[Supras] Blowff valve

[berniek at technicaldevelop.com]

Steve and group:

    The Turbonetics Raptor seems to have too stiff a spring, the so 
called "10 pound" spring.  I don't know if the rating refers to spring 
constant or force under preload.  But the poppet in the valve only opens 
3/16" or so with full vacuum from a vacuum pump on the top of the 
diaphragm.  A fellow I spoke to at Turbonetics did not seem too 
knowledgeable.  The instructions say two different things about 
connection to the bottom of the diaphragm:  run it to the boost source 
upstream of the throttle plate, or vent it to atmosphere with a suitable 
filter.  The first alternative leaves open the possibility of the valve 
opening due to boost pressure directly on the poppet area since at WOT, 
both sides of the diaphragm are exposed to boost.  The second 
alternative sounds as if it may still cause surge, because vacuum 
applied to the top of the diaphragm will be less than the 29" used for 
test when it did not open very far. 


    I believe I'm going to make up a spacer for the case halves to put 
under the diaphragm, or find a lower rate spring from Lee Spring or 
McMaster-Carr.  Its not that time consuming to take apart, and can tune 
it that way to avoid surge.  I would rather vent the bottom of the 
diaphragm to atmosphere to be sure the valve is closed under boost.  
Apparently there is a hidden O-ring dynamic seal in the guide for the 
poppet stem.  I'll keep you posted on the results.


    Also, I installed a 1-1/4" copper coupling (1-1/2"OD) in the 
accordion hose by brazing steel flanges on it cut from an empty 
Bernzomatic cylinder, and screwed the outside and inside flanges 
together with 4-40 screws (heads inside, double nutting and Loctite 
outside) to connect the valve discharge to.  It's all sealed up with 
Permatex Hi-Tack.  The valve flange steel weld neck is a good fit in a 
copper DWV 2" tee with a 1-1/4" branch connection after a bit of 
machining.  That will be soldered in place to hold the valve body and 
will be installed in a cut-out section of the angled hose coming out 
from the right side fender (still need to install hardpipes, but the 
material is on the way). 


    Bernie

Steve Michael wrote:
> I'll have to watch that when I get my 60 trim installed. I may have to 
> upgrade my BOV at that time as well.
>
> Thanks for the note!
>
> -=S=-
>
> ----- Original Message ----- From: <berniek at technicaldevelop.com>
> To: <azsuprasm at qwest.net>; <Supras at supras.com>
> Sent: Thursday, November 15, 2007 11:25 PM
> Subject: Re: Blowff valve
>
>
>> Steve:
>>
>>    Thanks for the answer.  When you modify the CT26, the map becomes 
>> more like the TO4-'57" as I found out from Performance Techniques.  
>> The surge line leans to the right very quickly.  So there is no way a 
>> stock or Bosch BOV is going to work.  A Turbonetics valve is on order.\\
>>
>>
>>       Bernie
>>
>>
>
>
>
>