Airworx 180HP O-300 STC

[GAHorn]

….

Also, higher octane fuel IS NOT higher energy than lower octane fuel. Higher octane fuel simply allows a higher compression ratio without causing pre-ignition or detonation, and the resulting engine damage. A given engine produces no more power with higher octane fuel than it does with the octane for which it is rated.

I knew immediately when I posted …that particular choice of words was wrong and almost edited it right-away. Yes, I’m completely in agreement as to what octane numbers mean and why. That was just a quick-and-dirty comment which was intended to refer to the higher efficiency of higher compression.

Displacement is the volume moved by the piston. Either the volume sucked in through the intake valve (assuming perfect conditions of course), the volume displaced by the piston on the compression stroke, or the volume pushed out through the exhaust valve. Simply bore cross sectional area x stroke (x number of cylinders).

If an original piston sitting at the bottom of an original cylinder…times six…equals 300 cu. inches…. then how can a taller piston which takes up more space inside the cylinder…. also equal 300 cu. Inches.

You are confusing displacement - the volume "displaced" by the piston with the total volume of the cylinder. The volume of the cylinder is displacement plus combustion chamber volume (the volume above the piston at top dead centre). The taller piston will reduce combustion chamber volume but not change the displacement (bore cross section x stroke).

Think of the 0-300 as having six pistons which each displace (move) about 50cu in. on each stroke. It doesnt matter at all what the remaining volume in the cylinders is.

Taller pistons will increase compression ratio (The ratio of (displacement + combustion chamber volume) / (combustion chamber volume)) as the combustion chamber volume is smaller. Higher compression ratio gives more power, as well as more risk of detonation and more load on the bottom end.

….. It’s the definition of displacement which (was) not making sense to me. As I suggested earlier, this confusion was a matter of terminology. Thanks for clarifying it daedaluscan and Miles.

Soo….the better way to have said my first post would have been not to use the word “displacement”…but instead to comment that cylinder VOLUME is reduced if taller pistons are installed.

Yes, I can see that any increase in HP would also increase the load on the lower-end of the engine. But the important parts of that lower end were sufficiently robust to accommodate their identical brothers in the 175 HP GO-300 engine, and the same crankshaft is used in the IO-360 which can be rated up to 210, soooo… it will be interesting if they can boost the HP of the O300. It still brings up the issue of a fixed-pitch prop vs constant speed.
It seems to me that this engine is limited more by it’s prop RPM than by it’s compression ratio, and increasing its’ compression ratio will likely prevent it’s use of mogas for those who like to use it….. while any performance increase of the aircraft which utilize the O300 will likely be poorly documented (like many other mods) and any actual change (personal prediction) will be almost negligible.

When I take out all the junk I carry in my baggage compartment it’s amazing how much better the airplane performs.

[daedaluscan]

I am very happy with my O-360 conversion, but might have been tempted by this solution. To be honest the O-300 with the 80x42 was a great performer at sea level and light. A bit more horsepower at a smaller investment would have been very tempting. Interesting to see where this goes.

[Fishsticks]

I am very happy with my O-360 conversion, but might have been tempted by this solution. To be honest the O-300 with the 80x42 was a great performer at sea level and light. A bit more horsepower at a smaller investment would have been very tempting. Interesting to see where this goes.

Yes! This is the commentary I was looking for!

I'm sure any of the 180-210 HP conversions with a composite CS prop are going to stay at the top of the heap performance wise. But they are also at the top of the heap $$$ wise. It would be nice if there was middle ground available.

[rschreiber]

Looks like Airworx just posted a video of the O-300 on their dyno. Initial reports are 164HP, looking at about 172HP after break-in. Also looks like he’ll sell the STC to anyone with the caveat it is applied during engine overhaul.

https://airworxaviation.com/blog/

[GAHorn]

I see that pic of an engine on their dyno.. No baffling? No fans? How do they prevent local overheating? That would be concerning on a new engine.
(might be the wifi I’m on today…no other pics display)

What rpm do they obtain that HP rating on an O-300? (I’m thinking a typical installation using a fixed-pitch prop will not produce that kind of RPM or HP.)

[mmcmillan2]

I see a big centrifugal blower with ducting terminating above the crankcase.

From what I understand it’s higher compression.

[voorheesh]

Lycon in Visalia, CA can perform “port & polish” on new Continental cylinders and I recall reported 159hp on their dyno for an O-300 some years back. Is that a credible claim?

[rschreiber]

I see that pic of an engine on their dyno.. No baffling? No fans? How do they prevent local overheating? That would be concerning on a new engine.
(might be the wifi I’m on today…no other pics display)

What rpm do they obtain that HP rating on an O-300? (I’m thinking a typical installation using a fixed-pitch prop will not produce that kind of RPM or HP.)

The blog links to a Facebook post with a more detailed video. The owner also answers a lot of questions in the comments section. It’s early in the process, and he has a lot of testing and evaluation to complete before there’s a full picture of what this STC will or won’t provide. I think you make a great point about needing an apples to apples comparison of a stock O-300 and his STC engine. That being said, I’m highly doubtful that a stock O-300 would register 160+ HP on a dyno. Early testing seems to show a significant improvement in performance. I’m thrilled that anyone is willing to try and improve on this 75+ year old technology while operating within the confines of the STC certification process. I’m interested to see what propeller options the STC will allow.

[lowNslow]

Lycon in Visalia, CA can perform “port & polish” on new Continental cylinders and I recall reported 159hp on their dyno for an O-300 some years back. Is that a credible claim?

When I had my engine rebuilt some years ago at Lycon I had them do the port and polish, it did 157hp on the dyno.

[GAHorn]

Lycon in Visalia, CA can perform “port & polish” on new Continental cylinders and I recall reported 159hp on their dyno for an O-300 some years back. Is that a credible claim?

When I had my engine rebuilt some years ago at Lycon I had them do the port and polish, it did 157hp on the dyno.

At what RPM? If you turn this engine up to 3200 RPM it’ll put out 175 HP. Continental and Cessna did this with the C-175 SkyLark.

The problem with reports and stories that claim increased horsepower is that this engine is usually run with a fixed-pitch propeller that is pitched to keep the engine within certain hp ratings…and the Type Certificate insists on those specs. To run this thing on a “dyno” and claim an extra 12 HP was produced is meaningless drivel (IMO) when your dyno is allowed +or - the same percent error in it’s instrumentation …or the atmosphere that day was anything other than standard. (Other than standard baro-pressure or O.A.T. on a dyno which has no rpm limiter such as a prop puts on the engine can result in a different HP output. Even Continental allows up to 10% “overspeed” on this engine with absolutely NO penalty or repair-scheme. If I deliberately …or inadvertently….or due to instrument-error…or simply “enthusiastically” for sales-promotion purposes…overspeed this engine by 8% (2700 RPM) then I can “dyno 157 HP” also.)

[DaveF]

Increasing RPM isn’t the only way to increase power. Power is RPM times torque. More push per power stroke will give more power at a given RPM. Anything that allows the engine to burn more fuel/air will increase torque. That could be increased displacement or volumetric efficiency, or turbocharging. Porting and polishing improves volumetric efficiency. Torque can also be increased by increasing the compression ratio. You’d need a higher pitch on the prop to take advantage of the power, but a dyno doesn’t use a propeller, so it can measure power irrespective of which propeller you ultimately need. Your points about standard test conditions and instrumentation accuracy are valid, but not the main issues here.

[GAHorn]

…, but a dyno doesn’t use a propeller, so it can measure power irrespective of which propeller you ultimately need….

Exactly…. hence my question…at What RPM did they claim an additional 12 HP? (Torque is rated/varies in accordance with RPM. It will increase with RPM at a given rate…then decrease as RPM is further increased.)

HP can be increased by volumetric efficiency…? I doubt that anyones’ dyno can make that apples-to-apples comparison. They’d have to take your engine with and without the polished ports with absolutely no other differences in atmosphere, temp, and dozens of other things exactly equal…to make that claim. (Some racers actually rough-UP their inductions to improve atomization of the fuel/air mixture. Polishing that induction may actually decrease efficiency if asked that of those racers.)

However, by definition: “ The volumetric efficiency is defined as the ratio between the actual (measured) volume of intake air Va [m3] drawn into the cylinder/engine and the theoretical volume of the engine/cylinder Vd [m3], during the intake engine cycle.”

Polishing/porting does not increase volume (displacement) of the piston/cylinder mechanism. Further, increased RPM actually reduces the time allowed for the intake-stroke thereby reducing effective volume. (I.E. the intake valve is mechanically closed before the incoming fuel/air baro-pressure has equalized.). There are folks who actually believe that the original direction of the scarf-cut of the tailpipes-orientation makes a measurable difference in output.

If you were to turbo-charge or supercharge this engine what you are saying would be correct.

I believe Continental knows more about their engine than anyone…and Continental states that the rated horsepower of this engine under standard atmospheric conditions is determined solely by RPM.

I guess we will have to agree to disagree on any measurable benefit of the modification made to intakes/exhaust ports of this engine. The benefit/penalty of relationships …or HP sales-claims …is not worth arguing, and I don’t mean to do that. I’m only expressing a personal opinion as it applies to this sort of engine mod versus cost.

[ghostflyer]

If one examines the surface finish quality of cylinders between Superior and Continental cylinders ,you would find the continental is rough and all the passages are not uniform in shape in comparison of cylinders. One of my continental cylinders was flow checked before and after the port and polishing as I was a skeptic and didn’t want to spend an extra $4800 on all 6 cylinders . While it’s not that important on the exhaust port but one of the cylinders exhaust had a large lump and part of a casting mark inside . I can’t remember the improved figures for my ported and polished cylinders [over 10 years ago] . However I have been told that continental cylinders have picked up their quality control. This is NOT an add for superior parts but they do have better quality product. I have all Superior cylinders these days and it wasn’t worth the extra $ for porting and polishing .

[dstates]

I, for one, am just glad someone is working on improving the O-300 series engines (and supporting them) when there are some well known engine shops that won't even overhaul them anymore. We'll have to vet out their STC when it is complete, doing so now is all just discussions on unknowns unless you have talked to them.

[Poncho73]

I very interested in the Airworx STC. Although my engine is around 1000SMOH so changing the engine is not on my short list, yet.... My neighbour at my home base airport has an early 172, under the owner maintenance category, (Canada). He just picked up an overhauled 0-300 that has been massaged with the C-85 pistons and intake porting clean up. I'm very interested to see how it performs when finally installed. I think a more interesting comparison would be having two identical 170's line up, one with the Airworx engine and one with a stock 0-300, identical props and same weight and let them have at it. Without that kind of "shoot-out" it would be hard to discern any major change.