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Climb power and CHT?s

TJCF16

Well Known Member
I have an 0-320 with a Hartzell constant speed prop. I just added two P-MAGs. I was wondering climb out settings? I use Full throttle on takeoff I get 2700 rpm 28.8 on manifold, after 500 feet agl I usually pull the power back to 2500 RPM for the rest of the climb at 600 ft per min, mixture full rich. My #3 CHT got up to 440 I lowered the nose pull powere a bit and opened the cowl flap and it came down to 393 in about two to three min. I have never had that cylinder get that hot. I was just wondering what others climb at with p-mags. Not sure how these P-mags should act? Maybe I should not climb so fast maybe climb at IAS.
I had a lightspeed before with a slickmag. Things seem a little different.
 
What is your fuel flow at T/O power? The carbureted 320's are notoriously lean in RV applications. Having a C/S prop means you need even more fuel flow than us FP guys because you are getting much more power on T/O. I have drilled out the jet on my carb twice in order to get the fuel flow I need to keep things cool on takeoff.

Also, do you have all 4 cylinders wired for CHT? I say that because at WOT my front two cylinders (1 and 2) are the hottest ones, so if you aren't watching those, they may be even hotter than #3. Lastly, have you done the baffle mode to increase cooling for cylinder #3?

Chris
 
I just added two P-MAGs.

My #3 CHT got up to 440

I have never had that cylinder get that hot.

Things seem a little different.

Well, pretty sure you have identified the issue.

Lots of folks here have experience with setting Pmags, but I am not one of them, so will let others advise........
 
I have done all the baffle mods. I doo have CHT probes on all cylinders. My front cylinders don?t get above 400. I think the jetting could be the answer. Allen at antisplat recommends the drill out the jet. I never looked at what the fuel flow was! Never had a carb apart!
 
Pretty sure your carburetor has an enrichment valve at wot.. try climbing out at full power, it'll run cooler. You're probably thinking that you are being more kind and gentle to the engine by pulling it back, but in reality, you're leaning it and probably adding stress (heat ).
 
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You can also retard the timing on the pmags (of course that will negate some of the benefits). And of course, give the baffles a very close look to make sure they are cooling as well as possible.

Chris
 
I am assuming this is new and appeared with the installation of the Pmags. What you are seeing is the byproduct of the pre-programed and unchangealbe
advance curves that are too aggressive. The curves are fine for cruise, but you need a more retarded timing for climb due to the reduced cooling available (optimum advance produces more CHTs than the more retarded settings of the mags). This is one of the reasons that I don't recommend products with a fixed and unchangelable advance curve.

I use a megasquirt system and have two switches to help control my timing. One is used for switching between A & B curves (curves of my design) that let me have either 25* or 34*, based upon ROP or LOP at my lower MAP ranges. I also have another switch that retards timing by 5* from whatever is called out in the map. I mostly use this for climb. I get high CHT's in the later stages of climbs to 8000', when the MAP goes down and my table starts advancing agressively. In the earlier parts of climb, my MAP is higher, so my timing is 25* and I am plenty cool.

I recommend the SDS product, as it allows the user the flexibility to manage situations like the one you are now experiencing. You are seeing the downside to a plug and play system where all decisions are made for you.

Larry
 
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Tim,

You say that you, "usually pull the power back to 2500 RPM for the rest of the climb"

That's fine, just leave the throttle full open and the mixture full rich until you get to an altitude at which you'll start leaning in the climb.

I agree that the aggressive timing of the Pmags is responsible for the higher temps if that's all you changed. You can try accelerating to 120KIAS immediately after takeoff and climbing at that speed. If that doesn't help, you may want to do something with the timing/Pmags. Also, try to keep the CHT's cool before you start your takeoff. If they're already around 350 when you take the runway, you don't have much headroom to work with.

Have an engine monitor? Check the full power fuel flow both with and without the electric boost pump running and report back.

Good luck; summer is coming and CHT's will only get higher without some changes.

Cheers, David
RV-6A A&P
 
I have an 0-320 with a Hartzell constant speed prop. I just added two P-MAGs. I was wondering climb out settings? I use Full throttle on takeoff I get 2700 rpm 28.8 on manifold, after 500 feet agl I usually pull the power back to 2500 RPM for the rest of the climb at 600 ft per min, mixture full rich.

CHT is much more dependent on RPM (i.e. mass flow, and number of firing events in a time period) than MP. You're doing it right.

I had a lightspeed before with a slickmag. Things seem a little different.

As delivered, the P-mag A curve starts at 26.6? BTDC, while the B-curve starts at 30.8? BTDC. Both rise further as MP drops in climb. Install the jumper to run the A-curve. Report back.
 
I will look at the fuel flow and other suggestions. The only thing I changed was the two p-mags. There is something amiss. May take some searching but should find a solution
 
Did you install the jumper (piece of wire) between pins 2 and 3, or not?

This jumper runs the A curve, which is retarded more than the B curve. Another option is use the B curve and use the EICAD program on your computer to set the timing the same as your standard Mag by setting the max advance to 25 degrees.

Mine ran hot at first and I brought it back to Normal settings, during this process I also switched my top baffle seals from Vans standard material to McFarlane cowl saver material. I was able to make one continuous piece along each side and the back, vs. segmented pieces. I also had a gap at the front inlets, outboard edges, and with the new material, made sure they tucked behind the sides of the inlets. Despite hours of baffle and jetting work, this was the smoking gun; what I thought was a good seal, was not. CHT?s run cool now and have advanced the timing back to 31.4, so far...
 
Tim is based about eight miles from me and when he installed the P-mags, I used the EICAD program from E-mag to set the Advance Shift to a -1.4 degrees on both his P-mags (I also lowered his Max Advance by 1.4 degrees), which puts them at 25.2 degrees for takeoff. As with any custom configuration on the P-mags, do you not install "the jumper".

After talking with Tim on the drive in this morning, I do not believe his issue is with the P-mag or fuel delivery. The reason being is that if either were the issue, then all the CHT's would be high due to bad timing or a lean mixture. If he was injected, I would imagine it is possible that a jet could be clogged forcing #3 to run lean.

That brings us to two possible issues, either a baffle seal around that cylinder or a leak on the intake tube for #3. He is going to inspect the intake tube gaskets and hopefully install the cowling and inspect the seals with his borescope. (His prop is out for an inspection, so no flying for a week or two.)

I will also stop by his hangar later this week and verify the P-mag timing is correct. It was correct when we left the hangar after I set them but it never hurts to verify such things.

A thought for all of you installing P-mags but are not planning on an EICommander; Tim does not have an EIC but he did bring the connections for one into his cockpit and terminated them with two female DB9 connectors under his panel. This allows for easy adjustment with the EICAD program. Should he ever buy an EIC, he can simply make a Y cable that goes from both DB9 connectors to the EIC's DB15 connector.
 
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Just a little more information. when I did my first test flight with the P-Mags at cruise I was running the following.

8,000 ft OAT 32
RPM 2270 Manifold 21.9

CHT #1- 326
#2- 348
#3- 345
#4- 354
 
Pretty sure your carburetor has an enrichment valve at wot.. try climbing out at full power, it'll run cooler. You're probably thinking that you are being more kind and gentle to the engine by pulling it back, but in reality, you're leaning it and probably adding stress (heat ).
#canconfirm. My -6 has conventional mags, but I was struggling with high CHT's on climbout for a while before someone clued me in that throttling back early wasn't the answer. Staying at full throttle kept my temps in check until I was ready to level off and cruise.

Keeping the nose down and climbing at higher airspeed and lower vertical speed also helps... It's great that we can go up at 1500-2000ft/min but doing so reduces airspeed, airflow over the engine, and its ability to carry heat away.
 
Tim, please confirm ;

1. This happened after installing pmags. No other changes to the aircraft.

2. It only happens on climb.

3. It only is effecting no. 3 cylinder.

Question-------are you still running aircraft spark plugs or did you switch to auto plugs?
 
This thread was started with respect to an O320 that probably has a MA-4 carb which operates quite differently than the carb that you would expect to see on a O360. With the MA-4spa, it is my understanding that throttle position doesn't effect the "enrichment" circuit as it does on the larger carbs.
 
A friend and his carbureted RV-6 recently had the same issue with one P-Mag. We built the cable to connect it to the computer and re-programmed the P-Mag to reduce the Adv Shift and Max Adv (as well as Max RPM). Current settings are as follows but we're still tweaking.

Adv Shift: -1.4
Max Adv: 36.4 (this is affected by Adv Shift so current max is actually 35)
Max RPM: 2816

Temps are now well under control with no noticeable power loss.

Someone above mentioned the P-Mag is not configurable. It certainly is but not to the extent of some other systems.

Cost of making the cable is about $10 and takes less than an hour. You can run it though the firewall to allow changes by a co-pilot while flying or just tie it down in the engine compartment for ground adjustments. PM me if you'd like more information.
 
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A friend and his carbureted RV-6 recently had the same issue with one P-Mag. We built the cable to connect it to the computer and re-programmed the P-Mag to reduce the Adv Shift and Max Adv (as well as Max RPM). Current settings are as follows but we're still tweaking.

Adv Shift: -1.4
Max Adv: 36.4 (this is affected by Adv Shift so current max is actually 35)
Max RPM: 2816

Temps are now well under control with no noticeable power loss.

Someone above mentioned the P-Mag is not configurable. It certainly is but not to the extent of some other systems.

Cost of making the cable is about $10 and takes less than an hour. You can run it though the firewall to allow changes by a co-pilot while flying or just tie it down in the engine compartment for ground adjustments. PM me if you'd like more information.
That is exactly how I configured Tim's P-mag's. (See my post above.)

Regarding your RPM limit, I would raise that up one notch to just over 3,000 RPM. It is easy to hit 2816 and when you do, the ignitions will stop firing, dumping raw fuel into the exhaust. When the prop slows down and the ignition starts firing again, that raw fuel in the exhaust will light off with a LOUD bang. That causes the pilot to need to change their underpants as soon as they land.
 
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This thread was started with respect to an O320 that probably has a MA-4 carb which operates quite differently than the carb that you would expect to see on a O360. With the MA-4spa, it is my understanding that throttle position doesn't effect the "enrichment" circuit as it does on the larger carbs.

You are correct Scott. In talking with Tim this morning, he (and I) was thinking it has the enrichment circuit. I'm not convinced it is a fuel delivery issue. If that was it, then all four cylinders would run hot, not just one.
 
That is exactly how I configured Tim's P-mag's. (See my post above.)

Regarding your RPM limit, I would raise that up one notch to just over 3,000 RPM. It is easy to hit 2816 and when you do, the ignitions will stop firing, dumping raw fuel into the exhaust. When the prop slows down and the ignition starts firing again, that raw fuel in the exhaust will light off with a LOUD bang. That causes the pilot to need to change their underpants as soon as they land.

Thanks. Missed our post, somehow. We set the Max RPM per Brad's recommendation and 2600 RPM limit of the prop but I understand the concern.
 
Thanks. Missed our post, somehow. We set the Max RPM per Brad's recommendation and 2600 RPM limit of the prop but I understand the concern.

If your FP prop is pitched correctly, the only way you are going to hit the 2800 RPM Rev limiter is by getting the nose down and not retarding the throttle, which a good bump can do in a hurry. That's why mine is now one setting higher, as is Tim's who has a CS prop. It will still save him from an overhaul.
 
This thread was started with respect to an O320 that probably has a MA-4 carb which operates quite differently than the carb that you would expect to see on a O360. With the MA-4spa, it is my understanding that throttle position doesn't effect the "enrichment" circuit as it does on the larger carbs.

I have a 320 and my research a few years ago showed some of the MA-4SPA models having an economizer and some didn't. The economizer reduces flow through the main jet at lower MAP levels. While not technically a WOT enrichment, it provides the same function - higher than designed fuel flow at high MAP levels, usually associated with WOT condition. I don't know the cutoff points, but would speculate around 26.

Larry
 
I'm not convinced it is a fuel delivery issue. If that was it, then all four cylinders would run hot, not just one.

Not necessarily. The poor fuel distribution can cause some cylinders to run much leaner than others at different throttle settings. It certainly does on mine.

Chris
 
Tim is based about eight miles from me and when he installed the P-mags, I used the EICAD program from E-mag to set the Advance Shift to a -1.4 degrees on both his P-mags (I also lowered his Max Advance by 1.4 degrees), which puts them at 25.2 degrees for takeoff. As with any custom configuration on the P-mags, do you not install "the jumper".

After talking with Tim on the drive in this morning, I do not believe his issue is with the P-mag or fuel delivery. The reason being is that if either were the issue, then all the CHT's would be high due to bad timing or a lean mixture. If he was injected, I would imagine it is possible that a jet could be clogged forcing #3 to run lean.

That brings us to two possible issues, either a baffle seal around that cylinder or a leak on the intake tube for #3. He is going to inspect the intake tube gaskets and hopefully install the cowling and inspect the seals with his borescope. (His prop is out for an inspection, so no flying for a week or two.)

I will also stop by his hangar later this week and verify the P-mag timing is correct. It was correct when we left the hangar after I set them but it never hurts to verify such things.

A thought for all of you installing P-mags but are not planning on an EICommander; Tim does not have an EIC but he did bring the connections for one into his cockpit and terminated them with two female DB9 connectors under his panel. This allows for easy adjustment with the EICAD program. Should he ever buy an EIC, he can simply make a Y cable that goes from both DB9 connectors to the EIC's DB15 connector.

Given that this problem appeared immediately after the installation of the Pmags (please correct me if not accurate), it would be difficult to assume the problem is unrelated to the installation. I imagine it is possible that the owner disturbed the intake gaskets or something else during the installation. However, given the immediate onset of the problem, it seems logical to focus on what has changed. I'm sure he could improve the baffles, but what are the odds they just started leaking the day he installed the pmags. Same with fuel flow. If the temps were normal before the installation, I can't imagine drilling a jet is going to fix the new problem on #3.

I would spend some time thinking about everything that I touched when I did the install. Have you had the cowl off since? Maybe a baffle seal was kinked or out of position, maybe a rag was left on top of the cylinder, etc. Has someone confirmed that the timing was set properly. It wouldn't be the first time that someone timed the ignition incorrectly on a Lycoming. Did you confirm that each sparkplug was tightened, etc. Also, I don't believe you are looking for a lean condition on #3. Lean cylinders don't show these types of disparities. If the other three cylinders are under 400 and let's say 100* ROP, you won't see a 50 degree increase in CHT by leaning to peak from 100 ROP (Peak CHTs occur at approx 80 ROP and will fall on either side of it). I don't know what the typical CHT spread is between 250 ROP and 80 ROP, but I can't imagine it is 50*. Maybe someone else can chime it, I don't ever run that rich. Detonation is a more likely culplrit for this type of spread. Detonation is most often caused by timing issues, going back to what has just changed.

Good luck,

Larry
 
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Given that this problem appeared immediately after the installation of the Pmags (please correct me if not accurate), it would be difficult to assume the problem is unrelated to the installation. I imagine it is possible that the owner disturbed the intake gaskets or something else during the installation. However, given the immediate onset of the problem, it seems logical to focus on what has changed. I'm sure he could improve the baffles, but what are the odds they just started leaking the day he installed the pmags. Same with fuel flow. If the temps were normal before the installation, I can't imagine drilling a jet is going to fix the new problem on #3.

I would spend some time thinking about everything that I touched when I did the install. Have you had the cowl off since? Maybe a baffle seal was kinked or out of position, maybe a rag was left on top of the cylinder, etc. Has someone confirmed that the timing was set properly. It wouldn't be the first time that someone timed the ignition incorrectly on a Lycoming. Did you confirm that each sparkplug was tightened, etc. Also, I don't believe you are looking for a lean condition on #3. Lean cylinders don't show these types of disparities. If the other three cylinders are under 400 and let's say 100* ROP, you won't see a 50 degree increase in CHT by leaning to peak from 100 ROP (Peak CHTs occur at approx 80 ROP and will fall on either side of it). I don't know what the typical CHT spread is between 250 ROP and 80 ROP, but I can't imagine it is 50*. Maybe someone else can chime it, I don't ever run that rich. Detonation is a more likely culplrit for this type of spread. Detonation is most often caused by timing issues, going back to what has just changed.

Good luck,

Larry

Larry, here is why I don't believe it is a timing issue:

1. The P-mafs fire two cylinder at the same time. If there was a timing issue and one coil pack failed, at a minimum, two cylinders would show high CHT's, not just one.
2. I was there when Tim set his timing to TDC and we verified each other. If the timing was off, all four cylinders would have high CHT's, not just one.
3. I configured the standard timing setup down 1.4 degrees, as I recommend, and emailed Tim screen shots of both configurations for his records.

No, I can't think of any way Tim's issue is related to the P-mags but I would love to be proven wrong.
 
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Tim just called and I found out two things.

1. He had never performed a climb like the one that prompted this thread with his old ignition so it is not possible to say his high CHT is a result of the new ignitions or if the issue was always there.

2. He does not have the deflectors in front of his #1 and #2 cylinders to push the cooling air up over the front cylinders and help cool the rear ones.

He was not the builder but since the plane came from Canada, the original builder put plate nuts in to make the deflectors removable. We are going to start with aluminum tape to see if that helps and then will make a set of deflectors. (I also made mine removable, so we already have a pattern.)
 
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