Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum - View Single Post - Push through or Pull through MAFS on SR20det

Jsquared · 03-12-2003, 12:41 AM

NO. the 944 turbo comes with a bypass valve stock, as does nearly every single turbo car made by anyone. the Silvia also comes stock with a bypass valve. a blowoff valve is just a bypass valve vented to atmosphere instead of rerouted back into the intake between the MAFS and turbo inlet. running a vented-to-atmosphere BOV on an S13 SR is no different than running the OEM BPV and venting it to atmosphere on a 944turbo (aka "951" in Porsche-speak) which is no different than a BOV venting to atmosphere on an Eclipse turbo which is no different than a BOV venting to atmosphere on an RX-7... get the drift? (no pun intended)

pop-off valves are completely different. a BPV/BOV prevents compressor surge to protect the turbo when the throttle closes under boost (as you know already)... a pop-off valve merely releases pressure when a car overboosts, mainly as a back-up for the wastegate in case the wastegate for some reason malfunctions and can't keep the boost down (which really doesn't make any sense because a wastegate is much more effective than a pop-off valve at regulating boost pressure). the only modern vehicle you should see a pop-off valve on is a CART Champ Car, and the governing body uses these to prevent teams from "turning up the knob" on the wastegate control and getting more boost, and thus more power, than other teams (the pop-offs are distributed by the governing body and are all set to the same psi).

03-12-2003, 12:41 AM	#21
Jsquared Zilvia Junkie Join Date: Feb 2003 Location: Raleigh, NC//Charlotte, NC Age: 42 Posts: 503 Trader Rating: (0)	NO. the 944 turbo comes with a bypass valve stock, as does nearly every single turbo car made by anyone. the Silvia also comes stock with a bypass valve. a blowoff valve is just a bypass valve vented to atmosphere instead of rerouted back into the intake between the MAFS and turbo inlet. running a vented-to-atmosphere BOV on an S13 SR is no different than running the OEM BPV and venting it to atmosphere on a 944turbo (aka "951" in Porsche-speak) which is no different than a BOV venting to atmosphere on an Eclipse turbo which is no different than a BOV venting to atmosphere on an RX-7... get the drift? (no pun intended) pop-off valves are completely different. a BPV/BOV prevents compressor surge to protect the turbo when the throttle closes under boost (as you know already)... a pop-off valve merely releases pressure when a car overboosts, mainly as a back-up for the wastegate in case the wastegate for some reason malfunctions and can't keep the boost down (which really doesn't make any sense because a wastegate is much more effective than a pop-off valve at regulating boost pressure). the only modern vehicle you should see a pop-off valve on is a CART Champ Car, and the governing body uses these to prevent teams from "turning up the knob" on the wastegate control and getting more boost, and thus more power, than other teams (the pop-offs are distributed by the governing body and are all set to the same psi). Last edited by Jsquared; 03-12-2003 at 12:44 AM..