jester_s1

I couldn't resist messing with a perfectly running engine so I pulled the baffle out of my TT .46 Pro to see what difference it would make. With a 10x7 on 20% Omega fuel I was getting 13140 rpm peaked on the ground with a #8 plug. After taking the baffle out, it peaked at 13030 for a loss of 110 rpm. Then I went to a 10x6 with no other changes and got 15040 rpm with a 300 rpm lower idle. With the baffle back in, it got 14570 with roughly the same idle but worse acceleration. So the results of this tiny little experiment show me that with this engine and this fuel, the baffle actually improves horsepower if you prop the engine on the heavy side and need torque, while it hurts horsepower when you prop it to run fast.

Does anyone have tips to get any more out of this engine aside from buying a tuned muffler? I fly SPA with it and am very happy with my Kaos and the way it flies, but if I can get some more free horsepower I'll take it.

Ernie Misner

For an experiment try the mac's muffler made for the OS 55AX. It has extra volume over the 46 size muffler and really makes the 55 scream.

Let us know if you do try it, thanks,

Ernie Misner

airraptor

My Feedback: (66)

Ernie i heard there are two different macs muffler one is very light weight and robs the engine of more power than the stock muffler.

I know on the OS AX engines taking the baffle out you gain power. The 46 AX will spin the APC 10x7 at 13,800 on stock muffler with baffle out. The best bang for the buck is the Tower/GMS muffler. this will giv you 500-800 more rpm back over the stock muffler. You can get them from Meccoa for 20 bucks. next besst IMO is the Jett muffler.

Ernie Misner

Yeah, that used to be true of the mac's mufflers but definitely not the case with the extra volume one for the 55 nowadays. I have a few now, night and day difference. They are all about the same weight, real light compared to the stock muffler, not 2 different weight versions that I know of. I've always wanted to try this version on a .46.

Thanks,

Ernie Misner

jester_s1

Well I'm impressed with the engine as it sits and probably won't spend any money on it. If I do, I'll go ahead and get the Jett muffler and probably wind up around 17k in the air with that gurgling midrange I hear at all the SPA matches. If I could coax a little more power out of it by tweaking glow plugs or head shims I'd do it, but I'm not inclined to mess with it before hearing from someone who has done it before.

1QwkSport2.5r

I have an older pro 46 (straight needle valve) and running 5% nitro 20% castor I get 16,800-17,000rpm with the Jettstream (red) and APC 9x7. Every 5% nitro I add I gain about 200rpm. I broke it in too slow (didn't know any better) so its down on power. I get 15,300 to 15,600 on 10x5 or 10x6 APC props. To get the engine really on the pipe, it has to be propped for 15,500+rpm.

airraptor

My Feedback: (66)

quicker the Jett/evo Blue muffler has a lower tunning range around 15,000 and it might help you some. Also for the jett mufflers it helps to put a angled flat on the corners of the muffler to match the engine. dont take to much metal away trying to get a perfect port match as you will lose power.

1QwkSport2.5r

From what I've gotten from Bob Brassel, I'm going to say no. The port is the shape it is for a reason. I don't care about 50 more rpm. Im not running my engine so lean and so fast just to get a few more rpm from it.

Your "super" FX is on its way back to you finally. Don't send me another one, either.

airraptor

My Feedback: (66)

qwick dont be a jerk. I didnt send one of my "Super" engines. I sent one that ran strong when i sent it to you. I dont know you at all. For me to send a engine to a complete stranger i didnt want to send one of my best engines because i wasnt sure if i would give it back. I have only tried to help you this whole time. I see your attitude isnt very receptive to my help so you will no longer get any. And by the way doing as I stated on the Jett mufflers will gain 300-400 on all OS, magnum, TT and ASP engines. Good luck on your engines there.

And yes the Blue muffler has a lower tunning point over the red muffler. I have had all of the Jett mufflers apart. I talked to Jett about the mufflers not lining and matching the OS type exhaust ports. he said it doesnt matter either but it does maybe one day if you get around to testing all the different Jett mufflers on engines and trying diiferent things you will see and know what I know about these things. Also over time the Red Jett mufflers have changed internally. some have different length mid pipes and some have different size outlets on the mid pipes. I also know all the failure points on the Jett mufflers and how to fix those areas.

I was never going to send you another anyway after your other comments I could see you whole intent was to try to disprove my stuff. I will get more video up on the other tread to show what a "super" 46 can do.

airraptor

My Feedback: (66)

jester and ernie. here is another great muffler if you every want a high RPM sport engine in the 40-52 size range.

http://www3.towerhobbies.com/cgi-bin...&I=LXFW05&P=SM

The price has went up some on those mufflers. These were designed by Super tiger prior to the Jett mufflers. They are of the same design as they are 1/4 wave pipes. They do have a problem in that they dont last as long as the Jett mufflers do. The internal pipe will fall out after one season of so. These used to be 29.00 dollars. i have a fix for these also if you ever buy one let me know and I can tell you how to fix them.

i forgot to add this muffler is close to the Jett Gold muffler and black SS one.

1QwkSport2.5r

I'm not being a jerk. I wanted to see what your miracle engine guy could do because i give everyone the benefit of the doubt. It turns out he does what every other backyard engine modder does. Use a dremel to open/modify ports. I can do the same thing. Why would I send my engine off to have someone else do that when I can save the shipping costs and do it myself?

You claimed that FX ran 17k on a 9x8. It eventually ran 17k on a 9x7 on 5% fuel. That tells me either there's a little voodoo involved, or it needed 20% nitro. I don't know... Thanks for the opportunity to test it out though. It gave me something to do.

There is more to it than just rpm.

I appreciate all of the info you've given and getting to test an engine. I guess I had higher expectations. My bad.

Btw: you had nothing to worry about in regard to getting the OS back. I can't stand OS engines and had zero intention of keeping it. I wouldnt want the liner to peel or blow a bearing out in a gallon.

airraptor

My Feedback: (66)

As those FX engines are known for it may have just started to peel when i ran it here before i sent it out. Yes it did run 17,000 on a 9X8 APC prop. In your post here and the other it seemed like you were quick to post how bad it ran. Yes any one can take a dremel to an engine. but we have done close to 1000 engines. we know what works and doesnt. we can tune for torque or rpm.

1QwkSport2.5r

That engine smelled awful when I unboxed it. Smelled like it was soaked with burnt tranny fluid. Anyway, it's no big deal. I'm out $12 and a tank of fuel. It was worth the experiment.

airraptor

My Feedback: (66)

LOL it was fresh transfluid. i got the engine today and just ran it. i got 17,500 dead even on the the same 9x8 prop on red muffler so it is donw on power from before i sent to you. I will tear it down tomorrow to find out where the problem is.

1QwkSport2.5r

Your California weather must do it justice because it struggled to get 17k and that was absolute peak. I even richened to 16,500 for a minute and re-peaked it and I got the same reading. I was using my Hobbico tach which always works well and gave repeated readings.

I did notice before installing my red Jett muffler, that the oil stains on the piston didn't look right. I then realized how much you opened the exhaust. That thing has to have a huge blowdown period and subsequently lower trapped compression ratio. That makes for a good top end but I just couldn't pull your numbers. I don't believe in stuffing tons of nitro in anything but by the looks of it, it could probably handle 15-20% nitro.

Anyway, I'm glad it got back to you safely. Thanks for the opportunity.

airraptor

My Feedback: (66)

Its set up for 5% nitro. i ran it today on 10% nitro and 16% oil. no worries once i pull it apart i will see whats going on. I think that one was set up for.110" blowdown. most of them that start to run bad will show on the boost port side with some fuel wash.

I put a tower muffler on it and it pulled 16,800 on the 9x8 also. usually for these (what we call a stage 2) lol that is about right where the jett will add about 1000 or so. I do have my Jett mufflers with that angle I talked about earlier.

Ernie Misner

That ST muffler is interesting. Same exact bolt pattern as the OS, TT, etc? I had no clue that existed. When I was talking about the mac's muffler I forgot you guys go raacing and are after every last rpm. You guys are the best.

Ernie Misner

asmund

Yepp, that ST muffler looks very interesting indeed, I never knew about it either, thanks

earlwb

Well some food for thought is that 10qucksprt2.5r is at approximately 810 feet elevation there in Minnisota, but arraptor is at about 43 feet elevation there in California. Also heat and humidity (and barometric pressure too as various fronts roll through) can change the effective elevation as much as 4500 feet too. So it will be difficult to impossible to duplicate the performance numbers that someone else gets. Plus the specific prop that one person uses versus the other has a big effect too. Even if both people used the same brand prop, the props can be different. It was worse with wood props before the plastic props became common, as the pitch could be slightly different from prop to prop even if the props all came in the same bag from the same manufacturer.

Years ago when I was younger, it used to bother me a lot when magazine articles and plane kit suggestions stated that you could use a certain engine on a plane and it flew great. But when I lived in Arizona near Phoenix, the plane would barely be able to get airborne and lumber around ready to stall and snap roll with that same plane engine combination. I remember the guys in Colorado had it even worse being much higher in elevation too.

Here in Texas we have 100 degree F plus temperatures and the humidity is 50% to 60% most of the time, more when it is thinking about raining. So the effect on the engines and planes is very noticeable.

I think the real airplane people, drag racers and other racers have charts and graphs (along with copius notes too) that detail the effective air density at different elevations, temperature and humidity. Maybe even spreadsheets and computer programs for it nowadays. The racers have to change things a lot to maintain that peak edge on speed and power as the conditions change.
Here is some more on it
http://www.chevyhiperformance.com/te...ing/index.html

1QwkSport2.5r

Thanks for posting that, Earl. I figured the climate had to have a lot to do with how that engine ran for me. One other thing that I have noticed when comparing engines or even the same engine's rpm readings from one run to another has a LOT to do with the glow plug and fuel used. I get far better results with one brand/heat range plug in particular, but the biggest factor is fuel used - mainly the oil type and content. My main test mule is my .46 Pro Thunder Tiger engine and it easily gains 300-500rpm if I drop the castor content from a full 20% to 10% and add 10% synthetic oil for a 20% total oil content at a 50/50 blend ratio. Since I run most of my aircraft engines on airboats, I stick with full castor in my fuel to give me the best chance of preventing rust and corrosion in the engines. If I wanted to get max power from the engine, I would run an 80% synthetic/20% castor blend but the need for using ARO in my applications is a must with that oil ratio in the fuel. The engines perform well on full castor, and it smells better than synthetic oils do so I prefer to stick with it as much as I can. A friend told me it smells like barbeque, but I think he might have had a few too many 12oz adult beverages that day.

Nonetheless, when I tested the modified 46 FX against my TT 46 Pro using the same exact plug, fuel, and prop, I got very similar results. The FX edged the TT out only by a hair. Moreover, those readings I got were absolutely peaked. The engines were running hot and the oil was very dark coming from the exhaust. I would never run the engines that lean in service. When in service, I set my carburetors so there is an ever so slight load-up in the midrange and top rpm is about 400rpm off-peak so the oil coming from the exhaust is dark brown.

One other thing to note; 2-stroke engines thrive on the proper expansion volume of the muffler/pipe assembly. I did some testing with my Enya SS30BB engine last summer and as I had posted in that thread, adding extra volume made a significant difference in power output of that particular engine. I tested the .46 Pro muffler adapted onto the SS30 with the baffle in place and noted a 1700rpm gain over the original Enya muffler on a 9x5 prop. Every other prop I tested it gained a significant amount of rpm, but as the load went up, the rpm gains went up at a slower rate. The highest prop loads netted the lowest gains. I may test it again without the baffle in place and see if the engine gains any more power or not, only as an experiment. I am also working on putting together a MCP to use on my SuperTigre S90K to gain a little power.