ROP v. LOP

[Shadrach]

2 hours ago, mooniac15u said:

Here's another one (see Lie #6) where he recommends staying above 300 and ideally above 350. 

http://www.avweb.com/news/maint/182849-1.html

Busch's seems to have taken several similar but slightly varied stances. Whatever the setting, if lead is not building up in your plugs at 250df, then I can't see what the proble is.

[Shadrach]

9 hours ago, N201MKTurbo said:

But nobody dies from a few PPM of NOx!

That's were acid rain comes from.

 

[N201MKTurbo]

7 hours ago, Shadrach said:

That's were acid rain comes from.

 

I've never heard of anybody dying from acid rain especially in an airplane.

Besides, NOx is a minor contributor to acid rain SO2 from burning coal is the big problem.

[mooniac15u]

7 hours ago, Shadrach said:

Busch's seems to have taken several similar but slightly varied stances. Whatever the setting, if lead is not building up in your plugs at 250df, then I can't see what the proble is.

If lead and/or lead bromide aren't building up then it's not a problem. I was addressing the overly general statement that there's no such thing as too cold.

The question was posed about whether running in the mid 200s could be problematic. The answer to that is yes, it could be. 

[Greg_D]

9 hours ago, Shadrach said:

Busch's seems to have taken several similar but slightly varied stances. Whatever the setting, if lead is not building up in your plugs at 250df, then I can't see what the proble is.

The date that last article was published was 1998, long before he attended the APS class in Ada.  He has since modified his stance and I've often heard him say that mid 200s are not a problem as far as CHTs go.  He also used to say that as long as CHTs were below 380, things were good.  That changed too after he looked at some more data.  380 is way too hot if it's 10 degrees F outside.

[aviatoreb]

1 hour ago, Greg_D said:

The date that last article was published was 1998, long before he attended the APS class in Ada.  He has since modified his stance and I've often heard him say that mid 200s are not a problem as far as CHTs go.  He also used to say that as long as CHTs were below 380, things were good.  That changed too after he looked at some more data.  380 is way too hot if it's 10 degrees F outside.

RIght - CHT is a proxy for ICP.  The internal cylinder pressure would need to be very high to create CHTs of 380 if it is 10F outside (ground level temp - more relevant as to how OAT relates to standard since 10F is not cold up high if it is standard on the ground).

[Shadrach]

On 2/19/2017 at 1:03 AM, carusoam said:

 

Fuel injectors Get 'balanced' to produce close to identical fuel flow in each cylinder.

in lieu of curvy balanced air intakes, like on an IO550, an IO360 can put proper injectors in the engine to match the air flow that exists...

six cylinders are slightly more of a challenge to put curvy intakes on.

Best regards,

-a-

Not trying to pick nits but since this is for posterity:

Tuned Fuel injectors are tuned to give identical (as close as possible) fuel/air ratios to each cylinder, not identical fuel flow.  Tuning fuel injectors to an engine (especially a Continental) will often lead to the installation of injectors that flow at different rates in order to bring all cylinders into the same mixture and power range.

The angle valve Lycoming IO360s do indeed have a tuned induction (equal length intake runners). I believe this was Lycoming's first foray into the practice.

IO550s with the "log runner" intake have reasonably good air flow characteristics. They have somewhat less desirable fuel flow characteristics as fuel spills over from one intake to the next and then to the next. This often necessitates installing injectors that flow at slightly lower rates for the middle and last cylinder sharing an intake manifold.

[jlunseth]

Your comment brings up a thought I have been curious about Ross, and I don't know the answer but have a guess.  I am thinking about tuned injectors and untuned intakes, especially the "log runner" you talk about, which is what I have on my 231.  The intake is just a straight pipe on each side, with perpendicular droppers for each of the three cylinders.  Obviously, the cylinders nearest the end are likely to see less MP than the ones at the front, because the prior two cylinders are taking air.  But there is more to it than that.  Pressure waves occur.  The closing of each valve would cause one.  The log end might cause one also.  It seems to me that these effects might be different at different RPMs and manifold pressures.  Which brings me to my point.  Tuned injectors, as I understand it, are just injectors that have slightly different bore sizes so that if, say the rearmost cylinder is consistenly getting less air than the front one, the rearmost cylinder should also get less fuel (through a smaller bore size) in order to have the same fuel/air ratio.   This is sort of an "all other things being equal" system.  In other words, it assumes that at different power settings the relative difference in pressure between these cylinders will be the same, so the adjusted injector will deliver the same fuel/air ratio at these different power settings.  But if things are changing inside the untuned induction system as power setting change - say there is a standing wave caused by the log end, and the wave moves further from or closer to the log end, and thus closer to or further away from the nearest cylinder, that will change the relative pressures between the two cylinders, and the tuned injectors won't be so tuned anymore.  Or another example, at a very high pressure and low RPMs one would expect that there would be very little pressure difference between the cylinders because there is more than enough to go around, but at a lower pressure and higher RPMs that might not be true.

At any rate, my thought is that the "tuned" part of "tuned"injectors is not exact in an untuned induction system.  The MP is not necessarily relatively constant between the cylinders, it may change, and thus the "tuning" by the injectors is less effective.

[Shadrach]

49 minutes ago, jlunseth said:

Your comment brings up a thought I have been curious about Ross, and I don't know the answer but have a guess.  I am thinking about tuned injectors and untuned intakes, especially the "log runner" you talk about, which is what I have on my 231.  The intake is just a straight pipe on each side, with perpendicular droppers for each of the three cylinders.  Obviously, the cylinders nearest the end are likely to see less MP than the ones at the front, because the prior two cylinders are taking air.  But there is more to it than that.  Pressure waves occur.  The closing of each valve would cause one.  The log end might cause one also.  It seems to me that these effects might be different at different RPMs and manifold pressures.  Which brings me to my point.  Tuned injectors, as I understand it, are just injectors that have slightly different bore sizes so that if, say the rearmost cylinder is consistenly getting less air than the front one, the rearmost cylinder should also get less fuel (through a smaller bore size) in order to have the same fuel/air ratio.   This is sort of an "all other things being equal" system.  In other words, it assumes that at different power settings the relative difference in pressure between these cylinders will be the same, so the adjusted injector will deliver the same fuel/air ratio at these different power settings.  But if things are changing inside the untuned induction system as power setting change - say there is a standing wave caused by the log end, and the wave moves further from or closer to the log end, and thus closer to or further away from the nearest cylinder, that will change the relative pressures between the two cylinders, and the tuned injectors won't be so tuned anymore.  Or another example, at a very high pressure and low RPMs one would expect that there would be very little pressure difference between the cylinders because there is more than enough to go around, but at a lower pressure and higher RPMs that might not be true.

At any rate, my thought is that the "tuned" part of "tuned"injectors is not exact in an untuned induction system.  The MP is not necessarily relatively constant between the cylinders, it may change, and thus the "tuning" by the injectors is less effective.

My understanding of injector tuning is the same as yours. I have never had to work through the tuning process. My engine will easily and smoothly run to 80LOP or more depending on power setting with stock injectors. Years ago I asked Walter Atkinson (APS) about the Continental intake. He said that APS's data indicated the log runner intake provided surprisingly even amount of air to each cylinder. The bigger issue as described previously was the fuel that migrated into the intake and downstream to the next cylinder every time an intake valve closed.

The pressure wave you mention is why intake runner are curved to be a certain length. The goal is to have the pressure wave bounce back to the intake valve the moment it opens at a given rpm range. Not really possible with the log runner, but the fact that it is boosted may make it less significant. I was helping a friend today repair the intake pipe on his Turbo BMW. The intake on that car does not appear to be tuned in any way. I compare that to the intake on my naturally aspirated Porsche which appears to have been very carefully shaped with a flapper that opens and closes to vary intake runner length with RPM. 

[N201MKTurbo]

1 hour ago, jlunseth said:

Your comment brings up a thought I have been curious about Ross, and I don't know the answer but have a guess.  I am thinking about tuned injectors and untuned intakes, especially the "log runner" you talk about, which is what I have on my 231.  The intake is just a straight pipe on each side, with perpendicular droppers for each of the three cylinders.  Obviously, the cylinders nearest the end are likely to see less MP than the ones at the front, because the prior two cylinders are taking air.  But there is more to it than that.  Pressure waves occur.  The closing of each valve would cause one.  The log end might cause one also.  It seems to me that these effects might be different at different RPMs and manifold pressures.  Which brings me to my point.  Tuned injectors, as I understand it, are just injectors that have slightly different bore sizes so that if, say the rearmost cylinder is consistenly getting less air than the front one, the rearmost cylinder should also get less fuel (through a smaller bore size) in order to have the same fuel/air ratio.   This is sort of an "all other things being equal" system.  In other words, it assumes that at different power settings the relative difference in pressure between these cylinders will be the same, so the adjusted injector will deliver the same fuel/air ratio at these different power settings.  But if things are changing inside the untuned induction system as power setting change - say there is a standing wave caused by the log end, and the wave moves further from or closer to the log end, and thus closer to or further away from the nearest cylinder, that will change the relative pressures between the two cylinders, and the tuned injectors won't be so tuned anymore.  Or another example, at a very high pressure and low RPMs one would expect that there would be very little pressure difference between the cylinders because there is more than enough to go around, but at a lower pressure and higher RPMs that might not be true.

At any rate, my thought is that the "tuned" part of "tuned"injectors is not exact in an untuned induction system.  The MP is not necessarily relatively constant between the cylinders, it may change, and thus the "tuning" by the injectors is less effective.

I think you will find the rear cylinders have a higher intake pressure then the front ones. The air in the intake plenum has mass and wants to continue straight ahead because of inertia. It will decelerate at the back of the plenum and bunch up back there. This will make the rear cylinders leaner than the front.

[Shadrach]

7 minutes ago, N201MKTurbo said:

I think you will find the rear cylinders have a higher intake pressure then the front ones. The air in the intake plenum has mass and wants to continue straight ahead because of inertia. It will decelerate at the back of the plenum and bunch up back there. This will make the rear cylinders leaner than the front.

It's my understanding that the folks at GAMI generally see the opposite when tuning injectors. On Continentals with stock injectors, the last (rear or front depending on the engine) cylinder on the intake runner is the richest not the leanest, the middle is the next richest and the first is the leanest.

[N201MKTurbo]

50 minutes ago, Shadrach said:

It's my understanding that the folks at GAMI generally see the opposite when tuning injectors. On Continentals with stock injectors, the last (rear or front depending on the engine) cylinder on the intake runner is the richest not the leanest, the middle is the next richest and the first is the leanest.

From GAMIs website:

A pattern appears. Cylinders # 1 & 2 (the rear most cylinders) peak first. They are the leanest cylinders. Cylinders # 3 & 4 peak next. They are the middle two cylinders in the TCM cylinder numbering scheme. Cylinders # 5 & 6 are the front cylinders and they peak last. They are the richest cylinders. Depending upon a number of factors, either #1 or #2 may peak first, but the pair should peak at nearly the same fuel flow. The same is true of #3 & #4 and #5 & #6.

[Shadrach]

On 2/25/2017 at 9:34 PM, N201MKTurbo said:

From GAMIs website:

A pattern appears. Cylinders # 1 & 2 (the rear most cylinders) peak first. They are the leanest cylinders. Cylinders # 3 & 4 peak next. They are the middle two cylinders in the TCM cylinder numbering scheme. Cylinders # 5 & 6 are the front cylinders and they peak last. They are the richest cylinders. Depending upon a number of factors, either #1 or #2 may peak first, but the pair should peak at nearly the same fuel flow. The same is true of #3 & #4 and #5 & #6.

Yes, but without knowing which way the intake is running, it's hard to discern to what Mr. Braly is attributing the imbalance.  If one looks at the images below, the text you've quoted makes my point rather than counters it.

 

[N201MKTurbo]

1 hour ago, Shadrach said:

Yes, but without knowing which way the intake is running, it's hard to discern to what Mr. Braly is attributing the imbalance.  If one looks at the images below, the text you've quoted makes my point rather than counters it.

 

That is not a Mooney 231 engine. They all feed air from the front. The engine he is discussing also feeds air from the front.

[Shadrach]

2 hours ago, N201MKTurbo said:

That is not a Mooney 231 engine. They all feed air from the front. The engine he is discussing also feeds air from the front.

I am aware of how the intakes (front to back) are configured on most TSIO360s.  We need not delve into semantics as we both likely understand that the "last cylinder" means the opposite end of the intake, as in the end were the log runner terminates. 

You quoted GAMI trying to prove your incorrect assertion about "intake charger inertia" making the "rear cylinders leaner than the front".  In the quote you posted, Gami (George Braly) was talking about standard TCM engines which have intakes that run firewall forward.  You completely (if not deliberately) omitted that context.  In the inset box right next to the text you quoted he says the following:

Operators of Senecas and Cessna 337s, with the TCM TSIO-360 engines should be aware that the pattern for those engines is precisely the "reverse" of that shown in figure 1. These engines also have a runner log-branch induction system, but the air starts at the front and moves to the rear causing the pattern to reverse itself.

While he omits the Mooney 231, it's clear he's referring to the same intake set up. Continental cylinders run progressively richer with each placement downstream of the first cylinder on the intake (which way it runs does not matter).  Correcting this issue is what created the cottage industry for tuned injectors.

I mean no offense, but if you're going to quote a respected source to counter someone's statement, at least take the time to thoroughly read the material.

 

[N201MKTurbo]

4 hours ago, Shadrach said:

I am aware of how the intakes (front to back) are configured on most TSIO360s.  We need not delve into semantics as we both likely understand that the "last cylinder" means the opposite end of the intake, as in the end were the log runner terminates. 

You quoted GAMI trying to prove your incorrect assertion about "intake charger inertia" making the "rear cylinders leaner than the front".  In the quote you posted, Gami (George Braly) was talking about standard TCM engines which have intakes that run firewall forward.  You completely (if not deliberately) omitted that context.  In the inset box right next to the text you quoted he says the following:

Operators of Senecas and Cessna 337s, with the TCM TSIO-360 engines should be aware that the pattern for those engines is precisely the "reverse" of that shown in figure 1. These engines also have a runner log-branch induction system, but the air starts at the front and moves to the rear causing the pattern to reverse itself.

While he omits the Mooney 231, it's clear he's referring to the same intake set up. Continental cylinders run progressively richer with each placement downstream of the first cylinder on the intake (which way it runs does not matter).  Correcting this issue is what created the cottage industry for tuned injectors.

I mean no offense, but if you're going to quote a respected source to counter someone's statement, at least take the time to thoroughly read the material.

 

If that's what you want to believe, go ahead.

[jlunseth]

The intake runs front to back with the log end at the back.  Its been quite awhile since I have bothered to use the "lean test" feature of my JPI to lean the engine out, but my recollection is that In my engine, #2 usually peaks first, then a bunch virtually at once, and one of the front cylinders I believe it is 5, goes last.  But I have GAMIs not factory injectors so my experience doesn't really count.  At idle after start up though, 1 & 2 can have so little pressure that they don't even register on my JPI as having an EGT.  Either they aren't firing, or the temp is so low it is below what registeres on the JPI.

[Shadrach]

34 minutes ago, jlunseth said:

The intake runs front to back with the log end at the back.  Its been quite awhile since I have bothered to use the "lean test" feature of my JPI to lean the engine out, but my recollection is that In my engine, #2 usually peaks first, then a bunch virtually at once, and one of the front cylinders I believe it is 5, goes last.  But I have GAMIs not factory injectors so my experience doesn't really count.  At idle after start up though, 1 & 2 can have so little pressure that they don't even register on my JPI as having an EGT.  Either they aren't firing, or the temp is so low it is below what registeres on the JPI.

They shouldn't be getting "pressure" at idle. Peculiar that they don't register. Old radials with lower C/Rs than your engine generate EGT at idle.  Perhaps they're so rich at idle that the the exhaust event is cooling below the display threshold.  Next time try leaning at idle to see if they come alive!

[slowflyin]

Nice LOP day in my lowly F.   A little up and down draft but for over an hour she ran 152-154.   Hottest CHT (#3) settled out at 156 with #3 just barely LOP. (7-8 degrees)   

 

Edited March 1, 2017 by slowflyin
file to large

[slowflyin]

Wow! Uploaded the file in it's original format.   I'll reformat and shrink it down.

[slowflyin]

This one is  smaller with acceptable resolution.

LOP.mp4

[jlunseth]

On 2/28/2017 at 11:12 PM, Shadrach said:

They shouldn't be getting "pressure" at idle. Peculiar that they don't register. Old radials with lower C/Rs than your engine generate EGT at idle.  Perhaps they're so rich at idle that the the exhaust event is cooling below the display threshold.  Next time try leaning at idle to see if they come alive!

That is lean.  I lean to idle rise or a little past, immediately on starting.  The engine is not rough, those two cylinders just don't register until I bring the RPMs up.  At the low speed the turbo is not working much if at all.  Don't remember exactly what it takes to get them to check in - 1200 RPMs or more.  There might be a minimum EGT number below which the JPI does not display, I have never checked that out.

Edited March 2, 2017 by jlunseth