VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.


Go Back   VAF Forums > Main > RV General Discussion/News
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #71  
Old 07-29-2021, 08:24 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 6,068
Default

On 9 to 1 PV engines, you can reduce timing to around 20 deg at high MAP, say above 25 inches. This seems to be pretty safe on 91 mogas and will lower the CHTs in the climb with minimal loss of power, perhaps 5-7hp on a 360.
__________________

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 449.1 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


Reply With Quote
  #72  
Old 07-30-2021, 04:17 AM
TXFlyGuy TXFlyGuy is offline
 
Join Date: May 2012
Location: Jazz Town, USA, TX
Posts: 539
Default

Quote:
Originally Posted by Clostermann View Post
Sorry to disappoint, but the FAA will not authorize any fuel for the entire fleet outside of PAFI. Braly's STCs are for 3 non-turbocharged engines (Lycoming's O-320, O-360, and IO-360) and the aircraft flown by the Embry-Riddle flight school (like the Cessna 172). He claims he will expand the STCs to other aircraft and engines using the AML-STC (approved model list) system, but will this include turbocharged engines or aircraft?

I suspect Braly's fuel will get even less traction in the marketplace than Swift's 94UL. Until an unleaded fuel is authorized for turbocharged aircraft, which represent 70-80% of AVGAS demand, deployment will be a gamble for any airport. According to GAMI's 2019 patent, G100UL contains ~30% aromatics plus 10-12% of an aromatic amine octane booster. Octane is below 100 and closer to 98 MON, if that. His "spec" minimum calls for 96 MON, barely above 94UL. A recipe for detonation in large turbos and a gamble for materials compatibility.

Until Braly shares his data with the OEMs and Industry, skepticism will remain. The 60 cent to a dollar upcharge may also dampen the enthusiasm.
This ^^^^^^^
__________________
Annual dues paid - 7-23-21
Future RV8 Owner
Reply With Quote
  #73  
Old 07-30-2021, 08:50 AM
Kuhtenia Kuhtenia is offline
 
Join Date: Jan 2018
Location: Galena, Ohio
Posts: 41
Default

Additional details from the AvFuel side of this - https://www.avfuel.com/Fuel/Alternat...tnQ6cZmFkQ3pHU
__________________
2021 dues paid
RV-6A Driver
Reply With Quote
  #74  
Old 07-30-2021, 09:14 AM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: Buena Park, California
Posts: 551
Default

Thanks for the link. Also quote from article regarding turbo engine testing

"What was the compression ratio, manifold pressure and the highest horsepower achieved during detonation testing that successfully passed a formal FAA 14 CFR Part 33.47 detonation test?

At the conclusion of the two days of detonation testing, GAMI elected to complete an optional test item from the FAA-approved test matrix.

That test item was to determine the maximum Brake Horsepower (BHP) at which the 8.7:1 CR IO-550 turbocharged test engine could be operated and continue to pass a standard Part 33.47 FAA detonation test.

With redline cylinder and induction air temperatures, the engine operated at 41.4” MP, 380 actual BHP (414 BHP when corrected to standard day conditions). We were unable to determine how much more additional HP could be obtained because the pressure relief “pop-off” valve on the induction system was limiting further increases in manifold pressure.
__________________
RV8 standard build: Empennage 99% completed
Wing -- Closed
Fuselage -- Canopy Done. Fiberglass 80%
Avionics Installation -- 90%
Firewall Forward -- Cowl completed. Baffle 90%
Electrical -- 90%

Donation paid through 2021
Reply With Quote
  #75  
Old 07-30-2021, 09:24 AM
skylor's Avatar
skylor skylor is offline
 
Join Date: Aug 2009
Location: Southern California
Posts: 1,000
Default ASTM Specification AvGas

Quote:
Originally Posted by Clostermann View Post
Sorry to disappoint, but the FAA will not authorize any fuel for the entire fleet outside of PAFI. Braly's STCs are for 3 non-turbocharged engines (Lycoming's O-320, O-360, and IO-360) and the aircraft flown by the Embry-Riddle flight school (like the Cessna 172). He claims he will expand the STCs to other aircraft and engines using the AML-STC (approved model list) system, but will this include turbocharged engines or aircraft?

I suspect Braly's fuel will get even less traction in the marketplace than Swift's 94UL. Until an unleaded fuel is authorized for turbocharged aircraft, which represent 70-80% of AVGAS demand, deployment will be a gamble for any airport. According to GAMI's 2019 patent, G100UL contains ~30% aromatics plus 10-12% of an aromatic amine octane booster. Octane is below 100 and closer to 98 MON, if that. His "spec" minimum calls for 96 MON, barely above 94UL. A recipe for detonation in large turbos and a gamble for materials compatibility.

Until Braly shares his data with the OEMs and Industry, skepticism will remain. The 60 cent to a dollar upcharge may also dampen the enthusiasm.
Early on in the GAMI UL100 development, I recall that George Braly stated that they tested 100LL AvGas from various sources and it did not meet the ASTM specifications that it was supposed to meet. George held that the FAA should reduce some of the requirements for unleaded fuels because 100LL didn't even meet those specifications. I think this is key to the suitability of UL100 in spite of it falling a little short of some requirements.

Skylor
Reply With Quote
  #76  
Old 07-30-2021, 10:19 AM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 6,068
Default

Quote:
Originally Posted by skylor View Post
Early on in the GAMI UL100 development, I recall that George Braly stated that they tested 100LL AvGas from various sources and it did not meet the ASTM specifications that it was supposed to meet. George held that the FAA should reduce some of the requirements for unleaded fuels because 100LL didn't even meet those specifications. I think this is key to the suitability of UL100 in spite of it falling a little short of some requirements.

Skylor
I had read somewhere that most of the FAA concerns seemed to be about specific gravity and other factors about the Swift and GAMI fuels. Both had passed detonation testing on turbocharged engines at Purdue and GAMI's facility as far as I am aware.
__________________

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 449.1 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


Reply With Quote
  #77  
Old 07-30-2021, 09:30 PM
David Z David Z is offline
 
Join Date: Aug 2010
Location: Thunder Bay Ontario
Posts: 739
Default

The (L)TIO-540-J2BD has the manifold pressure redline at 49", so should be expected to operate there with no problems. Yes, 45" is normal, but 49" is allowed. Compression ratio is also quite low, can't recall the exact number. That certainly helps with detonation margin.
__________________
RV8
Empennage Passed Pre-close Inspection
Wings mostly done
Fuselage at the "porcupine stage"
83126
Dash 8 day job is financing the RV8
Donation till September 2022

Last edited by David Z : 07-31-2021 at 10:09 AM. Reason: Type-o. Recline/redline
Reply With Quote
  #78  
Old 07-31-2021, 06:17 AM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: Buena Park, California
Posts: 551
Default

I just watched the AOPA weekly broadcast and GAMI initial goal is to STC its fuel for all the GA training fleet, and that includes all the C172s and other smaller trainers. I guess the twins with turbos will have to wait a bit longer.
__________________
RV8 standard build: Empennage 99% completed
Wing -- Closed
Fuselage -- Canopy Done. Fiberglass 80%
Avionics Installation -- 90%
Firewall Forward -- Cowl completed. Baffle 90%
Electrical -- 90%

Donation paid through 2021

Last edited by PhatRV : 07-31-2021 at 06:54 AM.
Reply With Quote
  #79  
Old 08-14-2021, 08:21 AM
Freemasm Freemasm is offline
 
Join Date: Nov 2017
Location: Orlando
Posts: 448
Default

Links taken from a thread in Mooneyspace. Not arguing any merits but just sayin’ this ain’t over (until it’s over)

https://www.casa.gov.au/file/203356/...token=5kUK1-c3

https://austhia.com/PDfs/AHIA-piston...ity-report.pdf
Reply With Quote
  #80  
Old 08-20-2021, 08:44 PM
PaulMillner PaulMillner is offline
 
Join Date: May 2021
Location: Berkeley
Posts: 8
Default Unleaded Avgas Update

I've been asked by a participant here to update and share this summary from late last year.

Avgas December 2020 Update – updated - Part 1

Quote:
It’s been a few years, what is going on with no lead aviation gas? I thought it was down to one or two. With the new administration on fossil fuel, the EPA will probably do more nudge to force a transition to an unleaded fuel.

Sure, let’s summarize what’s been going on, and address some of the questions that have been posed over the last little while. First the disclaimer, I was an engineer at Chevron for 38 years. The last decade plus, I was involved in unleaded avgas development, until Chevron became so frustrated at the FAA’s ignoring science that Chevron walked away, as eventually did all of the major energy companies. I’ve provided some small consulting to Swift and GAMI since then, but am not privy to their confidential stuff, and am not representing either of them in expressing my observations on the passing scene.
While the FAA’s PAFI (Piston Aviation Fuels Initiative) is stuck, because ignoring science is a bad approach, there are four companies working the issue. In diminishing order of successful probability, IMHO: GAMI, Phillips/Afton, Lyondell/VP-Racing, and Swift. [Shell walked away in January 2021.] Let’s look at each approach.
GAMI has been working on this issue since 2010, and they do observe the science. Their formulation and additives have evolved impressively. The FAA has streamlined (!) the approval process, and GAMI was granded limited approval just before Oshkosh last month. That will probably result in fleet trials, maybe at a flight school or two. The FAA and GAMI have agreed on a final testing program, which will lead to fleet-wide approval by June next year, GAMI says.
Phillips came to this game late, announcing at Oshkosh 2019, and giving a technical seminar. They plan to replace the lead with Methylcyclopentadienyl Manganese Tricarbonyl (MMT). Manganese is much less toxic than lead, although when MMT was used in mogas, principally in Canada, there were issues with spark plug fouling. Phillips thinks they know how to devise a scavenger for the aviation application that will spare our expensive plugs… I’m guessing a molecule that was considered too expensive to be competitive in mogas, but avgas’ higher margins make it feasible. Phillips website says 2025 or 2026 completion.
Lyondell (the former ARCO Chemical) is working with VP-Racing on a conventional avgas without lead, achieving the necessary antiknock property via ETBE (ethyl tert butyl ether), MMT, and methanol. Each of those additives presents challenges, so there are many moving parts to making this work.
Swift seems to be struggling a bit, but the underlying science of their R100UL should be workable. I’m not sure they have the resources to get there. Swift is selling an interim 94UL fuel that they originally planned to discontinue when the 100UL is available. Swift nows says they might continue manufacturing both fuels, which is surprising. Folks are concerned that the supply logistics on the 94UL Swift fuel seem sketchy, and worry what that might imply about Swift’s viability. It may however only be a learning curve experience for Swift. I wish them well.
Shell was the primary contender in the FAA’s PAFI, and that effort was not successful, even after the FAA changed the rules to accommodate them, versus being left with no players after Swift withdrew from PAFI. It’s important to note that it’s NOT the Shell refining company that’s pushing this effort. Instead, it’s kind of a speculative effort by their Global Solutions company, which was spun off a few years back. They’re hoping to develop a salable solution, rather than developing a solution for the Shell corporation. After the problems with their fuel removing paint from wings and their engine endurance testing failing, Shell has said they’re sitting back, awaiting a stronger business case for their fuel to appear.
Quote:
It’s not the politics that has held up this change, it’s that pesky physics thing. It’s got to support the high compression engines which burn most of the 100LL

It’s a combination of factors… The FAA has to follow the scientific method, but as a federal agency, it is an inherently political animal. So it tends to be a combination of confounding factors.
Quote:
Maybe they need to reduce the compression in those engines. Not a big deal to change pistons. Then, unleaded mogas can offer a real solution.

The certification burden is enormous for the fleet… each engine/airframe combination would have to be recertified, with new performance tables compiled from flight testing. This is a very expensive effort… and not one popular with aircraft owners, as it will result in reduced gross weight and performance. No one is excited about spending the money to make that happen.
Quote:
It’s been 25 years since EPA ban on lead in fuel, just how long do you think Kerry and the new administration are going to wait.

You overlook that the EPA and FAA duked this one out in Federal Court during the W administration (the White House didn’t want to take the heat, I guess). The SCOTUS decided that the FAA is in charge of avgas regulation, so the EPA sits by waiting for the FAA to do their thing. The EPA could make a finding of endangerment, that might adversely motivate the current producers of leaded avgas. But, that didn’t happen under 44, and I think Biden et al might be more interested in observing Supreme Court rulings in letter and spirit than running roughshod over them.
Quote:
Will this lower the price for avgas?

It’s hard to say. The unleaded fuel will cost slightly more to make. On the optimistic side, since high-liability lead facilities aren’t required, any number of additional blenders might choose to enter the marketplace, introducing more competition than currently exists. My guess is avgas prices will eventually be roughly the same: at wholesale, avgas sells at 80 cents to $1/gallon more than premium unleaded.
Quote:
Mogas isn’t really a replacement. The vapor pressure is too high. A good chunk of the fleet would have to be retrofitted with in tank boost pumps to keep airframe fuel lines from forming vapors.

There’s a number of issues with mogas, although in the summertime mogas vapor pressure and avgas vapor pressure are nowadays about the same. Ethanol content and octane are the big show stoppers.
Quote:
The mogas you buy at the Texaco station doesn’t have the QC/QA that aviation fuels do.

That’s true.
Quote:
Probably would also need to go to electronic ignition with knock sensors and variable timing… more money.

There are technical problems with knock sensors in aviation engines; lots of the aerodynamic noise looks like knock to conventional sensors, which is why GAMI tried developing fiberoptic based sensors. But none of that is certified and ready for prime time. And you’re right about more money.
Quote:
Unleaded avgas can be made to equal the current 100LL… I do not know what the holdup is.

There were subtleties when one starts looking at the entire fleet, and then there’s the certification process itself. The FAA has very limited experience in certifying fuels, and has made missteps.
Quote:
Environmental benefit? The amount of aviation fuel used is microscopic

Perhaps, but there’s no safe lead exposure… from molecule one, the best we understand it, children exposed to lead suffer from reduced IQ. Today, 1/3 of the lead entering the ecosystem is from our “microscopic” avgas use, so it needs to go away as a matter of social policy. There are studies implicating the one remaining tetra-ethyl lead plant in Liverpool, England in adverse impact on children down wind. How does one stand tall about that?
Quote:
leaded gas supposedly helps lubricates the valves, but I think that can be addressed in other ways.

Leaded gas is actually bad for the valves. There’s scholarship and industry papers explaining that the valve problems we saw when lead was phased out of mogas came from the drop in octane, not the lack of lead; and the FAA has done at least one validating study on aircraft.
Quote:
Ethanol contamination is a ridiculously easy check. Just add 10% water, shake, & see if the apparent water volume increases.

So, what do you do if your airport tank is full of mogas-derived avgas that flunks that test? It’s not pretty. It needs to be controlled for upstream, not remedied after the fact.
Quote:
High temperature and high humidity reduce horsepower now, yet we accept it. Maybe just reduce the max gross weight?

But the impact of temperature and humidity can be calculated in an FAA-approved manner, per the POH and the AIM. To reduce horsepower will require a similar certification effort with flight testing, and that’s expensive.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 04:34 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.