engine for 2548 / limited B?

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Bad Dawg
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engine for 2548 / limited B?

Post by Bad Dawg »

I am just about to order an engine for my 2548 P-39 and saw the GMS .25 on the Tower web site. Has anyone tried one? According to the mfg. (I take most of what any mfg. says with a large grain of salt) it weighs a tenth of an ounce more than the 25fx, has a hundreth of a HP over the 25fx @ the same rpm, and the same basic rpm range. A little more weight and torque isn't going to hurt a 2548 plane, and my wallet wouldn't complain about shelling out $30 less.

I consider the 25fx the gold standard for combat because of its ease of use and consistant performance, and if the GMS is as easy to run, I'd settle for a little less performance.

NUNC AUT NUNQUAM
Mark V.
The perpetual 'newbie'
BigCountry
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Post by BigCountry »

Mark,

I know that Jimbo had a couple of them that he was going to try to run for Open B and ended up putting them aside for some Irvine's. I know that he wasn't really impressed with much about them. I've also heard folks that have really liked theres but I think those were bigger engines for more sport applications.

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Cajun
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Post by Cajun »

I have the GMS.25, and while it is a good engine by Chinese standards, it ain't no OS. I ran it for a while in B and it does OK with a mousse can, but it has the same issues as most Chinese engines; Crapy carb, poor QC, and air leaks. I like the Mag.28 and Norvell bettter, and I don't even like the Norvell[xx(]

CAJUN [8D]
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Rabbit Leader
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Post by Rabbit Leader »

Mark, I have flown the OSFX, and both the Norvel plain bearing and ball bearing 25's. The OS is the benchmark, to be sure, but the Norvel plain bearing pulls the 10-3 within a couple hundred rpm of the FX, and is lighter to boot. The NorvelBB turns a bit less on the ground, but unloads well in the air. Only problem I have with the ball bearing engine is that it really unloads in a dive with a clean airframe, and doesn't hit the pitch "wall" as fast as either the OS or it's plain bearing sibling. I suspect that the ball bearing engine is hitting it's advanced porting on a downhill run, and it just takes it a bit longer to slow down to the usual 2548 speeds. Not a big deal, my 109 isn't much faster than any of my other ships in level flight, or in dogfighting, it just hauls butt in a prolonged vertical dive, which I do a lot when I want the guys at my field to wake up....[:p]

BTw, I took an old, fairly worn out 25FP that was bone stock, with the exception of a 35FP carb. The baffle is still in the muffler, and the stinger has not been enlarged. I ran it on some fairly old fuel, around 15 percent give or take a few months time, at around 85 degrees and fairly high humidity, and she turned a 10-3 at real close to 13,000 RPM. Now, I know thats 2500 rpm less than our max rpm limit, but I think that would still fly a 2548 ship okay, if it was built close to the minimum weight and was of a clean design..(109, P-39, etc). I THINK I heard someone say that the LA series of engines run stronger than the FP's did..might be feasible to get 14000 plus out of one with the baffle removed on 20 percent, on a good day, that is..

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Jimbo
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Post by Jimbo »

(I had two)The GMS.25's were the worst .25's I have ever had. I could right a book on all of their problems. Tower took them back,no questions asked. I have heard better things about their larger cid engines but these are just BAD.

Limited-B
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smelyal8r
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Post by smelyal8r »

I had two GMS .25s myself and after running the OS 25fx, I got rid of them both. They can't hold a candle to the O.S. in the power or consistency dept. Go with the O.S. if you want a motor that will fire up right away and run perfectly every time.

Brett "Smelyal8r" Sugamele
Colorado Springs, CO
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Bad Dawg
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Post by Bad Dawg »

Thanks guys. It's really the running ease I am loopking for in a 2548 engine. I have one 25FP, six Norvel Big Migs and five or six FX's. The FX is the best. I was just feling cheap and lazy. That's why I was looking at the GMS, but I don't want to repeat Jimbo's experience.

NUNC AUT NUNQUAM
Mark V.
The perpetual 'newbie'
Jimbo
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Post by Jimbo »

On 2-13-04 I wrote a review here. Look at "Engine Clinic" under "modifications". The topic is: "GMS.25's My review" I have all the gory details there.

Limited-B
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Serg
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Post by Serg »

I do have GMC 25, 28 and 32
25 can not be compared with 25FX. In direct comparison it loose (even it is chipper)
32 works better, but it out of rules, and before getting good result you have to work with him a lot... Final conclusion is simple as 1+1. I came back to 25FX.
Rabbit Leader
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Post by Rabbit Leader »

Shoot, Mark, sounds like you have a bunch of Merlins, Daimler-Benzes and at least one Allison in your supply depot! I'd say your'e good to go....

"Furballs are for cats!"
Rabbit Leader
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Post by Rabbit Leader »

Anybody tried one of the new Thunder Tiger 25 ball bearing engines? I had one of the older, round head engines, and it didn't run worth a hoot. In fact, my old TT 25GP plain bearing would run off and leave it. I may have just had a bad engine, it does happen from time to time, but I have a hard time believing that a company that puts out such a strong running 46 couldn't do the same with a 25...any info?

Cash

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Jimbo
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Post by Jimbo »

Travis had two of the old TT.25 ball bearing engines and they had very little power. The carb was very small on that engine. I sure wish they would do some changes to that engine because the .36 and .46 are very strong engines.

Limited-B
Try it,you'll like it !
sgilkey
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Post by sgilkey »

The TT PRO .25 (ball bearing engine) is a DOG, the plain bearing engine will out perform it. I have seen several TT PRO25s and they are all weak. You did not have a bad one!

Scott Gilkey
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