Hiccup

[carusoam]

EGT1 seems to not be playing by the same rules as all the others… (?)

Red line, hanging low….

When you do a Gami spread, does it stand out?

Brief PP look only…

-a-

[aviatoreb]

28 minutes ago, carusoam said:

EGT1 seems to not be playing by the same rules as all the others… (?)

Red line, hanging low….

When you do a Gami spread, does it stand out?

Brief PP look only…

-a-

Do you meant it shows a lower number?  I am told - and I take - that to be that either it is placed not the same way relative to the hot gases - since absolute EGT has no meaning for that reason, or perhaps the sensor is a bit more aged?  In any case, notice that it is in lockstep with the other EGTs when they rise and fall for very close sync, which is the main thing, isn't it?

[Marauder]

Do you meant it shows a lower number?  I am told - and I take - that to be that either it is placed not the same way relative to the hot gases - since absolute EGT has no meaning for that reason, or perhaps the sensor is a bit more aged?  In any case, notice that it is in lockstep with the other EGTs when they rise and fall for very close sync, which is the main thing, isn't it?

The lower EGT1 reading could be just the placement in the exhaust stack. I would go back and look at the earliest data you have and see if it is following the same trend as now.


Sent from my iPhone using Tapatalk Pro

[carusoam]

4 hours ago, aviatoreb said:

Do you meant it shows a lower number?  I am told - and I take - that to be that either it is placed not the same way relative to the hot gases - since absolute EGT has no meaning for that reason, or perhaps the sensor is a bit more aged?  In any case, notice that it is in lockstep with the other EGTs when they rise and fall for very close sync, which is the main thing, isn't it?

Yes and no…

in the 60s… nobody had their EGT system installed using jigs…

By the 90s… the EGT holes started appearing in the same place with great regularity….

What I am seeing, in this case is… five EGTs are showing very tight numbers… and one is 100°F lower…

So… it is looking statistically, a bit out of place…

 

The Ovation got a ship’s EGT gauge… in the confluence of three exhaust streams… it reads higher than the usual EGTs similar to the TIT…

All O’s have this very standard EGT location… so our raw data can be shared quite easily… except, the reading goes directly to an analog instrument that is hard to read…. 
 

Some Os are a bit more fortunate, their EGT number shows up digitally on a G1000 screen…

 

In case it is a sensor issue… swap it with a neighboring cylinder and see if the issues follows the sensor….

 

Earlier… I couldn’t get the data to show on my iPad screen….

This afternoon, it showed up as usual….

Remember….

1) TIT is mathematically a higher number as it gets six peaks in the same timespan each cylinder gets one… the actual peak temperature will be lower than the peak temperature seen by the EGT sensors…

2) It’s amazing how this averaging affect actually shows up in the readings….

3) See if the Continental turbo exhaust system has specific EGT sensor locations… you might get surprised by what you may find…

4) With open ended exhaust (non-turbo), the exhaust gasses expand so rapidly… a sensor being further down the exhaust pipe by mm(s) tends to show a very large change in EGT because of the thermodynamics of gas expansion…

5) The turbo keeps the exhaust from expanding and cooling as rapidly as an open ended pipe…

6) This is why the V-clamps get used in place of slip joints… 

7) The actual flame temp of gasoline in air under adiabatic conditions is somewhere around 3k°F…   So our raw EGTs don’t show exactly much of what is going on….

But,

• if mounted the same
• operated the same
• even the raw numbers do have meaning….

Fun thoughts on a Saturday….

Best regards,

-a-

now for the data…

See that 2-6 are within about 40°F of each other…

EGT1 is 100°F lower then all of them.

If looking for a needle in the haystack… start with that one to see if anything pans out…

 

[aviatoreb]

3 hours ago, carusoam said:

Yes and no…

in the 60s… nobody had their EGT system installed using jigs…

By the 90s… the EGT holes started appearing in the same place with great regularity….

What I am seeing, in this case is… five EGTs are showing very tight numbers… and one is 100°F lower…

So… it is looking statistically, a bit out of place…

 

The Ovation got a ship’s EGT gauge… in the confluence of three exhaust streams… it reads higher than the usual EGTs similar to the TIT…

All O’s have this very standard EGT location… so our raw data can be shared quite easily… except, the reading goes directly to an analog instrument that is hard to read…. 
 

Some Os are a bit more fortunate, their EGT number shows up digitally on a G1000 screen…

 

In case it is a sensor issue… swap it with a neighboring cylinder and see if the issues follows the sensor….

 

Earlier… I couldn’t get the data to show on my iPad screen….

This afternoon, it showed up as usual….

Remember….

1) TIT is mathematically a higher number as it gets six peaks in the same timespan each cylinder gets one… the actual peak temperature will be lower than the peak temperature seen by the EGT sensors…

2) It’s amazing how this averaging affect actually shows up in the readings….

3) See if the Continental turbo exhaust system has specific EGT sensor locations… you might get surprised by what you may find…

4) With open ended exhaust (non-turbo), the exhaust gasses expand so rapidly… a sensor being further down the exhaust pipe by mm(s) tends to show a very large change in EGT because of the thermodynamics of gas expansion…

5) The turbo keeps the exhaust from expanding and cooling as rapidly as an open ended pipe…

6) This is why the V-clamps get used in place of slip joints… 

7) The actual flame temp of gasoline in air under adiabatic conditions is somewhere around 3k°F…   So our raw EGTs don’t show exactly much of what is going on….

But,

• if mounted the same
• operated the same
• even the raw numbers do have meaning….

Fun thoughts on a Saturday….

Best regards,

-a-

now for the data…

See that 2-6 are within about 40°F of each other…

EGT1 is 100°F lower then all of them.

If looking for a needle in the haystack… start with that one to see if anything pans out…

 

Good eye Anthony.  It is reading 100 deg lower - but I am convinced it is a red herring for the hiccup problem.  Looking historically it egt1 has been 100 degree or so lower for about 1.5 years and about 50 degree cooler for about 2.5 years - before that it was middle of the group.  I think the sensor is wearing out.  But still showing good trends since it is trending in monotone fashion with all the others.

So I think Ill get another sensor egt probe but only install it at next oil change

[carusoam]

Let’s see what else we can come up with…
 

Spark, air, fuel…

1) Plug going away… drops extra fuel into the exhaust… raises an EGT and TIT… becomes obvious while on one particular mag. (Doesn’t lower an EGT)

2) Fuel injector getting plugged/restricted… raises the EGT… becomes more obvious when leaning… (super clear during Gami spread test)

3) MP oscillations… really cool data captured in the JPI….

As you can see, the MP varies during the inflight mag check…

During the hiccup… if you can find that moment in the JPI data…

I bet the MP may have dropped similarly to the MP drop in your inflight mag check….

Find that moment in time… and review all the variables that your JPI has stored….

A vapor bubble in the fuel line might be the small thing we are looking for…

 

One bubble may be really hard to find…

But, if it has a family of vapor bubbles…. It would be cool if we could see it in the data…. 

A family of one is a pretty tiny statistical sampling…

Check this detail out…

circled in blue, MP oscillating with mag check…. Really stabile during regular ops….

 

The second graph is a close up of the same data…

[carusoam]

Any chance of knowing the date and being able to pull up the flight the hiccup occurred?

Best regards,

-a-

[Ragsf15e]

On 8/12/2022 at 8:15 PM, aviatoreb said:

I agree.  Good analysis.

I tried to do a LOP mag check today and here's what it looks like with a Surefly in advance setting.  I was only at 6,500' (~24.1" MP), so it would be even worse higher because it would have more advance.  Egts went up when I turned off the mag, but not a lot and the engine was still smooth.  Slight decrease in speed, but barely.  When I turned off the SF, EGTs went way up, very rough, and airspeed dropped quickly (#2 plug may be a bit weak too?).  I know yours is different since it's fixed timing, but since we were talking about it earlier, I'll post it here.  Before switching back to both, I pulled power back to prevent the backfire as SF takes 5-10ms to come back online - you can see the EGTs all fall together at the end.

 

[aviatoreb]

7 hours ago, Ragsf15e said:

I tried to do a LOP mag check today and here's what it looks like with a Surefly in advance setting.  I was only at 6,500' (~24.1" MP), so it would be even worse higher because it would have more advance.  Egts went up when I turned off the mag, but not a lot and the engine was still smooth.  Slight decrease in speed, but barely.  When I turned off the SF, EGTs went way up, very rough, and airspeed dropped quickly (#2 plug may be a bit weak too?).  I know yours is different since it's fixed timing, but since we were talking about it earlier, I'll post it here.  Before switching back to both, I pulled power back to prevent the backfire as SF takes 5-10ms to come back online - you can see the EGTs all fall together at the end.

 

LOPs mag check seems like a really good thing to do - probably periodically -  maybe not every flight but maybe every month or two?

But - I think definitely over an airport.

[Sue Bon]

SF?

[Ragsf15e]

1 hour ago, Sue Bon said:

SF?

Surefly mag.  It’s an electronic “modern”magneto.  Works well for me.  Some folks had issues with early 28v models.  It can do some basic advance timing.

[carusoam]

The strong spark of the SF seems to be a proving a good point….

On one mag, the SF is burning more/most of the fuel than the standard mag can…

so there isn’T much unburnt fuel making it into the exhaust…. On that single mag operation.

 

When doing mag checks… the readings probably aren’t as noticeably different… between SF and both… 

Best regards,

-a-

[Ragsf15e]

8 hours ago, carusoam said:

The strong spark of the SF seems to be a proving a good point….

On one mag, the SF is burning more/most of the fuel than the standard mag can…

so there isn’T much unburnt fuel making it into the exhaust…. On that single mag operation.

 

When doing mag checks… the readings probably aren’t as noticeably different… between SF and both… 

Best regards,

-a-

I don’t think it’s a “stronger spark”.  I don’t even think Surefly claims a stronger spark (electroair does).  I think it’s the timing difference.  @aviatoreb did a loo mag check and didn’t notice a difference because his SF is set on fixed timing.  Mine is on advanced timing which allows advance timing based on their semisecret MP and rpm formula.  I think the timing is why there’s a clear difference in my lop check.  
You’re right, on the ground, there’s no difference in a mag check, because there’s no advance.

[Ragsf15e]

8 hours ago, carusoam said:

The strong spark of the SF seems to be a proving a good point….

On one mag, the SF is burning more/most of the fuel than the standard mag can…

so there isn’T much unburnt fuel making it into the exhaust…. On that single mag operation.

 

When doing mag checks… the readings probably aren’t as noticeably different… between SF and both… 

Best regards,

-a-

Here’s from their website.  They don’t call it “stronger”…

PERFORMANCE

SureFly Ignition Modules deliver a more consistent spark energy with higher accuracy than traditional magnetos. Variable timing advance provides SureFly customers real fuel savings. Low power consumption and light weight (up to 2 lbs. lighter than a Bendix magneto) make SureFly Ignition Modules light on fuel and light on the wallet too.

 

[aviatoreb]

And the other thing about surefly or any electronic ignition, is I consider it to be more reliable and a longer lasting unit.

I thought the spark was considered stronger/longer leading to a better more consistent fuel burn?

[Ragsf15e]

2 hours ago, aviatoreb said:

And the other thing about surefly or any electronic ignition, is I consider it to be more reliable and a longer lasting unit.

I thought the spark was considered stronger/longer leading to a better more consistent fuel burn?

We need a EE to chime in because there’s some difference in spark but stronger/hotter I don’t think is it.  I think I remember longer maybe?  They do recommend a different gap, so there’s something there…

[aviatoreb]

3 hours ago, Ragsf15e said:

We need a EE to chime in because there’s some difference in spark but stronger/hotter I don’t think is it.  I think I remember longer maybe?  They do recommend a different gap, so there’s something there…

Ok - you are quite right!  I should know better...  so what I do know - Longer duration of the same power will make more energy.  But I don't know what is different - I have read stronger/longer and the only one of those two that is physical is longer and I don't know if its even true.  Stronger suggests higher power, so either higher volts or amps or both, but I am not sure if that happens either.

[Ragsf15e]

5 minutes ago, aviatoreb said:

Ok - you are quite right!  I should know better...  so what I do know - Longer duration of the same power will make more energy.  But I don't know what is different - I have read stronger/longer and the only one of those two that is physical is longer and I don't know if its even true.  Stronger suggests higher power, so either higher volts or amps or both, but I am not sure if that happens either.

My poor understanding of EE thinks it can’t be “hotter”/stronger because we’re using the same plugs with the same resistance, but possibly longer makes it “stronger” as you say?  @EricJ or @N201MKTurbo will come and write something perfectly reasonable that I have no chance understanding.

[carusoam]

Could be the words we are using to describe what it is….

 

The end result should be better propagation of the flame front that gets the fuel burning in less time…

Giving it more time to complete the burn, before the exhaust valve opens…

 

Kind of like the effect of altering the ignition timing earlier…   But using chemical reaction dynamics instead of mechanical timing…

 

Now… without some follow-up from SF… what data do we have to support this?

 

Let’s see if Ross has any input… @Shadrach (SureFly, spark…. Stronger than standard?)

 

Best regards,

-a-

[EricJ]

54 minutes ago, Ragsf15e said:

My poor understanding of EE thinks it can’t be “hotter”/stronger because we’re using the same plugs with the same resistance, but possibly longer makes it “stronger” as you say?  @EricJ or @N201MKTurbo will come and write something perfectly reasonable that I have no chance understanding.

I don't know the details, either, and getting air to break down and arc in a controlled fashion across a variety of pressures and temperatures involves more than just the EE part, so it wind up being a bit specialized.    That said, even with the same plugs with the same gap and the same resistance you can change the characteristics of the spark by increasing the applied voltage (which I always think is what somebody means when they say a "hotter" ignition system, they just cranked the voltage up).

Electronic ignition often gets a "hotter" (aka higher voltage) spike out of a coil to create a spark because they're using a longer cycle from a more consistent electrical supply than just what you can induce with a partial turn of a magnet.   A coil can charge over a longer period with a constant input supply in an electronic system, but relies on a partial cycle of an induced current from a moving magnet in a magneto.   So while a magneto is more than adequate, one benefit of an electronic system is potentially higher voltage at the plug, or longer if you want to engineer it that way.   There are probably a lot of tradeoffs to be engineered for managing the spark itself, but I don't know much about the relevant details of that part of it for improving performance.

The magneto spark gets weaker at lower rpm, since the magnet can't induce as much current in the coil at the lower speed, which is why we have impulse couplers, to snap the magnet at a higher speed for a cycle when it needs a spark generated.    The electronic ignition likes the lower rpm because it can charge the coil even longer before it needs to generate a spark, so the opportunity for a "hotter" spark for startup is good at low speeds, especially for startup.

One advantage of the dual mag is that the impulse coupler fires both sides instead of just one, so you can get spark on both plugs during startup.    You can do this with separate mags as well by putting an impulse coupler on each side instead of just one.

[Ragsf15e]

14 minutes ago, EricJ said:

I don't know the details, either, and getting air to break down and arc in a controlled fashion across a variety of pressures and temperatures involves more than just the EE part, so it wind up being a bit specialized.    That said, even with the same plugs with the same gap and the same resistance you can change the characteristics of the spark by increasing the applied voltage (which I always think is what somebody means when they say a "hotter" ignition system, they just cranked the voltage up).

Electronic ignition often gets a "hotter" (aka higher voltage) spike out of a coil to create a spark because they're using a longer cycle from a more consistent electrical supply than just what you can induce with a partial turn of a magnet.   A coil can charge over a longer period with a constant input supply in an electronic system, but relies on a partial cycle of an induced current from a moving magnet in a magneto.   So while a magneto is more than adequate, one benefit of an electronic system is potentially higher voltage at the plug, or longer if you want to engineer it that way.   There are probably a lot of tradeoffs to be engineered for managing the spark itself, but I don't know much about the relevant details of that part of it for improving performance.

The magneto spark gets weaker at lower rpm, since the magnet can't induce as much current in the coil at the lower speed, which is why we have impulse couplers, to snap the magnet at a higher speed for a cycle when it needs a spark generated.    The electronic ignition likes the lower rpm because it can charge the coil even longer before it needs to generate a spark, so the opportunity for a "hotter" spark for startup is good at low speeds, especially for startup.

One advantage of the dual mag is that the impulse coupler fires both sides instead of just one, so you can get spark on both plugs during startup.    You can do this with separate mags as well by putting an impulse coupler on each side instead of just one.

Wow, I was wrong, I almost understood that!  Thanks!

[Shadrach]

20 hours ago, carusoam said:

 

Let’s see if Ross has any input… @Shadrach (SureFly, spark…. Stronger than standard?

Eric covered this one in detail. The only thing I’ll add is that from a practical standpoint, I’ve never noted the need for a “hotter spark” (higher voltage) from my ignition system as the engine is currently configured. I believe it would take a number of modifications to other aspects of the engine before a more robust spark would prove useful. As it stands, I don’t think it makes a lot of difference operating a stock Lycoming with 8.7:1 pistons and 25° of advance.

[Will.iam]

I have a surefly and since I’m turbo it’s timing is fixed just like the mag. Having said that i see difference in my mag check of maybe 25 rpm if that on the sure fly where the mag drops 50 when ROP. LOP is even more drastic when i goto the mag will drop 150 rpm at about 25 degrees LOP and if i goto 60 degrees LOP the mag will stumble and miss where as the surefly fires fine. I contribute that to a mixture so lean the weaker spark from the mag just has a hard time igniting the mixture. They say to widen the gap on surefly to make a bigger arc as it has the voltage potential to make the jump. I however heard that trying to widen the gap on tempest finewire plugs can break off the wire and at $125 a pop, I’ll just let the surefly wear away the tip to get more space that way than risk breaking it. So i rotate my plugs between cylinders but keep them on the same surefly / mag as they were before.