Swift 94 fuel fails trial at UND

[Ibra]

I used to respect GAMI opinions on piston engines, however, they seem to have lost the track on this one? they mentioned detonation with UL94 that caused valve problems, I fail to see how this happens in 180hp NA engine like on the one in the Archer? even in their words unless you have 500F CHT  with monkey holding mixture you won't get ICP that high even on UL94...I think the only "scientific reason" why they come up with this handy and predictible explanation: well now they sell G100UL right, which obviously has higher Octane rating than UL94, so we expect to hear more and more about detonation problems anytime an alternative fuel is mentioned, as always, it seems once you throw some business interest, you start to get dumb engineers 

Lycoming are not in the bright spot neither they claim it's the additives, which honestly does not add up unless UL94 used by UND comes from dodgy batch...

In the meantime Pettersen STC for auto-fuel allow to run Pipers on EN228 where the only modifications are fuel lines and dual fuel pumps, I can't imagine auto-fuels having higher octane and less aromatics than Swift UL94? 

 

 

Edited April 18 by Ibra

[Ibra]

22 hours ago, Shadrach said:

Lycoming and Swift are both "interested parties" and both should be sidelined when it comes to analyzing this less than ideal trial.

I would add GAMI as interested party here as well, no need to seek their expertise: they will now claim that any alternative fuel (from a  competitor) on lower octane than their G100UL will cause detonation and bend cylinders all over the place...

Edited April 18 by Ibra

[EricJ]

13 minutes ago, Ibra said:

I used to respect GAMI opinions on piston engines, however, they seem to have lost the track on this one?

Braly (GAMI) is promoting G100UL, so it's probably wise to interpret everything he does in that context.   I met him and heard him speak here earlier this year, and he is not remotely unbiased in my opinion.   I now look at what they do in an entirely different light.   I suspect other solutions may turn out to be more marketable than G100UL.

[Hank]

Bah humbug.

Our politicians are mandating electric motors for everyone anyway, then during summer telling us to not run home AC or charge the electric vehicles they so badly want us to buy . . . .

It's all about control, same as G100UL vs Swift94 vs 100LL. We will likely all end up paying more to use the fuel pushed the hardest by the most politicians . . . . Whether it works in our engines or not, it will be the only thing whose sale is permitted. Control!

[Shadrach]

18 hours ago, Ibra said:

I would add GAMI as interested party here as well, no need to seek their expertise: they will now claim that any alternative fuel (from a  competitor) on lower octane than their G100UL will cause detonation and bend cylinders all over the place...

Perhaps I didn’t see it. but I don’t recall seeing George Braly say anything negative about 94UL in the beechtalk thread. If anything, he seemed critical of Lycoming attributing the recession to aromatics, which some perceived as a backhanded shot at G100UL, given its higher concentration of aromatics to maintain detonation margins.  Perhaps George made the comments on a different forum, but he appeared mindful of his wording in the BT thread, which is to say that that he seems skeptical of Lycoming‘s analysis without supporting data.

[Shadrach]

2 hours ago, Pinecone said:

There was a post in one of the threads, or maybe AVWEB from somebody at another school that had similar problems, even with 100LL (IIRC), and they traced it to the change in carbs.

I see the no LOP as a shotgun recommendation.  But there have been issues with people trying to run LOP, but not understanding things, so they richen slightly putting them into the red fin area.

George Braly stated he can duplicate the issues that UND had, and did so on his test stand with exactly the same issues.  There is some stuff going on behind the scenes before details will be released.

I saw the mention of the Texas flight school and the apparent correlation between carburetor type and valve recession... I just find it hard to reconcile multiple detonation events that are long enough and severe enough to cause valve seat damage without manifesting any other symptoms of detonation.

[Fly Boomer]

8 hours ago, Ibra said:

well now they sell G100UL

Nope.

[Ibra]

14 hours ago, Shadrach said:

If anything, he seemed critical of Lycoming attributing the recession to aromatics, which some perceived as a backhanded shot at G100UL, given its higher concentration of aromatics to maintain detonation margins. 

Yes Lycoming aromatics explanation is a shot against G100UL whereas the GAMI detonation explanation seems more like promotion of G100UL 

UL94 in those aircraft should not be a problem, assuming people keep CHT where they should...

14 hours ago, Shadrach said:

severe enough to cause valve seat damage without manifesting any other symptoms of detonation.

Yes this explanation sounds highly chirurgical and very unlikely

I expect some engine mismanagement to be at play with some false signals that comes from maintaining a school fleet, however, this UL94 fuel trial by UND is far from being crystal clear 

8 hours ago, Fly Boomer said:

Nope

They sell "G100UL right"

Edited April 19 by Ibra

[Shadrach]

19 hours ago, Ibra said:

I would add GAMI as interested party here as well, no need to seek their expertise: they will now claim that any alternative fuel (from a  competitor) on lower octane than their G100UL will cause detonation and bend cylinders all over the place...

Did I miss something in the BT thread or elsewhere? Where did GAMI/George Brady make these lower octane/detonation statements?  Given that many, many Archers have been running 91 octane mogas under the Peterson STC for many, many years, it seems unlikely that George would make such a statement.

[Pinecone]

20 hours ago, Shadrach said:

I saw the mention of the Texas flight school and the apparent correlation between carburetor type and valve recession... I just find it hard to reconcile multiple detonation events that are long enough and severe enough to cause valve seat damage without manifesting any other symptoms of detonation.

It doesn't take a medium to large detonation to cause micro welding, as I understand it.

So the ONLY symptom may be the valve recession

[Shadrach]

17 minutes ago, Pinecone said:

It doesn't take a medium to large detonation to cause micro welding, as I understand it.

So the ONLY symptom may be the valve recession

In all of my reading on detonation, valve to seat micro-welding and valve recession has never been listed as a symptom.  If you know of a publication or white paper that references these symptoms, I would appreciate a link.

[Pinecone]

Just going on comments in the various threads, but people with some knowledge and history.

As I said before, George has stated that he ran an engine on the test stand in the conditions he believed UND was using and was able to duplicate the issues.

[Ibra]

4 hours ago, Shadrach said:

Did I miss something in the BT thread or elsewhere? Where did GAMI/George Brady make these lower octane/detonation statements?

I only read it through another forum and here that between the lines GAMI believes it’s something to do with detonation (taken with pinch of salt)

George Braly did not make his coming out yet (I understand they are sharing data and finding with UND first), I hope there is more substance to it than octane/detonation in 94UL, go for G100UL and problem solved ! 

We will surely get to the end of this duel Swift vs GAMI soon…

Edited April 19 by Ibra

[Ibra]

Lycoming thinks nothing to see or new under the sun, maybe it's open-ended work in progress:

https://aviationweek.com/business-aviation/safety-ops-regulation/no-smoking-gun-found-und-engine-wear-issue

Between the lines they don't expect this to be a problem for other operators (any valve problems, real or seatingd, seems to be with UND)

Savvy also questioned "dry tappet clearance" way to monitor VSR by UND

https://www.savvyaviation.com/unleaded-avgas-cure-or-curse/

 

Edited Thursday at 08:29 PM by Ibra

[Pinecone]

Interesting, since, as I understand it, GAMI has been able to recreate the issue in their test cell.