Right now i've just got a cheap ebay CAI and it's inside diameter is only 2.25". I was wondering, if i got an ITR CAI which is 3", would i see any performance gains over my current intake?

 

also interested

 

i dont know for sure, but i know theres something to be said for inake velocity and with that larger piping you'll loose that. Also i'm sure AEM has done lots of reasearch and have made them different diameters for a reason. It would probably only bennefit you if you had some heavy mods.

 

I have been curious about the same thing.

The calculated "best" intake diameter is 25% more than your throttle body bore.

For an LS it comes out to be about 2.56". Most AEM CAI's are 2.5", which is pretty close.

I am thinking that any larger than that, the throttlebody and IM are not going to be able to take advantage of the extra air coming towards it to warrent anything bigger.

I did pick up a cheap-o 3" shortram to test on a dyno when I go though, I will post the results. (compaired to my 2.5" cai)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StyleTEG &raquo;</TD></TR><TR><TD CLASS="quote">I have been curious about the same thing.

The calculated "best" intake diameter is 25% more than your throttle body bore.

For an LS it comes out to be about 2.56". Most AEM CAI's are 2.5", which is pretty close.

I am thinking that any larger than that, the throttlebody and IM are not going to be able to take advantage of the extra air coming towards it to warrent anything bigger.

I did pick up a cheap-o 3" shortram to test on a dyno when I go though, I will post the results. (compaired to my 2.5" cai)</TD></TR></TABLE>
well that would only be the case if it was FI, casue the intake only gives as much air as the engine sucks, supposedly the reason the CAI is so effective is because of the air pattern in the piping, so the only reason you would need to get bigger piping is if you had a larger bore or serious headwork wich mean that the engine wanted more air and the small piping couldnt deliver.

 

yes the CAI powerband is different due to the length of the pipe. The longer the pipe, the faster the intake velocity is (with in reason). This causes volumetric effeciencey to happen earlier, which results in the famous "AEM Hump".

I have dyno graphs showing the difference between the same diameter shortram and CAI having EXACT same performance except for the AEM hump. Supposidly, when you get into bigger NA the shortram reaches volumetric effeciency later so you get that hump higher and in your powerband.

But that doesn't mean that you can't benifit from a larger pipe on an LS. Which is what I am looking to find out at this point.

By going to a larger pipe you are sacrificing intake velocity for intake quanitity. Which the determining factor would be is 2.5" intake piping any bottleneck what so ever in the quantity of air on a relatively stock B18B?

 

Basically what i'm wondering is, since i have 2.25" CAI piping now, if/when i upgrade, should i get the 2.5" or just go w/the 3" piping?

 

The calculated best intake diameter is based on your TB bore. It should be 25% bigger than the TB.

The correct TB size is determined by your intake manifold.

So if you have stock of both of those, stick with 2.5".

 

aem im sure spends enough money on r&D so what ever they sell you is what they were able to produce the best hp with. but on the other hand they also in most cases test there products on stock cars with no mods so having other mods may call for a little larger piping so i guess i just contridicted my self. this may or may not help

 

As I stated earlier, you want the intake piping to be 25% larger than the TB bore. So AEM's R&D was correct in using 2.5" piping (which is about 25% larger than the LS tb bore, 58mm).

But once you start getting into serious breathing modifications that result in a different IM and TB for your engine package, you need a larger intake piping to work with that system.

 

Whatever you do... dont slap the tornado on it