M20J Speed Improvement?

[jaylw314]

10 minutes ago, INA201 said:

My thought on speed is practical in nature. I bought a Mooney for its history, looks, efficiency, cool factor, safety, and of course speed(ego maybe).  My philosophy is to restore it as close to the way Mooney designed it to be without breaking the bank while modernizing the electronic side.  I’m satisfied with 156knots but in the back of my mind there is always a desire to go for more. That being said if you need a new engine why not add the port and polishing to it along with balancing it all out.  Also, if I had needed a total new exhaust instead of a $750 repair I probably would go for the nicely designed power flow for a little more. If it was time for a totally new magneto it may be worth considering Electronic Ignition to bring digital timing advance into play.  If you like tinkering and a little extra work add a turbo for fun and let us know.  A lot of the real tinkerer types don’t always show up on forums so who knows what other folks have done to speed up.  There is always more but we’ve already got an A on the test by buying a Mooney.  Studying an extra ?? hours to make an A+, who knows?  

There are a bunch of people who've added PowerFlow exhausts (although I'd say it's not just a "little more" than $750).  I recall @xcrmckenna just added one to his J recently?

I recall there was an FAA AC or some kind of statement published recently about their concerns regarding multiple STC modifications, with the caution that while one STC modification results in known changes, multiple ones may result in unknown changes.  Kind of like quantum mechanics and medication interactions ...

Edited June 20, 2019 by jaylw314

[jetdriven]

Nobody has really quantified any speed improvement with J poweflow exhaust. M20C models, however, have real and serious gains.  

Maybe the J exhaust is already so optimized that it can’t really be improved on much. 

[xcrmckenna]

There are a bunch of people who've added PowerFlow exhausts (although I'd say it's not just a "little more" than $750).  I recall [mention=12769]xcrmckenna[/mention] just added one to his J recently?
I recall there was an FAA AC or some kind of statement published recently about their concerns regarding multiple STC modifications, with the caution that while one STC modification results in known changes, multiple ones may result in unknown changes.  Kind of like quantum mechanics and medication interactions ...

Upgrades are a disease, even if I think the $3,900 for my power flow should have gone elsewhere in the plane...


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[KSMooniac]

Testwest here has done extreme drag reduction on his 77 J and gets 165 KTAS at 10 GPH. That's the best I know of...and he's a pro test pilot so I believe his numbers.

Off the top of my head, his mods are:

Later model overhead vent retrofit, plus replace fuselage skin to delete pop-up scoop

F/G smooth belly (may have antenna inside)

Wing tips with nav antennas inside/cat whisker delete

Forward COM antenna delete

LoPresti cowl

Hartzell Top Prop

F/G low profile lower gear doors/caliper rotation/aft blister delete

Optimal rigging

He hasn't repainted, either, so new jetdriven-quality paint might bump that up a bit more! Roy LoPresti was an aero design genius and went after drag reduction first and foremost when turning the F into the J. That formula still holds true today for the speed/efficiency freaks! We have more to work with than he did in 1975...but it takes effort and money.

If you like to tinker, get after the rigging of gear doors and control surfaces. Check cowl fit and repair as needed to keep it from riding up (like mine!) and creating a step behind the spinner. Get rid of obsolete antennas, beacons, etc. Keep it clean. Remove dead weight. If re-doing interior, consider non-leather to save weight. Put some ballast in the baggage area (like a couple gallons of water) to move the cg aft if you don't have folks in back. It all adds up to more speed!

Or be happy with what you have! Starting with any Mooney of puts us at the top of the efficient speed class. 5 knots more cruise speed only saves ~5 minutes on a 350 NM flight at typical J speeds. Will you spend 10 AMU to do so? I won't answer.


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[OR75]

5 hours ago, jetdriven said:

How much more is the 390 vs the 360 and how much is that prop that has to be used with it?

a few years ago we looked at it. The prop was 10k and the engine was also around 10k more. No overhauled ones were available. Rebuilt was but it was expensive. 

The engine difference is gone. The prop requirement is still there.

Obviously ... YMMV .... i am not sure I would consider the IO-390 if i did not already have a Hartzell scimitar prop

But this is where i am coming from: 

My square tipped McCauley C212 needed to be overhauled (classic oil mist on the cowling signal). It was found the be non-overhaul "able" then, so instead i just re-sealed it (used C212 blades are not easy to find) . After a few years, I made the jump and got a Hartzell prop. The bonus was getting rid of the yellow arc on the tach.

With over 2200 hours my IO-360-A3B6D still purrs like a good old engine  (and compressions and UOA are great). It does get regular exercise.  Honestly, I think the accessories (mags, governor, rubber mounts, ...)  will need work before the engine.    

Options:

stay with the IO-360-A3B6D    (direct swap)

go to the IO-360-A3B6  ($3000 cheaper than the A3B6D but some of that saving will be spend on brackets and change to governor settings)

go the IO-390-A3A6 ($3000 cheaper that the A3B6D but some of that saving will be spend on brackets and change to governor settings - so same as A3B6)

with the prop question out of the way, the only drawback for me will be : slightly higher fuel consumption for a  few more HP ? and less a less proven engine platform ?

 

 

[Oldguy]

Unless I have to do a top overhaul in the next year or so (my engine has developed a slight drinking problem), I am looking at the same choices in about 4 years, and I am leaning towards the IO-360-A3B6 and putting the electronic mag on it to retain a little more power/efficiency at altitude. From what I have read and can recall, the benefit you get from the 390 fades after a specified amount of time as you have to pull back on the RPM (someone correct me, please, if I am wrong - this is recalled memory). Fortunately, there have been others before us who have done the A3B6D/A3B6 swap to document most of the problems you incur when doing it.

My ideal-money-is-not-a-problem swap? Find a NIB turbo normalizer for the A3B6 and strap it on the engine. 

But I figure a 252 would be about the same cost...

[Hank]

What a coincidence!!

 

[wcb]

2 hours ago, Hank said:

What a coincidence!!

 

Are you saying the best speed improvement for a J is ...... wait for it ........  is a K?

[jetdriven]

6 hours ago, Oldguy said:

Unless I have to do a top overhaul in the next year or so (my engine has developed a slight drinking problem), I am looking at the same choices in about 4 years, and I am leaning towards the IO-360-A3B6 and putting the electronic mag on it to retain a little more power/efficiency at altitude. From what I have read and can recall, the benefit you get from the 390 fades after a specified amount of time as you have to pull back on the RPM (someone correct me, please, if I am wrong - this is recalled memory). Fortunately, there have been others before us who have done the A3B6D/A3B6 swap to document most of the problems you incur when doing it.

My ideal-money-is-not-a-problem swap? Find a NIB turbo normalizer for the A3B6 and strap it on the engine. 

But I figure a 252 would be about the same cost...

It’s limited to 27.2” continuous MP after the 5 minute takeoff limitation.  So it’s really a 200 hp continuous engine with a 210hp takeoff rating 

[gsxrpilot]

1 hour ago, jetdriven said:

It’s limited to 27.2” continuous MP after the 5 minute takeoff limitation.  So it’s really a 200 hp continuous engine with a 210hp takeoff rating 

One question I've had about this is... I know that N/A engines lose MP with altitude. If one was to take off with full MP at 210hp and just keep climbing, would one expect the MP to be down to 27.2" within the first 5 minutes? And would that then mean that while the IO360 would make 200hp at sea level but only 180hp by 6000 ft, the IO390 making 210 at sea level would be at 200 hp by 6000 ft?

I don't know if this makes sense to anyone. I'm ashamed of my attempt at explanation.

[Jerry 5TJ]

Best way to get your Mooney to go faster is to trade it for a faster Mooney.  

[jetdriven]

2 hours ago, gsxrpilot said:

One question I've had about this is... I know that N/A engines lose MP with altitude. If one was to take off with full MP at 210hp and just keep climbing, would one expect the MP to be down to 27.2" within the first 5 minutes? And would that then mean that while the IO360 would make 200hp at sea level but only 180hp by 6000 ft, the IO390 making 210 at sea level would be at 200 hp by 6000 ft?

I don't know if this makes sense to anyone. I'm ashamed of my attempt at explanation.

Yes it will climb 3000’ in less than 5 min and be below 27”. 

The engine at full throttle makes 5% more Hp. At every equivalent power setting it’s 5% more. 

So at the power settings we cruise at, it’s 7.5hp extra at 75%. And 6hp more at 60%. 

[201er]

18 minutes ago, jetdriven said:

Yes it will climb 3000’ in less than 5 min and be below 27”. 

The engine at full throttle makes 5% more Hp. At every equivalent power setting it’s 5% more. 

So at the power settings we cruise at, it’s 7.5hp extra at 75%. And 6hp more at 60%. 

7.5HP? That's only worth 2 extra knots or not even 100fpm in the climb???

[flyer338]

The delta for speed mods between cost and speed increase is really defined by how much labor one has to buy. The ‘65 C I used to own cruised at 23” / 2400 rpm (65% power - 8 gph) at 140 ktas. After adding the following mods: 201 windshield, cowl closure, smooth belly, flap gap and aileron gap seals, all three tail mods, and moving one com antenna, and the transponder, DME, and ELT antennas inside, I had 152 ktas cruise at the same power setting. The useful load took about a 90 lb. hit. I did the work myself under appropriate supervision. The total cost (1996) was around 6 AMU. That was more than paid back in reduced fuel cost over the next 500 hours. 

An unlooked for benefit was a 50% increase in rate of climb - initial rate of climb at sea level went from 700 rpm to 1100 fpm. The airspeed indicator in that plane read fast; at 1000 feet at 2700 rpm and wide open throttle, I cruise at 189 mph indicated. A four-way gps showed it was only 182 mph. The stall speed was also slower; at 2300 lbs. the plane stalled power off in the landing configuration at 49 mph CAS. 

The glide ratio was also better at more than 13:1.

I more than got the value of my money and my time.

[INA201]

 

That’s impressive!

Where did the 90lbs go?  Seems like the 201 windshield and cowl enclosure wouldn’t add too much.

[flyer338]

It has been a while, but as I recall the one-piece belly pan was a lot of it. And the other mods each added a little; it adds up. I may still have electronic copies of the 337s. I will look and see if I can find the actual numbers.

The windshield also greatly improved visibility in turns and made it quieter inside.