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Author Topic: ST-V60 with spigot venturi fuel consumption  (Read 3995 times)

Offline Jimmy R. Jacobs

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ST-V60 with spigot venturi fuel consumption
« on: January 03, 2008, 07:02:15 PM »
I'm breaking in a rebuilt ST-V60 for my new Shark 45, and the tank I built is 5 oz. Spigot type Venturi size is .203 ST NVA.  The engine has lots of power (12-6 prop) and very good 4-2-4 run with 20 min. run time so far on test stand.  At this time the engine will run about 5 min. on a tank.  The engine has a hemi head, shimmed to .0035.  So my question is:  will the fuel consumption get better?  Will a smaller spigot Venturi, say .190, get better fuel consumption or lower compression?  Oh yes, I am running 10% 11-11 Power Master fuel.  I'm not saying the spigot makes it use more fuel.  Just need to get better fuel economy because it's the biggest tank I can fit in my Shark.

Jimmy Jacobs

Offline tom hampshire

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #1 on: January 04, 2008, 06:36:47 AM »
Jimmy - The economy might get a little better as the ring seats, depending on how much time the engine had on it when you got it.  I generally set up a tigre 60 with a venturi of .191.  If you fly with the .205 venturi, watch out overhead the first time, as it may sag due to fuel starvation.  So sneak up on it easy.  Tom H.

Offline Bill Little

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #2 on: January 04, 2008, 07:44:12 AM »
Dropping from 10% nitro to 5% nitro will help, as you know, also.

You may need to take a page out of Brother Al Rabe's book and build a special tank.  Getting the ST 60 to do the pattern on 5 oz. will be a challenge.
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Offline frank williams

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #3 on: January 04, 2008, 07:45:07 AM »
Typically I have found that the spigot venturi atmoizes the fuel better and the run duration goes up accordingly.  You may run slightly hotter with the spigotted ST60 than with a peripheral jet or spraybar venturi.  However, the spigot venturi does draw better than either.

Offline Bill Little

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #4 on: January 04, 2008, 08:36:09 AM »
Typically I have found that the spigot venturi atmoizes the fuel better and the run duration goes up accordingly.  You may run slightly hotter with the spigotted ST60 than with a peripheral jet or spraybar venturi.  However, the spigot venturi does draw better than either.

Frank,

Are there any tricks to getting a ST 60 through the pattern on 5 oz. of fuel like Jimmy needs to do??  He's using it in a Shark 45 so there is plenty of power available.
Big Bear <><

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Offline frank williams

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #5 on: January 04, 2008, 11:29:43 AM »
Pull the venturi bore down .... the .200 sounds a bit large.  5% nitro is fine for an ST.  You said the head was at .0035 ..... you probably meant .035.  As was said, as the ring comes in the run time will go up.  I just broke the engines in in the air after a test run on the ground to make sure its wasn't gonna blow up..... just run it fat ..... make sure you know its gonna be a short flight .... a manuever here or there to load it up ... then level out to let it cool .... or a bunch of bench running.  5oz may be tough ... I usually ran at least 6oz ...... mostly 6.5oz

Offline RandySmith

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #6 on: January 04, 2008, 12:18:50 PM »
I'm breaking in a rebuilt ST-V60 for my new Shark 45, and the tank I built is 5 oz. Spigot type Venturi size is .203 ST NVA.  The engine has lots of power (12-6 prop) and very good 4-2-4 run with 20 min. run time so far on test stand.  At this time the engine will run about 5 min. on a tank.  The engine has a hemi head, shimmed to .0035.  So my question is:  will the fuel consumption get better?  Will a smaller spigot Venturi, say .190, get better fuel consumption or lower compression?  Oh yes, I am running 10% 11-11 Power Master fuel.  I'm not saying the spigot makes it use more fuel.  Just need to get better fuel economy because it's the biggest tank I can fit in my Shark.

Jimmy Jacobs


HI Jimmy

I setup over 700 of the ST 60s, I think you are going to have a very hard time getting a full pattern from 5 ounces, regardless of any type of fuel delivery system. The best way to do this is with a .175 true venturie or any other of the same area. I setup many that used a .181 venturie and ran either a 13 x 6 Bolly or a 12.5 x 5.5  Bolly, both used 6 ounces to just make a pattern.

Do you have any idea around when this 60 was made, The biggest fuel gain would be made using the latest piston with the tall baffle. Many of the much older 60s had shorter baffles on the piston top and used more fuel.Even when you used the same piston in a late model ST 60. The taller baffle deflected the fuel up into the chamber, Shorter ones let it just go across the piston and out of the exhaust.  Also a few engine tuners used to file or machine the top of the baffle shorter as one of their *trick* setups.... (this is how you get them to use 7 1\2 ounces)

If you have to you can always add 10 to 15 thou head shims and increase the prop pitch to get more time.
I have seen a couple of people use a Bolly 11 x 7 4 blade or 12.5 x 8 3 blade and get by on  5 1\4 ounces of fuel
try to set the motor up on 5% nitro to start, as the hotter weather gets here you will naturally get better fuel milage

Regards
Randy

Offline Jimmy R. Jacobs

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #7 on: January 05, 2008, 04:25:18 PM »
Well, I guess I'll just bite the bullet and cut the nose ring off so I can get a 7+oz. tank in.  I also made a spigot Venturi .190 size.  Oh, I always break them in with extra head gaskets.  Thanks for all your help!

Offline Steve Helmick

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #8 on: January 05, 2008, 06:43:51 PM »
Dave Royer brought an old Merco trick back to light of day. Add (up to) 5% unleaded gasoline to your fuel, and your fuel economy will increase noticeably. I'd sure try it. Also would put a few layers of pantyhose material on the venturi to reduce the effective throat area and keep bees out.   y1 Steve
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Offline Jimmy R. Jacobs

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #9 on: January 05, 2008, 08:22:14 PM »
Steve, thanks for the help.  I've never used unleaded gas but I've heard of using white gas, but have never tried it.  Venturi size is not a problem as I have a lathe, mill and welder in my shop so I make my own parts and I can make any size Venturi I need.  Yes I have used pantyhose.  I put an o-ring groove on the top of some of my Venturis to told the pantyhose for restriction, but then I generally make a smaller Venturi.

Anyone building a 45 Shark that needs more than 5 oz. of fuel may want to install a larger fuel tank before the nose ring is installed so you don't have to cut the nose ring off like I did.  Hope this helps someone.  Thanks, guys for all your help.  If there's more I need to know, please let me know.

Jimmy Jacobs

Offline RandySmith

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #10 on: January 05, 2008, 08:31:19 PM »
Well, I guess I'll just bite the bullet and cut the nose ring off so I can get a 7+oz. tank in.  I also made a spigot Venturi .190 size.  Oh, I always break them in with extra head gaskets.  Thanks for all your help!

There  is another easier  option, you  can add a sump to the tank back-bottom if it is a metal tank, by soldering on a large metal cap or make a sump out of tin stock, its not very hard to do...or  you can find a short plastic tank and plumb it up as a stunt tank


Regards

Randy

Offline Jimmy R. Jacobs

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #11 on: January 05, 2008, 10:38:22 PM »
  Randy  thanks but I already made a new tank and cut off the nose ring off, os I can get it in. If I would have known, I would have put the tank in when I was builting it. I should have known. since I've built several ST 60 power planes, but never had trouble putting in fuel tank in .

                                                           Thanks help is all was a good thing.  Jimmy

Offline Bootlegger

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #12 on: January 10, 2008, 08:16:02 AM »
 #^ n~  Guy's could someone post a picture of the "spigot" set up ?  I can't seem to get an idea as to what it looks like in my  ? "Mind"?  .   
  " Of all the things that I have lost, I miss my mind the most"... n~
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Offline Ray

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #13 on: January 10, 2008, 03:22:54 PM »
There is no hollow tube across the throat of the venturi, nor is there one holding down a ST-style sprinkler venturi.  It's just a stub jutting out into the venturi from one side. 

Offline Jimmy R. Jacobs

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #14 on: January 11, 2008, 12:21:15 AM »
  Spigot venturi is not a sprinkler . NVA. in same place, but spigot venturi has only one hole with tube from hole in needle valve to just in side venturi hole about .020 or so inside .  Hope this helps

                                     Jimmy

Online Brett Buck

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #15 on: January 11, 2008, 09:39:02 PM »
Ah, OK. Now I see. I have also put in the wrong NVA in one  ST engine and now I know why it gave me fits in trying to start, run and fly. I changed it out to the first type, no more porblems, but I definitely misdiagnosed the actual problem. H^^ LL~

     Here is the drawing of the Supertigre 46 spigot venturi that I hypothesized in my Stunt News spigot venturi article. I think the 60 is similar.

  Note also that there is an extra o-ring below the annular manifold. That was the best thing I ever did for ST46 run consistency - maybe the only worthwhile modification I ever used or saw to an ST.

    I have nothing much to say about how much fuel is used by a 60, but it's my basic philosophy that you always need to make plenty of room for fuel and not cripple yourself in terms of engine setup. If need be, I can get around 9.5-10 oz of fuel into my airplane, in a 6" long space.

      Brett

Offline RandySmith

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #16 on: January 12, 2008, 02:58:01 PM »
""Note also that there is an extra o-ring below the annular manifold. That was the best thing I ever did for ST46 run consistency - maybe the only worthwhile modification I ever used or saw to an ST.""


There are many mods to the ST 46 and ST engines in general that are worthwhile, Putting in higher quality bearings is one since most ALL  ST 46s  came with open front bearing, the did leak , some much more than others, I have also seen many rear steel bearings that had corrosion in them new.

Getting rid of the Spinkler venturie and going with a true venturie is a very worthwhile endeavor, They draw fuel better, and do not burp over and over and over again at the end of the flight like the ones with all the little holes. The standard Sprinkler system had a wide deep groove cut all the way around The venturie, when you would run low on fuel and suck air into the line this would let the bubbles also go around the inside groove, letting the air in with fuel, making the lean burps at the end of the flight.

Balancing the crank back to the T crank shape helps much.

Taking the aluminum band off of the new stuffed cranks sometimes saved the engine from being totaled when it came apart.

cutting fins and a heat dam on the head did help the engine run cleaner when the glow  plug wasn't perfect and you ran a deep 4 cycle. It aslo helped it transistion a little better 4-2

using the early light round rods or using an I beam  rods was better than using the much heavier flat beefy rods that came from the Pylon racing 40, this really help most when you had the stuffed full circle unbalanced  crank.

There are many more  mods  that are  helpful to ST and many other engines.  I know many supposed  engine gurus    screwed up a lot of these and other engines  making some worse has  tainted  some views ,but remember  there are a lot with improved runs because of some of the above  mods.

I have modified literally 100s and 100s of Super Tiger motors  and  ran test on  this and  much more  for years and years. I also used the engines  with   ST stock venturies,   Restrictors, True venturies, fuel post venturies, and a couple of hybrid types. with many HP  plots of the exact same engine, and suction test, not to mention  in flight test same plane same engine with differant configurations.


Regards

Randy

Online Brett Buck

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #17 on: January 12, 2008, 07:16:08 PM »
""Note also that there is an extra o-ring below the annular manifold. That was the best thing I ever did for ST46 run consistency - maybe the only worthwhile modification I ever used or saw to an ST.""


There are many mods to the ST 46 and ST engines in general that are worthwhile, Putting in higher quality bearings is one since most ALL  ST 46s  came with open front bearing, the did leak , some much more than others, I have also seen many rear steel bearings that had corrosion in them new.

<<snip..>>


   Oh, I remember those days. Makes me very glad that it's 2008 and not 1984!   However, I would have to say that the key in any case is getting a good ring. If you had that, you were pretty much set, and if you didn't, you were rearranging the deck chairs on the Titanic. I tried all the porkchop cranks, etc. but these were all in the noise compared to the quality of compression seal.

     I know that *you* might be able to make useful mods, but for the average guy it's almost certainly going to be worse than a stock motor and it many of the crazy mods I saw were not reversible - and they aren't making ST46 spare parts any more.

     I would hasten to point out that the spigot venturi was something that I have never tried on any Supertigre, it was a notional idea of how I *would* do it if I was interested in trying it. It was a miraculous improvement on some other engines, but I never thought the Tigre needed a lot of help beyond the dribble-prevention o-ring.

    I am also amazed that people are still fiddling around with Tigres, etc, for serious money in some cases, when for the same money you can easily go buy far superior engines that don't require any fiddling. To each his own, I suppose.

    Brett

Offline RandySmith

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #18 on: January 13, 2008, 11:03:02 AM »
HI BRETT

I never adddress 1984 vs. 2008, but I agree 1000% the quality and quantity of great stunt engines and products are far better today,  And YES  many people still use ST 46s and many more old motors, I am settting up 4 right now for people. I just finished 6 of them and have other 60s HP 40s  OLD 35S engines that I am setting up for flyers, most of them are  ..new...
I am continually amazed at the brand new in box engines that show up at my shop. And the ST 46 was discontinued back in the 1970s
In regards to ring seal, that applies to any engine that uses a ring, not just a ST46. If You don't have a good ring seal, you don't have an engine.
Although there was a big problem with the ST 46 that most people never recognized, more often than not the engine came with a ring in it that had zero or just barley one thousands gap.
 This was disaster, the motors would be very critical to break in ,and most would just heat up ,the end gaps of the ring would touch.  Then the ring would get even hotter..heat up more, and quickly wear a out of round, flat spot on the ring.
Setting  ring gap is one of the parts of  "blueprinting "and engine, another worthwhile item to do. unfortunately your are right that there are not many that do that properly.
When the ring flat spots,The engine was ruined on the spot, Most of the replacement rings also had zero gap , unless you had a cylinder that was worn at the top, I have even seen many that were   "bell" shaped" after  running.
To compound all of this  some  ST 46s came with chromed sleeves, some with steel non chromed sleeves, The ring end gap needed to be set differant on each. You could glaze a ST  sleeve with the wrong gap or if too much have the ring not seal properly. The best thing that happened to CL was ABC  AAC technology.
Another big problem was if the ST 46 had a chromed sleeve, when rebuilding many of these that had a good bit of run time had a mirror surface on the sleeve, the chrome was very hard and most people either couldn't, didn't know how, or didn't have equipment to hone a new "cross hatch" onto the sleeve surface, without this it was almost impossible to ever seat  a new ring. Needles to say the engine was never as good after that

I made fuel post venturies for the ST 46 and ran and tested them many years ago, along with ones for the OS , HP  and OPS.  There was no advantage in power or quality of run over a properly made venturie, however we used them a good bit in HP and OS engines. And they run much better than the restrictors most used then.
 The best thing about them in those engines ,as the ability to instantly change the size of the  venturie, with precision, by screwing the post in and out.  And in the OS motors case ,it fit the engine better since there was no case material to install a true venturie. This was particularlly helpful to me when developing the later schunrule and then piped engines to get the proper size the venturie needed to be.

Regards

Randy
« Last Edit: January 13, 2008, 11:41:00 AM by RandySmith »

Online Brett Buck

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #19 on: January 13, 2008, 03:05:27 PM »
I never adddress 1984 vs. 2008, but I agree 1000% the quality and quantity of great stunt engines and products are far better today,  And YES  many people still use ST 46s and many more old motors, I am settting up 4 right now for people. I just finished 6 of them and have other 60s HP 40s  OLD 35S engines that I am setting up for flyers, most of them are  ..new...
I am continually amazed at the brand new in box engines that show up at my shop. And the ST 46 was discontinued back in the 1970s

     That's part of it (and I see them and people ask me about them all the time). I guess the difference is that you and I were active competitors and trying to use them, and have a more objective view. Even as early as late 70's people were almost desperate to find alternatives due to the frustration factor of trying to make ST46s run consistently with decent power. Really smooth and gutless was pretty easy, powerful and absurdly inconsistent was a little harder, and smooth and powerful was so difficult as to seem to be magical. The remarkable amount of fiddling required to keep them at competition performance levels was beyond anything most guys flying now could imagine. Unfortunately, until piped 40's came around, there weren't many better alternatives. But as soon as it looked like that was going to work, we all dropped the ST like a hot potato and never looked back.

     Brett

Offline RandySmith

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #20 on: January 13, 2008, 08:23:29 PM »
#^ n~  Guy's could someone post a picture of the "spigot" set up ?  I can't seem to get an idea as to what it looks like in my  ? "Mind"?  .   
  " Of all the things that I have lost, I miss my mind the most"... n~

Hi Gil

This a a fuel post or spigot  venturie, the fuel pickup and needle is on the same side. the only thing that goes into the venturie  is just a small part of the spray bar, and it goes in only from 1 side, the first ones are for the OS 35 S  and just screws onto the side of the case.
This version for the  OS like the ones for the  ST46 below are all tuneable  for the  exact size you need by screwing the post in deeper or backing it out with precision, you then just lock it back down with the  jam/seal nut

In looking down the center I think you can clearly  see this.   one of those  picture is worth a 1000 words  deal.. y1

Randy

Offline Bootlegger

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Re: ST-V60 with spigot venturi fuel consumption
« Reply #21 on: January 16, 2008, 09:47:43 AM »
 H^^  Randy, I sure do appreciate the pictures. They really showed me what I was looking for.
  Again thanks as the pictures do take the place of many words...
                   Gil
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