Compound turbos

[Hoble]

I was looking at the gt2056 and that's actually slightly bigger than the "big" turbo I was planning on running. And that's bigger than a stock t3. I'll be coming into boost pretty late with that setup. Big turbo wouldn't even spool till 6 grand in second.

I went for a drive in vrt with a 60 trim with a .60ar. That didn't come into boost till almost 4gs

[RabbitJockey]

I was looking at the gt2056 and that's actually slightly bigger than the "big" turbo I was planning on running. And that's bigger than a stock t3. I'll be coming into boost pretty late with that setup. Big turbo wouldn't even spool till 6 grand in second.

I went for a drive in vrt with a 60 trim with a .60ar. That didn't come into boost till almost 4gs

A gt2056 is definitely smaller than any t3 dimensionally and everything it does flow more than quite a few t3s but it is definitely not bigger.  If you rode in a vrt with a 60 trim I would almost garauntee it was t4 which is much bigger than a 60 trim t3, neither would work well on a 1.6 by itself,  anyways the comparison is apples to oranges

[Hoble]

Oh I missed the actual size part. My bad. And yea I knew the comparison was off as its gas to diesel and I don't know much about the turbo itself. Just googled the gt2056 and an interesting site popped up.

http://www.vwdiesel.net/forum/index.php?topic=28551.0

Now the first post one the second page is what is actually interesting. This turbo spools faster than the t3. The small turbo will be only running around 15 psi and the big will be around 20 psi to get to 35psi total.

After work tomorrow ill look into the bigger turbo you had mentioned to figure out where I am going with that.

[Alcaid]

justiz00: your assumption of a BSFC of 0.38 @ 6000RPM is just WAY off!!!

Stock 1.6TD had a BSCF of 0.52-0.53 at 4500RPM and it gets worse and worse as RPM increases. Modern turbochargers, porting etc. will improve this factor but you will never ever get a the magic number you've assumed. Also I think you have used a way too optimistic volumetric efficiency as that one also chokes at high RPMs.

Short summary: you need alot more pressure!

[RabbitJockey]

Oh I missed the actual size part. My bad. And yea I knew the comparison was off as its gas to diesel and I don't know much about the turbo itself. Just googled the gt2056 and an interesting site popped up.

http://www.vwdiesel.net/forum/index.php?topic=28551.0

Now the first post one the second page is what is actually interesting. This turbo spools faster than the t3. The small turbo will be only running around 15 psi and the big will be around 20 psi to get to 35psi total.

After work tomorrow ill look into the bigger turbo you had mentioned to figure out where I am going with that.

if you keep reading the thread, he gets most of that resolved, he was running a tdi cam(which is crap) and a tdi intake(which is also crap) and if it was surging it had more to do with those 2 parts than anything else.  But also in a compound setup surging would not be much of an issue.  boost doesn't just stack like that either, if the small turbo does 15psi, you would only need about 10 psi on the large turbo to get 35.

i wondered when alcaid would be chiming in!  like i said before tho i can only give you general ideas on what works, with out actually trying it its hard to say what actually works well and what does not.

[justiz00]

justiz00: your assumption of a BSFC of 0.38 @ 6000RPM is just WAY off!!!

Stock 1.6TD had a BSCF of 0.52-0.53 at 4500RPM and it gets worse and worse as RPM increases. Modern turbochargers, porting etc. will improve this factor but you will never ever get a the magic number you've assumed. Also I think you have used a way too optimistic volumetric efficiency as that one also chokes at high RPMs.

Short summary: you need alot more pressure!

Those were straight from garrett's formulas. I did not know the stock numbers. Yours will help everyone be more accurate in the future.

[Alcaid]

Garrett's numbers are for (T)DI engines, they are more efficient than our IDI engines

[justiz00]

F-it Im going 2jz. Not really but these new numbers are not comforting.

50.41 lb/min (.55 bscf)
77 lbs of boost
6.89 PR

70% eff. with minimal pressure loss at filter and i/c.

 

Good luck hoble, Ill just settle with my build as a nice auto weekend cruiser.

[Alcaid]

.45BSFC should be doable at 6000rpm with sequential setup (HP turbo bypassed at higher RPMs for higher efficiency and less back pressure) and a modern LP turbo. Also AFR can be a bit richer on the IDIs without smoke, 17-18 vs. 20-22 for the (T)DIs. These numbers are based on dyno experience, not just guessing. I will have a sequential setup ready for dyno spring time next year

To actually make a lot og HP at 6000rpm requires a heavily modified pump!

[RabbitJockey]

.45BSFC should be doable at 6000rpm with sequential setup (HP turbo bypassed at higher RPMs for higher efficiency and less back pressure) and a modern LP turbo. Also AFR can be a bit richer on the IDIs without smoke, 17-18 vs. 20-22 for the (T)DIs. These numbers are based on dyno experience, not just guessing. I will have a sequential setup ready for dyno spring time next year

To actually make a lot og HP at 6000rpm requires a heavily modified pump!

Not to be contradictory, and only to raise conversation, i've been going over the 1.5d sae papers which has a graph showing the ve at over 90% until 4500 rpms where it swiftly drops off, and is well below 85% by 5000, it also has info on the bsfc but i haven't quite wrapped my brain around it yet.

http://home.comcast.net/~jakeru/15dsae.pdf

[R.O.R-2.0]

Those are good choices but I think I'd go a bit smaller like a gt2056 for the small one and a gt2860 for the big but everything is a guestimation

those turbos seem a little bit on the large side..

the 2056 and 2256 are often run as large singles on these engines, with nice spool characteristics..

2056 is basically a big T3..

maybe an 1856 and a 2860?

im just thinking out loud.. he has a large wastegate to bypass the small turbine, so it shouldnt matter how much it flows up top..

we want quick spool on the bottom end..

[Hoble]

2056 is basically a big T3..

If you read the link at the top of the second page on page 2 it actually says the 2056 spools quicker that a stock t3. But I will look into that other turbo for sure.

And trevorbr, yea I'm not sure exactly how the compound boost pressures stacked up, I new they didn't multiply but adding didn't make sense ether. Basically I was going to start both turbos on a low psi and turn it up slowly and see where I got too. What I was saying with the psi numbers is that I want the big turbo to be running the majority of the pressure in the system as the small turbo compresses the atmospher given to it.

I know a lot of this is just guesstimation and I'm fine with that. It will probably be closer than my guess (as we figured out with the k03 and t3)

[R.O.R-2.0]

2056 is basically a big T3..

If you read the link at the top of the second page on page 2 it actually says the 2056 spools quicker that a stock t3. But I will look into that other turbo for sure.

And trevorbr, yea I'm not sure exactly how the compound boost pressures stacked up, I new they didn't multiply but adding didn't make sense ether. Basically I was going to start both turbos on a low psi and turn it up slowly and see where I got too. What I was saying with the psi numbers is that I want the big turbo to be running the majority of the pressure in the system as the small turbo compresses the atmospher given to it.

I know a lot of this is just guesstimation and I'm fine with that. It will probably be closer than my guess (as we figured out with the k03 and t3)

i drive a 2056 EVERY DAY...

i know how they perform...

they spool up as slow as a T3.. promise you..

i think you should shoot for a midsized turbo, and a big turbo..

not a big turbo, and a bigger turbo..

if you size your turbos too large, its gonna be just like running one big laggy turbo...

sure, the second turbo will help to spool the first, but to what degree? its not going to turn a large, semi-laggy turbo into an insta-spooler...

im just saying that i experience turbo lag quite a bit with my 2056 on my 1.6D

and yes, a GT2056 is close in comparison to a larger T3 turbo...

[Hoble]

Conflicting info.

Can you find any info on the 1856 for me? I couldn't find anything useful

[R.O.R-2.0]

Conflicting info.

Can you find any info on the 1856 for me? I couldn't find anything useful

i dont remember who ran that turbo, but it worked nicely he said..

dont remember what it came off of either..

maybe im thinking of something different.. this was a GT18 NON-VNT..