'VETTE PHASE

I am really curious as to how the LS6 stacks up against the LS2. Can't wait. (my money is on the LS2)

Thanks for all your hard work and posting it up.

indy300

Very interesting thread. There are a lot of numbers being thrown around here For the engineering-challenged people (not me ) can you please summarize your findings as it relates to someone who wants to better thier air intake.

Such as:
1 can the NA engine handle more incoming air?
2 what is the most restrictive components on the system?
3 what solutions/upgrades can improve the entire air intake/engine system?

thanks.

RedHotZO6

To answer your questions:

1) The amount of air going into a NA engine is a function of cubic inch displacement, RPM, and Volumetric effeciency. A 346 cu inch engine running at 6000 RPM with 100% VE will need about 600 CFM of air. So you can spin it higher, increase the effeciency, or both to increase airflow. In most engines, VE maxes out near the torque peak then begins falling from there as RPM's go up.

2) In a stock C5 probably the air filter housing. The intake, heads, and exhaust are pretty good in stock form. A change to some form of cold air induction is a good mod from my testing. Once you start modding the car and adding headers, cam and heads, it is hard to say. Your best mods are probably CAI, Longtubes w/high flow cats and exhaust, and a cam w/ tuning. High flow heads will bring all these together.

3) My tests have shown you can get a 50% improvement in the system flow by doing the things listed. From there you can go to larger 90mm throttle bodies, larger mass air sensors, aftermarket air bridge, open air cleaners, etc. The list goes on and on. Some of these I will be testing later on.

Paul

RedHotZO6

Thanks to member mqqn (Andy), I have some test results for the Twin Filter Intake on a C5 Air Bridge, Ported MAF sensor and Stock LS1 Throttle Body.

Twin Filter Air Cleaner


Air Cleaner Assy w/ Stock Lid


Air Cleaner Assy w/ Modded Z06 Lid


Air Cleaner Assy w/ Twin Filter Setup

Note:
All Flows corrected to 10" H2O
Stock Throttle Body Flowed 547 CFM w/no Air Cleaner

Results:
Air Cleaner Assy w/ Stock Lid = 356 CFM

Air Cleaner Assy w/Modded Z06 Lid = 410 CFM

Air Cleaner Assy w/Twin Filter Setup = 410 CFM

With No TB and through a 3-1/8" opening, Air Cleaners Alone Flowed:

Stock Lower w/ Modded Z06 Lid = 625 CFM

Twin Filter Setup = 654 CFM

This clearly shows that for a mostly stock or mildly modded engine with 75mm TB and ported MAF sensor, a modded Z06 airbox is a good as anything out there as the restriction is in the MAF, Air Bridge, Coupler, and TB. For 90mm TB's, smooth Couplers and Large Z06 MAF's, a better Air Cleaner setup may be worth something.

More tests to come.

Paul

indy300

Thanks for the results and the summary!

2kbluestreak

The twin-cone filter design has been maligned by several over the years as not being able to produce the same power as a Vortex or Blackwing. It appears that your testing reveals its ability to flow a decent amount of air. On the other hand, the rub about this design was something like turbulent mixing of the two air flows messing up the MAF readings. Whatdayathink?

mfrejek

It's not like laminar flow is possible in the confines of the intake anyway, so I don't see what the "rub" is.

chaase

Formula is incorrect....
CFM requirement is about 620.7
http://raceabilene.com/kelly/hotrod/cfmcalc.html

2kbluestreak

Mechanical Engineer here. Each cylinder takes in air once every two revolutions; hence, you divide by 2.

mqqn

Hi RedHotZO6 -

Sweet!

I will get with you this week to arrange for shipping the halltech carbon fiber trap with the warhead filter - I will put the twin ram on the z until I get the trap back.

Very interesting results from your testing - I thank you for doing this for us all!

The twin-ram is a lot easier setup to install and get to the filters as opposd to the halltech which conceals the filter out in front of the frame-stay (crossmember).

I am now interested in the stock airbridge compared to the aftermarket variety - the halltech airbridge is noticeably taller in profile, but if (as your testing is pointing out) the MAF is the limiting factor in otherwise stock applications, then a greater flow capacity downstream from the MAF is irrelevant.

Interesting....

best regards -

mqqn

vettenuts

Actually, using only the cubic inches to calculate the air requirements is not correct either, velocity and momentum play a big role especially at higher RPM's. Otherwise, cam an head design would be fairly straight forward.

madmatt9471

IMO! Wouldn't it be okay then to go with a larger MAF housing if one is to purchase and use a new air bridge? This is what I did and certainly could feel a difference in the crispness of the throttle!

Any analysis please! and correct me if I'm wrong here!

Thanks,Matt

RedHotZO6

I don't know what gains you would see from the larger MAF and Air Bridge. A flowtest of the complete system from air cleaner to TB would tell you.

Paul

yellow94coupe

Fantastic thread! This kind of stuff reminds me why I got in to mechanical engineering in the first place. I'm having to dust out some cobwebs since I haven't thought about fluid mechanics much in 6 or 7 years.

I'd be curious to see a plot of flow rates vs pressure differentials. What is a typical manifold pressure at WOT? Is 10 inH20 realistic?

There are a bunch of airflow horsepower calculators out there. I wonder how the differences in flow you are measuring stack up to the power people are claiming to get.

RB Racing

I just drilled some holes in my stock lid on my 2000 and I couldn't believe how small the stock ones were. I drilled 4 holes roughly 2 1/4" which is about 200% bigger than what was there. After taking it for a drive it seems to have a bit more response off the bottom.
Paul it would be nice to take a stock lid and drill holes till your at the flow rate of the modified Z06 lid to see how many holes are actually required.
Then people would know how may holes are required to get the most out of their stock lid with the minimum amount of holes.
Thanks for the info.
Marc

mqqn

Hi Paul -

I got the twin ram back last night - Thanks!

I will install it on my Z and send the Halltech to you if that's ok with you.

best regards -

mqqn

Beer99C5@FastbirdPerf.com

TTT

RedHot, have you considered contacting Corvettes of Houston and tell them what your doing? They may be interested in providing you various CAI combo's for a little PR and for there product knowledge also, after all they are a forum Sponsor.

Billdog350

GREAT THREAD!! I just finished reading the whole thing and I didn't see any answers for the STOCK AIRBRIDGE CFM. I recently had a new cam and heads installed and fell short when it came to the dyno peak hp (though torque was awesome). The graph showed a restriction in the system somewhere near peak hp, probably intake or exhaust flow. Wondering if my stock airbridge could be the cause for an issue around ~410 rwhp & 5800rpm. Can someone test one? Please?

Vetteoholic

Great thread Paul! Very Interesting Indeed Thanks alot for sharing with all of us ~ thats great.

KEV21

The most visually restrictive thing I see with a stock 02 air box (top removed), is the way the air is squished horizontally before the MAF sensor. I know that it is a little wider, but it seems to me that this would be a major restriction, and looks to be so after seeing the results with the air box "lower" and MAF removed.

I would like to see a flow comparison between the following 2 setups:

1-stock system, with no air box lid, and no air cleaner.

2-stock system, with nothing forward of the MAF sensor.

If this is a substantial difference, we are wasting time modifying the stock air box at all.

Great post!