How it works: turbo/mods
07-26-2005, 09:53 PM
#18
Drifting
Thread Starter
Originally Posted by streckfu's951
You have to scroll down farther. Look under 'Model Specific Forums'.
Good to know.
07-27-2005, 04:18 AM
#19
Drifting
Thread Starter
Originally Posted by theedge
Recirculation valves go between the outlet side and the inlet side of the turbo. They release the compressed air back into the J Pipe that goes from the Air Flow Meter to the turbo inlet. It opens up and allows air to flow when you lift off the throttle.
edit: maybe not, it just sends it to go through the turbo again, what would be the point of this?
Also, does anyone have any pics of the 951 exhaust set up? I assume the crossover pipe goes from the wastegate to the turbo, and the downpipe goes form the turbo to the exhaust past the wastegate?
07-28-2005, 11:57 PM
#20
Drifting
Thread Starter
I did the venturi delete, CV delete, but left my ISV in. Should I (or could I) remove that as well? I deleted mine with a Laust Pederson vaccuum manifold, Lindsey vaccuum kit, and an EBC.
07-29-2005, 12:47 AM
#23
Campeck Rulez
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he deleted the mess under his intake. (whatever cv is) but left his idle stabilizer valve in. shoul dhe remove that as well? he deleted the cv and venturi with a cool little thing that a rennlister makes that goes on the intake and has spots fro lots of vacuum hoses to run the various engine parts, a lindsey vacuum kit (hoses),
and an electronic boost controller.
and an electronic boost controller.
07-29-2005, 01:05 AM
#25
Addict
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OK, the Doc is in, lol...
Recirc valve. When you are at full boost flowing aprx 500 cubic foot per min of air(vs aprx 320cfm NA) and let off the throttle, the air has to go somewhere. The air will back up against the throttle plate and reverse flow against the turbo. This, in some cases, will... wear the thrust bearings in the turbo, possible brake the shaft in the turbo in extreme cases or more commonly, just slow the turbo to an ineffective speed. When shifting this will happen every time, the result, you have to respool the turbo(bring it back up to speed) resulting in unacceptable lag in every shift. The recirc valve allows the pressurised air to be releived and flow freely in a closed loop inside the AFM(air flow meter). A blow off valve(BOV) does the same only it releives the pressure to the engine bay outside the intake system. This is not a good idea for cars running an AFM or MAF(mass air flow) due to the air being metered as it come in and then being dumped outside the system. Mormally it just causes a stumble when getting back into the throttle due to the air reading being incorrect.
Recirc valve. When you are at full boost flowing aprx 500 cubic foot per min of air(vs aprx 320cfm NA) and let off the throttle, the air has to go somewhere. The air will back up against the throttle plate and reverse flow against the turbo. This, in some cases, will... wear the thrust bearings in the turbo, possible brake the shaft in the turbo in extreme cases or more commonly, just slow the turbo to an ineffective speed. When shifting this will happen every time, the result, you have to respool the turbo(bring it back up to speed) resulting in unacceptable lag in every shift. The recirc valve allows the pressurised air to be releived and flow freely in a closed loop inside the AFM(air flow meter). A blow off valve(BOV) does the same only it releives the pressure to the engine bay outside the intake system. This is not a good idea for cars running an AFM or MAF(mass air flow) due to the air being metered as it come in and then being dumped outside the system. Mormally it just causes a stumble when getting back into the throttle due to the air reading being incorrect.
07-29-2005, 01:12 AM
#26
Addict
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Venturi, it's basicly a syphon, it accellerates the vaccume to create more of it for the heater and brake booster. I deleted the venturi tube and related plumbing.
CV- cycling valve. Porsche used the CV to help the computer control boost. The WG(wastegate) is set to 7psi or there about, the computer will divert the boost signal back to the intake untill it reaches the programmed boost setting and then pulsing it to regulate the WG open to keep the boost under control. The CV is just a pneumatic switching valve. one line in and two options for out. It either goes back to the J-boot(intake before the turbo) or to the WG. Also the computer uses the CV in case of detonation(preignition or spark knock) detected by the Knock sensor to pull the boost down to reduce or eliminate detonation.
CV- cycling valve. Porsche used the CV to help the computer control boost. The WG(wastegate) is set to 7psi or there about, the computer will divert the boost signal back to the intake untill it reaches the programmed boost setting and then pulsing it to regulate the WG open to keep the boost under control. The CV is just a pneumatic switching valve. one line in and two options for out. It either goes back to the J-boot(intake before the turbo) or to the WG. Also the computer uses the CV in case of detonation(preignition or spark knock) detected by the Knock sensor to pull the boost down to reduce or eliminate detonation.
07-29-2005, 01:17 AM
#27
Addict
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ISV, idle stabalizer valve. This is a valve that introduces air to the intake(after the throttle body) to help control the idle under increased load like the AC being on or idleing the clutch out.
07-29-2005, 02:02 AM
#29
Addict
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I beleive the early cars had an auxilliary air valve and not the ISV. Same function, different tho. The ISV was variable, the AAV was on or off IIRC.