Gary0747 Posted March 4, 2019 Report Share Posted March 4, 2019 I have always had this weird looking line from my engine to the firewall. It is a coil of 1/8 inch copper tubing with a size 2 tube connection to the firewall pass thru fitting. It has always worked fine with no problems with vibration readings on the gauge or liquid in the line. Is this the proper way this line should be run? Quote Link to comment Share on other sites More sharing options...
LANCECASPER Posted March 4, 2019 Report Share Posted March 4, 2019 if it ain't broke . . . 2 Quote Link to comment Share on other sites More sharing options...
Guest Posted March 4, 2019 Report Share Posted March 4, 2019 It’s correct. Quote Link to comment Share on other sites More sharing options...
Gary0747 Posted March 4, 2019 Author Report Share Posted March 4, 2019 Thanks, I saw the diagram but the hoses or lines were all Mooney special part numbers. What I have looks to be simply 1/8 copper tubing that is coiled and in the way of some acces to other stuff. Quote Link to comment Share on other sites More sharing options...
asaxet Posted March 4, 2019 Report Share Posted March 4, 2019 Exactly the way my 66 is... kinda a pita when installing the engine monitor... starts on engine as AN4 fittings then down to AN2... took a while to order and install the 4 to 3 then sensor and 3 to 2 reducers.... Quote Link to comment Share on other sites More sharing options...
Yetti Posted March 4, 2019 Report Share Posted March 4, 2019 The PITA is the line is so small it don't fit most flare tools. Had to go bother the grumpy IA for an impact one and take the line off so I could put it in a vise. Quote Link to comment Share on other sites More sharing options...
MARZ Posted March 4, 2019 Report Share Posted March 4, 2019 The coil in the line is to alleviate vibration breaking the line - don't cut it to make it more direct. Quote Link to comment Share on other sites More sharing options...
carusoam Posted March 5, 2019 Report Share Posted March 5, 2019 The mid 60s Mooneys used about an 1/8th inch soft aluminum line.... with a calibrated weep hole in it... aluminum on one side of the fire wall, copper on the engine side of the firewall.... and a bunch of fittings in between... The thing to know about replacing it is the size of the weep hole... get this wrong and the the wrong numbers are shown on the MP gauge... The weep hole is in the aluminum line, an inch or two from the MP gauge... The oddity is the dimension of the weep hole isn’t on all the various drawings for the M20C... one of the key things I learned by calling the Mooney factory and talking directly with THE Bill Wheat... the size of the weep hole is dimensioned on the instrument page for the M20F... 40 years after Bill Wheat signed my M20C’s log book for airworthiness, the same guy was on the phone helping me source a drill to make a weep hole in its MP line... I hand fashioned a flare tool using a steel finish nail... The MP line had cracked and propagated right at the weep hole making it impossible for me to know what size it used to be... For an electronic MP sensor, I bet the weep hole gets eliminated... PP thoughts only, not an instrument tech... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Gary0747 Posted March 6, 2019 Author Report Share Posted March 6, 2019 So where did those installing EDM900 and other electronic MP sensors install their sensors? Did you install in the cabin or on the engine side of the firewall. Using or not using a weep hole? Quote Link to comment Share on other sites More sharing options...
carusoam Posted March 6, 2019 Report Share Posted March 6, 2019 Gary, I think Clarence @M20Doc May have shown the installation of three sensors on a nicely formed piece of sheet metal... the sensor mount... Dev might have something similar in his M20C... The sensor mount was probably attached to the firewall. All the hoses and wires were plumbed properly from there.... As far as the weep hole goes... that is required for the health of the mechanical gauge... Expect no weephole for a new electronic sensor. PP thoughts only, not a mechanic... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Guest Posted March 6, 2019 Report Share Posted March 6, 2019 This one? Holes in the top for the transducers and holes in the bottom for the hose connections. Clarence Quote Link to comment Share on other sites More sharing options...
Bob_Belville Posted March 6, 2019 Report Share Posted March 6, 2019 4 Quote Link to comment Share on other sites More sharing options...
Gary0747 Posted March 7, 2019 Author Report Share Posted March 7, 2019 Nicely done on both installations. I assume no weep hole in either install? Also why the stand off bracket instead of just mounting to the firewall using the adel clamp JPI provides for each sensor? also Bob it appears you have managed to get rid of that long coil of 1/8 inch copper tubing that messes up most installations with a factory gauge Quote Link to comment Share on other sites More sharing options...
Bob_Belville Posted March 7, 2019 Report Share Posted March 7, 2019 58 minutes ago, Gary0747 said: Nicely done on both installations. I assume no weep hole in either install? Also why the stand off bracket instead of just mounting to the firewall using the adel clamp JPI provides for each sensor? also Bob it appears you have managed to get rid of that long coil of 1/8 inch copper tubing that messes up most installations with a factory gauge I suspect the offset is to provide room for a wrench on bottom fittings. I've had the 930 for over 6 years. I recall that in the beginning the MAP oscillated. JPI provided a snubber valve (name?) that dampened the pulsing pressure. Quote Link to comment Share on other sites More sharing options...
kortopates Posted March 7, 2019 Report Share Posted March 7, 2019 I suspect the offset is to provide room for a wrench on bottom fittings. I've had the 930 for over 6 years. I recall that in the beginning the MAP oscillated. JPI provided a snubber valve (name?) that dampened the pulsing pressure. JPI has gotten pretty good at fixing the MAP oscillations within their firmware. It seems very few installations require installing a snubber in the line but occasionally they'll give the client one when the s/w fails to smooth it. Quote Link to comment Share on other sites More sharing options...
carusoam Posted March 7, 2019 Report Share Posted March 7, 2019 Those sensor racks look great! The reason for the weep hole.... it keeps fuel vapor from being sucked into the mechanical gauge when the engine gets turned off... the gauge is like a can, under vacuum.... Fortunately modern pressure sensors are not susceptible to such mechanical goofyness.... when you take apart the old MP/vac line... you will probably see blue goo all the way up to the hole... more, the closer to the engine... The weep hole sets up a tiny amount of air flow drawn continuously towards the intake. It would also have a dampening effect on the reading, but the snubber, as Bob mentions above, is a hole that is in the line, that has a tendency to chop the top and bottom off the peak and minimum readings... there are some snubbers for the mechanical gauges as well that get detailed in the parts catalog... mounted on the back of the instrument. If you see the needle waving around like it is vibrating.... probably a snubber issue... or something like the engine mount is broken... causing some serious vibration... The MP naturally has a lot of noise with all those valves opening and air is flowing at full force, then the valve closes...., then another opens.... it would be interesting to graphically see the air flow during the two cycle of the crank... PP thoughts only, not an instrument guy... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Gary0747 Posted April 21, 2019 Author Report Share Posted April 21, 2019 I am posting in this old thread since we finished installing a JPI EDM 900. Everything is working ok but I am a bit annoyed with the variation in readings on my manifold pressure input to the EDM. I see a bounce in readings of a half inch or more on the instantaneous readings. I don’t think the variation was this large on the old gauge. As Carusoam indicates a number of things were done on the design of the original install to dampen the the factory gauge. It appears most of the EDM 900 installs simply connect directly to the transducer with a relatively large hose. No coil of small copper tubing and likely no small bleed hole, both of which should provide dampening. This might be the cause of what I am seeing or it could simply be mechanical vibration of my transducer by not having the bracket mount as shown in some of the photos above. Any thoughts or similar observations? Perhaps the variation is just to be considered normal and the calculations within the EDM for things like % HP that utilize the MP readings have software to average things out. Quote Link to comment Share on other sites More sharing options...
Yetti Posted April 21, 2019 Report Share Posted April 21, 2019 On 3/6/2019 at 10:24 PM, carusoam said: Those sensor racks look great! The reason for the weep hole.... it keeps fuel vapor from being sucked into the mechanical gauge when the engine gets turned off... the gauge is like a can, under vacuum.... Fortunately modern pressure sensors are not susceptible to such mechanical goofyness.... when you take apart the old MP/vac line... you will probably see blue goo all the way up to the hole... more, the closer to the engine... The weep hole sets up a tiny amount of air flow drawn continuously towards the intake. It would also have a dampening effect on the reading, but the snubber, as Bob mentions above, is a hole that is in the line, that has a tendency to chop the top and bottom off the peak and minimum readings... there are some snubbers for the mechanical gauges as well that get detailed in the parts catalog... mounted on the back of the instrument. If you see the needle waving around like it is vibrating.... probably a snubber issue... or something like the engine mount is broken... causing some serious vibration... The MP naturally has a lot of noise with all those valves opening and air is flowing at full force, then the valve closes...., then another opens.... it would be interesting to graphically see the air flow during the two cycle of the crank... PP thoughts only, not an instrument guy... Best regards, -a- so does the .040 weep hole go on the engine side of the snubber or the gauge side? Quote Link to comment Share on other sites More sharing options...
carusoam Posted April 21, 2019 Report Share Posted April 21, 2019 Stand by, Gary... The bouncing JPI MP data issues have been pretty well resolved... Bob and Marauder have been very helpful with the details... a device (snubber) with a small internal hole ... that ‘chokes’ the waves/noise that are naturally in the manifold.... I believe JPI sells the proper size snubber for this... we can ask @Jeev our JPI seller... Jeev has the best resource for tech questions... I’m not sure how much sensitivity there is to vibration or shaking... if it is really sensitive... you can see it by having somebody shaking it while on the ground.... while watching the display... no need to even run the engine... If it is sensitive to shaking... that bracket will be better than the art that it looks like... The original weep hole, is on the entrance to the old mechanical gauges... it was dual functional... lopped the wave pattern down, and kept fuel from reaching the gauge. Especially after engine shut-down... the MP gauge was like a vacuum can.... Modern sensors have eliminated the need for the weep hole/vacuum relief... they must have some sort of a diaphragm that is sensitive to 1atm of vacuum, and no sensitivity to fuel... @Yetti Yetti, Expect a weep hole if you stay with the old mechanical MP gauge... (external hole) No weep hole if you go with the a modern sensor and electronic gauge.... but add the snubber to avoid the wave/noise... (internal) If considering adding a snubber to a mechanical gauge... you would want to keep fuel from entering the snubber, as the evaporated fuel’s blue goo may block the snubber’s small internal hole... the challenge that arises with adding a snubber... it may take trial and effort of a couple sizes to find what works best... both holes would need to be ‘calibrated’ type accurate holes to produce a known range of MP that would correlate to what the gauge can read... The complexity needed, to get the accuracy and smooth reading on a mechanical gauge... would take some real Yetti effort... ————— Also... Fuel pressure gets a similar treatment... there are waves and noise there as well... if the specific snubber on FP stops working... there is a procedure for allowing the needed air bubble back in the line.... If not sure what we are seeing... this is a great opportunity to download some JPI data and port it over to the Savvy site... post a link we can probably put MP and FP and rpm and FF on the same graph.... Speaking of waves... and chokes... one MSer needed to put one on the JPI’s electrical wires to dampen signals coming out of the JPI that were interrupting or breaking the squelch... (intercom challenge) PP thoughts only, I haven’t refreshed these memories in a while.... and I’m not a mechanic... let me know if I missed something... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Yetti Posted April 22, 2019 Report Share Posted April 22, 2019 The 75F came with a snubber that sits between the big tubing and the little tubing. Least that what I think it is, it could just be a reducer. Let me see if I can find a picture. 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted April 22, 2019 Report Share Posted April 22, 2019 It’s probably a complex set of parts for reducers and fittings for entering and exiting the dog house and firewall... starting with larger diameter copper pipe and ending with the 1/8th inch soft aluminum coil... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Jeev Posted April 22, 2019 Report Share Posted April 22, 2019 3 hours ago, Gary0747 said: I am posting in this old thread since we finished installing a JPI EDM 900. Everything is working ok but I am a bit annoyed with the variation in readings on my manifold pressure input to the EDM. I see a bounce in readings of a half inch or more on the instantaneous readings. I don’t think the variation was this large on the old gauge. As Carusoam indicates a number of things were done on the design of the original install to dampen the the factory gauge. It appears most of the EDM 900 installs simply connect directly to the transducer with a relatively large hose. No coil of small copper tubing and likely no small bleed hole, both of which should provide dampening. This might be the cause of what I am seeing or it could simply be mechanical vibration of my transducer by not having the bracket mount as shown in some of the photos above. Any thoughts or similar observations? Perhaps the variation is just to be considered normal and the calculations within the EDM for things like % HP that utilize the MP readings have software to average things out. Gary - Where did you install your MP sensor? If I read your post correctly you used the existing copper line? We always run a new MP hose to the JPI sensor if the aircraft has that old style line and never have an issue with fluctuations. It should be pretty easy to run a new line or give JPI tech a call to see if they have a quick fix for you. Good luck and please post your resolution. Quote Link to comment Share on other sites More sharing options...
Gary0747 Posted April 22, 2019 Author Report Share Posted April 22, 2019 Jeev, The sensor is installed on the firewall with the JPI supplied Adel clamp which is not nearly as solid and secure as the bracket mounts the others show. We used the original copper tubing coil which we assume did some dampening. We obviously did not use the small aluminum tubing with the weep hole that was on the cabin side of the firewall and no doubt did some additional dampening on the original gauge. I can’t see how just a straight hose connection to the new transducer does any dampening unless there is an additional orifice in the hose? Perhaps I am the only one even noticing this variation in the MP instantaneous measurement? The variation does not seem to show up in the % HP readout due to apparent averaging in the JPI software. Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted April 22, 2019 Report Share Posted April 22, 2019 I fixed this problem with:https://www.omega.com/en-us/sensors-and-sensing-equipment/sensing-accessories/pressure-snubbers/p/PS-SNUBBERSif you order the PS-8G, it uses 1/8npt and will fit inline with no adapters required.Tom 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted April 22, 2019 Report Share Posted April 22, 2019 14 hours ago, Gary0747 said: Jeev, The sensor is installed on the firewall with the JPI supplied Adel clamp which is not nearly as solid and secure as the bracket mounts the others show. We used the original copper tubing coil which we assume did some dampening. We obviously did not use the small aluminum tubing with the weep hole that was on the cabin side of the firewall and no doubt did some additional dampening on the original gauge. I can’t see how just a straight hose connection to the new transducer does any dampening unless there is an additional orifice in the hose? Perhaps I am the only one even noticing this variation in the MP instantaneous measurement? The variation does not seem to show up in the % HP readout due to apparent averaging in the JPI software. Typically there is a small orfice or snubber in one of the fittings in the line to dampen oscillations to the original MAP gage. The weep hole in the low point of the line near the cylinder head allows the line to drain and prevents contamination of the small line and the original mechanical MAP gage. Clarence Quote Link to comment Share on other sites More sharing options...
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