Gen 5 Cold air intake

Gen 5 Cold air intake

Postby decker » Fri May 28, 2021 9:08 am

Hey lads I've got a 2011 Gen 5 liberty gt and I was wondering if anyone with the same car has put a cold air intake on theirs before and if so could you please point me in the right direction in which parts I should use
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Re: Gen 5 Cold air intake

Postby Yowie » Sat May 29, 2021 7:53 am

I don't own a Gen 5 or know the engine bay layout at all, so this is is a generic set of comments.

1. Most aftermarket so-called "cold air intakes" are just pod filters in the engine bay replacing the factory air box. Some might put the filter in the guard, some might have some attempt at sealing the pod filter from hot engine bay air (not usually a good seal). Do you due diligence and use your brains before buying anything.

2. Drawing in hot engine bay air is bad for power due to reduced density and knock risk. The computer will pull timing to account for the increased knock risk of hot air. An intercooler cannot "mop-up" after an engine bay pod filter.

3. If the factory airbox has a reasonable source of air ducted from outside the car, that might be left alone, or perhaps mildly improved (sealed, de-burred, heat-insulated, whatever).

4. The factory airbox often has a hole in the bottom for a big plastic resonator. This is an opportunity to add a secondary feed to the factory airbox like I did ( viewtopic.php?f=10&t=36234&start=15 ). See the details in the thread, but it's a problem-solving exercise running the right sized silicone, aluminium or convoluted hose from the airbox to a reliable pickup point for cold air, ideally forward-facing for a mild ram-air effect. Convoluted hose will be the easiest way to route the incoming air through a complex series of bends. My alloy & silicone solution produced a box of unused pipe & hose sections until I got the combination right.

See also the plentiful articles on the Autospeed website for these types of projects.

5. Nay-sayers will warn you about ingesting water through the pickup point. I've been running this setup for a while. I did something similar for a VR commodore I used to own. The worst thing that ever happened with water was a saturated air filter (and reduced power) in the Commodore one night after driving on the freeway in torrential rain. No water was on the clean side of the air filter.

Enjoy the project.

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Re: Gen 5 Cold air intake

Postby LibertyTragic » Sun May 30, 2021 1:11 pm

I have been there and done that and my simple advice is don't bother. Not worth the cost for just gaining more induction noise (as fun as that is).

There are limited bolt on kits out there for the gen5 that has it all (filter, adapter, hose kit and a proper box surround). AVO turbo world sell a kit for the gen5, which I bought, but I don't recommend. AVO in general make pretty good quality gear, but the CAI product was not up to par, specifically the filter adapter was generic and was not a straight forward fit to the factory intake piping, fitting brackets were basic and were a struggle to get proper support and location and the box surround was low quality for the price and didn't fit together well.

Other options out there are taking bits and pieces from 2015+ WRX, which has a similar low mount turbo. Combine it with a WRX mishimoto air box hose kit and you can get it all to work. The hardest part is finding a box surround to suit. Others have just modified the WRX one.

For the AVO setup I had, it was functional, sounded great and intake air temps were not affected too much. On the intake temps, while driving, the difference between factory box and the AVO kit was not material based on my data logging. However, it definitely took longer to recover from TMIC heat soak if driving at low speed or idling for extended periods. Note even the factory setup suffers from TMIC heat soak at idle, which can't be avoided, but the max temp it reaches tends to be a bit lower on the factory as it doesn't get the double whammy of soak plus a hot intake.

So why did I rip it off? The tuning for the CAI/pod filter was a pain. Part of this I believe was due to the AVO adapter not having a flush seating on the inside for the MAF sensor affecting measurement. Even after a few revisions of the tune from my tuner, the low end, closed loop air flow range was always running super rich with the ECU correcting -8-10% in the LV. As a result the feel of the car when not wide open was not very linear, plus I wasn't happy with how much the ECU was needing to correct. If you had access to a dyno, you might be able to work through this, but your just spending $$$ and for no real extra power. With the factory box back on and reverting back to an e-tune built from a dyno and specific mods (i.e. less variables), the car is much better behaved and the tune is much healthier and safer.

So in summary, you will need to spend around $600-$800 for a CAI kit, plus $600-$1000 for a re-tune (mandatory unless you want to blow your engine). All this for a bit of extra noise - simply just not worth it. You would only go down this route if you are building an engine that will exceed the capability of the stock intake (300+whp), which is usually not the case for most people.
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