More Results with "New" 25LA

[Brett Buck]

I had previously noted that the "new" 25LA was much stronger than the originals, and a bit stronger than the 20FP. Now, I have gotten a fair number of flights on it, and it has settled down to *outstanding* performance and consistency. The setup is

*STOCK* 25LA-S (new version)
*STOCK* E2030 muffler
*STOCK* Venturi and rear needle assembly DO NOT change it to front needle, or at least don't expect it to work better.
*STOCK* OS A3 glow plug
APC 9-4 bone stock, with TE sanded down so it won't cut your finger
10% RO-Jett fuel - 3 oz for a full pattern
Launch setting - Find click of needle closest to 13100 RPM, if there isn't one, use the richer/slower notch. Engine should be mostly 2-stroking but occasionally blipping into a 4/misfiring
Tank - Sullivan SS-4 set up for suction, with muffler pressure into suction/overflow vent.

    It is a better stunt engine than the 20FP, the run quality is at least as good, and it is more responsive in the maneuvers. Takeoffs are like an electric, the engine seems to hardly unload at all (which explains the reason it blasts off the ground, and its because it has much more "power"). This worked at anywhere from sea level and 70 degrees and moderately humid, and 100+ degrees and not at all humid, on the Skyray/Flite Streak sized models.

   I cannot guarantee that this is the best possible setup, and using a 10-4 seems like a realistic possibility, but it works awfully well, better than most people have ever had in their lives in terms of stunt run quality. Jim and I cranked out 5-6 flights yesterday, all with perfect runs, from the early morning with overcast and rain to 100 degree California Sunshine. This is consistent between several different engines we have around here, all were much better than the old ones.

    You must have the *new* 25LA. I finally got a hold of a couple of the ~10-year-old blue 25LAs for a comparison test. They were both the same, and much weaker than the "new* version and weaker than the 20FP. A good test is to set it up on the stand, put in 10% and bolt on a 9-4 APC. Start with the pre-set needle, start it, and run through a 16 oz tank of fuel. The engine will rapidly go richer and richer, keep turning it leaner to keep the same RPM, which will be around 12500. Let it cool (DO NOT touch the front end or venturi for a while after this run because you will be sorry...), then start again, and peak it out. The "new" version will easily hit 14200-14300 on 10%. The old version, by comparison, will be good for around 12900. A 20FP will be around 13300-13400 peaked out.

   I don't have a 25FP to compare to, but I think the performance is about on a par FP, but the LA runs better.

    The only thing wrong with the rear needle is that it come in a bad position to get broken off on a profile, and that's exactly what happened. I haven't tried it but I think you should be able to turn the backplate 90 degrees clockwise (as viewed from behind) but there is a flat on one side of the backplate that seems to be for liner clearance. That puts the needle up behind the cylinder head on the muffler side, which is harder to access and might cause you to burn your finger, but will not get broken off.

   The needle it a bit touchier than the front needle but it works just fine.

   I don't know how to distinguish between the "new" and poor-running "old" version from the outside or from looking at the box. There seems to have been some inadvertent or seemingly irrelevant change made (maybe in the processes or materials) that made *all the difference in the world* to the performance.

    Brett

[Gene O'Keefe]

Is there a specific part number to look for or manufacture date or physical appearance for the "new" version ?

[Brett Buck]

Is there a specific part number to look for or manufacture date or physical appearance for the "new" version ?

  Not that I can determine. I just got them from Tower new, and they have been around for about 5 years.

    Brett

[Tim Wescott]

That also means that you can't trust that the magic won't go away.

I have a blue-case 25 LA that seems to be "new" (either that or my 20 FP is really really sick).  So I suspect that if it's silver, it's OK.

[phil c]

Talking to several flyers the LA 25's seem to be more variable lately(sample of about 12).  Some run well out of the box, some take a long time to start running well, others seem to wear out(lose power) fairly quickly.  There doesn't seem to be as much variation as some of the various Fox 35's though.

The first one I got about 10 years ago took 2 years and wore out 2 piston/liners before it suddenly started running flawlessly.

[Brett Buck]

That also means that you can't trust that the magic won't go away.

  Understood, I wish I could point to an indicator, but I can't, without running it. There is no doubt that it is FAR stronger than the older 25LA, it's not even close. It's definitely NOT unit-to-unit variation, the old ones were about all the same, and the new ones seem to be about the same (6-7 examples so far).

   You can tell right away which are the good ones once you fire them up. It will 4-stroke on a 9-4 at about 13100 straight out of the box, and maybe peak out around 14500 - and there's no way the old ones could do anything like that.

     Brett

   

[Bootlegger]

Brett can you tell what size the venturi is? I have one and with 10% I can't get more than 5 min run time on three oz and I'm wondering if the venturi is too large, it is the one that came with the engine.

  It does have the nva thru the venturi, no rear needle. I am running a 9x4 apc prop also and taching about 10,300, it seems to want to "lug" at higher rpm, and the engine has from 30-45 min run time on it.

         Thanks
   

[Brett Buck]

Brett can you tell what size the venturi is? I have one and with 10% I can't get more than 5 min run time on three oz and I'm wondering if the venturi is too large, it is the one that came with the engine.

  It does have the nva thru the venturi, no rear needle. I am running a 9x4 apc prop also and taching about 10,300, it seems to want to "lug" at higher rpm, and the engine has from 30-45 min run time on it.

  Something very strange is going on. I doubt that mine could be made rich enough to get 10300 on a 9-4 without quitting outright. If your venturi is abnormally large, as suggested by the fuel consumption, you would have a great deal of trouble getting it to run that slowly, and you would expect that it would be going either very slowly in the air, or run away dramatically. I would guess you might have a bent crank, or some other internal issue.

   Fire it up, peak it out with an APC 9-4, note the altitude and temp, and measure the RPM. A good runner should easily get to 14000 rpm on 10%.

  The venturi on mine measured .257 using calipers, which is probably really 6.5mm (.255). The spraybar (stock rear needle as supplied) is the same size at the OS regular front spraybar, at about .135 (probably  3.5 mm/.137). I can check a few other engines tonight but something sounds very wrong.

   Brett

[Steve Scott]

How long will an LA25 run on a 16oz tank?  I always thought more and shorter runs were the norm...

I just scored a new old-stock blue LA25 for an S-1 Ringmaster I'm building.  The dealer let it go for $38 so I can't complain.

[Dane Martin]

the 25LA is a great engine. i bought one NIB and donated it to the beginners for the NATS. hopefully it helps someone move up!

[Andrew Tinsley]

Hello Brett,
As I have noted before, all of my OS LA25s run pretty much the same. I have them from the introduction of the LA 25 in the European market, to a couple that I purchased in the last few months. Most of them will match your performance criteria for a "new" LA25. The very oldest are a couple of hundred revs down or so, but that is hardly surprising as they have had a large number of hours running time and are getting to the stage of being close to retirement!
I have been so puzzled by your claim of a "new" LA25, that I wrote to OS of Japan. The reply together with my initial email are shown below.
There is obviously something odd going on here. I rather suspect that the quality of the LA25 went down for a period and a lot of sub standard engines found there way to the marketplace. Maybe that is the reason that you saw so many poorly performing engines. At the present time I have 8 of the units , but I have had at least another 3 through my hands and have seen other LA25s behaving much as mine.


Dear Sir,

We have not modified 25LA for many years.  So we believe your 25LA and your friend's have same performance.

Best regards,
Junichi Shimazaki

> -----Original Message-----
> From: Andrew Tinsley [mailto:tin.lizzie@tiscali.co.uk]
> Sent: Thursday, July 31, 2014 9:14 PM
> To: OSエンジンインフォメーション
> Subject: OS LA25 engine.
>
> Hello,
>              Please can you tell me if the LA25 has been improved recently
> to produce more power? A renowned flyer claims there is a "new"
> LA25 which is much more powerful. I can see no difference in power between
> my very early LA25 engines and those that I have purchased in the last few
> months. Could you please tell which one of us is correct?
>
> Many Thanks,
>
> Andrew.


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Regards,

Andrew.

[rustler]

I have one of the Sheeks/RSM Mosquito kits. I was thinking to put in twin O.S. 26 or 30 4-strokes, but they will be a bit heavy?
Maybe twin O.S. LA 25's would be good?
Anyone got any thoughts?

[Geoff Goodworth]

Jack flew the original with Fox 35s so LA 25s should be fine.

[Phil Krankowski]

How long will an LA25 run on a 16oz tank?  I always thought more and shorter runs were the norm...

I just scored a new old-stock blue LA25 for an S-1 Ringmaster I'm building.  The dealer let it go for $38 so I can't complain.

This is a technology change.  The ABN P/C assembly, aluminum piston, brass with nickel plating cylinder, has to heat up fully to operate properly.  The material choices make for a very tight engine while cold, and a properly fitting engine while hot, so a lot of cold running is not very good for the engine.  The hardness of the parts is also quite different from one part to the next.

This is fundamentally different from a lapped iron engine where the fits of the cold engine are similar to the fit of the hot engine, without significant differences in the thermal coefficients of the materials.  The hardness of the various parts area also similar being of the same, or similar, material.

Good score on that engine too!

Phil

[Andrew Tinsley]

Hello All,
I have been running the LA25 on a 10x4 APC prop I have the E2030 silencer and Hayes tank as per BBTU. The runs are excellent, it doesn't seem to have the "pipe like" quality of the FP20 BBTU. I have tried running at the FP20 BBTU revs, but even so the pipe style run just doesn't seem to be there. Anyone else have the same experience? It isn't that the LA25 run is bad, far from it, it just seems to lack the pipe style of run

Andrew.

[Dane Martin]

Dear Sir,

We have not modified 25LA for many years.  So we believe your 25LA and your friend's have same performance.

how many years are they saying they have not been modified? there are physical differences. maybe not the case, but other parts. like they were out if the box with a separate plastic back plate, a metal nva mount, and then the nva was different.
then they did the one piece back plate with nva. so based on that, I'm only guessing, but other changes are possible, even in metal alloy changes or cost saving measures that are not important enough to mention, but could affect performance.
running an engine at full throttle is a lot different than rc application. it's much more demanding. so even a small change could make a big effect.

[Andrew Tinsley]

Hello Dane,
It isn't "my" quote, simply what OS say. Maybe they know more about their engines than anyone else?

Regards,

Andrew

[Dane Martin]

Hello Dane,
It isn't "my" quote, simply what OS say. Maybe they know more about their engines than anyone else?

Regards,

Andrew

i know you didn't say it, it just raises more questions for me. like i said, i have examples of both versions, so i would ask them how long they have been manufactured the same. they most certainly have not always remained the same. and just because one guys says it within the company, doesn't always make it so. they know more than me about engines in general, not just os.... but I'm holding two different os 25LAs, so maybe not every employee within the company knows the entire history?

[Andrew Tinsley]

Hi Dane.
You may well be correct in saying that one employee doesn't know the whole history of the LA25. I just thought it was worth asking OS, they should know. Let me make one thing quite clear, I do not in any way question Brett's assertion that something has changed in the LA 25s that have been through his hands. The problem that I have, is that I have not seen this difference and I am simply trying to understand what is going on here. If I could get my hands on one of the dud engines, it would be a fairly straightforward process to strip both types down and simply measure them up. There are relative few reasons why they differ in performance in a big way and its not very difficult to nail that difference. Brett says there is a "huge" difference in performance, so it should be easy to spot the difference. Things that come to mind are venturi ID (OS are good at putting out venturis of differing internal diameter. The next thing is the engine timing, that is simple to measure with a wheel Just measuring the heights of the top and bottom of the ports with a vernier height gauge would do. Head volume and shape are another good bet as is differing deck height. Crank shaft internal diameter is another remote possibility.
  That just about wraps it up. If you have a new and old LA25 can you check them out and see what the difference is? I suspect that large batches of engines are made at one time. I doubt that there is a production line for each engine type. If a machine was set up incorrectly (port cutting of the cylinder, for example). Then a large number of engines would be made with inferior performance. It only needs this batch to escape QA and there you have the answer to the conundrum. There isn't a lot I can do, as all the engines I have are more or less equal in performance.
  If anyone has an "old" and "new" LA25 then it should be very easy to spot the difference, all one needs to do is to strip them down and measure them. The difference should be quite obvious.

Regards,

Andrew.

 

[Dane Martin]

10-4 Andrew. I'll strip them down and see if i can tell any differences.

[Andrew Tinsley]

Hi Dane,
I would first check the ID of the venturi and then put a timing wheel on the engines before you strip them down. A pound to a penny that either of these two things are the culprit. I take it that you have checked them both out for RPM as per Brett's figures for a new and old LA25?
If you do have one of each, you should be able to spot the difference pretty quickly. The LA25s are pretty simple to work on and it definitely isn't some subtle difference that is causing such a big difference in power. It would be really good to nail this one!

Regards,

Andrew.

[Dane Martin]

Andrew,
i apologize for the delay. To answer, no i have not run any of my 2 stroke OS engines in some time. I'm trying to be a four stroke guy. i have always been an OS fan, especially the LA series. at this point it's easier for me to just strip them down, than to run them. I've never done a back to back comparison.

[Andrew Tinsley]

Hi Dane,
Hope you find a difference! This whole business has been bugging me, as I just cannot get my hands on an "old" or substandard LA25! Mine all run pretty much like Brett's "new" LA25s.
I very much doubt that any minor differences in the NVA system would explain the large differences in power, unless it is a big variation in diameter of the body. But then it would be so obvious that anyone would notice it. If you can, please get a timing wheel on the engine. My bet is that the new and old are a timing difference.
Hope you can throw some light on this. It has been going on for some time so no need to rush!

Andrew.

[Motorman]

Much about how an engine runs has to do with the roundness, taper and fit of the piston/sleeve. At that price point sometimes they get it right. If you want an OS 25 that runs great every time try the 25XZ. You get what you pay for.

MM

[Andrew Tinsley]

You could well be correct about that. I have had several new piston / liners for the OS LA 46 that were seriously out of round. The odd thing was that after a brief running in period (completed when the fuel consumption drops markedly), the engines performed faultlessly and well up to normal LA46 standard.
It seems as if the act of "running in" somehow makes the liners assume a roundness again. I have to be honest and state that the only thing that I have noticed about the LA series is the shaft can be quite tight to begin with. This tightness goes away quite quickly in most cases. I have had one LA46 that wore out a P/L and the shaft only eased up on the second P/L.
Agreed these are cheap engines and you get what you pay for. There are better engines to be had in this price range, but that is another story. Despite my criticism these are an excellent engine for stunt that doesn't cost big bucks, but they do wear out faster than most.

Andrew.

[phil c]

Hi Dane,
I would first check the ID of the venturi and then put a timing wheel on the engines before you strip them down. A pound to a penny that either of these two things are the culprit. I take it that you have checked them both out for RPM as per Brett's figures for a new and old LA25?
If you do have one of each, you should be able to spot the difference pretty quickly. The LA25s are pretty simple to work on and it definitely isn't some subtle difference that is causing such a big difference in power. It would be really good to nail this one!

Regards,

Andrew.

Since I abuse engines for other than stunt purposes I put the oldest LA 25 in the mill and took .020 off the closing side of the crank and squared up the  internal edge put a slight radius between the front and rear edges at all four corners.

That motor turns the same props about 5-800 rpm faster than the stock crank.  So if you need more power, there is plenty their with very modest changes.

Phil C

[Andrew Tinsley]

Yes it isn't all that difficult to improve the power of the stock LA series, or for that matter any of the cooking variety of engines. What is bugging me is that I can't get my hands on one of Brett's old style LA25s. I have absolutely no doubt that they exist, but not being able to find one in my part of the woods, means that I can't do an A / B comparison and track down the differences. For example, your mod would stick out a mile given a strip down or even a peek through the venturi!
  I have probably upset Brett already about my comments on the LA series rear NV. I reread my post and cringe, so apologies Brett, I really need to read my posts before I press the send button. I am a bit doddery and a rear NVA is a fantastic bit of safety engineering. They work fine in a wet two, but any other type of setup, they are inconsistent. I have put a good number of hours in trying to get to the bottom of the problem without success. I even used a helium mass spectrometer to find leaks  in my set up.

Regards,

Andrew.

[Brett Buck]

  I have probably upset Brett already about my comments on the LA series rear NV. I reread my post and cringe, so apologies Brett, I really need to read my posts before I press the send button. I am a bit doddery and a rear NVA is a fantastic bit of safety engineering. They work fine in a wet two, but any other type of setup, they are inconsistent. I have put a good number of hours in trying to get to the bottom of the problem without success. I even used a helium mass spectrometer to find leaks  in my set up.

    No, I am not upset about that. I know it works as intended, and how it works while doing a 4-2 is mostly beside the point, since that's the wrong way to run it anyway. Although it seems fine tp me when I do that, too, and a similar arrangement worked fine even on a lowly Fox 35. So, no, I don't care one way or the other. I am providing my (pretty carefully investigated) test results, and the knowledge of excellent performance for something you can get in 3 days for $75.

     It is mildly irritating that everybody seems to be willing to question my ability to tell the difference between an engine that peaks out at 12200 RPM and one that peaks out at 14500 rpm, and insisting there hasn't been any changes made. It's a completely different engine from the original type from the early 2000s in terms of performance. Previously, I had dismissed the "old" 25LA as not as good as a 20 in terms of both power and run quality. I got one of the old ones on loan, and nothing about it changed my mind. About 5 years ago Jim Aron got one of the new ones, and it was immediately clear about 2 seconds after he started it, that it was a whole new kettle of fish, and that it was probably the best of the bunch for our purposes took about 1/2 a flight. It is not subtle, it's dramatically different. So repeatedly posting "we think it's the same" isn't advancing the state of the art. I may not be the sharpest tool in the shed, but I can read a tachometer, and I can tell whether it pulls the airplane better or worse, particularly when it is this dramatic a difference.

     I am not particularly upset about it, this is a kid's tea party compared to some of our topics. I would be very interested in the specific differences myself (which I haven't been able to determine in the brief time I was willing to expend on it) but to try to claim is isn't different because we don't know the right things to look at, despite the fact it demonstrably works differently (and much better for our purposes), does grate a bit. Not that this is unique, everything I find with regular engines is either "no one else ever had that problem" (despite everyone i know having the same problem), or "that's not a bug it's a feature" (when it's clearly a bug), or "you're an idiot and don't know what you are doing", which is certainly an arguable point.

   I also note that, as I have repeatedly, the time is ripe for a repetition of my small engine experiments from the early/mid-90s, using the same parameters and currently-available engines. It doesn't help anyone to say the 20FP is so great if you can't get one (which when I did it, took $54 and a 10-minute trip to the hobby shop, or 3 days from Tower). The parameters have been noted at length, all it takes is some time, some (*brand new and unmodified, and not "disassembeled/cleaned/lubed"*) sample engines, a handful of various  (inexpensive) 3 and 4" pitch props, and careful objective evaluation. That might be a better use of everyone's time than claiming the engine is "the same" (and by implication I am a moron) despite all the evidence to the contrary. I already said I wasn't going to repeat it myself, the "new" 25LA is an exception because it's for Clint's "Stunt 25" contest. If we just want to debate my capabilities or intelligence, there are plenty of other threads for that.


    Brett

[Andrew Tinsley]

Hello Brett,
As I clearly stated, I have never doubted that you have observed a large difference in the power output of the LA25. What interests me is what the difference is between the two. I don't have one of the lower powered LA25s to do a comparison. All of mine run pretty much the same and they all agree with your quoted high end performance. So I can't determine the difference between the low and high output engines. Hence my query to OS, which didn't help. This may be a trivial quest to you, but I find such puzzles interesting and I am curious to solve them. Everyone in this hobby has their own pet interests and such trivia are mine.
With regard to the remote NVA. I would like to use this on just about everything, including older style 4 2 4 engines. I have always run the LA series engines in a wet two so there isn't a problem there. I like to run vintage engines too and this is where I have the problem. I cannot get repeatable results. There are still many people who run older engines in 4 2 4 for stunt and I am one. I really do wish I could get a remote NVA to work in this situation, for safeties sake. It doesn't matter if it is an old style engine or modern schnuerle ported engine. The cuts are just as deep! With advancing years and some serious medication, I find that I am getting fingers dangerously close to props without realising. I have spent a long time trying to understand the physics of a remote NVA, they are certainly different. I still cannot understand why.

Regards,

Andrew.

Andrew.