A fellow member can't seen to post because he's having problems with his account, so he asked me to post this for him. His name is Larry Sample.



A good method of determining if your intake flows enough to support your engine flow needs is to hook up a vacuum gauge in the plenum or intake manifold. If the gauge reads zero vacuum at maximum rpm, full throttle then there would be zero or very little gains from an aftermarket high flow intake.

I spliced a gauge line into the vacuum line on the manifold of my 2K2 Maxima and ran it to a vacuum gauge. See pics for gauge and installation.

http://www.fbody.com/members/LarryS/vacuumline.JPG
http://www.fbody.com/members/LarryS/vacuumgage.JPG

At full throttle, maximum rpm (about 6300) I read about 1/2" Mercury of vacuum. This indicates a restriction. I removed the cold air intake box assembly from the box that holds the filter and ran again. This time zero vacuum. This indicates to me that the factory filter is sufficient to flow enough and that adding a cone type filter would add no more hp than simply removing the cold air plastic assembly.

If you have an aftermarket exhaust then the factory filter may become restrictive. All my testing was with factory exhaust.

In summation, an aftermarket freer flowing intake with stock engine and exhaust will help but you can do the same thing by removing the cool air box. My next project is to modify the factory piece so I keep cool air coming in and get a zero reading on my vacuum gauge.
__________________
2K2 automatic Maxima, 1/4 mile time on G tech 14.77 @ 97.5 mph

See my cars - http://xs-fx.com/raughammer/larrysample.htm

 

Thanks for posting this, Kev.

Actually, this isn't the first time I've heard that adding an aftermarket intake provides little or no horsepower increase. But it's the first time I've actually seen someone put that theory to the test.

I wonder how much of a difference exhaust mods make? For example, how beneficial is it to add an aftermarket intake if you have a catback exhaust system or a Y-pipe or both?

I also wonder about the claims made by certain aftermarket intake manufacturers that their cone intakes are superior to all the others. If the OEM intake offers little or no restriction, then wouldn't any cone intake regardless of manufacturer remove the restriction altogether?

Finally, in anticipation of a flurry of SAE-corrected dyno results, how do you explain why one manufacturer's aftermarket intake apparently provides more horsepower than another's?

Good stuff, Larry. Let the controversy begin . . .

 

Someone with aftermarket exhaust hurry and do the same test. If it's true I can take my Frankencar off so I don't waste gas making it make cool noises. lol

 

I LOVE IT!

 

Interesting.

 

Could somebody please explain the "cold air box" since I'm not familiar with what stock item on the Maxima is called by this name? 2K2 only? Does he just mean that goofy scoop which all 5th gen's have?

I love discussions like this.

 

Would a 'smoother' flow of air allow more power? Most aftermarket intakes use smooth tubes instead of the resonator and flex section that look like they would cause turbulance in the airflow.

Someone has to do this on a fourth gen, and on a CAI to prove or disprove the 'fact' that the CAI is restrictive at high RPM. How much does a vacuum gauge cost and what else is necessary to do this?

 

Yeah what is the that "cold air box"?
I just got the FrankenCar intake and I am gona try it and see how it performs.

I can't belive that it won't be adding any more power as this guy's test suggest?!?!

 

I don't know folks.I have had my Frankencar intake on my car for about 1100 miles now.I was bored today so I put the stock intake it to see if I noticed any difference.Well maybe its just me,but the stock will be staying on from now on.I noticed alot more low end which was gone when the Franken went on.Also the quietness is beautiful.Ok enough babbling.Peace.

 

If this is true, how can the dynos by frankencar be explained?

 

Yea that's what I was thinking. How come some people see gains on the dyno?

 

What is a plenum? And for other cars, how do you know which line is the vacuum line?

I think the brain plays a lot of tricks on people. That is why people w/ intakes think they are going faster, b/c of the awesome sound that aftermarket intakes provide.

 

I don't think that they dynoed the cars with the cold air collector removed. They dynoed with the full OEM intake then redynoed with the cone intake. To verify this theory on a dyno someone needs to dyno with the full stock intake, disconnect/remove the cold air collector then dyno again.

 

same here. I went from CAI back to OSCAI with an K&N panel filter. Great low end and it's still pretty responsive on the highway.

 

there is not way this can be true if there are dynoes to back up gains with intakes on several 2k2's and other maximas. engines generate a HUGE vacuum and every little bit helps along with replacing the restrictive and turbulent mid section and increasing the intake velocity will all yield gains. i could see this being a debate if there weren't A LOT of dynoes to prove that intakes add hp but there are and there are more factors to improving hp then just if there is a vacumm or not.

also i notice a power drop when i take my intake off, and i don't notice much if any loss of low end torque.

-steve

 

Now all the talk about no results on pop or cai.. What is it? I just got a pop charger and i love the growl at wot, but thats the only time i can hear the intake.. I thought that there was to be a gain to put these filters on than the stock.. Damn.. I dont know what to do? Is this a conspiracy? IS this only a hype that will soon fade? I mean the money these auto guys take for the products they sell is outragious. Come on 70+ for a filter, then tubing will add another 80+. Omg if this is true then we are wasting our money for nothing but a big ol expensive sound that can be achieved by taking the resinator out.. Gez.. I mean i lost my low end... what else am i gonna lose, my mind... Can some one please settle this so i can get a good nights sleep..

 

Now all the talk about no results on pop or cai.. What is it? I just got a pop charger and i love the growl at wot, but thats the only time i can hear the intake.. I thought that there was to be a gain to put these filters on than the stock.. Damn.. I dont know what to do? Is this a conspiracy? IS this only a hype that will soon fade? I mean the money these auto guys take for the products they sell is outragious. Come on 70+ for a filter, then tubing will add another 80+. Omg if this is true then we are wasting our money for nothing but a big ol expensive sound that can be achieved by taking the resinator out.. Gez.. I mean i lost my low end... what else am i gonna lose, my mind... Can some one please settle this so i can get a good nights sleep..

 

On N/A Motors, I thought creating more Vaccuum was the point of creating more power ??? The engine is responding by being able to draw in more air ? Isn't that the point ? So if you want a gain, there has to be "pressure"(psi) on a N/A Motor ?

Please, think about this thread a bit better, and think about what I just wrote out.

Screw Measuring Vaccuum, how come CFM~????????????
Do the search and find a way to measure CFM ????

CFM, THAT'S WHAT FLOW IS~!~!!~~!~!

NOT VACCUUM OR PSI....THAT IS PRESSURE....

If your car was force fed, then isn't more Psi = more resistance as well ? But guess what Psi gains Hp.(given cfm goes up in proportion.)

Conspiracy theory no, just a bunch of freakin lemmings on the .org like Bill, Clee say there are. Once one person jumps on, everyone does. Oooh low end is back, but I guarantee your RPMS do not climb as quick in the high end, before my current mods, I ran w/ my stock box, and I'll tell you something, I lost major top end, and it wasn't the butt dyno.
I drive fast no matter what, low end felt better, and it shows in my 60 ft times, but my traps dropped and time gained almost 0.3s in the 1320. (2.31 vs 2.22)(93mph vs 90mph) (14.99 vs 15.02-15.04)
All freakin day I was kickin myself.

Same thing w/ exhaust. Toylet ran 0.5s better w/ a free-flow muffler vs stock, and all he has is an intake as a constant. (15.4 vs 14.9) I gave him my intake system, and we'll see what he runs.

-Lemming Watch is ON~!

 

Come hither LEMMINGS!~~!~!

-Bump.

 

 

Chimpy is on the LEMMINGS cliff diving call out bandwagon.

hehe

 

And I'm still waiting.

 

Im a little confused by what you said. Your times were better with or without the stock intake?

 

yes i know vg autotragic. what gains can it get..lol shiet its better than nothing. Just that my intake sounds loud now...So why post things about no results when there are , even little improvement. I need to go back to skool and learn things like physics.... am i destine to have a slow max...i guess its set in stone

 

on what ?

Times were worse w/ stock intake.


Gained = +0.3s

60 ft: 2.31(intake) vs 2.22(stock intake)
traps: 93mph(intake) vs 90mph(stock intake)
times: 14.99(intake) vs 15.02-15.04(stock intake)

 

well there is the low end..lol..chimp, u think my speed trap will increase just a little

 

been knocking on 90mph, so why not ?

Toy knocked on 95mph, w/o a Y-Pipe, so why not right ?

This was before I swapped in my system, but I'm sure he'll raise a few more eyebrows at the track again.

-Peace

 

I am not sure if my max is"Better" b/c of the pop upgrade... I guess that i have to wait for the 7th gen to come out so that i can some real fun.. But i just love my 3rd gen too much.. I would have to agree with you... More air= more power, right? but this simple thread about loss of performance has to be reconsiderd... I mean people have po and cai intake, and their maxima's perform better than stock.. All and all with mods there are always trade off.. To gain one thing is to lose another..

 

Any mod you to do a car to enhance performance compromises it at the same time.

Its not a matter of more air = more power.
Engine is a big air pump, and adding fuel and spark complete the equation of power.

Larry's point was providing an example of vaccuum as a bad thing on a N/A Car.

My point is, Vaccuum is a good thing for a N/A car + he confused "flow" w/ "pressure vs vaccuum."

If he wanted to measure "flow" then measure the "cfm" of air coming in stock vs aftermarket intake system.

-And I'm still waiting for a Lemming to rebutt me.

 

does he mean that when the vaccuum is zero, that the engine is getting sufficient air? and when he is getting a reading then that would be that the engine is struggling to get efficient air into the manifold??

 

Now I can make replys! Thanks for letting me join in Kevin.

Way to go Victor! You seem to understand the theory best of all!

 

Larry, thanks for the test. It's interesting. But IMHO, an normally aspirated engine MUST be making at least some type of vacuum all the time. ie.. high vacuum readings at idle/low rpms and lower vacuum readings at high/high load rpms. As I understand it, an NA engine can approach but never = no vacumm(ie.. atmospheric). If the engine actually could achieve a no vacumm condition, I don't think the car would actually run. As Chimp mentioned, an engine is an air pump. If the pistons aren't drawing any air, the engine isn't making any power.

The reason I sorta doubt this test is that you placed the vacumm guage source line in the manifold. A place where there should always be some type of vacumm(however little)

 

lol. thanks. i tried my best.

 

Ok Jeff, lets see if I can help you out here.

First of all, if you have any flow at all you have pressure. If you can believe that then if you have flow into the combustion chamber you have vacuum in the intake manifold or pressure going into the combustion chambers. Correct, the engine would not run without this pressure. Ideally however, is to have as little vacuum as possible so the cfm is increased. With more vacuum you have less cfm.

You are correct in saying that an n/a engine is making some vacuum all the time or you would not be filling the cylinders. Because this Mercury gauge reads zero does not mean there is zero vacuum. If we could mount a monometer filled with water and read inches of water column we would get a more accurate reading. Although a zero reading with the mercury gauge is an accurate enough measurement that you have done just about all you can to increase hp on the upstream side of the point of measure. You have a large enough filter, mass air meter, throttle body and every component to the point of vacuum measure.

Should you increase the size of the intake ports or any portion of the intake past the point of measure all the way back to the tail pipe, vacuum will increase as you increase engine flow. But nothing on the upstream side of the point of measure will give an increase in flow or hp.

 

i found it, heeh good write up hogan.

-steve

 

Okay, so we have determined that there must be a vacuum source no matter what.

Now the 2nd question is, was the max rpm test done under "load" or "no load" conditions? ie.. driving the car and flooring it until xxx rpms vs just reving the car in neutral? Although the rpms might be the same, the volume of air being used by the motor is very different. If you are just reving the motor, the amount of air is much smaller, thus a no restriction reading. That might not be the case under full throttle, high load, rpm running.

Just trying to get a feel for the test.

 

Interesting. I still want a aftermarket CAI

 

Jeff,

The test was conducted at full throttle in gear. The vacuum maxed out just before the shifts. I only read the 1-2 and 2-3 shifts. There was zero vacuum at lower rpm. Vacuum started building somewhere above 5000 rpm approximately. Getting good reading at different rpm is difficult as you would have to look at the vacuum gauge, tachometer and road ahead at the same time. Would need two buddies to ride with me. One for vacuum gauge, one tachometer and me the road ahead. Below 5000 rpm, full throttle, I am sure the factory intake is not a restriction on my car.

 

I will agree with the fact at the low to mid range rpms the stock air box (less the worthless fresh air duct on the core support) will flow the proper amount of air when all else is stock. But add the mods and even that will change. No, I don't have scientific proof it's just basic math and mechanical knowledge. The internal combustion engine is a air pump, you can not take more in than it can push out. Open the exhaust and it's a hole new chapter in the book. What it really comes down to for me is BaaaaaWaaaaa......what a RUSH! when my tach swings past 3500!
l8tr -- SS

 

Which should I do for more hp in low-mid and high (best of both worlds?) OSCAI or Frankencar.