americanlt1

Would like some opinions on intercooler outlet size for my twin turbo Lt1 project. I will be using 2 1/2" inlets on each end at the bottom and a single outlet in the center of the top. The spearco core will flow 1050 cfm. For the time being I'll be using a 52mm throttle body. I have room for a 3 1/2" outlet but if 3" would be fine I would rather go with that.

Also, any suggestions on a clean way to couple the tubing to the throttle body?

nitrorocket

iTrader: (12)

The outlet should be as big as the 2 inlets which would put you at the 3.5" outlet. Why such big inlets? Is that the size on the turbos themselves?

americanlt1

The outlets from the compressor housings are about 2 1/8". I chose 2 1/2 based on input from a couple of intercooler manufacturers. They seem split on the size of the outlet though.

METAL MAN

I personally prefer to go big as possible for the outlet to eliminate any restriction on the turbos blowing in, plus 3.5" will match up allot nicer to your MAF & throttle body.

smokinHawk

iTrader: (48)

go 4" and get rid of your MAF.
but if you cant do that just use the 3.5"

americanlt1

I know I'm not the best at math, but when I compare the area of two 52mm bores with a 3" tube it appears to be more than enough area especially after you subtract the throttle shaft and butterflys. If I'm missing something I'd like to know because I'm no expert. This is my first turbo car and I'm seeking input to hopefully minimize the mistakes i know I'm going to make.

I couldn't go any larger than 3.5" and keep the tubing round, and I haven't seen any oval shaped tubing in 90 degree bends. I won't be using a maf sensor, but I'm still not sure how to tie the tubing into the throttle body. I dont want to use the rubber accordion unit like the one on Lt1 corvettes. Any suggestions?

smokinHawk

iTrader: (48)

if 3.5 is the biggest you can go, use that
simple enough

NoGo

iTrader: (2)

In order to equal the size of the two incomming pipes you will need a discharge pipe from the intercooler with a diameter of at least 3.53".

So it looks like 3.5" is the preferred outlet size.

nitrorocket

iTrader: (12)

If your turbo outlets are 2.25" I would use 2.25" tubing. That will easily support 1500 hp and be very efficient. Plus the tubing is cheaper and more compact. FWIW, I am using 2" with twin 60-1 hi-fi's. I have a 3.5" outlet with a 3.5" to 4" adaptor for the TB.

americanlt1

Thanks for the input guys. I agree with nitrorocket on tubing size. I don't see why the tubing would need to be that much larger than the compressor outlet. I havent fabricated my intercooler tanks yet, so I can do any size I want.

FastKat

iTrader: (10)

Think about this... as you collapse that 3.5" hose down to the oval on the LT1 throttle body you're going to loose flow area. Think about a circle.... it maxizes area (which determines the flow) when it is round. Start to pinch it into an oval and you will reduct the area... keep pinching it till it's almost flat, and then you have GREATLY reduced the flow area.

Moral of the story: Round objects flow more than oval objects with a fixed circumfrence (length of the outer perimiter of the object.)

nitrorocket

iTrader: (12)

When you make tubing oval shaped, as long as tube does not "dent" in the process, and the top and bottom are flat and not dished, with rouned sides, the area is the same. So basically, when you flatten the tube it will get wider also. This does not restrict flow. It will only restrict flow if the flat areas are concave.

FastKat

iTrader: (10)

Pretty sure that's not true... here are some examples:

Take a 4"x4" square (which is 16" around) and find the area... you multiply length x width to get 16sq inches. That's the area you have for your air to flow through.

Now make it a 3"x5" rectangle (which is still 16" around) and find the area... you mulitply the length x width to get 15sq inches. The flatter you make that rectangle, the less area you are left with... which in turn means the less air you can flow.

The same holds with cirlcles and ovals, however the math is a little more difficult.