# Custom Intake



## glowsentra (May 27, 2003)

Ok i have been looking at AEM and Injen intakes, and i've decided that it's better to build a custom one then to spend 250-300 on one. My friend can build me one for around 60 bucks, but i was wondering how many horsepower a custom intake would add to my car. Right now it's a stock 91 sentra GA16 with a magnaflow exhaust (just muffler). If somebody has something similar and has dynoed their car perhaps? Thanks


My car


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## Harris (Nov 11, 2002)

CAI and WAI are going to give you a max of 6-8 hp and 3-5 hp, respectively, IMO. What you have to do when making a custom intake pipe is make sure you have uniform diameter and as few bends as possible. That's how all the AEM and Hotshots are made, IMO. I got an intake pipe from Ebay for my SE-R, and its pulls a lot better than the stock piece. Not a bad item, especially when I paid $48 shipped.


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## toolapcfan (Jul 10, 2002)

I still have my homemade CAI you could finish. The TB to MAF tube is what you'd need to finish and I have the piping for that, you just have to cut it and weld bungs in.


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## glowsentra (May 27, 2003)

Thanks. My friend is gettin the measurements as we speak. He has materials left over from his last intake, so it's not gonna cost me much  Oh yeah one quick thing, what is the intake diameter? I've been told anywhere from 2.25-3''.


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## Harris (Nov 11, 2002)

I can't remember off-hand, but make sure the diameter of the intake pipe is large enough to fit over the throttle-body.


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## toolapcfan (Jul 10, 2002)

2.5" is ideal for GA16's but people will tell you different. I'd just copy the diameter of what hothsot uses for their GA16 CAI.


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## glowsentra (May 27, 2003)

thanks guys, i'll let u know how it turns out soon


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## dho (May 15, 2002)

I made an intake for my B13 GA a while back. I read the Mathermotorsports write up on their custom intake. The best results that they had were from a 2.5" mid-pipe and a 3" for MAF/Filter. They also determined that the longer the 2.5" pipe, the more torque you will get. With my intake setup I took that into effect and... it worked! With stock tires on an automatic... I had a 3,300 stall... once I was off the line and accelerating, when the rpms got to 4500rpm's or so, I'd hear a little tire spin from the extra torque! Well... anyways, the pictures are below here and just so you know, I had to extend the MAF wiring:


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## the don 1600 (Dec 24, 2002)

okay so ....

1. all connections must be 2.5 to fit right.
2. need cupplers to connect.
3. longer mid pipe at 2.5 makes more torque.

question.

can i put breathers on all the connection hoses that go in to the mid pipe? so all i have is one pipe. because ive been wanting to do a cold air intake on my car also but i wasnt sure about that.


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## dho (May 15, 2002)

I'd recommend keeping all hoses. If you are worried about oil getting into the intake manifold, get a catch tank. Basically the engine runs better when it has the vaccum pressure that it was designed for and when you put the breather on the valve cover, you will make the engine run differently than designed. Also, you will dirty up your engine bay with oil, especially if you are running synthetic oil since it's able to get through cracks. Another thing, with a breather the oil will squirt out at higher rpms because of the oil moving around in the valve cover area. It's almost like having an oil cap off... but a lot smaller of an oil cap. Oh, one more thing, you might have issues with inspection if you use a breather. I'm not sure if it's definately going to change the readings but I'm sure it's like having a recirculating blow-off valve (read some information on that from not only on the NPM project 1.6 but in several other places) that just emits into the air. Hope this helps.

(2 hoses go to the intake pipe.. sometimes three depending on emissions equipment... valvecover ventilation / throttle body ( I think, it's been a while) / egr valve (really tiny 1/8" hose))


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## the don 1600 (Dec 24, 2002)

i only have two hoses. and nothing from emissions in my car. one of the hoses goes around the back of the engine. i still havent notice where it goes too. and the other one goes for the oil. i was thinking about an oil catch can but i dont know where i put it. i thought about welding it on to the intake but it seems like to much trouble. i thought about just leaving the rubber intake that the car comes with. and just extending it before the maf. moving the fuses that are next to the battery. so i can move the battery over or switch it so its horizontal. and put a filter between the battery and sidewall of the car. extending the maf all the way till the filter.

i just notice that u put ur battery sideways


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## dho (May 15, 2002)

the don 1600 said:


> *i thought about just leaving the rubber intake that the car comes with. and just extending it before the maf.
> 
> i just notice that u put ur battery sideways *


I'd try to keep the hoses after the MAF so that way if there is any oil going through the hoses, you won't damage the MAF. The MAF has a couple little wires on the inside that sense the temperature and how much air is going in. If oil gets on that it will be damaged or can cause damage.

Yeap, I used the factory tray and cut it by about 1 or 2 inches. Just play around with it. I used a total of 2 bolts to hold it down.


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## the don 1600 (Dec 24, 2002)

yea thats what i meant but i word it wrong. did u just cut the little side walls on the tray? how did u hold it down? cause if i turn mines side ways my battery tie down wont fit.


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## dho (May 15, 2002)

I think I chopped off 2 inches from the side that holds the fuses and relays. Next, I took one hole in the center and mounted it to the bracket that was already in the car. Finally, I took a bolt and nut and secured the rest of the tray on the right side (driver's) through a hole that the tray had. You may or may not have to drill a hole. Just play around with it... you'll find the spot for it. It should work, and by the way, when you cut the metal... make sure it's not sharp because it can cut into the battery. I'd recommend using the little plastic shield that the battery has underneath it.


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## the don 1600 (Dec 24, 2002)

how did u extend the maf? did u just cut the wires and extend. i just dont think it be all that smart to cut those wires since their so vidal for the car to function. but i think its the only way to do it since it be very difficult to do it any other way. i could go to a junk yard and get an old maf harness but than how do i connect the old one to the new one


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## Mr.Kouki (Aug 13, 2003)

I'd go with one of those cheap intakes on ebay, because, seriousley, what is the difference between an AEM steel pipe, and a no-name steel pipe? the only reason you're paying all that extra $$ for the AEM, is because of that damn C.A.R.B sticker..so unless you live in California, it would be pointless to get a 'big name' intake, when all you need is a uniform pipe and a good filter (that's where it's at btw). oh yeah, about this whole "how much hp will I gain with this intake" that kind of thinking needs to thrown out into the trash, imo. realistically, you probably won't gain very much hp, let alone feel it on the 'butt dyno' it's common for people to think that getting an intake will add 3-5 hp and then getting an exhaust will add another 7-8 hp, and adding a header will add an extra 4-5hp and so on...when in actuality, it DOESN'T work like that...there's a reason it's called and exhaust SYSTEM, intake, header,hi-flow cat,cat-back system, in reality with all these things working in sync, should give you somewhere around 10-14 hp gain... also, many people have the idea that a CAI gives you more hp, because it usese more dense air, when actually, that is only half of it...the tube length also plays a role in hp gain, because the longer the tube, the more velocity will build up as opposed to a sri...oh well, im going to sleep hope that helped...


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## dho (May 15, 2002)

the don 1600 - I cut one wire at a time and then got some shielded 16-20 guage wire and electrical tapped them together. I was afraid that the solder gun would get too hot for the electronics. You can electrical tape them as well as long as you make sure there is good contact and a very good seal. I sealed the points with a heat shrink wrap that was water proof. Try not to use very tiny wire because the voltage is important from the MAF. With a slightly larger wire than factory, you'll be very close to the original specs. Please keep in mind that electricity likes bigger wires in general to get the electricity to a further distance (depending on AC vs. DC). Also keep in mind that you don't need 3 ft of extra length. Take your MAF and put it in a place that it will be located for the completed intake. Next, you take your 16-18 gauge wire and you measure how much length you need to get the MAF extended with about an inch of slack on both sides plus a little in the middle for movement (if you make the wire taught, let it drop down by about an inch). Finally, make sure that all the electrical tape or heat shrink has a good seal w/o movement.

Hint: MAKE SURE THE CABLES ARE EXACTLY THE SAME LENGTH! It can hurt overall performance.... i.e. if one wire is 6inches longer than the other, it will send the computer a different measurement of resistance.

Mr.Kouki - I agree with you in a way. I can tell you that AEM does have a very good intake if they made it for the sentra... it's the V2. It utilizes thermal dynamic technology and engineering in making an intake that keeps an insulator of air to keep internal air temperatures down by a great amount. For example, their regular intake starts receiving heat from the engine bay after a while because the aluminum starts heating up (conductor). On their V2 intake, it basically adds a constant flow of air on the outside of the inner pipe to keep the air temps from increasing while the inner pipe performs like a normal intake. Another thing that helps their intake is the basic idea of using the vacuum from the intake to cool the intake pipe. Like I said before, the air is constantly circulating on the outside of the inner pipe (think of Air conditioning to the outside of a pipe) without affecting the intake performance (no negative effects because it is under vacuum) thus creating a very efficient intake that offers a double horsepower increase from an intake by reducing the temperatures. Some people say that if you reduce the intake charge (temperature) by 10 degrees, you get a 1% horsepower increase. On some of the intakes that the V2 was advertised for, they got an extra 10hp @ wheels (a total of 20hp @ wheels from a specially designed intake)!! I wouldn't be surprised if the intake temps were 100 degrees than a normal intake or cold air intake.

Another thing when making intakes that I found very interesting is the weight of the pipes. I wish there was a way to locate a manufacturer that made universal intake pipes that were made out of the same lightweight aluminum that companies like AEM and Injen make. Compared to the exhaust bends that I had to use, the aluminum vs aluminized steel piping for the same cold air intake design can have a 5-10lb difference in weight! The other factor is the use of mandrel bends. Like NPM told us on their exhaust articles, mandrel bends allow up to 30% more flow than normal crush bends. The same idea has to be used in designing an intake like Mr.Kouki said. Velocity is a very important thing in designing an intake. Another thing is what you design the intake for. If you were to make an intake for mid-high rpm power, you'd want a longer, gradual mandrel bent piping, TB matched piping, engineered for the desired RPM and CFM. For low-end power you'll want a very short pipe tuned to the desired rpm, large diameter pipe for larger amounts of instant air that's already filtered (helps when you just Punch the gas from a stop... V8's for example), and a cool intake charge... hard to accomplish while accomplishing a shorter pipe... sometimes good to have a hood scoop to help w/ temps. There are side effects of this design though, if you have an intake that is designed for a low end grunt, when you start getting in higher rpms you may have lost the velocity.

Below is a rough example of different CAI intake designs between different types of cars.. Honda vs. Nissan:
D16 SOHC VTEC vs. GA16DE
8000 redline vs. 6500 redline
Max HP @ very high RPMS vs. Max HP 500rpms away from redline
Max TQ @ very high RPMS vs. Max TQ in the middle-high rpm range (3500-4500rpms)
---A pop charger on a GA16DE will give a more wide-band range because it should increase torque at lower rpms better than a CAI but yet has a velocity stack to make up for the mid-high range. ** Several custom intakes utilize the HS CAI w/ POP charger in the fender well because of the useable power gains throughout all the powerband. (This is why I designed my intake like I did w/ pop charger.)

For the Honda, intake manufacturers like to use the 2" very.. very... very long intake pipe that sometimes equals to 5ft of piping! They use this to increase the flow near the peak rpm of the Honda whereas the nissan intakes have a median of power. After doing research on the HS design, they designed it for a very good mid-high range power gain which allows you to have more power throughout the useable powerband. Now which intake do you all think would be better for the street? Definately the HS type of design because it's used more. Every day we see and hear the bumble bee's hitting VTEC because they can't get the power when they need it. I can say that the VTEC does have benefits sometimes... good gas mileage until VTEC kicks in and then the engine starts working like it should all the time. I'm impressed with the VTEC head flow from the factory (Mainly Bseries vtec heads). I believe if Honda elimated the VTEC and just designed motors to flow well with the type of performance of VTEC without the switch over... they'd have decent street motors w/ torque. They should learn from the Nissan Engineers from the Nissan VVL w/ Turbo design.  High flow.. powerful motor... plus turbo!

I hope someone will learn a little bit from the information I just dished out. It took me several hours here on forums and doing research on the internet to learn what I have learned.

P.S. In the future I'd like to see more development of the GA16DE's variable timed intake cam. At different rpms the intake cam retards and advances itself at different rpms. JWT charges extra on the 1.6 ecu's to re-enable this feature from the factory if you were to get cams done. I believe that the VTC on the GA will produce something new in the N/A or even Forced induced world of the seldomly forgotten GA. It would be awesome if there was a way to utilize the flat power band (wide and useable powerband) for an all out street car. Finding a street car with enough torque at the bottom end and power all the way through the power band is hard to come by. The only two types of engines that offer this type of performance that I'm familiar with are the VVL's and the 3-Full stage VTEC motors (rare.. I think the only car it was debuted in was the NSX - 3 stage vtec... instead of no power at low rpms, they designed low, mid, and high cam lobe durations... no waiting till 4500rpm-6000rpm to wait for VTEC to kick in.. it's been already switched at 3,000 rpm and again at 5,500rpm).


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## Mr.Kouki (Aug 13, 2003)

dho-good info, im pretty tired (as usual) so I'll try and make this quick. as for the intake input that you have just told, there are many good points in that...but I'm here to talk more about VTEC, seeing how I also drive a B18c1 powered eg, anyways, VTEC was designed to get the best of both worlds out of the engine...true, many honda motors don't have that much low-end torque, but that's why VTEC was made...for the lower rpms say below 4100rpm, the low-end cams are used to make as much possible power they can at that rpm range, when the switchover takes place and the pins lock into the higher-lift free-moving VTEC cams, the power output is designed to make maximum power above 4100rpm...i personally think this is a good setup, because for daily driving, where going above 4100rpm isn't really necessary, gas can be saved as opposed to what you said in your last paragraph about the switch at 3,000 and then again at 5,500..but whatever, either way, i respect all cars and thier own kind of technology...

on a completly diff. note i hate being a newb because ppl dont take you serously and think you don't know sh!t unless you have 'x' amount of posts under your name, oh well, im going to sleep...


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## dho (May 15, 2002)

Hey now... be nice. I was not intending to insult anyone here. I don't really care how many posts you or anyone else have. It doesn't make you an expert if you've posted 1000 or 200, it's the information that you post. All the information that I post I've done the research on or I felt the information I was told was correct.

Regarding VTEC.......I did the research on VTEC. I know that it has it's benefits for saving gas money but I personally would perfer the 3 stage VTEC offered in the NSX over any other honda engine. Who likes to go through traffic, downshifting all the time to keep up with traffic? I would not like to have to down shift to 1st gear... engage VTEC for 2 seconds and then have to do it all over again putting more wear and tear on the motor. Not to start up anything but I've done several hours of research on the Honda engines because I was going to modify my 1990 Honda Civic hatch that I've already spent $2500 on the suspension. Anyways, you're telling me that the NSX does not have true 3 stages? Here's a link that states all the VTEC information I was talking about: http://www.performancesupply.com/vtecexpl.htm 



> First of all, despite being 16 valves, there is really only one cam lobe for operation in the first two stages. This is supplemented by the high lift center lobe (like in the normal DOHC VTEC). The second intake valve rocker, however, simply rides along a zero lift ring in place of the usual lobe on the cam shaft. To activate the second stage at 2500 rpm(both valves opening), oil pressure is diverted into a channel that drives a pin which connects intake valve rocker #1 with #2. Now, both intake valves are being operated in unison. This is perhaps not quite as ideal as a little valve stagger (as seen in the DOHC VTEC apps), but sufficient enough for good power.
> 
> To enter the third stage, at 6000 rpm, oil is now allowed into a second channel connecting all the rocker arms. This oil drives a pin which connects the linked #1 and #2 rockers to the center lobe actuated #3 rocker which is, of course, the high lift and duration mode.





> The high performance VTEC system, which made it's debut in the Acura NSX, is also available on the Integra GS-R, Prelude VTEC and del Sol VTEC as well as the 6th generation Civic Si.





> The VTEC system used in most Civics (EX, 5th Generation Si and the del Sol Si but NOT del Sol VTEC) is a little closer to that in the NSX, etc. The difference being that this system is vastly simplified and operates on the intake valves ONLY. The exhaust valves are actuated conventionally, which reduces the effect somewhat from the full VTEC system. This is partly to reduce costs, and partly because this engine is a SOHC, and the complex system of rocker arms to actuate sixteen valves is prohibitive to the full VTEC system. The VTEC on the Accord is close in design to that on the Civics as well, optimized more for a smooth power delivery then high horsepower.


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## dho (May 15, 2002)

For those of you who are interested, I found some information that I looked over about a year ago. Below is the information regarding a stock GA16DE head... information came from http://www.mathermotorsports.com/html/timmotor.html.


> The intake port of the standard head flows 102 cfm and the exhaust port flows 67 cfm.


This should help the people that are looking into more advanced intakes for the 1.6L. For modified heads, Mather motorsports got 115.5 cfm for the intake side (this information can be found at the Mather Motorsports website that I posted the link to above).


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## Mr.Kouki (Aug 13, 2003)

Don't get me wrong, that wasn't directed at you, for me being mad that im new to the board...anyways, what I've gotten from what you have posted so far, is that you want a motor to run like it was in VTEC, but at all times, correct? Now im unfamiliar with the NSX engine and how its 3-stage VTEC works, but I am somewhat familiar with how the new I-VTEC works on the DC5 and EP3 chasis'. so if all you wanted Honda to do was make a way to 'always be in VTEC' , then the I-VTEC is your answer...I know this is a Nissan board, so i'll make it quick.. ...
At low RPM's the cam timing is set in such a way that it reverts alot of exhaust gas back into the cylinder. This has an EGR effect and keeps emissions very low at normal driving RPMs. Then in the higher RPM's the cam timing can be set for performance....dont mis-interpret it, it doesn't push exhaust gas back into the cyliner there is just more overlap at low RPMs than there should be, so it sucks alot of the exhaust back into the chamber on the intake stroke...so to put it in terms for those reading who didn't understand a word i just said, here it is again in 'easier-to-understand' way...VTEC is the abbreviation for Variable Valve Timing and Lift Electronic Control.
i-VTEC stands for intelligent-VTEC . In addition to VTEC it has a variable valve opening overlap actuation mechanism , called VTC , as in Variable Timing Control for intake/exhaust valves overlap and NOT ignition timing control. This mechanism which is between the cam sprocket and the camshafts varies the overlap between the intake and exhaust valves according to engine load...so basically, Honda has got it down now to the point where they can run vtec-like performance at any rpm, whether low or high...for more information on this, here is a more in-depth look at I-vtec and all the ins and outs about it http://asia.vtec.net/article/k20a/index.html ....now b4 everyone gets confused at to why i wrote this, I own a Honda as well as a 240, i love both cars and both manufactuers...so there.


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## dho (May 15, 2002)

That's cool. I haven't done very much research on the new i-VTEC or the toyota's VVTL. I'm used to looking at older motors. So Honda took the best of all three worlds by using the idea that Nissan used on the GA16DE. The GA16DE has the VTC. They differ in their own ways but they both work the intake cam. That's why the GA has a very good useable powerband. One of the things that I found that was ironic is that JWT charges extra for a JWT ECU upgrade for the GA16DE plus an extra charge to keep the VTC enabled with JWT cams or just a regular ECU upgrade. I believe if it wasn't for the VTC on the GA that it would not be better for torque than a d-series DOHC 1.5 or 1.6 non-vtec motor.

Anyways, designing an intake for each one of these motors would take a little time designing. It's best to get a dyno of the engine you are trying to modify and then figure out the goals. Isn't it funny how you can go through the same decision making process when you build a performance motor and when you do headwork? By the way, one of the extra tricks that nissan used for the GA to produce more torque is the TB size and intake runner design that they used. It's not every day that you see a 110hp 1.6L motor that boasts 108lb tq with a 48mm throttle body that goes to long intake runners.

Well, I'm going to bed. I've been up for almost 20+ hours. If I put any information here that is not correct, please email me with the correct information.


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