SaabCentral Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
405 Posts
Discussion Starter #1
My 88 SPG is having stalling problems. I think it's my bypass valve (my girlfriend says the clamps and hoses look like they are in good shape). Since it needs replacement I figured I would upgrade. However I have noticed that group9 has some performance bypass valves that go for like $159. I am wondering if I should just buy a bosch bypass valve for like $50 from later model turbos (which are supposedly already an improvement on the stock valve). So basically is it worth it getting the more expensive valvue for $159. I am not really interested in any BOV's. The 'phssshh' sound is cool but I prefer not tossing that compressed air.
 

·
Banned
Joined
·
637 Posts
Welll.. it's your $$ But BOValves only release boost at the appropriate tme.. they cannot add power. Yers is likely shot.. Test it by sucking on it's Vac line.
OEM bosch valves are good for 15 psi (new) Viggen ones are rated for 20+ psi.. Not realistically likely that you would actually need more than that :)
Fancy Boutique ones are Shiny.. but that's about it, performance wise.
 

·
Registered
Joined
·
9,170 Posts
The main problem with the stock Bosch valves is that they are made out of a fairly cheap plastic which becomes brittle with heat and then leaks. There are aftermarket recirculating valves like you have found, which are usually of a stronger construction. I don't know the Group 9 ones, but Forge, who make my BOV, also do a recirculating one. Both are made out of billet aluminium, are considerably stronger than the stock ones and have larger port areas for better response. They are definitely of high quality construction, but are not cheap.

Bear in mind that stalling problems can be caused by a lot of things. It might well be the bypass valve, but it might be something else.
 

·
Registered
Joined
·
405 Posts
Discussion Starter #4 (Edited)
I just looked at the forge valves on . They charge about 100GBP, which is $175. Is there any place in the U.S. to buy forge from or similar valves made out of alu (and maybe for a little less money). Group9 doesn't specify the material of the valve.

Basre said:
Yers is likely shot.. Test it by sucking on it's Vac line.
What exactly am I looking for when I suck on it? I mean what should I notice if the valve is shot? If the valve is shot nothing should happen, right?

I have yet another question, I was looking around on ebay and found a bypass valve that look intersting. However I don't know what the exact dimensions are of the stock valve and don't know if this one will fit. Here's a link to the auction: http://cgi.ebay.com/ebaymotors/.....
Does anybody know the required dimensions for it to fit without changing any hoses?
 

·
Banned
Joined
·
637 Posts
Test it by sucking on it's tiny Nipple or the Vacuum line attached to it.. Suck and hold the vacuum by plugging the tube/orifice with your tongue.. it should keep that vacuum indefinitely. Also pull the thing out and take a peek at it's diaphragm.. the rubber thing that is the moveable seal on the large openings, it should not be damaged nor should it be too easy to push backwards with your finger. This thing is what has to hold against boost pressure.
It is also possible to improve the Bosch valves effectiveness (ability to hold Boost) by mounting it in reverse to the OEM position.. a small change in itself, but just like relocating yer wastegate's boost hose to the Intake plenum.. it all works together to increase power/response..
 

·
Registered
Joined
·
16 Posts
Basre said:
Welll.. it's your $$ But BOValves only release boost at the appropriate tme.. they cannot add power. Yers is likely shot.. Test it by sucking on it's Vac line.
OEM bosch valves are good for 15 psi (new) Viggen ones are rated for 20+ psi.. Not realistically likely that you would actually need more than that :)
Fancy Boutique ones are Shiny.. but that's about it, performance wise.
mr. basre is the bringer of the good advice and i also agree that the expensive ones are quite shiny. i add that the test should also include the blowing into in addition to the sucking on the line to the valve.

there is no problem with stock bosch valves. the plastic doesn't fail - the diaphragm does. one problem with the shiny kind is that it is hard to see all the shinyness when installed.

early valve part numbers all supercede to the one used on the viggen that can hold the super extra boost.
 

·
Registered
Joined
·
134 Posts
I have Group 9's adjustable bypass-valve. I wanted something that wouldn't fail so easily, dumped more air and wouldn't *pshhhhhhh* so loud. I was already getting parts from Group 9 so i indulged in a bit of 'shiny' :cheesy:

If your stock valve is the problem and your car isn't too wild get atleast the viggen valve and forget about it.

http://groups.msn.com/TheSwedeDemon/shoebox.msnw?action=ShowPhoto&PhotoID=20
 

·
Banned
Joined
·
5,841 Posts
Your turbo pipes and hose's are lovely!

Where did you get them from?

My rubber ends can pop off under heavy boost, horrible feeling!

Those must be able to hold a lot of pressure?
can you recommend any upgrade for the pipes and hoses?
 
1 - 8 of 8 Posts
Top