-
The (official...) COMPOUND turbo thread!
by
monomer
on 15 Apr, 2009 14:08
-
I've seen a couple of fab pics....
some talk....
I'm to the point where I need to decide what turbo setup to run. VNT would be nice, but it seems we lack PROPER control of the unit (pressure actuator still isn't good - vanes will foul up)
The fab pics I've seen of the compound setup are amazing. So amazing it made it to my back desktop image on this machine. I'd like to know more on the design end of things. Which turbos would complement each other well - CFM, efficiency and the like.
-
#1
by
RabbitJockey
on 15 Apr, 2009 14:33
-
i kind of wonder if a little k14 dumping into a gigantic turbo like a t3/t4 would be nice the k14 would keep you moving nicely for daily driving, then when you really want to wind out your engine that big gigantic turbo would really flow, i don't know how it all works though,
-
#2
by
53 willys
on 16 Apr, 2009 00:23
-
anybody try a k14-k26 compound yet?
-
#3
by
Smokey Eddy
on 16 Apr, 2009 04:03
-
i kind of wonder if a little k14 dumping into a gigantic turbo like a t3/t4 would be nice the k14 would keep you moving nicely for daily driving, then when you really want to wind out your engine that big gigantic turbo would really flow, i don't know how it all works though,
That's what i would do.
The jumbo turbo would be essentially useless out side of WOT.
could make some outrageous intake pressure.
-
#4
by
Rabbit on Roids
on 16 Apr, 2009 10:36
-
VNT + 300D turbo... thats what i was told would work well if you already have a VNT.
-
#5
by
zukgod1
on 16 Apr, 2009 11:00
-
anybody try a k14-k26 compound yet?
I think that would be the perfect combo.
-
#6
by
91redjetta
on 16 Apr, 2009 14:15
-
i just like to see one of this motors that was built really well.. made good power and was driven daily and didn't blow up in a month!! twins would be nice.. but just so you can say you've done it.. i don't think it would be good daily. and probably wouldn't last... just my thoughts...
-
#7
by
monomer
on 16 Apr, 2009 15:26
-
VNT + 300D turbo... thats what i was told would work well if you already have a VNT.
the t3 turbo on the 300's is still tiny.
I was thinking of something small feeding into a bigger turbo, along the lines of a 60-1
-
#8
by
Rabbit on Roids
on 16 Apr, 2009 18:34
-
a t3 off a merc is quite a bit bigger than the stock t3 on our vw's
-
#9
by
53 willys
on 16 Apr, 2009 21:51
-
only reason I have not tried compounded turbos on mine is I don't think the head will stay clamped...maybe on a race only engine..but I doubt a DD dub running a BIG K14-K26 would last very long??
I know you could try to control boost...but your never gonna escape the fact that compounded turbos make BIG boost numbers witch seem to really be the problem on these heads...
I'm waiting for one of you guys to try it!!
-
#10
by
monomer
on 17 Apr, 2009 05:39
-
only reason I have not tried compounded turbos on mine is I don't think the head will stay clamped...maybe on a race only engine..but I doubt a DD dub running a BIG K14-K26 would last very long??
I know you could try to control boost...but your never gonna escape the fact that compounded turbos make BIG boost numbers witch seem to really be the problem on these heads...
I'm waiting for one of you guys to try it!!
external wastegate - I have a TiAL 38mm sitting here.
does anyone have one of these setup running? I gotta hear how it sounds.
the 30D turbo is 52-54 trim, and not to eficiant compared to modern turbos
-
#11
by
aidan
on 17 Apr, 2009 09:20
-
I didn't think turbo size mattered so much with compound?
I.e can a k14 hold 1 bar til say 4500rpm?
if so, k14 feeding x cfm (1 bar/PR of 2 right?) into 2nd k14 feeding x cfm into engine (again at 1 bar/ PR of 2). So that works out as pressure ratio of 4 (3 bar) total being supplied into engine.
I don't know how much cfm a k14 actually flows, but surely that would be enough for what these engines can make before there are reliability problems?
I'm hoping someone more knowledgable will say if what I have written is correct, but this is what I had been led to believe.
-
#12
by
aidan
on 17 Apr, 2009 10:47
-
Andrew is what I have put correct, re. pressure ratios?
I would agree, low end (idle to 1800rpm) the K14 is rubbish, as are most WG turbos, but compounds would increase airflow over all revs surely.
But say for example it makes 4.9 psi at 1400 rpm (just so its an easy 1.3PR), would that not become 2.6 total, or 1.6 bar gauge.
'Spool' hasn't sped up as such, but it gives the equivalent of 1.6 bar boost at 1400rpm?
Am I completely wrong with my working out here? If not, is the above low-rpm boost situation the reason why the 2nd turbo is larger, to reduce low end airflow?
-
#13
by
monomer
on 17 Apr, 2009 12:09
-
That's part of the reason I'm partial to VNTs. They can provide better low-end than a K14 and enough high end boost to threaten reliability on these engines. Additionally, the complications of a functional and reliable vane control system are much simpler than the complications of a compound setup.
is there a PROPER vane control system designed for our application?
one where the vanes work and respond as they should, AND do not foul up.
I have yet to see one.
-
#14
by
ryanp
on 17 Apr, 2009 14:15
-
this will be nice to see, I've not seen a control i see fit for purpose as of yet!
compound seems complicated when VNT's can do a similar job!
Ry