I am going to be turboing my lsj soon and just wondering what size piping would be the best?
Im gonna have

s256et
ported and polished head
darton sleeves
diamond pistons
78lbs valve springs
and all the turbo bolt ons....

Any recommendations?

 

2.5 inch hot side. 3 inch cold side

 

Everything 2.5".
Only use a 3" MAF section if your MAF is shitting itself due to max frequency.

 

2.5 is the norm.

 

you need a full 3 inch cold side. if you only use a 3 inch maf section it will cause turbulence over the MAF and skew readings

 

Nope. Just a MAF section.
To take out any turbulence a MAF must; be placed at least 6-10 inches after any neck or bend, and 4-6 inches before any neck or bend.
ie; you only need a clean 10-16 inches of 3" pipe to have the MAF work properly.

 

then why make it difficult and use 2.5 to 3 inch to 2.5? just go straight 3. its not going to make a huge difference in spool time

 

Because going straight 3" is a lot of un-needed volume that which results in a lot of air mass to move, thus slowing spool and charge velocity.

If you are running the pipe through the fender well, where the stock intake goes, you can have over 50" of pipe length from just the IC to the TB.
At 2.5" with a 3" section, that's a volume of 246 cubic inches.
A full 3" would be 353 cubic inches.... that's nearly 50% more mass that has to be accelerated or deccelerated during transient flow.

So, the simple answer is; it's simply un-needed.
Especially when 3" mandrels cost almost double to buy... it's far cheaper to do a 2.5", with a 3" section.

 

Thanks for the input guys

 

That's gay. I just bought a 3'' universal kit and I already had it setup 2.5 - 3 - 2.5

FML

How about that base tune man haha I'll have hpt soon I need something to go off of. If you don't wanna do it it's cool.

 

mine is blow through with a 3" maf section only and it works perfect

 

I agree completely. Just did it.