Maybe everyone else already knew this, but it was news to me.

  Jim Aron had good results with the new 25LAs a few years ago, so I had waited for a Tower "deal" and got a pair of them for some ridiculous price (maybe $45, but so low it didn't register). They just sat since then. I don't know if this is a reliable indicator of the "new" VS "old" LA, but these came as bare metal as opposed to painted blue like those I had tried and seen other people use in the past.

   Today, after flying "Stunt 25" with the Skyray/20FP at the Ted Goyet contest, I popped one of them on the airplane just to see how it worked. The answer is - very good. I decided to read the directions and follow them *to the letter* to see of there was anything to be learned. I bolted it on the airplane exactly as it came, plastic backplate, rear needle, everything. The needle was supposedly set at the factory to a good break-in position. I primed it as it said and it started on the first flip and ran at a *perfect* break-in setting well into the 4-cycle. After a tank of gas was run through it (which, I might add, didn't take all that long), I put on the flying prop - APC9-4, naturally - and did some testing. It peaked out at over 14,000 rpm right away, and had no problem holding a 4-stroke at maybe 12,800. This is *much* stronger than the 20FP I had been running and at least some stronger than a perfect 20FP. This is much different from the older LAs I had tried, it is *much much* more powerful.

     We flew it and had the same issues we typically had with the 20FP - that is, the fuel consumption was astronomical, and the needle was changing rapidly. Maybe 4 minutes on 3 oz, set at 13000 at launch, and steadily richened up through the (brief) flight. Fired it up for the next flight, and with the same needle, it was down to maybe 11,200 and was dead rich. Tweaked it back to 13000, launched again, and it ran longer and richened up throughout the flight, but not as much. Firing it up again at the same needle got about 11,800, dead rich again. Went through a a few flights doing this and we got 11,200, 11,800, 12,200, 12,400, and 12,600, tweaking the needle more closed each time to get back to 13,000, and the duration of the flight on about 3 oz went longer every time. Eventually we could get through a complete pattern on ~2 oz, which held there the rest of the afternoon.

   Otherwise, the in-flight performance was quite good. The air was a gentle wafting 15 mph breeze and we had a lot of time to fiddle with the Skyray since almost the entire field of the contest passed their second round flights. Flying my regular airplane, the air was not all that bad, and at no time was I concerned, but it was definitely a stiff breeze and certainly not something you could just ignore. The Skyray/25LA was very fast but had the "slow motion" feeling most of the time, and had no issue getting through the pattern. Occasionally it would briefly go rich in overheads which didn't add a lot of confidence, but the rest of the time it was very consistent in flight. When we tried backing it off into a 4-stroke in level flight, the power boost in the maneuvers was more than you would want. This was no surprise, this is not a Fox and that's about what happens with any of these engines (20/25FP. Brat 28, OS32, Magnum 32, etc) with the stock parts. Of course there was abundant opportunity for whip-up but it was no worse than any of the others in that respect.

     One day and maybe 10-12 flights isn't enough to draw any conclusions but it seems like the engine has a lot more potential than the "old" LA that was clearly less powerful than the 20FP. It would certainly spin more prop than a 9-4 APC and would clearly fly A LOT more than a 400-square inch 29 oz airplane.

    By the way, the rear needle and plastic backplate seemed to work just fine. Once the engine settled in, the needle settings were dead-nuts repeatable, predictable, showed absolutely no problems. One click was a pretty big change, which is about my only possible criticism. It looks like the needle would be very prone to breaking off in an inverted crash, which is no better than the conventional needle, but I would be a little concerned that the needle assy. hitting the ground might crack the part of the backplate you care about. Another feature of my particular installation was that the plumbing ran all over the place, since I just took off the 20FP with a conventional spraybar and hooked up the rear needle with the same tubing, etc leaving a big loop, and the filter hanging out near the cylinder head. This led to some starting issues since it was very prone to the fuel running out of the lines. We use the same technique as with it's big brother 40VF - flip through with finger partially covering the venturi and removing it quickly once the engine fired up to prevent flooding it off.  I don't dispute those who have had a problem with the backplate leaking and maybe mine will too, at some point, but so far it seems to work with no issues

    Brett

Thanks for the report, Brett.  I am surmising that the timing seems to have been changed on the .25LA?  With the results you have gotten so far, would you go to the 10-4 APC or stick with the 9-4?

    I haven't tried it but I would expect that it would spin a 10-4 but you would want a much larger airplane. If you just put on a 10-4 on the same airplane,  it might spin slower on the ground but go even faster in terms if airspeed/lap time. The limiting factor would be when it was running slowly enough that wouldn't draw fuel anymore.

   BTW, I am not sure what is different for certain, it could be the timing or it could be something else (like larger ports with the same timing).

     Brett

Thanks!  Sounds like the latest OS .25LA would really be at home in a Classic design meant for the Fox .35.  Or even a new design about 500- 550 sq, in.  What do you think?

   I didn't have a 25FP to compare with, but of course that works well in Noblers, etc.  What I don't know is if the LA can be reliably controlled in the maneuvers, or what it takes to do it.

     Brett

            I see absolutely no power difference in the old vs new engines. We use the LA.25 exclusively for speed limit combat. I'm seeing ten of these engines at one time all from different years. All of us are essentially flying the same planes. The FP however which two other pilots use, run stronger than our LA's. I have blue versions and silver versions myself and I see no benefit of one over the other. Were timing these planes and using identical props, planes, line length, same fuel etc. Your findings are apparently different. I'm just stating my findings with these engines. Ken

I'm a noob to CL.  I have 2 of them. I have one on ringmaster.  I have good runs on an APC 11-4. The engine handles it well and no problems. I'm running Powermaster 15/18 1/2 castor.

Well I'll be blowed! After carefully accumulating FP20s for use with the BBTU (which I think is still an extraordinary style of run from such a lowly beast). I now find Brett advocating the LA25!
Anyone want some FP20s cheap!

Regards,

Andrew.

Definitely don't smash those FP20s -- put them in a box and send them to me

Most folks in the Pacific NW run their 25LAs with 10-4 APC props, and like them.  One fellow I know, from Klamath Falls, flies on a 9-4 when he's at altitude because the engine doesn't have enough grunt with a 10-4.

So if anyone does do the testing that Brett is talking about, be sure to at least try an APC 10-4.  My LA25's seem to not run away on a 10-4, but I don't have Brett's skill or experience so take that statement with a very large grain of salt.

I do know that I have a bunch of over weight planes and I don't fly super well, and I know that an LA25 with a 10-4 (at 600 feet above MSL) will pull one of my porkers through the overheads better than my FP20 will.  I also know that the FP20 works really fine on the lightest plane I have (a Ringmaster, which is still porky at 32 ounces, but lighter than either of my other small planes).

I sometimes wonder why people scrap the OS rear-needlevalve and install a new one right next to the spinning prop!  The rear units work just fine, and are much easier on fingers!

Floyd

I sometimes wonder why people scrap the OS rear-needlevalve and install a new one right next to the spinning prop!  The rear units work just fine, and are much easier on fingers!

They're less friendly about bubbles in the fuel, and more prone to losing prime in the tube from the remote needle to the spraybar.

That having been said, I haven't found the above to be that big of a deal once I figured them out, and, on the old-style FP valve you could mount the thing so that the needle was out of the way of a crash.  On the LA, you can, too -- it just takes some cutting.

Hi Brett,

What I am getting from your report (and generally all your writings) is that just because that engine "A" has more power than engine "B", it doesn't mean engine "A" is what we need.  

  Exactly. A Zalp 2.5 has 4 HP, that crummy PA75 is only running 3/4 horse in stunt trim - which do you prefer?

   The same argument works great with the "there's no such thing as too much power" crowd. I can get a lot more power out of a PA75 by tweaking the needle to peak it out, and better gas mileage as well. So let's all lean them down hard since that will give us more power.

   QED

   Brett

Brett:
Just curious (yes I still keep up on IC)  You mentioned that your plumbing was not really set for the RN installation - you think that had any effect on the variations you were getting early on in your tests? 

  No, I don't think so. The plumbing was the same all day, but the fuel consumption/needle setting changed rapidly at first, and then slowed down, then stopped with no other changes. The same thing happens with all of these engines to one degree or another, even with the plumbing set up for it (like the 20FP).  This one was a pretty big change compared to some of the others, but exactly the same character.

   The fuel consumption change was roughly a factor of 3. It managed about half a pattern on 3.8 oz on the first flight and richened up dramatically through the flight. It made it through a complete pattern some margin on a little more than 2 oz after about the 5th-6th flight and the needle held right on throughout.

     Brett

Brett, thats pretty consistant behaviour with what i saw with my LA 46s,, at least the couple I bought new,, the others were RC rejects,, * they dont have enough power for a 46*  I got them for a pretty good deal too!
anyway, after about 6 to 12 flights the consumption went way down, and it held the needle much better, and this was after a fairly generous bench run in,, ( something on the order of an elapsed 30 minutes in shorter segments,, ) Okwell its generous for a 50 dollar motor LOL

    I have done the first flight on several 20FPs that were also official flights in contests! Actually, the very first run of any type was an official flight. So I knew what to expect. And just like the LA, it got rich enough at the end it was a little iffy to keep running in the overheads.

     What I hadn't done was carefully document it, or have a *factory-set* needle. This time I followed the instructions *to the letter* with the exception of the flying prop, (and flipping with my finger instead of a starter) including running a tank of fuel through it on the ground first. It fired up on the first flip and the factory-set needle was absolutely perfect. On successive flights I reset the needle to get 13000 on the ground, and it ended up going a long way, maybe 3/4 turn, as it settled in.

   I did this mostly to determine you could just take it  straight out of the box and followed the directions, it would work with no other knowledge or modifications. The only think that was wrong for stunt was the prop selection - it says to use a 9-6 or a 10-5 but either one of those would be absolutely supersonic. Even 4" was way too fast at the settings it needed to run. And it even comes with a $6 glow plug! Such a deal.

   So, again, there are so many people opening the engine box, tossing the muffler, putting in an ST needle, replacing the backplate (which may be of some value in terms of reliability although I had NO issues for the 15 or so flights we had) and later getting out the Dremel tool. All of which appears to severely counter-productive, it runs dandy straight as it comes and following the directions. A beginner would need to know almost nothing about engines to make it work while a lot of alleged "engine experts" shoot themselves in the foot.

     Brett

p.s. I forgot to mention this, but it's clear where some of the tightness comes from. After the first flight, I went to fuel it up and restart it, and the venturi was *incredibly hot*. This after it had gone so rich that it made me a little nervous about a flameout. That went away as the engine loosened up and later we were flying flight after flight in a medium 2-stroke and the front end was cool to the touch. I think that means that the plain-bearing section is the draggy part and very rapidly breaks in. I think it also means that you might have to run it a very long time on the ground to get the same effect as a few actual flights (where you are putting varying side-loads on the bearings). It was very "flippy" at the end of the day.

I sometimes wonder why people scrap the OS rear-needlevalve and install a new one right next to the spinning prop!  The rear units work just fine, and are much easier on fingers!

Floyd

I have 2 LA .25's.  Being a noob they have both been in the dirt via figure "9's".  A nasty side effect from this is the rear NVA, being plastic and part of the back plate tend to part company.  Sometimes the backplate mounting ears break off and the whole thing needs to be replaced.  In my case the back plates survived and I replaced the NVA's with the older OS metal version.  Other than that I would have kept the rear mounted ones.  I figured the next figure 9 would just trash the new rear mounted so I went with the front mounted than tend to hold up better.

Hello Phil,
I agree with you, that there seems to be no timing or port differences between old and "new" LA25s as far as I am able to determine. My very latest LA25 does have a larger diameter venturi than the old one and I am pretty sure that this is where the increase in power comes from.
I still much prefer the power delivery of the BBTU FP20 than either of the LA25s.

Regards,

Andrew.

Hello Douglas!
Said very much with tongue in cheek! I was a touch sceptical aboout the claims for the BBTU ........... until I tried it! I wouldn't swop my FP20s for LA25s, although having said that. My pair of FP25s are good powerplants.

Regards,

Andrew.

THE 25 LA pulls a Nobler pretty well, so does an Enya 25SS or 30SS, Lots of power in the newer  small motors

Randy

Brett,

I need to talk to you at the M&M.

There are a couple inconsistansies here. First an FP 20 is not a 25...... (yeah I know, obviously)

I have an FP 25 ABC and a couple LA 25's.

Here's the perimeters:

9X4 ACP
E-2030 muffler
6mm venturi and an OS NVA
10X22, 50/50 fuel

First I ran the FP.....It turned 13,5+/-
Then I ran the LA....It turned 12,9+/-

So, I opened up both engines and the FP has three ports (boost port?)plus the exhaust port.
The LA has two ports plus the exhaust port.

The cranks are slightly diferent but not enough (side by side with the naked eye) to make a big (?) difference.

The parts listed in my manuel are: crank/piston ass. No. 22553000. I called Tower to see if there is/was an update and she told me that that was it! Meaning that the LA has TWO ports and NO boost port. (I guess I'm using the right terminology)

I'm just not smart enough, or knowledgable enough to tell the difference, but I do know that my FP 25 pulls the Jamison like a mule! And no, I'm not going to change engines to see if there is a difference...........to much trouble.

Pull the head off your engine and lift up the liner to see how many ports you have. I'd be interested to know if Tower (the girl) knows what she's talking about.

See you at M&M, Jerry

Here's the perimeters:

9X4 ACP
E-2030 muffler
6mm venturi and an OS NVA
10X22, 50/50 fuel

First I ran the FP.....It turned 13,5+/-
Then I ran the LA....It turned 12,9+/-

   My LA turned 14,500 with no problem right out of the box. Some of Jim's LAs did indeed have a boost port.

    Brett

Hi Randy,

Thanks for that. I didn't realize that the very top of the boost port could be seen through the exhaust, but sure enough there is the guy!

Bret, You got a boost port??

See you at M&M

Jerry

Since about 80% of an engine's power come from the piston/liner fit, perhaps OS is just putting a heavier coating on the sleeve and putting is a little more taper in the sleeves.  We're talking at most a couple thousandth's of taper, which takes quite a bit of skill to measure accurately, without special tools.  The engine tuners go mostly by feel and experience.

or they just mic the P/S   

Randy

Shame on you Randy....

 

Randy C.

Boost port or not in the liner, the question remains- "Is the crankcase machined for the third port?"

Some of the LA series had this third port in the liner but no matching port in the crankcase. There is a thread on the 40 LA that pertains to this.


http://stunthanger.com/smf/index.php?topic=20831.0

Brett

Please take a look in the cylinder and see if the boost port opposite the exhaust is functional.  Thanks.

An interesting report Brett. Does this mean that the 20FP with BBTU has had its day? Just kidding, but I would be interested in knowing which engine you prefer?

Regards,

Andrew.

Thanks for that Brett. I still have one reservation. As far as I am able to determine, there isn't a new LA25. Everything I have been able to measure indicates the same timing etc for all the LA25s that I have been able to measure (new purchase this year, new purchases early last year and two very old LA25s). It just makes me wonder if it is simply a loosening of QC on OS's part giving good and not quite so good engines. The FP20s have been as like as peas in pods and I have a good number of them. The LA25s that I have flown (using the standard BBTU) have been equally consistent, but not quite as good a run as the FP20 and certainly no more powerful.
  I have kept strictly to the BBTU specs for both engine types. I prefer the FP20 from my testing, but I have an uncomfortable feeling that we are not comparing like for like. Maybe there is a modified LA25 engine on sale and I just have old stock?

Thanks again for a most interesting set of results,

Andrew.