Intake choices, new ideas...

[GeeXPee]

Did a lot of searching about various custom air intake setups for the GXPs, right now I'm mulling over a few different options in order of $$ investment and level of effort.

1. Increase the air inlet size + K&N panel filter.
2. Typical DIY heat shielded short ram-air cone intake type system
3. Both 1 & 2... minus the panel filter obviously
4. FWI
5. Twin intake possibility?

My question to you smart guys out there, would it be possible (and worthwhile) to incorporate a twin intake setup, i.e. two cone filters customized to feed either the current intake setup combined with maybe option 1 above or possibly a larger 4" custom setup as mentioned in another post? Has anyone tried this? Is there a point of dimishing returns? No matter which route I go the car will be getting a new tune to accomodate the larger air flow.

Does anyone have hard data that would support any one of these over the other? I know there isn't a lot of room to play in these cars but I'm sure if you get crafty the twin intake could work.

Am I insane or what?

[matt5112]

I think you're spending too much time worrying about an intake.

But I'm no engineer.

I do like the part where you mention a tune.

That with any of the options will be nice.

[GeeXPee]

You are probably right, being that I'm an excel junky I get wrapped around numbers too much sometimes. What I think would be cool is if we had a data forum for people to post real dyno results before and after a mod. I know not everyone does this or has the money for it but over time it could probably help people make good choices based on reasonably good data.

[blueguy]

I say #1 with a tune.

Seriously.

[SlowNA06]

Hm. Maybe get a nicer filter than K&N. I'd go with cheap short ram. If there's benefits to fenderwell, you might not notice. I happen to prefer the look of a 9"x4" filter, though, over airboxes. As for twin intake... probably too much work for no return.

[blueguy]

^^Followin' off that...

Back in the old days for cheap intakes...guys would gut the airbox and open up the front of it as well...worked pretty good from what I remember...and they ran a solid tube to the TB instead of the rubber corrugated junk.

[GeeXPee]

There has been discussion on this forum for a while about whether or not the stock setup was really that restrictive. K&N provided me some pretty hard data to back this up. The bottom line here is that the engine max CFM at 6000 RPM is 451 while the K&N panel filter can provide 592.4 CFM, the airbox restricts flow to 240 CFM. So the running while breathing through a straw analogy applies. Just thought I would pass this on.

"Thank you for your interest in K&N products. A stock engine usually has a volumetric efficiency in the high 70% to mid 80% range which would put the CFM of your motor at 451 CFM at 6000 RPM. That is the maximum amount of air that your engine car draw in so, even if your use a filter that can flow 800 CFM, your engine will still max out at 451 CFM and there won’t be any performance gain.



The CFM of a filter is based on its surface area and our 4 layer cotton filters flow around 6 CFM per square inch. Horsepower gains from the intake system are primarily from designing a more efficient and smoother intake tract. As you can see from our air flow test data, our panel filter can flow 592.4 CFM on its own, but in the stock, restrictive airbox, it can only flow 240 CFM.

http://www.knfilters.com/dynocharts/33-2334.pdf



By eliminating the airbox and using a smoother intake tube, the efficiency increases and the CFM capability of the system is greater than the requirements of the engine.



The only benefit of using a filter that flows more CFM than your motor needs is that it extends the service life because there is more surface area to draw air through before the filter becomes clogged. With that being said, a twin intake will provide no performance gain and will only be for aesthetic purposes. "

[Bio248]

im fairly sure once you start running a considerable amount of boost, those numbers are whack.

[matt5112]

Then gut the box and smooth tube?

[jcmonteman]

or rip the box out and try and sell it...much simpler

[blueguy]

or rip the box out and try and sell it...much simpler

No one wants a factory intake.

[GeeXPee]

Forced induction systems don't allow for greater flow rates in terms of CFM than what is set by the displacement of the engine. What t/c, s/c systems change is the amount of mass in lbs/min of the air coming into the engine, greater mass = more power so no it doesn't really go out the window.

I was providing the info for the 5.3 folks many of which haven't opted for the 5k cartuning turbo thats out there so I thought it may be of value to someone.

[jcmonteman]

honestly...i think someone might...a non-car person who wants to keep their car stock for resale purposes...

[GeeXPee]

Then gut the box and smooth tube?

Thinking about something along those lines.

[jcmonteman]

^^ well...if it goes horribly wrong, you know where you can get a replacement box (right here)

[matt5112]

Forced induction systems don't allow for greater flow rates in terms of CFM than what is set by the displacement of the engine. What t/c, s/c systems change is the amount of mass in lbs/min of the air coming into the engine, greater mass = more power so no it doesn't really go out the window.

I was providing the info for the 5.3 folks many of which haven't opted for the 5k cartuning turbo thats out there so I thought it may be of value to someone.

I don't follow.

The VE goes up, so does the CFM.

You could back up at look at it this way, more power requires more air to be pumped through the motor in the same period of time.

Thinking about something along those lines.

Let us know how it goes.

or rip the box out and try and sell it...much simpler

honestly...i think someone might...a non-car person who wants to keep their car stock for resale purposes...

^^ well...if it goes horribly wrong, you know where you can get a replacement box (right here)

:C

[GeeXPee]

All force induction system do is put more air in the same volume of space...CFM will go up (max out based on size) but the engine still can't exceed it's max CFM determined by the cu in size of the engine...that doesn't change. Volumetric efficiency doesn't go up just because the CFM is higher it's also because of the larger mass of air compacted into that same volume.

I'll take pics when I do my intake and let ppl know how it goes.

Thanks for the tips.

[matt5112]

Isnt CFM based on displacement and VE?

[T0pwater]

All force induction system do is put more air in the same volume of space...CFM will go up (max out based on size) but the engine still can't exceed it's max CFM determined by the cu in size of the engine...that doesn't change. Volumetric efficiency doesn't go up just because the CFM is higher it's also because of the larger mass of air compacted into that same volume.

I'll take pics when I do my intake and let ppl know how it goes.

Thanks for the tips.

What you are saying with regard to the CFM determined by the engine displacement is this: CFM = RPM * Displacement (cu. ft) / 2 ... divided by 2 because 2 rotations to fire all 6 cylinders. However, the density of the charge in a forced-induction system is much higher than the density of the air coming through the air filter. Yes, your volumetric flow rate through the intake ports is going to be the same in an N/A or forced induction car, however it will be much denser air (greater mass) in an S/C car. To raise the density of the air we MUST pull more volume of atmosphere into the engine. Thus, a S/C car does require more volumetric flow pre-supercharger, and there is no limit to that based on engine displacement. The volumetric flow will be determined by the size of your supercharger and its efficiency. It's called conservation of mass. There's no such thing as conservation of volume.

The info from K&N seems bogus and makes me never want to buy a filter from them. Saying a filter "can flow" a certain volume of air makes no sense. The volumetric flow in any fluid system depends on the pressure differential across the restriction. Upgrading to a less-restrictive filter (which, according to them, won't help you) will serve to decrease the pressure difference across your filter, thus raising your vacuum pressure and increasing the efficiency of the supercharger. When they say "our filter flows 6 CFM per square inch" what is that? With what vacuum pressure? With what intake tubing? Bogus.

EDIT: okay, after I went on my rant about K&N I looked into their data and by "it can flow X CFM", he means it can flow X CFM on a flowbench before creating a 1.5"H2O pressure drop. However, I still hope he knows forced induction can flow twice, if not more, the engine displacement through the filter due to the compression. So his "451 CFM max" number is ridiculously bogus as soon as you get into boost, as Bio said. Times 10 if you're running a small pulley.

[GeeXPee]

No to raise the density of the air you must increase the mass of the air while the volume remains constant...you are shoving a higher lb/min mass of air into the same volume in the engine. Pressurizing the air is what a FI system does...D=m/v...I really don't care what happens pre-supercharger. I'm talking about what takes place in the engine itself. But we can agree to disagree. It's all a moot point because I'm not really looking out for the FI guys anyways

I'm not trying to validate K&N either, I was looking to provide people info about the restrictiveness of the air boxes. I appreciated the fact that K&N was so forthcoming with their data whether or not anyone decides to use their systems I could care less. I trust that the CFM restriction on the stock intake system is accurate. I like to make decisions based on real data, I figured others might as well.

EDIT: Yeah I understand that in order for a S/C to provide a certain level of boost it must draw X amount of air in terms of CFM. Not really arguing that point. This is all skewed we are talking about the same thing just from a different angle.