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Poor mixture authority

00Dan

Well Known Member
I’m running an O-320-A3A with an MA-4SPA 10-3678-32 carb. The engine runs smooth (except below 750 rpm; I attribute that to the wood prop). I can’t help but feel I am running lean due to the mixture control having very little travel before an RPM drop is observed. I did validate the mixture control is actuating the lever to both stops.

On the ground at approximately 1200 RPM I did not observe any RPM rise before a drop. In the air at 8500’ and WOT I observed approximately 50-70 dF EGT rise on the three cylinders for which I’m instrumented; I can’t say if this is peak or not, merely that’s when RPM visibly dropped off. RPM rise is either not there or imperceptible on my tach. The one CHT probe I have is on #4 and sees up to 370-380 during a long 100 MPH climb and around 300-320 during cruise.
I’m not instrumented for fuel flow. These temperatures at with ambient temperatures about 55-60 on the ground.

I will be installing a JPI soon so I’ll have an idea of what all four cylinders are doing plus have fuel flow information before making any changes. The lack of mixture authority is what got my attention though. I saw the posts here about RVs running lean and did some research, including calling MSA. They said the 3678-12 is the richer carb for my engine compared to the -32 I have installed. Yet, I saw posts here from the past year from others who called them and were told the opposite.

My theory is that this is one of two things - either my carb is running lean or I have one cylinder running very lean and causing an RPM drop off while the others are still rich.

Any thoughts or other avenues to explore here?
 
From idle, when you move the mixture to ICO, what rpm rise do you get? You stated that you get none at 1200rpm, but how about at idle?
It does sound like maybe the jetting could use opening up. .I would expect more egt change from full rich to peak egt in cruise. .
 
From idle, when you move the mixture to ICO, what rpm rise do you get? You stated that you get none at 1200rpm, but how about at idle?
It does sound like maybe the jetting could use opening up. .I would expect more egt change from full rich to peak egt in cruise. .

I'll check the ICO rise next time I fly, but its not my primary concern since its easier to adjust than the jet.
 
I'll check the ICO rise next time I fly, but its not my primary concern since its easier to adjust than the jet.

It’s just another data point to check, and I figured that I would mention it since you couldn’t get a rise at 1200rpm.. that’s probably because you aren’t really on the idle circuit then. It does sound like your main jet may be a little lean, as I would expect more of a egt rise in cruise though. Have you read the posts about the “Mooney mod” on RV carbs?
 
It’s just another data point to check, and I figured that I would mention it since you couldn’t get a rise at 1200rpm.. that’s probably because you aren’t really on the idle circuit then. It does sound like your main jet may be a little lean, as I would expect more of a egt rise in cruise though. Have you read the posts about the “Mooney mod” on RV carbs?

I have indeed, but wasn’t sure if they were applicable since I have a 320 with a -4SPA rather than a 360 and a -4-5.
 
I’m running an O-320-A3A with an MA-4SPA 10-3678-32 carb. The engine runs smooth (except below 750 rpm; I attribute that to the wood prop). I can’t help but feel I am running lean due to the mixture control having very little travel before an RPM drop is observed. I did validate the mixture control is actuating the lever to both stops.

On the ground at approximately 1200 RPM I did not observe any RPM rise before a drop. In the air at 8500’ and WOT I observed approximately 50-70 dF EGT rise on the three cylinders for which I’m instrumented; I can’t say if this is peak or not, merely that’s when RPM visibly dropped off. RPM rise is either not there or imperceptible on my tach. The one CHT probe I have is on #4 and sees up to 370-380 during a long 100 MPH climb and around 300-320 during cruise.
I’m not instrumented for fuel flow. These temperatures at with ambient temperatures about 55-60 on the ground.

I will be installing a JPI soon so I’ll have an idea of what all four cylinders are doing plus have fuel flow information before making any changes. The lack of mixture authority is what got my attention though. I saw the posts here about RVs running lean and did some research, including calling MSA. They said the 3678-12 is the richer carb for my engine compared to the -32 I have installed. Yet, I saw posts here from the past year from others who called them and were told the opposite.

My theory is that this is one of two things - either my carb is running lean or I have one cylinder running very lean and causing an RPM drop off while the others are still rich.

Any thoughts or other avenues to explore here?

Does the engine get rough as your tach indicates the rpm loss? I would ignore the rpm loss and lean until you see peak on the first of the three instrumented cylinders to hit peak EGT. What is the Egt spread from full rich to peak on that cylinder? Does the engine get rough or start stumbling at this point? At idle, below 1000rpm, you want to see a rise in RPM, when leaned out to quitting, to see what the idle mixture is doing.... No rise too lean, 10-25 rise just right. At power, is is difficult to discern mixture using the TACH. It can be done but you need really accurate, sensitive instruments. The egt will give you way more accurate data. If the engine stumbles or gets rough way before you are leaned to peak on the instrumented cylinders that means the one that isn't instrumented is much leaner than the others. If the engine loses power evenly when you are going past peak then that means all of the cylinders are close to the same mixture. Ideally, you would want to have the engine lose power evenly without roughness, as you go through peak and at lower altitudes of say 3000 feet and under, you would want to see at least a 50-75 degree spread from full rich to peak on the first cylinder to peak. On a carbureted engine that is a bit difficult to attain. But if your engine gets rough or starts stumbling when the first cylinder hits peak then you know that cylinder is the leanest and as long as you have the 50-75 degree spread at lower altitudes, on that cylinder, the engine is rich enough and you are assured that the other cylinders are at least as rich as that one or richer.
Happy New Year!
Mahlon
 
Intake Leak?

Dan, did you do the usual first things in checking out a lean engine? I tangled with a newly installed O-290 some time ago that ran like that. Pilot gripe was high mag drops, and rough on either mag by itself. Weird, right? Long story short, after checking the mag timing, (it was fine) I ran it myself and noticed that a very short pull on the mixture made the engine quit. I had the carb apart looking for obstructions. Very ashamed to admit, after all that, (all that!) I noticed that all 4 primer holes in the heads were not plugged. Well, it's SoCal and it's not unusual to not have a primer system. Whoever built the engine apparently figured the installer would add a primer. So. A trip to the local hardware store for 4@ 1/8" NPT brass plugs and that engine was ALL better. I was surprised that it would run even that well or at all with such a huge intake leak. So, anyway, make sure the carb is tight on the oil sump, and check all around the gasket to see if there's a gap. Make sure the intake hoses are tight and sealing, and check the intake flanges at the heads. Those things can distort and leak if they're overtightened. If you see blue fuel stain by the flange(s) it's a dead giveaway. Once, I even ran across an engine where all four of the paper flange gaskets were missing altogether. You might pull the sparking plugs and see what color they are. If they're light grey or white on the business ends, something is definitely lean. I'd do all that easy, free stuff before rejetting the carb. Safe flying!
 
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Does the engine get rough as your tach indicates the rpm loss? I would ignore the rpm loss and lean until you see peak on the first of the three instrumented cylinders to hit peak EGT. What is the Egt spread from full rich to peak on that cylinder? Does the engine get rough or start stumbling at this point? At idle, below 1000rpm, you want to see a rise in RPM, when leaned out to quitting, to see what the idle mixture is doing.... No rise too lean, 10-25 rise just right. At power, is is difficult to discern mixture using the TACH. It can be done but you need really accurate, sensitive instruments. The egt will give you way more accurate data. If the engine stumbles or gets rough way before you are leaned to peak on the instrumented cylinders that means the one that isn't instrumented is much leaner than the others. If the engine loses power evenly when you are going past peak then that means all of the cylinders are close to the same mixture. Ideally, you would want to have the engine lose power evenly without roughness, as you go through peak and at lower altitudes of say 3000 feet and under, you would want to see at least a 50-75 degree spread from full rich to peak on the first cylinder to peak. On a carbureted engine that is a bit difficult to attain. But if your engine gets rough or starts stumbling when the first cylinder hits peak then you know that cylinder is the leanest and as long as you have the 50-75 degree spread at lower altitudes, on that cylinder, the engine is rich enough and you are assured that the other cylinders are at least as rich as that one or richer.
Happy New Year!
Mahlon

Mahlon, good points on the RPM drop. I'll admit I didn't particularly consider letting the engine go further lean. I'll try this.

Dan, did you do the usual first things in checking out a lean engine? I tangled with a newly installed O-290 some time ago that ran like that. Pilot gripe was high mag drops, and rough on either mag by itself. Weird, right? Long story short, after checking the mag timing, (it was fine) I ran it myself and noticed that a very short pull on the mixture made the engine quit. I had the carb apart looking for obstructions. Very ashamed to admit, after all that, (all that!) I noticed that all 4 primer holes in the heads were not plugged. Well, it's SoCal and it's not unusual to not have a primer system. Whoever built the engine apparently figured the installer would add a primer. So. A trip to the local hardware store for 4@ 1/8" NPT brass plugs and that engine was ALL better. I was surprised that it would run even that well or at all with such a huge intake leak. So, anyway, make sure the carb is tight on the oil sump, and check all around the gasket to see if there's a gap. Make sure the intake hoses are tight and sealing, and check the intake flanges at the heads. Those things can distort and leak if they're overtightened. If you see blue fuel stain by the flange(s) it's a dead giveaway. Once, I even ran across an engine where all four of the paper flange gaskets were missing altogether. You might pull the sparking plugs and see what color they are. If they're light grey or white on the business ends, something is definitely lean. I'd do all that easy, free stuff before rejetting the carb. Safe flying!

My ~1800 RPM runup mag drops are normal, with just less than 100 RPM smooth drop on each. At cruise power in the air mag drop is about the same, but with a slight roughness associated at that power level. I haven't done a formal intake leak search, but when the plane was in prebuy about 5 weeks ago the engine got a full visual inspection and a trained ear listening for leaks during the compression test. Plugs were pulled and nothing out of sort was noted at the time.

When I install the JPI next month I'll be giving everything a good visual inspection and it will be interesting to see if the different instrumentation sheds some light on it. I'm certainly avoiding any sort of exploratory surgery.
 
I did some testing today. At 20" MAP and approximately 2250 RPM at 2200', I got the following results by leaning until roughness (I didn't pay attention to RPM).

#1: 53 dF EGT rise
#3: 21 dF EGT rise
#4: 58 dF EGT rise

CHT on #4 was stable at approximately 310 dF the whole time.
I tested ICO rise at full idle, which is set to approximately 650 RPM right now. There may have been a small (~20 RPM) rise but it was hard to tell.



Thanks for the link.
 
I did some testing today. At 20" MAP and approximately 2250 RPM at 2200', I got the following results by leaning until roughness (I didn't pay attention to RPM).

#1: 53 dF EGT rise
#3: 21 dF EGT rise
#4: 58 dF EGT rise

CHT on #4 was stable at approximately 310 dF the whole time.
I tested ICO rise at full idle, which is set to approximately 650 RPM right now. There may have been a small (~20 RPM) rise but it was hard to tell.

Thanks for the link.


If you are only getting a 20-50* rise at 20" from full rich, you have some major issues going on. I would expect at least a 150-200* rise from full rich to peak EGT at 20" Maybe less at 28", but at 20" it should be very rich even at 2200 MSL with a carb.

Larry
 
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If you are only getting a 20-50* rise at 20" from full rich, you have some major issues going on. I would expect at least a 200* rise from full rich to peak EGT at 20" Maybe less at 28", but at 20" it should be very rich even at 2200 MSL with a carb.

Larry

Those numbers aren’t necessarily peak, rather it’s how far I got before the first cylinder to peak went lean enough that I could feel it. I’m not prepared to rule out one cylinder running particularly lean. Just my luck that it may be the one that I don’t have EGT hooked up on. One piece of potential supporting evidence for this is my #4 CHT - I suspect it would be running hotter if the entire engine was running very lean.
 
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Those numbers aren’t necessarily peak, rather it’s how far I got before the first cylinder to peak went lean enough that I could feel it. I’m not prepared to rule out one cylinder running particularly lean. Just my luck that it may be the one that I don’t have EGT hooked up on. One piece of potential supporting evidence for this is my #4 CHT - I suspect it would be running hotter if the entire engine was running very lean.

Hottest CHT will be at 80-100* ROP. They cool a bit as you lean to peak and then cool rapidly when leaner than that. CHTs also drop when richer than 80-100* ROP.
 
Hottest CHT will be at 80-100* ROP. They cool a bit as you lean to peak and then cool rapidly when leaner than that. CHTs also drop when richer than 80-100* ROP.

Correct, which leads me to believe at least #4 is running sufficient rich to keep it at that temperature.
 
To clarify some questions I’ve been asked, some additional details.

The engine runs smooth and starts easily. I did some testing with airspeed which the EGT does respond to, although it rises faster in a dive than it decreases in a descent (Test done at constant throttle).

As far as I’m aware it’s been running like this for years. The other cylinders without CHT probably haven’t cooked themselves as oil consumption is good (approximately 2-3 quarts per 50 hours).

Basically, it all comes down to the fact I can’t lean it out very far. The EGT readings I posted above sort of back this up. I hope to have a JPI installed within the next month and hopefully it will provide some additional diagnostic data before I start pulling things apart.
 
engine monitor

...
Basically, it all comes down to the fact I can’t lean it out very far. The EGT readings I posted above sort of back this up. I hope to have a JPI installed within the next month and hopefully it will provide some additional diagnostic data before I start pulling things apart.
I don't have any knowledge of the JPI but have you considered an engine monitor like the GRT EIS 4000 with a small EFIS? Very inexpensive, and will get lots of info. http://grtavionics.com/vaf.html
 
Nozzle PN

Resurrecting this thread because I have some new info.

I was going through the engine log the other day and I discovered the builder at one point swapped the nozzle in the carb. It originally had a 47-773 and he swapped it for a 47-828. What sort of difference would this be expected to make?
 
Resurrecting this thread because I have some new info.

I was going through the engine log the other day and I discovered the builder at one point swapped the nozzle in the carb. It originally had a 47-773 and he swapped it for a 47-828. What sort of difference would this be expected to make?

The nozzle is the main jet and it is the biggest contributor to how the carb matches fuel flow to air flow through the venturi. I can't say whether that swap was an increase or decrease in the jet size, but it likely moved the fuel flow rate, at full rich, up or down.

I recommend that you keep leaning, even if one cyl gets rough, to determine the EGT Delta from full rich to peak on the three cylinders. This will help pin point if you have a carb issue or an issue with the one cylinder that is lean. Recommend doing this at altitude (3-5K) and WOT to help eliminate intake leaks and becuase this is where you really want to know if the fuel flow is metering correctly.

Larry
 
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I finally got the chance to fly my plane fully instrumented. I only flew for a little bit today since it was getting dark but I noted fuel flow and RPM in a couple full throttle conditions. It was cool here today, only 45-50 F on the ground.

In the takeoff run and climb I saw approximately 10 GPH at 2150 RPM. In cruise at 7500, I saw about the same fuel flow at 2650 RPM. When leaning, the engine became rough at about 9.5 GPH.

I did install the SDS intake flanges to preempt any potential intake leaks, and that appears to give me normal leaning authority on the ground.

My uneducated perception here is that I’m simply in need of a rejet (assuming I choose to live with the airspeed induced leaning found in my model carb). Any advice before I bust out the drill?
 
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I finally got the chance to fly my plane fully instrumented. I only flew for a little bit today since it was getting dark but I noted fuel flow and RPM in a couple full throttle conditions. It was cool here today, only 45-50 F on the ground.

In the takeoff run and climb I saw approximately 10 GPH at 2150 RPM. In cruise at 7500, I saw about the same fuel flow at 2650 RPM. When leaning, the engine became rough at about 9.5 GPH.

I did install the SDS intake flanges to preempt any potential intake leaks, and that appears to give me normal leaning authority on the ground.

My uneducated perception here is that I’m simply in need of a rejet (assuming I choose to live with the airspeed induced leaning found in my model carb). Any advice before I bust out the drill?

9.5 GPH at 7500' is right around or a bit higher than max power (approx 75-100 ROP). I routinely run 8 GPH at 8000', which is around 20-40 LOP. Rejetting is not your answer, at least at cruise. You should remember that many carb'ed engine won't be happy LOP. If WOT, intake leaks have a small impact on mixture. Trying pulling back the throttle just a bit at cruise as well as adding carb heat to see if it helps to get leaner. Many seem to have some success with this. Have you checked your ignition timing and insured that each plug is firing?

Shortly after T/O, nose down and accelerate to 2500 RPM, still WOT. What is the fuel flow then? You're looking for around 13.5, give or take, at low altitudes. If you're getting that, no need to rejet.

Down low and WOT or max prop RPM, compare full rich EGT to peak EGT. If you are getting a delta of 200*, your jetting is fine. DO this quickly, as you want to avoid time at peak EGT under high power settings down low.
 
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9.5 GPH at 7500' is right around or a bit higher than max power (approx 75-100 ROP). I routinely run 8 GPH at 8000', which is around 20-40 LOP. Rejetting is not your answer, at least at cruise. You should remember that many carb'ed engine won't be happy LOP. If WOT, intake leaks have a small impact on mixture. Trying pulling back the throttle just a bit at cruise as well as adding carb heat to see if it helps to get leaner. Many seem to have some success with this. Have you checked your ignition timing and insured that each plug is firing?

Shortly after T/O, nose down and accelerate to 2500 RPM, still WOT. What is the fuel flow then? You're looking for around 13.5, give or take, at low altitudes. If you're getting that, no need to rejet.

Down low and WOT or max prop RPM, compare full rich EGT to peak EGT. If you are getting a delta of 200*, your jetting is fine.

Next time I fly I’ll redo the EGT test and I’ll try a higher RPM. I will say the other night as I was returning to the airport at 3000’ I set FT and full rich. With that I saw about 11 GPH at 2680 RPM; I expected higher there given the relatively low altitude.
 
Resurrecting this thread because I have some new info.

I was going through the engine log the other day and I discovered the builder at one point swapped the nozzle in the carb. It originally had a 47-773 and he swapped it for a 47-828. What sort of difference would this be expected to make?

I finally found the nominal diameters for these two jet sizes.

The 47-773 is .1065” (#36 bit).
The 47-828 is .0935” (#42 bit).

Obviously nozzle size isn’t the only variable but when my carb was previously re-jetted that made a big step down.
 
Did some testing today. After takeoff I pitched down and accelerated to 2500 RPM. This resulted in 11 GPH.

At 8500’ I performed a lean test. Engine was in steady cruise at full throttle, 21.1” and 2640 RPM. OAT 33 dF.

At full rich fuel flow was 10.5 GPH. Full rich EGTs:

#1: 1390 dF
#2 1390 dF
#3 1520 dF
#4: 1460 dF

When leaning #3 was the first to peak at 1570 dF, approximately 9 GPH.
 
Did some testing today. After takeoff I pitched down and accelerated to 2500 RPM. This resulted in 11 GPH.

At 8500’ I performed a lean test. Engine was in steady cruise at full throttle, 21.1” and 2640 RPM. OAT 33 dF.

At full rich fuel flow was 10.5 GPH. Full rich EGTs:

#1: 1390 dF
#2 1390 dF
#3 1520 dF
#4: 1460 dF

When leaning #3 was the first to peak at 1570 dF, approximately 9 GPH.

WOW. 50* ROP at 8000 with full rich is quite lean. seems a jet change is in order, assuming you have confirmed that the mixture cable installation is allowing the arm on the carb to go full travel. Down low, WOT and 2500 should be well north of 11 GPH.


If I recall corrctly, I drilled out my jet to 38 or 39 and it is too rich at low altitude clmbs. I manually lean to a target EGT.

Larry
 
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WOW. 50* ROP at 8000 with full rich is quite lean. seems a jet change is in order, assuming you have confirmed that the mixture cable installation is allowing the arm on the carb to go full travel. Down low, WOT and 2500 should be well north of 11 GPH.

That said, I don't see how full mixture at 21" is flowing less than 29". Might be worthwhile to view the SB on the two piece venturi's to confirm that is not the issue.

If I recall corrctly, I drilled out my jet to 38 or 39 and it is too rich at low altitude clmbs. I manually lean to a target EGT.

Larry

Larry Vetterman sent me some information about the 3678 series carbs from a while back. As I understand it, once sufficient airspeed is achieved ram air is pressurizing the bowl causing it to lean out. That’s the most likely explanation for the flow difference, seeing as both were at WOT and the MP change was from atmospheric lapse.
 
Larry Vetterman sent me some information about the 3678 series carbs from a while back. As I understand it, once sufficient airspeed is achieved ram air is pressurizing the bowl causing it to lean out. That’s the most likely explanation for the flow difference, seeing as both were at WOT and the MP change was from atmospheric lapse.

The bowl vent is not exposed to ram air. If it was, the excess pressure on top of the fuel in the bowl would cause a rich condition, not lean. The same way that higher float settings cause rich conditions.
 
If my current jet is nominally a #42 (on paper, I’ll verify once I have it out), should I go one size at a time or jump to a #40 on first go? I have a #40 reamer if that makes it preferable to a drill bit.
 
I reamed my jet out from #42 to #40. I also addressed some throttle shaft play by having one of the bushings replaced - it’s nice and tight now.

The two size step brought my top end fuel flow up about 0.5 GPH (low altitude climb), and my leanest cylinder is now 100* ROP at full rich (8500’, WOT).

Obviously I could stand to go a little bit richer just looking at the total fuel flow, however I wonder if it is worthwhile to try and chase mixture distribution for the rear two cylinders. I’m aware it’s a common problem with carbureted Lycs and can in many cases be attributed to a limitation of the design due to the intake geometry. Is there anything worth trying here before I just accept it and pour in more fuel?
 
I have an almost identical situation.
50 deg ROP @ 8000, MS MA4 SPA 10-5217
Anyone have a repair manual for the carb that I could buy or borrow?
 
I reamed my jet out from #42 to #40. I also addressed some throttle shaft play by having one of the bushings replaced - it’s nice and tight now.

The two size step brought my top end fuel flow up about 0.5 GPH (low altitude climb), and my leanest cylinder is now 100* ROP at full rich (8500’, WOT).

Obviously I could stand to go a little bit richer just looking at the total fuel flow, however I wonder if it is worthwhile to try and chase mixture distribution for the rear two cylinders. I’m aware it’s a common problem with carbureted Lycs and can in many cases be attributed to a limitation of the design due to the intake geometry. Is there anything worth trying here before I just accept it and pour in more fuel?

The standard is 200 ROP when full rich, WOT at sea level. It is nice to have that margin for detonation prevention on Take off. You should be more worried about WOT SL than at cruise, as that is where you will have the most problems from being lean. Did you by chance measure the float height while the carb was apart? Fuel flow is determined mostly by jet size and fuel height in the bowl for any given airflow rate. A float that is slightly low will cause lean running. Even 64ths and 32nds can make a meaningful difference. Always measure float height when the carb is apart.

Larry
 
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The standard is 200 ROP when full rich, WOT at sea level. It is nice to have that margin for detonation prevention on Take off. You should be more worried about WOT SL than at cruise, as that is where you will have the most problems from being lean. Did you by chance measure the float height while the carb was apart? Fuel flow is determined mostly by jet size and fuel height in the bowl for any given airflow rate. A float that is slightly low will cause lean running. Even 64ths and 32nds can make a meaningful difference. Always measure float height when the carb is apart.

Larry

I did not measure the float height. The carb guru on the airport who did the bushing for me mentioned that he did not adjust it as it was unnecessary.

I can measure it next time I have the carb open since it looks like I’ll have to go in again anyway. I will note my carb has the brass float, if that makes any difference.
 
I did not measure the float height. The carb guru on the airport who did the bushing for me mentioned that he did not adjust it as it was unnecessary.

If he is any good, he would have measured it before making that statement.
 
Does anyone have experience with the nozzle PN 47-862 that MSA developed for the Carbon Cub with the Titan 340? Per SB-22, it is a drop in replacement for 47-773 jet that is standard in the 10-3678-32.

I'm waiting to hear back from MSA on the nominal flow rate. The Carbon Cub users report good results but I can only find qualitative reports. I wonder if the results will be applicable to the faster RVs.
 
Does anyone have experience with the nozzle PN 47-862 that MSA developed for the Carbon Cub with the Titan 340? Per SB-22, it is a drop in replacement for 47-773 jet that is standard in the 10-3678-32.

I'm waiting to hear back from MSA on the nominal flow rate. The Carbon Cub users report good results but I can only find qualitative reports. I wonder if the results will be applicable to the faster RVs.


Per MSA the 47-862 nozzle is the same flow rate as the 47-773. I ordered and received the 862 nozzle earlier this week, it measured to #36 ID (same as the 773).

I flew it today and performed some lean tests. At 2500’ and WOT, #1 peaked first with full rich being approximately 110* from peak. At 8500’ and WOT #2 peaked first approximately 250* from full rich.

My previous nozzle (47-828) had some aeration holes for atomization, and at 8500’ showed approximately a 130* spread between richest and leanest cylinder. After I reamed it from #42 to #40, the spread was 170*. The new nozzle (47-862) had significantly more aeration holes from the factory and showed a spread of approximately 80*.

Further testing is needed but it seems the 47-862 nozzle has gotten me close to where I need to be, at the least. I’ll also note I did measure my float height when I had the carb apart and found it to be at the nominal value of 7/32”.
 

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