Importance of intake tract design.

How important is or to what degree does the intake tract design effect the output of a high HP(500 +) NA motor. For example with the LT1 unless you go with a custom set up or a Trans Am ram air set up your stuck with the 90 degree bend. Is this design a restriction? If not than why did GM decide to go with the straight ahead design of the LS1? Just got to thinking after reading some of the threads in LT1 tech that were talking about the supporting components needed to realize a high cfm value actually seen by the heads. How can a cooky design CAI like a Moroso or K&N flow enough air when they are such odd shapes?

Intake design is very important. The diameter, length, contour
and all other aspects are critical to squeezing power out of the motor.

First off, I would imagine getting cold air into the motor is priority.
Having an intake design which allows cold air with the shortest
path through a heat source is a key factor.

Bends aren't so bad as long as they are smooth. A direct shot
is best, but that isn't always possible.

The output power of the motor really isn't an issue; this would
apply to any motor.

Engines of extreme output are probably banking on timed pulses
which are tuned via runner lengths and volumes according to
engine operating ranges and valve timing.

The shape of the tube is important, but from what I've read, the
cross sectional area is one of the major criteria for flow. The FIPK
kits from K&N are flat and wide as opposed to circular.

The area and volume of flow is equal or greater than that of a stock
LT1 intake.

A shot in the dark tells me the deliberate shape will also straighten
air flow, and/or accelerate air flow as it passes into a narrow
path...sort of like a venturi?

The MAF screens are also said to remove eddy currents from the
intake tract before it enters the plenum.

This 'myth' has been tossed around for a while, but nobody has
stepped up with solid evidence. I tend to believe that a turbulent
fluid passing through the screen will straighten out, just as it would
flowing through an air filter.

The K&N CAI will flow in excess of 1300cfm.The cork in this system is the small filter that comes with it,it flows 700cfm.AFAIK 1300 is the biggest TB you can buy so a K&N should do fine.
The cross section area and length do quite a bit toward shaping the air and get it headed to the piston.The length will differ from engine to engine depending on your tuning pressures.It isn't one size fits all.The plentum volume figures into the mix also.You have to have enough,but as with runner length you have to fit it under the hood.

Some of the figures I have seen for plentum volume are BIG CID

Good info guys.

What about an intake design like this...(found this on a search).

http://community.webshots.com/photo/118796447/118796895NXIcpX

http://community.webshots.com/photo/118796447/118797672jBxXUn

http://community.webshots.com/photo/118796447/120934904drNCHV

A bit GETTO,don't you think?

Without a doubt:D, functionally though?

Probably not any more so than a neat CAI.If you are trying to make 500+ to the tire you will look for air intake help anywhere,but this wouldn't be MY first choice.
I have done a lot of research on this,and into making my own.(going for 700FWHP on pump gas) For the time being I will use the K&N and their 1400cfm filter mounted in the fender.It will fit,but I have no front bumper and modified plastic in that area(I have a plastic welder)I also reshaped the end of the K&N tube to move it to the rear of the hole to allow for the 14"filter.Looks pretty good but I would advise taking the front clip off to do it.They make a 12"cone filter also that flows1200cfm.But don't know if it will work with the bumper in.

This is an interesting discussion being that I personally will have some freedom in my choice of intake design once I get SStrokerAce's intake.

1racerdude your talking about some big filter's here. Any idea on what the two puny SLP CAI filters flow? Thats what Im running now, that's may have to change...

http://www.slponline.com/view_product.asp?PARTNUMBER=21014&SHOWIMAGE=On&SHOWEMAIL=Off

Are these the standard K&N cone filter that is 6-7" long and has a 4" opening?If it is they flow 700cfm.Cain't tell the size in the picture.

Ain't that a nice intake Bret's got.Will be one hell of a set up to make all the HP a body could stand.I got a sneak prevew when it was being built.I may have wrung it out for him if I hadn't already had Wilson do one for me.

Oh that intake is a beauty. I got a sneak preview from start to finish also, looks so nice I dont want to get it dirty.:D

I think the length's are maybe 5" or so. The openings for each filter are small, maybe 2" in diameter each. Ill check for sure tommorow. Thinking quickly they are realtively close to a campbells soup can in size.

Well, the intake system does it's thing from the filter to the piston so it sounds like those filters are a cork in the system.I thought about building a CIA like that with bigger tubing and 2 of the 700cfm(6-7") filters in the fender of this '94 but it seemed like less work with the 1x14" until I got to doing it(lazy)That plastic is not easy to make it do what you want.

Originally posted by 1racerdude
Are these the standard K&N cone filter that is 6-7" long and has a 4" opening?If it is they flow 700cfm.Cain't tell the size in the picture.

If this is the filter(k&n 7inch) I am running with my solid intake and vortech is it a restriction since the blower flows 1000cfm? Or does it really matter with forced induction.

Slightly off the topic... I been reading on maxima.org about how ram air is worthless, more specifically, its just another CAI. I believe different, If TA's were equal with the same hardware would one with a Ram Air hood be faster, if so, what would have to be done to make it faster, i.e, sealed box, different lid? I dont think that the different exahust was worth all 20hp.

Yes you have a restriction.If your blower is trying to suck 1000cfm and the filter only flows 700cfm then the blower is not at full potential.It is a little different with a blower but any restriction will limit it's output.
IMO ram air is effective,but not through the hood.It should come from the outer quarter of the lower front clip were air pressure is at speed is the greatest,and be ducted to the TB.Parking light hole??

To add further to the RAM Air discussion:

Ram Air is more functional as a cold air intake and efficient beacuse
of the straighter path from the outside world to the engine.

I've seen dyno curves of Grand Prix (GT and GTP) with and without
the Ram Air GTX hood. There was a slight variance of a couple of
horsepower, but nobody could attribute that small increase to the
hood design.

On top of that, Ram Air on a dyno is sort of pointless because the
car isn't moving.

The more interesting facts came with track times and speeds between
these cars as well as a graph of manifold pressure as the car
accelerated down the track.

I don't recall exact times/speeds/or MAP, but I know it wasn't
in excess of a couple MPH and a tenth averaged out between
the tests.

You'll find it interesting to know that Ram Air hoods don't work
as well as you might think until the car is moving at excessive
speeds.

The engine is sucking up quite a bit of air to begin with. In order
to pressurize the intake plenum with enough reserve air, the car
must be moving at high speeds. Some numbers I've heard are
100+ MPH.

Not very effective for street use, but will grab some power on the
track.

Originally posted by 1racerdude
The K&N CAI will flow in excess of 1300cfm.The cork in this system is the small filter that comes with it,it flows 700cfm.

Yes 700cfm... but at what pressure drop?

-Mindgame

Originally posted by Mindgame
Yes 700cfm... but at what pressure drop?

-Mindgame

The best my memory can recall it was 10"water.

Neat idea, I'd replace the corugated hose with a straight bellow. It takes twice the diameter of corrugated hose to flow the same as non-corrugated.

Airflow doesn't like bends either, since air has mass with develops momentum. It takes a large radius bend and a larger diameter to flow the same as a straight pipe. Minimize the cruves and cross sectional changes and you're on the right path.

Hope this helps,
-Christian

Look at a K&H CAI the next time you get a chance and look at the bends,you'll be impressed at how they did it.It does flow in excess of 1300 CFM(just the tubing).

Originally posted by 1racerdude
The best my memory can recall it was 10"water.

10" water would put the 1.5" flow at ~270 cfm. No bueno.

I've seen tests of the round K&N filters, in particular the 12 x 3.5-incher, flow ~875 cfm at 1.5" H20. Subtract 1/2" from that overall height to compensate for edge flow losses and you get ~113 in^2 of effective flow area. That would suggest that the K&N filter element flows about 7.7 cfm per square inch of filter area.

The LT1 filter is 6" (top) x 4.5" (bottom) x 7" long. Subtracing 1/2" from the length again, I get an effective filter area of ~108 in^2. That multiplied by 7.7 cfm gives us ~831cfm of flow. Of course we haven't accounted for frictional losses along the pipe so... was the element flowed with the pipe attached and what was the actual depression used?

I'm guessing, based on these examples, that the depression was 1.5" H20 but we really need to know for sure if we're going to base calcs on 700cfm.

Considering the formula for air capacity of an engine of given size...

CFM = rpm x displacement / 3456

A 383 ci engine turning 7000rpm would ingest 776cfm at 100% volumetric efficiency. So I'm wondering how much the K&N cone filter is hurting performance.

I may make a backup pass without the filter next time I'm at the track to see what happens. Anyone tried this??

-Mindgame

I have mounted the K&N with the same end dimensions except 12"long along with their intake tube.That filter flows 1200CFM.I figured if your TB flows 1300 ya need an intake tract to flow with it.
My program says that this engine ingests almost 900CFM@7000???That not what the formulas I have used for years says--but??

Yes, sort of (a 'lil off the question even)...

Using a 14" diameter x 3" high K&N ring filter, I made a dyno pass
without the filter installed to test for restriction.

The dyno showed no increase in horsepower/torque so we concluded
that the filter was sufficient for my engine.

355 CID, spinning to 5800 RPM making 270.2 HP at the wheel.

This is an L98 engine breathing through a 700 CFM Holley.

Based on the "area of flow" for the ring filter, it was able to handle ~ 596 CFM (if 100% V.E.)

I have also made passes down the 1/4 with and without the
filter: +/- 1 tenth was inconclusive with 3 attempts.

1Racerdude, you mentioned the curvature of the K&N FIPK being interesting. I've been running the Arizona Speed and Marine cold air with a 9" k&N filter IIRC. I decided to pic up the Moroso/ Lingenfelter cold air to do some airflow comparisons. Here are some pics of the moroso if anyone is interested:

http://www.carprogrammer.com/Z28/MorosoIntake/

I'll datalog 3 WOT 3rd gear runs on each intake and compare the MAF readings, I'll share the results on this thread if no one minds.

-Christian

That would be great. I don't have the access to things here for testing as I had in CAL. and a test like that would be enlightening for everybody.

Thanks man.

MG,
I will see if I can find the paperwork on that test.I may still have it,it's been a few years.
Old fart's and their memory sometimes don't get it done.

[QUOTE]Originally posted by Mindgame
[B]10" water would put the 1.5" flow at ~270 cfm. No bueno.

I've seen tests of the round K&N filters, in particular the 12 x 3.5-incher, flow ~875 cfm at 1.5" H20. Subtract 1/2" from that overall height to compensate for edge flow losses and you get ~113 in^2 of effective flow area. That would suggest that the K&N filter element flows about 7.7 cfm per square inch of filter area.

The LT1 filter is 6" (top) x 4.5" (bottom) x 7" long. Subtracing 1/2" from the length again, I get an effective filter area of ~108 in^2. That multiplied by 7.7 cfm gives us ~831cfm of flow. Of course we haven't accounted for frictional losses along the pipe so... was the element flowed with the pipe attached and what was the actual depression used?

I'm guessing, based on these examples, that the depression was 1.5" H20 but we really need to know for sure if we're going to base calcs on 700cfm.

Considering the formula for air capacity of an engine of given size...

CFM = rpm x displacement / 3456

A 383 ci engine turning 7000rpm would ingest 776cfm at 100% volumetric efficiency. So I'm wondering how much the K&N cone filter is hurting performance.

I may make a backup pass without the filter next time I'm at the track to see what happens. Anyone tried this??



Mindgame,

-You are correct-- the number is 1.5" of water.

Thanks for the confirmation Larry.

Just hate to assume anything. :)

-Mindgame

By your figures the "standard" 7" K&N does not flow enough for these 650-700HP engines? Or is it borderline,IYO?

Now that I'm actually thinking about it (never have really given it much thought til now, thanks LR) I'd have to say it may be "borderline". I plan on doing a bit of experimenting when time allows to find out... cause I'm running that same 7" filter on my setup. :)

-Mindgame

OK

Just some info I have from my last dyno runs with the SLP intake and the two tiny filters. Every since this last Dyno I have been planning on doing some thing different for the filters but I need more testing and the test car is down.

Test Engine. Stock LT1 350CI. slightly modified intake, heads ported to 280+@.600,58MM Billet TB, MBA MAF Ends with stock electronics(Tune calibrated for this), SLP CAI with filters.

This Engine made 395 Corrected 409 actual at the rear wheels through an Automatic and a 12 bolt.


Once above 4,800 RPM the Map started dropping from 101Kpa. It hit a low of 89Kpa along the way and hit 380+ GPS on the MAF reading. THE MAP Drop was not erratic spikes but a fairly smooth drop. Peak HP was at 6,900.

I also have some files on our stock LT1. it only took 250ish GPS of air and the Moroso was fine with just little blipps in the MAP.


Just what I have tested thought I would toss it out there for you to add to your tests.

250ish is no were near 700FWHP.Thats where I need to go.Thanks for the input.

I am so sorry. Try this one on for a taste.

http://groups.msn.com/WashingtonFBodys/twofast4lv.msnw?action=ShowPhoto&PhotoID=520

Just my little under construction Engine ;)

Kinda remind's me of mine.Intakes are different,Wilson did mine,but if its built for the engine who cares who built it.
Really nice.When ya gonna make smoke?

Just some info I have from my last dyno runs with the SLP intake and the two tiny filters. Every since this last Dyno I have been planning on doing some thing different for the filters but I need more testing and the test car is down.

Test Engine. Stock LT1 350CI. slightly modified intake, heads ported to 280+@.600,58MM Billet TB, MBA MAF Ends with stock electronics(Tune calibrated for this), SLP CAI with filters.

This Engine made 395 Corrected 409 actual at the rear wheels through an Automatic and a 12 bolt.


Once above 4,800 RPM the Map started dropping from 101Kpa. It hit a low of 89Kpa along the way and hit 380+ GPS on the MAF reading. THE MAP Drop was not erratic spikes but a fairly smooth drop. Peak HP was at 6,900.

I also have some files on our stock LT1. it only took 250ish GPS of air and the Moroso was fine with just little blipps in the MAP.


Just what I have tested thought I would toss it out there for you to add to your tests.

OneFlyn95z28 sorry I maybe missunderstanding but its late and Im dead tired. So based on your testing is the SLP a restriction as compared to the mentioned moroso based on the drop in Kpa?

Ive thought about doing a CAI swap also. Something along the lines of a 4" elbow from here (http://www.jagsthatrun.com/Pages/Parts_AirClean_Ducting.html) along with a couple pieces of rubber tubing/fernco from the local plumbing store. My only concern is the air flow transitioning from a smooth 4" elbow entering the engine bay to a squished irractic "ovular" shape as its passes through the tiny space between the radiator and the ABS block. Should 5" tubing maybe be used here to account? Im hoping this along with a 7" or larger K&N filter should outflow the dual 2.5" SLP unit.

Any thoughts?

Anyone?

1racerdude?
OneFlyn95z28?

Highly considering switching over to a Corvette cold air induction system, has anyone documented dyno gains from before after. Since the front fascia of my Callaway has a huge front opening, what better way to capitalize on the design. Do you have to change hoods since the induction goes over the radiator support? Any feeback would be nice. Take care

Johnny

There was a guy who did the same thing with the corvette cai. Take a look at some of the pics Jkren posted earlier in the thread. This is that guys CAI.

There was a guy who did the same thing with the corvette cai. Take a look at some of the pics Jkren posted earlier in the thread. This is that guys CAI.

Yeah I saw the pics but I didn't get the user board name. Considering purchasing an aftermarket C5 CAI but skeptical on whether if the hood will close. (I think not) Can anyone help me?

Johnny