the muffler and exhaust mod thread

[mcrews]

"Your chart is wrong. Many factory vehicles produce more than your max hp figures."
Ok, that sentence really is not factual. sorry.
Starting with A and going forward alphabeticly.......
please list the many factory vehicles that are over 935hp.........
come on, lest than 10% of all factory vehicles can make 500hp.

Better yet, find me a chart that disputes the one posted.

[mcrews]

But hey, lets have everybody re-pipe for 2.5 and then lests do some eco driving at 15-1800rpms at 55mph on a 30%load.

I find it interesting that 'certain items' always fall on the hp side and 'other items fall on the fe side.
Exhaust is always about "factory sysytem is restricitve". Maybe for hp, but not for FE
Just look at the exhaust on the factory fe civics or any other fe car.
Ther factory is trying to get the very max fe possible......and they design a crappy exhaust???? I really don't think so. exhaust pipe is cheap. doing it correctly for max fe is not an additional cost.

And there have been plenty of threads debunking the 'more hp means more effeceincy'

[Ladogaboy]

mcrews, he isn't stating what size is better for FE and whether an increase in HP equals an increase in FE. What he is saying is that many cars come factory stock exceeding the Max HP per diameter that that chart reads. For instance, my car (with a stock 2.25" exhaust) is running about 100 hp more than the max your chart has listed (291 hp versus 185 hp). After a tune, still running stock exhaust, my car is pushing an additional 30 whp over stock.

In terms of whether the stock exhaust is ideal for either power or FE, I can almost guarantee that it is neither. It is one of the areas where the manufacturer can save a lot of money (i.e., they use cheaper, bulkier, and sometimes less-efficient materials), and they have many concerns that go beyond power and FE. For instance, they also must assure that they meet emissions testing, noise requirements, etc.

[slowmover]

When I bought my truck the PO had removed the stock muffler and tailpipe and replaced it with an:

- Aeroturbine 4040

but the drone while towing was unreal. Had to almost (literally) yell for my wife to hear me. After reading some threads on TDR I copied the move made by several by moving the A-T forward to serve as resonator and added a

- ROKKTECH Silent Might

which has to be the best sounding muffler ever made for an ISB Cummins. Straight-thru but for 3-square holes cut at one end (large chamber surrounding pipe) in the direction indicated for "quiet" (on a quiet muffler).

The section cut out was used to replace a gaudy tailpipe tip (extends exhaust out past rocker panel several inches. Definitely a school bus look).

The exhaust system is essentially a 3.5" i.d. pipe with [2] 4" i.d. pipe mufflers.

Is it better than stock? Maybe, maybe not. But it is lower backpressure I'm fairly sure and just about as quiet but with a different sound (sharper) than the stock system.

I've thought about playing with it by adding an EAG at the mouth of the A-T as a few reports indicate better steady-state fuel burn.

.

[mcrews]

Originally Posted by Ladogaboy

mcrews, he isn't stating what size is better for FE and whether an increase in HP equals an increase in FE. What he is saying is that many cars come factory stock exceeding the Max HP per diameter that that chart reads. For instance, my car (with a stock 2.25" exhaust) is running about 100 hp more than the max your chart has listed (291 hp versus 185 hp). After a tune, still running stock exhaust, my car is pushing an additional 30 whp over stock.

In terms of whether the stock exhaust is ideal for either power or FE, I can almost guarantee that it is neither. It is one of the areas where the manufacturer can save a lot of money (i.e., they use cheaper, bulkier, and sometimes less-efficient materials), and they have many concerns that go beyond power and FE. For instance, they also must assure that they meet emissions testing, noise requirements, etc.

got it! my misunderstanding.

[malibuguy]

It all depends on driving habits. If your driving the car so lightly...then exhaust mods will typically not benifit. Now say if your really running the vehicle hard...say a gas truck towing alot...then yes the added flow area of a proper custom exhaust can result in better FE.

I lose about 2-3 mpg on my Yaris with my full custom exhaust...stock is a perfect 1.75" mandrel bent exhaust with a calibrated spring loaded valve in the muffler. When im hypermiling i dont go past 2500rpm. However my 2" mandrel bent exhaust does make a major HP improvement on the top end

[malibuguy]

I forgot to note my gfs car picked up about 2 mpg with the custom exhaust i did on it. Its an automatic and she is usually running the kids around so it actually benifited.

[2005_rs]

My magnaflow installation looks alot like your pic in the o.p. The noise was horrible until I added a 9" tailpipe section onto the muffler in order to terminate the exhaust at the bumper. That quieted it down a lot. I think the sound was resonating off the inside of the bumper and underneath the car until I made the change.

Originally Posted by California98Civic

In the OP I dismissed the Thrush Turbo as a fart can, then I continued looking and eventually found someone who insists it sounds a lot like stock and does not attract police attention like other mufflers. I think the fart can effect heard in the vid in post #1 might be because of a tip. The cheaper price of the Thrush remains attractive for an experiment.

For the hell of it, for the cheap of it, and for my general weight reduction project, I'm thinking I'll get the Thrush, compare its weight to stock, install it, post my own sound video, and compare its life span with the several stock mufflers this car has gone through over the last decade. Cheap initial cost and modestly lighter weight are the only savings/FE goals. And additional benefit might be that it has a smaller diameter and might integrate better into a underbelly pan project for the rear of the car.

[hackish]

Originally Posted by mcrews

"Your chart is wrong. Many factory vehicles produce more than your max hp figures."
Ok, that sentence really is not factual. sorry.
Starting with A and going forward alphabeticly.......
please list the many factory vehicles that are over 935hp.........
come on, lest than 10% of all factory vehicles can make 500hp.

Better yet, find me a chart that disputes the one posted.

Pipe Dia. (inches).....Total CFM (est.)....Max HP for 1 Pipe.... Max HP For Dual System
1 1/2 .......................171.................... 78........................... 155
1 5/8 .......................203 ....................92 ..........................185
1 3/4 .......................239 ...................108 .........................217
2 ............................ 318 ...................144 ........................289
2 1/4........................ 408 ...................185 ........................371
2 1/2 ........................ 509 ...................232 ......................463
2 3/4 .........................622 ...................283....................... 566
3.............................. 747 ....................339...................... 679
3 1/4........................ 882................... 401 ........................802
3 1/2.........................1029 ..................468 ......................935

Here is your chart again. Don't take a single line of it and claim the entire chart is accurate because you can't find any vehicles with twin 3.5" exhausts. When you list maximum horsepower for a pipe size it should have some vague correlation to be a bit larger than common vehicles producing those horsepower figures.

Let's start at the top:
Honda Civic Si 1.6l engine 1.5" exhaust 130bhp way more than your max of 78hp
Acura Integra GSR 1.8l 1.75" exhaust 180bhp way more than your max of 108hp
Honda S2000 2.0l 2" exhaust 240bhp more than your max of 144
Subaru Impreza WRX 2.25" 227bhp more than your max of 185
Dodge SRT4 2.4l stg3 2.25" exhaust 310bhp your max 185
Chevy Corvette Z06 2 1/8" exhaust 505bhp your max for 2.25 duals 371
Cherokee SRT8 2.75" single exhaust 420bhp your max 283
Bugatti Veyron SS 3" dual 1184bhp your max 679

The problem with your list is that it's entirely incorrect. If it was just a few odds and ends here and there that were 20% off the mark I wouldn't complain. We're seeing horsepower numbers well over 50% above your stated maximums.

The one thing worse than not posting a list is posting an incorrect list. If people read this and take it as fact then make decisions for their eco mods based on your list you're doing them a big disservice.

[hackish]

Originally Posted by Ladogaboy

In terms of whether the stock exhaust is ideal for either power or FE, I can almost guarantee that it is neither. It is one of the areas where the manufacturer can save a lot of money (i.e., they use cheaper, bulkier, and sometimes less-efficient materials), and they have many concerns that go beyond power and FE. For instance, they also must assure that they meet emissions testing, noise requirements, etc.

This is exactly what goes on. The engineers design it for ease of fabrication & installation on the assembly line. They have to make sure there is adequate clearance so you won't have rattles or heat/fire concerns. They have to make sure it meets the noise limit laws. They want to make sure it's going to outlast the warranty period. Depending on the size of the car company they will sometimes design exhaust routine to match with other already engineered exhaust components. It's not a mistake that an exhaust for a 1992 Subaru Legacy Turbo is close enough to a 2006 WRX that you can bolt many of the components right on...

The exhaust system is not typically where they look for fuel economy. Instead that focus is on the engine calibration and gear ratio selection - for slushboxes the shift program as well. In fact I remember about 10 years ago a carmaker got busted because they wrote a detection routine in their PCM so it detected when someone was running the EPA fuel economy driving test and modified the engine parameters to get a better score.