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03-31-2017, 07:42 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Let's focus...the point is that the sump is only one component in an assembly of components. Every component in the assembly contributes to variance, not just the sump. It's not reasonable to blame one piece alone, or claim perfection for any, including injectors.
Digital injector trim? Yep, no question, the absolute best new development in EAB fuel delivery. Regardless of where the variance comes from, it can be corrected from the cockpit, in moments.
Quote:
Originally Posted by Norcalrv7
It appears in this style sump, the intake tubes normally extend into the sump to form the bell mouth tubes. My intake tubes (made by Vetterman) end after the 0-ring seal.
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Tell us more about those Vetterman tubes. Got a photo?
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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03-31-2017, 08:02 AM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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If I recall correctly, there was an old thread about the bell mouth tubes being installed in the sump, and swedged into place---the guy was looking for the tool to redo the swedge---the internal tubes are effectively a part of the sump, and the tubes running to the heads are separate units.
It is not clear in Dan's image, but the way it looks is like the tube is one continuous piece from bell mouth to the head? Uses a thick wall seal that takes up the extra diameter needed for the bell end to pass through the sump casting?
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
Last edited by Mike S : 03-31-2017 at 08:09 AM.
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03-31-2017, 08:23 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by Mike S
It is not clear in Dan's image, but the way it looks is like the tube is one continuous piece from bell mouth to the head? Uses a thick wall seal that takes up the extra diameter needed for the bell end to pass through the sump casting?
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That's correct Mike.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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03-31-2017, 08:39 AM
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Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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Quote:
Originally Posted by DanH
Let's focus...the point is that the sump is only one component in an assembly of components. Every component in the assembly contributes to variance, not just the sump. It's not reasonable to blame one piece alone, or claim perfection for any, including injectors.
Digital injector trim? Yep, no question, the absolute best new development in EAB fuel delivery. Regardless of where the variance comes from, it can be corrected from the cockpit, in moments.
Tell us more about those Vetterman tubes. Got a photo?
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In the case of Dave Anders, he had the best stuff he could get on there- flow matched heads from Lycon and a Sky Dynamics intake which follows best automotive practice with a large plenum and tapered, near equal length runners. Even then, we saw variations of a few percent. Compare that to Clark Carrol's roughly 10% max variation. Most combinations are somewhere in between those two sample points. If we strip away each variable one at a time, it seems to me we are left with one conclusion- airflow imbalances exist in these engines to varying degrees due to intake design and port flow differences. We know which variables can contribute to imbalances but without more experimentation, it will be hard to zero in on what is the ultimate combination for a particular engine.
I'm keen to see what Mike's back to back comparisons show.
Last edited by rv6ejguy : 03-31-2017 at 08:47 AM.
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03-31-2017, 08:40 AM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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The 540 and 360 "tuned" sumps differ in that the six banger indeed has the tulips swaged into the sump, whereas the four has one piece tubes from head to tulip.
And yes, Dan, the sump is but one aspect of mixture distribution, but it can be a big one. These "tuned" sumps from Lycoming seem to be taylor made to take advantage of modern EFI and with their big plenum area and tuned runners actually predate the design of automotive EFI intake manifolds by decades.
I believe that Caleb is likely leaving power on the table with the truncated induction tubes he's running. I intend to test that theory with my airplane by experimenting with induction tube length as a means to find optimal VE, but again, I need to get the thing in the air first. That said, Lycoming probably got pretty close with their original design and cutting several inches off the tulips is most certainly going to change tuning. It likely shifts the optimal power range up and out of the normal RPM range we normally fly with.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
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Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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03-31-2017, 08:58 AM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Quote:
Originally Posted by rv6ejguy
If we strip away each variable one at a time, it seems to me we are left with one conclusion- airflow imbalances exist in these engines to varying degrees due to intake design and port flow differences.
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Your are forgetting about the scavenging or restriction that the exhaust system can create in each cylinder. Especially for a NA engine.
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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03-31-2017, 11:04 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by rv6ejguy
In the case of Dave Anders, he had the best stuff he could get on there- flow matched heads from Lycon and a Sky Dynamics intake.... Even then, we saw variations of a few percent.
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Interesting. You're saying even Lycon and Sky Dynamics can't can't really balance airflow. Probably true, and I'm not surprised. It's a dynamic system.
Re Clark's 10% variance; IIRC he was using an updraft sump, swapped it for an updraft sump from a different manufacturer, and recorded no change. Should we conclude that sumps make no contribution to variance?
Na. I'd still say it's a combination of random contributions from every component, and be pleased that you've developed a way to trim it easily.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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03-31-2017, 02:20 PM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Quote:
Originally Posted by DanH
...Re Clark's 10% variance; IIRC he was using an updraft sump, swapped it for an updraft sump from a different manufacturer, and recorded no change. Should we conclude that sumps make no contribution to variance? ...
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I think its reasonable to theorize that the manufacturer of a PMA'd sump will share the gross charactaristics of another, similar design. Most of those updraft sumps share the same choke points. The change to the "tuned" design however represents a significant departure in design. Its as compelling as the difference between the Ford 302 intake of 1970 vs 1990.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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03-31-2017, 04:19 PM
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Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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I think we've covered the many variables which can affect jug to jug airflow variations numerous times before, including exhaust. If you don't have equal length exhaust primaries, chances are that different jugs will "pipe in" and "pipe out" at different rpms leading to improved or degraded scavenging compared to the next jug.
I agree with Toobuilder, sumps with nearly the same design are likely to work similarly no matter what name is stamped on it.
I'd be interested to know how close the primary tube length is on Dave Anders RV4 are since he's got the other bases well covered.
The nice thing about having SDS on an engine is we can easily quantify AFR variations which give quicker results from experimentation.
BTW, auto racing engine designers understood and implemented tuned length intake systems at least 2 decades before Lycoming came up with any of their better designs. https://ixquick-proxy.com/do/spg/sho...cf5b9fcd00472f
Last edited by rv6ejguy : 03-31-2017 at 05:48 PM.
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03-31-2017, 05:30 PM
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Join Date: May 2006
Location: Pocahontas MS
Posts: 3,884
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Lyc had them that early?
https://en.wikipedia.org/wiki/Chrysler_B_engine
That was in production cars, and I'm pretty sure it wasn't the 1st. Racing, obviously much earlier than that.
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