Hotrodnova66

I'm wondering what size tube everyone is running for their cold air intake system on an ls2 or similar motor with dbw throttle body. My harness instructions told me to use 4" but it never idled, idles around 1600rpm. Tonight I reduced my existing 4" intake and put a 3" pipe at the end and it idled better than it ever has. Wondering if the volume of air in a 4" tube is too much and causing a false reading??? Thanks

1989GTA

I have an L92 and I am using a 4" tube. Also using a DBW throttle body. Not sure what is happening with your setup.

superdave84

I have a 4" tube for my LS2. One end fits perfectly on the TB, but the MAF is smaller than 4" by a little bit. I ended up cutting an extra silicone coupler I had, slitting it and cutting a little bit out so that its circumference was a little less than 4". I put it around the MAF, and it serves as a spacer. I then used a silicone coupler and clamps on top of it like you normally would.

I imagine if you had air slipping in around the MAF you might get an inconsistent idle. Not sure what's going on though

Hotrodnova66

I should of mentioned my engine harness came with the ls7 maf sensor which is the card style. Not too sure this is my problem but putting a piece of 3" before the maf helped the idle, will try to mock up a whole 3" intake and see what it does. Thanks for the replies

1989GTA

Mine also has the card style MAF sensor.

fieroguru

iTrader: (1)

I have a 4" intake with LS7 MAF feeding a LS2 intake/90mm DBW TB on a 5.3L. The 4" tube has a honeycomb air straightener, but it idles at 800 rpm with a 224/232 camshaft.

Hotrodnova66

It's not my intake size, tried 3" today and didn't like that at all. We'll back to square one with this thing. Thanks for the input everyone helped with this situation.

1970camaroRS

iTrader: (8)

Not sure how your intake tube size would be much of a variable in idle. Sure, you should run the correct diameter if you're using a LS7 card style MAF, but even if that's sized wrong it should alter your idle too much. With your idle being so far off, I would look at the IAC valve, that the throttle is closed properly and that the tune is correct.

All that said, I have 4" the the TB, reduced to 3.5" for the rest of the run because I'm running a stock LQ4 truck MAF and intake.

pdsq98gt

I think you need a custom tune. Especially since you have a card style maf on a custom cai system. Even if you use an older maf that is the whole housing, they're still off a little depending on the cai setup.