Van's Air Force
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Intake manifold and cams
- Thread starter zav6a
- Start date
plenum
I'd like a bit more power and not interested in swapping engines. I enjoy tuning and optimizing and getting as much speed and economy out of it as I can. I've been playing around with fuel distribution and exhausts and believe that the weak point is the induction. And, I fly at high altitude nearly all of the time (summer DAs at takeoff typically over 8000 feet and I end up over 12k most flights).
Looking at the existing plumbing, circa 1957, can't help but believe their is a way to get more air, and more evenly distributed, in there. I would probably jump compression a notch too given I can seldom run much more than 75% and detonation margins are therefore wide.
In summary, a smooth running, economical, O-320 that is the HP equivalent of a O-360 at altitude.
I'd like a bit more power and not interested in swapping engines. I enjoy tuning and optimizing and getting as much speed and economy out of it as I can. I've been playing around with fuel distribution and exhausts and believe that the weak point is the induction. And, I fly at high altitude nearly all of the time (summer DAs at takeoff typically over 8000 feet and I end up over 12k most flights).
Looking at the existing plumbing, circa 1957, can't help but believe their is a way to get more air, and more evenly distributed, in there. I would probably jump compression a notch too given I can seldom run much more than 75% and detonation margins are therefore wide.
In summary, a smooth running, economical, O-320 that is the HP equivalent of a O-360 at altitude.
intakes and cams
Mr.zav6a
There certainly are"small" ways to help the 320, but you must first look closely at the beast. GA aircraft engine in comparison to the rest of the internal combustion engine world are poor examples of engine designs. This can be proven by their reliability records as well as the constant "reminders" AD notices, that come up on a regular basis.
Porting, flow paterns are somewhere between poor and mediocre. Most Briggs and Strattons found in lawn mowers are far more sopisticated. The fact that they spin so slow is a hindrence in producing power. Looking at a horsepower formula will tell you that HP is a result of engine speed. Increasing engine speeds has it's drawbacks not the least of which is reducing the efficiency of the "screw". In addition, look closely at a crankshaft, crancase and overall construction of GA engines, and even an untrained eye will tell you, it ain't gonna take too much more speed. Case in point, Lycomings used in helicopter applications, have reduced TBOs simply because they are required to spin faster that their conventional flying brothers. Exhaust designs are always a hot topic of discussion. In reality, they do not add or make power, unless other components are in harmony. They will only pin point power. Given the operational speed of our engines which is no more than 300 or so rpms, it would take a sophisticated dinomometer to design a pipe the will make all it's power at that speed, and even then it won't be much more, if any, than the engine already has.
Other factors include fixed ignition timing, fixed pitch props, and the worst carburator design of all time , the updraft carburator, which BTW, won't be found even in lawn mowers. One last feature, is the tolerance used in a typical GA engines.
A few days ago, I measured the bores of an O200 Conti. Piston to wall clearance was an acceptable .013. New tolerance for the O200 is .009 to .011. Maximum allowable is .019 to .020. By comaprison, a Briggs and Stratton lawnmower, has ,003, max .006. As you can see the AC engine will have constant blow by, as well as oil consumption. My Chrysler T&C as well as many other autos, has .0005 piston to wall clearance and max .002. Your O320 is a little wider than the little Conti, new .010 to .020 max.
Bottom line, we fly engines with technology out of the Jurassic age.
What can we do to improve them?
As with all engines, our dinosaurs notwhitstanding, holding those tolerances as close to new as possible is the first step. I've done this on my old Cherokee 140 (O320) as well as my old Arrow (IO360)
Piston to wall clearances held to new tolerances, as well as ring gaps, lifter bleed down clearance held at ,050 +- .005 for the 320, .060+- .005 for the 360. Ignition timing per specification , but just because the mags match on the timing marks doesn't mean it's woking. Point gap must be set to allow maximum coil saturation for the strongest spark possible. With the 140, it's maximum speed as published was 142 mph. it rarely would do much over 120. Airframe rigging help a bit to barely nudge 125. Prop pitch had been decreased, so I had increased back to specifications and increased it to the legal limit of 1 in. It's published top speed of 142 was finally realized. With the fixed pitch prop. altitude was always a limit but it did reach it much faster than before the changes. Climb was also improved by as much as 300 fpm over published specs, 800 fpm over 500 fpm.
On the Arrow (180) much the was done in addition to LASAR. Fuel injectors were properly flowed to specs. Before the Arrow rarely saw more than 128 to 132kts in cruise, after 140kt to 145kts in cruise (top speed 147 kt) Due to C/S prop and managed ignition timing. Climb was dramatically increased particularly at higher altituded 11K to 13K yielded more than 750fpm while at lower altitude avaraged 1100 fpm. Spcs 800 fpm from SL. In both cases, oil was 15/50, and mogas helped as well though the Arrow was not approved due to FI, however, though illegal, it did improve performance, when tried.
Could more have been done, probably so, but as stated, with poorly designed intake ans exhaust conduits, poor combustion chamber, overly heavy valve train, unbelivable sloppy engine tolerances, it would have taken insurmountable funds. In the end with the low engine speeds, I doubt that much more could be gained accecpt for a massive reduction in oil consumption (to none), and yes, reduction in oil consumption in itself would translate in HP increase, performance, and economy.
If you have the time and funds, even the dinosaur can be made to soar.
We are after all experimental, so give it a shot, but don't be too disappointed if what you're looking for evades you. At least the learning curve will be rewarding.
T88
RV10
Mr.zav6a
There certainly are"small" ways to help the 320, but you must first look closely at the beast. GA aircraft engine in comparison to the rest of the internal combustion engine world are poor examples of engine designs. This can be proven by their reliability records as well as the constant "reminders" AD notices, that come up on a regular basis.
Porting, flow paterns are somewhere between poor and mediocre. Most Briggs and Strattons found in lawn mowers are far more sopisticated. The fact that they spin so slow is a hindrence in producing power. Looking at a horsepower formula will tell you that HP is a result of engine speed. Increasing engine speeds has it's drawbacks not the least of which is reducing the efficiency of the "screw". In addition, look closely at a crankshaft, crancase and overall construction of GA engines, and even an untrained eye will tell you, it ain't gonna take too much more speed. Case in point, Lycomings used in helicopter applications, have reduced TBOs simply because they are required to spin faster that their conventional flying brothers. Exhaust designs are always a hot topic of discussion. In reality, they do not add or make power, unless other components are in harmony. They will only pin point power. Given the operational speed of our engines which is no more than 300 or so rpms, it would take a sophisticated dinomometer to design a pipe the will make all it's power at that speed, and even then it won't be much more, if any, than the engine already has.
Other factors include fixed ignition timing, fixed pitch props, and the worst carburator design of all time , the updraft carburator, which BTW, won't be found even in lawn mowers. One last feature, is the tolerance used in a typical GA engines.
A few days ago, I measured the bores of an O200 Conti. Piston to wall clearance was an acceptable .013. New tolerance for the O200 is .009 to .011. Maximum allowable is .019 to .020. By comaprison, a Briggs and Stratton lawnmower, has ,003, max .006. As you can see the AC engine will have constant blow by, as well as oil consumption. My Chrysler T&C as well as many other autos, has .0005 piston to wall clearance and max .002. Your O320 is a little wider than the little Conti, new .010 to .020 max.
Bottom line, we fly engines with technology out of the Jurassic age.
What can we do to improve them?
As with all engines, our dinosaurs notwhitstanding, holding those tolerances as close to new as possible is the first step. I've done this on my old Cherokee 140 (O320) as well as my old Arrow (IO360)
Piston to wall clearances held to new tolerances, as well as ring gaps, lifter bleed down clearance held at ,050 +- .005 for the 320, .060+- .005 for the 360. Ignition timing per specification , but just because the mags match on the timing marks doesn't mean it's woking. Point gap must be set to allow maximum coil saturation for the strongest spark possible. With the 140, it's maximum speed as published was 142 mph. it rarely would do much over 120. Airframe rigging help a bit to barely nudge 125. Prop pitch had been decreased, so I had increased back to specifications and increased it to the legal limit of 1 in. It's published top speed of 142 was finally realized. With the fixed pitch prop. altitude was always a limit but it did reach it much faster than before the changes. Climb was also improved by as much as 300 fpm over published specs, 800 fpm over 500 fpm.
On the Arrow (180) much the was done in addition to LASAR. Fuel injectors were properly flowed to specs. Before the Arrow rarely saw more than 128 to 132kts in cruise, after 140kt to 145kts in cruise (top speed 147 kt) Due to C/S prop and managed ignition timing. Climb was dramatically increased particularly at higher altituded 11K to 13K yielded more than 750fpm while at lower altitude avaraged 1100 fpm. Spcs 800 fpm from SL. In both cases, oil was 15/50, and mogas helped as well though the Arrow was not approved due to FI, however, though illegal, it did improve performance, when tried.
Could more have been done, probably so, but as stated, with poorly designed intake ans exhaust conduits, poor combustion chamber, overly heavy valve train, unbelivable sloppy engine tolerances, it would have taken insurmountable funds. In the end with the low engine speeds, I doubt that much more could be gained accecpt for a massive reduction in oil consumption (to none), and yes, reduction in oil consumption in itself would translate in HP increase, performance, and economy.
If you have the time and funds, even the dinosaur can be made to soar.
We are after all experimental, so give it a shot, but don't be too disappointed if what you're looking for evades you. At least the learning curve will be rewarding.
T88
RV10
gmcjetpilot
Well Known Member
Cool plenum
The idea of the cold induction is more air density due to less oil heating. I don't think that change (increase air density with cooler air) changes cam timing.
I am not sure how much the intake will neccesitate the NEED for a cam change, but with the 4 into 1 exhaust a cam change would take advantage of more scavaging it provides with cam timing changes. Read the Cafe Foundation Exhaust reports and get a hold of Lycon about custom cam work.
There was a used cold plenum for sale for a 360. I think this guy had it on his site: I believe it was a
http://www.attawayair.com/index.html
Sky Dynamics also makes a cold sump:
http://www.skydynamics.com/homepage.html
None of this is for the 320, but it may give you some ideas. I also concure with the above, unless you know what you are doing and are prepared to take the extra risk and likely cost of major engine work, very short TBO, than go for it. I just have a hard time taking a strung out Lycoming out for a plane ride with the girlfriend, friend or kid. Just my opinion. You can add anything you want, but complete engine failure, broken rods, cranks, burnt pistons/valves and so on, are all possible results of custom engine work. George
The idea of the cold induction is more air density due to less oil heating. I don't think that change (increase air density with cooler air) changes cam timing.
I am not sure how much the intake will neccesitate the NEED for a cam change, but with the 4 into 1 exhaust a cam change would take advantage of more scavaging it provides with cam timing changes. Read the Cafe Foundation Exhaust reports and get a hold of Lycon about custom cam work.
There was a used cold plenum for sale for a 360. I think this guy had it on his site: I believe it was a
http://www.attawayair.com/index.html
Sky Dynamics also makes a cold sump:
http://www.skydynamics.com/homepage.html
None of this is for the 320, but it may give you some ideas. I also concure with the above, unless you know what you are doing and are prepared to take the extra risk and likely cost of major engine work, very short TBO, than go for it. I just have a hard time taking a strung out Lycoming out for a plane ride with the girlfriend, friend or kid. Just my opinion. You can add anything you want, but complete engine failure, broken rods, cranks, burnt pistons/valves and so on, are all possible results of custom engine work. George
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intake
I perhaps made it sound like I am a horsepower nut. What I am really after is just to see the equivelent of 65 or 75 percent more of the time. Because of the altitude and fixed prop, my engine has never seen in excess of 75 percent in the last 700 hours, and most of it closer to 55-65% (even though it is firewalled 90 percent of the time)! I just want some of the power that sea level folks enjoy every day! If I get 10 percent more out of the engine, between fuel injection, electronic ignition, slightly higher compression and improved intake and exhaust, which is probably a stretch if I stay under 2700 rpm, I will still be putting less stress on the engine than if I operated at sea level! If I can better cyl to cyl balance out of it too, that would be a bonus.
My equivelent of turbonormalizing (to maybe 5000 feet) without the turbo.
Thanks for the Lycon lead. I see their name often but did not realize they did performance work too.
By the way, I put in the starting circuit to prevent backfire associated with Jeff Rose ignition (that you recommended months ago) and now the prop always goes the right way!
I perhaps made it sound like I am a horsepower nut. What I am really after is just to see the equivelent of 65 or 75 percent more of the time. Because of the altitude and fixed prop, my engine has never seen in excess of 75 percent in the last 700 hours, and most of it closer to 55-65% (even though it is firewalled 90 percent of the time)! I just want some of the power that sea level folks enjoy every day! If I get 10 percent more out of the engine, between fuel injection, electronic ignition, slightly higher compression and improved intake and exhaust, which is probably a stretch if I stay under 2700 rpm, I will still be putting less stress on the engine than if I operated at sea level! If I can better cyl to cyl balance out of it too, that would be a bonus.
My equivelent of turbonormalizing (to maybe 5000 feet) without the turbo.
Thanks for the Lycon lead. I see their name often but did not realize they did performance work too.
By the way, I put in the starting circuit to prevent backfire associated with Jeff Rose ignition (that you recommended months ago) and now the prop always goes the right way!
