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Discussion Starter #1
Has anyone ever gotten under and looked at the exhaust on their van?? Well I know a couple have because I've talked to them about cutting some stuff out. I've noticed before the two resonators and huge muffler and am planning on removing all of those and going with a less restrictive muffler, but today when looking at where to install a cold air intake, I noticed how the headers/manifold, run into the exhaust before the cat. The rear side connects back into the exhaust in a revers y connector!! There was plenty of room for them to flip that around but they actually have the exhaust running backwards for a bit there which seems ridiculous. I may see about fixing that, just wondered if anyone else had tried messing with it.
 

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'04 Kia Sedona EX, '10 MBZ C300 Sport, 1.3KW Electric GoCart
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The reason for the odd exhaust routes on your Sedona are probably for 2 reasons, overall noise and emissions. True, you may get some slight performance benefits by opeing the exhaust up, but I think you will get more noise than actual performance.

Also, if you look at the HP/torque specs of the motor, the torque curve is very low, starts right after 2000 RPM (maybe a little higher, going by memory). One way to bring the torque curve down is to restrict the exhaust. The wrap around route or backward Y connection maybe way you get such great low end torque. This may also hold the exhaust gas in the CAT longer for better burn off.

Contrary to most enthusiast, lots of engineerng time goings into all systems of a van or auto. True, there are slight trade-offs in performance to accomadate the normal public, but you have to understand, the engineers probably did not design the Sedona for "sport" purposes.

Even if you open up the exhaust, with a cold air kit on the intake, you still do not know the combustion chamber design along with the size of the intake and exhaust ports in the heads. You may be going down this path for nothing.
 

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I understand the reason why the resonators were put on there which is only for noise reduction and by removing them it will increase the exhaust sound volume but I doubt it will increase it a lot, it should give it a nice soft rumble, which is what another member reported when doing the same thing. With where the muffler is mounted there is still a plenty of pipe and bends to muffle the sound. I would still plan on leaving the last small resonator since it is basically a straight through pipe.

My main goal is not increasing performance, it is to increase fuel economy. All that restriction makes the engine work a lot harder and robs it of fuel economy, power, and torque. This was the reason I removed the air intake tube they had, since it was only on there to muffle the intake sound. The sound difference with it off is barely noticable from inside, only when getting on the throttle. The pickup on that was no difference from where the air filter box would pick up. I just took a 90 degree elbow and 3 inch intake pipe and ran straight down to pick up cooler air.

The reverse Y still poises no usefullness to me and was probably a something they did to accomodate the exhaust manifold, I haven't really crawled under to look, I just peeked the other day and was like.."what the f###". I havne't seen a dyno test for the engine, but I'm certain, removing the resonators or reversing the Y would only improve it. I've noticed as soon as you take off, there is a slight sluggishness, which then you feel a kick of torque coming on. I would account this slight sluggishness to that restriction. Also, the Cat is after the Y, so that wouldn't have been the reason for it. Restriction is never a good thing, though a little is needed. Fast flowing exhaust gases is a good thing, which is what creates low end torque, which in turn is created by using a certain amount of restriction. This is dealt with by the pipe diameter. Running exhaust backwards would do nothing to increase gas flow, and would only rob you of torque. I'll attach an article I found about backpressure and increasing torgue.

"Exhaust system back pressure as a result of restrictive mufflers, catalytic converters and multiple sharp bends in the exhaust system can be severely detrimental to good torque and power. Exhaust pumping losses caused by restrictive exhaust back pressure can be substantial in some applications and the problem increases dramatically with engine speed. Performance camshafts are also rendered less effective because back pressure typically negates any improved cylinder scavenging during the overlap period. The Catch 22 with exhaust systems is your own personal comfort with the sound level of the mufflers. You can run mufflers with virtually no restriction, but the drone may drive you crazy the first time you take a 100 mile trip. The best approach for most moderate street engines is to complement all the other torque building efforts you have applied by using a small tube header with at least 2.5-inch diameter exhaust pipes and the least restrictive muffler you can stand relative to sound levels. A crossover tube to balance the pulses from each cylinder bank can help smooth the sound a bit and it may add a very slight amount of torque depending on the rest of the application. It is usually worthwhile. "

Here is also one on cold air

"Finally, anything you can do to enhance air flow into the engine at cooler temperatures will be good for torque and horsepower across the entire rpm band. Remotely sourced inlet air is almost always cleaner and cooler than engine compartment air. Use an aluminum intake manifold with the carburetor exhaust heat blocked off. Manifolds with runner separated from the valley keep the charge cooler and thus denser. Duct your air from outside the car and keep the ducting insulated from engine compartment heat. Make your inlet ducting at least 4 inches in diameter or larger and keep the path as short and unrestricted as possible. Be sure to duct the air through a high flow air filter prior to entering the carburetor. These simple modifications can increase torque on the order of one to three percent and they will also increase power at high engine speeds due to unrestricted airflow and a cooler charge. "


I understand that engineers are not trying to make the minivan a sport vehicle, which isn't what I'm trying to do either. I'm trying to make it more fuel friendly at normal driving and a little added extra power when getting on it doesn't hurt either. Engineers are usually too driven by cost. I'm guessing being it's a minivan, they targeted a soccer mom and thought they would want a quite vehicle, and traded off better fuel economy for that purpose.
 

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'04 Kia Sedona EX, '10 MBZ C300 Sport, 1.3KW Electric GoCart
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Last night I changed my oil on my '04 and I remembered this post. The reverse "y" connection between the left/right exhaust manifolds seems to be there because of an assembly issue. The motor is probably installed with the lower level exhaust components all ready mounted to the engine. I see the "extra" room you are referring to under the van. You could probably get everything cut off and custom pipes made.

On last thought, the "Y" connection that makes the backwards bend may be there to match the exhaust tube lengths between the left/right engine banks. Equal tube length headers for American V8 engines look strange sometimes for this very reason.
 
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