SaabCentral Forums banner
1 - 10 of 10 Posts

·
Registered
Joined
·
114 Posts
Discussion Starter · #1 ·
I know this will sound a bit naff to a lot of guys but I don't particularly like the atmospheric dump valve sound - I use my car for highway touring a lot and it would get on my nerves after a while, yet I have a problem with the high boost surge at about 25psi as you back off the throttle - the recirc dump valve does not cope well with it.
My guess is that I could install both a recirc and an atmospheric valve and get the best of both worlds - the atmospheric's ability to cope with high volumes of back pressure and the quiet operation of the recirculating valve.
What I need is a an installation guide - I have seen talk of this before but can't remember where.
 

·
Banned
Joined
·
7,270 Posts
sounds like a total waste of time to me... also the fuel injection system with an air-mass-meter in the intake will run badly if you vent metered air back out to atmospheare.

However... if you really wanted to do this then just link them up in series and fit a stiff spring to the atmos valve... then only when you're really gunning it will anything vent to atmosphere.

Still think it's a rubbish idea though. ;)
 

·
Registered
Joined
·
114 Posts
Discussion Starter · #3 ·
thanks, yes I've been experimenting with this and find that two dump valves cures the big problem that I have had with compressor surge. Making one valve recirc and the other atmosphere works fine actually but it does cause small isling issues so I will install two recirc valves - makes shifting much smoother under high boost than I have experienced at any time while running 25 psi.

Both valves are Forge and are adjustable so should be able to adjust them to suit. Piping is relatively easy as I have had a 25mm spigot welded onto the pipe just next to the throttle body.An interesting thing I noticed is that Saab used the larger of the two throttle body spigots for the idle air valve - I may swap the two hoses over to allow the DV to use the larger spigot - it must all help when that much air needs to be dumped.
 

·
Registered
Joined
·
801 Posts
I think it's a great idea, so great that I thought of it on my own about 2 weeks ago, and did this:



I was experiencing turbo stall and therefore bad spooling, and inturn because I am using a RRFPR I was having horrible fueling after shifting and I have blown up my custom turbo twice, Possibly due in part to not enough venting...25 psi is ALOT of Air, and my T3/T4 flows MORE air at 15 psi than a stock turbo at 20 psi, needs Tons of fuel at higher boost levels, and the un-official rule is that the stock valve is good for roughly 300 hp which I was probably breaking...certain cars like the Audi A8 and Maseratis, and Porsches use two valve, granted some are twin turbo cars...but still
 

·
Registered
Joined
·
5,975 Posts
If you want to be a bit techy you could use some solenoid valves and pressure switches, have the recirc dumping upto 7psi then the atmos +7psi.
 

·
Registered
Joined
·
2,879 Posts
Well, I know of cars producing up to and over 500hp using just a single dump-valve. If it was me, I would just run 1 larger dumpvalve, and safe me the hassle of installing two, plus, in my oppinion, it dosn't look as nice with 2, but that might just be me, it is my 2 cents, at least... :)
Daniel.
 

·
Registered
Joined
·
3,829 Posts
Saab-Daniel said:
Well, I know of cars producing up to and over 500hp using just a single dump-valve. If it was me, I would just run 1 larger dumpvalve, and safe me the hassle of installing two, plus, in my oppinion, it dosn't look as nice with 2, but that might just be me, it is my 2 cents, at least... :)
Daniel.
Or run a dual stage BOV like some of us here. :cheesy: The SSQV opens the first stage at < 5 psi, and the second at > 5 psi I believe.
 

·
Registered
Joined
·
801 Posts
Saab-Daniel said:
Well, I know of cars producing up to and over 500hp using just a single dump-valve. If it was me, I would just run 1 larger dumpvalve, and safe me the hassle of installing two, plus, in my oppinion, it dosn't look as nice with 2, but that might just be me, it is my 2 cents, at least... :)
Daniel.
Daniel get back in the box:p ....I like my two new valves, looks mean and race inspired, and SHINY! hahaha....but you're probably right for most people one high flow recirc valve would be perfect, I found the biggest restriction on the stock valve is the tiny port on the throttle....just welding a 1" connection on the charge pipe made all the difference in the world and made the stock valve audible but not loud like an atom valve....
 

·
Registered
Joined
·
2,879 Posts
Hehe, b5speed, looking forward to seeing a video/sound-clip of the new and improved... And still, I can't believe it's necessary with 2 valves... And no, can't believe that a bit of surge would have killed your turbo, my car drove without a valve for 19 years until I got if from my parents, the turbo wasn't killed by that, and still, you would dump A LOT of air still with 1 valve... Would be fun to calculate what a 1" opening can bleed during a very short period of time (while the bov is open) at a given pressure...
Daniel.
 
1 - 10 of 10 Posts
Top