air intake

[ismellrealbad]

my guess is that it has a similar effect as does a cat does on exhuast. if you end up ripping everything off, res,cat,muffs and just run straight pipes, you loose backpressure and end up with REDUCED performance. doing this to a degree is what helps, like a hi flo or just ripping the cat out, but to leave everything else on including muffler(s). sometimes rupping just the muffler(s) off helps. i dont know, like i said im just gunan rip the airbox off and whomp on the gas and see if i gain anything from it

 

slower=stick with airbox

faster=new intake

[JPaganel]

Yeah, but what is the connection?

 

OK, as I understand it, the engine is a big air pump. Bigger inlet/bigger outlet make it work better. Backpressure helping performance is counter-intuitive. I know what you're saying, but what I don't know is why this happens.

[Brian P]

It's got to do with air velocity....I dont understand why people get hung up on "backpressure". You don't NEED back pressure, you need velocity, that is, get the exhaust out as fast as possible. I saw a great article by a person over at 60degreev6 that knew his shit. If I find it I'll link it. You can have an exhaust with zero backpressure, but if you overdesign it (like a 3 inch straight pipe) the air is just going to slow on a naturally aspirated engine. The easiest way to get the exhaust gases out fast IS by creating backpressure, so yeah for our applications, you don't want 0 backpressure, but for drag/funny cars they have intakes and exhausts that are created well enough so that there is no "backpressure" PLUS the air moves at the fastest possible rate. Again, not for us...

I found it hard to believe that the OEM intake was of benefit....I even had removed the snorkel a few years back and it seemed to get faster, but it was all PLACEBO. As soon as I put the snorkel back on and sealed it up, the engine felt healthy again. There was a time that the snorkel partially came off my airbox while driving, I thought I had lost a cylinder or something because acceleration sucked. I'm tired of hearing all this cone filter marketing here. Moved.

[ismellrealbad]

um er, pardon me, wouldn't powertrain be a more logical place for this thread?

[Brian P]

OH CRAP! thanks!

[gpse3200]

I'm an Automotive Engineer...................If thats not good enough for you than I don't know what is.

 

Personally, I believe you. Now that that is out of the way, can you explain why it works like that , or at least point me in the direction of an explanation of the theory behind this effect? I'm not doubting, I just wanna know why. If I find out, I can further my reputation of an exceedingly smart guy and impress all the chicks with my superior automotive knowledge...

 

ehk....I'll start over and try to explain this better. Hopefully this won't run on.

 

The 2.8/3.1 FI intake GEN1 and 2 have a particular setup. The small width, long length runners(about over a foot long if you were to measure it) mandate that the air be rushed in. This is your typical Torque Setup of TPI.

 

The Venturi effect is when a media is squeezed though from a bigger opening to a smaller opening under a pressure difference, The media is accelerated. Say turning a bottle upside down, the weight of the fluid above is rushing the fluid below out the bottle's small opening. When that happens the the media coming out of the opening is accelerated and much faster moving as opposed to the media above it.

 

The Venturi effect is most consitant with a TPI setup of the small diameter, long runner style of intake that we have. The faster you can get the air into the Combustion chamber, the more Horsepower you'll make, mostly you'll make way more torque. Torque like High speed rather small quantity of air, Horsepower likes Lower speed Larger quantiy of air.

 

Now lets look at the W car. It would seem that it's a two stage setup in the sense that there is one system to hit up first. The snorkle at the end under a pressure difference from the moving pistons with the open intake valve is causing the air (from behind the headlight ouside, not from the engine compartment)to be squeezed though that opening, notice how it opens up after the opening. Now maybe the shape is odd due to the clearance issues, but the size is good. If there was enough space I'm sure it would be a circular opening of the same thing. Either way it would do the same thing. Now you get to the TB, the air from the Air box is already moving at a high rate, when the air is squeezed though the TB it really hauls. After that the air goes though the plenum down the corresponding runner at high speed. So in a way the air box is kinda an accelerator. This is good for the 2.8/3.1 kind of Intake. The faster the air gets in the better power you'll make. Quantity is good naturally but not as much as the speed of the quantity. And thats how GM has it setup. this may all apply tot he 3800, though earlier models have short runners, they also have small diameter runners.

 

Now the problem with that setup is yeah when you need more air, TPI is Tuned for a specifc RPM/ rpm range as per equpiment. In our case we peak out at HP 4800 RPM and we are tuned for max vol effic at 3600. So how do you counter act that? You do it internally. Changing the cam, doing port work, or increasing displacement and if applicable, using a larger TB of the same or similar style(this one is sktetchy but would seem to work out in this setup seeing as how the air is funneled in yet still). And when doing that it may be nessesary to alter the ouside unit, maybe a bigger snorkle, not changing the whole general design as it would still be a best match to the engine intake. So as you can see this engine is very particular to what it wants. But going around adding venturis is not the answer either ultimately it will impede power. And using an exterior intake that is not similar to what the stock one is won't help you much either, it'll just make noise. With the proper work you can make your TPI setup run from idle to 5000+ RPM, I'm proof of that as well as many other people. But even though I'm breathing at a high speed and moving more air, the air box is still setup to assist the Intake. So with interior work you can pull in more air yet still have the speed of the air rushing in. The High speed TPI can almost be compared to a forced induction in a way. Also the stock filter is big enough to handle extra power increases.

 

Now some engines like the twin cam and the quad4 like to breath alot all at once. Their style of TPI intake is not tuned for velocity. You'll notice the larger diameter runners. I would say they are shorter in length too so they seem, its pretty close...Anyways the hope for that style of engine of making high velocity for torque is either though its sheer displacement, cam work, or gearing. So as you can see adding venturis to this setup is not going to work unless say the engine has bigger a displacement. You'd have to put a big venturi in a setup like this and with that you'll impede power. Short, fat, runners do not like that. So the best thing is to give them damn near unrestriced airflow. Now I'm not saying that the air box on this engine doesn't help it out, it just might give it some response but it doesn't seem that it can fulfull the top end power requirements of that setup. Considering what's avalible at the lower engine speed anyways, you may as well just use a cone filter anyways and get your 5-10 hp from that.

 

As far as cold air is concerned, pulling it from behind the head light is fine, that is outside air. With the light on that area doesn't get that warm, esspecially at speed, thats good for the 2.8/3.1. But pulling air from the engine compartment with a cone filter will cause lower performance. Even lower on the 2.8/3.1. Also the air box snorlk should be sealed with RTV as to not pull in any engine compartment air except fromt he front snorkle. As far as the twin cam and quad 4 is concerned, air should be pulled from the outside with a cone filter utilizing a large diameter duct.

 

Now a Higher flowing drop in air filter would be nice for the 2.8/3.1. thr Kand N drop inthough is not the best thing though as it's pleating is done the wrong way(longitudinal) that the air is not being directed in the right direction. I've consistantly lost .1-.2 of a second in 1/4 mile times this was a clean filter mind you. This is something you won't notice but you'll see at the track and for $50 won't appriecate either. Even removeing the air filter causes even more of a loss. About .5 seconds in the quarter. Adding the airbox gave me a whole second + back. Whats the cause of all of this? Turbulence. 2.8/3.1 like any other engine doesn't like turbulence, now the kn filter straighten the air like the stock filter does but the air is getting pulled against the filter the wrong way thus causing a small amount of turbulence. As far as the KN is concerned this was a conclusion I came up with, because otherwise its a nice quality filter. The only thing different is the pleating. I bet if the pleats were lateral the KN would be a nice little item to have, in fact i wonder if Holley's has a filter for the W car. I wouldn't use a drop in filter on a quad4 or twin cam, just a cone.

 

Exhaust. The 2.8/3.1/3.4 have the manfolds they have because of space issues(lets face it these engines went into some really small cars), it also helps out a touch with bottom end torque but I wouldn't rely on it as a performance item. The W car is the biggest most demanding application for the 2.8/3.1 but I guess GM though it was cheaper not to use a header setup, and well the twin cam simply doesn't have a whole lot of room....barely enough room for the engine as it is. The 3800 wins out because it was put in primairly C and H bodies, like 10 times bigger tan out cars(exaggerating). Hell the N body even has enough fore and aft room for a rendition of it. But even with headers the need for a 3 inch exhaust on theses engines is ill advised. A hot exhaust is good, the hotter it is, the more energetic it is the faster it will leave the system. Making the pipes huge will cause the exhaust to cool down and slow up. That means that the engine has to push hot exhaust through cold and slower exhaust, a barrier. On a stock 2.8/3.1, the factory 2 1/4 to 2 y-pipe setup, or '89(2 inch to muffler with a 2 inch croosover)-'90 GPSE setup is just fine for it. The '90 GPSE setup is a 2 1/4 all the way to the back and the crossover is 2 1/4. Unfortunalty it was made in the beginning of '90 and then went to a y pipe setup. The '89-'90 GPSE set up has a very unique sound that I miss. Picture an 80 series flowmaster mounted on the passenger side fore/aft with one of the exits facing aft and the input and another exit facing fore. At the fore exit take a crossover pipe to a muffler on the driver's side. Very weird sounding, very nice sounding:) Use any muffler you wish! The other reason why with headers you won need a huge exhaust is because about the same amount of air is comming out if not more. Also I'm not too sure on this but I think also the way how a 60 degV6 is timed has something to do with it. As far as the twincam is concerned I'd say 2.5 to 2 1/4 y pipe, no bigger. Quad 4 smaller. But I'd recommend changing the catalyst if you all want mroe sound because GM used a big converter and it acts as a resonator. You won't get a real loud sound unless you change it to the smaller freeflow style thats avalible at parts stores for about $70-$90( if you can see light though it you got the right one). They are all free flowing, in fact the GM ones are free flowing too just that its big. There hasn't been a horribly restrictive converter since the early 80's that had the pellet design. The Monolithic style is very good(unless made very crappy or clogged), and considering how we can clean up the air by using these, the price of the restriction is very minute. We should all use them.

 

Wow this was by no means short.... My recommendations for the 2.8/3.1 is stock air box sealed snorkle with rtv, stock AC Delco air filter, engine changes, possibly a larger TB, a lateral pleated kn airfilter, replacement small style catalyst, 2 1/4 2 1/2 max exhaust main pipe. Y pipe- 2 to 2 1/4 max piping. Same thing goes for the 3800. For the twin cam and quad 4 I'd say cone filters, intake re route with large diameter duct, and 2.5 to 2 1/4 y(twincam) smaller for the quad 4. Hope this better helps to understand some of this stuff....

[gpse3200]

ACtually I should say that the S10 style #1 and #2 the Camaro/Firebird is tied with the W-car as being the most heavy application.

[JPaganel]

Wow. Talk about your quarter explanation... (as opposed to the dime explanation)

 

OK. I see what you're saying, it's the velocity of the air going in that's important. I had an idea of building a custom airbox with the stock snorkel but with a cone filter inside. Now, what do you think of this? The stock snorkel would keep the velocity up and the cone should help with flow. I have one of the double cone filters with the little inverted cone on the end, so that may work out to advantage there...

[gpse3200]

Well like I said before the stock filter has more than enough capacity to flow... You also need the air to be properly directed if using the air box. Confining a cone filter doesn't make it do it's job properly, it needs to be completely exposed. So I think you'll hurt performance. If you want and nice filter check out Holley, they have a line like kn's they might have somthing for the w-car, hopefully the pleats are in the right direction. I was also thinking that removing the muffler inside the airbox, the extension tube of the snorkle, see if that nets more power. In a way it's almost like a runner but I think the air isn't going much faster in that part after the snorkle. I'm telling you put on the cone filter or drive without the air box you'll know what I mean. For the 2.8/3.1 its not a restriction, its a helper. On '88 models with the MAF sensor, the coffee can would work out too, esspecialy since it has a gasket to from the engine compartment to the chamber behind the headlight, the only problem is the MAF sensor gets in the way and that is a restriction. In fact the cars run better with '89+ style box I recommend a switch over for '88's to '89 engine mangement and induction. Also it would probably be a good idea to get an air duct that isn't so corrogated.

[JPaganel]

You know, it's a good day for ideas for me...

 

Ok, suppose I put the snorkel after the filter? (inside the cone?) The air would be speeded up and it would retain that speed all the way down the intake tube, wouldn't it? It wouldn't matter how the pleats go, then...

 

I have to get a spare airbox and try this now...

[Guest]

I just want to add in here real quick that my Cutlass is a 1988, and it originally had the MAF (the programming never got updated from the factory to speed density, so the MAF was working as a MAF). I one time took the lid off of the can, and drove like that for 2 miles, and the car performed BADLY. Needless, to say, I pulled over on the side of the road and put the lid back onto it. Later, I updated the programming with the speed density, and the car drove even better, but now, I have updated the car with the 89 programming, and the 89 airbox, TOTALLY GETTING RID OF THE MAF, and the car is at its best now. Changing the air box from the round one (which I had a K & N DROP-IN in it by the way) to the square box of the 1989 has been the best thing that I have done to it (not counting the cam). I can say from personal experiance that the car works its best if you use the STOCK AIR BOX WITH AN AC DELCO AIRFILTER. I have tried everything for my car (2.8L MPFI) and the 89 programming and the stock airbox are still the best.

 

Taylor

[cutlassdude96]

What about the 3100's are they the same as there counterparts as air flow goes, I also put in a Fram air filter in it a whole lot better than that old dirty AC filter. I also got a 91 Calais with a Quad4, would a drop in K&N type filter work or a cone style work. They get there air from down below by the wheel well.

[gpse3200]

The 3100 is a mystery...because it's kind caught in the middle. Its got a ventury type TB and airbox snorkle but the engine has fatter yet overall shorter runners yet its kind of set up similar to the GEN2. With that motor you are damned if you do, damned is you don't. When I do my refit I will definately see what works best with an altered 3100 styp upper end. As far as the Calais is concerned I think if the filter looks like the stock one as far as pleating and such, then I'd say a kn drop in would be good. Today I placed an order for the HOLLEY brand cloth air filter, a direct competitor to the kn. if I find that the pleating is the same as stock, i'll be more than happy to try it out. kn is good its just with the w car I think they messed up a touch.

[Chinski]

Now you've got me all confused. I can understand that the velocity of the air is important on the 3.1/2.8 but it seems to me that you are saying that the air coming in the small opening of the extension of the air box, then going into the larger airbox and back to a small, non-smooth hose to the engine helps with the velocity as it is a venturi. Now we are working on some venturi stuff in my fluid dynamics calss and learned that a venturi goes big-small-big as far as cross sectional areas go. This seems opposite of what you are saying...but i kinda got lost in your explination as it was so long. The mass flow rate has to be constant right? So wouldn't the air box slow the velocity down? Anyway, wouldn't a cone filter with a venturi after it increase the velocity of the air? I'd have to think that a smooth pipe would also help over that thing that's in there now (it cant be helping the flow velocity or direction with all those pleat things causing turbulance). I hate fluid dynamics

[gpse3200]

Now you've got me all confused. I can understand that the velocity of the air is important on the 3.1/2.8 but it seems to me that you are saying that the air coming in the small opening of the extension of the air box, then going into the larger airbox and back to a small, non-smooth hose to the engine helps with the velocity as it is a venturi. Now we are working on some venturi stuff in my fluid dynamics calss and learned that a venturi goes big-small-big as far as cross sectional areas go. This seems opposite of what you are saying...but i kinda got lost in your explination as it was so long. The mass flow rate has to be constant right? So wouldn't the air box slow the velocity down? Anyway, wouldn't a cone filter with a venturi after it increase the velocity of the air? I'd have to think that a smooth pipe would also help over that thing that's in there now (it cant be helping the flow velocity or direction with all those pleat things causing turbulance). I hate fluid dynamics

 

 

I never said the air duct was good, I said we should change it to a smoother type. The air will slow up in the box at the filter primarily but it wouldn't be as fast by the time the air got to the TB if the snorkle wasn't there. As far as the box itself is concerned, it holds the filter, now the filter also directs the air in the right direction, granted it would be better if the pleats were angled toward the air duct but that is $$$. Look I can only explain this shit so much and I'm trying my best to explain it and I think I did it very well, long or not. Not all the same shit works on every Engine despite what the commercial marketers want you to beleive. If someone would take the time and find a different way to make power for this style then we'd make some power. Its like the shit about at the rear leaf spring all over again. No one wants to take the time to understand the fucken thing so we start putting on shit that don't belong there and looks like crap and operates like crap. I already challenged you all to drive your cars with whatever setup you have or wish to have and then drive it with the air box on. If you don't want to take the challenge, you don't believe me, Fine. Use your cone filter, deal with the power loss, and the extra noise. I'm done typing so much on this....

[gpse3200]

Anyway, wouldn't a cone filter with a venturi after it increase the velocity of the air?

 

Hmm I missed this part:) You see thats an idea that might work out very well, but once again you are now pulling air from the engine compartment, thats whats good about the box becasue it doesn't absorb heat that well since it's a thermoplastic, and it pulls air from outside the compartment. But still if the intake runner were too long then the air would slow up and you'd have to keep using veturis which would then ultimately then impede quantity. I like ths box. I like this box because it works. I need to stop typing on this!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :!: :!: :!: :!: :!: :!: :!: :!: :!:

[ismellrealbad]

one pop, you just cant stop :fruity:

[gpse3200]

Hmmm..I could go for some Pringles Brand Potato Chips. Less fat thanks to OLEAN!!!!!MORE TRIPS TO THE BATHROOM THANKS TO OLEAN!!!! :? :!: :!: :!:

[JPaganel]

Anyway, wouldn't a cone filter with a venturi after it increase the velocity of the air?

 

Hmm I missed this part:) You see thats an idea that might work out very well, but once again you are now pulling air from the engine compartment, thats whats good about the box becasue it doesn't absorb heat that well since it's a thermoplastic, and it pulls air from outside the compartment. But still if the intake runner were too long then the air would slow up and you'd have to keep using veturis which would then ultimately then impede quantity. I like ths box. I like this box because it works. I need to stop typing on this!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :!: :!: :!: :!: :!: :!: :!: :!: :!:

 

 

Yeah, and you missed my whole damn post on that just up the page... You're ignoring me, I'm gonna go cry now...

[gpse3200]

Hmm You posted?....

 

"You know, it's a good day for ideas for me...

 

Ok, suppose I put the snorkel after the filter? (inside the cone?) The air would be speeded up and it would retain that speed all the way down the intake tube, wouldn't it? It wouldn't matter how the pleats go, then...

 

I have to get a spare airbox and try this now..."

 

Ok, very close to what the other guy said.....Same response then. Sorry I missed you!!!!!!!!!!!!!!! :? :? 8) :!: :!: :!:

[JPaganel]

Mwaahhahah! It worked! He posts yet again! :devil:

 

Actually, what I was thinking of doing was remaking the box with a larger intake opening and the venturi after the filter using a smoother pipe.

 

I'll see if I can do it and post pictures. With a little fiberglass, anything is possible...

[Brian P]

I had made a smooth metal pipe going from the stock airbox to the throttle body. Yes it did make a noticeable difference at higher RPM (3000+), however make it a note that THIS PIPE MUST STILL FLEX because the motor will always flex somewhat (well, more than the airbox ever will), so don't make it out of a hard material, such as metal, dammit.

[gpse3200]

Mwaahhahah! It worked! He posts yet again! :devil:

 

Actually, what I was thinking of doing was remaking the box with a larger intake opening and the venturi after the filter using a smoother pipe.

 

I'll see if I can do it and post pictures. With a little fiberglass, anything is possible...

 

That would be cool, but it would be better if the air can be pulled from the outside, or at least the minimum be effectively shielded from the engine compartment.

[stlunatics2oo3]

how could you make a heat shied with a cone filter since the space in the 2.8s is really tight and with what materials i did a stupid thing and tried usin keter pipin over it and the negative and positve of the battey touched and wham i was like electricutted so what material should someone use

[JPaganel]

keter pipin over it

:?:

 

You used what over what? Sorry, I just can't figure it out...