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Shortening N/A Intake ***Font Sizing Needs Formatting***

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Shortening Air Intake





Shortening the air intake on a N/A S13 helps improve the responsiveness of the engine and gives it a bit more go. The pipe is shortened to where the stock battery location is and the battery is either relocated to the other side of the engine bay or to the boot.


This guide was written using an SR20DE from an S13. Other silvias and CA18's may have differen throttle body and afm sizes so check that before buying couplers




Materials: (I'd recomend using a 2.75" pipe, 2.75" straight coupler and a 2.5" to 2.75" coupler to keep throttle size continuity. The pics at the bottom are using a 3" pipe which is too big for the throttle body)


1 x 2.75" 90 Degree or 45 Degree Mild Steel Mandrel Bend (Local Exhaust Shop) For the new intake pipe. Pics soon at the bottom for differences, personal preference. You could also get a stainless bend from here. I chose mild steel as I painted it satin black to look stock. Exhaust pipe is best to use as it can be welded, the walls are nice and thick, it can withstand heat and its cheap and readily available. Try to avoid the bent "stainless" pipes from Supercheap / Autobarn. They are way too thin for this application and probably can't be welded.


1 x 2.75" Straight Silicone Joiner ($15, ASI_Performance on eBay) To join the intake pipe to the throttle body


1 x 2.75" to 2.5"Silicone Coupler ($15, ASI_Performance on eBay) To join from intake pipe to AFM


4 x Hose Clamps tosuit (3 x 2.75", 1 x 2.5") To clamp joiners


2 x 1.25 or 1.5m "Switch To Starter" Cables (ac-ebiz on eBay) To extend battery terminals / wires


3 x Metal Hose Fittings Only 1 is necessary that runs to the brake booster. Other 2 are for EGR and Crankcase. Take the hoses off and into an engineering shop to find the right size fittings


1 x 4m roll of Single Core Electrical Wire (Supercheap) To extend AFM wires


1 x Small Battery Tray (Supercheap) To install battery on original airbox side


1 x Pod Filter (3ARacing Pod from eBay) Speaks for itself


1 x Pod Filter Adapter (Supercheap) To adapt the AFM to a 3" pipe for the pod


2 x Battery Terminals (Ones with 2 bolts on the end that can clamp the cable in place. Auto One) For the new battery wires to connect to the battery


Electrical Tape









Start by removing the battery as well as the stock airbox, intake pipe and rubber throttle body pipe. You can then also remove the baffles that sit under the engine bay that connect to the stock air box on the right hand side.


To extend the battery wires (the way I did it), take the bolts right off from the stock terminals. Using a pair of pliers, separate where the stock terminal joins up. Bend it outof the way. Use a set of tin snips to cut the stock terminal so you are left with a small piece with a hole in it connected to the battery wire. Put the bolt back through this hole and put the starter to switch cable on the other side, as well as the other stock smaller wires that usually run to the original terminal. Bolt these all together with a washer on the starter to switch cableand tape over thoroughly. Do the same for the negative lead.


Alternatively, you could buy a small distribution block for 8 or 4 gauge wire made for 2 wires. (Can be more although not needed). Cut off the original positive terminal and strip the wire back a little bit and place it in one of the holes. Cut off the terminal on the positive extension wire and strip it back a bit. Put it in another hole of the distribution block. You have now joined the wires. This can also be done for the negative, but make sure they have their own distribution block!




Run these wires to the other side (where the air box originally was) wherever you want to run them through. I ran them out the front and along the radiator support. Once at the other end, clamp the wire into the new terminals. Label the positive wire byputting red tape on that wire.




To extend the AFM wires is pretty simple. Pull away the stock tape / cover on the wires and cut them 5 – 10cm away from the plug. MAKE SURE YOU LEAVE PLENTY OF WIRE TO STRIP AND JOIN ON THE PLUG SIDE! Strip the wires and join it onto a new piece that will run to the other side. Join it back at the plug and it's all done. Make sure to solder the wires. I ran them through the front and the rad supportagain. There is 3 wires for the AFM.




The mandrel bent pipe will be too long from the exhaust shop so you will need to angle grind it down to size. This will vary depending on where you want to position your pod. Do it bit by bit as it's easy to make the pipe shorter again but you cant extended it. Just keep shortening it until you are happy with how it sits mocked up with the pod and AFM on the end.




Depending on how many fittings you are using you will now have to find a spot for these. I just hooked up the brake booster line. I got mine welded for me as I don't have a welder. Get them (or you) to cut the base of the fitting so that it can angleout. Hard to explain but it makes the fitting face across the engine bay. I also cut about half the fitting off to stop the brake booster hose from kinking. For the brake booster hose, I pulled off the stock hose and cut off alittle bit from the short side (say 1 or 2cm) and a few cm (say 4 or 5) fromthe other side. Then put the hose on backwards to what it usually is and it should slide on the fitting without kinking if your fitting is in the same location as mine. Alternatively, buy some new hose that is flexible rather than bent such as the factory one and run it.




After welding the fitting on, you can paint the intake any colour. Use etch primer underneath then whatever colour on top. I used Satin Black from Supercheap to keep it semi - stock looking.




Screw down all the hose clamps and make sure the couplers are on and fit well.




To fit the battery tray on the other side, relocate the plugs that were under the factory airboxby pulling them off the mount and cable tying them out of the way. Then sit thebattery tray down and position where would be best. From here you can weld it on or screw it through the metal where the stock airbox baffles went as there is nothing else there to hit.




Connect up the batteryas normal, plug in the AFM and everything should be right to go!




You may notice that within the first week or so, the car may play up a little. This is most noticeable when driving and then putting the clutch in to slow down. The car may stutter and almost stall (or fully stall). All it needs is time. It usually only takes a week or so for the ECU to learn the new position of the AFM, depending how much you drive. The AFM has moved 1 - 1.5m closer to the throttle body and is now free from restrictions of the stock system so thats why it has to re-learn its position.




Drive it! Enjoy the new little boost in responsiveness and the awesome induction noise it brings!










This guide is taken from SkylinesAustralia.com by the user "WYTSKY". The original is here. I accept no credit for the guide, just copying in here as it's relevant to those who want to make a CAI for the shortened intake. If anyone does their own CAI or this one, please add it to this thread






The whole amount of the hardware you need only costs around $30 if you go to the right places.


I used:


$8- 90 degree intake pipe from a vn commodore in Pick Pay n Go

$4- flexible black funnel from Bunnings

$12- 6 pack hole saw bits up to 100mm from Bunnings (were meant for wood but they were so cheap and I only wanted to use them once)

$3- Rubber edge to cover up the bare hole from Clark Rubber-"Cool Clarky" if you please tongue.gif


All up = $27


The whole process only took me about an hour and you only need very basic tools.


Tools required:


Hack saw


Wire cutters/Tin snips

Maybe a flathead or phillips head to undo a few plastic screws on the underbody



The Steps:


1. Once you have found a Vn Commodore intake pipe, you will notice one side is longer then the other. I ended up cutting it down to about the same, so I could fit the funnel on it and just fit it all into the front bar.




2. Once the pipe can fit in under the front bar (keep testing to find the right size) you need to cut the funnel down to attach it onto the pipe. The funnel is used to attract more air in the direction of the pipe to flow straight to the pod. It probably isn't 100% neccesary, but for $4 who cares?


3. Use the hack saw again, cutting the funnel about halfway through, possibly with a little bias either way. The next step you want to do is measure how much you need to flare the inside of the funnel so it fits snuggly over the pipe. At the moment, the smallest part of the funnel should be able to fit inside the pipe, fit it in and see how much you need to flare the funnel.(It should be about a centimeter)


4. To flare the funnel you will probably need to make about 10 tabs with the hack saw around the smallest end of the funnel, each about 1cm deep. Once the tabs are made, grab a lighter and make the tabs just a tad warm which will make it a little easier to bend the flares with your fingers. The final result should make the small end look like a flower, which will then allow for the pipe to fit in.

To hold the pipe and the funnel together, use an adjustable hose clamp to tighten down the open flares over the pipe.




At this point your piping is now complete, it is optional if you want to use some fly wire to stop any bugs/leaves going up the pipe to your pod, I was not to worried about this because my pod is already a filter so I don't think it matters. You now need to make the hole in your engine bay.


5. Get your pack of hole saw bits, I used a 90mm size which fit very snug. Adjust where you want to place your hole, I decided to make it right in the middle under the pod. Attach the hole saw to your drill and start off very slowly. (From what other people had said I was weary of using hole saw bits that were made for wood, but they were a quater of the price of metal ones and I only planned to use them once.) After you have made the rough outline of where you want your hole start pushing down a little harder, then just keep holding it there, that way the teeth on the hole saw bit wont go blunt as quickly. I did it this way and it took me about 2 minutes before I could simply peal off the perfect circle like a metal can lid, plus I still have plenty use out of the hole







6. Once your hole is made you need to put the rubber edge on, and if you have it handy, spray some fish oil to stop rust(if you don't, don't stress, the rubber edge stays on nice and tight!) To get rubber the right length slowly cut it down in educated guesses, because it slips in deeper to the edge then you think and you end up needing more or have a part where the circle is not complete. I strongly recommend you use this rubber edging because it makes the hole look a lot more professional and hides any imperfections you may have made making the hole. ( in the pics the circle looks a little lop sided because the rubber had not been put on properly yet)




7. The final step to do is adjust the angle of the pipe a little, just so the funnel is pointed right in the center of the hole of the front bar and try to point the 90 degree pipe slightly down so dirt and water can't fly up as easily. I simply used a few hidden cable ties and found a few holes off which to angle them by.





Resized to 88% (was 800 x 600) - Click image to enlargeImage017.jpg













intake 2.jpg

intake 1.jpg

intake 3.jpg

intake 5.jpg

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nice, better than the one that i followed a while ago,


now make a box to go around it, with instructions so i can copy :P

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nice, better than the one that i followed a while ago,


now make a box to go around it, with instructions so i can copy :P


use your factory airbox. it fits in the corner well and the short sr afm would make it a piece of cake to hook up. I managed it with an rb25 afm and de airbox with a bit of effort.

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You can either ground the stock ground wire to the chassis and then a wire from the battery negative to the chassis too, but I extended both the battery wires to the terminals (so the negative was still stuck to the negative)/ It shouldn't matter, but I believe the stock ground is grounded directly to the engine block too? Not too sure but I thought that it would be best to take the stock route

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In the end I never did get a tune. The problems with stalling only stays that way for a few days to a week while your ECU learns the new position of the AFM. After about a week it runs as normal and doesn't ever bog down or stall when coming to a stop!


No idea on tuners in QLD sorry. Melbourne people can hit up Chequered Tuning who do NisTune supplied, installed, tuned and dyno'd for $850

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okay too easy a few of my mates have done short air intakes on there ca's and sr's and they havnt taken it for a tune so im guessing its all good thanks for that

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Thanks for the write up! next weekends project i say. Even if it doesnt make a huge difference in response or power, will be good to get that stupid long intake pipe out of the way:P

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