modified stock intake

[timfretwell]

I was inspecting the stock air intake on my 94XLT the other day, and I did two things that I believe are improvements that only take a few minutes. If you follow the tube from the air box to the grill, you will see that the tube screws to the inside of the grill. On the "front" side of the grill is a square black cover that covers the intake hole. The cover has a slit in the bottom and side. This seems to really restrick air flow. I laid on the ground and with a long flat blade screw driver, I was able to pry the cover off. Next, on the front of the grill beside the head light there is a rubber flap attached to a plastic bracket. This flap simply pulls off. This allows air to flow directly from the grill straight into the intake tube. The plastic bracket(without the flap) actually acts like a fin to divert air to the intake.

I can't tell any difference in highway performance, but I do think the city performance is a little better. I am currently checking to see if it will help my gas mileage any. I'll keep you posted...

 

[clark91Jo]

Hey Tim, cool idea. I have thought long and hard about the air intake too. I was thinking of just taking off all that tubeing off from the grill to the air box just until I get the KKM kit. I don't think much if any water would splash up there, besides the aftermarket ones are open anyway. Back to my thought, the tube that runs from the throttle body to the MAS has all those flex, rippled bends and that flat spot. This can do nothing but distrub the air flow. I think I have figured a way to make my own air intake tube. I think I will use PVC or conduet pipe, only thing is the throttle body is about 3" and the MAS is about 4", I think. It has been awhile since I measured. Anyway, with some PVC glue, pipe and rubber to make gaskets, we could easily make one since K&N won't make one. I think that would greatly improve performance. If you think of something cool on this, let me know because I should start soon.

Clark

 

[Brian1]

Sounds like a good idea. Have you thought about or drilled holes in the air box? Alot of people have done this here on the board.

 

[timfretwell]

Originally posted by clark91Jo
Hey Tim, cool idea. I have thought long and hard about the air intake too. I was thinking of just taking off all that tubeing off from the grill to the air box just until I get the KKM kit. I don't think much if any water would splash up there, besides the aftermarket ones are open anyway. Back to my thought, the tube that runs from the throttle body to the MAS has all those flex, rippled bends and that flat spot. This can do nothing but distrub the air flow. I think I have figured a way to make my own air intake tube. I think I will use PVC or conduet pipe, only thing is the throttle body is about 3" and the MAS is about 4", I think. It has been awhile since I measured. Anyway, with some PVC glue, pipe and rubber to make gaskets, we could easily make one since K&N won't make one. I think that would greatly improve performance. If you think of something cool on this, let me know because I should start soon.

Clark

Yes, I agree. The ribbed surface of the stock tube will slow the air velocity. I took a fluid dynamics cousrse while in engineering school, and you are right, because the air will move faster if the interior walls of the tube are smooth.

I believe pvc comes in 3" and 4" standard sizes. Some places even sell a black pvc, which would obviously look better under the hood. You could start at the throtle body with 3", then use a 3x4 coupling to size up to 4" going into the MAS. You want to size up as soon as possible after coming out of the MAS. When the air goes from the 4" down to 3", it actually increases in density somewhat. More air density is what we want for more HP! I would be curious if you couldn't do the same thing going out to the grill, rather than sucking that hot engine air? Be sure to show us some pictures if you try it. It's been too cold here for me to get out and try anything. (My next home will definatly have a garage)

 

[timfretwell]

Originally posted by Brian1
Sounds like a good idea. Have you thought about or drilled holes in the air box? Alot of people have done this here on the board.

I'm interested in the air box holes, but want to know more about it before I break out the black and decker and get carried away. I wonder if anyone can tell us if they really experienced any performance or mileage improvements with this mod. I'm still not too sure about the hot engine air. If people are definately getting results I will probably give it a try. We could always put it back with a replacement box from your local salvage yard. If you try it, let us know about the results.

 

[clark91Jo]

Thanks for the info Tim. Won't be until next weekend or after that I will have time, and yes trying to get warm too.

 

[TymeKeeper]

I drilled my air box about a year ago, I noticed a bit more acceleration, I don't think the hot air makes a difference, because I still have the inlet from under the grill.. Works great for me.

 

[timfretwell]

Originally posted by TymeKeeper
I drilled my air box about a year ago, I noticed a bit more acceleration, I don't think the hot air makes a difference, because I still have the inlet from under the grill.. Works great for me.

What type of hole did you install? Can you tell any difference in the sound, or any improvment in gas mileage? I think your probably right to leave the stock feed tube in there, especially if you do much sitting at stops lights during the summer. That way you engine still gets some fresh air. Thanks for the info.

 

[TymeKeeper]

I drilled about 25 1/2 holes on all 4 sides of the box...Swiss-cheesed it heheh. I notice a sound difference, and a bit of performance change...but no real gas miliage difference. Took a few miles for the computer to catch up with the mod.. I'm thinking about putting in a few more holes just for the added air. Also I have heard about moding the intake tube that comes from the grille area.. Using a screwdriver to open a flap or something..I haven't looked at it yet.

 

[Cameron]

Originally posted by timfretwell

...When the air goes from the 4" down to 3", it actually increases in density somewhat. More air density is what we want for more HP![/B]

I don’t think the air would become denser because it is being sucked in as apposed to pushed in. If you were forcing the air down the tube to the intake manifold (as in supercharging or “ram air”) then yes, it would become denser as the tube shrank in size. But because the air is actually being sucked into the manifold (as our normally aspirated motors do) I think coming down to a 3-inch pipe from a 4 inch pipe would actually be restrictive. I think a gradual tapering from 4 to 3 inches is probably best.

Don’t quote me on this. Just a thought!

 

[91xltTerd]

Are yall sure that the hood will close with a 3 or 4 inch piece of pvc running across the top of the radiator. Just doesn't look like it would fit to me, but i haven't tried it.

Chip

 

[Cameron]

The pipe wouldn’t run on top of the radiator. It would run between it and the motor. Not unlike the stock intake (at least the stock intake on my 97 4.0).

 

[91xltTerd]

I just looked at mine and it runs right on top of the fan shrowd and I still don't know if there is room for a 4" maybe a 3". My hood seems to go down within about an inch of the flat part of the rubber hose.

 

[97bignslow]

holes

I drilled the holes in my air box last year. I noticed an immediate difference in MPG, and throttle response. I did replace my air filter with a K&N at the same time. I have not noticed any drawbacks after doing this.

In reference to the PVC idea. It sounds good, but be careful what PVC you use. It's not different colors because of style or manufacture. Certain PVC's can not be exposed to ultra violet rays, high temperature, certain chemicals... Make sure you check the chemical makeup of the one you decide to use.

Timfretwell...
The plastic flap you removed from the front of the air intake at the grill... isn't that there to protect the intake from driving rain, insects, debris... Make sure your not taking in things from the front of the truck you don't want.

Eric

 

[clark91Jo]

Ya'll are right. The flat spot on '91-'94 exploders is because of the hood clearance. I have removed my belt driven fan and shroud and replaced it with an electric fan so now I have room for 3" pipe. I will most likely use black PVC because of light weight. The ultra-voilet light sensitivity has to do with burst strength becuace that is how pipe is rated. 1. This will be under the hood, 2. I'm not running water through so am not worried about PVC break down, and 3. Black is not affected by sunlight. Looks like I am pushing up the date still but will let you know when I get it done.

 

[timfretwell]

intake mod

Originally posted by 97bignslow
I drilled the holes in my air box last year. I noticed an immediate difference in MPG, and throttle response. I did replace my air filter with a K&N at the same time. I have not noticed any drawbacks after doing this.

In reference to the PVC idea. It sounds good, but be careful what PVC you use. It's not different colors because of style or manufacture. Certain PVC's can not be exposed to ultra violet rays, high temperature, certain chemicals... Make sure you check the chemical makeup of the one you decide to use.

Timfretwell...
The plastic flap you removed from the front of the air intake at the grill... isn't that there to protect the intake from driving rain, insects, debris... Make sure your not taking in things from the front of the truck you don't want.

Eric

I think your probably right, the flap in the grill was intended to prevent rain/debree from entering the intake. (Thats why I put it in the back of the car just in case I encounter problems in a storm or something). However, I've been driving for several weeks now, in different weather, and have had no problems. In fact after three tanks of fuel, I've confirmed an increase in mileage from 12.5 to 13.9 MPGs in city driving. Thats about 22.4 more miles per tank, or roughly a $2.40 savings!(okay, I'm CHEAP) And this is with a stock air filter. I will probably upgrade to the K&N filter next to see what difference that makes.
Happy Exloring!

[Edited by timfretwell on 01-18-2001 at 05:05 PM]

 

[ChewieM16]

timfretwell, hows your engine goin with that piece removed still? i just did that to my truck today, so id be great to see what i have to look foward to.

-mike

 

[timfretwell]

Originally posted by ChewieM16
timfretwell, hows your engine goin with that piece removed still? i just did that to my truck today, so id be great to see what i have to look foward to.

-mike

Mike,
The mod is working great. I definately think its better this way. I believe there is a little better response around town, and a small MPG increase(maybe not as much as previously reported). I noticed something new over the weekend. The intake has a baffle that opens to let HOT air in from the exhaust manifold when the engine is cold. According to the Haynes manual, this is to warm the engine up faster, reducing emissions. Thats all fine, but AFTER the engine is warm I'm sure some hot air still gets sucked in through this duct. I plan to remove the duct and reroute the hot air tube forward to pull in cold air from the grill area. After I know the performance and MPG affects, I'll make another post.....

 

[ChewieM16]

really? wheres this flap?

i also just removed the lower half of my air box today, while its out i plan to cut huge hols in it to let more air in.

 

[InNeed]

Originally posted by clark91Jo
Back to my thought, the tube that runs from the throttle body to the MAS has all those flex, rippled bends and that flat spot. This can do nothing but distrub the air flow.
Clark

Clark,
I was thinking (doesn't happen often), I haven't looked at it but the ripples before the MAS might be ment to disrupt air flow so that the MAS gets an accurate reading. If the air is just sucked into the MAS it could have different densities in it and the ripples cause the air to be mixed up so there aren't false readings. Its like frozen orange juice concentrate, if you pour the concentrate in and don't mix it up. All of the OJ goes to the bottom of the container and it tastes bad and you think there isn't enough OJ in the water when all you actually have to do is stir it. Intake manifolds have ripples also to keep the air and gas mixed. Does anyone else know if this could be true or not?
Just a thought,
Matt