Baffle Seals, how much cooling am I losing?

[dzeleski]

With the summer being warmer then the previous year I had with my J im seeing temps during climb that are a little higher then I would expect. 1-3 seem to be decent peaking around 350-380 depending on the day, but number 4 has been pushing 390-405. My #4 gami injector is absolutely too lean which I will resolve but im thinking my baffles might either need some love or to be replaced.

Attached a few photos of my current setup, it seems I have a massive hole where the bump of the cowl is and then two smaller holes in each corner. Other wise the baffles are in decent shape. Thoughts?

[EricJ]

Those CHTs aren't terrible, but not great, either.   A simple thing to do to close those smaller holes is just cut a slice from the edge down the middle of where the fold is.   You don't need to cut down the baffle very far, just enough to relieve the bunching that makes that fold so that the two pieces overlap instead.    That won't help the hole in the middle where the cowl bump is, but it should help, and may help #4 a bit.

Edit:  You can see I have slices in similar spots, specifically to fix that problem.

 

Edited August 10, 2021 by EricJ

[dzeleski]

2 hours ago, EricJ said:

Those CHTs aren't terrible, but not great, either.   A simple thing to do to close those smaller holes is just cut a slice from the edge down the middle of where the fold is.   You don't need to cut down the baffle very far, just enough to relieve the bunching that makes that fold so that the two pieces overlap instead.    That won't help the hole in the middle where the cowl bump is, but it should help, and may help #4 a bit.

Edit:  You can see I have slices in similar spots, specifically to fix that problem.

 

Yeah they are not terrible but I know they can be better based on reading other values from other J models. Ill cut a little slit in each of those spots and then maybe Ill cut and bend a small piece of metal and double side tape or RTV or something to seal up that center gap as a test. If that works ill see if I can cut a piece of silicone and get it attached to the baffle.

[EricJ]

36 minutes ago, dzeleski said:

Yeah they are not terrible but I know they can be better based on reading other values from other J models. Ill cut a little slit in each of those spots and then maybe Ill cut and bend a small piece of metal and double side tape or RTV or something to seal up that center gap as a test. If that works ill see if I can cut a piece of silicone and get it attached to the baffle.

If you have some baffle seal material laying around, or borrow some scrap from somebody, you can attach a piece to fill the cowl bump to the existing baffle seal and attach it with the fasteners from aircraft spruce.   No special tools required, just drill a hole for each fastener in the baffles.

https://www.aircraftspruce.com/catalog/appages/cowlsealhardware5.php

[philiplane]

The biggest losses are around the front of the engine. Around the cowl inlets. And around the starter and alternator. The factory left large areas open, and those are where you can make the most gains. 

[dzeleski]

13 hours ago, philiplane said:

The biggest losses are around the front of the engine. Around the cowl inlets. And around the starter and alternator. The factory left large areas open, and those are where you can make the most gains. 

I believe mine are setup correctly and dont have any gaps. Ill double check the next time im down at the airport. Attached an old photo I have of the front of the cowl. Im fairly sure that gap at the front is expected?

[EricJ]

4 minutes ago, dzeleski said:

I believe mine are setup correctly and dont have any gaps. Ill double check the next time im down at the airport. Attached an old photo I have of the front of the cowl. Im fairly sure that gap at the front is expected?

Since you have the ram air delete, you may need to add a strip of baffle seal across the very bottom just below the old ram air inlet.   Otherwise that winds up being a big hole that will let a lot air through.    I just attached a small strip to the one on either side, and it's been working well for several years.

Edited August 11, 2021 by EricJ

[dzeleski]

Some of these have been replaced as they had holes in them and the heat wasnt working that well. What im probably going to do is patch it up and see if I can get a decent improvement to at least get me through summer, winter has obviously never been an issue up here. My annual is up in Dec so ill most likely place an order with you closer to that @GEE-BEE AEROPRODUCTS for a full baffle and scat kit.

[philiplane]

Seal gaps with Dow 736 RTV. Gaps around the starter, where plug wires go through grommets, between the aft baffle and the case, between the left forward baffle and the case, between the case and the #3 cylinder aft baffle, anywhere you see a hole or gap larger than 1/4". 

[Guest]

7 hours ago, dzeleski said:

I believe mine are setup correctly and dont have any gaps. Ill double check the next time im down at the airport. Attached an old photo I have of the front of the cowl. Im fairly sure that gap at the front is expected?

Cover the large holes above the alternator, seal the gaps around the starter, add the missing sealing tape from removing the ram air door, add loads of additional rivets to hold/seal the baffle tapes to the metal baffles.

Clarence

[OR75]

#3 is normally the hottest. if your  #3 is in the 350-380 range .... others are colder 

your #4  T probe may be off (switch them to check that)

[dzeleski]

On 8/10/2021 at 8:11 PM, philiplane said:

The biggest losses are around the front of the engine. Around the cowl inlets. And around the starter and alternator. The factory left large areas open, and those are where you can make the most gains. 

When you say around the cowl inlets do you just mean the baffles near them? I dont have any baffles directly on the inlets.

6 hours ago, M20Doc said:

Cover the large holes above the alternator, seal the gaps around the starter, add the missing sealing tape from removing the ram air door, add loads of additional rivets to hold/seal the baffle tapes to the metal baffles.

Clarence

Crap I didnt even notice the hole where the alternator is. I think the starter is sealed, ill double check. I assume Ill need some aluminum cut into the correct shape for the alternator and rivet it on? Is that part sold or should I just make it myself? Thanks I appreciate the tip

5 hours ago, OR75 said:

#3 is normally the hottest. if your  #3 is in the 350-380 range .... others are colder 

your #4  T probe may be off (switch them to check that)

Thats been tested, both EGT and CHT is high on #4, its strictly a fueling problem way too lean when compared to the other three and a gami test proves that. #4 peaks about 1.5 -2 GPH earlier then the rest.

[OR75]

Not sure I would cover the alternator hole or seal the starter gap . The gap left by removing the ram air should have been filled 

[Guest]

The holes above and around the alternator, gaps around the starter and any gaps between the metal baffles and the engine case decrease cooling efficiency.

Clarence

[philiplane]

57 minutes ago, dzeleski said:

When you say around the cowl inlets do you just mean the baffles near them? I dont have any baffles directly on the inlets.

 

The seals at the outboard baffles are supposed to seal the cowl inlet area so air cannot go around them. Often times, those vertical seals bend backwards and allow the inlet air to go outside of the cylinder baffles.

[ArtVandelay]

The holes above and around the alternator, gaps around the starter and any gaps between the metal baffles and the engine case decrease cooling efficiency.
Clarence

I’m surprised no one mentioned the crack metal baffling?

[Guest]

12 minutes ago, ArtVandelay said:

I’m surprised no one mentioned the crack metal baffling?

What else is wrong with this engine installation?  How good are we at spotting issues?

Clarence

[carusoam]

Dzel,

With one pic…

You got personal recommendations from a top shelf mechanic, A seal manufacturer, and a bunch of MSers who have been there and done that…

And you may have enlightened another MSer that thinks differently…. 

Remember…..All of the air flow is supposed to enter above the cylinders…

Any air escaping out the bottom… is pressure lost from your cooling stream….

or air entering below the cylinders… is pressure working against the cooling flow through the cylinders…

 

Check the offer from GeeBee… looks like he needs a pattern for a seal… you need a seal… you make him the pattern, he makes you the seal…

What a country!

Go MS!

PP thoughts only, not a mechanic…

Best regards,

-a-

[EricJ]

This is what I did after the ram air delete.   The foil tape over the hole isn't very pretty, but it works, and the extra piece of baffle seals closes up what is otherwise a big hole in the high-pressure area.   If you put the lower cowl on you can see a big gap there, assuming the hole in the cowl was patched after the ram-air delete.

The entire front area is high-pressure, so plugging holes there can make a big difference, especially since it feeds the underside of the engine, which you want to be at as low pressure as possible for flow.

Edited August 12, 2021 by EricJ

[A64Pilot]

18 hours ago, OR75 said:

Not sure I would cover the alternator hole or seal the starter gap . The gap left by removing the ram air should have been filled 

When I got my airplane the previous IA had used aluminum tape to completely close out the hole around the alternator and starter, I removed that tape under the assumption that the factory left those rather large gaps for some kind of reason.

I’ve noticed no difference in Fl Summer heat. 

If it would make much difference why didn’t the factory close them off ?

Is there an SL or SB or something from the factory telling us to close off those holes?

Edited August 12, 2021 by A64Pilot

[Igor_U]

 

4 hours ago, A64Pilot said:

If it would make much difference why didn’t the factory close them off ?

 

Well,

Factory did close them off, at least on my '67F. Alternator has a round silicone seal and starter had a black felt seal that partially replaced with cut silicone sheet.

 

[A64Pilot]

I don’t think they did on my J as there are no open holes where fasteners would go.

An issue I can see is by closing off the hole around the alternator are you blocking it’s cooling? You would think if it were beneficial then Mooney would have done it on the J especially if they had done it on previous models. I believe these alternators suck air in through both ends and exhaust it from the sides, automotive alts do and I think these are very similar designs.

 

[carusoam]

Generators got a cooling hose from the front of the cowl…

Alternators typically get a fan mounted on their front…

It is unlikely that a leaky air passage would be intended for use as cooling the alternator…

PP thoughts based on the history of the cooling hose that was connected to the generator…

Best regards,

-a-

[A64Pilot]

Most automotive alternators and I assume ours is likely automotive based, have two fans, and they suck air in from the front and the rear and blow it out out of the sides or middle of you will

Majority of the heat is from the rear mounted diodes, alternators are actually AC, not DC devices and are pretty inefficient, they rectify AC to DC via a bank of diodes and those diodes give off a lot of heat and this heat is why they are inefficient. They are inefficient but relatively lightweight and small.

About all the continuous power that can be extracted continuously from a small frame alternator is about 80 amps at 14V or half that at 28V of course, coincidentally 80 amps is also about the max you can pul from a single Vm belt without it slipping and generating “dust”.

I suspect most of us only draw 15 or so amps continuously so we aren’t pushing the alternators very hard

 

[Guest]

The alternator installed on a J model has no fan, internal or external.  It, like the cylinders relies of the pressure differential from the front side to the back side for cooling.  The holes in the alternator itself shouldn’t be blocked, but the oversized hole in the metal baffle around it can be sealed.

Clarence