Air intake muffler delete on a Pontiac Sunfire
 

I’ve got an eco mod and a performance mod for people with a Cavalier/Sunfire (J-body). Other people can benefit from this too. The steps will be different, but the benefit will be the same.

I remembered that the J-body has an air box or intake muffler in the driver’s side fender. Eliminating this air box frees up the restrictive catacombs that the incoming air has to go through to enter your engine. I did this mod in under 70 minutes including jacking up the car and with the help of pneumatic tools.

How is this an eco/performance mod? This air box is kind of like you running marathon breathing through a straw. If you get rid of the restriction then your car can breathe better and more efficiently. This translates to you not needing to press the accelerator pedal down more than you need to to get going. Less pedal means less gas injected into the engine saving you fuel. And your engine will thank you for it. Just keep you foot out of the pedal because less restriction means your car will be a lot more rev happy.

All you need for this is a jack and jack stands, ratchet set, screwdriver flathead and phillips, pliers, Optional tools, a sawsall and a long blade (if you don’t have one read the article for alternative), compressor, air ratchet, impact wrench and sockets, hammer and punch

On to the mod!

Jack the car up, place jack stands under the car as required (I put them under the lower control arm). If you don’t know where your car’s jacking points are look in your owner’s manual. Take off the driver’s front wheel. It’s a lot easier that way. In the engine compartment, if you have a strut tower bar go ahead and unbolt the driver’s side of the bar with a 13mm ratchet. There is a fuse box that you’ll need to remove that is right over the filter box. All you need to remove that is pliers. Take out the center plug of the fastener, and then you can pull the rest of the fastener out. The other side is only held in by a tab. Lift the front where the fastener was and pull the fuse box up. You don’t need to disconnect any wires you’re doing this just to have room to pull the filter box up.

Unscrew the 4 bolts of the filter box with a flathead or Phillips screwdriver whatever your preference. Unscrew the band clamp closest to the engine/throttle body. Take the plastic ducting along with the top of the filter box and air filter and set it aside. The only thing holding the bottom of the air filter box on the car is a tab next to the firewall. You just need to bend that tab back a little to get the filter box off. If you can’t bend the tab with your fingers then you’ll need a small pry bar or big flathead screwdriver. Be sure to wrap the pry bar/screwdriver in a paper towel so as to not scratch the paint. After the tab is bent take the bottom of the air filter box out. You’ll see the ducting of the box connects to the air muffler in the fender. You can press out one more fastener. It’s the plastic nipple that holds the air intake of the air muffler to the body of the car. It’s down from the plastic fastener from the fuse box that you took off. If you can’t locate it you can just tug it out when the air muffler is free. If you did find it press it out with a hammer and the proper sized punch.

Get down on a creeper (or the floor), take a 7mm ratchet and unbolt 3 bolts that hold the underside plastic on, then unbolt the 2 bolts in the outside wheel well. There are 2 more bolts on the inside wheel well only loosen those. The plastic of the wheel well will still be attached by 2 plastic fasteners at the top, taking these out is unnecessary (and they usually break just enough so you have to buy more from the dealership $2 or 3 each). The plastic will be pliable enough to do what you need to do.

Unbolt the upper bolt (10mm or 13mm depends which year) with the metal tab on the backside of the air muffler. Discard it/recycle it. You won’t use it again. If you already pressed out the air intake of the air muffler in the engine bay you only have one bolt left, but you have to unbolt the windshield washer fluid reservoir. (Thanks GM engineers for making something easy harder to do!) I didn’t do that… I got out my sawsall, put a long blade in it, and cut the backside of the bottom box of the air muffler half way through. ONLY CUT HALF WAY THROUGH! THERE ARE WIRES ON THE FRONT SIDE! Then cut the front of the bottom box. Once that comes off the air muffler comes right out. Button everything back up, clean up and take a test drive.

If you don’t have a sawsall there are coupons in many magazines and even some Sunday papers for Harbor Freight that have sawsalls for around $20. If you don’t have that coupon then I think regular price is $40. That’s good price for any saw. These are good cheap tools, not bad cheaply made tools. If you don’t have a sawsall or don’t have a Harbor Freight store or the like in your area you’re stuck with draining the washer fluid reservoir, and unbolting it to get to that last bolt.

Since doing this I’ve noticed that I don’t have to rev the engine as much to get started. Even starting in 2nd gear isn’t a chore. The engine revs easier. The car doesn’t hesitate when going around a corner in 3rd gear or going up hill in a numerically higher gear. My car is happy and I’m happy because it’s easier to drive.

As soon as the test drive was over I filled up and it’s time to do a mileage test.

See right there is the major fault in your premise that this actually accomplishes anything eco. To extract x amount of throttled power the engine NEEDS to be restricted x amount. The source of the restriction for eco purposes is irrelevant.

Show us a watertight A-B-A.

exacttly, well said FL

It sucks that its such a PITA to remove that from your car it takes about 25min to do it on my Bonneville remove 2 screws and loosen a band clamp then pull up. To remove the intake muffler use a screw driver and hammer at plastic welds, now reinstall air box. I went a step further and opened the front of the box also.

The air box is not really a restriction till you get into high RPMs and the MPG change will be .01-.7 better at most IF driving it the same way as before. The real benefit to this mod is better throttle response, and that can save gas.

Before anyone says anything here is the reason that it can save gas. Having better throttle response means there will be less delay in the engines ability to rev. If the engine can rev easier and faster changes in TPS are easier to detect allowing for more fine tuning of speed when cruising, and less time spent accelerating. In the end the change might not do anything for MPG but it will give a better seat of the pants feel and can allow the driver to better adjust the throttle for more efficient driving.

Frank,
You are almost correct in what you’re saying, but you’re confusing restriction(CFM) and vacuum. Higher vacuum is what gives you more gas mileage. Not higher restriction (lower CFM). The reason for the vacuum is the engine trying to suck air through a partially open throttle body. Because I have deleted the air intake muffler I have better flow to the throttle body; therefore I don’t need to open the throttle body more to get the same acceleration I did before the mod. Because the throttle body isn’t open as much the throttle position sensor ( or TPS) isn’t sending the computer the signal to inject more fuel into the engine.

My modification doesn’t deal with decreasing vacuum it deals with increasing flow measured in CFM. By getting rid of the restriction it can have more flow to the throttle body.
For example, in the world of head porting and polishing the object of the porting/ gasket match is to open up the intake and exhaust runners increasing CFM. Before and after the porting the technician measures the flow. Of course there has to be a constant or a control to see how much more CFM is flowing in and out of the cylinders. That control is vacuum. Let’s say a regular unported 350 head flows 180 CFM at 28 inches of vacuum before the porting. Then after the porting the technician has to have the correct vacuum to make a good comparison of the CFM gain. It’ll still be 28 inches of vacuum.

As far as the watertight A-B-A, this vehicle is to go to work and back which is 20 miles so I use a more realistic test like driving until the tank gets down to 1/4 tank then fill it up and calculate the results.

That will be in about 2 weeks... Can you feel the tension rising?:eek:

[QUOTE=Phantom;249928]It sucks that its such a PITA to remove that from your car it takes about 25min

The air box is not really a restriction till you get into high RPMs and the MPG change will be .01-.7 better at most IF driving it the same way as before. The real benefit to this mod is better throttle response, and that can save gas.

Phantom, thanks for the post. Whether it was a PITA or not. I'm glad I did it.

I've actually done this mod on my girlfriend's (now wife) 2001 Sunfire with a 150k miles on it. It had the older OHV 2.2L engine and an automatic transmission. She went from getting 26 mpg to 28 mpg. It had no other mods done to it. I'm hoping for around that kind of gas mileage but I'm not betting on it. Every little bit helps.

Well... no, not really.

More restriction from the throttle body, more pumping losses, less efficient use of fuel.

as has been said, irrelevant at other than close to WOT(thanks Phantom), as the throttle plate causes far more restriction than the intake pipe ever will

I have good news (for me). I went from a 36.2 MPG fill up to a 37.06 MPG (375.4/10.128) fill up. Let the hate posts begin.

Silvey01, I'm glad to see you're getting better mileage. However, the fact of the matter really is that we have some great knowledgable users here that really do know a lot about engines and how they work, especially when related to efficiency. You can ignore these users, but it really isn't going to get you better mileage. There are a lot of misconceptions out there, and many are wildly proliferated via the internet and car forums. We do a lot of testing here to prove our modifications work (or don't work) which is pretty rare.

That being said, this modification is not responsible for getting you your extra 1 mpg. I would highly recommend looking over the 65+ mods list for staring out ecomodding. Its a very good list. The mods listed are proven modifications that do work.

No one is out to get you! Although some of these posts may not be polite or sympathetic...

Reducing the airflow restriction will increase your performance at wide open throttle, but just cruising it seems like the same amount of air would be going into the engine. It may be possible that you are entering a different BSFC region of your engine with this new configuration, or some other phenomena, although it's unlikely.

If you really want to, you may consider getting more data, including putting it back on and trying it again. My variation from tank to tank is about 5mpg even without changing anything on the car - driving mode, wind speed, temperature.. they all have a big impact.

it's hard to hate stupid........

Stupid like saying one tankful of gas is driven the exact same way of 300 miles as the last tank..........

stupid like ignoring a simple A-B-A test over a flat 10-15 mile stretch using the cruise control to duplicate the drive with the mod and the drive without the mod.

stupid like not reading other posts that discuss the placibo effect (look it up)

stupid like even being so clueless to post the in-your face nanny nanny pooh pooh .......

Alright, he is out to get you

A similar intake mod, called the Keman mod on the ZX2, gained me ~2 mpgs. Is it possible the modification helps due to warmer intake air, instead of air drawn from outside the engine compartment? Maybe, but whatever the reason, I am keeping my intake mod. I have no problem with people saying it will not work, I just take my results and keep plugging away.

If it can net some results - for whatever real reason - grab it.
One mpg here, another one there ... that's how we get there after all.


Just make sure the air intake path isn't so easy that it can scoop up water.

I agree! I have found faster acceleration improves my mpg. That said, obviously flooring it and reving up to redline is not the right idea but accelerating "briskly" so you can settle into a high gear and a stable speed is beneficail. Keeping up with the average driver after a light seems to be about right for me. I also catch less flack from the passangers for driving "slow" that way as it seems to them like I am driving just like everyone else but getting great mileage. I find that small engines like mine have a hard time keeping up without flooring it (not good for mpg at all) so performace mods might net a gain even if they shouldn't in theory. If your engine is already quite powerfull, letting more ponies out of the barn will probably keep milage the same or even make it worse.

Yes, there are some knowledgable people out there who know a lot about engines including my best friend who's an engine builder (not engine assembler), machinist, fabricator and GM tech.

While my engine is very underpowered the air intake muffler delete has in fact improved HP at WOT it has also stopped the hesitation and sputtering when I'm going up hill in a higher gear at partial open throttle as I said in my original write up.

Also, why I only got 1 mpg and not 2 or more is probably because I've been driving with Max A/C on because for the last 3 weeks the heat index has been between 105 and 115 degrees in Missouri. It's not a dry heat either.

I've looked at the modifications on the 65+ mods list and while I agree with most of the mods on there there is no mention on advancing the cam timing (not ignition timing). COMP Cams® - COMP Cams® Valve Timing Tutorial

There's a brief write up on it... If this is confusing basically advancing the cam timing brings the peak power (both Torque and HP) down in the RPM range.

A stock cam usually has peak power in the 4000-6000 rpm range... I know of no one who drives on the highway at this speed. Bringing the peak power down moves the vehicle without the engine "breaking a sweat" like on the hotter cam engines that make all either power up in the upper rpm range. This advance in cam timing coupled with the a economy or "RV" cam would optimize the engine for economy.

Yes, he is.

Considering he has a pompous car and a pompous attitude and only gets 23MPG I don't think I'll take his advise for ecomodding.

Also, my car is a base vehicle... no cruise control and if I could find a "flat" stretch of land that is 10-15 miles in length in Missouri, I'd let him know.

I always check my tanks' mileage even when I don't do a mod. It's just about the same considering I got this car to go back and forth to work only, but I do go on errands for my wife here and there in the "city" and that drops the mileage unforchantly. What can you do?

Autospeed has a great 5 part article on this. It shows that reducing the differential between atmospheric and intake (not manifold) pressure does have an effect on performance at less than WOT.

Eliminating Negative Boost

I doubt GM- or anyone- released new vehicles with built-in hesitation and sputtering. So there is a problem with this vehicle that isn't systemic across all vehicles yet the implication here is that all or some or many vehicles will benefit from a mod that seems to address the problem.

Modding a vehicle with a defect without first getting it to good stock tune is kinda... well... bad form.

It does? Since reading it through was too much like Chinese water torture, I looked at installments 1 and 5. To summarize, at the very end he claims elimination of negative pressure, but also admits to changing several variables AND in the final analysis the vehicle did not produce any more power or fe. Right?

98 Sunfire
 

It breathes in a little better,but a cold air intake would help furthermore.Still a good cheap mod coupled with an high flow air filter.
Thanks for you're post.