Removing Muffler (good or bad)

[kickflipjr]

I heard bunger say that the muffler doen't help fuel economy at all. I was just wondering what you guys think?

btw I can deal with the with the noise.

original post by bunger:

With most mufflers designs, the exhaust velocity is going to go to crap anyways, so at very least, don't create a bottleneck. The good part is, that far back in the system, the exhaust gases have had some time to cool and condense, so flow requirements decrease.

In a perfect world you would probably have a total straight tube that very slowly decreased in diameter to maintain the port velocity with a tip that was designed in such a way that the passing fresh air would create a vacuum, and thus lower pumping losses even more.

[rh77]

Originally Posted by theclencher

What about everyone around you?

Let me get this straight -- nearly every Tempo I've come across has had a rattling heat shield, hole in the exhaust manifold, or the muffler is AWOL -- so your 5-color Tempo is in perfect resonance?

So why didn't you spring for the Topaz? Better re-sale.

RH77

[rh77]

Originally Posted by theclencher

You better give mine a listen before you rush to judgement.

Call me on the phone; I'll go out and start it for ya.

Re-sale?!? Why would I sell?

Come on, jump into the 21st Century! Get a microphone, record it on your computer and post it We're all dying to hear it

Come to think, it would be harder to find 'Paz parts as there were fewer of them. It's just that whole Ford/Mercury re-badging that makes no sense. They still do it today with the Escape/Mariner, Fusion/Milan, Crown Vic/Grand Marquis, Explorer/MKX, Expedition/Navigator, etc. Now Pontiac is coming out with a G5, which is essentially a Cobalt. Make NEW cars already people!

New rule: no more brand sharing.

RH77

[rh77]

Originally Posted by theclencher

My mic cord ain't that long.

Well, shoot. Move the computer! LOL, I give up.

Initials and Year

[tomauto]

But some people are fooled by badge engineering, so...why not do it.

[onegammyleg]

A couple of excess noise fines and a forced reinspection of your muff-less car will negate any FE money savings.

[Jack]

My CRX came with a **** muffler so I ripped it off and drove around with out one for a a month or 2. When I finally put the new one on my MPG went up.

[Sludgy]

Originally Posted by Jack

My CRX came with a **** muffler so I ripped it off and drove around with out one for a a month or 2. When I finally put the new one on my MPG went up.

Removing the muffler, installing headers, and/or a low restriction muffler will hurt fuel economy in closed loop FI systems, for a number of reasons:

1) Reducing the exhaust backpressure will allow more air to be sucked throught the cylinders and intake. The ECU will control the air/fuel ratio at stoichiometric, so the fuel rate also goes up. Great for power, but not for economy.

2) Then, because more air and fuel is being burned, the ECU must tighten the throttle. So by removing the exhaust restriction, a worse restriction is added to the intake (at the throttle body).

3) Exhaust systems are "tuned" for a given rpm. Changing the exhaust geometry changes the most efficient operating point of the engine. Reducing exhaust restrictions usually raises the best efficiency RPM, again, good for power, but not good for economy.

Save your neighbors' ears. Keep your stock muffler.

[Bunger]

Originally Posted by Sludgy

Removing the muffler, installing headers, and/or a low restriction muffler will hurt fuel economy in closed loop FI systems, for a number of reasons:

1) Reducing the exhaust backpressure will allow more air to be sucked throught the cylinders and intake. The ECU will control the air/fuel ratio at stoichiometric, so the fuel rate also goes up. Great for power, but not for economy.

Perhaps, but then you'll be making more power and would require less throttle input and in turn, less fuel.

Originally Posted by Sludgy

2) Then, because more air and fuel is being burned, the ECU must tighten the throttle. So by removing the exhaust restriction, a worse restriction is added to the intake (at the throttle body).

Unless its drive by wire, thats not going to happen. But you do have a point... if you needed less of a throttle angle, that would increase pumping losses on the intake side.

Originally Posted by Sludgy

3) Exhaust systems are "tuned" for a given rpm. Changing the exhaust geometry changes the most efficient operating point of the engine. Reducing exhaust restrictions usually raises the best efficiency RPM, again, good for power, but not good for economy.

Save your neighbors' ears. Keep your stock muffler.

Perhaps also, but mufflers are heavy also, never good for FE... and with my 92 HP motor, a cat and resignator in the exhaust stream, my blue CRX is quieter than my silver B18C CRX with full exhaust.

I'm not suggesting everyone go remove their mufflers, but there are things that could be done to the exhaust system to improve FE.

It would be pretty easy for me to add a restrictor to my exhaust system, I wouldn't mind rolling around with it for a week or so to see what the results are, maybe I'll have to eat some of my words. =)

[Sludgy]

Originally Posted by Bunger

Perhaps, but then you'll be making more power and would require less throttle input and in turn, less fuel.

Unless its drive by wire, thats not going to happen. But you do have a point... if you needed less of a throttle angle, that would increase pumping losses on the intake side. =)

I think some new cars ARE drive by wire, at least to some extent. I remember old automatics where the rpms would drop when you went from N to D.

My Ford automatic idles at the same rpm regardless of what N or D, and so does an 07 Camry that I just rented Monday. This can't happen unless the ECU is controlling the throttle to some extent.

Anybody shed light on how much "drive by wire" control is in newer cars?

[onegammyleg]

Hi Sludgy -¨I remember old automatics where the rpms would drop when you went from N to D.¨

When an auto is placed into gear there is more load on the engine than at idle , so it is logical that a reduction of rpm is noticed., especialy at idle when the engine is making very little power.
Older auto cars would just have a slightly lifted idle speed so when a gear is selected the engine speed drops down to a normal idle.
On many autos their ignition settings and camshaft specs may be different compared to a manual to allow a slower idle speed , ,and a power band more suitable for the auto trans. application.

In almost all auto EFI cars they use a thing called ¨idle up solenoid¨
When D is selected the solenoid will activate increasing the speed.
Even many manual trans cars have this fitted to lift the idle when the air conditioner kicks in.

A ¨Drive by wires¨ exact application would mean NO physical conection between the operator and the throttle system.
I havent seen any cars (ime sure they exist) that are done this way .. almost all still use a throttle cable to a butterfly on the intake side of the engine somewhere.


PS . on some cars they have an idle up soilenoid which may work mechanically on the throttle linkages to increase idle speed , but some do it by bypassing more air past the throttle butterfly , this is usually called ¨Idle air control¨= IAC.
Diferent way , but same overall result.

[rh77]

The TSX is throttle by wire, and I really need to research what exactly is involved. It works in concert with the i-VTEC, probably for best FE/Emissions.

RH77

[thisisntjared]

you will get better mpg without a muffler. leading reason:

even though you say you can stand the sound, you really wont, and in turn you will go lighter on the throttle and end up saving fuel that way.

my muffler rusted off. i got better fuel economy because i never wanted to floor it. then the rest of it rusted off right behind the header the next week. fortunately i already had my new exhaust in the mail, but i did drive to work open header for one day. that was so loud that i didnt baby it anymore, i just floored it everywhere cus it was just so rediculous.

i have to admit, open header pulled like a freight train. i had fun in that one day.