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So I had the cobb short ram intake on my Stage II 2005 STI, and recently went to the Injen CAI which I got on sale from Ptuning. I don't know if it is just my mind, but I definitely feel more power, especially in the higher end where it used to just fade. I idle at about 500 rpm but sometimes it dips to 400 and sounds like it is going to stall but doesn't. What could I do to fix this?

* I had a reflash tune done by Jeff w/ the Cobb on.

I don't know what the cross-section difference on the maf tube is between those two intakes, but there is a possibility that the Injen is slightly larger, causing you to run a bit lean. This may account for any power gains, and the rough idle.

IIRC Colin had the Injen intake, or was it the FMIC?

If you had a cable throttle, you could back the idle screw out a bit and raise the speed, but you have the electronic throttle body.

If you want the crappy "everybody will laugh at you" zak fix, clean the MAF sensor, and cover the lower half of the filter. This will encourage more air to enter the top half of the tube where the sensor is and maybe richen up the AFR to get the idle better.

A long shot, but who knows...

This has always been an issue w/ most aftermarket CAI. The main problem being the location of where the MAF sensor is mounted. Usually being right after a curve causing air on one side of the sensor to be denser than the air on the other side which throws the voltage off. I noticed that when I went from a WBR CAI intake (which is plagued by the bad location of the MAF and caused erratic idle) to the COBB shorty intake, the idle went back to stock smoothness. I used the WBR intake only b/c it came w/ my WBR FMIC kit and I didn't have an alternative at the time. I was happy to remove it. I would recommend a re-tune if you intend to keep it. Nothing beats the stock intake in my mind unless you are running 600HP+.

sirwilliam wrote:This has always been an issue w/ most aftermarket CAI. The main problem being the location of where the MAF sensor is mounted. Usually being right after a curve causing air on one side of the sensor to be denser than the air on the other side which throws the voltage off. I noticed that when I went from a WBR CAI intake (which is plagued by the bad location of the MAF and caused erratic idle) to the COBB shorty intake, the idle went back to stock smoothness. I used the WBR intake only b/c it came w/ my WBR FMIC kit and I didn't have an alternative at the time. I was happy to remove it. I would recommend a re-tune if you intend to keep it. Nothing beats the stock intake in my mind unless you are running 600HP+.

That pretty much sums it up. I had an Injen CAI on my WRX and it would sometime cause a rough idle. Especially during the hotter months. There really are only two times you need to replace your stock airbox: If you're running a FMIC, or if you're making ~600awhp.

(I'd put off using one unless you really feel compelled to. )

Would an SPT high-flow intake fit the bill or would that also contribute to wonky MAF readings? Or would it not give much of an improvement?

--Alan

remove the intake snorkus and drop a K&N into the factory airbox. 99% of the gains, 0% of the issues.

Mr Kleen wrote:remove the intake snorkus and drop a K&N into the factory airbox. 99% of the gains, 0% of the issues.

We have a winnAr!!

Yeah I figured. Nobody seemed to mention that when I was looking for parts I could go back to teh Cobb shorty but the CAI definitely seems to provide a better power band. I would also go back to stock however.... I'd have to call my trash company

I will be getting a tune once I receive my turbo, injectors, and fuel pump from gruppe-s. ( Also have an SSA TMIC )

Sorry I'm a bit late to the party here folks but I have to agree with everything being said. The Injen CAI has been shown to make gains (especialy up top) due to it's design leading to leaner A/F ratios. I've seen logs that prove it. If I was starting from scratch, the SPT, Cobb and K&N Typhon are the only short-ram intakes I would consider. They all make gains over the stock intake and none alter the AFRs. The only CAI I would consider is the Buschur Racing as it has shown to not run leaner AFRs over stock yet still make excellent gains.

If you want to use the Injen CAI I would highly recomend a few logging runs be made to make sure your not running lean up-top. Trust me, the last place you want to run lean is at 6,000-7,000 RPMs. I'm not saying you should not run the Injen CAI. If you get tuned with it on you are likely to have gains over the stock air box or even the Cobb, SPT or even the K&N Typhoon. CAIs really do work. I'm not a big fan of them as i don't feel the risks and hassle are worth the exra hand-full of power they deliver over a decent short-ram, but they do work.

Roger that. Anyone with a tacitrix cable and laptop going to be a meet soon?

I have a Tactrix Cable but no laptop.
That laptop would also need to have ECUexporer or LogWorks or some other data logging software.

In theory I can use my mac laptop with vmware fusion. ( It supports USB/USB2 passthrough to the guest OS )

If vmware allows you to graph your data as a log and view it than yes it might work. Hopefully, you won't have a problem with the tactrix cable, supposedly many older laptops do.

Both programs downoaded and installed. I will bring laptop. Also installed Enginuity for kicks.

drwrx wrote:The only CAI I would consider is the Buschur Racing as it has shown to not run leaner AFRs over stock yet still make excellent gains.

Hmm, I have not heard anything on the bushur one. Will have to check that out. I have heard that the APS 65mm and the Prodrive CAI do a pretty good job keeping it stock like but I have seen any hard data to prove it. Yeah, I agree to just yank the stock snorkus and grab a new panel filter.

My friend actually modified the snorkus to get it more like CAI. Also, my buddy Peaty has hard data that removing the snorkus and using the RS OEM Fender Plug causes more heat vs. not having the fender plug. Just FYI.

sirwilliam wrote: Also, my buddy Peaty has hard data that removing the snorkus and using the RS OEM Fender Plug causes more heat vs. not having the fender plug. Just FYI.

who is Peaty and where is his hard data posted for review? inquiring minds want to know...

Mr Kleen wrote:

sirwilliam wrote: Also, my buddy Peaty has hard data that removing the snorkus and using the RS OEM Fender Plug causes more heat vs. not having the fender plug. Just FYI.

who is Peaty and where is his hard data posted for review? inquiring minds want to know...

Peaty is a good guy and he is everywhere subies are but you can find a lot of his hard data on:

www.scoobymods.com

And I know everyone has heard of that site I sent him a PM to find the exact location of that info. I know it was posted up on the SF.org site but can't remember where.

sirwilliam wrote:

Mr Kleen wrote:

sirwilliam wrote:Peaty is a good guy and he is everywhere subies are.

I was wondering if that was the Peaty you were refering to. I can also vouche for his knowledge and the quality of his research. He knows his stuff, and I would trust any of his findings.

so are you still running that CAI?