simbasupra Posted January 2, 2008 Share Posted January 2, 2008 Hi, was just wondering if anyone had fitted a dump valve to a UK/VVTi Supra? I have a UK Supra and was thinking of getting one, so searched the forum and found this quote on the explanation of a dump valve thread. "If you have a UK car, an atmospheric BOV can confuse the ECU because they use a MAF airflow sensor which is ahead of the BOV." If anyone has fitted one to a UK/VVTi spec how did you get round this? Link to comment Share on other sites More sharing options...
RobSheffield Posted January 2, 2008 Share Posted January 2, 2008 I believe you can get recirculation kits for some BOVs, like the HKS one. Link to comment Share on other sites More sharing options...
JustGav Posted January 2, 2008 Share Posted January 2, 2008 Hi, was just wondering if anyone had fitted a dump valve to a UK/VVTi Supra? I have a UK Supra and was thinking of getting one, so searched the forum and found this quote on the explanation of a dump valve thread. "If you have a UK car, an atmospheric BOV can confuse the ECU because they use a MAF airflow sensor which is ahead of the BOV." If anyone has fitted one to a UK/VVTi spec how did you get round this? The car already has a dump valve, I am assuming you mean you want the dump valve sound. Recirculation is the proper way to do it, a few people have gone atmospheric without noticeable issues, I however am not a fan. Link to comment Share on other sites More sharing options...
Nic Posted January 2, 2008 Share Posted January 2, 2008 HKS do a recirculation valve (sold separately) for their SSQV BOV, this replaces the standard fin in the BOV as seen in this pic http://www.hks-power.co.jp/products/blow_off/sqv/img/sqv_n.gif HKS also do an electronic gizmo called the EIDS (Electronic Idling Stabilizer), which is suppose to prevent the problem with vent to atmosphere BOV's on cars with MAF sensor. http://www.hks-power.co.jp/products/blow_off/sqv/img/option5.jpg I can supply both these if needed. Link to comment Share on other sites More sharing options...
styggen82 Posted January 3, 2008 Share Posted January 3, 2008 Hi, was just wondering if anyone had fitted a dump valve to a UK/VVTi Supra? I have a UK Supra and was thinking of getting one, so searched the forum and found this quote on the explanation of a dump valve thread. "If you have a UK car, an atmospheric BOV can confuse the ECU because they use a MAF airflow sensor which is ahead of the BOV." If anyone has fitted one to a UK/VVTi spec how did you get round this? I`ve fitted one on my vvti, and the only thing I have experienced is slight fuel in the exhaust. but my afr is perfect under load, rich when I step off the trottle but no stalling at all. used it for 6 months now and still works... but where does the air go when you use stock bov? I know that all the compressed air in the system is vented back to the intake but some of it must go back out through the air filter? because of the volume of it?or am I completly wrong? Link to comment Share on other sites More sharing options...
simbasupra Posted January 3, 2008 Author Share Posted January 3, 2008 The car already has a dump valve, I am assuming you mean you want the dump valve sound. Recirculation is the proper way to do it, a few people have gone atmospheric without noticeable issues, I however am not a fan. Thanks for the feedback everyone. Just to clarify a aftermarket recirculation type dump valve wont give me that "dump valve sound " will it? So to do it correctly and still have that "dump valve sound" i would need a atmospheric type dump valve with a HKS EIDS like Nic is selling? Link to comment Share on other sites More sharing options...
D8MOA Posted January 3, 2008 Share Posted January 3, 2008 Thanks for the feedback everyone. Just to clarify a aftermarket recirculation type dump valve wont give me that "dump valve sound " will it? So to do it correctly and still have that "dump valve sound" i would need a atmospheric type dump valve with a HKS EIDS like Nic is selling? that sounds the general idear.... try it without the hks gizmo and see how it goes..... have seen cars with afm and DV's with no problems Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 3, 2008 Share Posted January 3, 2008 I wrote this on a Skyline forum about 12 years ago, may help, FWIW. The following is based on my Skyline experience, with air usage measured by air flow meters before the turbos. It is not applicable to cars that soley use a MAP sensor and throttle angle for air measurement . To recap I put in a bigger intercooler and the standard Skyline duct that runs across the lower front of the car taking dumped air from the 2 blow off valves to the intake between the air flow meters and the twin turbo inlets was masking air exiting the lower 4 rows of the new IC. Having spent a good deal of money on this item it pained me to see some of effectively blanked off. So I decided to blank the inlet off altogether where the cross pipe entered the turbo inlet ducting, remove the cross pipe and vent to atmosphere. The dump valves were being held open at idle by the idle vacuum level, so after ages of pondering i made a set up of solenoids to control when vacuum was applied to the dump valves. This set up worked perfectly. *HOWEVER* a much more serious problem occurred, which any similarly inducted turbo car will potentially suffer if the boost air is dumped to atmosphere rather than as standard into the air intakes after the AFM (s). On the overrun, after a period of boost running, the standard set up will recirculate the excess boost back into the turbos, through the IC, and back through the dump valves to the turbo inlet again until the turbos inertia has slowed them to the point of little or no boost. The AFM's do not see any more air entering the engine, as it is being recirculated. However, when we dump to atmosphere, that air is lost from the system and the turbos draw in fresh air via the AFM (s). This causes the engine to go mad rich, as the throttles are closed and no fuel is really needed. Hence the black smoke seen on the overrun after my mods. Worse still was a noticeable but very short period of detonation when coming hard back on the throttle. This puzzled me totally, then it dawned. As the fuel system started working normally again the Lambda sensor "caught up" with what was happening, saw a very overly rich mixture, and shut down the injector pulse width, creating a very lean mixture, causing a brief, but very dangerous period of detonation! I spent the afternoon and evening making new bracketry for the IC, new hoses and adaptors and shifting the IC forward that critical 40 mm or so, enabling me to fit the original moulded duct from the BOV's behind the IC without blocking it. Quite a lot of work and fabrication... However, the mod I was planning could well have caused damage, and is certainly something to be very aware of if one has a similar AFM pre turbo set up changed to dump boost to atmosphere. The type of BOV matters not, it's the fact that the air no longer re circulates but is lost from the system, confusing the AFM (s) into thinking the engine is wanting more air/fuel mixture. An oscilloscope on the O2 sensors confirmed what was happening. We live and learn, often the hard way, but in this case not as hard a lesson as it might have been. I hope this helps, I searched the web long and hard for references to BOV problems, and failed to find any details of why dumping to atmosphere on none MAP sensor systems, that aren't mapped for this, is potentially dangerous. Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now