cold air intake

rubicondon53 · **Joined:** Fri Aug 25, 2006 6:37 am **Posts:** 15

I run a trail/daily driver 04 rubicon, and am very pleased with my cold air intake from K&N. The skinny pedal is much lighter, with a notable difference in throttle response from idle. I have also improved my fuel mileage by better than 1 mpg. My wife runs our 05 CRD (daily driver and snow beast). Will a cold air intake improve performance with our CRD the same as it has improved our Rubi? any experience to pass along will be appreciated!! thanks!!

BlackLibertyCRD · **Posted:** Sat May 30, 2009 4:47 pm

It already has an cold intake with inner cooler. An cone filter will add no benefits except more dirt. You should replace you air filter every 12,000 miles if running stock filter. Otherwise follow the aftermarket manufactures recommendation for their drop in filters.

Uffe · **Posted:** Sun May 31, 2009 9:16 am

BlackLibertyCRD wrote:

It already has an cold intake with inner cooler. An cone filter will add no benefits except more dirt. You should replace you air filter every 12,000 miles if running stock filter. Otherwise follow the aftermarket manufactures recommendation for their drop in filters.

What he said!

Cold air intake makes no sense on intercooled turbo diesel engines, you cool the air before the turbo heats it up massively, there's little point to it. The intercooler on the CRD is already powerful enough, I highly doubt you will gain anything from a cold air intake.

Another advice, don't use K&N filters on a turbo diesel, it sucks in much more air, and more particles compared to a gasser. Filtration is much more critical, and if you put a K&N on it it will suck in particles en masse because the K&N allows bigger particles to go through. My advice is to keep the stock filter.

danoid · **Posted:** Mon Jun 01, 2009 12:44 pm

I'd be interested in the J8 air filter. It's made by Donaldson. They make big rig filters and the J8 filter supposedly lasts far longer than our little paper things.

Tinman · **Joined:** Mon Apr 10, 2006 10:45 am **Posts:** 308

There are some good aftermarket cold air intakes, but K&N isn't one of them. It's pretty much a glorifed rock guard. At stock power you don't really need them. If you play the hp game, then it can be useful and necessary. If you really want to try a better filter I'd suggest AMS oil EaA or a Afe Proguard 7 (if they make one for the libby). To be safe, do oil analysis to be sure. I ran an EaA on the libby for a oil interval and silicon was OK. But I ran one on my Cummins and i had a concern, so I'm back to paper. If you search the net, you'll find stories of a lot of dusted diesels b/o K&N. The air box assembly would be a better way to help air flow.

gmctd · **Posted:** Tue Jun 02, 2009 11:03 am

Again, size matters: a larger-area filter will pass more air and last longer than a small filter in the same conditions, simple physics - it's the available real estate that puts the crimp in our style - maybe a V- or L-shaped filter element - or surgically alter the inner fender to accept a larger round Donaldson unit

danoid · **Posted:** Wed Jun 03, 2009 8:48 am

The J8 has a cylindrical filter. It fits under the hood of a Wrangler, so it's on the same order of magnitude as our air box. Maybe I'll contact AEV to see if they can get one (USA dealerships can't because it's an export only part).

gmctd · **Posted:** Wed Jun 03, 2009 9:12 am

Understood, danoid - check it out, do some show'n'tell - however, as you know, why go to the effort of installing another filter that has the same surface-area as the oem version? Cylindrical filters typically have smaller cross-sectional dimension than flat-panel filters in order for cannister to fit within constraints of available real estate - I personally like cylindrical filters, side-entrance cannister, flow thru outside filter suface into central area, top exit from that inside-center of cannister - heighth dimension must be such that the resulting 90* angle adaptor to turbo inlet-ducting is not restrictive to max flow - that small-radius 90* right at the KJ turbo inlet is bad enuff, without duplicating it at the filter cannister

Cowpie1 · **Posted:** Thu Jun 04, 2009 2:10 am

gmctd wrote:

Again, size matters: a larger-area filter will pass more air and last longer than a small filter in the same conditions, simple physics - it's the available real estate that puts the crimp in our style - maybe a V- or L-shaped filter element - or surgically alter the inner fender to accept a larger round Donaldson unit

I would agree with that especially on a natural aspirated system like the 3.7 gassers. With turbo charged engines, this is not so much the issue. True though, it will last longer. But regarding air intake, the turbo will grab what it needs for the 2.8 VM since it is a VG turbo anyway.

gmctd · **Posted:** Thu Jun 04, 2009 2:45 pm

Doesn't totally fly, my friend - the turbine-driven compressor merely reduces air pressure at the inlet, and Baro, thru the air filter and ducting, does the rest - however, air, like other fluids, loves to travel in a straight line in as least restrictive a confinement as possible - check out my thread in Haystack for pics of the reduction in cross-sectional area in the rubber duct between the MAF outlet and the turbo inlet - restrict the pump intake and the pump will cavitate, sometimes with disastrous effect, particularly exhaust-gas turbine-driven air pumps - real estate is our achilles heel, tho sometimes engineers use that and other restrictions to "detune" engine output in order to comply with management's warranty mandates

Turbo Tim · **Posted:** Thu Jun 04, 2009 11:20 pm

Just for the curious folk out there. Have any of you looked under the hood of one of those big semi rigs? Ever see the size of the intake hole of the turbo? If so, for those out there that haven’t, it’s about 2 ½ to 3 inches (or so) in size.
Now for the mystery. Ever wonder why they run a 10 inch size pipe (or so) from the air cleaner to that little 3 inch hole?
This is because the turbo will grab all the low pressure air it can to make high pressure air. (For those of you in high humidity areas and if conditions are right, and the turbo intake is open, you will see some neat effects. One time on the dyno, we did a full throttle run and a basket-ball size cloud formed right in front of the intake of the turbo. You could see this little tornado coming out of the turbo scooping up all the air it could. Very impressive).
Once an engineer from Garrett told me to figure about a 110* degree angle immediately off the intake of the turbo if you want max efficiency when building your intake.
This should explain why the size of the hose from the air cleaner on the big rigs to the intake of the turbo. You need to move a lot of low pressure air and it takes big hoses to do it.

gmctd · **Posted:** Fri Jun 05, 2009 4:19 am

FYI: while the observed effect was a tornado coming out of the compressor inlet, actual physics were that the high-speed inrushing air was beginning to spin due to the rotation of the compressor wheel - the rotating air turbulence affords less resistance as the rotating compressor blades cut the inrushing air, requiring less power input from the turbine - and making that highly-desireable turbo-whistle - some compressor inlets utilize ridges and fences to reduce inrushing air rotation in order to improve compressor efficiency - other inlets are smooth-throated, supposedly to reduce that whistle - ?quien sabe

Turbo Tim · **Posted:** Sat Jun 06, 2009 12:41 am

You bet. The other thing to note here is that the changing speed of the air. The cloud you see is because the moisture is left behind because of the changing air speed. It does look neat I have to say.

rubicondon53 · **Joined:** Fri Aug 25, 2006 6:37 am **Posts:** 15

Wow I sure opened a can of worms. As I do drive an 18 wheeler, bout 3k a week, I am somewhat familiar with its operation. You guys have only confirmed what I had suspected all along, that this CRD is the same thing only a whole lot smaller. A buddy of mine is convinced a cold air intake would help the off the line performance, bull, it already cools its own air, and the turbo does the rest!! Sure would like to get my crd's turbo to whine like a cummin's Now that would be cool!!!!!! lateron don

UFO · **Posted:** Sat Jun 06, 2009 8:02 am

rubicondon53 wrote:

Wow I sure opened a can of worms. As I do drive an 18 wheeler, bout 3k a week, I am somewhat familiar with its operation. You guys have only confirmed what I had suspected all along, that this CRD is the same thing only a whole lot smaller. A buddy of mine is convinced a cold air intake would help the off the line performance, bull, it already cools its own air, and the turbo does the rest!! Sure would like to get my crd's turbo to whine like a cummin's Now that would be cool!!!!!! lateron don

I'm convinced the only way to get the Cummins/big rig sound is to use a 6 cylinder engiine....maybe a Nissan LD28 with a turbo conversion.

rubicondon53 · **Joined:** Fri Aug 25, 2006 6:37 am **Posts:** 15

Say UFO,,

We are going to start our vacation next may in the Moab region, spend a few days @ Arches N Park, then Canyonlands, and all the wheelin' to go with it. We are ending our vacation, @ Mesa Verde National park, and plan on wheelin' all around there as well. Do you have any specific web sites or any advise at all about trail head locations, and when or if said trails will be open mid May? I see you are from Colo, and might be familiar with some of the trails in that region, thanks! lateron don

cold air intake

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