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rvdave
Joined: 24 Jan 2009
Posts: 191
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 Posted: Sat May 23, 2020 6:41 am Post subject: Spark plugs and heat range |
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Is there a relationship between heat range of plugs and running lop and what would be the science behind that either way? I mean lop operation usually means throttling back(?) which reduces map which changes timing on most ei systems, does a colder or hotter plug make any difference to get to lower fuel burns lop?
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Dave Ford
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Tim Olson
Joined: 25 Jan 2007
Posts: 2878
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| Posted: Sat May 23, 2020 7:28 am Post subject: Spark plugs and heat range |
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I can't answer the spark plug heat range part of the question other than
to say that if you use fine wire plugs, you don't have a huge selection
of heat ranges, and I haven't found that I've needed anything different
than the normal plug I'd use anyway.
But, running LOP doesn't *usually* mean throttling back. It certainly
can, if you're trying to run LOP at low altitudes and want to honor
the 65%/75% power levels. However, I usually cruise at altitudes
over 8,000' when possible, preferring 9000-10,500 whenever it's
practical. Much of the time I'm not needing to power back at all
because the altitude took care of that MP reduction for me.
I'm sure that in an ideal world, a person would have a multi-heat-range
spark plug, because ideally you'd have a different one for takeoff
power at sea level, and cruising in the mid-teens. But in the real
world, you'd pick one that can handle the high power level of takeoff
in all situations, and compromise when it comes to cruise flight.
I just had all my plugs out this week and they're mostly clean, as
usual. The bottoms sometime get a little gunk in the bottom that needs
to be cleaned out, but the insulators generally are tan/faint grey
and never black, so they always look good to me. That's fine wire
though. I haven't run massive electrode plugs in years.
Tim
On 5/23/20 9:41 AM, rvdave wrote:
| Quote: |
Is there a relationship between heat range of plugs and running lop and what would be the science behind that either way? I mean lop operation usually means throttling back(?) which reduces map which changes timing on most ei systems, does a colder or hotter plug make any difference to get to lower fuel burns lop?
--------
Dave Ford
RV6 for sale
RV10 building
Cadillac, MI
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496465#496465
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rvdave
Joined: 24 Jan 2009
Posts: 191
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| Posted: Sat May 23, 2020 8:19 am Post subject: Re: Spark plugs and heat range |
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I’m running iridium plugs with dual ei and should have mentioned flying lower altitudes also. My light speed ei came with denso slant ground, have tried some different plugs but seem to get best performance with these, only problem is leaning to get best economy can’t get down to where I’d like to be and wondering if a different heat range would make a difference there?
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Dave Ford
Cadillac, MI |
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Kelly McMullen
Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ
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| Posted: Sat May 23, 2020 1:47 pm Post subject: Spark plugs and heat range |
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1. Leaning has very little to do with plug heat range. Primarily plug heat range is determined by compression ratio, and to lesser degree the amount of oil burned.
2. Once you get fully LOP, going further lean just reduces your power, does little to improve efficiency, which is why for normally aspirated engines LOP with 8.5-9.0 ratio; 14.95 times fuel flow in gph equals horsepower. So 11 gph is 165 hp, 12 is 180 and 13 is 195 or 75% in round numbers. If you have higher compression the multiplier goes up. For turboed engines the multiplier goes down as compression goes down....typically in the 13.7 range.
3. While iridium plugs of the auto variety are fine for electronic systems built for them, in the aviation plug variety they are mostly a waste of money, unless you can guarantee that no plug will ever be dropped, that the resistance will never change, so you can use them for a full engine TBO. Do you really want to invest over $1000 in a set of plugs? I had 8 used Champion fine wires that I put in my engine early on. More than half have gone way above the suggested 5K ohm value and had to be pitched. Of the new massive Champions that came with the engine, another 1/3 rd developed high resistance in under 200 hours. So when my supply of good used plugs is exhausted, it will be Tempest massives for me.
Kelly
| Quote: | | Sent from my TRS-80 Model 100 |
On Sat, May 23, 2020 at 9:26 AM rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:
| Quote: | --> RV10-List message posted by: "rvdave" <rv610dave(at)gmail.com (rv610dave(at)gmail.com)>
I’m running iridium plugs with dual ei and should have mentioned flying lower altitudes also. My light speed ei came with denso slant ground, have tried some different plugs but seem to get best performance with these, only problem is leaning to get best economy can’t get down to where I’d like to be and wondering if a different heat range would make a difference there?
--------
Dave Ford
RV6 for sale
RV10 building
Cadillac, MI
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496468#496468
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Kelly McMullen
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Tim Olson
Joined: 25 Jan 2007
Posts: 2878
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| Posted: Sat May 23, 2020 2:09 pm Post subject: Spark plugs and heat range |
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Good info Kelly, but I would like to point out that you said champion find wire plugs. Those haven’t had a good history from what I’ve heard. If you use Tempest fine wire, you may have better luck. I’ve used them over 1000 hours and they test out great every time. And, since I only need six of them, even at $85 apiece it isn’t really that big of a deal over the life of an engine, or even over 1/2 of the life of an engine. I do know that they are far easier to clean than the massive electrode plugs, and they seem to stay cleaner than those plugs did, don’t wear, and really have never required gapping. So lots of benefits. But again, these were autolite, now tempest. Less resistor issues with these plugs.
Tim
| Quote: | On May 23, 2020, at 4:53 PM, Kelly McMullen <apilot2(at)gmail.com> wrote:
1. Leaning has very little to do with plug heat range. Primarily plug heat range is determined by compression ratio, and to lesser degree the amount of oil burned.
2. Once you get fully LOP, going further lean just reduces your power, does little to improve efficiency, which is why for normally aspirated engines LOP with 8.5-9.0 ratio; 14.95 times fuel flow in gph equals horsepower. So 11 gph is 165 hp, 12 is 180 and 13 is 195 or 75% in round numbers. If you have higher compression the multiplier goes up. For turboed engines the multiplier goes down as compression goes down...typically in the 13.7 range.
3. While iridium plugs of the auto variety are fine for electronic systems built for them, in the aviation plug variety they are mostly a waste of money, unless you can guarantee that no plug will ever be dropped, that the resistance will never change, so you can use them for a full engine TBO. Do you really want to invest over $1000 in a set of plugs? I had 8 used Champion fine wires that I put in my engine early on. More than half have gone way above the suggested 5K ohm value and had to be pitched. Of the new massive Champions that came with the engine, another 1/3 rd developed high resistance in under 200 hours. So when my supply of good used plugs is exhausted, it will be Tempest massives for me.
Kelly
| Quote: | | Sent from my TRS-80 Model 100 |
On Sat, May 23, 2020 at 9:26 AM rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:
| Quote: | --> RV10-List message posted by: "rvdave" <rv610dave(at)gmail.com (rv610dave(at)gmail.com)>
I’m running iridium plugs with dual ei and should have mentioned flying lower altitudes also. My light speed ei came with denso slant ground, have tried some different plugs but seem to get best performance with these, only problem is leaning to get best economy can’t get down to where I’d like to be and wondering if a different heat range would make a difference there?
--------
Dave Ford
RV6 for sale
RV10 building
Cadillac, MI
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496468#496468
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Kelly McMullen
Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ
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| Posted: Sat May 23, 2020 2:21 pm Post subject: Spark plugs and heat range |
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Oh, I agree that the Tempest are a better plug, although Champion claims to have fixed their resistor issue, I don't see the benefit of paying 30 bucks more a plug for a name that no longer means quality.
I don't find massives hard to clean with a dental pick for lead balls. Fine wires are less work, for sure. I have seen the results of a dropped plug, and dropping one is kind of like dropping your wife's fine china.
| Quote: | | Sent from my TRS-80 Model 100 |
On Sat, May 23, 2020 at 3:13 PM Tim Olson <Tim(at)myrv10.com (Tim(at)myrv10.com)> wrote:
| Quote: | Good info Kelly, but I would like to point out that you said champion find wire plugs. Those haven’t had a good history from what I’ve heard. If you use Tempest fine wire, you may have better luck. I’ve used them over 1000 hours and they test out great every time. And, since I only need six of them, even at $85 apiece it isn’t really that big of a deal over the life of an engine, or even over 1/2 of the life of an engine. I do know that they are far easier to clean than the massive electrode plugs, and they seem to stay cleaner than those plugs did, don’t wear, and really have never required gapping. So lots of benefits. But again, these were autolite, now tempest. Less resistor issues with these plugs.
Tim
| Quote: | On May 23, 2020, at 4:53 PM, Kelly McMullen <apilot2(at)gmail.com (apilot2(at)gmail.com)> wrote:
1. Leaning has very little to do with plug heat range. Primarily plug heat range is determined by compression ratio, and to lesser degree the amount of oil burned.
2. Once you get fully LOP, going further lean just reduces your power, does little to improve efficiency, which is why for normally aspirated engines LOP with 8.5-9.0 ratio; 14.95 times fuel flow in gph equals horsepower. So 11 gph is 165 hp, 12 is 180 and 13 is 195 or 75% in round numbers. If you have higher compression the multiplier goes up. For turboed engines the multiplier goes down as compression goes down....typically in the 13.7 range.
3. While iridium plugs of the auto variety are fine for electronic systems built for them, in the aviation plug variety they are mostly a waste of money, unless you can guarantee that no plug will ever be dropped, that the resistance will never change, so you can use them for a full engine TBO. Do you really want to invest over $1000 in a set of plugs? I had 8 used Champion fine wires that I put in my engine early on. More than half have gone way above the suggested 5K ohm value and had to be pitched. Of the new massive Champions that came with the engine, another 1/3 rd developed high resistance in under 200 hours. So when my supply of good used plugs is exhausted, it will be Tempest massives for me.
Kelly
| Quote: | | Sent from my TRS-80 Model 100 |
On Sat, May 23, 2020 at 9:26 AM rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:
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Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD |
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Bob Turner
Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA
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| Posted: Sun May 24, 2020 8:59 am Post subject: Re: Spark plugs and heat range |
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The heat range spec is a measure of the plug’s thermal conductivity, tip to body. Too cold, deposits won’t burn off. Too hot risks pre-ignition. (Never run hotter than max allowed). Dave, if you can’t lean to as lean as you want, you probably need to adjust the cylinder mixtures to all be the same, by making very small changes in the injector sizes. You can buy them in 0.0005” increments.
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Bob Turner
RV-10 QB |
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Tim Olson
Joined: 25 Jan 2007
Posts: 2878
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| Posted: Sun May 24, 2020 9:58 am Post subject: Spark plugs and heat range |
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Also, make sure your injector nozzles all have the air bleed hole in the
proper location,
and I've found with a group of other people that especially on #2, that
air bleed being
directly in the airstream blast of the inlet can be affected a little.
It can help if there is
any sort of air dam that would disturb the air.
Definitely take Bob's suggestion though and make sure you tune the nozzles
properly.
Tim
On 5/24/2020 11:59 AM, Bob Turner wrote:
| Quote: |
The heat range spec is a measure of the plug’s thermal conductivity, tip to body. Too cold, deposits won’t burn off. Too hot risks pre-ignition. (Never run hotter than max allowed). Dave, if you can’t lean to as lean as you want, you probably need to adjust the cylinder mixtures to all be the same, by making very small changes in the injector sizes. You can buy them in 0.0005†increments.
--------
Bob Turner
RV-10 QB
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496476#496476
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rvdave
Joined: 24 Jan 2009
Posts: 191
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| Posted: Sun May 24, 2020 6:02 pm Post subject: Re: Spark plugs and heat range |
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| Tim Olson wrote: | Also, make sure your injector nozzles all have the air bleed hole in the
proper location,
and I've found with a group of other people that especially on #2, that
air bleed being
directly in the airstream blast of the inlet can be affected a little.
It can help if there is
any sort of air dam that would disturb the air.
Definitely take Bob's suggestion though and make sure you tune the nozz
Tim
|
[/quote]
I’ll have to take a look at the vent hole, not sure how that comes into play though. I have gotten my nozzles down to the closest I think I can get them but may play with them again. How does the vent hole not spew fuel since it is pressurized? Is the holder some type of check valve? Would like to learn more about that.
Dave
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Bob Turner
Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA
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| Posted: Sun May 24, 2020 6:20 pm Post subject: Re: Spark plugs and heat range |
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It’s Bernoulii’s principle, just like on top of the wing. There’s also an accessory wand for an air compressor, with a right angle port. Hook up vinyl tubing, it will suck liquid de-greaser and mix it with the air. Same thing here, it mixes just a bit of air with the fuel to help atomize it.
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Bob Turner
RV-10 QB |
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Kelly McMullen
Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ
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| Posted: Sun May 24, 2020 6:30 pm Post subject: Spark plugs and heat range |
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The injector body has a vent hole that lets air in through a screen, which mixes with the fuel coming through the inner restrictor of the nozzle.
The vent is supposed to be at atmospheric pressure, except on turbo-charged applications where additional tubing keeps it at manifold inlet pressure.
You can tell where the vent hole is by a flat marked with an A. It is supposed to point down, within a flat either way. I haven't had much luck aligning a couple of mine, because you are only allowed between 40-60 in/lb torque, which is about one flat of rotation.
I have stock restrictors (.028) on cyl 1,2,5,6, and .0275 on cyl 3 and 4. YMMV
Kelly
| Quote: | | Sent from my TRS-80 Model 100 |
On Sun, May 24, 2020 at 7:09 PM rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:
| Quote: | --> RV10-List message posted by: "rvdave" <rv610dave(at)gmail.com (rv610dave(at)gmail.com)>
Tim Olson wrote:
> Also, make sure your injector nozzles all have the air bleed hole in the
> proper location,
> and I've found with a group of other people that especially on #2, that
> air bleed being
> directly in the airstream blast of the inlet can be affected a little.
> It can help if there is
> any sort of air dam that would disturb the air.
>
> Definitely take Bob's suggestion though and make sure you tune the nozz
>
> Tim
>
>
>
|
I’ll have to take a look at the vent hole, not sure how that comes into play though. I have gotten my nozzles down to the closest I think I can get them but may play with them again. How does the vent hole not spew fuel since it is pressurized? Is the holder some type of check valve? Would like to learn more about that.
Dave
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496483#496483
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eferrer" target="_blank">http://forums.matronics.com
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errer" target="_blank">http://wiki.matronics.com
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rel="noreferrer" target="_blank">http://www.matronics.com/contribution
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[/quote]
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD |
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Tim Olson
Joined: 25 Jan 2007
Posts: 2878
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| Posted: Sun May 24, 2020 7:13 pm Post subject: Spark plugs and heat range |
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That was one of the theories as to why some people had trouble running LOP. If you had an intake that gave more manifold pressure than what your upper cowl area sees with air pressure, the air bleed won’t bleed air in as easily so you won’t get the atomization you want. For people with turbos they have the system mentioned previously. But it is just something to note that upper cowl plenum pressure is important to atomization since that vent needs to have air sucking in, to atomize fuel. Look at your injector next time it’s off and you’ll see a mesh shield on it. Now you know why it’s there...
Tim
| Quote: | On May 24, 2020, at 9:36 PM, Kelly McMullen <apilot2(at)gmail.com> wrote:
The injector body has a vent hole that lets air in through a screen, which mixes with the fuel coming through the inner restrictor of the nozzle.
The vent is supposed to be at atmospheric pressure, except on turbo-charged applications where additional tubing keeps it at manifold inlet pressure.
You can tell where the vent hole is by a flat marked with an A. It is supposed to point down, within a flat either way. I haven't had much luck aligning a couple of mine, because you are only allowed between 40-60 in/lb torque, which is about one flat of rotation.
I have stock restrictors (.028) on cyl 1,2,5,6, and .0275 on cyl 3 and 4. YMMV
Kelly
| Quote: | | Sent from my TRS-80 Model 100 |
On Sun, May 24, 2020 at 7:09 PM rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:
| Quote: | --> RV10-List message posted by: "rvdave" <rv610dave(at)gmail.com (rv610dave(at)gmail.com)>
Tim Olson wrote:
> Also, make sure your injector nozzles all have the air bleed hole in the
> proper location,
> and I've found with a group of other people that especially on #2, that
> air bleed being
> directly in the airstream blast of the inlet can be affected a little.
> It can help if there is
> any sort of air dam that would disturb the air.
>
> Definitely take Bob's suggestion though and make sure you tune the nozz
>
> Tim
>
>
>
|
I’ll have to take a look at the vent hole, not sure how that comes into play though. I have gotten my nozzles down to the closest I think I can get them but may play with them again. How does the vent hole not spew fuel since it is pressurized? Is the holder some type of check valve? Would like to learn more about that.
Dave
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496483#496483
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errer" target="_blank">http://wiki.matronics.com
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[/quote]
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rvdave
Joined: 24 Jan 2009
Posts: 191
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| Posted: Sun May 24, 2020 8:04 pm Post subject: Re: Spark plugs and heat range |
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Wondering how critical it is for the ‘A’ to be pointed ‘down’ since that in itself is relative to the slight angle of the injector body. Could it be that some injectors are receiving ram pressure instead of atmospheric pressure or am I just overthinking this? What did you mean by an air dam that could disturb the air?
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Dave Ford
Cadillac, MI |
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Tim Olson
Joined: 25 Jan 2007
Posts: 2878
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| Posted: Sun May 24, 2020 8:46 pm Post subject: Spark plugs and heat range |
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Just a guess but I’m guessing that down is just because if it were up, it could have air escaping easier when fuel isn’t actively flowing and/or it may not get the same siphon effect while flowing. Not sure.
Some could be getting ram pressure I think. The difference would be slight but if you picture the injector right in the air blast where the air hasn’t slowed much it could be different than other injectors that are more protected. The injector side being on the left as you face it from the rocker cover means the #2 is the one most directly facing the incoming cowl air.
When I talk about air dams I mean the ones right in front of the front two cylinder fins. The amount of trimming people do can vary so the effect on airflows in areas near it behind them could be slightly different from plane to plane too. I can’t remember who, but someone I talked to years ago experimented with shielding that injector a little from direct airflow and I think they saw a little improvement in how well they could run LOP. It’s many years ago now, so I forget the details.
Tim
| Quote: | On May 24, 2020, at 11:12 PM, rvdave <rv610dave(at)gmail.com> wrote:
Wondering how critical it is for the ‘A’ to be pointed ‘down’ since that in itself is relative to the slight angle of the injector body. Could it be that some injectors are receiving ram pressure instead of atmospheric pressure or am I just overthinking this? What did you mean by an air dam that could disturb the air?
--------
Dave Ford
Cadillac, MI
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496489#496489
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rvdave
Joined: 24 Jan 2009
Posts: 191
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| Posted: Mon May 25, 2020 12:33 am Post subject: Re: Spark plugs and heat range |
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Ok thanks for the info, I’ll be taking a closer look at this.
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Kelly McMullen
Joined: 16 Apr 2008
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Location: Sun Lakes AZ
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| Posted: Mon May 25, 2020 5:02 am Post subject: Spark plugs and heat range |
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If you don't cut down the air dam in front of the #2 cylinder, it blocks any direct ram air against the nozzle on #2. You want to preserve as much of that air dam as possible, to direct as much air as you can to #6 and the oil cooler, since # 6 is likely to be your hottest cylinder.
I can tell right away that spring is here when my oil temp starts moving above 180 in cruise.
| Quote: | | Sent from my TRS-80 Model 100 |
On Sun, May 24, 2020 at 9:09 PM rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:
| Quote: | --> RV10-List message posted by: "rvdave" <rv610dave(at)gmail.com (rv610dave(at)gmail.com)>
Wondering how critical it is for the ‘A’ to be pointed ‘down’ since that in itself is relative to the slight angle of the injector body. Could it be that some injectors are receiving ram pressure instead of atmospheric pressure or am I just overthinking this? What did you mean by an air dam that could disturb the air?
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Dave Ford
Cadillac, MI
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Vol88
Joined: 13 Jul 2019
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| Posted: Mon May 25, 2020 11:17 am Post subject: Re: Spark plugs and heat range |
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From Lycoming Service Instruction No. 1275C "Cleaning Fuel Injector Nozzles":
In normally aspirated engines where the nozzles, P/N LW18265 (see Figure 2), are installed horizontally, particular attention must be paid to the identification marks stamped on one of the hex flats on the nozzle body. This mark is located 180° from the air bleed hole and must appear in the lower side of the nozzle to assure that the airbleed hole is on top in order to reduce fuel bleeding from this opening just after shutdown. To ensure nozzle is correctly torqued, tighten the nozzle to 60 in.lbs. torque. Then continue to tighten until the letter or number stamped on the hex of the nozzle body points downward.
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Tim Olson
Joined: 25 Jan 2007
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| Posted: Mon May 25, 2020 11:29 am Post subject: Spark plugs and heat range |
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Good clarification. So the bleed hole is opposite of the identification
mark stamp,
thus when we put the mark down, the air bleed is up.
Tim
On 5/25/2020 2:17 PM, Vol88 wrote:
| Quote: |
>From Lycoming Service Instruction No. 1275C "Cleaning Fuel Injector Nozzles":
In normally aspirated engines where the nozzles, P/N LWÂ18265 (see Figure 2), are installed horizontally, particular attention must be paid to the identification marks stamped on one of the hex flats on the nozzle body. This mark is located 180° from the air bleed hole and must appear in the lower side of the nozzle to assure that the airÂbleed hole is on top in order to reduce fuel bleeding from this opening just after shutdown. To ensure nozzle is correctly torqued, tighten the nozzle to 60 in.Âlbs. torque. Then continue to tighten until the letter or number stamped on the hex of the nozzle body points downward.
Read this topic online here:
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Kelly McMullen
Joined: 16 Apr 2008
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Location: Sun Lakes AZ
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| Posted: Mon May 25, 2020 11:31 am Post subject: Spark plugs and heat range |
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I would exercise extreme care, because over-tightened nozzles are a bear to remove, and some experts believe can lead to head cracking in that area.
AirFlow performance gives a spec of 40 in/lbs to no tighter tan 60 in/lbs. You sure don't want to bugger one up by over-tightening.
| Quote: | | Sent from my TRS-80 Model 100 |
On Mon, May 25, 2020 at 12:22 PM Vol88 <tom(at)twmason.com (tom(at)twmason.com)> wrote:
| Quote: | --> RV10-List message posted by: "Vol88" <tom(at)twmason.com (tom(at)twmason.com)>
>From Lycoming Service Instruction No. 1275C "Cleaning Fuel Injector Nozzles":
In normally aspirated engines where the nozzles, P/N LW18265 (see Figure 2), are installed horizontally, particular attention must be paid to the identification marks stamped on one of the hex flats on the nozzle body. This mark is located 180° from the air bleed hole and must appear in the lower side of the nozzle to assure that the airbleed hole is on top in order to reduce fuel bleeding from this opening just after shutdown. To ensure nozzle is correctly torqued, tighten the nozzle to 60 in.lbs. torque. Then continue to tighten until the letter or number stamped on the hex of the nozzle body points downward.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496502#496502
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Bob Turner
Joined: 03 Jan 2009
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Location: Castro Valley, CA
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| Posted: Mon May 25, 2020 12:58 pm Post subject: Re: Spark plugs and heat range |
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Thank you, Vol88, for reminding me of the actual instructions. Note the arrow doesn't have to point exactly down: anywhere within a 180 deg of arc of "not up" will suffice to minimize fuel dripping out after shutdown. If you're concerned with ram air hitting the opening, you could point the arrow down and slightly forward.
Like Kelly, I didn't want to over torque these things. I stopped at 40 in-lbs if the arrow was down. If necessary I went to 60. If that didn't work, I removed the whole thing, cleaned the threads with a toothbrush and tried again. That usually worked!
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