Port & Polish?

idahoflier

idahoflier

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idahoflier
Trying to decide if getting new cylinders ported and polished is worth it. I have read is that it's possible to get up to 5 hp/cyl. Conversely I have been told it's only worth doing on an experimental and that on a certified engine there is really no benefit.

Does anyone have any experience with port & polished cylinders?

Thanks!
 
Generally a port and polish means removing some material, either to match gasket openings or simply getting rid of casting flash to improve flow. That where the additional hp comes from. Nobody's going to to that in a type certificated airplane.

So why waste the money?
 
I do think the new conical valve seats are worth the extra.....but, not noticeable.
 
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Chip Sylverne said:
Generally a port and polish means removing some material, either to match gasket openings or simply getting rid of casting flash to improve flow. That where the additional hp comes from. Nobody's going to to that in a type certificated airplane.

So why waste the money?
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My understanding is that's exactly what's being done, removing the casting flash and polishing, which isn't modifying the cylinder since it is still conforming to the design and thus allowed my the FAA. Some people are doing it, that's why I'm asking...
 
unsafervguy said:
With the crappy induction design of aircraft engines I doubt it will help much at all.
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Plus, they're a low speed engine. Under the conditions that aircraft engines operate in I'd expect to see very little, if any benefit. The exhaust systems are typically poor as well, further complicating matters.

I've overhauled one O-320 with cylinders that were "ported". I didn't see enough difference in the ports between before and after to make it worth it. There were too many changes implemented at the same time to say that the head work made any power improvement.
 
Ask the shop that's selling you the jugs if they've flow tested the heads before and after, and what the increase is, not the " hp". Bet it's not enough to make any difference. I mean, if they aren't modifying the head, there's not going to be much difference.
 
I know a guy who did something like that....and he say's he can't tell the difference. :D
 
We ported and matched the cylinders in the O-200 in our Experimental VariEze.

No idea how much power it made, but the static RPM increased by 100-ish RPM...
 
It might become a dollars per knot question (ie $1200/3kts) minus costs (direct costs of the P&P, plus loss in engine lifespan costs)
 
Bunch of stuff on the Van's board. Found a .pdf report that flowed an O-320 cylinder increase around 11.4 cfm intake, nearly 14cfm exhaust, which is more than I would have expected from a simple p&p with no bowl work.

No idea how that translates into increased bmep though.
 
The idea that porting and polishing works better for experimentals has to do with high compression. Better induction is more important to a guy running 12:1 or 10:1 than a stock engine at 7.5:1. But, Titan and Millennium cylinders are flow matched and set balanced. They work better than stock. Ly-Con makes a living correcting factory cylinders. Continental bought ECI and adopted ECI manufacturing (Titan) for their cylinders. Lycoming is in the middle of retooling to do their own cylinders now. If they make them better from the start there's less room to improve them. More horsepower? Engine shop claims about horsepower are hard to believe. 320 CI at standard compression at 2700 rpm makes X power. Port and polish may make it smoother and more efficient but big power increases don't make sense.

Horsepower isn't what turns a prop. Torque does. There's no replacement for displacement.
 
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General doctrine now is polishing harms air/fuel mixture. Some texture promotes turbulence in keeping fuel better atomization. This is true across all gas engine types. Porting helps if the purpose is to promote consistent flow matching between cylinders. Removing casting flash and other inconsistencies between cylinders helps the engine run smoother. Generally head work helps with the greater the RPM. Our aircraft engines operate at a relatively low RPM. Race engines like LyCon builds operate at 2x common RPM in our factory aircraft. My MX races planes in Reno and his Lycoming runs 4000 rpm. The engine is rebuilt after each race.
 
Stewartb said:
Horsepower isn't what turns a prop. Torque does. There's no replacement for displacement.
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Please, not this misunderstanding again. It takes power to perform work. I can get you ten million foot pounds of torque at the propeller, but it will be turning too slowly to even see! To turn it fast enough to fly, you need horsepower. Horsepower is a function of torque times RPM. Power moves things.
 
Local guy is having it done on his Carbon Cub engine. I will report back with his results but I too am skeptical. Given the low RPM these engines run at, increased airflow is not likely to help much. Displacement, compression, and cam profile make the biggest difference in the lower rpm range. Flow numbers and a/f ratio start to make up the upper power band.
 
Kenny Phillips said:
Please, not this misunderstanding again. It takes power to perform work. I can get you ten million foot pounds of torque at the propeller, but it will be turning too slowly to even see! To turn it fast enough to fly, you need horsepower. Horsepower is a function of torque times RPM. Power moves things.
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Hod rod an 0-320 to 180hp and put it next to an 0-360. The 360 will spank it. Proven over and over and over again.
 
Stewartb said:
Hod rod an 0-320 to 180hp and put it next to an 0-360. The 360 will spank it. Proven over and over and over again.
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Your reply doesn't exactly fit my post, unless you are talking about the area under the curve, which is a different story. But if you run two engines at peak horsepower, and they both make 180 hp at 2700 rpm (so you've got your prop set to 2700), all else being equal, they will move an identical airplane in an identical manner.
 
By the way, Lycoming's Thunderbolt shop (exp engines) ports, polishes, and balances all their engines. Can't wait to get my Thunderbolt IO-390!


Kenny Phillips said:
Your reply doesn't exactly fit my post, unless you are talking about the area under the curve, which is a different story. But if you run two engines at peak horsepower, and they both make 180 hp at 2700 rpm (so you've got your prop set to 2700), all else being equal, they will move an identical airplane in an identical manner.
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But they don't. Go figure!
 
Stewartb said:
By the way, Lycoming's Thunderbolt shop (exp engines) ports, polishes, and balances all their engines. Can't wait to get my Thunderbolt IO-390!



But they don't. Go figure!
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No figuring required; they aren't putting the same power into the propeller, period. Aftermarket companies have been know, occasionally, to exaggerate.
 
I agree about dyno ratings, but I'm not interested in arguing.

To the OP, I just got off the phone with the Thunderbolt shop and was told in my 390 port and polish adds 3-4 horsepower total. That's not what I called about and that info was coincidental to the conversation. I called about compression ratios. The P&P's 3-4hp gain is consistent for 8.9:1 and 10:1 engines. The compression increase adds about 10hp. Makes sense. The difference between a 150 and 160 hp 0-320 is compression, and it does make a noticeable difference.
 
I don't think I've ever heard anyone say "I woulda ( fill on the blank) if I just had that extra 3 hp".
 
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