Making my own cai

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Guest

Making my own cai

Postby Guest » Mon Jan 06, 2003 12:27 am

My quad is almost back together after waiting four months for an ARP head stud kit from Summit. When I bought the car somebody took the tip of the snorkel off the air box (along with the factory filter inside) and shoved a cone filter on the end. It was pressed right up against the rad! This setup of course did nothing but harm. I'm going to be making my own CAI for it and I'll be using the inner fender for the pick-up area.

Is it true that when adding a cone filter you lose some torque? Because once I open up the exhaust side of things I don't want to lose even more torque. My idea is to leave the stock air box in and install a K&N drop in. Then run piping from the air box to the inner fender. I'll also replace the piping from the throttle body to the airbox for better flow. This way I still get plenty of cold air and maybe I won't lose the torque by using the airbox.

So what does everyone think?



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Making my own cai

Postby KFLO 93 GT » Mon Jan 06, 2003 2:00 am

I have never heard of losing torque from a cold air intake, and you won't lose torque from exhaust unless you go too big.  Go 2.5" on the exhaust and you'll get peak power without torque loss. ÂÂÂ

I dunno about quads, but according to the trusty butt-dyno my intake gained me some torque. :laugh:  I have a 3.1 btw.






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Guest

Making my own cai

Postby Guest » Mon Jan 06, 2003 8:40 am

Thanks for the info. Maybe I can save myself some piping etc., and just run it from throttle body to inner fender.



Guest

Making my own cai

Postby Guest » Mon Jan 06, 2003 10:57 pm

How does everyone go about the first attachment off the throttle body. The throttle body opening is oval and the rubber elbows I can find are round. Do they form to the oval opening?



Guest

Making my own cai

Postby Guest » Tue Jan 07, 2003 12:03 am

Why are you going to the fender well for intake air?? You can gain some ram recovery if you run the "factory" setup from beside the headlight (that some people want to replace for some reason) or do what I did on my '92 GT and run a 4 inch  flex duct from the factory air filter box (with a K & N drop in) down to the left side of the upper chin scoop to a simple intake scoop that faces dead ahead. You can do this simply as long as you at least have a stub of the snorkel left. Some people have been replacing a system designed for engines of 2.3/2.4 /2.8/3.1 litres displacement with a system designed for 1.6 litre engines. 2.5 and 3 inch ducts?? Go figure.



Guest

Making my own cai

Postby Guest » Tue Jan 07, 2003 5:07 am

The idea is to get RID of the factory air box.......it's one of the main things resticting airflow. In addition, if you can add a good length of pipe, you may be able to take advantage of some resonance supercharging....NOT something you can do with the factory system. Also, cone filters by nature have more surface area than flat filters.........this means more airflow.

BTW....2.5 and 3.0 inch piping should work fine as long as it's mandrel bent, and doesn't have too many twists and turns. Remember, the stock throttle body on a Quad is only 56-57mm (2.5in = 63.5mm, 3.0in = 76.2mm......both larger than the TB). I'm not saying that larger than 3.0in piping is bad, but rather, that it may not be necessary (or possible due to space restrictions).



Guest

Making my own cai

Postby Guest » Tue Jan 07, 2003 9:57 am

Oh I'm not going to use anything bigger than 3". I don't need my engine bay looking like a furnace. I'll have plenty of room for a long pipe with the stock air box and piping removed.



Guest

Making my own cai

Postby Guest » Tue Jan 07, 2003 7:43 pm

The air filter box in itself in not restricting airflow. I admit that the snorkel inlet size and the design of the airbox system is possibly a bit of a tradeoff for sound suppression but you will find that the airfilter box inlet and the outlet are about the same size. It it worries you remove most of the snorkel, nothing else & and use the K & N drop in. The only thing that happens is that the air flow slows up slightly within the airbox (which increases the pressure slightly) then speeds up again as it is forced into the airbox outlet (increasing in speed and dropping in pressure back to where it was. (Bournoulli's principle) It is called a diverging-converging duct. BUT.. using a 2.5 and maybe even a 3" duct the length of which I have seen some people using may be causing what is called "duct loss" where the friction of the air as it is forced along a long, less than big enough duct or pipe causes a loss/restriction in airflow. G.M. engineers are not complete idiots. Resonance supercharging is a fine science far beyond the scope of the aftermarket companies and most people designing/supplying the inlet ducts/pipes that I have seen, and is normally accomplished by engineering the intake system downstream of the throttle anyway. Unless these guys are airflow engineers don't believe everything you read.



Guest

Making my own cai

Postby Guest » Tue Jan 07, 2003 8:31 pm

Quote (RPS @ Jan. 07 2003,18:43)
The air filter box in itself in not restricting airflow. I admit that the snorkel inlet size and the design of the airbox system is possibly a bit of a tradeoff for sound suppression but you will find that the airfilter box inlet and the outlet are about the same size.

Have you seen the airbox on a Quad?

Seriously, this is one of the goofier stock intake systems I've seen, and can definately be improved upon. For one, the airbox and the filter are SMALL, and for another, ditching the airbox will eliminate 2 90 degree bends and a 60 degree bend in the airflow, not to mention the ridiculously small inlet snorkel. Throw in the benefit of a cone filter having more surface area to draw air from (and therefore less restriction), and the *possible* resonance supercharging effects, and a full length cold air setup with a cone makes sense.

Yes, it's true that resoance supercharging is not something you can just engineer in (it's very hard given underhood space restrictions), but it does happen on a fair few intake designs over a period of a few hundred rpm in the powerband.

An example: http://www.se-r.net/about/200sx/scc/april98/april3.jpg

Notice the HP spike around 4500-5100rpm (this is on a bolt-on 200SX SE-R BTW)....this has been determined to be caused by resonance supercharging (differing pipe lengths move the spike around). Sure, maybe whatever intake you design for your Beretta MAY not have a similar spike somewhere, but it's hard to tell without doing it, and then slapping it on a dyno.

Also, the differing pressure waves you were describing can be thought of another way......restriction. Sure, a simple, smooth neck down (such as that on a coned throttle body....something found on stock 3100's) can decrease restriction as opposed to just dropping to a smaller pipe size, but when you start varying from smaller to larger and vice versa, you lose any benefits you might have gained.



Guest

Making my own cai

Postby Guest » Tue Jan 07, 2003 10:22 pm

I"m not talking "pressure waves" upstream of the throttle here. I'm talking airflow and air pressures which is what is important here for your average Beretta owner. To get down to basics it is to get the coolest air at a pressure as close to ambient pressure as possible to the T/B, and then obviously to the cylinders. Another comment here.... I have seen (on a TNN TV show among others) some intake duct installations where the air filter is installed right in the grill area with the intake duct then going to the T/B. A wet air filter will restrict air flow to a degree which can cause performance issues. Notice that in a factory/properly designed system there is an effort made to keep rain water etc. from wetting the air filter. For example a drain system or some kind of an "updraft" design where the water will drain down/out against expected airflow is used.  I believe even a water soaked K & N will cause a  drop in airflow, but maybe someone has info on this.



Guest

Making my own cai

Postby Guest » Tue Jan 07, 2003 11:28 pm

O.K., did mean to start a debate here. :D  But I guess a good debate always helps clear up stuff.

I'll lose the airbox and use a cone filter. But I'm not putting it in the grille, a wet anything isn't good. Even a K&N will most likely lose airflow because of water. I'm going to put it in the inner fender where its covered from most of the elements.

Now, should I use 3" or 2.5" piping?







Guest

Making my own cai

Postby Guest » Wed Jan 08, 2003 8:09 am

don't they make water inductions to prevent water ingestion (sp) i've seen them for 30-40 bucks in sport compact magazines, althought if you put it in the grill you'll still get other elements. but you'll get rid of the water even put it towards to bottom of the car i would think.



Guest

Making my own cai

Postby Guest » Wed Jan 08, 2003 9:22 am

Yes, AEM makes a water bypass valve. It'll open up and let all the water out before it gets to the engine and it still lets the engine breathe. But you'll still end up with a soaked filter which won't flow as good. And the bypass valve isn't an air filter so when its open and your engine is breathing through it raw air is being sucked in. Not good for long periods of time.



Guest

Making my own cai

Postby Guest » Thu Jan 09, 2003 1:02 am

I've been thinking (dangerous right?) about this topic a bit. What if I left the airbox in the works but left it empty and used a cone filter in the fender. I'd still replace all of the piping, from throttle body to inner fender. Would leaving the airbox installed add a air reservoir the engine can use? Or would it just screw up the flow of air and make the piping too long?



Guest

Making my own cai

Postby Guest » Thu Jan 09, 2003 11:51 pm

If you use the fender well you are giving up something for free in the form of ram recovery which above about 50 or 60 MPH is worth while taking advantage of. I can only speak for my '92 GT 3.1 but without any rework of/or relocating anything I routed a 4 inch flex duct from the air filter box using the stub of the snorkel as the connector on the air filter box, down behind the headlight, looping down to a forward facing inlet scoop mounted in the upper chin scoop of the grill. Weighs almost nothing, nothing is seen except the scoop, water cannot "climb" up the vertical distance and the car has not been hacked up. This scoop gets the coolest air possible and at highway speeds is subject to ram. I use the K & N drop in, and I did accomplish a port and polish of the plenum, lower intake and heads. To cut down on heat soaking at idle I added a heatshield blanket (aircraft pneumatic duct heatshield material) around the flex duct to the T/B, painted the air filter box in reflective chrome paint and added a spacer on the air filter box attach bolt to raise it further away from the exhaust manifold and to make it easier to attach the duct to the snorkel stub without hacking up the radiator support. I stand by my "argument" that not withstanding the air filter and possibly the snorkel inlet, that the air filter "box" is not in itself restricting intake air. Just remove/blend out any plastic "flashings" or defects in the inside. And don't forget that you can "ovalize" a round duct or pipe to some degree to go through a tight spot without decreasing it's crossection or area to any great degree.




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