I don't know if I found out what was going on but I sure acquired a lot of info and a lot of theories. I am now in the process of changing over to fuel injection and will give a complete report when I get that done. The comparison should be interesting.
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Carb Heat for better fuel atomization?
- Thread starter bubb2
- Start date
I don't know if I found out what was going on but I sure acquired a lot of info and a lot of theories. I am now in the process of changing over to fuel injection and will give a complete report when I get that done. The comparison should be interesting.
I am interested in hearing more about the conversion. Which STC, and what are your primary reasons for undertaking the conversion?
John
Jim,
Thanks for the response, I know what your saying about egt but there are differing opinions out there. I installed the egt probes myself and tried to ensure they were all exactly the same distance from the exhaust port, but as you point out the curve of the pipes resulted in some variance between probes. I don't pretend to be an expert on this but someone who does disagrees about egt being meaningless. That would be G.A.M.I Injectors. They insist that if your probes are accurate (I get that if is a big word) and you use their tuned injectors, with a little minor adjusting you can get your egt's (fuel/air) variation down to less than 40 degrees. But their interesting point is once you get the engine running close enough on egt you will be able to safely lean the engine lean of peak egt. They say if you try that with a 125 degree difference (standard for a carb engine) the engine will start to run rough due to the variance in air/fuel mixture of the cylinders (results in significant power differences between your cylinders causing engine roughness). When the cylinders are tuned to burn the same air/fuel mixture you can lean well lean of peak with no adverse effect to the engine (and no engine roughness) as all cylinders will peak at almost the same exact time. Not sure how much of this I buy but their web site has some video of engine operations that are pretty convincing. They also seem to have a legion of pilots who swear to their claims. As I needed to buy a set of injectors for my conversion to fuel injection I bought a set of G.A.M.I.s. With the carb I couldn't lean the engine past the first cylinder hitting peak egt with noticeable roughness. To run lean of peak egt you lean until the last cylinder peaks. If I tried that with the carb I think the engine would shake so bad it would come out of the mount. Time will tell. More to come.
Thanks for the response, I know what your saying about egt but there are differing opinions out there. I installed the egt probes myself and tried to ensure they were all exactly the same distance from the exhaust port, but as you point out the curve of the pipes resulted in some variance between probes. I don't pretend to be an expert on this but someone who does disagrees about egt being meaningless. That would be G.A.M.I Injectors. They insist that if your probes are accurate (I get that if is a big word) and you use their tuned injectors, with a little minor adjusting you can get your egt's (fuel/air) variation down to less than 40 degrees. But their interesting point is once you get the engine running close enough on egt you will be able to safely lean the engine lean of peak egt. They say if you try that with a 125 degree difference (standard for a carb engine) the engine will start to run rough due to the variance in air/fuel mixture of the cylinders (results in significant power differences between your cylinders causing engine roughness). When the cylinders are tuned to burn the same air/fuel mixture you can lean well lean of peak with no adverse effect to the engine (and no engine roughness) as all cylinders will peak at almost the same exact time. Not sure how much of this I buy but their web site has some video of engine operations that are pretty convincing. They also seem to have a legion of pilots who swear to their claims. As I needed to buy a set of injectors for my conversion to fuel injection I bought a set of G.A.M.I.s. With the carb I couldn't lean the engine past the first cylinder hitting peak egt with noticeable roughness. To run lean of peak egt you lean until the last cylinder peaks. If I tried that with the carb I think the engine would shake so bad it would come out of the mount. Time will tell. More to come.
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I am interested in hearing more about the conversion. Which STC, and what are your primary reasons for undertaking the conversion?
John
JohnnyR,
For whatever reason, or probably multiple reasons, the O-470-50 engine does not seem to run that well with a carburetor. Several owners validated they had similar issues with their carbureted big bore Continentals. I've commented on a couple other threads on this site. Search "fuel injection" "O-470-50" as there is considerable info on the STC. It's basically an old, unsupported STC developed by Bendix in the 1960's for installation on Continental O-470's in 180's and 182's. They also had one for Bonanza's. The STC was a kit and most of the components are obsolete or superseded. You can still get a field approval using the STC as reference data.
JohnnyR,
For whatever reason, or probably multiple reasons, the O-470-50 engine does not seem to run that well with a carburetor. Several owners validated they had similar issues with their carbureted big bore Continentals. I've commented on a couple other threads on this site. Search "fuel injection" "O-470-50" as there is considerable info on the STC. It's basically an old, unsupported STC developed by Bendix in the 1960's for installation on Continental O-470's in 180's and 182's. They also had one for Bonanza's. The STC was a kit and most of the components are obsolete or superseded. You can still get a field approval using the STC as reference data.
Gotcha.
Two questions:
Who built up your PPonk?
Have you tried sending the carb out to Ly-Con or another PPonk-approved shop to overhaul the carb?
Not trying to dissuade you from your path. I'd pretty much decided to do a PPonk for our 180 this upcoming winter, and I'm interested in hearing about what brought you to this point.
Thanks,
John
Gotcha.
Two questions:
Who built up your PPonk?
Have you tried sending the carb out to Ly-Con or another PPonk-approved shop to overhaul the carb?
Not trying to dissuade you from your path. I'd pretty much decided to do a PPonk for our 180 this upcoming winter, and I'm interested in hearing about what brought you to this point.
Thanks,
John
Great questions. Answers are two of the primary "theories" as to why this engine does not run well carbureted. This engine is literally a IO-520-D that has had the fuel injection removed and a p.ponk modified carburetor installed. So this engine, unlike the standard p.ponk, has the higher compression pistons in it (field approval). I'm not sure if the higher compression pistons contribute to the problem but that has been suggested as one possibility. The carb was recently overhauled prior to Ly-con becoming the official overhauler for p.ponk. I spoke with Ly-con and they mentioned they have disassemble several carbs overhauled by this other facility and noted the other facility was using some un-approved parts resulting in poor running carbs. The thing is I have communicated with a couple of different owners of carbureted p.ponks who had very similar issues, very high fuel flow to keep the rear cylinders from running too lean of peak egt and wide egt differentials (although I did not learn of the Ly-con discovery at that time so I didn't ask who overhauld/modified their carbs). The really puzzling thing with this engine is that with partial carb heat (40 degrees) you could then lean the engine to a very reasonable fuel flow and the egt differential were as good as fuel injection. Now keep in mind the engine did not run rough or bad, it was only after I installed an EDM-900 that I discovered the rear cylinders weren't getting enough gas at the expected fuel flow and that it would run perfect with partial carb heat. I did eat up a couple cylinders until I installed the EDM-900. I recommend anyone who runs a big bore Continental, carbureted or injected, to check out G.A.M.I. injectors web site and see what they discovered on why the Continentals run lean on those back cylinders and rich on the front. Also check out Pelican Perch on the article about 0-470's which the author describes as having the worst induction system of any certificated engine.
I just had a lengthy discussion with a master engine guy who gave the following regarding similar issues in a regular 470. His responses can be summarized as:
"Sounds like an induction issue. Check for proper size crossover tube, and for cracks in the induction system."
Both of your recommended readings are excellent, by the way.
I can also recommend "Fly the Engine," found on Amazon.
J
EDIT: I apologize - just went back and read your earlier posts from March and it looks like you were tracking the proper stuff. Can't help but think it's something relatively simple that hasn't yet been found. Armchair quarterbacking, I know!
Good luck with the project. I'm sure others are like me and will be interested in hearing how it goes.
J
"Sounds like an induction issue. Check for proper size crossover tube, and for cracks in the induction system."
Both of your recommended readings are excellent, by the way.
I can also recommend "Fly the Engine," found on Amazon.
J
EDIT: I apologize - just went back and read your earlier posts from March and it looks like you were tracking the proper stuff. Can't help but think it's something relatively simple that hasn't yet been found. Armchair quarterbacking, I know!
Good luck with the project. I'm sure others are like me and will be interested in hearing how it goes.
J
Great questions. Answers are two of the primary "theories" as to why this engine does not run well carbureted. This engine is literally a IO-520-D that has had the fuel injection removed and a p.ponk modified carburetor installed. So this engine, unlike the standard p.ponk, has the higher compression pistons in it (field approval). I'm not sure if the higher compression pistons contribute to the problem but that has been suggested as one possibility. The carb was recently overhauled prior to Ly-con becoming the official overhauler for p.ponk. I spoke with Ly-con and they mentioned they have disassemble several carbs overhauled by this other facility and noted the other facility was using some un-approved parts resulting in poor running carbs. The thing is I have communicated with a couple of different owners of carbureted p.ponks who had very similar issues, very high fuel flow to keep the rear cylinders from running too lean of peak egt and wide egt differentials (although I did not learn of the Ly-con discovery at that time so I didn't ask who overhauld/modified their carbs). The really puzzling thing with this engine is that with partial carb heat (40 degrees) you could then lean the engine to a very reasonable fuel flow and the egt differential were as good as fuel injection. Now keep in mind the engine did not run rough or bad, it was only after I installed an EDM-900 that I discovered the rear cylinders weren't getting enough gas at the expected fuel flow and that it would run perfect with partial carb heat. I did eat up a couple cylinders until I installed the EDM-900. I recommend anyone who runs a big bore Continental, carbureted or injected, to check out G.A.M.I. injectors web site and see what they discovered on why the Continentals run lean on those back cylinders and rich on the front. Also check out Pelican Perch on the article about 0-470's which the author describes as having the worst induction system of any certificated engine.
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Mine runs like a top! Seriously, about as good as it can get. It took a little carb work, but nothing major.
bubb2, what year is your plane? What model 470 did you begin with?
1954.Engine was a IO-520-D. What kind of carb work? One opinion I got was the Texas Skyway carb works better. No idea what, if any difference between the two. Also, do you have a six cylinder engine monitor and if so what do you see for egt differential?
In my experience Continental reman carbs run too lean and so do Pponk’s modded carbs. But we finally got mine right, thanks to a friend. Get the carb right? Magic.
Mine is a ‘75 model with big exhaust.
EGTs? No idea. Never cared. CHTs are level and happy around 375-380.
Your woes don’t sound like the carb is the problem. I get why you want FI and no doubt it’ll help, but I’m still curious about your temp spreads and what’s causing it. There are lots of happy Pponk owners around. Your engine is unusual.
Mine is a ‘75 model with big exhaust.
EGTs? No idea. Never cared. CHTs are level and happy around 375-380.
Your woes don’t sound like the carb is the problem. I get why you want FI and no doubt it’ll help, but I’m still curious about your temp spreads and what’s causing it. There are lots of happy Pponk owners around. Your engine is unusual.
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I was under the impression that lean condition/under-jetting was earlier on, and that the handful of approved carb shops building for PPonk conversions are now onboard for proper jetting. No?
In my experience Continental reman carbs run too lean and so do Pponk’s modded carbs. But we finally got mine right, thanks to a friend. Get the carb right? Magic.
Mine is a ‘75 model with big exhaust.
EGTs? No idea. Never cared. CHTs are level and happy around 375-380.
Your woes don’t sound like the carb is the problem. I get why you want FI and no doubt it’ll help, but I’m still curious about your temp spreads and what’s causing it. There are lots of happy Pponk owners around. Your engine is unusual.
Not in my experience. All I ever wanted was to have 200* of leaning authority on a typical Alaskan summer day. That would assure I have adequate fuel flow for a cold winter day. I’ve had that carb worked on several times through the years and always came up short until the last time.
Other than jetting the best thing I’ve done for my Pponk was to swap out the decent shape stock exhaust for a new Acorn system. The resulting drop in CHTs was similar to what I saw when changing to a Hot Rod muffler on the -12.
I’ve mentioned it before but once I had an itty bitty leak in my induction at the Y pipe. I chased weird temps and MPs for weeks. A local carb guru listened to my story and told me I had an induction leak at the Y. I looked. No leak. The problem persisted. I looked again. No leak. One day a lean start backfire caused an engine fire and that required the carb and airbox to get rebuilt. After that MCS Mike insisted that I CAREFULLY inspect the rubbers at the Y pipe. I found the leak. Since then I inspect the rubbers and tighten the clamps every time I have the lower cowl off. I pay special attention to the Y pipe, which is not easy, just necessary.
Other than jetting the best thing I’ve done for my Pponk was to swap out the decent shape stock exhaust for a new Acorn system. The resulting drop in CHTs was similar to what I saw when changing to a Hot Rod muffler on the -12.
I’ve mentioned it before but once I had an itty bitty leak in my induction at the Y pipe. I chased weird temps and MPs for weeks. A local carb guru listened to my story and told me I had an induction leak at the Y. I looked. No leak. The problem persisted. I looked again. No leak. One day a lean start backfire caused an engine fire and that required the carb and airbox to get rebuilt. After that MCS Mike insisted that I CAREFULLY inspect the rubbers at the Y pipe. I found the leak. Since then I inspect the rubbers and tighten the clamps every time I have the lower cowl off. I pay special attention to the Y pipe, which is not easy, just necessary.
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Thanks, Stewart. If you don’t mind, I’ll get in touch with you for jetting specs prior to ordering from Ly-Con. I intend to discuss carb jetting with them to prep for cold winter flying. Not as bad as in AK, but we regularly see temps of -20 in Jan/Feb.
Not in my experience. All I ever wanted was to have 200* of leaning authority on a typical Alaskan summer day. That would assure I have adequate fuel flow for a cold winter day. I’ve had that carb worked on several times through the years and always came up short until the last time.
Other than jetting the best thing I’ve done for my Pponk was to swap out the decent shape stock exhaust for a new Acorn system. The resulting drop in CHTs was similar to what I saw when changing to a Hot Rod muffler on the -12.
Not in my experience. All I ever wanted was to have 200* of leaning authority on a typical Alaskan summer day. That would assure I have adequate fuel flow for a cold winter day. I’ve had that carb worked on several times through the years and always came up short until the last time.
Other than jetting the best thing I’ve done for my Pponk was to swap out the decent shape stock exhaust for a new Acorn system. The resulting drop in CHTs was similar to what I saw when changing to a Hot Rod muffler on the -12.
I’ve mentioned it before but once I had an itty bitty leak in my induction at the Y pipe. I chased weird temps and MPs for weeks. A local carb guru listened to my story and told me I had an induction leak at the Y. I looked. No leak. The problem persisted. I looked again. No leak. One day a lean start backfire caused an engine fire and that required the carb and airbox to get rebuilt. After that MCS Mike insisted that I CAREFULLY inspect the rubbers at the Y pipe. I found the leak. Since then I inspect the rubbers and tighten the clamps every time I have the lower cowl off. I pay special attention to the Y pipe, which is not easy, just necessary.
What are you seeing for fuel flow, at cruise (I run 2400/23), with your jetted carb to get that 200 degrees rich. I'm pumping about 17.5 gph into the engine at my cruise power setting and only have about 40 degrees rich of peak egt on the rear cylinders.
In level, full rich, 24-2400 cruise my fuel flow is around 18. I lean to 16 initially and then adjust down to the mid-15s as conditions warrant. I could go lower but CHTs start rising and I was taught that fuel is cheaper than cylinders.
Any problems with fouling plugs at that richness? How far rich of peak is 15 gpm for you? I recognize what you said about egt’s, but it’s helpful to have a baseline from which to work.
Also, Stewart, please refresh my memory on your bird - you have cowl louvers in addition to cowl flaps, correct?
Louvers recommended for the PPonk, regardless of effective baffling?
Thanks for your thoughts,
Johnny
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Johnny, Pponk owners are usually concerned with two things. Adequate fuel flow for full throttle take-off and climb, and nicely level CHTs during normal operations. When I bought a factory reman the carb was scary lean. Continental's rep had me take it to a shop where they reamed the jet. it was marginally better but not good. About that time I upgraded to the Pponk and had the carb mod done by Steve Knopp. It was a little stingy and I had a local shop open it up a little. Then after my engine fire that local shop opened it up a little more while overhauling it. It still didn't flow enough fuel for full power ops so it need a little more adjusting. Now I have 20-21-22 gph at take-off, which some here will say is too low (it isn't too low for my engine) and I have better than the 200* leaning authority. How rich of peak am I at 15.5? No idea. I still go by the pull the mixture til it stumble and then push it back in 3/4". If I do that? I come right to about 15.5 gph and my temps are very even. If you don't have adequate fuel flow for take-off the CHTs get hot early and they stay hot. With adequate fuel the CHTs don't get hot and keeping them in my comfort zone has been pretty easy. That's my perception of it, anyway.
Yes, I added cowl louvers and got 10-15* reduction in CHTs for closed cowl flap ops. Most of the guys I know with PPonk and TS engines have added cowl louvers. Required? No. A good idea? Probably, it can't hurt. The down side is oil temps drop more than CHTs but a strip of tape fixes that.
Yes, I added cowl louvers and got 10-15* reduction in CHTs for closed cowl flap ops. Most of the guys I know with PPonk and TS engines have added cowl louvers. Required? No. A good idea? Probably, it can't hurt. The down side is oil temps drop more than CHTs but a strip of tape fixes that.
I'm consistently seeing 23.9 GPH for takeoff flow with my 470R at 2650 RPM on a two-blade MT prop. That's derived from the downloaded spreadsheet data, and is measured with a JPI fuel flow meter that has proven to be accurate within tenths of a gallon over hundreds of gallons tracked by refilling (hand calc'd confirmation of flow).
What that means in comparison of WOT fuel flow to your engine's, I don't know... seems like yours is running the way you want it to, whether lean or not.
It does seem that having a fuel flow meter on these birds is a handy device to have during testing of a new engine install.
J
What that means in comparison of WOT fuel flow to your engine's, I don't know... seems like yours is running the way you want it to, whether lean or not.
It does seem that having a fuel flow meter on these birds is a handy device to have during testing of a new engine install.
J
Johnny, Pponk owners are usually concerned with two things. Adequate fuel flow for full throttle take-off and climb, and nicely level CHTs during normal operations. When I bought a factory reman the carb was scary lean. Continental's rep had me take it to a shop where they reamed the jet. it was marginally better but not good. About that time I upgraded to the Pponk and had the carb mod done by Steve Knopp. It was a little stingy and I had a local shop open it up a little. Then after my engine fire that local shop opened it up a little more while overhauling it. It still didn't flow enough fuel for full power ops so it need a little more adjusting. Now I have 20-21-22 gph at take-off, which some here will say is too low (it isn't too low for my engine) and I have better than the 200* leaning authority. How rich of peak am I at 15.5? No idea. I still go by the pull the mixture til it stumble and then push it back in 3/4". If I do that? I come right to about 15.5 gph and my temps are very even. If you don't have adequate fuel flow for take-off the CHTs get hot early and they stay hot. With adequate fuel the CHTs don't get hot and keeping them in my comfort zone has been pretty easy. That's my perception of it, anyway.
Yes, I added cowl louvers and got 10-15* reduction in CHTs for closed cowl flap ops. Most of the guys I know with PPonk and TS engines have added cowl louvers. Required? No. A good idea? Probably, it can't hurt. The down side is oil temps drop more than CHTs but a strip of tape fixes that.
Another little item I learned on my information crusade on carbureted big bore Continentals. The gasket between the airbox and the carburetor is currently priced by Cessna at about $75.00. Most o-470's and probably o-470-50 owners/mechanics elect to use the FAA/PMAd equivalent which costs a couple bucks. The main difference (besides the price) is the Cessna gasket has a square hole in the center that matches the inlet of the carb. The FAA/PMAd gasket has a round hole. I'm not an engineer but I can't imagine placing a partial restriction to the inlet of your carb would enhance it's performance. Never did any testing of this as I just recently discovered it. I know I've been running around for 30 plus years with a round hole in front of a square peg. Another little tid-bit of info, the 180 Parts Manual does not even show a gasket between the airbox and the carb on the early 180's. Not sure if that's a misprint or was how they were manufactured.
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Bubb2,
I was musing about your quandary and thinking about the ignition system. Poor performing spark plugs can raise egt’s, as in when one plug isn’t firing properly. I think Gary/BC12D mentioned this earlier. Did you rule that out for each suspect cylinder? My apologies if this is redundant.
J
I was musing about your quandary and thinking about the ignition system. Poor performing spark plugs can raise egt’s, as in when one plug isn’t firing properly. I think Gary/BC12D mentioned this earlier. Did you rule that out for each suspect cylinder? My apologies if this is redundant.
J
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When I overhauled the engine I also installed the EDM-900, so from the very beginning I was using brand new plugs. Now obviously brand new plugs don't mean you can't have a bad one but I think the fact that if I implement partial carb heat to 40 degrees and the engine runs perfect (I can now lean to 125 rich of peak on the rear cylinders at a ff of about 15gph and an egt differential of 40-75) would indicate it's not the ignition, its the carb. I also rotated the plugs a couple times since overhaul, no change.Bubb2,
I was musing about your quandary and thinking about the ignition system. Poor performing spark plugs can raise egt’s, as in when one plug isn’t firing properly. I think Dave Caulkins mentioned this earlier. Did you rule that out for each suspect cylinder? My apologies if this is redundant.
J
Have you done a mag check during cruise? Just curious, because it can reveal health of both plugs and mags and is a good eval exercise - testing at “load.”
When I overhauled the engine I also installed the EDM-900, so from the very beginning I was using brand new plugs. Now obviously brand new plugs don't mean you can't have a bad one but I think the fact that if I implement partial carb heat to 40 degrees and the engine runs perfect (I can now lean to 125 rich of peak on the rear cylinders at a ff of about 15gph and an egt differential of 40-75) would indicate it's not the ignition, its the carb. I also rotated the plugs a couple times since overhaul, no change.
Have you done a mag check during cruise? Just curious, because it can reveal health of both plugs and mags and is a good eval exercise - testing at “load.”
I don't remember checking the mags at cruise. I may have, just don't remember. Both mags and harness were all replaced with new at the overhaul. Mags check good at runup. Kinda too late now, the carbs off, the fuel injection is pretty much installed. Got a couple other things going on; radio change, annual inspection, etc. I also just submitted an amendment to the field approval based on fuel pressure limitation changes.
Welp, good luck with the upgrades. Perhaps I’ll get to see it this summer when I’m up in your neck of the woods. Regardless, looking forward to an after action report!
J
J
I don't remember checking the mags at cruise. I may have, just don't remember. Both mags and harness were all replaced with new at the overhaul. Mags check good at runup. Kinda too late now, the carbs off, the fuel injection is pretty much installed. Got a couple other things going on; radio change, annual inspection, etc. I also just submitted an amendment to the field approval based on fuel pressure limitation changes.
Welp, good luck with the upgrades. Perhaps I’ll get to see it this summer when I’m up in your neck of the woods. Regardless, looking forward to an after action report!
J
You flying that 180 Up here?
That’s the plan. Some time in Talkeetna with Don, then out and about.You flying that 180 Up here?
How's the FI install going?
I don't remember checking the mags at cruise. I may have, just don't remember. Both mags and harness were all replaced with new at the overhaul. Mags check good at runup. Kinda too late now, the carbs off, the fuel injection is pretty much installed. Got a couple other things going on; radio change, annual inspection, etc. I also just submitted an amendment to the field approval based on fuel pressure limitation changes.
Hit a little snag with an amendment to the Flight Manual Supplement at the FAA shop. I think it's now working out. Presision Airmotive (owner of the RSA fuel injection system)recommends taking the fuel pressure reading from the inlet side of the injector which measures fuel pump pressure instead of at the flow divider. Trying to get that change approved so I can get the JPI EDM-900 configured for it. JPI will not change the unit without proof of FAA approval. While I wait I'm doing the radio install and have run into some antenna separation issues. This airplane isn't going anywhere till the water turns wet again.
To eskimo77 I would share the 337 but not until I check the system out. I installed this system a little different than the others 337's I have seen. The old STC data is contradictory and in places just wrong. I can provide copies of previous installations in other airplanes. These 337's list all the current components and reference documents but I don't think any of them have an updated and corrected Flight Manual Supplement. If your serious these 337's will tell you what components to acquire and what to use for basic data.
To eskimo77 I would share the 337 but not until I check the system out. I installed this system a little different than the others 337's I have seen. The old STC data is contradictory and in places just wrong. I can provide copies of previous installations in other airplanes. These 337's list all the current components and reference documents but I don't think any of them have an updated and corrected Flight Manual Supplement. If your serious these 337's will tell you what components to acquire and what to use for basic data.
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