LA 46 Fuel Volume

[Kim Mortimore]

LA 46 users, how much fuel does it take to get you thru the pattern?  The range seems to be fairly wide among my local home boys.   

Thanks

[Bill Barber]

   Kim , my LA .46 in my slightly overweight Cardinal  uses 4 1/4 ounces to get thru a pattern .
  Bill

[RandySmith]

LA 46 users, how much fuel does it take to get you thru the pattern?  The range seems to be fairly wide among my local home boys.   

Thanks

Most people use a 5 ounce tank and get by with that or under

Randy

[Bootlegger]

            I am running 5 oz tanks on all my 46's using 10% nitro, 22%% oil half & half, in the heat add about 2-3 oz  castor oil.     

[Randy Powell]

We have guys here getting through a pattern on 3.5oz! But that's really Pat Johnston. That guy gets the best fuel economy of anyone I know. Even when you are using the exact same setup he is, you can count on an extra 1/2 ounce or so. Maybe it's the 5% nitro fuel he uses.   

I'd say go with a 5oz tank, always easy to take some fuel out; very hard to put more in than the tank will carry.

[Kim Mortimore]

We have guys here getting through a pattern on 3.5oz! But that's really Pat Johnston. That guy gets the best fuel economy of anyone I know. Even when you are using the exact same setup he is, you can count on an extra 1/2 ounce or so. Maybe it's the 5% nitro fuel he uses......

One guy getting by with a small amount of fuel in this area is using an OS25 venturi and 3 head shims on a 40 oz. plane.

[Steve Helmick]

My experience says a 5 oz tank is the safe bet for the .46LA. But it can vary a lot, depending on your setup...muffler type, prop, venturi/spraybar size, and brand of fuel, as well as nitro and oil percentages. Lots of variables. What works for you is the best setup to use, I betcha.  Steve

[Neil Rogers]

We run our LA46s on Sig Champion 5% using an APC 11x5 prop, Super Tigre nva, and a tongue muffler. We use Sullivan 4 oz rectangular tanks and can often overrun if the tank is filled. 3 3/4 oz is all we normally need.  This combination has worked nicely on airplanes up to 600 sq. in.

Neil Rogers
Edmonton

[Bill Little]

Man, there are SO MANY variables that go into this.   Prop, RPM, Nitro %, environment, and???

One way to get longer runs is to drop the nitro.  5% is actually plenty for most people in most conditions.  10% if it really gets hot!  Not enough ponies?  Bigger engine needed.....  running a "wet 2" versus a "solid 4" versus a 4-2 will all be different.  How long you actually take to fly the pattern also varies!  How long do you fly "after" the cloverleaf?  I like to have exactly enough fuel to get through the cloverleaf, and then land.  I can't stand flying laps after the pattern is over.  I use less than some of my buddies because of this.  Anything over 6:30 is way too long for me, most of the time.

Best way to find out the amount is to get the plane flying the way you want it to fly, fill the tank completely, then time the flight from "start" to "stop".  Then measure how much you need to take OUT.  Measuring how much you put IN the tank can be problematic....  measuring how much you take OUT of a full tank is the same every time.

Big Bear

[FLOYD CARTER]

My LA 46 has been flying the pattern on 3.75 oz of SIG 10-10-10.  I changed the prop to a 3-blade Master Airscrew cut down to 11-6.  Line tension was better, but ran out of fuel!  Second flight with 5 oz fuel, and just barely made the pattern.

The new prop pulled much better, so the engine was more loaded and developing more HP.  I assume that more HP=more fuel. 

So fuel load depends on thrust generated, which equates to fuel required. etc., etc.

So, what numbers you get on the test bench have little meaning when you fly!

Floyd

[Randy Powell]

Just as a followup. I talked to Pat and he is experimenting with a new set up for his LA46. .256 venturi and ST type NVA. His standard 13.25 x 3.75 prop and is using less than 3 ounces of fuel. Sheesh.

[Bill Little]

Just as a followup. I talked to Pat and he is experimenting with a new set up for his LA46. .256 venturi and ST type NVA. His standard 13.25 x 3.75 prop and is using less than 3 ounces of fuel. Sheesh.

Hi Randy,

I think you meant "12.25" x 3.75.  

Big Bear

[Dennis Moritz]

I have a 38 ounce Tanger that was kit bashed to look like a JD Falcon. A nice fellow made it and sold it to me cheap. I run an LA46 on it, set ridiculously rich. Barely breaks when doing the tricks. 6 second laps. But the plane stays out there, pulls up and over and does all the figures. A pattern runs nearly all the fuel out of a six ounce clunk.

[Kim Mortimore]

I have a 38 ounce Tanger that was kit bashed to look like a JD Falcon. A nice fellow made it and sold it to me cheap. I run an LA46 on it, set ridiculously rich. Barely breaks when doing the tricks. 6 second laps. But the plane stays out there, pulls up and over and does all the figures. A pattern runs nearly all the fuel out of a six ounce clunk.

Dennis,
Interesting.  What prop are you using?
Thanks.

[Dennis Moritz]

12.25x3.75 APC. Balanced and stuck on the front. Not cut down at all. Dan Banjok was absolutely indignant when he timed the laps at Muncie. Said the speed was way too comfortable. He said that effective stunt flights need an edge, an element of fear.   The conditions were ideal when I flew at the NATs. Even in a moderate breeze tho, the plane seems to work flying at that speed. I think the light weight of the plane, plus the abundance of reserve power, allows me to fly this plane that slow.

[Steve Fitton]

12.25x3.75 APC. Balanced and stuck on the front. Not cut down at all. Dan Banjok was absolutely indignant when he timed the laps at Muncie. Said the speed was way too comfortable. He said that effective stunt flights need an edge, an element of fear.   The conditions were ideal when I flew at the NATs. Even in a moderate breeze tho, the plane seems to work flying at that speed. I think the light weight of the plane, plus the abundance of reserve power, allows me to fly this plane that slow.

I watched it go through the pattern too that day.  A couple of tenths faster would make it WAY easier to put in a nice pattern...

[Kim Mortimore]

12.25x3.75 APC. Balanced and stuck on the front. Not cut down at all. Dan Banjok was absolutely indignant when he timed the laps at Muncie. Said the speed was way too comfortable. He said that effective stunt flights need an edge, an element of fear.  The conditions were ideal when I flew at the NATs. Even in a moderate breeze tho, the plane seems to work flying at that speed. I think the light weight of the plane, plus the abundance of reserve power, allows me to fly this plane that slow.

Cool.  Indignifying our friends is half the fun.   
LA46 is the bee's knees.  Our club has been trying them on planes in that weight range with great results too.  Love the sound of that deep 4-stroke and the nice smoke trail.   

[Pat Johnston]

Might as well spill all the beans.  Here is what I wrote on a thread on the Magnum 36:
"If a person wants the Holy Grail of engines, under $100, buy an LA46-S and either plug one whole side of the venturi with JB Weld, silly-cone, balsa wood, etc or install a much smaller venturi, which gets in the area of .012 to .014 square inches of choke area.  The combination of a ST NVA and LA25 venturi (.257") gets you to the .012 figure.  My last flight with this combination was swinging a 11.5 X 4W APC in a crackling 2-cycle yeilding a full stunt run with about 6-8 laps after the clover leaf on 2 1/2 ounces of fuel.  Let that sink in.  The run was possibly the most consistent from the start to the finish of anything I've ever expienced.  The break to a solid 2-cycle started at the very beginning of the maneuver and immediately fell back to the level flight setting.  Can you see why I call this the Holy Grail of engines?  Less than $100, 2 1/2 ounces of fuel, swings a substantial prop, and a spectacular run.
How can that get any better?"

Really, this is an amazing setup.  The stock venturi and NVA may run OK, but it has twice the choke area at about .024 square inches.  It is no wonder why people use 4.5 to 5.0+ ounces of fuel.  Up until lately, my setup for the 46 was a .275" venturi and ST NVA yeilding about .0165 square inches and using 3.625 ounces of fuel.  As you can see, dropping the venturi choke area down makes a dramatic difference in fuel consumption.  Interestingly enough, the engine still puts out power like a 40 on steroids.  I use only Power Master 5% fuel with 8 ounces of castor added.  Bottom line is if you are running out of fuel early, change the venturi.
Pat Johnston
Fan of the LA46
Skunk Works

[Bill Little]

(snip)Really, this is an amazing setup.  The stock venturi and NVA may run OK, but it has twice the choke area at about .024 square inches.  It is no wonder why people use 4.5 to 5.0+ ounces of fuel.  Up until lately, my setup for the 46 was a .275" venturi and ST NVA yeilding about .0165 square inches and using 3.625 ounces of fuel.  As you can see, dropping the venturi choke area down makes a dramatic difference in fuel consumption.  Interestingly enough, the engine still puts out power like a 40 on steroids.  I use only Power Master 5% fuel with 8 ounces of castor added.  Bottom line is if you are running out of fuel early, change the venturi.
Pat Johnston
Fan of the LA46
Skunk Works

Hi Pat,

Thanks for the posts! 

Two things I have missed in the posts so far on this set up is which airplane you used (P-40ARF??) and how much it WEIGHS. 

I really can appreciate using less fuel as long as no damage is done, and enough power is still available.  From your posts on this set up, it looks like both situations are good to go.

BTW:  What does a 6mm venturi compare to in "American terms"?

Thanks!
Big Bear

[Pat Johnston]

Bill,
Here are more spec's.  The plane is my RSM P40K, the prototype for the kit.  Weighs 45.5 ounces.  Great flyer, BTW.  The overall charactoristics are very similar to the Brodak P40B.  Imagine that!  I designed them both.  There is one thing a little different on the LA46, which is the combustion chamber is opened up a little.  This saves needing to add head shims.  According to Lew Woolard, opening up the CC volume is a little better than adding head shims because the glow plug distance to the top of the piston is not altered.  Makes good sense.  The engine does have a metal backplate, but that is more for consistency than anything else.  In comparing my engines to Mark Scarborough's we could see little difference.  Not sure just how it would affect the smaller venturi setup.
To your 6mm venturi question.  That is .236", which in unison with an OS NVA (3.5mm) would yeild the same .012 sq. in. choke area.  If you can come up with a 6mm for the OS NVA, that would be good.
Having an engine swinging 11.5" of wide blade prop at the correct lap times is pretty magical.  I would like to try a .260", .265", and .270" venturi to see just how that works.  I suspect that the .260 or .265 may be the best overall.  I forgot to mention that the engine has the very usual trait of richening up at the end of the first lap.  Very common with a conservative choke area.  I found that the needle had to be turned in about a quarter of a turn when the 2-4 break point was found.  This will creat a condition which will be a learning experience, then no big deal.
Pat

[Bill Little]

Hi Pat,

I actually have Delrin venturi in both  6.5 and 7 mm for the LA .46.  Is the 3.5mm OS NVA teh one used as "stock" now?  Or the old thicker spray bar one?  I have both, just wondering.  I also have one of Eric's ST (style) NVA for the OS .46 and a few of Randy's NVA used in the PA's. 

Thanks!  it sounds like a real good set up. A 45.5 to 46 oz plane is heavy enough for me short of "full blown stunters". And the planes I have scheduled for the .46LA should all fall in that range, or below.  Hopefully anyway!

I'm going to put a LA.46 in the RM 576.

Now, got the same trick for a ST G.51? (gonna have to use one this year, as you know!) 

Thanks, again
Bill

[Pat Johnston]

Bill,
The 6.5mm unit equals the LA25 venturi (.257") while the 7mm is .276", which is functionally what I have been running for the last three years.  Anywhere from 6.5 to 7mm with a ST NVA (4mm) is ideal in my opinion. 
The OS NVA's are currently 3.5mm.  As an interest for converting the venturi/NVA equivalents, just add or subtract .020" to the venturi size, depending on which NVA is used.
I believe you will find that the ST51 through the throat where the stock NVA is mounted measures .285" (7.25mm).  Be aware that this is a true venturi design and if the NVA is lowered to bisect the middle of the mounting boss (recommended) the venturi opens up there and allows for a larger airflow.  I think it would be interesting to plug the venturi with aluminum tubing and JB Weld and ream out the hole to somewhere in the .270" to .275" range.  A person might be surprised just how efficient the ST51 can be.  With a .282" hole in mine, I am swinging a 13" prop and the engine is happy.  Have two 51's and one eats 4 ounces of fuel, the other 4.5 ounces.  Odd.  Must have one which is a little more efficient.  Should check the bearings for alignment.
Hope this rambling helps.
Pat

[Bill Little]

HI Pat,

Thanks for the further info.  I still haven't run a truly "stock" G.51.  The one in my USA-1 (54 oz) and earlier SV 11 (64 oz.) ran about 5 to 5 1/2 oz. of 5% nitro fuel.  Never a problem for power! LOL!!  I mostly used Rev Up 12-5 govt. surplus props, craved on a bit.  When I sold the engine, with the USA-1, I had an Eather 11 5/8" 3blade pitched to about 4-3/4 at station 10.  Never knew what the venturi size was, it was whatever Tom put in it! LOL!!

[Frank Imbriaco]

Bill,
Here are more spec's.  The plane is my RSM P40K, the prototype for the kit.  Weighs 45.5 ounces.  Great flyer, BTW.  The overall charactoristics are very similar to the Brodak P40B.  Imagine that!  I designed them both.  There is one thing a little different on the LA46, which is the combustion chamber is opened up a little.  This saves needing to add head shims.  According to Lew Woolard, opening up the CC volume is a little better than adding head shims because the glow plug distance to the top of the piston is not altered.  Makes good sense.  The engine does have a metal backplate, but that is more for consistency than anything else.  In comparing my engines to Mark Scarborough's we could see little difference.  Not sure just how it would affect the smaller venturi setup.
To your 6mm venturi question.  That is .236", which in unison with an OS NVA (3.5mm) would yeild the same .012 sq. in. choke area.  If you can come up with a 6mm for the OS NVA, that would be good.
Having an engine swinging 11.5" of wide blade prop at the correct lap times is pretty magical.  I would like to try a .260", .265", and .270" venturi to see just how that works.  I suspect that the .260 or .265 may be the best overall.  I forgot to mention that the engine has the very usual trait of richening up at the end of the first lap.  Very common with a conservative choke area.  I found that the needle had to be turned in about a quarter of a turn when the 2-4 break point was found.  This will creat a condition which will be a learning experience, then no big deal.
Pat

Hi Pat:
Thanks for  sharing  your setup. I've got a new  OS 46 LAs. I checked the venturi specs and discovered  that the OS 25 unit is 8mm O.D.
and the 46 unit is 10mm o.d.; as per the OS website. What do you do about the the undersized situation ?
As far as replacing the NVA assembly with the ST unit, can you supply a stock #?
Also, do you modify the engine to be non-remote  NVA or keep it as is ?
Thanks,
Frank

[Pat Johnston]

Frank,
Can you be talking about an old OS 25S series as opposed to the FP/LA Series?  The 25 FP/LA units are distinctly 10mm (.394") bosses.  I do think that the older 35S and likely 25S units were 8mm mountings.  At least the beauty of the metric oriented engines were that the venturis were in even metric measurements, ie 8, 10, 12, 14.  I think the Magnum and some Stalker engines use the 12mm while the ST60 uses the 14mm boss.  The FP/LA engines from the 20 to the 46 use the 10mm venturis.
Pat

[Frank Imbriaco]

Pat,

Perhaps there  is an error with theTower Hobbies tech notes  re: venturi o.d. for  the LA 25s. I also referrred to the OS site and it says the same as Tower. I believe you, but to be sure, do you have the OS  P.N. ?

Also, mind if I ask again about the ST. NVA and whether you keep it remote as designed or set it up the traditional way through the venturi ? I saw that design on the RSM Distribution site for the LA 46s and just want to be sure.

Thanks,

Frank

[Bill Little]

Hi Frank

Not Pat J (obviously! LOL!!) but I would suggest moving the NVA to the front in the "traditional" style.  With the remote, there seems to be a slight lag in needle adjustments.  Change any LA backplate to metal ones, just to avoid future aggravation! LOL!!

I have some parts packages in the basement with the FP numbers on them.  If no one else shows up with them, I will post them later.

Big Bear

[Pat Johnston]

I bet Bill can provide the part number.  His comments are right on.  I've done many FP/LA25's through 46's and they do indeed all have the basic 10mm outside diameter venturi for mounting in the engine case.
Pat

[Balsa Butcher]

Well, I'm not Bill or Pat but the OS  25-25FP-S venturi you are looking for is PN:22312000. Its matching Needle Valve Assembly is PN:22311000. Both are currently in stock through Tower Hobbies. 

[Frank Imbriaco]

  Pete,

  The venturi  o.d. spec for the  LA25S and the LA46S differ on Tower's and OS web. That's what I'm getting at.
It may be a mistake, but I want to be sure.
Thanks,

Frank

[Balsa Butcher]

I'd go with Pat's recommendations. Also, the stock needle valve assembly is worth having but most substitute a ST or PA NV assemble. They have a thicker spray bar which decreases the size of the venturi opening even further and will entail drilling out the case and venturi. The procedure has been explained on this forum, not a big deal.