0-320 h.p. increase, help wanted

[redrooster]

Nobody mentioned electronic ignition. The guys that have them seem to like them. I'm pretty old-school but it's hard to argue with results. Makes sense that constantly tweaking the timing (instead of fixed timing like a standard mag) would be a good thing, even if it was just advancing the timing along with the rpm. I don't know what all controls the timing on a Lightspeed (or whoever) ignition. One mag & one electronic seems like the best of both worlds.

 

[bob turner]

I am sure nobody has forgotten - I am the Cub pilot who cannot discern any performance increase with the Thrustline change, I am also a pilot who thinks the 160 conversion is a red-hot deal,

So my buddy just traded his high time O-320 for a factory new O-360. I have not flown it much, but my first takeoff I could tell the difference from the moment the throttle was opened right on through the spectacular climbout. Maybe it was a comparison between a 1500 hour engine and a new one, but the old engine had good compression, good accessories, and a Borer prop. The change is simply dramatic! I was not expecting such a change.

 

[Carey Gray]

So, you're saying that the O-360 puts out more power than the O-320.
I'll be damned.

 

[gander]

If your gonna put the money and effort into hott rodding a engine do a 0360 parallel valve. hands down.
The extra weight difference can be made up in lite weight cowling components, my limited experience with both is a hott rodd 0320 gets off only slightly shorter but climbs like a homesick angle and a hott rodded 0360 accelerates a whole lot faster gets off shorter and climbs even better.
Has any one done any ceramic coating to the combustion chamber, piston, exhaust ports?

 

[willyb]

0-320 h.p. increase,help wanted

T.J.

You asked the question
At any given compression ratio, what is the octane rating fuel that is required?

To the best of my knowledge there no set in stone numbers or formulas that will give an absolute octane requirement.
Octane is an anti detonation rating.The factors which can cause an engine to detonate are numerous and vary with engine design and operating conditions.
Mechanical compression ratio is a misleading number.
Cylinder pressure under compression varies greatly with the overall ability of a given engine to fill the cylinders.The more air and fuel it can take in the higher the pressure at Top Dead Center.
Air filter/box,intake design,port layout,rod length,deck height,squish velocity,piston dome configuration,exhaust efficiency,ignition timing,cooling capacity and so much more.
How you load the engine is also a big factor.This is how the factory tests an engine.They put it on a dyno under controlled conditions and and keep increasing the load on it pushing it until it detonates.

Modern auto engines use an anti knock sensor.If the engine starts to detonate it will via the computer back the ignition timing instantaneously to stop it from doing so.When it stops it will put the timing back in.This is one reason that modern cars can obtain good power from poor gas.
They also use manifold pressure and oxygen(rich/lean)sensing.
I believe the Lightspeed ignition uses Manifold pressure sensing to alter the timing curve to load.

By the way if any of you want to get noticeably better gas mileage from your cars go to you auto parts store and get a vacuum gauge or use a manifold pressure gauge.Plumb it into the intake.Now alter your driving to keep the gauge as close to what it is at idle as you can.Fuel mileage will go up,guaranteed.Gas engines only.

Didn't mean to get long winded

Bill

 

[KevinJ]

LY-CON has put High compression pistons in engines that were hooked up to read cylinder pressures with special made sparkplugs while on the dyno and found that the cylinder pressures were less than stock compression at cruise RPMS! But at full power the pressures were a lot more than stock. I found this interesting. Palhal

Old thread…..Can anybody shed more light on the how’s and whys of this?

 

[BC12D-4-85]

Old thread…..Can anybody shed more light on the how’s and whys of this?

Maybe they refer to the average cylinder pressure measured versus short peak pressure during the combustion cycle? Higher compression should result in lower CHT and EGT. That's due to less fuel needed to make the same torque/prop rpm (with more efficient/quicker burn = lower CHT), and less still burning when the exhaust valve opens (= lower EGT). I don't see how you make equivalent torque with less peak pressure, but my engineering is in fish.

Why fish? Dairy farmer grandfather said whatever you do for work make sure you can eat it.

Gary

 

[Steve Pierce]

Getting nervous it might blow up?

 

[KevinJ]

Getting nervous it might blow up?

Ha. Nah. With our DA up here most of the year it’s hard to crater one. You can melt one however

 

[RaisedByWolves]

Maybe they refer to the average cylinder pressure measured versus short peak pressure during the combustion cycle? Higher compression should result in lower CHT and EGT. That's due to less fuel needed to make the same torque/prop rpm (with more efficient/quicker burn = lower CHT), and less still burning when the exhaust valve opens (= lower EGT). I don't see how you make equivalent torque with less peak pressure, but my engineering is in fish.

Why fish? Dairy farmer grandfather said whatever you do for work make sure you can eat it.

Gary

Should, but doesn’t. More HP=more heat. And fuel. Plan on 1.5-2gph more with 10:1 on a 320. And replacing valve guides at 300
Hrs. Oh and more metal from piston skirt wear. I don’t think I could tell any real performance difference. Besides spending time trying to get rid of CHT heat. And oil temp. Made wide cowl doors, seaplane lip on the bottom of the cowl. Couldn’t get below 430 in cruise.

 

[RaisedByWolves]

Getting nervous it might blow up?

Heck if i had Kevin’s money I wouldn’t worry about the fuel burn, or top overhauls every 300 hrs

 

[BC12D-4-85]

Keep the engine the same just increase compression. Same prop at same cruise rpm full rich should burn less fuel if more efficient and temps should drop. A fish told me his did, and others that converted to 160 here.

Gary

 

[pa11driver]

Should, but doesn’t. More HP=more heat. And fuel. Plan on 1.5-2gph more with 10:1 on a 320. And replacing valve guides at 300
Hrs. Oh and more metal from piston skirt wear. I don’t think I could tell any real performance difference. Besides spending time trying to get rid of CHT heat. And oil temp. Made wide cowl doors, seaplane lip on the bottom of the cowl. Couldn’t get below 430 in cruise.

That is very different than my experience: My high compression 0-320 didn’t run hot, didn’t burn measurably more fuel at the same power settings, had loads of power, and had perfect compression when I sold it and still has never had a cylinder off in close to 1,000 SMOH today. It’s a great motor.

 

[BC12D-4-85]

Maybe the secret is go from 7:1 to 8.5:1 and not higher? Eventually high compression may increase internal loads and friction, and take more fuel to overcome compression in cruise. Good power at takeoff but not good for cruise fuel burn and wear plus more heat?

Gary

 

[pa11driver]

Maybe the secret is go from 7:1 to 8.5:1 and not higher? Eventually high compression may increase internal loads and friction, and take more fuel to overcome compression in cruise. Good power at takeoff but not good for cruise fuel burn and wear plus more heat?

Gary

Maybe, but I had 10:1’s on a motor built by Lycon, not retrofitted with just the pistons.

 

[RaisedByWolves]

That is very different than my experience: My high compression 0-320 didn’t run hot, didn’t burn measurably more fuel at the same power settings, had loads of power, and had perfect compression when I sold it and still has never had a cylinder off in close to 1,000 SMOH today. It’s a great motor.

Lycon port and polish and they installed the pistons. 300 hrs the guides and seats were worn, low compression. Couldn’t get under 430 in the summer on floats. Had to keep the fuel to it to stay at 430. 10.5 gph at 2400. Climb on floats I tried not to look at the cgr.
Back to 160 Hp but still have port and polish. The engine builder who replaced the guides and seats said lately lycoming seats are real thin. Said it’s really common. Happens much quicker with 10:1’s.
With the 8.5 it will touch 400 in a climb and come back down to 380’s. Spread now is 15 between the cylinders. 8.5gph in cruise too.

Plus side of the 10:1 is it burned 1 qt between oil changes.

 

[BC12D-4-85]

Would retarding the timing helped with the heat? It seems like it becomes a game of fuel burn, heat, wear, versus performance. Without a CS prop it gets even more complicated choosing the rpm range and MP that works best.

Gary

 

[bob turner]

I love the B2B. Just brought a 160 Citabria back from Denver - 6.2 gph. Runs like a watch; pulled really good to 11,000 feet over Angel Fire.

If I was wealthy, I would pull the IO 360 off my Decathlon and put a 160 on it. It would take a field approval, but it would be a better aircraft, considering I do not need vertical roll capability.

 

[KevinJ]

Heck if i had Kevin’s money I wouldn’t worry about the fuel burn, or top overhauls every 300 hrs

If I had that kind of money I’d just buy an MD500

 

[DENNY]

The math for adding horsepower mods is not cumulative. On a stock engine a single mod may give you 5-10 HP but as you stack the mods the return is less per mod. Mods that seem to have little downside are Exhaust, Porting, and intake. Done correctly you can lower EGT/CHT at the same time. Add the prop right for the mission you can have trouble free flying and fun. Hight compression pistons can also cause issue with props, advanced timing seems to be good for 10-20 rise in CHT.
DENNY

 

[RaisedByWolves]

Would retarding the timing helped with the heat? It seems like it becomes a game of fuel burn, heat, wear, versus performance. Without a CS prop it gets even more complicated choosing the rpm range and MP that works best.

Gary

I went to 20 from 25, didn’t see a noticeable difference.
Surefly variable timing on the left mag, switched it to fixed, retarded both to 20, no noticeable change in cht.

 

[BC12D-4-85]

RBW...what did the EGT temps do/change when you went from 10>8.5:1? CHT dropped so might as well learn something about the exhaust while on topic.

I guess a CS or GA prop could help balance cruise speed and cooling vs performance and fuel burn. There comes a point when the Cub hits hull speed anyway, but at 85 they run hot with a long flat FP prop in my experience. I had a 80" CS on a Citabria A2B that would do 130 WFO and cruise over 100. Even with external loads on floats it never got hot - CHT or oil. Scout-type air adjustable lower cowl flap helped.

Gary

 

[Steve Pierce]

Heck if i had Kevin’s money I wouldn’t worry about the fuel burn, or top overhauls every 300 hrs

He can't make that money if his airplane is down. Those horses and donkeys need their shoes and Kevin needs the fragrances and to keep his back limber. I am envisioning a certain picture he sent me of an uncooperative donkey. Different than those corporate first officers sipping coffee in the right seat. 8)

 

[RaisedByWolves]

He can't make that money if his airplane is down. Those horses and donkeys need their shoes and Kevin needs the fragrances and to keep his back limber. I am envisioning a certain picture he sent me of an uncooperative donkey. Different than those corporate first officers sipping coffee in the right seat. 8)

It took me awhile, but work smarter not harder.

 

[Thiago]

Luke; A popular local Cub re-builder has this set up on his PA-18 and has it signed off as legal. It's an O-360 sump that centers the carberator on the engine and makes all the riser tubes from the sump to the cylinder intake ports the same length. This is part of the difference in an O-360.

The O-360 riser tubes are also larger in diameter then the O-320 risers. This lets the engine breath easier on intake. He has a 3" tail pipe on an Atlee Dodge stock muffler. I personally think 2 1/2" is large enough on the tail pipe, 2" is stock. With an 82/46 borer prop he claims it turns 2800 rpm wide open and 2500 static.

Shaving the cases to gain compression ration with legal pistons came from another source but is still legal.

There is a lot more you can do to an O-320 if you were experimental but this is about it in a certified Cub. As for me I have gone the O-360 route and still really like it. I have another friend that built up a hopped up O-320 PA-18 like mentioned above. He then built up another PA-18 with an O-360 in it. He sold the hopped up O-320 Cub a while later. He told me the O-360 Cub "did everything better". In my opinion (other then landing, and here they are about the same) it does. Take care. Crash

Rookie (dumb) question but how do you find out what model of 0-360 sump fits an 0-320 A2B narrow deck ? Thanks for all the good info you always share here.

 

[Paul Heinrich]

Spitballing here, but has anyone ever tried running a hose into the carb box that is connected to the regulator of a supplemental oxygen tank? You could use the extra oxygen when operating out of high altitude airports or when a performance take off is required. Kind of like the way muscle cars use nitrous but without the risk of overboost.

I don’t remember seeing any restrictions in the paperwork from Lycoming or the Faa that would prevent you from adding oxygen to improve the air quality going into the engine.

You’re not looking at a double digit performance increase, but you might find enough extra umph to make a difference.

I dunno. Anybody?

 

[JimC]

I'd be concerned about burning a hole through the pistons.

 

[cubdrvr]

Rookie (dumb) question but how do you find out what model of 0-360 sump fits an 0-320 A2B narrow deck ? Thanks for all the good info you always share here.

I've seen an O-320 sump fit an O-360.

 

[Paul Heinrich]

I'd be concerned about burning a hole through the pistons.

Where? How so? Wouldn't the extra oxygen allow the fuel to burn more completely and efficiently? You wouldn't be packing more air into the cylinder; just improving the air quality going in. Wouldn't that be analogous to using higher octane fuel?

What's the risk if all you'd be doing is increasing the amount of oxygen going through the carburetor to maintain a fuel/air mixture that approximates the amount of oxygen available at sea level.

Like I said - I don't know; I'm just spitballing.

 

[JimC]

"Wouldn't the extra oxygen allow the fuel to burn more completely and efficiently?"

Yes. And the aluminum too.