Stock Airbox Mods: K&N and Holes in Airbox

[Stratosurfer]

All,
I am working on two new 4" exhaust systems and considering my best options on intake mods. My Burb has no MAF sensor, but the Tahoe does and it seems the aftermarket intake systems are geared primarily for those w/o MAF sensors. I listened to a radio mechanic on the way back from Port Isabel TX last weekend claiming he's punching holes in most all airboxes and his clients are getting 2-3 better MPG. I've scanned the archives and can't find any one definitive thread that shows how a K&N with a 'perforated' airbox performs vs drawing in through the snorkel.
Is anyone running a K&N in the airbox with holes in the box (on the top of the box) and if so how has it affected turbo spool up?
The radio mechanic stated that the restriction on most snorkel systems act as a choke and opening up an airbox and taking in much more air helps everything, even though the air is warmer than at the front of the truck.
All feedback appreciated.

[Hubert]

Its been discussed and normally pulled through fender is preferred to under hood air. But could depend on ambient temps and year comparisons. Early trucks did have a significantly restrictive snorkel. After 96 or 97 with round filter most all agree pull through fender or build an even bigger cold air box and intake path to flow more air but not warm underhood air.

Depending on engine for each something like 9-11F rise in IAT (comparing same boost) you loose 5-10 hp???? Not exact numbers but you get the idea its appreciable. The 190 hp sticker was in cool temperature and in avg summer temps a stock truck won't make the advertised 190 hp. Opening the air box won't help in that case its all about the temperature.

The 6.5 w/o intercooler does not like warm air into turbo from open box or with holes. It might sound louder but performance is not better with open element under hood. If you have a clean radiator and are constantly moving you get a flush and underhood air is not hot. In slow stop and go driving the air under the hood is HOT. There have been a few reports of guys with snow plows melting wire looming near turbo and starter due to hot under hood temps from restricted air flush of underhood air. And thats in cooler weather.

[Stratosurfer]

Thanks Hubert, this is exactly the data I was looking for.

[JohnC]

...claiming he's punching holes in most all airboxes and his clients are getting 2-3 better MPG. ....


Don't you think the manufacturers would have figured this out by now if there was anything to it?

[Stratosurfer]

Don't you think the manufacturers would have figured this out by now if there was anything to it?

The issue for me is this: ALL the aftermarket intakes I've seen for sale for the 6.5 are -not- using any type of snorkel and taking in only warm under engine hood air. All the data seems to conflict in some way: the data Hubert gives, and the systems selling for more more performance.
I'm just trying to take in as much real world experience (results) as possible to make the best move with my intake.
The manufacturers have many objectives, just within the past year has fuel economy now risen back to the forefront.

[Hubert]

Yep advertisements are confusing and you can bet an advertisement is/are biased. Notice there are very few 6.5 intakes all I remember is the AFE shield. The 6.5 trucks have limited space. Its not consuming near the air that the other diesel do. The market is small and declining. Compare to Ford, Dodge, and 6.6 GM trucks and the many boxes. Their boxes are just about all closed (I don't remember an open one). Some have improved scoops and claim to be cold air intakes.

Again cool is the key. More air is better but you have to look at the temperature because more hot air is not better necessarily.

With the later trucks there is not that much restriction in the fender and opening the element up will let in more heat than really increase air intake volume for stock compression and near stock boost.

Go to Kennedy's site and look at the early trucks restrictive snokel and in that case an open element or holes might help.

[sturgeon-phish]

I replaced my plate filter with a round one from a 97 and later model and that helped a lot. Another thing I did was I replaced the front turn signals with a perforated cover and turn signal to let more air in.

http://i126.photobucket.com/albums/p81/sturgeon-phish/Truck/000_0011.jpg
http://i126.photobucket.com/albums/p81/sturgeon-phish/Truck/001_0014-4.jpg
This let in cooler air into the fender and into the airbox.
I remember somone took a grinding tool and removed some of the plastic flange around the original turn signal assembly, to let in more air.
A year or more ago there were several posts about getting more cool air in. If you want more info about my mod, let me know. It was cheap, under $20.

[Stratosurfer]

Yes I believe I saw your mod's sometime in the past. If you have a boost gauge, did you notice any increase in boost at freeway speeds?
Could you send me the link to how you made these mods? Mine is the C/K grill (two sealed hi/lo beams) and may be different but your process would help me.
Thanks

[rhsub]

I've examined my air intake (99 sub) and here is my conclusions
checked air filter restriction guage, it sets at 1.5" of vacuum (not very much restriction)
it draws air from the coldest location possible without doing extensive modifications to fender etc
until I see actual unbias dyno results that an aftermarket system out performs the factory system I am going to spend my money on other upgrades
modifing lighting systems to possiby gain performance is setting yourself up for a lawsuit in the event of an accident
In conclussion I believe that the second design air intake system is pretty good for all but extensively modified applications ie larger turbos etc
Just my 2 cents worth
Ron

[sturgeon-phish]

Here is how I did it
1. Obtain
a. two amber turn signal assemblies from parts store
b. some scotch loc wire connectors
c. ¼ sheet metal screws,
d. ~ 6” of ¼” tubing
e. Sheet metal material to make bracket for replacement turn signal
f. enough perforated sheet metal material to cover the opening created by removing the turn signal assembly
2. Remove turn signal housing from grill by unscrewing the 4 screws, keep the screws
3. Remove lamp bulbs from lens housing
4. Make a bracket from sheet metal to attach replacement turn signal assembly inside the hole
5. Attach the replacement turn signal to the bracket to the front end of the radiator support in the hole centered top to bottom and towards the center of the truck ( see pic) being cautious not to puncture anything behind the grill support
6. Connect appropriate wires with scotch locs
7. Take second turn signal bulb assembly and wire tie to bracket where it will look OK. (If you remove the bulb you turn signals will recognize this as a burnt out bulb.)
8. Test turn signal for proper operation
9. Cut the perforated sheet metal to fit inside the turn signal opening,
10. Place the perforated piece in the opening and mark for the screws to attach the housing to the grill front, drill as necessary
11. Slightly bend the perforated sheet metal to match the contour of the grill front
12. Insert the screws in the holes to attach the perforated cover
13. On the inside of the screws slip ~ 3/8 to ¼ piece of tubing over the screws. This is just a spacer to bring the cover out flush
14. Repeat for the other side

http://i126.photobucket.com/albums/p81/sturgeon-phish/Truck/001_0013-7.jpg
http://i126.photobucket.com/albums/p81/sturgeon-phish/Truck/001_0014-4.jpg
http://i126.photobucket.com/albums/p81/sturgeon-phish/Truck/000_0012-5.jpg
http://i126.photobucket.com/albums/p81/sturgeon-phish/Truck/001_0016-4.jpg
http://i126.photobucket.com/albums/p81/sturgeon-phish/Truck/000_0002.jpg

[Stratosurfer]

Phish,
Where'd you source that perforated stainless (or whatever metal) for the grille?

[Hubert]

Did you check out the article on overheating LLY in the summer issue of the GM diesel Mag.

Its about the stock 2005 6.6 (LLY) having an open to under hood air intake. It runs hotter when towing and engages the radiator fan when making significant boost from the added heat of warm intake air.

The GM solution was the LBZ intake and sealing up the intake box to outside air as in a more factory cold air intake.

Another arguement for closed box.

[DennisG01]

As eluded to above, here's a before and after of what I did to allow more air in. I currently run an open K&N filter with a better, smoother intake tube going to the turbo. I never noticed any marked difference (both EGT's and seat of the pants) between stock and what I currently have. My theory is although I'm sucking in warmer air, I'm also sucking in more air so it sort of cancels out. But, the best thing would be a larger box. I'll get to it eventually...:rolleyes:
http://www.thedieselpageforums.com/photopost/data/519/Grill_Opening_-_Before_-_Small.JPG
http://www.thedieselpageforums.com/photopost/data/519/Grill_Opening_-_After_-_small.JPG

[ronniejoe]

The 190 hp sticker was in cool temperature and in avg summer temps a stock truck won't make the advertised 190 hp.

Those are sea level standard day numbers (i.e. 14.7 psi ambient and 59F)

[sturgeon-phish]

Phish,
Where'd you source that perforated stainless (or whatever metal) for the grille?

I salvaged it from the side case of some old computer equipment. A similar source is the metal drop in cold air return panel for suspended ceilings.

If I were to do it again, I use the method of removing the extra flange material. I think you effectivly have the same result for no money, and retains stock appearance.
Jim

[enforcer233]

Has anyone with one of the box style replacement kits, like AFe, actually installed a small hood scoop above air box to allow cold air in from above?

Reading this thread made me thiink about a smaller size scoop like the 70's firebirds had with some perforated sheet metal between the scoop and the intake to keep some of the bugs out.

[Hubert]

Those are sea level standard day numbers (i.e. 14.7 psi ambient and 59F)

Yeah, you have to base on some standard for testing purposes and I did not mean to exaggerate they were intentionally misleading the hp rating. But summer temps for a lot of driving hours can be 85-95F or more ambient easily and higher under the hood. Moving at highway speed you get a flush of air that keeps things from getting too hot but 35 mph towing a hill underhood temps rise.

I'll venture a guestimate that if the engine breathes 95 F air it would only make about 180hp ??? or less if it made 190 hp at 59F air temp. 105-115F??? underhood air would only be worse. I think I am being conservative but want to point out that a low restriction sealed airbox is a good thing compared to an open element especially w/o some intercoolering of some kind. Maybe the affects are not so bad cruising light down the highway but 35 mph uphill with higher EGT and ECT or in stop and go I am pretty sure affects are bad.

[ronniejoe]

Yes, and add to that the effects of high relative humidity that we encounter everyday, the power really goes down.

[Hubert]

Has anyone with one of the box style replacement kits, like AFe, actually installed a small hood scoop above air box to allow cold air in from above?

Reading this thread made me thiink about a smaller size scoop like the 70's firebirds had with some perforated sheet metal between the scoop and the intake to keep some of the bugs out.

The aerodynamics are funky for these hoods. I think a lot of the top of the hood won't push air into a scoop. Thats the reason behind the cowl induction. I have seen a post on a scoop cut into the side of the fender. Seen the factory do on it a good bit on bigger trucks too. Not so much on the top of the hood at least for trucks.

[JohnC]

Yes, and add to that the effects of high relative humidity that we encounter everyday, the power really goes down.

Yeah, but, except for the guys like RJ running on the ragged edge, these engines usually run with an excess of air anyhow, so the power loss is minimal. A turbocharger can make up for a lot of ills... :)

EGT on the other hand....

[Stratosurfer]

I am considering on my next re-paint to install an small NACA air-inlet scoop on my hood just above the factory airbox. My plan will be to put a doughnut gasket around a hole I cut in the top of the box that mates with the discharge end of the scoop when the hood is lowered. This would provide an additional 'semi-pressurized' source of cold air to the airbox and be pretty simple in operation. I haven't fully determined how to evacuate water from a rainstorm from the box (tiny weep-hole(s)?).
This is just a thought for now, I need to have my gauge pillar pod installed and get some data before I consider anything. I'm leaning toward the trim-ring 'trim' job idea posted on this thread. My old C/K grille on the Tahoe with the sealed beams looks as to flow 4x the air as the LS/LT grille to the snorkel inlet.
These small NACA air-inlet scoops are off the shelf items at experimental aircraft suppliers such as Aircraft Spruce, I had them on an Long EZ I owned in the past. They're very efficient in minimizing drag while providing maximum flow.

[enforcer233]

It would only make sence that a scoop on the hood or the fender would work to increase air flow and allow cooler air in. If not why did cars in the 60's and 70's have cowl indiction, ram air and shaker intakes.

When I look at the profile of my 97 surbirban It sould seem to me that air could be easily taken into a scoop. But I will say that without a wind tunnel and smoke wand it would be difficult to say for sure.

I guess you could go with a snorkel intake like you see on some jazzed out off road vehicles where the air comes in at the roof above one of the A pillars but that would be a little excessive unless you plan on driving through five foot deep waters; I think not!

As far as water getting in. If the scoop is on the side of the fender gravity will eliminate most of it betore entering the air box. Of course that is speculation on my part. Otherwise some deflector between the opening and the filter would allow the water to run down to a weep hole.