[Supras] 57 trim CT26 alteration

[Jeff Mohler]

I have a few friends with VW diesel TDi's with VV turbos..nice.


But..the WG doesnt flow exhaust to make HP..it only needs to flow MORE
if you have too much boost, IE..creep.

I dont see where a lick of power comes from a larger WG transit.

On Dec 10, 2007 8:59 PM, berniek at technicaldevelop.com
<berniek at technicaldevelop.com> wrote:
> After disussing it with (I forget who) at Performance Techniques, he
> agreed that the boost would come on faster without clipping the turbine
> wheel.  But then, what to do with volume of exhaust gas after spoolup?
> Bypass more at the wastegate, which is what we did.  The ideal solution
> would be variable geometry inlet guide vanes.  Although they made a
> brief appearance on cars some time ago, they seem to have become
> relegated to truck use, no doubt due to cost considerations.
>
>
>     Bernie
>
>
>
> Jeff Mohler wrote:
> > What advantage does this offer..if you dont have boost creep, then
> > opening up the boost release (wastegate) isnt..adding anything.
> >
> > Is it?
> >
> > On Dec 10, 2007 5:11 PM, berniek at technicaldevelop.com
> > <berniek at technicaldevelop.com> wrote:
> >
> >>  From what I understand, the customary way to allow more exhaust flow
> >> through a CT26 is to clip the turbine wheel.  I discussed this with
> >> Performance Techniques when I had one modified for 57 trim.  To cut to
> >> the chase, I decided on boring out the wastegate passage instead, as the
> >> cross sectional area can almost be doubled while still leaving at least
> >> .080" at the circumference for sealing by the disk.  The area is still
> >> far less than the area of the diaphragm in the actuator, so cracking
> >> open early from disk force did not appear as if it would be a problem.
> >>
> >>
> >> Waste gate passage boring is one aspect of the modifications I forgot to
> >> mention in previous postings about mods.  The 15-17 PSI boost comes on
> >> explosively at 3000 RPM and it pulls strongly to redline with stock cams
> >> and a cleaned up head (valve bowls and intake passages cleaned up with a
> >> die grinder and carbine burr) with the other mods.  Caught it once at
> >> 6500 RPM at the top of second gear, it was so quick.  Maybe the former
> >> owner installed an earlier ECU (from before full crankshaft
> >> counterweighting), also indicated by idle speedup when turning lights on
> >> (90-up does not have the circuit board parts stuffed for that
> >> function).  Just curious if anyone else has done waste gate boring.
> >>
> >>
> >>     Bernie
> >>
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> >>
> >
> >
> >
>