Custom built Venturi intake, using garbage scraps

AA wrote:

Good discussion, from two different sides of mod logic. One school says that numbers rule. If you can't verify quantitatively that changing the system results in an actual gain in power or track times, the numbers people say it isn't worth doing. The other group says experimentation and DIY mods can instill a sense of pride and personal accomplishment, regardless of the actual results. If it feels right to the owner, why do numbers even matter?

Both sides offer real benefits to different types of folks. As Einstein would profess, it's completely relative. For those guys who've been to the track, and have seen first-hand what makes a car faster, it's a no-brainer what mods you do and don't do to a car. For the other guys looking from a different angle, why not try things for the experience, even if the numbers guys snicker? As most everyone knows, true innovation often results from experimentation against traditional logic. Who knows? Trying something opposite the norm could result in spectacular discovery!

One problem with the numbers type of approach is that verification requires a visit to the track, or metering with expensive equipment such as a dyno. This often costs as much or more than the mods themselves, and not everyone has the time or means for it, so most people looking for proven gains will pay their money to a professional with a good reputation for a claimed result. Most of the time you get what you pay for, but how do you really know? Because you're detached from the mod process, you're putting 100% trust in the one doing the work. My advice: unless you know from reputation or experience that your guy knows his stuff, ask for some kind of proof to verify the numbers are legit.

In contrast, the DIY experimenter types are basically using trial & error methods to offset the cost of professional equipment or services. Using what fundamental knowledge they have (or think they have), these folks prefer to try new things, tinker with settings, and experience results, which are usually felt rather than recorded. The obvious problem here is that time can be wasted, with no guarantee on return. In many cases, you can end up with a car that's less reliable, slower even, than what came from the factory. As Larry70GS has pointed out, the engineers at GM knew a thing or two about this sort of stuff. If we assume they are wrong about everything, we are probably fooling ourselves.

My opinion is this: you need to pull from both sides. Feel free to experiment, but be smart - understand that numbers do matter, and that your perception of "improved response" is kind of like saying your favorite color is blue. Try to find a more objective way to verify results without spending much money, then your findings will become more credible. Member opinions on our board can vary somewhat, but some things we all agree on, and this is FREE info! Consider the opinions of those like Larry70GS, who have years of experience tuning cars and running at the track. Don't agree with what he has to say? Try proving him wrong then. Take some base-line measurements and then try implementing your mods under same situations, and compare results. Be careful to do your testing in a scientific manner, and repeat more than once to show consistency. Because you're involved in the testing, whatever results you find, at least you'll learn something. If the results are not what you wanted, NO BIG DEAL. The most intelligent thinkers in history will say they learned the most from occasional failures.

Regarding your progress so far, it is intriguing work. I know very little about the behavior of air intakes on NA engines, and would like to know more. Admittedly, I'm a numbers guy, but I do appreciate experimentation. Would like to see some numbers that prove your intake design really functions in practice as it does in theory. I want to know if that copper pipe actually does what you think it does (letting the air pressure stabilize). Right now, we have no evidence it works in your particular case. No saying it doesn't, because I have no proof that it doesn't. Right now, it's just a copper pipe that might do as intended.

Last thought: you mentioned your intent to drop the t-stat to a 180º unit. Based on my own experience, and what I believe to be excepted wisdom from those that know, you won't see any performance benefit from doing this, unless you can find a way to advance spark timing to a point where engine starts to knock. All engines are designed to operate most efficiently within a certain temperature range; in our case, that's about 190-210ºF. For supercharged applications, we are constantly flirting with knock under boost, and since forced induction is a definite power adder, it makes sense to compromise thermal operating efficiency a little but in order to improve the blower's ability to add power, ei. fighting spark knock to allow more boost. But if you're not fighting knock, it's not helping, and probably hurting performance.

Keep us updated on your progress. Feel free to start new threads or add to old ones when you experiment with different areas of the engine or car.

All valid points. I was thinking higher engine temps = higher intake temps too, but I guess I'm less affected by that now with a cold air intake and a bit of insulation on the pipe. If I go supercharged im definitely getting a 180*

And like I said earlier, if I did have a blower, there would be no need to mess with the intake other than coldest possible air and the least amount of restriction. I'm a numbers guy too, but I can definitely feel torque gains, I can't say for sure if the car is actually faster because my speedometer is broken. It could be saying 60 while I do 90. Also, mid-top end seem a bit more responsive. The engine sound seems a bit more refined overall now as well. It sounds much more healthy at lower cruising speeds, and one big note on engine health, I was having problems starting the engine for a while, turning over and not starting, which cleaning my throttle body fixed, but since I put the venturi setup as a cold air setup, the engine has never started so quickly, like it was new. it used to always take a bit longer than it should, despite the engine running fine. I can also hear the venturi at work. There's a little whine noise of rushing air :p

Something to keep in mind, I did admit earlier that at first the venturi setup was slower with weird effects, but still seemed like power was added somewhere, then I realized it wasn't them MAF, but the fact I was feeding the engine hot air, which was probably affecting it badly with the venturi setup. I had no idea why backwards, without a cold air setup, it gained torque, and on the right way, I lost torque, when a venturi setup is supposed to lose top end. The cold air intake setup seemed to solve everything completely, and I feel like it helped overall everywhere, especially with torque, which I really need because of the horrendously long gearing. I wouldn't be saying my setup helped if it didn't but I can't definitively prove it either.

If, and a huge if, I did set up a venturi intake on a supercharged car, gaining knowledge of what people have recently told me based on this setup, I would be meticulously perfecting air flow so that the turbulence wasn't too high going into the MAF, I'd test it on an N/A car for vacuum pressure, I'd probably do a wind tunnel type test or some kind of trest where I can visually see the air flow, I'd make sure there are no sharp bends in the plumbing, which Iv'e already done in my setup, make sure both filter and plumbing are very insulated from engine bay, maybe hook the venturi piece up to some kind of water hose, which would also speak for durability under a lot of pressure, but I don't see myself doing all that for minimal gains under a forced induction setup. This was an intake made out of broken crap laying around out of boredom while I was cleaning one day :p

My ideal intake setup, blown, is a true ram air intake with a housing around the filter to force all the air in, not looking tacky, but I don't know about the aerodynamics to permit whether or not that would gain over a fenderwell intake just yet :3

Im a numbers guy too, but I cant exactly just hookup to a Dyno whenever I want, and I may try the vacuum test.


Also, I do live out in the middle of nowhere on some really windy backroads, so I can definitely say my car has improved in track performance. I never had enough power before to lose any kind of control, and I found myself almost slipping a little bit with the new intake setup, not used to the power gain yet. obviously not numbers verification, but I think it means at least something.


Honestly, There's not much point in spending huge amounts of effort in testing whether or not there are gains, because this is only a temporary set up. I plan on getting an OBDII bluetooth adapter soon, which can record 0-60 and 1/4 times, I'd be happy to compare them to stock when I get it, and see if it has improved though

See, you've already learned something about intake temps vs. engine coolant temps. Two entirely different things. There's also one more: exhaust gas temp (EGT). Some advanced tuners consider EGT to be one of the most informative parameters.

To clarify each:

Intake Air Temp (AIT) - cooler air means more air into the engine, because it's more dense. This means more fuel can be added, keeping the AF ratio = more power/torque. Cooler air also tells the AIT sensor to command maximum ignition timing advance, also = more power/torque in warmer ambient temperature. AIT does not have much effect, if any, on ECT.

Engine Coolant Temp (ECT) - lower temp is beneficial for fighting spark knock, and not much else. Lower ECT effects EGT a little bit, but it doesn't much effect AIT, because intake air tends to pass the MAF sensor before getting warmed. ECT's effect on EGT can help tame spark knock, which enables more advanced timing (if tuned), which = more power/torque.

Exhaust Gas Temp (EGT) - is the actual temp of air/fuel after combustion, as it passes through the exhaust valves. EGT is determined mainly by A/F mix, and to a lesser extent by ECT and probably AIT by a very small amount. Cooler range spark plugs have a slight impact on EGT, cooling the cylinder combustion and decreasing spark knock.

For natural aspirated engines, a lower AIT is desired, but ECT and EGT should remain higher, in the range the factory intended for best efficiency.

Quote :

If, and a huge if, I did set up a venturi intake on a supercharged car, gaining knowledge of what people have recently told me based on this setup, I would be meticulously perfecting air flow so that the turbulence wasn't too high going into the MAF, I'd test it on an N/A car for vacuum pressure, I'd probably do a wind tunnel type test or some kind of trest where I can visually see the air flow,

Since you're planning to get OBDII capability, why not use it for scanning? You can monitor MAF and know exactly how much air is moving through the intake, and the IAT. You can also monitor boost (MAP) when you get your supercharger going.

Re: the Weapon R intake idea, I'm not sure I'm sold on their use of the Venturi effect. In their words:

"The concept is to create two different air velocity profiles, one traveling at higher speeds than the other. This technology increases air volume and speed to the engine, which naturally feeds the engine 3x more air than the conventional air intake system. The intake pipe is bent out of high quality 6061 Aluminum on our Automated CNC mandrel bender. Polished to a high show quality finish. The SW1 Air filter features a tuned velocity stack to increase velocity and decrease turbulence. 1 Million Mile Limited Warranty Open pore high density re-usable foam Over 250 applications for Car's / Trucks / SUV's"

Sounds good, but reminds me a lot of this:

"Creates a swirling air motion, allowing the air to move faster and more efficiently by whirling air around corners and bends. The result is improved airflow into your cars truck or SUV's engine. Causes better fuel atomization, resulting in an increase of gas mileage anywhere from 7-24%. These figures are confirmed by road testing performed at an emission lab licensed by the EPA. Dyno testing shows 4-13 added horsepower as well!"

The latter description is for the Tornado/Turbinator intake device, imo one of the most fraudulent products ever to be foisted upon automobile owners. I wouldn't call the Weapon R technology fraudulent (yet), but it does echo the idea of the self-perpetual machine that somehow magically supplies more air to your engine than would be thought possible. A 3X improvement is quite a claim.

So, are there any numbers to support Weapon R's technology? I found this link from 2004:
http://www.scionlife.com/forums/showthread.php?t=1549

Basically, they took a 100HP Scion xB with 1.5L I-4 on the dyno. The results:

Stock intake, baseline run: 94.1 HP / 98.3 LB-FT torque (best out of 3 runs)
Swapped Injen intake run: 96.3 HP / 100.2 LB-FT torque (best run)
Swapped Weapon R w/Venturi: ~95 HP / ~99 LB-FT torque (numbers were "between stock and Injen" runs)
Weapon R w/Venturi removed: ~96 HP / ~100 LB-FT torque (numbers "almost equal to Injen" run)
Weapon R w/o Venuri & 3" cut from length: ~97 HP / 99.6 LB-FT torque (evidence of improved flow)

What I got from the test: Venturi technology appears to improve HP/TQ, until the Venturi is removed and the intake is retested. It's then clear that any gains were from the increased diameter of the intake, not the Venturi effect. In fact, it's pretty clear that the Venturi decreased performance slightly.

More importantly, the best performance gain was only 3 HP, and the Venturi-equipped version gained only 1 HP (actually a 1HP loss, considering).

According to Leo, of Weapon R:

"Agree that the 1hp difference in this car will not make much of a difference."

"I still feel that the velocity tube inside the pipe will make more power, it's just figuring the size and length."

"Overall tube length is going to effect the intake's overall performance."

I agree with each of these statements, but it's still not a good case for the Venturi technology. Remember, the claim is a 3X increase in air flow.

I found a couple other hits for dyno tests with the Weapon R. One claimed a 3 HP gain for a Toyota Yaris. A responder asked a very interesting question: why does the longer length TRD intake offer a 5HP gain? Makes me wonder what the gain would be, if the Venturi part were removed and the same intake were retested?

If Weapon R's own test results show a loss, I'm not sure how sound the Venturi idea is to begin with. Are there any other intake manufacturers pursuing the concept?

Luckily, my design differs slightly from Weapon-R, because the pipe to let pressure even out has a much bigger inner diameter on mine, and the intake is an actual cold air intake on top of it, and the venturi piece is right next to the engine itself (not sure if that part differs)

but, there was a huge difference in the effectiveness of my intake from regular short ram air intake, to the cold air intake setup I just did. correct me if I'm wrong, but Weapon R is just a hot air short ram intake that they claim is as good as a cold air intake? like you said earler, colder air is more dense, and lets more o2 molecules to be burned into the engine, which seems more useful to me than a little shove from a venturi device regardless, and I'm thinking the venturi piece is a lot less effective without colder air.

also, one more thing.

Quote :

The simplest apparatus, as shown in the photograph and diagram, is a tubular setup known as a Venturi tube or simply a venturi. Fluid flows through a length of pipe of varying diameter. To avoid undue drag, a Venturi tube typically has an entry cone of 30 degrees and an exit cone of 5 degrees. To account for the assumption of an inviscid fluid a coefficient of discharge is often introduced, which generally has a value of 0.98.

I'm not convinced the air entry is proper, this looks like it's just hooked up to a smaller tube to me, but I can't exactly take one apart and look at it




I used a port tube out of a broken subwoofer as my venturi pipe because of the smoothness of the ends, and how it fit perfectly to my pipe walls, and has a somewhat good angle for smooth entry and exit of airflow. I did not mindlessly put together a pipe with constrictions and call it a Weapon-R :o


As you can see, my piece here doesn't look much like a weapon-R. I didn't design it after the weapon-R, because most people on here were saying bad things about it.








I'm pretty sure the formula for a perfect venturi wouldn't be close to checking out on mine, but it looks a lot more like the real thing than the Weapon-R imo.

and I'm convinced a venturi really does increase air flow because of how blow torches work, and various other venturi applications. I wouldn't have even started this project if I didn't start messing with little torches from boredom one day, turbing it from lighter, to torch, wondering how the air flow increased so dramatically, then realized I could apply this effect to my intake


but then again, I'm not claiming any scientific credibility, or really any performance credibility other than what I noticed from anecdotal experience in my project either

also, I'm not claiming to fully understand how this thing works

I understand the concept of a Venturi. Air speed increases through a tapered narrow tube, no doubt there. Question is, does the increased velocity mean there is actually any more air volume/mass flowing through as a result?

Please keep experimenting, and don't mind my critiques. I'm actually hoping there is some way this idea could work.

AA wrote:

I understand the concept of a Venturi. Air speed increases through a tapered narrow tube, no doubt there. Question is, does the increased velocity mean there is actually any more air volume/mass flowing through as a result?

Please keep experimenting, and don't mind my critiques. I'm actually hoping there is some way this idea could work.

No, mass flow rate remains constant. Velocity increases to make up for the lowered cross sectional area.

So air flow in = air flow out, minus the restriction of the inner tube. Unless I'm missing something, it seems no gains are possible by using a Venturi in the intake.

Faster moving air has lower pressure. That's what makes a carburetor work, and that is what creates lift in aviation. I still see no advantage to a venturi on the intake.

well, I can say for sure it feels like I have more torque. but due to the fact my gauge cluster needs to be rebuilt, I can't definitively prove speed gains what so ever.

Also, one thing is, even if I'm not getting MORE air, at the very least, it's probably going faster, and is more insulated, and is probably at least colder than if the venturi was not there. I guess this will have to wait a while until my wire harness gets fixed/I get an obd reader to post a good 0-60 or quarter mile time


what does a stock L36 riv get for 1/4 time and 0-60? I have no idea on that.

c0reyl wrote:

what does a stock L36 riv get for 1/4 time and 0-60? I have no idea on that.

From the Auto channel.com http://www.theautochannel.com/vehicles/new/reviews/1997/gap9649.html

1997 BUICK RIVIERA
By Matt/Bob Hagin
buick

SEE ALSO: Buick Buyer's Guide

SPECIFICATIONS

Manufacturer's Suggested Retail Price $ 32,910
Price As Tested $ 34,855
Engine Type 3.8 Liter V6 w/SFI*
Engine Size 231cid/3791 cc
Horsepower 205 @ 5200 RPM
Torque (lb-ft) 230 @ 4000 RPM
Wheelbase/Width/Length 113.8"/75"/207.2"
Transmission Four-speed automatic
Curb Weight 3747 pounds
Fuel Capacity 20 gallons
Tires (F/R) P225/60R16
Brakes (F/R) Disc (ABS)/disc (ABS)
Drive Train Front-engine/front-wheel-drive
Vehicle Type Five-passenger/two-door
Domestic Content N/A percent
Coefficient of Drag (Cd.) N/A

PERFORMANCE

EPA Economy, miles per gallon
city/highway/average 18/27/21
0-60 MPH 8.5 seconds
1/4 Mile (E.T.) 16.9 seconds @ 87.2 mph
Max towing capacity 1000lbs
* Sequential fuel injection


Keep in mind that test results will vary from one source to another. E.T. depends heavily on launching the car with no wheel spin, and that's a lot harder than it sounds. Getting the car to launch cleanly and get to that first 60' means the most, 0-60 or 1/4 mile. Sticky tires help immensely here, so Drag Radials run at a proper pressure and warmed up with a burnout, are going to give you that clean launch. That will also put maximum strain on the drive train. Since the transmissions in these cars are just about adequate, racing will likely hasten their demise if you get a clean leave, and repeat that often enough. Experimenting with different launch RPM, and converter loading can also show gains.

Even if your speedo was working, it would be very difficult for you to document any gains from your venturi intake. If you are happy, and pleased. That's great.

Wait, the supercharger only makes the car have like, a half second faster 0-60? :O


And yeah, I know that part, by thew way, I have never had enough power to get anywhere near breaking loose on my wheels. there's no way traction loss can be a factor. and OBD II adapters for android can more accurately document 0-60 times and 1/4 times than me looking at the gauge.

Looks like I aim to beat 8.5 secs and around 17 second 1/4 time then


btw how much does the entire ABS system weigh? or is it just some sensors that allow the breaks to be applied in a way that helps it not lock up? I ask this because I remember seeing "ABS delete" on someone's performance mods, and my ABS doesn't work anymore anyway

c0reyl wrote:

Wait, the supercharger only makes the car have like, a half second faster 0-60? :O


And yeah, I know that part, by thew way, I have never had enough power to get anywhere near breaking loose on my wheels. there's no way traction loss can be a factor. and OBD II adapters for android can more accurately document 0-60 times and 1/4 times than me looking at the gauge.

Looks like I aim to beat 8.5 secs and around 17 second 1/4 time then


btw how much does the entire ABS system weigh? or is it just some sensors that allow the breaks to be applied in a way that helps it not lock up? I ask this because I remember seeing "ABS delete" on someone's performance mods, and my ABS doesn't work anymore anyway

No, some supercharged cars are listed at about 7-7.5 seconds, with a 1/4 mile in the mid 15 second range.

http://www.classical.net/riviera/


You should be able to easily squeal one tire with the L36 from a dead stop. Try turning off the traction control. It may be working even if the ABS is not.

Removing the ABS is not that easy. I don't think it weighs enough to matter really.

I think it's interesting that the L36 in the Riv had 205 horsepower, while in the regal and some other cars it only had i think 190 or 195.

RidzRiv wrote:

I think it's interesting that the L36 in the Riv had 205 horsepower, while in the regal and some other cars it only had i think 190 or 195.

are you basing it off of non supercharged v6 or specifically the L36? possibly the pistons are higher compression at 9.4:1? I know the L67 has an 8.5:1.

also, I thought I saw AA somewhere say the L67 riv's were quoted by GM at somewhere around 8 sec 0-60 but I could be wrong :3


and, maybe my riv has always been messed up then, btw I don't have traction control as an option in mine. I have never sequeeled my wheels, ever in my riv, like I could in my step dad's L67 riv. Possibly my engine needs a complete tune up then? Like I said, I plan on taking out the throttle body and cleaning it sometime, possibly replacing it with a better one, but whenever I grab the L67 intake manifold, I'll probably clean and sand/polish that before it goes in for a supercharger if I ever get around to that.

RidzRiv wrote:

I think it's interesting that the L36 in the Riv had 205 horsepower, while in the regal and some other cars it only had i think 190 or 195.

I think some years had the series one N/A engine. That might account for it. I take manufacturer HP claims with a grain of salt anyway. Look at the performance and judge that way.

Yes the non supercharged 3800 series 2. I remember looking up the horsepower specs for my friends 99 regal LS and it said that the horsepower was rated at 190 or 195hp. I'm sure the difference in horsepower was just due to tuning for a larger car.

RidzRiv wrote:

Yes the non supercharged 3800 series 2. I remember looking up the horsepower specs for my friends 99 regal LS and it said that the horsepower was rated at 190 or 195hp. I'm sure the difference in horsepower was just due to tuning for a larger car.

Yes, I have a book with all the specs from 1903-2000 Buicks. In 1999, The Regal LS had 200 HP and 225 TQ up from 98 by 5HP/5TQ. They say due to a better air cleaner and larger induction system. Who knows?

LARRY70GS wrote:

RidzRiv wrote:

Yes the non supercharged 3800 series 2. I remember looking up the horsepower specs for my friends 99 regal LS and it said that the horsepower was rated at 190 or 195hp. I'm sure the difference in horsepower was just due to tuning for a larger car.

Yes, I have a book with all the specs from 1903-2000 Buicks. In 1999, The Regal LS had 200 HP and 225 TQ up from 98 by 5HP/5TQ. They say due to a better air cleaner and larger induction system. Who knows?

Lol, I can tell you for a fact, the stock L36 intake setup that came in my buick is one of the most terrible intake systems Iv'e ever seen. it makes me think GM detuned the engine tbh :3

Thanks for the info Larry! Could it possibly be from tuning of the computer? and Corey, i believe GM may have made a restrictive air intake in attempt to get rid of some of the 3800's notable noises.

RidzRiv wrote:

Thanks for the info Larry! Could it possibly be from tuning of the computer? and Corey, i believe GM may have made a restrictive air intake in attempt to get rid of some of the 3800's notable noises.

I actually like the exhaust note of the 3800. It sounds surprisingly refined for an iron block 90 degree v6 :3

I like it too, the engine actually sounds really "futuristic" or almost robotic to me. It just sounds ahead of its time to me.

RidzRiv wrote:

I like it too, the engine actually sounds really "futuristic" or almost robotic to me. It just sounds ahead of its time to me.

Haha, I'm not gunna lie, the whistle of the venturi is almost as notable as a supercharger whine

Although it does increase air velocity for a small distance, this venturi design is restricting your intake, as well as messing up your MAF sensor output to the PCM. Because of the changes you've made to your MAF tune the PCM takes time to relearn all the fuel trims. Theoretically you could do some MAF tuning to correct this, but it serves no purpose. In the end you are not changing the amount of air your engine can draw through it's intake valves.

Supercharging, of course, pressurizes the intake passages and increases the volume of air now being pushed through the intake valves. If you want MORE air being pushed into the intake runners you can reduce the size of your supercharger pulley so it spins faster, compressing more air.

Eventually you will reach a point where the volume of air coming from the supercharger exceeds the volume of air that can get through the intake valve in the allotted time (valve opening/lift). This is called Boost Stacking and tends to generate extremely high intake air temperatures. Then you need to make valvetrain modifications to keep the intake valve opened longer/higher.

A venturi in a carb is there to create a low pressure area to help atomize the fuel. The fuel inlet at idle (very low airflow) is right next to the low pressure side of the venturi. It serves no purpose in a fuel injected engine unless you put it in the intake runner directly below the fuel injector (which is already atomizing the fuel so no need). It could help atomize fuel to improve idle on large injector applications (high power big blocks, 60 lb injectors, etc. - the larger the injector the poorer the fuel atomization and thus idle quality) but race engines aren't usually concerned with idle quality. In recent engine designs this is being addressed by using direct injection - you can time the fuel release from the injector to the lowest pressure part of the intake stroke, optimizing atomization.

Not sure why this topic was posted in Supercharged tech; thread has been moved to NA tech.

AA wrote:

Not sure why this topic was posted in Supercharged tech; thread has been moved to NA tech.

Oh AA,dats just cold

deekster_caddy wrote:

Although it does increase air velocity for a small distance, this venturi design is restricting your intake, as well as messing up your MAF sensor output to the PCM. Because of the changes you've made to your MAF tune the PCM takes time to relearn all the fuel trims. Theoretically you could do some MAF tuning to correct this, but it serves no purpose. In the end you are not changing the amount of air your engine can draw through it's intake valves.

Supercharging, of course, pressurizes the intake passages and increases the volume of air now being pushed through the intake valves. If you want MORE air being pushed into the intake runners you can reduce the size of your supercharger pulley so it spins faster, compressing more air.

Eventually you will reach a point where the volume of air coming from the supercharger exceeds the volume of air that can get through the intake valve in the allotted time (valve opening/lift). This is called Boost Stacking and tends to generate extremely high intake air temperatures. Then you need to make valvetrain modifications to keep the intake valve opened longer/higher.

A venturi in a carb is there to create a low pressure area to help atomize the fuel. The fuel inlet at idle (very low airflow) is right next to the low pressure side of the venturi. It serves no purpose in a fuel injected engine unless you put it in the intake runner directly below the fuel injector (which is already atomizing the fuel so no need). It could help atomize fuel to improve idle on large injector applications (high power big blocks, 60 lb injectors, etc. - the larger the injector the poorer the fuel atomization and thus idle quality) but race engines aren't usually concerned with idle quality. In recent engine designs this is being addressed by using direct injection - you can time the fuel release from the injector to the lowest pressure part of the intake stroke, optimizing atomization.

Derek,
I tried to explain to him the same thing. He's convinced his car is faster with it. I gave up.