Some questions....t25 / custom pump

[darrenjlobb]

Hey guys...

Right, as you know i suffernt a fairly major bottom end explosion back along, not sure what let go first, the rod i think, but anyway, ended up with 2 huge holes in the block and a right mess!

(im the peugeot XUD driver not a vdub sorry)

Basicaly, i am now rebuilding the new engine, have got some slightly stronger rods (thicker) but not massivly, so still scared about it happening again.

The setup is basically a 1.9 IDI TD XUD engine
Hybrid turbo (t2 with t25 compreessor wheel)
Modified bosch pump (11mm head, gov mods and more dynamic advance) (lots of fuel)
Straigh though big bore exhaust
Piper fast road cam.
Custom front mounted intercooler.

Now, i was running 28psi when it blew, and am thinkiing maybe the boost is what killed it...ive read about people skimming 2-3mm off the top of the pistons to reduce the comprsssion, anyone know if there is potential in doing this? How badly is it going to effect my off boost, and will i need more boost to make the same power as before?

The reason i ask, is i had the wastegate totally disabled before, and all it would build was 28psi, is this normal for a t25 turbo? i would have thought it would have a bit more, even if it wasnt safe...just wouldnt boost any harder.

Has anyone got any ideas on how i can get more from it / how i can prevent / help it from going bang again?

I now have oil pressure / oil temp and EGT gauges to help monitor things...

Thanks

[RabbitJockey]

i think you need more flow.  you have a tiny turbo and you're trying to move lots of air, even with the t25 wheel its a small small turbo.  and 28 psi is too much boost too, especially with a closed wastegate, when ur reallly getting revved up thats a lot of air to move through that tiny turbine housing.  i think your pump can move way more fuel than what your turbo could ever move air for.

[rabbitman]

Skimming the pistons would mess up the quench area.

Though if you did skim 'em you'd need less boost to make the same power, ya know, fit more air in there.

But starting might be a pain.

[darrenjlobb]

I think i need a better understand of turbos, this is one area thats always really confused me,

I cant quite grasp the whole flow / pressure thing....the way i always see it, is if you are pushign 28psi (pressure) of boost into the intake system, surly its only at 28psi because the engine is sucking all it can, surly the only way to increase the air that the engine sucks in is by increasing the pressure it is in the inlet so you can pack more in?

By flowing more air at lower psi, how does it still get in there?

I find the t25 fairly laggy as it is...3k for full boost, what turbo are we suggesting here...?

Thanks again for your time,

[darrenjlobb]

Anyone got any suggestions on what turbo range id be looking at? Are we talking GT25 rather than t25? or maybe t3, wats the size differnce / flow difference betwen t3 and gt25...Only problem is, the peugeot manifold is a funny 3 stud triangle flange rather than the common 4 bolt type i see on here...

 

[55eta]

I think i need a better understand of turbos, this is one area thats always really confused me,

I cant quite grasp the whole flow / pressure thing....the way i always see it, is if you are pushign 28psi (pressure) of boost into the intake system, surly its only at 28psi because the engine is sucking all it can, surly the only way to increase the air that the engine sucks in is by increasing the pressure it is in the inlet so you can pack more in?

By flowing more air at lower psi, how does it still get in there?

I find the t25 fairly laggy as it is...3k for full boost, what turbo are we suggesting here...?

Thanks again for your time,

you got to think on the lines of e.g if you have a 20mm pipe with 10psi of air coming out of it  at x cfm [cubic feet a min] the same cfm put through a 40mm pipe would not produce the same PSI but you have the same amount of air [cfm] flowing through it ,so when a small turbo is working at its upper limits the pressure is increasing {psi} but the cfm is not increasing in proportion so its increasing pressure but not cfm  ,there's a bit more to it but that's a rough example

[darrenjlobb]

So what turbo are we talking...what do you vw people use for 160+hp IE 2 28psi and above....

GT25?
T3?

What kind of size / lag are we talking with turbos like them?

[MJF]

6 cyl Mercedes K24 (20-22psi) should be good for that power.

[darrenjlobb]

Ah, so its more the hotside thats the problem...what kind of size the k24 compard to my t2-t25 hybrid..?

And mounting.. my turbo mounts with a triangle 3 bolt design flange, not the normal 4 bolt....

[vanbcguy]

If anyone has pics of all 3 sizes of VW turbos side by side that would be awesome (I mean the 'pre-VNT' ones - K03 / K14 / K24) - would really help show the difference between them.

[darrenjlobb]

Ok ive been told today, that my turbo probebly isnt acually a t2-t25...

Basically externalls its identical to a standard t2, except if u look at thecompressor , the blades are at a different angle, but inlet outlet etc all the same size?

Have i been conned?

[4wheeler]

Compound turbos I`ve decided is the answer to any volume/lag concerns.

USing a K14 fed by a T3.  Looking for 25PSI boost and consistance volume throughout the entire RPM range.

Volume is key.... Boost pressure is relatively easy!

[zukgod1]

K03, K14 and a K26.compressor wheels.





k14 and k26 side by side

[darrenjlobb]

Anyone got simular comparison pics of some garrett turbos?

[55eta]

http://www.turbobygarrett.com/turbobygarrett/products/products.html all you need to know