Triple88a

Hello all,

I've been searching around the forum for a while but could not find my answer. Basically i'm curious which will be better? A muffler with the stock exhaust manifold or a custom manifold with a straight pipe?

As you can see how my manifold goes down and then forward.. its pretty tight on its way down. My plans are to cut out a new manifold out of a solid aluminum piece that goes straight to the side right in front of the rear tire.


Any feedback or recomendations are welcome

Thanks in advance

SManMTB

Almost everything will be better than what you plan on doing.
The pipe is a tuned exhaust and it can be done better or worse. The black thing in the picture is an important part of it.
It looks like you can open that one up and look inside. If you do you will see the cones. There a re two, the front divergent cone and the rear convergent cone.

A straight pipe will not be better.

Triple88a

I have opened up the muffler.. its hollow on the inside and there is 1 round plastic piece (with 7 small holes.. 1 in the middle and 6 around it) that goes right where the 2 pieces of the muffler screw together. Everything else is a straight through.

j_blaze

I ran my speedy buggy without the round piece inside the muffler, little bit louder but WAY faster. You'll be surprised how much faster it goes then, almost like why did they put that piece in there?

Triple88a

I have also ran my buggy with out that piece. It died easier while idling but it did feel faster. i thought free flow was best and that exhaust manifold and that muffler doesn't seem really free flowing to me. The manifold is tight as hell on its way down and its all made of sharp bends so the pressure bounces off and doesn't flow smoothly, especially when it reaches the bottom of the manifold being that round end of it that connects to the muffler. The muffler it self also seems a bit wird since the air inside has to bounce off back to get to that hole.
Maybe i can make a dyno and test it lol.

I have quite a bit of experience with real cars that you ride in and go to the store but I'm new to RCs of that level.

proptop

My Feedback: (8)

The black plastic "pipe" is actually not that bad...just get a decent header for it and that will help quite a bit.

Triple88a

so a straight header isn't a good idea then? :P I'd try it but my header is pointing forward so that isn't really good when the car is also moving forward at full speed.

proptop

My Feedback: (8)

Our 2 strokes run much better with a divergent/convergent cone type tuned pipe.

See if you can make or buy a tubular header that bends down and forward to connect to your black plastic pipe...it's actually a tuned pipe/muffler, so it would not be good to run without it...you would notice a loss of power.

Something like the header in post #2 in this thread: http://www.rcuniverse.com/forum/m_6116192/tm.htm

The_Shark

yeah, i got my ofna cd3 but the header was stripped and warped so i just got a hpi muffler, its just a can with a pressure hose and a stinger. i notice i have to lean it more or else it really blows smoke and cant go over 30 and doesnt hit 2nd. i also ran it with the manifold pointing up and away without a pipe and it felt peppyer and about 10times louder.

what the hell? whats better? a muffler, a tuned pipe or nothing at all? i actually go slower with the hpi pipe and leaky manifold than just a open manifold.

proptop

My Feedback: (8)

A muffler is basically just that...it quiets the engine with usually a power reduction.

A tuned pipe actually helps power production, and has a pressure fitting for the fuel tank, which is something a straight (open ) pipe is lacking.

It takes some experimentation to find the "perfect" pipe for any particular application.
You have several variables to deal with, like what r.p.m. is the engine ported/timed for?
What type of vehicle is the engine in and how heavy or light is it?
What are your gear ratios?
What type of driving are you doing...bashing or racing...etc.etc.etc.

The_Shark

lets see, i rarely do WOT as i practice for racing soon. the ratio is pretty tall. the car weighs about 3lbs. practical rpms are 30k but max are 38k.

im guessing i need something that gives me torq because im not speed running.

oh guess what?? i noticed that this muffler made my car soo quiet that i could hardly hear it idel far away, i also niticed it made my car REAL slow, so when i got back i cracked it open, i look inside to see the baffle, there are no holes open except for the screw! i saw two pushed in dots, so i figured id just drill into them, i put it on a peice of wood and presed with the drill i heard a pop. i looked down and ther was a perfectly round hole.

i think this thing was mismanufactred, i cant wait to try it now but its raining[sm=tired.gif]

lsurber

The most important element in exhaust system is tuning. A properly tuned muffler is better than an inadequetly tuned pipe! It's just like tuning a ported sub-woofer.

The_Shark

well, i had the chance to drive the car and it streight up blows. the muffler chopps down the speed by half and makes it feel "spongie" and weak. i tryed mutiple tunes and the only way i can get good power is if i really lean it out and it wants to die, bogs, doesnt start easy, and cooks the engine up. i even removed the baffle and it still sucks.

i just need a new header and pipe.

The_Shark

i have good news!! due to my ghetto skills i fixed the pipe and muffler!!!
what i did is take the manifold that was warped and filed it down for 30mins, after it was smooth i rinsed it out. then i took the pipe and bored out the stinger hole, i then stuck in the silicone diverter thing in there with the ribbed part, that fixed the stinger. then i got two screws and on one side did bolt and nut, then the other part was trickey, the manifold is just a mm away from the hole, so i got a amature spacer and a lug nut to space the screw, then i had to cut a nut with some angle cutters and pounded into position, i bolted it on an there you have it!

i felt ISNTANT power and less lag. it feels more powerfull than before when i had a leaky manifold. ah, another day another $20 saved...

kevinsburns

I can't believe what I am reading in this old thread.
Tuned pipes are simple, really simply.
1) It is a sound wave "Shock wave" same thing, that forces the fuel back into the engines exhaust port just before closing the port. So the cones "The shape of the actual pipe"; as the hot exhaust and raw fuel exits the case via the exhaust port, the exhaust expands, hence why the first cone is longer and gets wider to allow the sound of the actual explosion, exhaust and raw fuel expand. Now once it hits the ends cone it compresses the exhaust and raw fuel, the sound creates a shockwave that bounces off the small cone and the shock wave pushes/sends the exhaust/fuel back to the engines case via the exhaust port. The shock/sound wave doesn't care how it get there either "Twists/bends etc.). It also doesn't matter what direction the stinger is pointing (Up, down, front rear). One last note; a few pin holes or leaks is not detrimental to the tuned pipe. Look at it this way there is a huge hole in the pipe anyways "The stinger" and a smaller hole the fuel pressure tap. Some engines run whats called "Throttle exhaust" The throttle exhaust sits right aft of the exhaust port before the tuned pipe and it controls the throttle, no carb just a venturi, opening and closing the throttle exhaust controls engine rpm much like putting your finger over the stinger. Anyways those things leak like a sieve but give 20% more performance than a standard carburetor. The exhaust throttle seen hooked to a K&B 3.5cc drum induction/not crank induction engine in a Dumas hawk Hydro I own.


By tuning the length of the pipe closer or further from the glow plug determines when the pipe will come on and that determines the rpm range and where one wants it.

2) They are called tuned pipes. What this means is the length from the glow plug to the widest part of the pipe determines when the pipe comes on "Getting on the pipe". The shorter the pipe length from the widest section to glow plug the sooner it will come on because the fuel charge has less distance to travel back to the exhaust port, and the longer that length is the later it will come on because the fuel charge has further to travel back.
The drawback to both is:
A short pipe will come on sooner good for holeshots out of turns (The engine wont bogg as much) but lacks higher rpms "bad for long straight aways".
A longer pipe will come on later but lowend will suffer "bad for hole shooting out of turns" (The engine will bogg slightly) but rpm will be greater good for long straight aways.

What you did by changing the header was change the length of the pipe, so much as 1/16th of an inch can drastically change a tune.

I run on-road in a nascar style oval so prefer my pipes on the longer side as I like to go fast down long straights and wide turns. If I were to run in a more on-road course with tight turns I would shorten the pipe to get on sooner out of the turns but top end would suffer.

Nitro airplanes and boats use very long pipes because they are not affected by throttle changes or really slowing down for turns so we can run those engines pretty much full throttle full out so higher rpm is easy to manage, where a car or truck/buggy uses the throttle more so the actual pipes are shorter and smaller.

Similar to full size auto race headers, the longer they are the later they come on, and vise versa. that's why they are called tuned headers.

Get it? I know this post is old but people do read this stuff.

kevinsburns

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kevinsburns

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kevinsburns

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kevinsburns

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1QwkSport2.5r

Long exhaust = lower timing requirement and lower peak rpm. Short exhaust = higher timing requirement and higher rpm requirement. Long exhaust=better torque. Short exhaust=better top speed. The manifold makes about 75% of the difference of how an engine “feels” as this determines the overall length and flow velocity. When matched to a good pipe, the manifold can make a blah engine really come alive provided the engine has the proper timing parameters.

Onroad manifolds are much shorter than off-road manifolds which is why they can rev so much harder. Any “U” shaped buggy and truggy manifold isn’t going to give as good of output as an onroad. So keep this in mind-for non-racing environment; run the shortest header and highest timings. Then you can mess with header lengths and find the perfect setup.