Disclaimer: I am new to the LS and turbo charging world.....

My Twin turbo BMW M5 project.

Power goal: 700hp/650lbstq at the wheels.

Project goal : To make a lot of smoke. The car is heavy, 4100+, and I plan on doing a fancy shmancy stereo in it, so it will not be a drag racer. Just a fun car that I plan on driving a lot in the summer. I will take long trips in it too, so making it reliable is key. Well, as reliable as a project car can be......

The car: 2003 BMW M5, Sterling Grey/Caramel Executive Leather interior

The engine: Gen III 5.3L, completely refreshed block with all new OEM bearings, new stock rods with floating wrist pins, new stock dished cylinders, new rings gapped to 25/28, 799 heads, Brian Tooley twin turbo cam, .660 lift platinum springs, titanium retainers, BTR chromoly pushrods, LS6 intake.

Transmission: T56 to the stock BMW M5 3.15 rear end.

The turbos : CX Racing 61mm turbos

More details - 100 cell race cats, some sort of mufflers with electronic cut outs, A2A intercooler, meth injection, HPtuners, retaining AC (if it matters), among other details.....

The questions:

These are T4 turbos. I would like to use these elbows, but they only go from T4 to 3" V band. CX Racing Elbows. I can not locate another set of elbows that go from T4 to 2.5" V bands, which is what I planned on using for my hotside from the exhaust manifolds. I am planning on using either 2010 Camaro manifolds or these Hooker manifolds depending on what fits. Both of which are 2.5" piping. If neither work, I will fab up some log headers.

I was then reading that these turbos need plenty of air movement to spool quickly. I am just worried about running out of air up top. Would going from 2.5" manifolds to 3" piping to T4 be a bad thing? Still need to check to make sure I have hood clearance for 3" piping. I'd rather not fab up a T4 to 2.5" adapter.

Next question, coming out of the turbo hot side, it has a 3" discharge. Would it be ok to use 2.5" or would it be better to use 3"? Again, I am not certain if I have room for the 3", so it may be a moot case. I just want to make sure these turbos can breath.

 

You're complicating it a bit.

Either build a 2.5" hotside that doesn't use the elbows or V-bands, or buy turbo headers that do. You can get 2.5" to T4 flanges from CX for like $30/each. Build your hotside to run the 2.5 inch piping into the flange wherever you want to mount the turbos.
Or get the headers that those elbows were designed for.

You're not going to have top end issues with 2.5" piping. People have made more power than your goal on 2".

 

Thanks for the reply.

With the placement of the turbos, a 90 degree T4 flange is needed. Would you happen to have a link for the 2.5" to T4 elbows? The only thing I can find for 2.5" to T4 is a dual inlet for a single turbo crossover pipe.

 

They aren't elbows. They're just the flange. You buy a piping kit and make your own elbows. Those CX racing elbows were designed to be used on the ends of the CX racing up and forward turbo headers with 3" V-band collectors. If you don't need V-bands in the middle of your hotside, then don't use them.

 

Check out dburt86's E36 M3 twin turbo build

https://ls1tech.com/forums/forced-in...ay-turbos.html

 

Thanks,

I've read that thread, along with just about every BMW/LS swap thread 10x, even spoke with him VIA text. He is using a little larger turbos than I am.

I guess I'm not worried about choking them, rather having too large of piping and having adverse effects. Then again, I'm not versed enough to even know if there ARE adverse effects to running too large piping?

 

Too large of piping will just slow the spool a bit.

 

Look at the UPP 5871 turbos... Two year warranty, and they are the base turbos that UPP used on their base twin kits for gto'so, corvettes, and Camaros. They are $499 each and will spool instantly.

 

Already purchased the CX Racing turbos. $285 each.......

 

Cool. I hope it works out for you.