The XLS .25 Combat Engine

Tell us what you do to get the best performance from your engines.

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lightning
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Re: The XLS .25 Combat Engine

Post by lightning »

Don Holmes wrote:Alright, Someone write Global and get the answer.
I'm out of the Country until Nov 9th. If anyone gets a solution, please be sure to post it here.
Thanks
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Blue Note
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Re: The XLS .25 Combat Engine

Post by Blue Note »

Wouldn't sub-piston induction and a leaky front bearing let air into the engine but not fuel? For my engine ( which use several different brands of remotes needles ) to continue to run with the carb barrel totally blocked until the tank is dry, the engine must be drawing air and fuel, correct? I have looked at several of my Magnum engines, mostly 15's ( although the 25's seem to have the same characteristic ) and notice that the carb barrel itself seems to be a rather loose fit. If this is indeed the case, could the tolerances of the carb barrel be such that it is letting the air in through the venturi and around the barrel, thus allowing the engine to draw a tiny bit of fuel and have enough air to continue running? While I will not have time to test this idea in the near future, perhaps applying a rather thick grease to the outside of the barrel ( for testing purposes ) could help determine if there is an issue with the tolerances of barrel fit by providing a barrier to stop the potential air flow. This, of course, will need to be tested on an engine that won't stop by closing the carb. Just an idea. If anyone gets around to trying it, let us know, then we'll have something definitive to tell Mike Greenshields at Global to help expedite a remedy and also ask if it is a remedy that they will honor via warranty. As it is a safety consideration to be able to kill your engine, the manufacture needs to have the chance to make it right before we have to start tinkering with things just to make the engine safe and less damaging to our props when we land.
Chris Gunter
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Re: The XLS .25 Combat Engine

Post by boiler »

Blue note, that is what I was thinking was the issue. I don't have one yet but figured that was the only way fuel & air could get in.
Bob (Longhaul) Loescher
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Re: The XLS .25 Combat Engine

Post by Blue Note »

I also realize that air would potentially leak in from the ends of the carb barrel as well, which is likely in that mine will still run with my finger over the carb inlet. Whoever can test this first, post it and I'll be glad to email Mike with a summary of the different things we have tried and the results, but since I have not yet run mine, I am dependent on others at this point unless my schedule opens up.
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David Drowns
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Re: The XLS .25 Combat Engine

Post by David Drowns »

The plane is now Built, have a few tanks of fuel run through the engine, finally got it stuffed and today it's finally time to try it out.

Time for Maiden! :D

Image
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Re: The XLS .25 Combat Engine

Post by David Drowns »

Got 3 flights in today. 1st one after getting the new plane trimmed out I went with throttle up. As the speed increased I got the rare but not unheard of...FLUTTER... :x backed off the throttle and just kept to tight maneuvering to continue break in.

The flutter fix on the MiG is cutting down the aileron TE so after a trim, retry.

Tank two, got airborne, went with throttle up..... :D success, no flutter so off to the races. ran good, smooth and it seemed that pulling back on the throttle she just kept wanting to run, below 1/2 throttle it would slow down but this baby just wants to go. Doing high and tight loops it was smooth at the beginning of the tank but toward the end it seemed to lean out more than early on..?.. :? ..? Finally the tight maneuvering killed it. -Dead stick- :roll:

Now I need to time the run with the 6 oz. tank.

3rd tank, Reset needle rich for high G maneuvers, set timer, going balls out (can I say that here?) this plane seems to get faster each time it flies. Again, high and tight loops, torque rolls, pylon circuits, this plane is covering ground fast. Eventually it seemed to lean again on a high G loop at 6 minutes so I lessen the G's and keep blowing holes in the sky and get 9 minutes before the tank goes dry.

After those "break in" flights I squirt in more fuel to do another RPM check. -dead plug- :o (it is break-in after all) Somehow I had a plug in with an idle bar so I put in a replacement.

Running an APC 9x4, stock muffler, no baffle on 15% I hit 15,700 RPM's on the pinch. This is right in there Don with your run of 15,760 on a 10x3 but a bit shy of your run Kieth of 17,950 on an 8x5.

The test engine when we ran it had a Mouse can, MAS 9x4 on 15% and seemed to have a little better throttle control transitioning RPM's. Maybe it just likes pipes???
I also noticed just like the 15 XLS, this plane came back WET. But I guess if I wanted to keep it dry I'd be flying electrics. :wink: Besides, It's still breaking in.
Leaning??? I guess it dosen't like bubbles. :roll:

No problem killing the engine. Idle could have been better but my replacement plug was used so I'm not counting it out yet. It wasn't a problem before.
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Don Holmes
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Re: The XLS .25 Combat Engine

Post by Don Holmes »

Well I put #1 XLS .25 back in the box affter cleaning and got out #2 XLS .25 then bolted it to the stand fired it up, putting it thru the heat cycles yesterday and noticed it would not shut off when closing the throttle. I put it thru 4 short runs, no muffler 40% nitro 22% castor 8 x 3 prop
it screamed at 22,500RPM #1 only hit 21,118
Storms today so no running in and taching
Don Holmes RCCA #957
Mid Atlantic Combat
sgilkey
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Re: The XLS .25 Combat Engine

Post by sgilkey »

I have been eyeing the new Magnum 25XLS engine, hoping to try one but thinking I would wait and see if they run a nice sale like they did last year on the 15XLS. I saw the post that HobbyPartz has what looks like a 25XLS (without the XLS logo) for less than $50 shipped, so I bought one to try.

I have not seen a 25XLS in the flesh but based on photos, it appears the engine I got from HobbyPartz is indeed the same engine as the Magnum. Overall quality appears very good and is appears to be a significant upgrade from the old 28XLS, which was already a decent engine but not as refined as the 25FX. The carb and NVA, and muffler, in particular appear to be greatly improved.

Casting and machining quality look pretty good. I did see some burrs and rough machining in the crank gas passage and window. But then, the machining in the crank gas passage of a Jett 30 is also amazingly rough. But considering the Magnum 52XLS has a nice smooth gas passage and a ball-milled crank window rather than end-milled or broached, I was hoping for something that at least “looked” hotter.
Crank Window.JPG
Crank Window.JPG (26.35 KiB) Viewed 12412 times
The rear main bearing has a metal retainer. Let’s hope it proves more durable than some Chinese metal-retainer bearings at high rpm. A cheap upgrade/insurance is the RCBearings phenolic retainer bearing which seems to be very stout and is cheap.

Two fairly big disappointments. First is the use of a circlip for wrist pin retention vs. the teflon pads of the FX. I’ve had several combat engines (ST 29, Webra 25, and Magnum 28) which have had failures of the circlip- when one lets go, it leads to total destruction of the top end. The teflon pad system of the 25FX seems completely reliable and I wish Magnum would have copied it in this FX clone.
Wrist Pin.JPG
Wrist Pin.JPG (27.51 KiB) Viewed 12412 times
The second it the pressed-in crankpin. I have seen several failures of this construction in the Magnum 28XL, which has similar construction. The Mag28 seems to hold together forever at Limited B rpm, but at Open B rpm the pin tends to back out. Then it starts rubbing on the backplate and then engine binds up. Let’s hope the 25XLS uses better metallurgy and/or tolerances in the press fit, to avoid this problem.
Crank Pin.JPG
Crank Pin.JPG (27.61 KiB) Viewed 12412 times
Bench running was unremarkable. Engine runs great, the needle has a very broad range and seems leak-free, MUCH better than the 28XL. The engine was smooth and throttled well. It ran for about 10 seconds with the barrel fully closed, before finally dying. This seems to be a common issue with the 25XLS, some apparently are worse than this and won’t die at all. After 10 break-in runs my engine was running about 14k on the MA 10x4 Limited B prop, but it was about 40 degrees. RPM may improve at more “normal” combat temps. I did not test in OpenB configuration.

Overall I think this is a really nice engine and am looking forward to flight testing next spring. At less than $50 with shipping, it seems to be a great deal. I just wish I would have been able to snag some XLSs at the $40 Hobby People sale!!!
Scott Gilkey
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David Drowns
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Re: The XLS .25 Combat Engine

Post by David Drowns »

Great info Scott. You make me want to go tear down one of my XLS's to see what's inside now that we have the Hobby Partz insides on display. One is ready for 4th string backup if needed this weekend and the other one is wrapped up under the Christmas tree somewhere. (hmmm... :roll: . ya think she'll notice?) Naw can't do that. But now I know what to have an eye for. Thanks.
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Re: The XLS .25 Combat Engine

Post by David Drowns »

I got a chance to look at the inside of the 25 XLS and here is what I found. The pictures are not as good as yours Scott but you can see the same circlip used in the Hobby Partz engine but a much smoother finish on the piston.
Image

I wasn't able to remove the crank but it has the same rough finish in the fuel port.
Image

The piston sleeve with the ABC technology (Aluminum piston, Chrome plated Brass sleeve) can be seen here.
Image

But you can't get around the fact that they do back their engines and have done a fine job of responding to our needs for a good 25 size for combat. Mine ran great in the Pearl Harbor event when I finally put it in the battle. In fact I found myself backing off to 2/3 throttle to keep from flying right past my targets. That was until I had the last streamer remaining, then it was "Go with throttle-up!" and "Catch me if you can!" All with only the baffle removed.
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Re: The XLS .25 Combat Engine

Post by gsjames »

Mine haven't arrived yet, but I was looking at one that a local Q-25 racer just bought and I noticed something that might explain why some guys are having trouble with the engine not shutting off. On his engine, as received, I noticed that when the throttle barrel is COMPLETELY closed that a small "bleed gap" appeared at the right rear of the barrel. (viewed in flying orientation) This would be more than enough air to let the engine keep running. This bleed gap is controlled by the small screw on the right side of the carb, opposite the needle valve. As I understand it, this screw moves the barrel left and right and is the idle mixture adjustment. I don't know if this will help, but it's worth a shot.
Gary James
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Don Holmes
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Re: The XLS .25 Combat Engine

Post by Don Holmes »

My XLS .25 would not stop running for the first 2 days after running it in, it shuts down now .
Don Holmes RCCA #957
Mid Atlantic Combat
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