Q: What’s the reason the O-320 E series can’t be converted to a higher compression?
A: It’s been a long time since I’ve had this question come up, but the answer is easy and may not be to your liking.
The following O-320-E series Lycoming engines may not be converted to high compression because these engines are built using “thin wall” main bearings: O-320-E2D, E2G, E2H, E3D, and E3H.
Other than those, some models may be converted to a higher compression, however there are some caveats.
Of course the pistons, piston pins, piston rings, and exhaust valves must be changed, but most low compression engines have plain steel cylinder barrels and the high compression engines must have either nitride or porous chrome barrels.
This begs the question: Even if you had a model that was acceptable to convert, would the expense be worth the cost just to gain 10 horsepower?
One suggestion I might mention is that if your engine is high time, but all operating parameters are still within specs, possibly just completing a top overhaul would provide you with some additional horsepower you’re looking for.
I have Seen only Certain AirCraft Engine that are able to do this with! The Lycoming 0-320 series comes either at 7.5:1 or 9.0:1.why would any one Need more the 9:1(180lbs.) of Compression in the Aire? Switch to Fuel Injection and Better Tuning in the Exhaust will increase Torque & H.P. significantly 30 hp. & 50+ lbs.of Torque. And an increase in throttle-response Noticeably by 30%.so don’t mess with the ibside, just the Out!
Drag reduction indeed will yield the highest gains in airspeed and roc. However there is a limited number of things that can be legally done to certified aircraft. Those items allowed will yield little speed gains.
Adding flap gap seals and wheel pants will help, but few aircraft have any stcs for any drag reduction.
The engine HP can be boosted with stc’d tuned exhaust systems and electronic ignition to get better ROC.
These will also allow more mixture leaning for a lower fuel burn.
$5,000 spent on drag reduction will let you go a lot faster than $5,000 spent on adding ten horsepower. There’s a formula for this, it is something like the speed increase will be one third of the percentage of the hp increase. 10 hp additional on a 150 hp engine is a fat 6%, so for $5,000, you get to go two miles an hour faster. What a bargain!
Clean up the airframe first. Make sure the doors fit properly (gear doors, too, if applicable), access doors, fairings and fillets, too, remove any unused antennas, make sure the airplane is rigged correctly, take out all the “stuff” that you don’t need to drag along, heck just washing and waxing the darn thing will give you two miles an hour.
Make sure your engine baffles are in good shape, cooling drag is something like 30% of the total drag on the airplane.
Jim Bede did some interesting work on drag reduction, it is on the internet but you have to dig around for it. There’s also a book by Kent Paser “Speed with Economy” which shows how he increased the top speed of his Mustang II from 175 mph to 239 mph, ROC from 1,200 FPM to 2,000 FPM and service ceiling from 17,000 feet to 25,000 feet PRIMARILY THROUGH DRAG REDUCTION, not by adding huge gobs of expensive horsepower. We can’t do a lot of this on certificated airplanes, but we can do some of it.
The formula is: Power required = drag (in pounds) times speed in MPH, divide by 375. A 25% reduction in drag, which is likely quite achievable for $5,000, nets a 24% increase in speed.
Still want to throw money at the engine?
Best Regards,
M/M