chin spoiler, low gas mileage?

[JRB73IN]

So I need some help with something. A long time ago I added an 18" piece of aluminum tubing down out of the stock air box, and flipped the plastic behind the fascia on the left side to force air toward the tube, this I thought seemed to increase our gas mileage a mile or two. I just recently added the chin spoiler which is about 2+ inches deep so it has increased the amount of air being forced into the area where the tube is, so I notice that since I put it on I have lost 2 miles per gallon. I am trying to fiqure out if I need to cut down the tube or what, Having the tube is basically giving me cooler outside air, but It is causing a pressure I think on high way driving, forcing more air and pulling more gas. Any engineers out there got an answer or idea? It seems like you can just watch the gas gauge drop on the interstate, even though the computer is saying I am pullin like 22mpg, which was 24 hwy mpg normally.
http://i105.photobucket.com/albums/m219/JRB73IN/car/100_2851.jpg
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:modding::deadhors::deadhors:

[MikeEast]

Hard to see where a chin spoiler could make that big of a change - even if your tube was causing a 'pressure event' to the air filter, the motor is only going to inhale what it needs, it isn't like you have a supercharger effect there.

If anything I'd theorize that there is a more pressure on the nose of the car now, creating more drag, since there is now a wedge pushing air up instead of it sliding cleanly underneath the car.

Mike

[JRB73IN]

It just seems funny that the guys with daytonas seem to get the good gas mileage too. My wife says she thinks it is just because it has 48K on it, I did just add a catch can yesterday and I looked inside the throttle body and ugh, it is nasty in there! But I saw a noticable differnce the weekend I put on the spoiler. I also noticed the car seems to look more raked. Is there any cleaner to run through it?

[boggart]

Take the spoiler off, see if it goes back up. If it does, then put it back on, see if it goes down again. If it does, put the airbox back to stock and see what happens. I suspect that your "ram air" is doing nothing other than giving you the satisfaction of modding your car.

[Walt SRT8]

I did just add a catch can yesterday and I looked inside the throttle body and ugh, it is nasty in there! Is there any cleaner to run through it?


Pull the TB and spray the inside of the intake manifold with TB Cleaner and swab out with a clean rag. Continue until the rag is clean. You can also run some "Seafoam" through the system.

[Gentile Giant]

When the Olds 442 had the W-31 package, it came with 2 scoops under the bumper that feed directly into a sealed air cleaner. ALL test showed it was good for at least a 1/10 in the 1/4.
I believe you are on the right track especially if your city mileage didn't change much at all after your mod.

[FloridaRT]

When was the last time you changed spark plugs....................

You mentioned you have 48K miles on it.

Bob

[MagNite]

When the Olds 442 had the W-31 package, it came with 2 scoops under the bumper that feed directly into a sealed air cleaner. ALL test showed it was good for at least a 1/10 in the 1/4.
I believe you are on the right track especially if your city mileage didn't change much at all after your mod.

Yeah, making the air cooler and denser on the old carb type cars was an easy way to get HP, but with todays air sensors and computer controlled cars, could be that the computer is sensing a higher air mixture and is enriching the fuel mix to compensate thereby using more gas. Kind of the same reason putting a turbo on an engine uses more gas. I'm not an engineer, but that's my reasoning. Any body else got an idea?

[FL3JM]

There shouldnt be any diffrence at all. In order to get obove atmospheric pressure (normal pressure that is) you have to drive like 120mph just to get somewhere near 1.5 psi. (Yes, ram-air is pretty useless in that aspect.)
The benefit is that you get colder air, BUT, having it suck air very close to the ground can actually increase the temperature of the air sucked in if its a sunny day due to the air getting heated up by the ground. (This is where the ram air is great, cause its not close to the ground.)

Oh and the thing about using a turbo; yeah it might increase fuel consumption a bit BUT cars that are made with a turbo usually have smaller engines and therefor use less gas than a bigger engine while still having the same amount of HP and torque.

[JRB73IN]

So I finally cleaned the throttle body, it was filthy and I installed a piece of tube similair to the pic above but only 6 inches long and inside the neck that goes from the air box to the TB. It basically gets rid of the ribs in the tube. I also noticed that someone asked about spark plugs, I am at around 57K and have never changed them, is that something that should be done already, I have always thought it was 100K for plugs. I would have liked to clean out the intake, but wasn't sure what would be needed to tackle that. Anyone got a list of necessary gaskets?

[Magnum P.I]

I believe the HEMI motors need the plugs changed every 30K.not sure as i only have the V6

[ssprntja]

Magnum PI is correct change the plugs in the Hemi every 30k. I bet that will make a difference. Maybe change them twice now to make up for it. :)

[Warlock]

USE Champion plugs

[schexy1]

There could be other factors like quality of the gas you are using. Did you change grades or station? Did your station change suppliers? I try to buy gas at the same station all the time. It is not as bad now, but a few years ago there was a noticible difference in milage and performance between places like Cheveron and 7eleven. Places that didn't have a roof or covered pumps like GasMan would give my Gixxer the flu.

[JRB73IN]

I have notice a large improvement since I cleaned the throttle body and installed the tube in the intake neck. I can be running 65, 70 and still watch my mpg go up, of course the best has always been around 55, but I am averaging 2 mpg better on my average now. was down at 17, due to more intown driving but now I am staying above 19! TB cleaning is definatly recommended, now I just need to get my plugs done. So, why Champion? certain style?

[Carbon27 AutoSports]

its the pressure on the front of the car like MIKE EAST said. your creating drag , which is slowing your car down. it may not seem like much , but everything makes a big difference when cruising 70+

[Carbon27 AutoSports]

its just like attaching two 11x11" metal sheets vertical and perpendicular to the side of the car. the air is being PUSHED out of the way instead of flowing along the cars exterior. try and stick your hand out with soemthing that size pushing directly into the air. ITS VERY DIFFICULT, and your car now is having to work harder to maintain the same speed.

[JRB73IN]

update, I have now added a CAI given to me by DANTRA, but still kept the down tube to get more airflow, and guess what, better gas mileage and more power when you want it, I can really feel more pull out of the car now. I made a heat sheild with some folded aluminum flashing and some siliconed wire molding. Turned out ok I think. Here are some pix.
http://i105.photobucket.com/albums/m219/JRB73IN/218.jpg
http://i105.photobucket.com/albums/m219/JRB73IN/212.jpg
http://i105.photobucket.com/albums/m219/JRB73IN/213.jpg
http://i105.photobucket.com/albums/m219/JRB73IN/0_214.jpg
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http://i105.photobucket.com/albums/m219/JRB73IN/0_217.jpg
http://i105.photobucket.com/albums/m219/JRB73IN/0_221.jpg

[fireman2118]

All the above and clean your air filter.

[hop2000]

I have notice a large improvement since I cleaned the throttle body and installed the tube in the intake neck. I can be running 65, 70 and still watch my mpg go up, of course the best has always been around 55, but I am averaging 2 mpg better on my average now. was down at 17, due to more intown driving but now I am staying above 19! TB cleaning is definatly recommended, now I just need to get my plugs done. So, why Champion? certain style?

Champion Copper Plugs are recommended by Dodge and are also very inexpensive. Don't waste your money on some $7+ iridium or platinum plugs. However, with that many miles on your car, I would make changing the plugs out a TOP priority. Maint. schedule shows replacing the plugs every 30,000 miles as everyone else has mentioned. You are definitly overdue.