TT GP-42 vs OS LA 46
 

Hello all, I'm currently building a low wing sport plane of my own design which I hope to have finished in a few weeks. I ordered a Fox .40 bushing some time ago from Fox but it still on backorder with no delivery time in sight... I am thinking of buying another 40 engine to continue progress on the nose section of the plane and saving the Fox for another project. I have a strong preference for bushing sport/type engines because of their easy tuning and low maintenance nature. The plane should be pretty light at around 3.5-4.0 pounds with about 500 sq" of flat bottomed wing.I have narrowed the choice down to between the LA .46 and the TT GP .42 (actually a .40) Specifically, I have 2 questions for those of you who run these two currently....1) Is the OS LA .46 still made in Japan? I notice if you look at the picture on Tower's site, that you can't see JAPAN on the crankcase like the pics of the other size LA's show. I refuse to "reward" a manufacturer with a sale if they've outsourced a product for cheaper labor, regardless of what it cost me to buy. And, 2) Regarding the GP-42.... I only have room for a six oz. tank in the nose with enough room for a little padding around it. Would the Thunder tiger have a lower fuel consumption than the LA being a smaller displacement? It does have a boost port that the LA does not have... This freer breathing makes more power per displacement but might take more fuel? I was thinking that fuel consumption might be similar between the two as they both should put out a similar horsepower. This might be especially true if the LA is run with an 11-5 prop vs the GP's more appropriate 10-6 or 10-5.Please, Let me know what you think.... Oh and please go easy on the OS bashing... I've had superlative luck with all of mine for thirty plus years now, almost all of them bushing models with air bleed carbs. The T Tigers on the other hand I've never owned. Thanks in advance for any replies. Robert, (WoodCutter)

RE: TT GP-42 vs OS LA 46
 

I have number of .40 and .46 LAs and TT .42GPs. Like you, I like the bushing engines for ease of use and maintenance. I prefer the TT 42GP to the 46LA as I get more power from it on the props I use )11x5, 11x6 and the 5% nitro fuel with added castor oil that I also use. I have never had a peeled liner in the many TT engines I've used but have experienced two instances with OS liners. I am at 200' above MSL. I use a 6 oz tank with my TT 42 and it gives me 10 minutes+ with the type of flying I do.

RE: TT GP-42 vs OS LA 46
 

My understanding is that the LA 46 will have more power with large props and the TT 42 on small.  Never had either but I have owned several TT engines and they are equal or better than OS execpt for one issue.  Sometimes they don't tighten the screws as they should.  Also the carb is not preset. 

But TT is from a free republic nation.

RE: TT GP-42 vs OS LA 46
 

I prefer the Thunder Tiger engines. Ihave run several TT engines and love tham all.

RE: TT GP-42 vs OS LA 46
 

I have a .46 Pro and love it, a buddy has a GP42 and likes it.

RE: TT GP-42 vs OS LA 46
 

Thanks all for the replies. It sounds like the GP-42 would be suitable...Still, before deciding on ordering one of those, I still would like to know if the current manufacture LA .46's are made in Japan. Also, I was under the impression that the liner peeling issue was more confined to the higher powered more highly stressed OS's like the FX and SX series. None of my FP's (multiple) or the LA .15 that I have run have had any problems with their liners.

RE: TT GP-42 vs OS LA 46
 

Don't forget about the K&B 45 Sportster. Can find them new or slightly used on here and the auction sites for less. Similar engine (bushed) and air bleed carb. The 3 or 4 I've had over the years have all run great. Little larger cylinder and muffler than the others if fit is tight though.

RE: TT GP-42 vs OS LA 46
 

The K&B Sportsters are good engines, but require a lengthy break-in to be really reliable.. At least my .65's were. The carb is not an airbleed type (if its factory K&B or Perry). The K&B carb is like a Perry where the idle mixture is adjusted with the idle disk which is controlled by an eccentric screw only allowing about 2° of adjustment on either side of rich/lean. High speed mixture is of a traditional needle and fixed seat.

Like many bushed engines, they really like to have 20-25% castor oil content, no synthetic. Especially during break-in. I ran synthetic blends in my sportster, but I get better top rpm with it on 25% castor. I'd bet you could find a used one for $30-50 with box and paperwork.

A Super Tigre GS40 or G51 would be strong runners as well. The 40's come ringed or ABC and the 51's are ringed. These would require less bench time than the Sportster would.

RE: TT GP-42 vs OS LA 46
 

Mine were bleed type carbs, if I remeber correctly. I'm talking when they came out about 20 years ago, without the remote needle.

RE: TT GP-42 vs OS LA 46
 

I agree that the K&B .45 would be great. I've enjoyed using the couple that I have had. This might sound strange to some of you, but I was really wanting to buy something new. The way I look at it, the glow engine market is gradually shrinking. If not enough people buy engines new as well as used, then manufacturers will only continue to drop more models from their lineup. Mecoa still sells the .65 and .28 Sportsters but the .45's are gone....No it's going to be the OS .46 or the TT .42 . That is unless Fox gets their wonderful bushing .40 to me before I place the order.

RE: TT GP-42 vs OS LA 46
 

My .65's are of that vintage - non bronze bushed crankcases. Factory carbs are not airbleeds, and neither were the Perry's.

RE: TT GP-42 vs OS LA 46
 

G'day I have used both and liked both. I am using an OS LA 46 at the moment in a World Models Skyraider trainer and a friend is using one in a Sig Kadet LT-40. Both work really well. Very easy to start, minimal running in, economical and powerful enough.

I am also a fan of Enya engines which are available from Ken Enya in Japan at www.enya-engines.com Ken replies quickly to emails and has a great stock of parts for his engines. His SS40 W/SNV is a plain bearing engine of similar specification for about $129. This engine uses the older iron piston/steel liner which needs some running in and castor oil but these engines last for ages. I had a worn one from years ago but he was able to provide a new piston and liner for only $35. Enya engines are of particularly high quality and are known for being very long lasting.

I have had a LA 46 which had a worn liner. I suspect it was fed a "high silica diet" ie lots of dust before it came to me. A new liner cost $49 which is expensive but not too bad. Better than $95 for the piston and liner for an AX 46.

Cheers

Mike in Oz

RE: TT GP-42 vs OS LA 46
 

Robert, I have two LA .46s and both are jewels. One is converted to Davis Diesel operation, the .46s make a fine Diesel or glow engine.

RE: TT GP-42 vs OS LA 46
 

Is the TT .42 really a .40???? It's somewhat amusing - a friend of mine bought a pair, which were going to be used for CL Stunt. He was lamenting the "fact" that they were over .40, so he had to use the heavier .018" lines rather than .015". Maye he needn't have worried..?? As it turns out, all the competitive guys use .018s on .40s anyway, because they're more precise - less line stretch.

Iskandar

RE: TT GP-42 vs OS LA 46
 

The TT site specs the engine at..421 square inches.</p>

RE: TT GP-42 vs OS LA 46
 

I'm another pilot who has flown both and really likes both the O.S. Max .46 LA and the TT GP-42. With two engines like these that are readily available, affordable, reliable, and powerful, it's a wonder that some folks actually bother with electric aircraft.

RE: TT GP-42 vs OS LA 46
 

I was told the GP42 is supposed to be a ".40 series 2" or something of that effect.

RE: TT GP-42 vs OS LA 46
 

No. the 42 is actually .42 displacement, thus the 42 in the model number.

RE: TT GP-42 vs OS LA 46
 

I seem to remember a post where someone (I think it was Jeffie) fed the Bore and Stroke dimensions into an online displacement calculator and the thing said .396 Cu." for the GP-42. But I may be remembering it wrong..... WoodCutter

RE: TT GP-42 vs OS LA 46
 

I do the calculation by hand and I get .4195.</p>

RE: TT GP-42 vs OS LA 46
 

Thanks Sport pilot....WoodCutter

RE: TT GP-42 vs OS LA 46
 

I have owned a ttgp-42 since 2000 and I had it on a Kadet LT-40 and learned to fly with it. Engine has been to hell and back and I have never replaced anything. I run Byron's 15% with a fox miracle plug and it always fires right up. Never owned a OS and probably never will since I got the TT and 2 evolution .46

RE: TT GP-42 vs OS LA 46
 

I get .3964618. Doing the calculation with a scientific calculator.

Regardless of what the displacement is believed to be, it would be a good running engine.

RE: TT GP-42 vs OS LA 46
 

Pie (3.1416)  R Squared times stroke.</p>

RE: TT GP-42 vs OS LA 46
 

Ithink the differences are in the published bore and stroke data. I remember vaguely doing it a while ago and found it was actually .42 like they said.
I think there was some erronious data out there, probably a cut and paste publishing problem.