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What are your CHT's After LASAR Cowl Installation


C.J.

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Hello all,

Interested in knowing what improvement (if any) anyone has had after installing LASAR Cowl Fairing mod #131. It was my hope that my 1965 M20C's CHT would run cooler but that has not been the case so far. With its original guppy mouth, with ambient temp of 80F, after a 7 minute taxi & run-up, CHT 390F was typical with it rising to 430F by 600 feet AGL after cleanup & climb power established. Climbing at 130mph for 3 - 4 minutes brought it down to 400 - 410F where it would stay constant till level-off at any altitude from 4500 - 10,500. Mixture is kept at Full Rich to 5000. CHT's in cruise are 370 -380F at 65% Power at 100F ROP, with OAT'S generally at ISA +15C. Now with the LASAR Mod installed the CHT numbers are the same. Increasing power to 70% results in CHT 400F. My O-360 has 1900 TTSN & 30 SMOH and has a Power Flow Exhaust. Overhaul was completed by Lynn Mace. Engine gauges are original Garwin and seem accurate given CHT matches ambient OAT prior to engine start. I'm in Michigan with it now and in cooler OAT's but the CHT numbers are much the same. Mechanics up here said baffles looked good & increased the idle mixture by 3 quarters of a turn but it was no apparent help. 

Anybody who can provide some comparison numbers and/or solutions and experiences would be greatly appreciated.

Thanks

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Yeah that seems high on the ground.  I have the Lasar enclosure on an F but I’m little help because I have the io-360 and the closure was installed before I bought the airplane.  I have read that it provides more esthetics than actual cooling.

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Don’t think the closure makes much temp difference. A few people have said individual cylinder temps are more even.

Just because the Garmin gauge appears accurate at ambient does not mean much at higher temps.

Check the magneto timing. Going from 25* to 27* degrees BTDC would raise cylinder temps substantially. 20* would run much cooler.

Two mags, or do you have a Surefly ignition?  If Surefly, is it set for variable timing? 

When Lynn did the o/h, was the carb done? There is a larger main jet that should be used for Mooneys.  Might not have been done. This would affect only climb temps.  Idle mixture is for idle, red knob for cruise.

A couple of my engines, even though broken in, continued to be unusually warm for 50 to 75 hours.

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43 minutes ago, David Lloyd said:

Don’t think the closure makes much temp difference. A few people have said individual cylinder temps are more even.

Just because the Garmin gauge appears accurate at ambient does not mean much at higher temps.

Check the magneto timing. Going from 25* to 27* degrees BTDC would raise cylinder temps substantially. 20* would run much cooler.

Two mags, or do you have a Surefly ignition?  If Surefly, is it set for variable timing?

When Lynn did the o/h, was the carb done? There is a larger main jet that should be used for Mooneys.  Might not have been done.

A couple of my engines, even though broken in, continued to be unusually warm for 50 to 75 hours.

Surefly should not matter because it is fixed timing at low altitude and/or low rpm.  It doesn’t advance until roughly 25” mp or less at cruise rpm.  You’re right to check mag timing though.

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47 minutes ago, David Lloyd said:

Don’t think the closure makes much temp difference. A few people have said individual cylinder temps are more even.

Just because the Garmin gauge appears accurate at ambient does not mean much at higher temps.

Check the magneto timing. Going from 25* to 27* degrees BTDC would raise cylinder temps substantially. 20* would run much cooler.

Two mags, or do you have a Surefly ignition?  If Surefly, is it set for variable timing?

When Lynn did the o/h, was the carb done? There is a larger main jet that should be used for Mooneys.  Might not have been done.

A couple of my engines, even though broken in, continued to be unusually warm for 50 to 75 hours.

Agree that  timing is important, but those kind of CHTs at taxi power seems suspect.

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Eliminating some variables might help you through this.

Did the high CHT's exist before the engine overhaul or are they new after the engine overhaul?

W/ overhaul was carb and mags rebuilt?

Sounds like you have the original single cht gauge and single probe on #3 cylinder.

gauge/probe are reading ambient prior to start but we don't know if still calibrated through range. You could try sticking probe in coffee cup of boiling water to get an idea at mid range. if you have a fluke meter with temperature probe (or a thermometer that reads that high) you could using a heat gun or hair dryer to get an idea of calibration at higher temp. you heat both probes using fluke as your reference, be careful not to overheat things but you can get a fairly accurate reading if you control your heat slowly and allow things to reach steady state.

Baffles and seals can't be minimized, small gaps are huge pressure drops that take all the airflow and reduces airflow through the fins. looks good is not the same as "we think we have high cht readings and want to make sure all the air is getting pushed through the fins. really scrutinize your baffles, look where the silicone material is spliced and around corners to see how it all fits with cowling in place.

The Lasar cowling closure is more looks than improving cooling.

Mooney SB M20-182 is for the the E&F with io-360 but you can see that what they were trying to do was close off air through the fins on no 1&2 cylinder to force more through 3 and 4 and then out the bottom through a new exit scoop (side note if anyone has this on their E&F I would like to measure so I can fabricate)

once you knock off some variables this will get less complex

for the record engineering nerd and life time wrench turner not an A&P

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15 hours ago, David Lloyd said:

Don’t think the closure makes much temp difference. A few people have said individual cylinder temps are more even.

Just because the Garmin gauge appears accurate at ambient does not mean much at higher temps.

Check the magneto timing. Going from 25* to 27* degrees BTDC would raise cylinder temps substantially. 20* would run much cooler.

Two mags, or do you have a Surefly ignition?  If Surefly, is it set for variable timing?

When Lynn did the o/h, was the carb done? There is a larger main jet that should be used for Mooneys.  Might not have been done.

A couple of my engines, even though broken in, continued to be unusually warm for 50 to 75 hours.

It's got 2 mags.

I'll text Lynn on Monday re: the carb & see if he remembers. I don't remember seeing that notated in the logbook though & I don't have the logs handy right now to check.

I'll have the mechanics here check the timing to see if it's set at 25* BTDC. If so, I'll have them adjust to 20* 

Thanks for the input, David. Much appreciated.

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1 hour ago, TomM20F said:

Eliminating some variables might help you through this.

Did the high CHT's exist before the engine overhaul or are they new after the engine overhaul?

I'll ask the previous owner on Monday.

W/ overhaul was carb and mags rebuilt?

I don't remember seeing any notation of that in the logbook but will have that checked on Monday. I'll text Lynn to see if he remembers having done that. And ask the new operators of AGL Services in KMRN to check their records

Sounds like you have the original single cht gauge and single probe on #3 cylinder.

That's correct. The plan is to install an EI CGR-30 Combo monitor in late December or in January but for now I have to play the cards I was dealt.

 

 

1 hour ago, TomM20F said:

 

Baffles and seals can't be minimized, small gaps are huge pressure drops that take all the airflow and reduces airflow through the fins. looks good is not the same as "we think we have high cht readings and want to make sure all the air is getting pushed through the fins. really scrutinize your baffles, look where the silicone material is spliced and around corners to see how it all fits with cowling in place.

I'll have that checked out too.

The Lasar cowling closure is more looks than improving cooling.

Well it definitely looks better with it than without. 

once you knock off some variables this will get less complex.

Troubleshooting is so $$$$$ FUN!!!

for the record engineering nerd and life time wrench turner not an A&P

Just happy to have some other owner/operator input. Thanks Tom

 

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3 hours ago, C.J. said:

I'll ask maintenance to try that. Thanks.

I just can’t imagine there’s enough energy at taxi speed to generate those kinds of CHTs. In my F model I don’t think I could generate those kinds of taxi CHTs dragging the brakes. My CHTs are typically <300 when I start my take off roll.

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4 hours ago, C.J. said:

It's got 2 mags.

I'll text Lynn on Monday re: the carb & see if he remembers. I don't remember seeing that notated in the logbook though & I don't have the logs handy right now to check.

I'll have the mechanics here check the timing to see if it's set at 25* BTDC. If so, I'll have them adjust to 20* 

Thanks for the input, David. Much appreciated.

Check the timing listed on the data plate. I reviewed the TCDS as well as the Lycoming Operator’s manual. Both of those documents list 25° as the specified setting with no mention of an alternative option. 20° does not appear to be an approved setting for any O360 that Mooney installed.

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I’ve seen a few of these Doghouse M20C’s and they all run hot.  Add the power flow makes it even worse. You’re making more power from the engine without an associated increase in full throttle fuel flow.  Turning the carb up helps. I suspect that relocating the oil cooler helps. But 420 at 1000’ seems to be the  norm.  Powerflow seems to make that worse. 
I’ve got a 1968 O-320 Cardinal doing the same thing. Now we’re sending the carb off to get the main jet richened up ans gonna make the baffling 100% airtight. It will help but it won’t run cool 

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Do all Cs have the doghouse? Is there a consensus as to whether it’s the baffle design or the O360 that contributes to the heat?  I know it’s considered ideal to keep CHTs under 400 but I don’t see much anecdotal evidence of shorter cylinder life.
It’s interesting to me that Lycoming gave the option to retard the timing on the injected, angle valve but not the carbureted, parallel valve engine.

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21 minutes ago, Shadrach said:

Do all Cs have the doghouse? Is there a consensus as to whether it’s the baffle design or the O360 that contributes to the heat?  I know it’s considered ideal to keep CHTs under 400 but I don’t see much anecdotal evidence of shorter cylinder life.
It’s interesting to me that Lycoming gave the option to retard the timing on the injected, angle valve but not the carbureted, parallel valve engine.

I'm pretty sure they all have a doghouse, which is a piece of dogsh*t in my view.  Crap mixture distribution via the carb is another offender, and perhaps the dominant one  - It's really just #2 and #4 that have the issue for me (both in climb and cruise) - the other two cool nicely, even after putting in a Powerflow exhaust and advancing timing at lower power settings via the Surefly mag.  You really need to have the richer carb option on these engines also.  From '68 onward they fixed the cowl flap position on the C, which I suspect didn't help either.  I've "illegally" retarded baseline timing to -23ish on mine but it didn't noticeably help. 

At high CHTs, I think there is a cylinder longevity issue, maybe not in the low 400s though.  My hottest cylinder in climb (#4) actually lasted longer (~1350 hrs) than the other 3 before needing to be reworked - it rarely went any higher than the 430s in climb though, even on the hottest day.  When my blowby-related oil consumption rose to 1qt/3hrs and #4 had a consistently oily bottom plug, I figured it was time and I replaced #4 with factory new, hoping to make it another several hundred hours before overhauling.  After 1.5 years and 200 hours, oil consumption is back down to 1qt/3hrs, the crosshatch looks polished out of #4, and it now also has an oily TOP plug :angry:.   A little while before swapping #4, the Powerflow went in, which made it commonplace to break CHTs of 450 on that cylinder in climb, and I gotta think that's what led to the premature wear.  Now I leave the throttle out 1 inch when going to full power on the runway - this has barely perceptible effect on MP and fuel flow but keeps #2/4 CHTs in early climb below 420 generally. It must be improved mixture distribution that occurs here, though I think they also cool worse from an airflow perspective.   I wish I'd figured this out when #4 was brand new instead of abusing it so badly :(

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On 9/30/2022 at 4:28 PM, C.J. said:

Hello all,

Interested in knowing what improvement (if any) anyone has had after installing LASAR Cowl Fairing mod #131. It was my hope that my 1965 M20C's CHT would run cooler but that has not been the case so far. With its original guppy mouth, with ambient temp of 80F, after a 7 minute taxi & run-up, CHT 390F was typical with it rising to 430F by 600 feet AGL after cleanup & climb power established. Climbing at 130mph for 3 - 4 minutes brought it down to 400 - 410F where it would stay constant till level-off at any altitude from 4500 - 10,500. Mixture is kept at Full Rich to 5000. CHT's in cruise are 370 -380F at 65% Power at 100F ROP, with OAT'S generally at ISA +15C. Now with the LASAR Mod installed the CHT numbers are the same. Increasing power to 70% results in CHT 400F. My O-360 has 1900 TTSN & 30 SMOH and has a Power Flow Exhaust. Overhaul was completed by Lynn Mace. Engine gauges are original Garwin and seem accurate given CHT matches ambient OAT prior to engine start. I'm in Michigan with it now and in cooler OAT's but the CHT numbers are much the same. Mechanics up here said baffles looked good & increased the idle mixture by 3 quarters of a turn but it was no apparent help. 

Anybody who can provide some comparison numbers and/or solutions and experiences would be greatly appreciated.

Thanks

Your experience with the C model is typical.  Idle mixture only matters when idling - it has zero effect on climb/cruise temps, so your mechanic missed the mark there. Your temps as described in climb are actually a bit better than average considering the Powerflow.  Mine came with the cowl closure so I have nothing to compare to, but I've heard multiple folks say it made zero perceptible difference for them in terms of cooling or cruise speed.  

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Also getting 420-430F right after takeoff on initial climb out, especially when it's hot out. Cruise is around 360-380F depending on power %. Like everyone stated previously, I think you do need to have it checked for the idle/taxi temps as those seem abnormally high, even for a C.

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On 10/1/2022 at 4:02 PM, Shadrach said:

Check the timing listed on the data plate. I reviewed the TCDS as well as the Lycoming Operator’s manual. Both of those documents list 25° as the specified setting with no mention of an alternative option. 20° does not appear to be an approved setting for any O360 that Mooney installed.

You're probably right that 20* is not an option -

"Lycoming Operator's Manual Section 5-1-b(1) (Ring gear may be marked at 20* and 25*. Consult specifications for correct timing mark for your installation.)"

Mechanic hasn't told me what's on the data plate. They'll be testing the CHT probe on Monday.

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On 10/3/2022 at 3:16 PM, MooneyP87 said:

Also getting 420-430F right after takeoff on initial climb out, especially when it's hot out. Cruise is around 360-380F depending on power %. Like everyone stated previously, I think you do need to have it checked for the idle/taxi temps as those seem abnormally high, even for a C.

CHT probe will be checked on Monday.

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11 minutes ago, C.J. said:

You're probably right that 20* is not an option -

"Lycoming Operator's Manual Section 5-1-b(1) (Ring gear may be marked at 20* and 25*. Consult specifications for correct timing mark for your installation.)"

Mechanic hasn't told me what's on the data plate. They'll be testing the CHT probe on Monday.

I've never seen a Lyc 360 ring gear that isn't marked for both.  Unless your data plate diverges from the TCDS, 25° is the specified setting.

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On 10/2/2022 at 3:03 PM, DXB said:

Your experience with the C model is typical.  Idle mixture only matters when idling - it has zero effect on climb/cruise temps, so your mechanic missed the mark there. Your temps as described in climb are actually a bit better than average considering the Powerflow.  Mine came with the cowl closure so I have nothing to compare to, but I've heard multiple folks say it made zero perceptible difference for them in terms of cooling or cruise speed.  

I'd 100% agree there is zero perceptible difference in cooling or cruise speed.

$600 + labor for zero benefit - CAVEAT EMPTOR. And yes, I did research it and ask around so YMMV, but on the plus side it looks better than the guppy mouth.

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1 minute ago, Shadrach said:

I've never seen a Lyc 360 ring gear that isn't marked for both.  Unless your data plate diverges from the TCDS, 25° is the specified setting.

Yeah, I'm thinking it will be 25* too. Mechanic is contacting me re: CHT accuracy on Monday along with data plate info

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