Help me pick a good turbo once and for all.

[zukgod1]

I know jack about turbos.

I know I can kill an K24 with ease.

I would like a k24/26 hybrid turbo but the shaft size is to damn small so I need a Garrett or equivalent turbo that has a larger shaft and a larger compressor than the k24.

I have been reading for a while now but without pictures I just dont get it when it comes to turbos.

Trim and AR confuses me.

First off anyone have the trim info on a K24 for me to compair to other turbos.
I think with this info I can pick what I need.


My car is a stock 1.6, gasket matched that's it.
10mm pump
Merc injectors
ARP head studs
AAZ head gasket
FMIC already mounted for boosting!!

I use it for a 62 mile commute and run around 3000rpm ont he freeway so I need a turbo that's damn near spooled by then so I can actually drive the damn thing.


MAIN thing is the current K24 specs so I can compare.

Can anyone help me without sending me to Garrett's web site?

[KTZed]

You looking for a new turbo, or a junkyard/oem application?
How prepared are you to make a new exhaust manifold/manifold flange to adapt to, say, a standard T3 style flange?
What kind of boost capability would you like from this turbo?

Answering these will help to narrow down your choices.
I would bet a large VNT would be awesome....Has anyone done a VNT20 on a 1.6 yet?  :twisted:

[zukgod1]

I think I want New. No more used stuff for me.

I have no problem making an adapter plate to mount the standard T series turbo.

Want 25-35 psi on the top end cruising want 10 or so.

[subsonic]

I have a Merc 300TD T3 I will be selling soon I think.  .48AR on the turbine housing.  Thats a bit bigger than stock VW turbos, it will spool a bit later unless you have the fuel turned up and a free flowing exhaust.  I believe it is a 42AR compressor with a 45 trim. It has the capability to move more air than either the stock T3 or K24 at slightly lower temps.  You would need a standard T3 flange / manifold to run it.  It has been dissasembled(lots of propane,PB Blaster, knuckle skin, cursing etc..) hot tanked and bead blasted.  I have the high performance complete T3 rebuild kit with the 360 bearing upgrade from gpopshop to go with it.  Just needs to be bolted back together.

[zukgod1]

How much are you thinking? Drop me a PM.

or some reason I'm thinking it will be to big on the exhaust side for me to spool it for daily driving. Sounds like it would be perfect for road racing maybe.. Either way let me know what your thinking for price.

[zukgod1]

Personally I think a 24/26 hybrid would be perfect if not for the damn weak shaft they have...

I'm REALLY tired of breaking these things.

Why the heck did they neck down the damn shaft on the compressor side?
If they would have kept it the same DIA to the end or maybe to up to the last  .250" I would still be running the original k24!!

[jackbombay]

Want 25-35 psi on the top end cruising want 10 or so.

    You will not find a turbo that can push more than 25 PSI and still be operating on its compressor map. How high above sea level do you live? Altitude makes a big difference when it comes to the Pressure ratio across the compressor.

  The .35 AR T3 is actually pretty good for big boost and decent cruising efficiency, see page 3 of the linked thread for the T3 map with points plotted for various running conditions, again those points are for a 1.9, but estimate the LBS/Min, subtract %15 and replot the point, the pressure ratio will stay the same so the point will just move left a bit.

  Check this thread out for a bunch of compressor map theory. I plotted all those points for a 1.9, for the 1.6 take %15 off the LBS/Min (X axis numbers) and you'll be quite close.

[jtanguay]

i don't think you would really want 10 psi for cruising...  more psi = isn't always a good thing...  you really only want boost on demand.  for passing/hill climbing/accelerating.

[zukgod1]

i don't think you would really want 10 psi for cruising...  more psi = isn't always a good thing...  you really only want boost on demand.  for passing/hill climbing/accelerating.

This is true more of a flow than pressure deal and yes on demand boost is what I want.

I just found a good VNT 15 in the next town over for a fair price.
I'm not to sure about the flow on the 15 vs the k24 though and building a VNT controller that actually works sounds like a pain in the BUTT.

[zukgod1]

Want 25-35 psi on the top end cruising want 10 or so.

    You will not find a turbo that can push more than 25 PSI and still be operating on its compressor map. How high above sea level do you live? Altitude makes a big difference when it comes to the Pressure ratio across the compressor.

  The .35 AR T3 is actually pretty good for big boost and decent cruising efficiency, see page 3 of the linked thread for the T3 map with points plotted for various running conditions, again those points are for a 1.9, but estimate the LBS/Min, subtract %15 and replot the point, the pressure ratio will stay the same so the point will just move left a bit.

  Check this thread out for a bunch of compressor map theory. I plotted all those points for a 1.9, for the 1.6 take %15 off the LBS/Min (X axis numbers) and you'll be quite close.

I disagree on finding a compressor that will move 25 psi but finding one that will move enough air lower as well will be a problem with a compressor large enough to move 25 psi.

Turbo maps do me no good. Unless someone is standing here explaining to me what they mean it's like a deer in the headlights.... Thus this thread, I can post up what I want and answer questions as to how everything it/will be set up though.

Will a VNT 15 move enough CFM to do what I want maybe?

[VW_Commuter]

Zudgod1, jackbombay isn't saying you can't find a turbo that won't push 25psi, what he's saying is you won't find one that can push 25psi and still be within it's safe operating limits.  When you push mechanical devices significantly past their design operating parameters they tend to destroy themselves.

[zukgod1]

I understand that, what I need is one that won't grenade when running 25psi. Its going to go there with the fuel I'm running so it need to be beefy enough to deal with it. I do think a k24/26 would do waht I need but not for long, would end up with a twisted shaft yet again.

[jackbombay]

Zudgod1, jackbombay isn't saying you can't find a turbo that won't push 25psi, what he's saying is you won't find one that can push 25psi and still be within it's safe operating limits.  When you push mechanical devices significantly past their design operating parameters they tend to destroy themselves.

  Exactly.

  You can run 35 PSI, but you will continue to blow turbos.

  A bigger compressor won't really help that, the problem with high boost levels is that the pressure ratio goes through the roof, sometimes bigger comp wheels can drive higher PRs, but not always, also with bigger comp wheels the map moves to the right with relation to LBS/Min so you run a decent risk of surge (crossing the line on the left), especially at altitude.

  Run a turbo in its "happy zone" (on the map) and it will run forever.

See this thread if you want to learn how to read a compressor map.

  This GT 20 has a good map and could work well for you, I can figure some typical operating conditions for you if you like. What RPM do you cruise at on the freeway? How many PIS on the freeway? What altitude do you live at? What max boost do you want to run? What is the highest RPM you run the engine up to?

[jackbombay]

Whats the bore and stoke of a 1.6?

[jackbombay]

Well, here is that gt20 map with a couple points plotted on it, right on the surge line at cruising speed, but thats probably ok, I assumed you lived at 5000 for the calculations,



  and here are the same couple points on the smallest GT15 map, nice and efficient at cruisiing speed, but out of breath for high RPM and high boost.