[Supras] 57 trim CT26 alteration

[berniek at technicaldevelop.com]

Rich:

    As stated to Jeff, no, there will not be any additional power 
produced, but the boost will come on sooner, previously discussed with 
Performance Techniques.  And it does so, explosively.  There are two 
schools of thought about increased tendency for cracking:  One is that 
somewhat thinner wall by the wastegate passage will experience less of a 
transient thermal gradient and therefore less transient stress.  The 
second is conventional wisdom:  Thicker will be stronger.  But stock 
ones crack all the time.  In any event, I bought a new turbine housing 
for $100 when I had my rebuild done, so I have some time to see what 
happens.


    BTW, the best way to stop a crack is to drill a small hole at the 
end of it.  Problem is that the alloy (non-magnetic, no it must be 
nickle-chrome stainless) is very tough to machine, so use of a carbide 
or high cobalt high speed drill run at low speed with plenty of 
evaporative (tapping) lubricant is a must.  Sulfurized cutting oil won't 
do a thing with that material.  Bea careful with carbide drills:  They 
are costly and break very easily. 


    Bernie

Rich wrote:
> I agree with Geoff.  The power loosing restriction on the CT-26 is 
> /through /the turbine area, which can be improved by clipping the 
> exhaust wheel at the expense of more lag.  Making the wastegate larger 
> doesn't increase flow through the turbine area...  If I were to bolt a 
> larger external wastegate into my Infiniti, why would I expect any 
> power increase?
>
> Also by removing material from an area of the casting already known to 
> crack (wastegate flange) probably from heat stress, aren't you further 
> provoking a problem in that area?
> -Rich
>
> Jeff Mohler wrote:
>> 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
>
>
>