I don't need more air!

[tracer]

The guy from Pittsburg Power says that when you have an aerodynamic truck with tucked away air filter housing, your engine gets a much warmer air than a conventional truck with 2 air breathers outside of the truck. They suggest installing a second air filter/housing (like the Ecolite made by Donaldson) to get more COOL air to the engine. Anyone did this on an aerodynamic truck? I have a 2004 International 9400 with 1 huge air filter/housing on the passenger side under the hood.

Here's an interesting quote from some past articles on power and performance I found on pittsburghpower.com

Most truck manufacturers supply an air filter and housing with enough CFM (cubic feet of air per minute) to satisfy the horsepower of the truck when it's being built. If you purchase a used truck with a 290 or 300 HP. engine then rebuild the engine to 400 or more horsepower your air filter is too small. Almost all trucks with the air filter stuck under the hood suffer from lack of cool air. This is the new aerodynamic look with the filter under the hood. However, it is terrible for performance. Why preheat the air before it gets to the turbo? Think about how hot it is under your hood in the summer when your 3,500-lb. engine is operating at 185 degrees and your air filter is right above it. We all know what high pyrometer temperatures do to aluminum pistons. Heat and metal fatigue are a trucker's biggest enemy. If you do not own a conventional, or cannot mount your air filter out in the air stream, then mount a second filter under your hood on the opposite side of your current filter. On a cabover it's fairly simple to mount a secondary air filter and plumb it into your existing air pipe going to the turbo.

The most economical and easiest filter and housing to work with is the Farr Ecolite. At 24" long and 13.5" in diameter, this filter has an amazing capacity of 1500 CFM The price is $139 and for installations you need two clamps at $15 each. The air inlet and outlet is 7" in diameter and you will have to obtain 7" aluminum piping to complete the installation. The extra clean air entering your engine will lower your pyrometer temperature and allow your engine to run as it does on a cool, damp night."

[allan5oh]

Meh, I'm beginning to really question this guys logic.

The air is being grabbed from the outside, how is this any different from a "classic" truck? They both grab it from the outside.

I don't see how the air filter unit inside the truck is going to make that huge of a difference. Besides, with a classic you have all the ducting under the hood anyways.

Until I see some testing (turbo inlet air temps) I don't believe it. The size and efficiency of the CAC has much much more to do with engine air inlet temps then where the filter is mounted...

[tracer]

I don't see how the air filter unit inside the truck is going to make that huge of a difference.

Try touching your air filter housing (I bet it's next to the turbo) after a day's long drive. If it's hot, the air filter is hot too, and it acts like a heating element of a stove when filtering the incoming air. What's wrong with this logic?

[NotSteve]

I'm only guessing on this but I don't think really cool air effects engine performance that much.

The reason I say this is you can do a technique like strip mining and reducing the air line from 12" to 6" to 3" to 1 1/2". Increasing the velocity of air reduces it's temperature by a great deal.

As an example. Take a front steer tire fresh off a truck with the inside air temp at 150 degrees. Take the needle valve out of the valve stem so the air comes out. It will be about 0 degrees and form ice balls.

[allan5oh]

I don't see how the air filter unit inside the truck is going to make that huge of a difference.

Try touching your air filter housing (I bet it's next to the turbo) after a day's long drive. If it's hot, the air filter is hot too, and it acts like a heating element of a stove when filtering the incoming air. What's wrong with this logic?

The piping will also be hot, if that logic holds true. Yes the outside might be a little warm on ONE side, but the filter doesn't touch much of the filter housing.

Like I said, turbo inlet temps, has to be tested. And the CAC makes much more difference.

[bob h]

Meh, I'm beginning to really question this guys logic.

The air is being grabbed from the outside, how is this any different from a "classic" truck? They both grab it from the outside...

Agreed. Any difference between 'outside' and 'filter housing' air temperatures would be minimal and irrelevant... imo. Huge volumes of air flow through that pipe during engine operation... there's not time for the air to heat up.

[tracer]

Take a front steer tire fresh off a truck with the inside air temp at 150 degrees. Take the needle valve out of the valve stem so the air comes out. It will be about 0 degrees and form ice balls.

Hm, I should try this trick on a hot day, instead of running the A/C

[pdm]

The temp that matters is entering the engine from the intake. A scan tool will display this if you want see if it can be improved on. The air leaving the turbo can be upwards of 300 degrees F.

I'm pretty skeptical of most claims of aftermarket products & additives. It seems to me that the engine manufacturer would have to approve the truck oem's installation in the chassis.....

As for the air being cool coming out the valve stem thats the basic principle of refrigeration.........lowering the pressure on something lowers the temperature. Freon is under pressure till it hits the expansion valve (or orifice tube as the case maybe) where the pressure is reduced which lowers the temperature.

[tracer]

I finally got a response from CAT Call Center and the verdict is I don't need more air.

Here's my original question.

Could you please help me with another question regarding the AIR FLOW? I need to know how much air flow in CUBIC FEET PER MINUTE my CAT C15 Serial BXS***** needs at the maximum horse power rating? I bought this truck with 435 hp rating, but then later rerated the engine to 475 hp. I now plan to rerate it to the maximum available rating of 550 hp, 1,850 lb/ft torque and I need to know if my current air filter will provide enough air. So, the question again is: how much air flow in CFM Cat C15 BXS***** will need at 550 hp. Thank you very much.

And their reply.

The CFM for a BXS with 550hp goes in a range but if you use anything over 1,600 C F M will be sufficient to handle that horsepower. Your current air filter arrangement is the same as they use for all the hp arrangements, so yes your current air filter is sufficient for the 550 horsepower. But in order to go to a 550 hp you will need to check your transmission and make sure it can handle the 1,850 Torque. and make sure your cooling system can handle it as well. Thanks for your interest in Caterpillar.

[special k]

Any time you can get cooler,denser air that is a good thing. That has been proven a million times. I don't agree with everything Bruce has to say but he is right on this topic. If I'm not mistaken the 9400 series picks up air at the grille but runs it through a passage in the top of the hood over the engine and then goes into the actual housing which is still over the engine. So I would say there is enough time to heat the intake air noticeably. If you think any truck mfg hasn't cut corners on fuel economy/power to save a few bucks for themselves I could sell you a bridge or two.

[tracer]

If I'm not mistaken the 9400 series picks up air at the grille but runs it through a passage in the top of the hood over the engine and then goes into the actual housing which is still over the engine.

It took me a while to figure it out: the main air inlet is next to the bottom of the windshield, in the very center of the rear part of the hood. From there the air goes via a huge plastic hose located just above the cylinder block and into the air filter housing which is fastened to the firewall on the passenger side - 5 inches away from my dual turbo. I wrapped the filter housing with some anti-heat material ... but both the housing and the air hoses still stay hot during the engine operation.

It's funny how old ideas can still be found in new trucks ... I had 2 flat tires on the company trailer today (!) and a GMC cabover tire truck showed up... While the guy was toiling away at the tires, I looked at how his air inlet was positioned. Because it's a cabover, they don't have enough space in the front. The air filter housing was behind the cab on the passenger side, right in the open, and close to the ground. A vertical plastic air pipe came out of it ... probably 3' in length, and at the top was a ... plastic round air cleaner! Well, it looked like the one on a Peterbilt, only it was much smaller and devoid of chrome, and actually it was not an air cleaner but a round air inlet - very much resembling a mushroom. An interesting design... I bet the housing and air pipe/inlet on this GMC cabover stay much cooler than on my Cat.

[mudpuddle]

Bruce recommends the big 15 inch exterior air cleaners for two reasons. One is the cooler inlet temps. The other and probably more important reason is the much less restrictive ducting. I am sure you have heard the sucking whooshing sound when your hood breaks the seal on the inlet ducting when you hit a big bump. The intake ducting on those trucks is very restrictive. Same thing happens when you put a large tube cold air kit on a car. Cooler more dense charge. Bruce says it somewhere in his writing, one change doesn't make the big difference its all the little things that add up.

[bob h]

Any time you can get cooler,denser air that is a good thing. That has been proven a million times. I don't agree with everything Bruce has to say but he is right on this topic. If I'm not mistaken the 9400 series picks up air at the grille but runs it through a passage in the top of the hood over the engine and then goes into the actual housing which is still over the engine. So I would say there is enough time to heat the intake air noticeably.

That's incorrect; the 9400 "I " has an inlet duct in the cowl tray at the top of the firewall... inlet air flows over the hood, as opposed to integral air ducts in (or under) the hood. Older models (previous to the "I" series) grabbed air from a vent on the side of the cab.

I've encountered many manufacturing flaws in truck engineering... but, never had a problem with underhood air cleaners heating the inlet air sufficiently to cause a driveability concern... maybe before my time? Do people really think there's that much less airflow under the hood?? what exactly STOPS the air from flowing under the hood? most vehicles I've ever been involved with are designed to allow excellent underhood airflow... otherwise the engine overheats........ winterfronts

[allan5oh]

Bruce recommends the big 15 inch exterior air cleaners for two reasons. One is the cooler inlet temps. The other and probably more important reason is the much less restrictive ducting. I am sure you have heard the sucking whooshing sound when your hood breaks the seal on the inlet ducting when you hit a big bump. The intake ducting on those trucks is very restrictive. Same thing happens when you put a large tube cold air kit on a car. Cooler more dense charge. Bruce says it somewhere in his writing, one change doesn't make the big difference its all the little things that add up.

This is where I completely disagree.

Look at the intake of those outside cans. Most of them are very small.

Then you have to look at the filter element, the air comes down the filter element on the inside of it, goes through it to the outside, then further on to the engine.

With my Volvo, it has a huge air inlet in comparison to those two cans put together. Then you look at my filter. It's a monster. It also flows from the outside in, not inside out. This adds a LOT of surface area.

What are the dimensions of those filters in the cans? What about the air inlet area of the filter?

[allan5oh]

Personally, from what I've seen, air filter systems are massively oversized to begin with. I've never had my filter minder register anything. That goes to show how good the air filter system is on a Volvo.

Now if you're making 800+ hp, maybe that's a different story.

But to be honest the biggest advantage a classic truck has is the dual pipes. But if you have an aero with dual pipes, you're laughing. The exhaust system on a classic with dual pipes seems more restrictive then the exhaust system of an aero with dual pipes. The aero has much less bends to it. Of course, it depends on which model of classic.

[pdm]

There was an interesting article in Cat's Truck Engine News letter a few years back. On a cool night the denser air helps the engine produce a little more power, more efficiently but the energy required to move the truck through the denser air is higher so it actually results in net loss as far as energy efficiency goes...

[allan5oh]

Yup that's exactly true, that's why in winter our engines are more powerful(probably ~50 hp) and spool up much quicker, yet get worse fuel mileage.

[Bandit102]

Personally, from what I've seen, air filter systems are massively oversized to begin with. I've never had my filter minder register anything. That goes to show how good the air filter system is on a Volvo.

Now if you're making 800+ hp, maybe that's a different story.

But to be honest the biggest advantage a classic truck has is the dual pipes. But if you have an aero with dual pipes, you're laughing. The exhaust system on a classic with dual pipes seems more restrictive then the exhaust system of an aero with dual pipes. The aero has much less bends to it. Of course, it depends on which model of classic.

My 525hp N-14 pulls 20 inches of vacuum with dual air cleaners and brand new filters. Your gage is broke.

[lwsii]

I agree with mudpuddle, check your air filter restriction gauge. It waill also make a difference with 15" cans on a Pete versus the narrower ones on aFreightliner or International (due to the width fat cans won't fit a fat truck) I won't argue with you but I've never seen over 8-10 " restriction on A Pete with Vortexes & if it pulled that, you needed to change the filters. I can't argue with you on how much is acceptable, obviously Intl/Frtl & their engine people are comfortable with their systems, the last new 9900 ix I made acouple trips for a friend I called him after less than a 100 miles convinced I had already diagnosed his 4.3 mpg avg (565,13/355 bullrack) problem- his filters were plugged up. I had never seen one pull 20" restriction before, he said they were suppose to be new but go ahead a change them. Well, I sure wasted his money, or would have but only because I saved the old filters, but point being I was wrong about that. So it is probably one of those unjustifiable things, they do make a difference but it may just be me & the gauge who notices it. At least a factory performance parameters.

[special k]

Sorry for the wrong info Bob, my experience was from the early 90's 9400.