I have been designing and flying giant scale for a few years now. I have a friend that flies the Don Lowe Masters with a set of tuned canisters and a 3 blade on his rig.....40% Comp.Arf. Is there a distinct advantage to the stock type cans the TOC boys always use for freestyle/3-D ? My old,heavy 3-w 150 likes the stock , noisy cans. Always ran lean on tuned canisters at start up. I am not looking for a "your engine is lean/carb leaking" answer as this is not a problem. Looking for a competition solution....untill then I'll keep burning jet A. There must be a reason for this at the major events...very few tuned canisters in big birds.
C'Ya at the Nall

Tuned cans require tuning. Not everyone has the skills to get it right. The header length has to be matched to the engine and prop. Done right, you'll get more power, good throttle response, less noise, more weight, more cost.
Done wrong, you'll get less power, poor throttle response, less noise, more weight, more cost, a hotter running engine, and broken headers.

In-cowl mufflers are the set it and forget it approach - requires no fiddling and a lot less planning and testing. Also have the advantage of lower weight, less cost, and more durability. You can't win a contest with a broken exhaust.

If you want all the advantages of tuned cans with a little less headache, expense and weight gain, look into the new Greve pipes offered by DA. Bernd Bershorner was running them at Tucson last year and the seemed the perfect balance of all things good, quite (extremely), light, no mid range issues (that I could tell) and they are shorter and smaller diameter than the KS 1090s so install should be pretty simple. About $550 for the cans, headers and mounting brackets.

Almost none of the "big guys" are running stock canister (in cowl) muffelers now, just too loud. I've been running MTW cans for about 2 years now and love them. They give some performance gain, make the noise level much more tolerable and are easy to set up adn forgiving to "tuning". There is a balance between upper and lower needles that has to be struck to make the midrange just right, other wise you can get a surging, but it's fairly easy to hit the sweet spot.

Kev

So what is the correct way to "tune" the cannister?

I would like to know this as well....I have the can setup from Gerhard {pefa} . The headers have a step that prevents alteration, as well as the canisters themselves. May be able to shorten 1/2" , but no more. Seems they should be "close" tuned for that specific engine size. I could understand if it were like cutting a pipe for a 2 stroke. But in my case there is'nt much of an option....considering putting stockers back on. You can't fly it like you stole it unless the engine will be there for you. Try a torque roll at 6 feet with a questionable engine....Nervous yet????

Oh btw a recent ground run revealed a high temp of 147 deg F after 15 minutes of full power......even cooler at lower rpms. Checking exhaust temps are tricky depending on where you take the reading....nothing to be worried over.

Headers: $150
Tuned pipes: $300
Time to install: It could be into the millions?
Keep'in it simple with stock mufflers: Priceless!!

I will admit that when they are installed right and tuned they do work well, but for the time and money involved I will most likely go back to stock mufflers.

Guys,, "Tuning" a pipe goes back to the .60 pattern engines. The Length of a full wave pipe is critical. We did a ton of testing with a specific prop,fuel combination to get supercharging affect working correctly. It was much like a needle valve. When you had a full wave pipe in tune you could see pretty good RPM increase. Length from glow plug center to the high point of the pipe USED to be gaurded info!
Gas engines,,,, I know of only one true "tuned"(full wave) system on the market for our application. All of the rest are simply cannisters. There are given lengths recomended, but volume is king! Don't fear these things guys,,they're bolt and roll pieces of equipment. Once you get used to a quiet set up you can never go back to cackleing. They are really easy to work with. Another plus is getting heat away from the cylinders. Stock cans are mass next to the cylinder, heat. Headers are the minimum mass, there is a temp diff,, not huge but less.
I wouldn't have a plane without them! GO FOR IT!!

Biff's right on with this one, once you have a plane with them, going back to the old way is just out of the question. The Pefa, MTW and short KS are not "tuned" per say. However, if you get them too short, you'll have mid range transition issues, you'll get "surging" at half throttle which is annoying and will make speed critical manuevers more difficult (like rollers). With that being said, I've always followed DA's recomendation on header length (10.5" minimum) and mine have all been phenominal. Instalation is very simple for most planes and it will make a one piece cowl much more user friendly because you don't have those huge stacks coming out of the bottom of the cowl. The front exit cans exhaust out the more scale location in the normal air exit in the bottom of the cowl, so you simply remove the prop, un-bolt the cowl and slide it off.

It's also a nice jab back at the guys who used to give us grief about "those damn loud gas planes" now we make less noise than their planes. If your flying anywhere near a residential area, it's the right thing to do to protect our flying fields.

As for tuning the actual "tuned" pipes like the KS 1090's, you start off with the headers really long and cut them off until you get the desired effect. In the good old days of the 2 stroke .60 on pattern days, the name of the game was top in RPM so we would cut the headers 1/4" at a time until the rpm peaked and dropped off then back the pipe up in the coupler 1/4" to get the max RPM. Now days mid range and transition is much more important so you'd have to cut it, fly it, cut it fly it, and keep going until you got good power with smooth throttle response. Thankfully there are lot's of people who have figured it out and are willing to share what they learned, so the information is easy to come by.
Kev

Thanks Biff & Kev. This had me confused??

OK, You guys have convinced me to keep the cans in the hole. I do like to hear the prop wash on downlines. Now back to the original item at hand...why is this thing lean at startup? I mean you can't even think of touching the throttle stick. After a couple of minutes it will allow you to do a run-up. Still afraid to hover down on the deck.....lost a bird a few months back due to this engine problem... leaned out in a hover and quit @ 15' up. So I got a brand new carb and phenolic plate from Gerhard and absolutely no difference !!!! Reeds are new as well. Fuel is 80 octane and lawnboy 2 cycle.....on new plugs after a couple of "regular" flights to get a plug reading. Very slight deposits with 30X magnification. Also tried another ignition.....no change. Almost ready to trade it for another turbine..........my 100cc runs like a raped ape.....on cans! Thanks for all the info......

I'll keep the 1 and a half extra lbs on the bench and 500+$ dollars in my wallet..

As far as the "big guys" go , I didn't se any tuned equipment on the 4 cyl.DA200's at the Shootout that took most of the top finishing spots..


Dave

Unless there is a specific reason to fly with cans, why use them...??? I have a set of 3w's and they weigh out at 34-ozs. uninstalled. Why fly with all the extra weight...??? They now sit in the cabinet in a quiet manner.

Eventually, we will all be forced to fly with noise suppression but until then, why do so..??? , V.

Originally Posted by Vtailman777

Unless there is a specific reason to fly with cans, why use them...??? I have a set of 3w's and they weigh out at 34-ozs. uninstalled. Why fly with all the extra weight...??? They now sit in the cabinet in a quiet manner.

Eventually, we will all be forced to fly with noise suppression but until then, why do so..??? , V.

V. We are under noise restrictions in Ohio and other states around us. You learn to change props to manage the addition of weight, without power loss.

Kitman

Originally Posted by FlyAlot

I'll keep the 1 and a half extra lbs on the bench and 500+$ dollars in my wallet..

As far as the "big guys" go , I didn't se any tuned equipment on the 4 cyl.DA200's at the Shootout that took most of the top finishing spots..


Dave

Dave,
one of those (only 3) LOUD planes cost another contestant (a very big name) an unknown round at the NATS because of the ripping to show off. They've also cost many people their flying fields. I don't think being loud had anything to do with who finished higher at Tucson, nore did the wieght saved from not using cans, ewspecially since the 200 was heavier than a 150 with cans (granted the extra power is a plus, but the plane is still heavier). And 1.5 lbs could be at least a little exaduration. If your flying in the middle of no where, great, knock yourself out, save the money and the weight, and stick with the stacks, but if your coming to my field, PLEASE do me a favor and figure out a way to quite down your set up. For someone who wants to travel for IMAC contest, you never know the situation at some fields until you show up, just seems the reasonable thing to do is attempt to be as quite as possible.

Kev