[Supras] 57 trim CT26 alteration

[berniek at technicaldevelop.com]

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
>>
>> _______________________________________________
>> Supras mailing list
>> Supras at supras.com
>> http://supras.com/mailman/listinfo/supras_supras.com
>>
>>     
>
>
>