R34 Gtt Custom Air Box

[R34mac]

Hi guys,

For the past year I have run an Apexi pod filter in my R34 GTT, using a JJR shroud in an effort to seal it off from the engine bay heat. But I've never liked the shroud because it is not a perfect seal and would still allow a lot of engine bay heat in. I also hate the fact that it doesn't have a snorkel or some kind of duct feeding cool air to it - instead the air has to find its way through the small gap behind the headlight.

So I have decided to design a custom airbox which will be able to accommodate an Apexi pod filter and will be sized so that the stock airbox lid will clip onto it, and in turn allow the stock snorkel to slot in as well. I have come up with a design in CAD and have made a full scale model using thick cardboard to allow me to test fit - it still needs a few more small tweaks to get the AFM angle and position spot on before I consider making the final product. I am planning on using perspex but also considering aluminium and borrowing my friend's welder.

What are people's thoughts on this? Something which you guys would be interested in or not worth the effort?

I know there is a valid argument to simply sticking with the standard airbox and panel filter, but I'd miss the induction noise that you can only get with a pod. My time is free and the materials aren't exactly going to cost me very much. Thoughts?

[sonnyQ]

Would be very interested to see the outcome, as I am also looking for a cold air solution. I also run a pod and have been thinking about getting the JJR shroud but like you I think its a little counter productive without fresh air feeding into it. I just love the induction noise too much to go to a panel filter.

Let us know how you go and would like to see pics!

[GTSBoy]

Don't use perspex. It will stay nice and cool while the engine is running (because of the induction air going through it), but when you shut down a hot engine, the bay temps will rise and the perspex will get soggy and it will all go to crap.

[R34mac]

Don't use perspex. It will stay nice and cool while the engine is running (because of the induction air going through it), but when you shut down a hot engine, the bay temps will rise and the perspex will get soggy and it will all go to crap.

Alright, I've sent an email off to a local plastics company to see if they have a product available to suit. I am hoping for a thickness of 2 - 3mm max.

The design of the actual box is almost spot on now, just have to adjust the shape a little bit to get more clearance between it and the stock intercooler piping. It's still going to take time though - I still have to design brackets so it bolts up to the stock mounting holes, and try and source some clips.

I also have to buy a standard airbox and snorkel to check the airbox is sitting at the right height, to meet up with the lid. At the moment I am just working with accurate lid dimensions and a rough position for where the stock airbox usually sits.

Edited December 15, 2011 by R34mac

[J34]

I've been thinking about making something Custom for years. i've got a Apexi pod with the stock snorkel helping feed air in the direction of the pod but dont have anything other than that. It seems to go ok but fails when your not moving alot. I'm now thinking of going back to the stock airbox and use a highflow pannel filter. I've had my fun over ther years with induction noise but now im looking for something quiet that will still perform, the added bonus of one less thing to defect is a bonus as well.

Anyone know performance wise what the difference will be between the Apexi pod by itself and the stock airbox with snorkel and high flow panel filter?

[R34mac]

I've been thinking about making something Custom for years. i've got a Apexi pod with the stock snorkel helping feed air in the direction of the pod but dont have anything other than that. It seems to go ok but fails when your not moving alot. I'm now thinking of going back to the stock airbox and use a highflow pannel filter. I've had my fun over ther years with induction noise but now im looking for something quiet that will still perform, the added bonus of one less thing to defect is a bonus as well.

Anyone know performance wise what the difference will be between the Apexi pod by itself and the stock airbox with snorkel and high flow panel filter?

I've heard 5kW but in reality I think the difference would be negligible. Most people think running a pod makes a big difference but I bet it just feels faster because of the induction noise.

Basically I love the induction noise and I'm trying to come up with a stock looking setup that lets me run a pod which isn't sucking in hot air from the engine bay, or stuck behind some half-arsed shroud. The actual kW gains between it and a stock airbox & filter are irrelevant to me.

Edited December 15, 2011 by R34mac

[Godzilla34]

Hay guys i bought a k&n apollo kit (google) it, i gained 4KW aftera dyno run, works well. Entire Kit cost me $200.00 anyone interested in seeing some pics send me a pm with your number and i can txt u some pics, dont have any pics on my pc. So pretty much, remove the entire airbox from engine bay. Get a 3" afm adaptor from either autobarn or supercheap.

The kit comes with a duct kit, it than attachs to the adaptor, than i ran it through the bottom of the engine bay and mounted the pod filter box up in the passenger wheel guards and than has another peice of duct which i than brought out the front grill which gets its cold air from.

I would be happy to help anyone with their installation too if you choose to go down this path, it looks good and you can definitely feel an improvement from just having the old dodgy 3" pod filter sitting out in the engine bay receiving hot engine air.

[B-Boi34]

I have plans to get a carbon fiber cold airbox from JJR & a GTR snorkel & cut a slot in the box for the snorkel to fit into, I am yet to try this or measure anything up so still not 100% sure if it will but if it does it should work pretty well.

[SargeRX8]

I used perspex, it never went soggy. Good stuff and easy to work with. If you really want a tight seal from the engine bay you need to use some neutral silicone or something else to seal around the edges of the box facing the engine. Ill be making one once I know for sure that my intake pipe isn't going to be modified. I'll be using some aluminium checker plate which I will line the inside with something to deter heat. A full perspex box isn't a good idea. If anything, build it like a computer case, have a mostly metal frame with a piece of perspex in the top panel for looks.

[75coupe]

perspex, checkerplate, apollo kit, plastic shields.....

it all just sounds so tacky....

[gotRICE?]

Has anyone actually done any logging before and after temps with/without airboxes?

[krzysiu]

Stock airbox unless your running big power. Cant go wrong with that

[zebra]

Has anyone actually done any logging before and after temps with/without airboxes?

Don't be daft

People always do stuff like this and claim 100hp lol

[gotRICE?]

Haha.

Ive never seen the point in a cold airbox if you have a decent intercooler. The turbo is going to superheat the air regardless of how many degrees the intake is at the filter. Be it a couple of degrees cooler..

Sitting in traffic isnt going to do shit. The air moves so slowly through the pipework, even if it came in at -10'C it would still be 50+'C after a little while idling.

The second you give the engine some revs, and get the air moving the temps will plummet. airbox or not. Tried it a million times lol.

Try this too, get on the freeway, cruise at 100km/h and throw it in neutral. Watch the intake temps rise just as much as they do in traffic. If i remember ill even post a video of this over the weekend.

[SargeRX8]

Haha.

Ive never seen the point in a cold airbox if you have a decent intercooler. The turbo is going to superheat the air regardless of how many degrees the intake is at the filter. Be it a couple of degrees cooler..

Sitting in traffic isnt going to do shit. The air moves so slowly through the pipework, even if it came in at -10'C it would still be 50+'C after a little while idling.

The second you give the engine some revs, and get the air moving the temps will plummet. airbox or not. Tried it a million times lol.

Try this too, get on the freeway, cruise at 100km/h and throw it in neutral. Watch the intake temps rise just as much as they do in traffic. If i remember ill even post a video of this over the weekend.

I believe the boxes do jack shit. If you measure the temperature of your intake charge I am fairly sure it will be fairly warm to hot, as compressed air normally is. I really doubt shielding that bit of heat from the engine is going to make more than a bees dick of difference. But hey, it looks cool.

[R34mac]

Surely the point is to make the engine as efficient as possible? Haters gonna hate

Regardless, here's a screenshot of my design. I made a full size test version out of thin plastic and it sits comfortably in the engine bay and clears the stock intercooler pipes nicely. I can't really progress until I buy a stock airbox and make sure it sits in the exact same position, so the snorkel and lid line up with it perfectly. It is worth noting that I have designed it around an Apexi power intake so pod filters which are any bigger will most likely not fit.

I also plan on revising the design to minimise the amount of individual pieces it is constructed out of.

Edited December 16, 2011 by R34mac

[DVS JEZ]

Might be a good idea to sell cheapish pod filter and the box as a package. That way u know it will fit.

I like ur idea. Keeping things legal looking / devious is what its all about for a streetcar

[GTSBoy]

Ah, you see, here's the deal.  All those who are saying there is no benefit to a cold air intake if you have a good intercooler are missing one rather important point.  It's not how cold the air is that reaches you engine, it's how much of it there is.  And this is why a cold air intake is a good thing, even with a perfect intercooler.

Let's say that the air temperature outside the car is 25°C.  That air has a density of 1.18 kg/m3 at sea level.  If the air under the bonnet is say, 60°C, then it has density 1.06 kg/m3.  That makes the ratio of those two densities equal to 1.113.  ie, the cooler air is 11.3% more dense than the hot air.  You get 11.3% more air in every given volume.  Now, the maximum amount of air you can pull through the turbo inlet is limited by the sonic velocity.  Let's say you're at the limit (and this is what restrictors in competition classes are all about, so it does happen).  At 25°C, the speed of sound is 346 m/s.  At 60°C the speed of sound is 366m/s.  That's a ratio of 0.945.  ie, the cool air has a sonic velocity that is 94.5% of the hot air.  If you multiply our 2 ratios together, you get that at limiting flow, the turbo can ingest 1.113*0.945 = 5.2% more air mass.

That holds true at lower flow rates than the limit too.  Turbos are like most pumps (including the engine).  They breathe on a volumetric basis, but they do work (and consume power from the turbine) and give benefit to the engine on a mass basis.  Clearly it is in your best interests to give the coolest air to the turbo inlet.

And all this is before we even get to the question of pressure ratios.  For any given power level the engine must consume a certain mass of air.  If the air is less dense getting to the turbo inlet, then you have to pump it up to a higher pressure (and hence pressure ratio) to get the required amount of mass into the engine than if it arrived in a cooler, more dense state.  Higher pressure ratios are usually located at lower efficiency lines on a compressor map (for a well sized and matched turbo).  QED.

Edited December 16, 2011 by GTSBoy

[zebra]

Surely the point is to make the engine as efficient as possible? Haters gonna hate

Regardless, here's a screenshot of my design. I made a full size test version out of thin plastic and it sits comfortably in the engine bay and clears the stock intercooler pipes nicely. I can't really progress until I buy a stock airbox and make sure it sits in the exact same position, so the snorkel and lid line up with it perfectly. It is worth noting that I have designed it around an Apexi power intake so pod filters which are any bigger will most likely not fit.

I also plan on revising the design to minimise the amount of individual pieces it is constructed out of.

So all that effort for what is the same as a stock airbox???

[R34mac]

So all that effort for what is the same as a stock airbox???

No - all that effort for a stock looking airbox that is large enough to fit a pod.

Edited December 16, 2011 by R34mac