[Supras] 57 trim blowoff valve recommendation

Wed Nov 14 21:51:35 CST 2007

With the money and effort put into the engine and the turbo ($600+ for 
the 57 trim modification, rebuilding, wastegate port boring, a new 
turbine housing for the turbo alone), I'm not about to take any 
chances.  I spoke to James at Performance Techniques a couple of times 
and examined the map for the TO4E "57", supposedly the closest to a 57 
trim CT26 because of the compressor wheel used.  The surge line lays way 
over to the right.  I don't know what the discharge pressure is when the 
throttle slams closed and the present Bosch BOV is supposed to work, but 
the pressure ratio (measured in absolute pressure units) is certainly 
higher than the 2:1 with 15 PSI boost.  No wonder it surges, even with 
relatively little boost at part throttle when shifting gears.

Performance Techniques recommends a Turbonetics Raptor BOV, probably for 
political as well as practical reasons.  So I dutifully paid $253 to 
Summit Racing earlier tonight and will have it here by Friday.  Yeah, I 
was tempted by ebay pricing of some Greddy knock-offs, but the genuine 
item is more reliable.  Tonight was spent at LOWes getting two types of 
1-1/2" ID hose for the discharge, and copper fittings to replace part of 
the stock boost hose before the plastic piece leading to the 3000 pipe 
(yeah, that will be upgraded too).  Believe it or not, a Taco hot water 
heating circulator flange will just about fit the branch of a 
2"X2"X1-1/2" copper tee and the BOV inlet flange, with a little machine 
work and brazing.  So that setup will  feed the BOV inlet.  The run ends 
of the tee will fit in the hose just mentioned, with rings of #14 copper 
wire soldered near the ends to form a bead to hold the hose on.  The BOV 
adapters on ebay all seem to be 2-1/2", too big for the present setup 
(they are cheap and I can get one later when upgrading IC piping, but 
they look a bit crude.  The ID will probably need to be bored smooth and 
increased in size a bit). 

    A phone call to Turbonetics yielded a drawing of the wastegates and 
BOVs they make.  The Raptor discharge will take a 1-1/2" ID hose. The 
1-1/2" hose will connect the discharge of the BOV to the accordion 
hose.  Minor surgery will be required for the accordion, cutting a 
1-1/2" hole in the curve just behind the AFM, and making two 16 gauge 
steel rings to conform to the curve.  One will be inside the hose, one 
outside.  The inner one will have a 1-1/4" copper coupling (1-1/2" OD) 
brazed to it sticking through the hole, and the outer ring will be 
clamped to it with a series of 6-32 or 8-32 screws (heads on the inside, 
elastic stopnuts on the outside).  Then the BOV discharge hose can be 
connected. 

    If anyone knows a simpler way to do the BOV discharge recirculation, 
I'd really like to know about it.  That work, and oil change, and a 
couple of other things are expected to take most of the weekend.

Bernie

Jim Jobe wrote:
> Actually I was noting the time when I had the stock AFM
> and thus also the stock ECU.  And, amazingly, I had a stock
> turbo then too.  It was pushing 13-15psi.  That was a long
> time ago for both of us.
>
> No ill effects, not even a backfire from it.
>
> Certainly not the case now...the cars or you maturing.  LOL!
>
> On Wed, Nov 14, 2007 at 06:16:09PM -0500, t72pwrd wrote:
>   
>> Option B with HKS SSQV vented to atmosphere worked for me as well.  My 
>> turbo was a -60 trim at 21PSI at the time.  HKS valve was located where the 
>> passenger side foglight WAS.  Amusing as hell to see people jump when I 
>> shifted.  Of course this was a damned long time ago and I was much younger 
>> then.  Some people even say I've matured ;-0
>>
>> Jim is also too modest to say he's running a turbo quite a bit bigger than 
>> any of the ones discussed so far.  SP61 or 63 IIRC.
>>
>>
>> ----- Original Message ----- 
>> From: "Jim Jobe" <jjobe2 at supratech.org>
>> To: <b2nice84 at aol.com>
>> Cc: <berniek at technicaldevelop.com>; <Supras at supras.com>
>> Sent: Tuesday, November 13, 2007 11:08 PM
>> Subject: Re: [Supras] blowoff valve recommendation
>>
>>
>>     
>>> Option B has worked very well for many, for a long time.
>>>
>>> I've also run just the HKS SSQV with no ill effects.
>>>
>>> On Tue, Nov 13, 2007 at 09:49:19PM -0500, b2nice84 at aol.com wrote:
>>>       
>>>> The below options is using a blow off valve.
>>>>
>>>> Option A
>>>> The HKS SSQV has an adapter you can add to be able to redirect the air 
>>>> back into the accordion hose.? But of coarse it costs some money and a 
>>>> little of thinking to install.? Regardless it is doable and you will lose 
>>>> the BOV sound if you care about it.?
>>>>
>>>> Option B
>>>> Another way (this is what I am doing) is to keep the stock Bypass valve 
>>>> in and install the blow-off valve at the same time (blow-off valve air is 
>>>> released into the atmosphere).? It eliminated the bogging. The stock 
>>>> bypass valve keeps the AFM happy and the blowoff valve let out all the 
>>>> extra air out that the stock bypass valve could not (over 8 psi) when I 
>>>> am boosting over stock.?
>>>>
>>>> I feel the stock bypass valve works great when you are boosting stock.? 
>>>> But when boosting more then stock I feel it needs a little more air out 
>>>> that the stock bypass valve will not allow.? That is why I used Option B.
>>>>
>>>> Now I am waiting for Jeff to make a comment on how wrong it is for me to 
>>>> do this.? hehe
>>>>
>>>> Brandon
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: berniek at technicaldevelop.com <berniek at technicaldevelop.com>
>>>> To: Supras at supras.com <Supras at supras.com>
>>>> Sent: Tue, 13 Nov 2007 5:43 pm
>>>> Subject: [Supras] blowoff valve recommendation
>>>>
>>>>
>>>>
>>>> For the last two weeks I've been getting my jollies by driving my '91
>>>> with 550cc injectors, 57 trim turbo, Walbro, Lexus, 3" exhaust from
>>>> turbo back, etc.  However, a disturbing boing-oing-oing sound has
>>>> persisted from the air intake when closing the throttle under 15 PSI
>>>> boost.  Spoke to James at Performance Techniques about this, and he says
>>>> it is compressor surge, which I suspected.  From all I have read, using
>>>> the Bosch Porsche right angle blowoff valve should have been sufficient,
>>>> but it is not.  I get the sound even at low boost.
>>>>
>>>>
>>>> So I'm looking for recommendations as to which BOV to use.  I would like
>>>> to recirculate to the accordion hose, even if I need to cut a hole in it
>>>> and use curved, clamped large washer-like pieces on the inside and
>>>> outside to provide a large bung for the BOV discharge.
>>>>
>>>>
>>>> Any and all suggestions would be appreciated.  Thanks.
>>>>
>>>>
>>>> BernieK.  PS:  Arlene and others were right.  There is never enough
>>>> power even if you can "walk" the tires in second gear.  Starting to
>>>> wonder what to do next for more HP.
>>>>
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