Question bout mufflers...

[Half-breeder]

I have seen designs, concepts, and reasons for said ideas(different intake needs a different exhaust... to work properly). However... I was tossing the thought around of making my own 'muffler'... but 'just' for appearance and functionality... no 'reason' other than that.

I know that the 'factory' exhaust is quite restrictive... I know if the intake is upgraded and the exhaust upgraded the jets need upgrading as well... What I am wondering is what if 'just' the exhaust is upgraded and the intake kept factory... would 'anything' (other than the exhaust itself) need to be changed? Will 'just' the exhaust upgrade cause the motor to 'react' differently?

I used to make suppressors(for rifles), that were quite effective... coughcough...and knowing that a straight flow muffler is 'less' restrictive than a conventional designed muffler... was wondering if the lessening of back pressure would effect the HF212 6.5 clone w/ 'nothing' done to it(even has the governor!).

This is the 'design' but there will be a 'twist' to the method of my madness if I get the answer Im looking for...

 

[danssoslow]

Short answer: let the spark plug tell you what the engine needs. Use this picture as a guide.

If the plug appears rich after the exhaust mods, lean the mixture or go for less restrictive air intake mods. If the plug appears lean, enrich the fuel.

 

[OzFab]

Let me try to answer that with a story... (wow, I can already hear the whines of "here we go again" )

A few years ago, I had a car very similar to what's known in North America & Europe as a Ford Escort. After fitting a competition level sound system into it, I found I could no longer hear the engine so, I decided to change the exhaust from the 1 1/4" pipe with a single muffler to a straight through 2" with a single resonator from the catalytic converter back (stock manifod & header).

With that change alone, I noticed an increase in torque, not much but, enough to know something had changed...

IMO, changing nothing but the exhaust will not affect much, it may run a little lean (because the jet can't supply enough fuel to keep up with the faster exhaust) but, that's about it...

 

[danssoslow]

Lessons from experience always carry stories. For those that like it short and sweet, there's always wikipedia.

Btw, I'm a Chevy man. I'm jealous of some of those Holdens you guys have.

 

[OzFab]

I'm a Chevy man.

Me too! Give it a year or two & you'll have no reason to be jealous... Besides, you have some of them over there too...

Technically, the Ford was a rebadged Mazda

 

[danssoslow]

Some have. Hell, that platform the Camaro and CTS is Aussie derived. We had the GTO; but I really, really wanted to see the El Camino come here. Lutz tried like hell; but alas, no dice.

 

[OzFab]

I heard the deal was struck for 20,000 units; are you saying it never happened?

 

[danssoslow]

The El Camino? No, never did.

And Lutz has been out for a good while. Personally, I think he was the General's chance at a Iacocca. Wasn't to be. Bad economomy and a look towards a greener future, and now we have the Volt. :rollseyes:

He did leave us with the Solstice and Sky. Which, with available LS engine kits, can be the Fiero that the Fiero never was. There was word that the Fiero was going to recieve Buick's GN 3.8L turbo for '88; but Pontiac layed the car to rest in '87. How badarse would that have been?!?

 

[DeathStarr89]

OP, your design is a standard glasspack (various materials can be used instead of fiberglass). They are supposed to trap the higher frequency noise and let through the lower ones while not restricting flow.

Honestly (and I've been building exhaust systems for cars, trucks and small engines for a long time) glasspacks aren't that great for sound control. Part of their drawback is the physical case size.

Look at a cutaway of a magnaflow muffler, it's the same idea as a glasspack but with a larger case and more material. That's why they sound so much better.



But to your original question, yes. Changing the exhaust will lean the engine out. You'll have to read the plug like previously said.

 

[danssoslow]

Half-breed,

If you like investigating and learning new things, look into building a helmholtz resonator muffler. I'd bet you that's something that has never been done on a kart before!

 

[DeathStarr89]

Very true... and it's not that hard either.

 

[Doc Sprocket]

Can't wait to see what you come up with. Here's mine- http://www.diygokarts.com/vb/showthread.php?t=7449

I regret that I did not do a how-to writeup or video and I STILL get folks asking. I may do another, for that purpose.

While that kart is long gone, the Cherry Bomb is alive and well on MULE.

 

[Tig]

Half-breeder,
I like the design pictured, like said a bigger case and more material may sound better. I'm a big fan of MagnaFlow
You can also make it a tuneable muffler by welding one end and riveting the other. That way you can add or remove packing to get the desired sound.
I'll post a pic of one very similar to the one I made, it was for my motorcycle.
what is your "twist" that you had mentioned?

Half-breed,

If you like investigating and learning new things, look into building a helmholtz resonator muffler. I'd bet you that's something that has never been done on a kart before!

That is a great idea.

 

[Half-breeder]

...what is your "twist" that you had mentioned?

Well...I call it a 'twist'... a compensation for the lack of back pressure... add more pressure... like dual ends(2 mufflers)... just giving the appearance of dual exhaust off a 1 cylinder motor. But Im gonna try a single setup to see how bad its gonna lean things out... then Ill add the 2nd after I find out the effects of the 1.

...things are still in my head... slowing realizing the simple isnt simple if math is added... sigh.

 

[firemanjim]

Not sure if you can see it, the red muffler on the pink kart, is half of a dual exhaust from a china crotch rocket. I made a header flange ,ported to fit the exact shape of the block, and smoothed over a little for flow. Then I welded the muffler to that using the same size pipe. It had TOO much back pressure and wouldnt let the engine run or rev up properly. Could not figure out why till i looked inside. The pipe did not go completely through the case ,it was just a nipple on each side. The gasses were dumping into the case and fighting to get out. I cut the welds off one end and cut a piece of pipe to fit the distance between the nipples ends. Drilled a bunch of 1/8" holes like the ones above,and put it back together. Runs like a beast now.... I dis not add any wadding or packing. I had made stainless steel "wool" to pack it with but I love how it sounds...

 

[Half-breeder]

Well... the originally designed muffler I was starting, will have to be trashed due to lack of patience... but I have sheet aluminum(aluminum flashing for roofing)and a lil 8$ after market muffler... so I was thinking...
... the muffler

... and the outer casing?... slide to get desired 'tone' then clamp down. Itll cover the lil stubby muffler/ugly screw on fabrication to pipe n after lined w/ steel wool, wont be 'as' hot to the touch!
Casing will be bout 7" long 3" diameter.

 

[danssoslow]

Welding a resonator around a muffler can defntely deepen the tone. This setup was an Autozone fart can tip welded to an RLV muffler. It had a really deep tone, like a single cylinder Harley at idle.

 

[firemanjim]

Got bored at work today..... This will go on the next kart engine....

 

[firemanjim]

I guess a finished pic would be nice too.....
SAFETY NOTE: If you're eagle eye is working, you will notice that the big tube is galvanized..... hot dipped fence top rail. As I stated in another post, DONOT weld galvanized metal as it puts off toxic fumes (welding dont?)...... When cutting , welding, and grinding on this muffler, I wore a supplied air respirator

 

[landuse]

Nice muffler!!