Cobb cold air box for SRI

[Super Unique]

What's really funny is we spend all our time worrying about how cool we can keep the incoming air, and hypermilers worry about how they can heat the intake charge for better mileage

 

[gsxrnic]

I bought the COBB SRI because of the value and ease of install. Not sure how much difference there is between the a CAI and the SRI power wise. Just something else to throw into the debate. I haven't seen anyone mention anything about the ducting that goes to the battery box. That little duct is routed right off the main ducting that comes from the front grill and goes to your TMIC. I'm not sure what the effect to the battery would be, but if you disconnected the little piece of ducting that goes to the battery box it would vent almost directly on top of the COBB SRI. Any thoughts on this and what would be the adverse effects to the battery??

 

[FrequentFlyer]

The engine bay of this car gets damn hot. Probably the hottest car I've ever had. The battery is real close to the turbo. I don't know why they couldn't have shoe horned it somewhere else. Normally, batteries are up in the front corners of the engine bay. There is a reason why they put that ducting there because batteries don't like heat. How long will the battery last if you take that off? Who knows? Is it worth the extra power? Probably not. You could move the battery to the trunk somewhere.

 

[nhluhr]

SRI or CAI, it doesn't matter. Why? Simple. Once the air enters the intake it goes to the turbo where it gets compressed. When air gets compressed it gets hot. Much hotter than the ambient air temp. So, no matter what intake you have, the air will be the same exact temp once it is compressed by the turbo charger. The air is then cooled by the intercooler before entering the TB, and then the cylinders. If you want to lower intake temps get a larger intercooler on top, or even better a FMIC. That will make a difference.

This is just wrong. A turbo doesn't heat the air to some pre-set temperature, nor does an intercooler cool whatever it gets to exactly ambient. If you feed the turbo ambient air, it will get hot when compressed. If you feed the turbo hot air, it will get REALLY HOT when compressed. Likewise, an intercooler won't be able to cool the charge air all the way back down to ambient temp so the hotter air you feed it, the hotter air you get out of it.

Anyway, with that said, WRX/STI also have problems with really hot engine bays since there are two catalytic converters in the engine bay as well as the exhaust manifold being way longer so it releases a lot more heat into the engine bay. Beyond the obvious loss of charge density from increased temperatures, the ECU also is programmed to pull timing as the intake heats up to prevent detonation. Here is a stock table from the Subaru ECU that shows how much timing gets pulled for a given IAT:

As you can see, going from 120 to 140 you lose 6 degrees of timing. That is a LOT. A lot of people incorrectly think the sluggish response from their Subarus on hot days in stop-n-go traffic is due to the intercooler getting heatsoaked but it is MOSTLY due to the timing issue. This makes a bigger difference. (Note: Subarus do not have a temperature sensor after the intercooler... only in the MAF prior to the Turbo)

And here is how well Cobb's box for the Subarus works:

Highway Driving:

COBB Intake no box: Max 124 degrees F, Avg. 91.6 degrees F
COBB Intake with box: Max 108 degrees F, Avg. 74.9 degrees F
Difference of: Max ~16 degrees F, Avg. ~16.7 degees F

City Driving:

COBB Intake no box: Max 149 degrees F, Avg. 117.4 degrees F
COBB Intake with box: Max 111 degrees F, Avg. 87.5 degrees F
Difference of: Max ~38 degrees F, Avg. ~29.9 degrees F

Idle (~5 mins):

COBB Intake no box: Max 149 degrees F, Avg. 133.5 degrees F
COBB Intake with box: Max 113 degrees F, Avg. 99.2 degrees F
Difference of: Max ~36 degrees F, Avg. ~34.3 degrees F

Personally, I think the box will be well worth it not only for improved charge density but also for the ECU aspect.

 

[whitey4311]

Very nice post.

So much for all the ignorant posts about hot engine bay air not affecting anything, lol.

The funny part about all this is that if the CAI was priced less then the SRI all these cheerleaders would cheer for it and make reasons for its superiority. The point being that many who buy an item for some reason loose rationality just because they own and want to support it, go figure.

Now if Mazda would lift the stop sale on the CAI others could have the best product with no warranty hassle. I would honestly just get a other brand CAI and argue like crazy if they fought me on the warranty. I am just happy that my MS CAI is perfect and has given me no problems because I dont the stress of the dealer looking at after market items.

 

[MS3077]

What’s funny is I've never had a MS3 with a CAI actually out accelerate me and I've ran into quite a few MS3's. Not to brag or anything but it seems that I have better throttle response in comparison to those with a CAI. If there is a difference it's not noteworthy enough to justify buying a CAI and there are many other members that will contest to this. Once the car gets moving nothing else matters.

 

[MS3077]

Let's see 1/4 times, track times, etc.. I'm sick of hearing all this BS why don't you guys with the CAI's "prove" it gives you more power, etc. Race a MS3 with a SRI and see what happens.

 

[nhluhr]

I think shortrams tend to have much better throttle response just because it is a lot shorter column of air to have to accelerate when you open the throttle. There is so much less resistance in a shortram that it typically makes up for the loss you see because of the higher temperatures. That said, if you can make a shortram ALSO cold-air, then it is worthwhile.

 

[Betelgeuse]

Yeah you can think of it as trying to suck air from a really long straw. There will be some resistance. But cut the straw in half and things get a lot easier.

I will probably try the airbox just for the hell of it to see if my butt dyno notices any difference. But then we're back to that long straw again........

 

[SPEEDYHANS]

when can we buy this or the fmic

 

[dkswim]

rumor has it fmic next week sometime and the box they had a redezine to make simpler/cheeper for them to manufacture

 

[LaCroix08]

Dammit, I want it nowww!
Gimme gimme cobb

 

[Kain]

On other applications, typically how much more than just the SRI has Cobb charged for an SRI/box combo?

 

[nhluhr]

$125

 

[Super Unique]

If the $125 is right, it's a done deal for me. My Cobb SRI just got here and I installed it last night. Haven't done much driving on it, but I can already tell the noise annoys me. The performance is great, but that woosh needs to be toned down some. Fast and quiet is the best combination. If Cobb can deliver both while keeping the intake air cooler then they have a sale here.

 

[nhluhr]

Not sure how much it'll reduce the noise but that would be a benefit for me too. I had my whoosh noise with the subarus I owned and can do without it now.

 

[CoolWhip]

I just installed my SRI on Friday and I love the sound (thumb)

Might as well get the cold air box too.

 

[BoneyJive]

So what's the word on this? Is it out? Impressions? Sound? Performance?

 

[migueleitor]

hi

hello,

i'm thinking to install the COBB SRI; however,

1- when can i get the box that it mentioned here?
2- have anyone had any cel on with the cobb sri?

Thank you.

 

[nhluhr]

why do people keep asking here if the box is available? Why don't you call Cobb and ask?!