M20K 252 TSIO 360 - SB Engine data

[Fix]

Do anyone of my fellow TSIO 360-SB owners (MB works too) have engine data to share?
I'm trying to get my engine to run LOP smooth as I can and need some input for reference.

I would be happy if you can share some flights with me where you have.

4000-6000 feet, 26" / 2500 rpm with 10.4g/h (LOP) and 12.6g/h (ROP)
and if you have same for 12000feet->

 

[Falcon Man]

I have run three different K models at LOP - two MB and one SB engine. Average settings at 14,000 to 18,000 were 2200 RPM, 28-30 MP and ~ 25F degrees LOP of hottest cylinder CHT, Fuel flow 10-11 gph. None of the engines ran smooth < 25F LOP. GAMI spread was 0.3-0.5 gph on stock injectors.

[Aerodon]

You need to look up the gami test to get the gami spread - the difference in fuel flow between the first and last cylinder to peak.  I think the target is 0.5 GPH, but it may be less.

The MB/SB engines should be good out the box, but Gami can help you refine them.

 

Don

 

[Pinecone]

Mine (-SB) runs well very LOP.

I did the GAMI spread test and sent the data to John-Paul and he refused to sell me GAMIjectors.

What are you trying to figure out?  If you engine is not running well LOP, the spread is too high.  You may be able to swap the factory injectors around to get it closer.  But it all starts with the test of spread between the cylinders.

I run 29.5 - 31.5 inches, 2300 RPM at 10.1 GPH.  This is about 62 - 63% power.   The different manifold pressures do not change performance, they just change how LOP you are.  When LOP, power is based on fuel flow.  I just MP to keep the CHTs below 380 with little or no cowl flap opening.

Turbo engines we can pick a power setting and adjust to run that at various amounts of LOP.  NA guys have to reduce fuel flow (thus power) get more LOP.

[Fix]

I have a GAMI spread of 0.5GPH more or less when I tested. (tested several times)

Can't get it running smooth as I want at higher altitudes. 4000->
I tried some things that Paul K suggested to me, but still it's not running smooth as I want.
Either my GAMI spread is to high or there are other things messing with me.

Have some ideas why it not running smooth and I'm trying to check them one by one.
Can see on my engine data that when I run for example 25" 2500rpm with 12.6g/h (65% ROP) I have my EGT values per each cylinder always in the same order.
I also have that same EGT order with 11.6g/g or if I fly FT/2600/26g/h.
Engine here is smooth.

Soon as I lean my mixture to 26" 2500rpm with 10.4g/h (10.1-10.3) my cylinders change EGT wise and I starting to get roughness/vibrations.
I tried different settings trying to find a sweet spot, but with no success.

So if someone can share some flights on Savvy I can try to compare if how other engines behave and that give me some clues.
I might suspect that there is a Induction leak on Cylinder 2 and maybe Cylinder 3 since those are the ones that changes.
That's why it would be very interesting to take a look on some engine data.

 

I have and/or tested.
Tempest Fine Wire plus. (gapped to 0.017") - ~500h on them since new, looks good.
SureFly + Slick 6324 (First I have 2x Slick Mags, one of them dropped little much, but within limit. Bought an SureFly, but no change with LOP)
Both mags are timed with in 0.5 degrees (if we didn't do anything wrong. Used timing pin and digital measure)
We did a Induction test, but couldn't see any leakage with soapy water and pressure also didn't change)
No other obvious signs that could give any leads.
Tighten the screws of the rubber fittings to the inductions tubes.


What I found that might be part of the problem.
I haven't test flown after this.

The other day I thought that I might check the firm/tightness of the Inductions tubes nuts at the cylinders.
Those was quite loose, if you ask me way to loose. Not that I could use my finders to loose them, but they were way to loose.
So I tighten all of them and this could absolutely be the source of problem.
If there is a induction leak it's not much, and since the nuts were looser than they should and with heat and vibrations there is a small chance that this is the problem.
Don't have high hopes that this is the problem, but glad I found it anyway.



If anyone has any other good ideas or thoughts...

[exM20K]

24 minutes ago, Fix said:

I have a GAMI spread of 0.5GPH more or less when I tested. (tested several times)

Can't get it running smooth as I want at higher altitudes. 4000->
I tried some things that Paul K suggested to me, but still it's not running smooth as I want.
Either my GAMI spread is to high or there are other things messing with me.

I'd try to start eliminating things:

1) induction leak: fly LOP at ambient MAP (eg: 10,000' at baro - 10").  If smooth LOP, you have an induction leak somewhere.

2) Spark: do a LOP mag test aloft. Is the problem isolated to one mag or bank of cylinders?

3) Fuel: any evidence of drips upstream of the fuel pump, including from the fuel selector, gasollator, and electric pump? 

When you did the soapy water thing on the induction, did you get *all* the lines such as the MAP sender, the line back to the fuel pump aneroid, the lines that pressurize the injectors?

I've been through a lot of these troubleshooting odysseys , as @kortopates can attest to, over 20 years  of Continental turbo ownership.

-dan

[Fix]

I double checked my timing.

 

TDC is spot on. 
With in 0.1 degrees.

SureFly is 0 degrees 
Within 0.1 degrees.

Slick Mag is 19.4 / 19.5 degree

So it must be within limits in general.
But is it better to have 20.5 degree than 19.4 degrees for LOP ?

 

 

[Pinecone]

Why are you running such a low MP?

Right now with a Slick and a SureFly (timed to 0), I cruise at 31.5 inches, 2300 RPM, 10.1GPH.   Depending on temps, that is with cowl flap closed to slightly open and CHTs under 380.  TIT is running about 1590.

Before the SureFly, I was at 29.5 inches.   Shop wants to retard the timing in the SureFly by 1 degree.

[Fix]

8 hours ago, Pinecone said:

Why are you running such a low MP?

I assume that 27.5 and 2500, 10.4GPH  more or less same at 29.5/2300/10.4?

I tried to fine tune with different MP/RPM but with no bigger success.
Maybe 2400rpm  and 26MP was slightly better.

Pretty sure I tested 29" / 2300 / 10.4 but if not mistaken my engine was too rough.

I think my problem right now is that I can't get LOP enough due to something.
And if I have higher MP then I get more LOP and more rough.

Will do some testing soon as I have aircraft back together.

[Fix]

23 hours ago, exM20K said:

I'd try to start eliminating things:

1) induction leak: fly LOP at ambient MAP (eg: 10,000' at baro - 10").  If smooth LOP, you have an induction leak somewhere.

2) Spark: do a LOP mag test aloft. Is the problem isolated to one mag or bank of cylinders?

3) Fuel: any evidence of drips upstream of the fuel pump, including from the fuel selector, gasollator, and electric pump? 

When you did the soapy water thing on the induction, did you get *all* the lines such as the MAP sender, the line back to the fuel pump aneroid, the lines that pressurize the injectors?

I've been through a lot of these troubleshooting odysseys , as @kortopates can attest to, over 20 years  of Continental turbo ownership.

-dan

1. Will test the 10" at 10000feet.

2. When I do a LOP mag test I can feel that it's rough, and when looking at engine data I can't see it. Or any "suspect" cylinder.
Might be that more than one cylinder is causing it.

3. Didn't check all of that. 
Will do it soon as I can.

Paul K suggested me to check Cylinder drains too.

[exM20K]

16 minutes ago, Fix said:

Will test the 10" at 10000feet

It would be more like 20” MAP. at 10,000, or surface pressure less an inch per thousand feet of altitude.  Good luck.

-dan

[Pinecone]

16 hours ago, Fix said:

I assume that 27.5 and 2500, 10.4GPH  more or less same at 29.5/2300/10.4?

I tried to fine tune with different MP/RPM but with no bigger success.
Maybe 2400rpm  and 26MP was slightly better.

Pretty sure I tested 29" / 2300 / 10.4 but if not mistaken my engine was too rough.

I think my problem right now is that I can't get LOP enough due to something.
And if I have higher MP then I get more LOP and more rough.

Will do some testing soon as I have aircraft back together.

At 29/23, 10.4 is not LOP on all cylinders in my engine.  At 29./23 I suspect I would have to be about 9.9 GPH to be LOP.

When you are LOP, fuel flow determines power.  So 10.4 GPH = 142.4 HP = 64.8% (for a -SB)

When LOP, lower RPM is better as the lean charge burns slower.  So if you are at a higher RPM, you are wasting some of that fuel burn.  Plus raising your TIT.

[Fix]

6 hours ago, Pinecone said:

At 29/23, 10.4 is not LOP on all cylinders in my engine.  At 29./23 I suspect I would have to be about 9.9 GPH to be LOP.

When you are LOP, fuel flow determines power.  So 10.4 GPH = 142.4 HP = 64.8% (for a -SB)

When LOP, lower RPM is better as the lean charge burns slower.  So if you are at a higher RPM, you are wasting some of that fuel burn.  Plus raising your TIT.

I hope that I can fly on Friday and do some testing.
Especially after finding all nuts not tighten as they should on the all air intake tubes.

[kortopates]

I hope that I can fly on Friday and do some testing.
Especially after finding all nuts not tighten as they should on the all air intake tubes.

When you find nuts on the intake tube that aren’t tight, the gaskets should really be replaced before tightening to ensure a proper seal after tightening. An old seal and perhaps damaged gasket isn’t likely to seal like a new one being compressed for the first time.

Good luck friday.


Sent from my iPhone using Tapatalk

[Ragsf15e]

On 7/8/2025 at 2:18 PM, Fix said:

I assume that 27.5 and 2500, 10.4GPH  more or less same at 29.5/2300/10.4?

I tried to fine tune with different MP/RPM but with no bigger success.
Maybe 2400rpm  and 26MP was slightly better.

Pretty sure I tested 29" / 2300 / 10.4 but if not mistaken my engine was too rough.

I think my problem right now is that I can't get LOP enough due to something.
And if I have higher MP then I get more LOP and more rough.

Will do some testing soon as I have aircraft back together.

I agree with @Pinecone. My 65% LOP setting is 2350/29” at 10.4gph.  26/2500 seems way too low manifold pressure at 10.4gph to be lop.  Are all of them really past peak there?
I just did this yesterday and it’s smooth on my engine (sb) with 2 mags, and gamis.  My spread is more like 0.2 though.

[Fix]

2 hours ago, Ragsf15e said:

I agree with @Pinecone. My 65% LOP setting is 2350/29” at 10.4gph.  26/2500 seems way too low manifold pressure at 10.4gph to be lop.  Are all of them really past peak there?
I just did this yesterday and it’s smooth on my engine (sb) with 2 mags, and gamis.  My spread is more like 0.2 though.

Will test 29/2350 10.4
This was also suggested by Kortopates.

I have a gami spread of 0.5 so that should be enough.

My best guess is that I have a small induction leak.

 

[Ragsf15e]

1 hour ago, Fix said:

Will test 29/2350 10.4
This was also suggested by Kortopates.

I have a gami spread of 0.5 so that should be enough.

My best guess is that I have a small induction leak.

 

Mine is only ~20 lop on the richest cylinder at that setting, so not a lot past peak (but plenty safe and cool at 65%).  That’s why I’m thinking your mp is too low for all to be past peak.

[Fix]

I'm double checking everything for the moment, found some things that might messing with me.

Checking the spark plug gap. Now all to 100% are 0.017-0.018"
Ohm measured all spark plugs, lowest 0.56K, most around 0.8k-1.5k and one at 4k.

First I found the non tightened nuts on all six air intake tubes, that absolutely can be the problem.

Today noticed that the inner nuts on exhaust wasn't tightened as the outer nuts.
Don't think this is a problem, more that they should be tightened and not good since it's the exhaust.

Also EGT Probe clamps wasn't that tightened as I would like them to be.
Don't think it affect my LOP but now they are tightened too.

2 cylinder drain nuts needed some love...


My engine has 6 new cylinder ~170h ago and and things that you need to remove is not tightened as it should afterwards.
Sloppy or not sloppy by the mechanic, but I'm starting to see that a pattern here.

Hopefully everything is ready tomorrow for a quick test flight.

 

Edited July 10 by Fix

[Pinecone]

Once you are at what you think is LOP, it is a simple test.  Lean the engine a bit more and the EGTs should all drop.  If any rise, you are not LOP on those cylinders.

[Ragsf15e]

18 hours ago, Pinecone said:

Once you are at what you think is LOP, it is a simple test.  Lean the engine a bit more and the EGTs should all drop.  If any rise, you are not LOP on those cylinders.

Or, if you’re at 10.4gph, go slightly richer very slowly and watch them all rise to see how far from peak you were at 10.4 gph.  Obviously don’t do this at higher power settings.  Either @Pinecones way or this will ensure you see all are lop at that setting is.

[Fix]

On 7/10/2025 at 7:41 AM, kortopates said:

When you find nuts on the intake tube that aren’t tight, the gaskets should really be replaced before tightening to ensure a proper seal after tightening. An old seal and perhaps damaged gasket isn’t likely to seal like a new one being compressed for the first time.

Since I suspected that Cyl 2 is the one that might have had an induction leak I removed the Air intake tube just to see if there was any damage to the gasket.
Gasket looked fine with any damage.

I did notice that one side of the gasket it was burnt/stick to the cylinder as expected, but on the other side it was loose and there was some signs of leakage.
Some slight discoloration on the cylinder, could be a illusion but gasket is now changed anyway.

[Fix]

On 7/8/2025 at 12:18 PM, Fix said:

I double checked my timing.

 

TDC is spot on. 
With in 0.1 degrees.

SureFly is 0 degrees 
Within 0.1 degrees.

Slick Mag is 19.4 / 19.5 degree

So it must be within limits in general.
But is it better to have 20.5 degree than 19.4 degrees for LOP ?

Slick Mag is re-timed to 20.1 degrees.

I hope to have it back together tomorrow, but weather next week is not good.

[Fix]

Quick update:

I need to do some more testing, but I think I made some progress.
Not there yet, but moving forward.

I suspect that my Slick Mag that has 415h has either some internal timing error or/and e-gap out of spec or something when it get hot.
I've sent the Mag for a 500h inspection, and looking forward to see what they find and then continue testing.