Dual exhaust question
I have an oppurtunity to get a cat back dual exhaust installed on my mini-van (waiting for the laughter to subside) for $90. How much power/fuel economy can I gain from this?
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Probably none. Consider these points...
An upgraded exhaust system is important when upgrading other stuff too. For it to help power, I'd expect you would also need to upgrade most of the intake system and the ECU at the least. |
There are two rather major flaws in all of that logic....
One of the biggest focuses of OEM exhaust/intake systems is quietness, and cheapness. If the pipes are anything but mandrel bent (Only now done on hi-po cars) they're restricting at WOT. And if it's so quiet you can't hear it running... It's restricting. There's also the fact that minivans are never sold based on horsepower, they're sold based on convenience and comfort. And part of comfort is quiet. There is no incentive to eke every last horsepower out of the engine that they can, so they don't spend nearly as much time perfecting the exhaust as they would in an SRT car or something like that. Your statements are true, to a limit, when dealing with modern High Performance cars, as they do want to squeeze every horsepower within reason out of their cars. However, still... They need to make them reasonably quiet and keep production costs down. Which is why exhaust upgrades are a reliable way to increase power with almost every car. With an '05 Mustang GT, a magnaflow cat-back system was dyno proven to gain 11hp. Worth the high cost of such a system? Doubtful. But showing actual gains? Yup. Definately. Basically, in every car, if there was at all a desire to keep either sound or cost down, you can improve the intake and exhaust for power, over OEM. The less of a desire there was to keep sound and cost down... The less you'll gain. |
I'd be worried that the new, cheap catback exhaust would rust out quicker than the stock exhaust. Is it stainless steel?
You might gain 5hp, which is barely noticeable. I'd be suprised if you saw any gains in FE. OTOH there's a good chance the new catback is noisier. Quality exhausts will cost more than $90. |
my only thought was that you MIGHT realize FE gains IF your present exhaust was old/leaking. but, i see your van is a 2007, so it's doubtful based on that premise.
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What are your exhaust manifolds like? Log style or the more conventional extractor type?
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The retail on the exhaust is $250 but my discount would be 60%. I have no idea what my exhaust manifolds are like. I just think it would be funny to have dual exhaust on a mini-van but I think my wife is going to veto the move based on the "that's a stupid waste of $90" arguement.
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The deal about bigger exhausts has to do with exhaust gas velocity and the engine's powerband. Bigger pipes allow a higher CFM flow at a lower velocity, smaller pipes allow a smaller CFM flow at a higher velocity. The bigger pipes generally move the powerband of the engine up higher, and the smaller ones down lower.
I really wouldn't reccomend duals. If you're going to do this and they do not have mandrel bent piping (95%+ of shops only do crush bent), 1/4" to 1/2" bigger DIA than the SMALLEST dia on the stock system should treat you pretty good as a rule of thumb. I've got a 2.25" mandrel bent straight through exhaust system on the Saturn. I'm getting improvements in gas milage because the cat was bad, but it's a pretty fair amount of a gain. I also put on a ceramic coated header, which has a lot to do with it. When my car's not having problems with other things breaking, I'm using 2-5% less throttle on the highway. I used to need about 15-16% throttle to cruise behind a truck at 55MPH - now it's 10-12%. The highway economy has gone way up, but the city hasn't really moved too much. |
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Anyway, you probably already have stainless steel exhaust. Personally I do not think you will gain anything though. You will just be out the money spent, so I guess I will have to agree with your wife on this one........ Sorry. Just my opinion. |
^ I've drove one of them for an extended period once... bits of trim were falling out and it had 35k miles on it. :-p
I work on cars including exhaust at work. you won't gain anything by changing the pipes. the caravan/t&c pipes are plenty big. you MIGHT gain something from free-er flowing mufflers. as stated, cars are designed by expert engineers...the same engineers that put half chryslers lineup battery in the d^&* wheel well and the steering rack wedged behind the engine to name a few expert designs. goal #1: cheap. goal #2: emissions (mostly manifold/cat) goal #3 of exhaust: quiet (depending on the application)goal. the biggest FE gains are in FE oriented headers and cat followed by free flowing muffler. |
I would think that any gains (FE or otherwise) would be negated by the weight of the 2nd set of pipes and the 2nd muffler.
Personally, I'd use the $90 for something else. |
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