# Does two exhausts make a difference?



## naazlee (Aug 12, 2010)

I was wondering to have two exhausts, what do you all think will it make a difference in the performance of the car. I am looking for an initial ppick up..


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## Tom_Cruze (Jul 23, 2010)

Yes it will. It will actually make the car slower. The smaller the displacement of the engine the smaller the exhaust opening you'll need. One exhaust tip will be more than enough for the Cruze. You lose a lot of throttle response if you go too big of an opening.


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## descorpio (Aug 15, 2010)

Having two exhaust will consume more fuel and it's a no-no as far as family car is concerned. It's a double edged sword like make you to spend more to maintain the vehicle.


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## naturelover (Aug 12, 2010)

Vehicles fitted two exhaust's are normally slow in pickup but definitely give great pleasure in long drive where one can witness the great speed. The main concern for any car owner is fuel efficiency and I doubt two exhaust's serve any purpose in this front than just sheer pleasure.


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## adhityaen (Aug 15, 2010)

Apart from the listed benefits and pitfalls in having two exhausts, the most important is maintaining exhaust systems as it improves the engine life by exhausting gases created when fuel and air are burned in the combustion chamber. So do a regular check up of the exhaust system to get great engine life and power.


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## princee18 (Sep 1, 2010)

It's true that two exhausts gives a car a less fuel efficiency but it certainly improves the engine performance and it does not effect that much mileage of your car.


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## Machida (Aug 16, 2010)

It will be slower but I think that is the price that you will have to pay for extra exhaust. Having an extra exhaust will only meant that I could easily cool down the engine.


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## Tom_Cruze (Jul 23, 2010)

princee18 said:


> It's true that two exhausts gives a car a less fuel efficiency but it certainly improves the engine performance and it does not effect that much mileage of your car.


No it won't improve the cars performance. Not even by a longshot. The engine displacement of the Cruze is too small to even warrant anything bigger than a full 2.5 inch exhaust system. Anything larger will lose too much back pressure.


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## 70AARCUDA (Nov 14, 2010)

...so, a BORLA dual cat-back system is only for "show" and not "go" on a Cruze (wink,wink)?


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## motorhedfred (Nov 13, 2010)

What are guys basing all this "technical" information (opinion?) on ? The facts are _any_ back pressure is bad where an internal combustion engine is concerned. Back pressure is an unfortunate side effect of exhaust velocity which is absolutely needed for an efficient exhaust system.

The engineering challenge is to make an exhaust system that's sealed, quiet and flows well enough to allow the engine to reach the target power level. The velocity helps evacuate the cylinders which readies them for intake charge. Back pressure is especially bad for a turbocharged vehicle as it slows turbo spool up and limits maximum boost.

If you want the look of duals, make a crossover pipe after the muffler with some nice tips.....no loss of "back pressure", no issues with O2 sensors...ect.

MHF


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## cruze-control (Jul 23, 2010)

70AARCUDA said:


> ...so, a BORLA dual cat-back system is only for "show" and not "go" on a Cruze (wink,wink)?


yes it is mainly for show (wink, wink)! i guess thats why all the cruzes competing in the wtcc only use a single exhaust because. they probably dont know what theyre doing. oh wait i just remembered they actually do. they won against some really good cars. 

too much back pressure is bad for your engine however without any back pressure the car will feel like it has a turbo rotary. no useable power whatsoever until the turbo kicks in. ever tried driving a 4 cylinder car with too big of an exhaust up a very steep incline? i have, my friends cobalt... the exhaust he put on it was way too big. it helped his top end but going up a steep incline is a near impossibility.


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## shawn672 (Oct 31, 2010)

You don't want "back pressure"... you want RESTRICTION. the exhaust gas needs SOME restriction (too much and it shifts the power band too low, too little and it shifts it too high)

that being said, turbo cars respond EXTREMELY well to exhaust modifications, but obviously using piping thats too big will not have enough RESTRICTION and the car will actually lose horsepower.





> *III. Backpressure and velocity
> *Some people operate under the misguided notion that wider pipes are more effective at clearing the combustion chamber than narrower pipes. It's not hard to see how this misconception is appealing - wider pipes have the capability to flow more than narrower pipes. So if they have the ability to flow more, why isn't "wider is better" a good rule of thumb for exhaust upgrading? In a word - VELOCITY. I'm sure that all of you have at one time used a garden hose w/o a spray nozzle on it. If you let the water just run unrestricted out of the house it flows at a rather slow rate. However, if you take your finger and cover part of the opening, the water will flow out at a much much faster rate.


Exhaust backpressure the myth - ThumperTalk


They call it velocity in this article, as restriction is just a lower velocity though.


Also to the person who referenced the WTCC car.. you should also note it has a 2.0L engine, it's not the same setup that stock cruze's rock


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## bpipe95 (Nov 1, 2010)

70AARCUDA said:


> ...so, a BORLA dual cat-back system is only for "show" and not "go" on a Cruze (wink,wink)?


 in short yes.
GM makes pretty good flowing factory exhaust. Only reason to put a cat back on one would be to make more noise. 

I would put a new downpipe on before ever touching the rear section of the exhaust. And having two exhaust pipes with tips all coming out of one cross flow muffler. like the ones already made overseas for the cruze is not going to kill power.

NA cars are way more sensitive to exhaust size and flow than a turbo car, you can still over exhaust a turbo car it just takes a very over sized exhaust to do it.


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## cruze-control (Jul 23, 2010)

shawn672 said:


> You don't want "back pressure"... you want RESTRICTION. the exhaust gas needs SOME restriction (too much and it shifts the power band too low, too little and it shifts it too high)
> 
> that being said, turbo cars respond EXTREMELY well to exhaust modifications, but obviously using piping thats too big will not have enough RESTRICTION and the car will actually lose horsepower.
> 
> ...



my bad. ive always referred to restriction as back pressure. now i know they are completely two different things. having said that the fact that the wtcc cruzes use a larger displacement motor and still decided to keep it a single exhaust proves my point even more that you need restriction in your car.


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## MikeyCruze (Oct 28, 2010)

Thanks for the info guys, good thread to learn from.


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