im building my coldair intake out of mandrel piping, silicon clamps, and i was planing on taking the MA sensor and pluging it directly into the piping. do you think its a bad idea to take the sensor out of the stock medal part(i dont know what it is called) and also plugging the o2 sensor into the piping aswell.

if you were wondering where the cold air is coming from well get ready. i remounted the battery towards the engine a few inches then where the stock resinator was located in that hole by the wheelwell, well i cut a 3.5 in diameter hole and dropping the piping through that and made slits in the front bumper where the fake vents are located. idea seems perfect but im worried about the sensors. any help please?
ps i'll post pictures when its done

matt 96 g20

What do you mean O2 sensor, shouldn't that be in the exhaust?:confused:

You shouldn't take the mass air flow sensor out of the housing, it will not function properly it's designed to work with an exact sized opening. If you change that opening size, you will change the air-fuel ratio, in this case making it run EXTREMELY lean, not a good thing. If you are going to make a custom CAI, incorporate the MAF unit into the piping by cutting a piece out of the piping, where you can use silicon hoses and clamps to hold the MAF in place. The only thing you may need to mount to the CAI is the air temp sensor, but that's relatively easy, just 3 holes, 2 for the bolts, 1 for the sensor itself (i had to do this to my HS CAI when i got it about 2.5 years ago).
Also, I've heard that some people have been having better luck moving the MAF unit as close to the filter as possible, rather than closer to the TB in the intake piping. If you're doing all the piping by hand, maybe try and incorporate the MAF as far away from the TB as the MAF harness will allow.

Hope this helps

Originally posted by JustinP10
Also, I've heard that some people have been having better luck moving the MAF unit as close to the filter as possible, rather than closer to the TB in the intake piping. If you're doing all the piping by hand, maybe try and incorporate the MAF as far away from the TB as the MAF harness will allow.

Hope this helps
what will moving the MAF farther do? how will it change the performance?

Originally posted by B13 Rob P10

what will moving the MAF farther do? how will it change the performance?

I've heard it's gains a hp or two, i'm not sure if that's by shifting the power curve higher up, or just an increase in overall power. I'm guessing the earlier of the two. I unfortunately do not have any dyno graphs to back this up right now though. Sorry.

do you know what causes the increase in power?

Why not just go out and buy an intake so you can save all this trouble and know your car will be reliable.

Originally posted by B13 Rob P10
do you know what causes the increase in power?

I don't know the exact reason, but my guess would be resonance tuning, as that's where most of what the gains come from with a CAI.

What kind of intake system do you have my g20t has a stillen intake and I am proud.

You ever think of just making your own pop charger with a heat shield? That could work as well as a CAI IMO.

I would think that having your MAF sensor further away from the engine would be bad. Lengthening the tube allows the air to have a more laminar flow before it reaches the MAF sensor. This would seem to be ideal. Moving the MAF further away from the engine (closer to the filter/opening) puts it in the more turbulent air. I would think that doing this would give you LESS power, not more. I'd have to see some dyno numbers to confirm that moving it further away gives more power before i'd believe it.

Originally posted by fuzzynaval
You ever think of just making your own pop charger with a heat shield? That could work as well as a CAI IMO.

Heat shield would be pointless. I've run a series of tests (involving scattering thermocouples around the engine bay and driving round and round...) and that area of the engine bay where the pod filter would sit is so close to ambient temperature it's not funny. Anyways, the advantage of a CAI is not so much the cool air but the resonate supercharging effect.

Originally posted by 2002G20Racer
Why not just go out and buy an intake so you can save all this trouble and know your car will be reliable.

CAI prices are kinda ridiculous when you consider that you're only paying for a fairly simple length of pipe....

Originally posted by B13 Rob P10

what will moving the MAF farther do? how will it change the performance? Since the MAF is a restriction in a 3" CAI pipe, it will tend to reflect some of the pulse energy reaching it, and cause a little interference with the resonance of the pipe.

Moving the MAF further away increases the resonant length of the CAI between MAF and throttle. I'm guessing this lowers the resonant frequency of the pipe and lessens the pulse interference at the throttle plate end. It may get 1-3 hp below 4000rpm on a stock engine based on the quote below.

I think the following was written by Mike Kojima (correct me if I'm wrong) where he fitted a larger MAF which would have a similar effect:

"I also tested using a big 80mm MAF from a late model Maxima using a custom programmed JWT ECU. My engine is getting close to the point where it can top out the stock ECU but not quite yet. Even through the Maxima unit is nearly 45mm larger than the tiny stock MAF, I did not gain any power except for about 2-3 below 4000 rpm! My theory on this is that the larger hole helped the CAI resonate better at lower rpm. I don't think bigger or bored out MAF's like Stillen sells are worth it unless you are turboed or your engines are modified to the point where they can pull more than 5.15 volts on the airflow meter. This is the point where the stock MAF is maxed out."

Originally posted by jasestu
CAI prices are kinda ridiculous when you consider that you're only paying for a fairly simple length of pipe....
True, but when you add in the mandrel bends, welding for all the inlet tubing, and the finishing (chrome or otherwise). Thats one chunk of change if you are doing just one, thats not even including labor. Hell, just for the simplicity of the install, its worth the money. All in all, if you build one that matches an aftermarket one, youll probably pass the price. If you go ghetto, Im sure youll come out ahead...just my two cents...

Originally posted by Yahnozha

True, but when you add in the mandrel bends, welding for all the inlet tubing, and the finishing (chrome or otherwise). Thats one chunk of change if you are doing just one, thats not even including labor. Hell, just for the simplicity of the install, its worth the money. All in all, if you build one that matches an aftermarket one, youll probably pass the price. If you go ghetto, Im sure youll come out ahead...just my two cents...

Pat, you hit it on the head. It could be done cheaper, I'm sure, but probably not enough so to make it worth it. If you had the tubing on hand, that would be different. If you can't do your own welding, you can probably expect that to cost you more than a few bucks. I tack welded my IC pipes and had a professional do the real welds. That cost me about $80.

Don't forget there are three little pipes that must be added to the CAI for vacuum and other fittings as well.

If you guys think the Nissan stuff is expensive, buy a Porsche. I'm planning on making several things for it because I can make, or have made, several things for less like spherical bearing cassettes (replaces the suspension bushings) and even swaybars. Swaybars for the damned car run $800-1,300!

Originally posted by Yahnozha

True, but when you add in the mandrel bends, welding for all the inlet tubing, and the finishing (chrome or otherwise). Thats one chunk of change if you are doing just one, thats not even including labor. Hell, just for the simplicity of the install, its worth the money. All in all, if you build one that matches an aftermarket one, youll probably pass the price. If you go ghetto, Im sure youll come out ahead...just my two cents...

No sence in me trying to convince you otherwise until I've done it, so if I do get around to doing it I'll document the whole process and then compare costs.

But just for interests sake...

Mandrel Bends - S.S. tubing from work (dairy factory), free.
Welding - What needs welding? Anyways, Dad's an A grade mechanic, free.
Finishing - Good friends own an electroplating company, free

Aside from that it's an interesting little project. Also gives you the option of positioning the filter in alternative locations...

Originally posted by Geo


I tack welded my IC pipes and had a professional do the real welds. That cost me about $80.

Don't forget there are three little pipes that must be added to the CAI for vacuum and other fittings as well.


Ahhh, that welding. :)

Originally posted by jasestu
No sence in me trying to convince you otherwise until I've done it
I havent asked you to convince me, Im just pointing out some of the stuff youll need to do one.


Originally posted by jasestu
But just for interests sake...Mandrel Bends - S.S. tubing from work (dairy factory), free. Welding - What needs welding? Anyways, Dad's an A grade mechanic, free. Finishing - Good friends own an electroplating company, free
Cool...Its always nice to have resources...mine is an almost fully equiped machine shop...www.customsteel.com (under the facility section)


Originally posted by jasestu
Ahhh, that welding.
Yeah, this welding...
http://www.customsteel.com/2001/G20/CAI.jpg
Keep in mind thats a 3" piece of tube for the first section of the CAI, take a look at the little tube on the right, its maybe 3/16" of an inch OD. Have fun welding that one...

Not trying to bag on your attempt, I am always supportive of others that can do things differently, better, cheaper.


Originally posted by jasestu
CAI prices are kinda ridiculous when you consider that you're only paying for a fairly simple length of pipe....
I was just commenting on the fact that a CAI is not a simple piece of tubing that is priced at $200, there is work involved to manufacture these things and companys like to make a profit....

So do us a favor and give us a comparison on what you are able to do including all the free stuff, and try to get the pricing on what all these free goodies would cost if you had to pay for them. Most people dont have those kind of resources...

Originally posted by Yahnozha
Keep in mind thats a 3" piece of tube for the first section of the CAI, take a look at the little tube on the right, its maybe 3/16" of an inch OD. Have fun welding that one...

Just drill a hole, weld a nut or socket fitting over it and screw a 3/16" OD hose fitting into the nut or socket ..... what's so hard about that? :crosseyed

just got the cai done but have a prob, the vac hose that goes to the tb not the engine one, well i put a breather on it, why wont my car stay on,and whats the difference if i have a breather on it or if its connected to the piping itself?

Originally posted by jasestu
Heat shield would be pointless. I've run a series of tests (involving scattering thermocouples around the engine bay and driving round and round...) and that area of the engine bay where the pod filter would sit is so close to ambient temperature it's not funny.

You know, it's so cool when people do things like this.

FWIW, Lew Shadoff on the SE-R list has software and a link that allows him to read anything the ECU reads. He found the same thing. Also, some folks on the Rennlist 944 list have also hooked up thermocouples and found the same thing. The data is speaks strongly.

Originally posted by mcguiver7
just got the cai done but have a prob, the vac hose that goes to the tb not the engine one, well i put a breather on it, why wont my car stay on,and whats the difference if i have a breather on it or if its connected to the piping itself?

Unless I've misread, you're sucking in unmetered air.

Originally posted by Geo


You know, it's so cool when people do things like this.

FWIW, Lew Shadoff on the SE-R list has software and a link that allows him to read anything the ECU reads. He found the same thing. Also, some folks on the Rennlist 944 list have also hooked up thermocouples and found the same thing. The data is speaks strongly.

You know I've been meaning to do the same thing, i wanted to get a couple measurements for testing, one of ambient air (say in front of where the fog light would be) on where the filter is at (in the CAI setup) and on in the intake piping right near the TB (as close as possible to the temp of the air entering the motor). It'd be interesting to see what type of temps there are when it's 110 outside :surprised
Any suggestions on where to go for the sensors/thermometers...? Thanks

Originally posted by JustinP10


You know I've been meaning to do the same thing, i wanted to get a couple measurements for testing, one of ambient air (say in front of where the fog light would be) on where the filter is at (in the CAI setup) and on in the intake piping right near the TB (as close as possible to the temp of the air entering the motor). It'd be interesting to see what type of temps there are when it's 110 outside :surprised
Any suggestions on where to go for the sensors/thermometers...? Thanks

I hooked a data-logger up to 3 thermocouples - one behind the front number plate (ambient) one where a typically pod filter would sit (by the stock airbox) and one over towards the VC. But bugger it I can't seem to find the raw data, I think I've lost it between PC's...

But I did just find the original post of mine on AF:

===
After some discussions (G20>Maintainence>Howdee), and for my own curiosity, I've taken a few temperature readings...

The results are an average of 10 readings taken at 1 minute intervals driving at open road speeds (100km/h 60mph). There was no aftermarket system to get air up to the location of the intake (where the stock air box is located). The data needs adjusting for the thermocouple calibration, but the difference is only about 0.4C and I can't be bothered doing it. The engine is a SR20DE in a 92 Primera Te. Error values are 1 standard deviation.

Ambient (taken from behind the front bumper)
--- 20.5 +/- 0.3C (69F)

Engine Bay (taken down the left hand side of the engine, I guess I should get a pic of this or describe it more accuratly)
--- 40.6 +/- 1.7C (105F)

Intake
--- 31.3 +/- 1.9C (88F)

Feel free to hit me up with any questions...
===

Oh. :0 Turns out the difference from ambient to intake is a tad more than I thought. Still significantly cooler than other regions of the engine bay.

Must caution you tho - this data is only from one set of trials on one day. Anyone with a scientific background should realise the limitations of this.