't worry about it getting too hot, because even if insulation were wrapped around the fitting, it's conductivity would not let its temperature rise any more than the head itself.
docc Posted May 10, 2008 Posted May 10, 2008 Well, this changed the running more than I expected. The idle dropped about 200-300 rpm. There is more 'burble' on engine braking (leaner?). And the throttle response 'seems' crisper and more linear. I've gassed up to see if the fuel economy is affected. Thanks again to everyone for sharing their tuning secrets!
Ryland3210 Posted May 10, 2008 Posted May 10, 2008 Well, this changed the running more than I expected. The idle dropped about 200-300 rpm. There is more 'burble' on engine braking (leaner?). And the throttle response 'seems' crisper and more linear. I've gassed up to see if the fuel economy is affected. Thanks again to everyone for sharing their tuning secrets! Hi docc, You probably know this already, but keep the idle speed up to 1100 to 1200 to maintain oil pressure when the engine is hot. I'm really looking forward to how you make out on fuel economy. best, John
docc Posted May 12, 2008 Posted May 12, 2008 Theorizing that I had already set the TPS for a given rpm, I simply turned the throttle screws in to bump the idle up. Next tune-up interval I'll go through the whole process again. Perhaps by next week I'll have some fuel economy data while I chase the heat source in my wiring harness . . .
Ryland3210 Posted May 13, 2008 Posted May 13, 2008 Theorizing that I had already set the TPS for a given rpm, I simply turned the throttle screws in to bump the idle up. Next tune-up interval I'll go through the whole process again. Perhaps by next week I'll have some fuel economy data while I chase the heat source in my wiring harness . . . Uh-oh. You said screws (plural). As a reminder, if you did any part of that idle adjustment with the right idle screw, back it out and make up the difference with the left screw. Remember, that's what keeps the connecting rod in tension at idle to eliminate backlash, and keep the throttle in synch at idle and off idle.
docc Posted May 15, 2008 Posted May 15, 2008 Thanks for the reminder. I've actually used both methods over the years with more years having the right screw defeated. At this point I've been using the left screw as 'primary', but turning the right screw in just to make a stop. It's more than likely probably redundant. I always check the mercury sticks at both idle and rpm.
Guest ratchethack Posted January 25, 2009 Posted January 25, 2009 It now occurs to me that perhaps the sensor actually NEEDS to be at least partially insulated & that the CHT temp information provided by a properly installed & functioning sensor is what the ECU has been calibrated to. By placing the sensor in direct thermal contact with the head, temp data may be significantly elevated & therefore adversely affect the fuel map at various points. . . Having finally got a ROUND TUIT, I just installed the brass holder and futzed with it, and I'm in agreement with Tony.^ Instead of thermal paste, I used a custom-formed cylinder of lead drifted into the holder. By my measure with a dial depth gauge, the distance between the tip of the sensor and the bottom of the holder cavity ain't a tiny thing, and it's clearly very much intentional. The gap is .25". I cut and finished the lead cylinder to about .26" in length. The lead was soft enough so seating the sensor pushed into the lead ~.01", ensuring very complete, direct thermal flow. As it turned out, this wasn't a good thing. The results were abominable. It wouldn't idle when fully warm, missing and coughing at low RPM and off-idle transitions in traffic something fierce. Clearly, the sensor is working fine, but the ECU is now putting the FI pulsewidth in lean mode when it needs to be in rich mode, which leads me to Tony's conclusion above. Though it ran fine at normal operating RPMs at speed, it was just about unrideable in town. So back in went the OE plastic holder with no thermal goop a-tall, and the formerly good as ever in town and in traffic behavior (as well as at speed) returned instantly. I'll be experimenting with the brass holder by incrementally taking out a few mm of depth into the lead at a time, boring into it with my drill press to re-create a less than OE, but smaller-going-to-larger air gaps, to see wot this does. Will advise.
Dan M Posted January 25, 2009 Posted January 25, 2009 Will advise. Please do. Am I the only one that finds it curious that MG designs the map on a temp calculation rather than actual head temp? I've always practiced having good clean contact between temp sensors and the surface of whatever they are reading. The sensors can convey a fairly accurate read to the ecm if they are contact. So, one would ask, why the air gap? I wonder if it is because we are dealing with an air cooled head and temp varies considerably compared to a liquid cooled motor. Perhaps in situations like running slow in traffic with a high head temp the engineers were avoiding leaning out of the mix creating even hotter combustion temps. The air gap might not only lower the temp of the sensor but slow the response too. Seems there must be a reason? Just thinking out loud, winter in Chicago and all of that. 1
gstallons Posted January 25, 2009 Posted January 25, 2009 Hey I installed a brass adapter replacing the plastic one. I filled the cavity with FORD heat sink compound when I put the CHT sensor back in the adapter. I didn't notice any difference in performance. Every sensor I know of (in this use) comes in direct contact with the substance it is monitoring.
savagehenry Posted January 25, 2009 Posted January 25, 2009 Hey I installed a brass adapter replacing the plastic one. I filled the cavity with FORD heat sink compound when I put the CHT sensor back in the adapter. I didn't notice any difference in performance. , only I used anti-seize with a little copper in it. And this doesn't mean it runs exactly the same, but I am such a ham fisted troglydyte I don't notice any major differences before and after.
Guest ratchethack Posted January 25, 2009 Posted January 25, 2009 ...one would ask, why the air gap? I wonder if it is because we are dealing with an air cooled head and temp varies considerably compared to a liquid cooled motor. Perhaps in situations like running slow in traffic with a high head temp the engineers were avoiding leaning out of the mix creating even hotter combustion temps. The air gap might not only lower the temp of the sensor but slow the response too. Such have been among my thoughts also, Dan. Seems to me the brass holder was intentionally designed with a considerable air gap (.25") for a specific intent and purpose that we've been directly thwarting here with heat conducting materials. The fins on the brass holder, unlike the OE holder, were clearly designed to dump heat. This means it flows heat through it -- not simply into it, like the OE plastic holder, which is more of a tiny dead-end for heat flow. Constant heat flow through the brass holder would seem to more rapidly (and potentially more accurately) respond to the changing delta in temps betweeen the head and ambient. But that's just me. Reverse engineering the intent of long-retired and gone Italian engineers who operated at the ragged limits of sporadic, puny, and non-existent budgets under dubious "continuous transition management" (d'you reckon they were at least smart enough to demand payment in advance for services rendered? ) in a lake resort at the foot o' the mighty Dolomites -- ain't that wot a Guzzi Winter is for, after all? More futzing later today. Say Dan and Henry -- Speakin' o' heat flow -- I just gotta ask. Wot's the local spin on the ever-expanding noxious cloud emanating from the Blago-ObamaNation stink bomb? Will this eventually be doctored up enough by The Chicago Tribune, et al to pass as simply more corrupt Chicago Daley/Blago/Obama Machine politics as usual, or d'you think the national focus at the time of the inauguration-coronation actually suffered enough collateral damage from Blago-splatter that ol' Hot Rod will have to be strung up to take the heat off The Messiah? Enquiring minds. . . (well, you know). . .
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