Soul intake/exhaust questions
 

I was looking around on the Kia Soul forum and I saw that many people were installing cold air intakes and new exhaust systems for added HP.

Will either of these mods help my mpg? I don't really want to do anything to hurt the mpg...but at the same time I do enjoy kicking my horses around once in a while and as such want to upgrade the motor a bit... currently if I sit at a light and rev for the babe next to me...it sounds lame and I hit 3rd gear and it puddles out till i can get the rpms way up, and by that time the smokin hot babe has, well, smoked me...LAME! :mad:

It depends on two things. How you drive it and how the engine/transmission itself responds to the modifications.

If you want more power to go faster, then of course you're going to loss economy. Its hard to get around basic physics and chemistry.

I am not familiar with your drive train either. If you have 5th or 6th gear, you most likely won't see any highway gains, and have the possibility of losing MPG. Pulling more air through the system will increase full consumption as the engine management attempts to maintained program A/F ratio. If you have a 4 speed where you encounter flat spots of acceleration, opening up the intake and exhaust will help you maintain less throttle to obtain higher speeds.

Its a trade off, you'll have to try for yourself. You could always ask the people with Kia Souls if anyone has noticed a difference in fuel economy with those modifications. You'll need to find an honest opinion from someone who accurately tracks their mileage. Most of the time, if you putting on intakes and exhaust you're not worried about FE and new accessories "encourages" you to drive faster and will lose FE. You need to find a driver who kept their driving habits the same given a new intake and exhaust to get an accurate answer.

here is an exhaust calculator, this is ideal size for the given RPM that you put into it, not to big, not to small.
Autolounge.net | Calculators | Exhaust Pipe Sizing

here ya go buddy
69 SERIES TYPHOON HIGH FLOW PERFORMANCE COLD AIR INTAKE KITS - JCWhitney

that with a straight pipe from the cat back to a flowsound muffler off ebay wiill pick up a little bit of power and make the car cruise along easier. in cars that are underpowered like this small mods can make a big difference My buddy's PT cruiser we put just a cheap intake with and replaced the rear muffler with just one of those flowsound mufflers and it cut a whole second and a half off of his 0-60 10 instead of 11.5 and it got 3 MPG better too cause power was more readily availible and the way he drove that helped

I am trying to understand this as it applies to more than just the SOUL. You seem to be saying two different things:

1) If you modify the intake and exhaust to ALLOW more air flow this doesn't actually PULL more air does it? Air flow is a function of engine RPM right? Are the "flat spots of acceleration" due to air flow restriction?

2) After the mods will you be able to use less throttle at lower speeds also or does the increased AVAILABLE air flow only help when at higher RPM than most FE driving calls for??

Don

MetroMPG tested high flow air filters long ago and proved that they do not improve mileage.

Testing a 'performance' air filter for MPG - Part 1 - MetroMPG.com

Testing a 'performance' air filter for MPG - Part 2 - MetroMPG.com


Tweaking the exhaust can likely lead to small increases in mileage. However, you'll likely want to go smaller than OEM pipe size to do this and that may reduce peak horsepower.

Last night Soulster and I stayed up late and did some ABA testing. On his car, we could take off the intake pipe at the air filter. This leaves about 14" of pipe or the same size as the warm air.

We did ABA testing on the same stretch of road the I used for my mod testing. He drove and I put the data into a spreadsheet. Once I got him to do testing we kept going and did his upper grill block, folded in the side mirror, and removed the side mirror. Once I process the data Soulster will post it up. More data for the wiki :)

It depends on the how/why the intake was designed. There are many different reasons why air intakes have ribs/ tubed chambers/ large chambers, etc. Sometimes its to mellow out the noise of the engine. Sometimes it is to provide better throttle response.

And yes modifying the intake will increase the amount of air the engine actually pulls. There are realistic limits as to how much air you can suck through a hole without generating more turbulence within the pipe. By opening up the smallest "diameter" of the intake and exhausts you can change physical amount of air that can be pulled by the motor. You can also effect this by length of the intake piping, number of turns, types of baffles, etc.

Think of it like a vacuum cleaner. Consider the motor of the vacuum to be a constant. If you hooked a dryer vent onto your normal household vacuum cleaner, how well would it pull up dirt from your carpet? not very well..

Now switch to something like a 1/2" radiator hose. You'll have a higher PSI vacuum on the 1/2" hose than the dryer vent, but It would also be very ineffective because the motor could be fighting itself to pull more air though the small 1/2" hose.

Now consider the regular hose. Neither the dryer vent or the 1/2" hose would work as well as the normal 1" or 1-1/4" vacuum tube your vacuum came with. There is a peak operating diameter for the hose to get the most pull/area without losing the vacuum like the dryer vent and restricting the motor with the 1/2" hose.

A car works the very same way...except that the motor has variable speeds (and thus volumes of air flow). So one type of air intake may work better for lower RPMS when you achieve the best fuel economy, while one style of give you the most power in the higher RPMS, which when you're ecomodding will NOT help fuel economy!

Maybe that clears some of it up.

As for the "flat spots" have you ever been climbing a hill (in your car, on a paved road...) and notice that even with increase the throttle the car simple does not accelerate any more? Or in case of an automatic it simply down shifts to jumps to a higher rpm. Thats the flat spotting i'm referencing. If the Soul has flat spots in the acceleration it may benefit from an after market intake or exhaust. The flat spot is a key indication that the motor has been restricted by factory design. This may be to keep down noise, provide back pressure which effects valve train, sometimes there are restrictions just by fault of the design (Fault of design example: the 2.0L (first generation 85-88 Chevy Cavalier had a 4-1 header from factory, it was a straight bar that had a T shape, so by design it had a faulty flow, later corrected for a cast iron, true 4-1 design which provided an additional 5-10 hp to the 2.0L and 2.2L engines).
:)

Here is the data from last night's testing:

http://i917.photobucket.com/albums/a...7at71515PM.jpg

http://i917.photobucket.com/albums/a...t71515PM_2.jpg

From this data we decided that the warm air does not statistically change the MPG at steady state 55MPH testing.

all cars and all drivers are differen't

besides air intakes and air filters are different when you change out the air intake setup it'll effect it one way or another