AJI Posted December 9, 2006 Share Posted December 9, 2006 Just done a quick search but couldn't find the exact answer so here goes... I'm not the best when it comes to exaclty how everything works within an engine so if this question has been done to death (or if it is factually incorrect then I appologise. The stock Twin Turbo comes with a re-circ dump valve which instead of dumping the air to the atmosphere it puts it back infront of the turbos to help with pre-spool ready for the next session of acceleration. This helps to reduce turbo lag. But a dump to atmosphere valve will release the unused pressure into the engine bay and by doing this helps prevent turbo stall in that the pressure can not back-track through where it came from ie. back through the turbo. So helping to keep the turbos spinning and therefore not loosing RPM (of the turbo) between gear changes etc. So if both of these are true, which is the best way to go for a BPU TT Supra when you are to look at best turbo performance/response (and also preservation of turbo condition) ?? Keep the re-circ setup as stock... or remove stock system and install dump to atmosphere valve, based on performance alone? Link to comment Share on other sites More sharing options...
Chris and Alana Posted December 9, 2006 Share Posted December 9, 2006 I have a pretty much stock tt aprat from an apexi induction kit. I still had the stock dump valve and chaged it for a HKS SSQV. Since changing I didnt notice any difference in performance or spool up time between the atmospheric dump valve (HKS one) and the standard re-circulating one. I think its all down to personnal preference and whether or not you want the WHOOOOOSE noise or not. Im very happy with mine Link to comment Share on other sites More sharing options...
Bobbeh Posted December 9, 2006 Share Posted December 9, 2006 Mine is vent to atmosphere. TBH I dont think you're gonna notice much difference which way you have it. I predict the shouts of UK spec MAF sensor and all that suggesting you stick with re-circ, anyway I thought the stockers were good for aeound 450bhp anyway so theres no real need to change them. Link to comment Share on other sites More sharing options...
Jake Posted December 9, 2006 Share Posted December 9, 2006 In theory the MAF based Supes (VVTi/UK/US specs) should suffer problems with a VTA BOV but in reality they don't seem to notice the difference. Link to comment Share on other sites More sharing options...
AJI Posted December 9, 2006 Author Share Posted December 9, 2006 is this 'problem' the one where the engine sometimes stalls ? I drove a Supra with a vent to atmosphere valve on it a while back (not going to say who's it was ) but it nearly stalled on two occasions when I changed gear. So basically both versions of valves do their job of helping turbo performance in their own way... but neither is a leap forward from one or the other in either turbo response or turbo life. This is the answer I was hoping for to be honest. I wouldn't change from the stock setup to a vent to atmos' purely for the noise aspect... but if the dump to atmosphere valve meant that overall engine performance increased then I would do it. Link to comment Share on other sites More sharing options...
Bobbeh Posted December 9, 2006 Share Posted December 9, 2006 I was under the impression that it was the vent to atmos that helps with turbo life in preventing surge? Aron, what spec of Supra was the staller? Link to comment Share on other sites More sharing options...
wkdtime Posted December 9, 2006 Share Posted December 9, 2006 I was under the impression that it was the vent to atmos that helps with turbo life in preventing surge? Aron, what spec of Supra was the staller? MAF (Air measured before the turbo) based Supra's eg UK, Euro and US spec tend to be the stallers, the stalling problem is pretty much non existant when using a pull type BOV, e.g HKS SSQV rather than the usual Push type, e.g Blitz etc. Link to comment Share on other sites More sharing options...
Bobbeh Posted December 9, 2006 Share Posted December 9, 2006 Interesting you raised this push/pull theory, not heard that mentioned before. Good job I got the HKS SSQV then isnt it Link to comment Share on other sites More sharing options...
Chris and Alana Posted December 9, 2006 Share Posted December 9, 2006 Both help turbo life thats why there is one as standard. They just do different things. Standard re-circ = it dumps the excess boost back into the intake system, this only helps if you take your foot off and then back on straight away as you have a load of air ready to go back into the system. if you take your foot off or dip the clutch and change gear or take time in putting your foot back down the excess air just goes out the intake system (air filter) Atmospheric = does just the same apart from all the excess air is dumped into the atnmosphere (non into the intake) To be honest I dont think you would notice any difference. Any experts out there to correct anything...... Link to comment Share on other sites More sharing options...
wkdtime Posted December 9, 2006 Share Posted December 9, 2006 Both help turbo life thats why there is one as standard. They just do different things. Standard re-circ = it dumps the excess boost back into the intake system, this only helps if you take your foot off and then back on straight away as you have a load of air ready to go back into the system. if you take your foot off or dip the clutch and change gear or take time in putting your foot back down the excess air just goes out the intake system (air filter) Atmospheric = does just the same apart from all the excess air is dumped into the atnmosphere (non into the intake) To be honest I dont think you would notice any difference. Any experts out there to correct anything...... I'd say your pretty much on the ball there, but i can bet if Bobbeh resorts his UK back to a Re-circ his car will feel more responsive. Link to comment Share on other sites More sharing options...
Bobbeh Posted December 9, 2006 Share Posted December 9, 2006 My car feels no different since fitting, I would have noticed and swapped it back if it did. Link to comment Share on other sites More sharing options...
Chris and Alana Posted December 9, 2006 Share Posted December 9, 2006 Yeah the HKS SSQV is a better unit with its pull type technology. If you use a push type you have a spring that opens the piston at a set pressure. If you are at low boost and take the foot off the dump valve may not open and the excess air gets sent back through the turbos, as a result they stall and take time to spool again. it also doesnt do the turbos much good. I think im right there........ Link to comment Share on other sites More sharing options...
wkdtime Posted December 9, 2006 Share Posted December 9, 2006 My car feels no different since fitting, I would have noticed and swapped it back if it did. Bobbeh, try reverting back, it's only then you notice that there is/was a difference. When you go vent to atmos on any MAF based car you are innevitably running richer (Air lost throught to amos. is not accounted for) than you should be, which in turn robs you of some power. (Only a few horses TBH) (It's not a massive diference though:)) Link to comment Share on other sites More sharing options...
Bobbeh Posted December 9, 2006 Share Posted December 9, 2006 Surely I would have noticed going from one to the other to start off with if there was any difference - right? I think if I were BPU, your argument would have more credence. I think you'd more easily notice any delay/lag in spool. Link to comment Share on other sites More sharing options...
wkdtime Posted December 9, 2006 Share Posted December 9, 2006 Surely I would have noticed going from one to the other to start off with if there was any difference - right? I see what you mean, i too did not notice any difference when going from re-circ to atmos when i had an MR2 Turbo (Early rev1,2 MAF based), its only when the HKS failed on me that i had to revert back to re-circ but the plus side to this was that the car felt more responsive.... Lol it may just be placeabo:d Link to comment Share on other sites More sharing options...
R Black Posted December 9, 2006 Share Posted December 9, 2006 I think you've hit the nail on the head it is a Placebo, you can be fooled into thinking your going faster by Aural indicators. Link to comment Share on other sites More sharing options...
Bobbeh Posted December 9, 2006 Share Posted December 9, 2006 I wish by just fitting a BOV it would make me go faster.. but after 10k miles of driving without and 20k with I can safely say it hasnt Link to comment Share on other sites More sharing options...
Pete Posted December 10, 2006 Share Posted December 10, 2006 Relevant thread - http://www.mkivsupra.net/vbb/showthread.php?t=76991&highlight=bov [edit] that bug is really annoying. Just click the first underlined bit! Link to comment Share on other sites More sharing options...
AJI Posted December 10, 2006 Author Share Posted December 10, 2006 Thanks Pete, some good info on that thread. Bobbeh - the car I drove was a UK-spec BPU+ (I think), it was around the 450-500bhp mark. It was a little scary when down changing as the rear wheels would momentarily lock up and screech as they re-started the engine with the gears (as in a jump start). Link to comment Share on other sites More sharing options...
Wez Posted December 10, 2006 Share Posted December 10, 2006 It was a little scary when down changing as the rear wheels would momentarily lock up and screech. Are you sure thats the same problem? My J-Spec doesnt stall but when driving spiritedly I get chirps from the rear tyres when going down the box at speed. Link to comment Share on other sites More sharing options...
Bobbeh Posted December 10, 2006 Share Posted December 10, 2006 Yeah that doesnt sound like something caused by the BOV, maybe the revs not matching when you're braking/changing down a gear for the speed you were going? Link to comment Share on other sites More sharing options...
AJI Posted December 10, 2006 Author Share Posted December 10, 2006 nah, it wasn't due to revs difference... it was happening whilst I was slowing down from about 60 in 5th.... so the revs at this stage were not high up the scale. Then changed to 4th and slowly let the clutch out (as it was not my car I wasn't driving it hard.... just wanted to get a feel for the suspension set up)....; when the clutch was in by the way, the engine noise went very quiet, warning triangle flashed on for a second... and when the clutch came back out the rear wheels screeched briefly and the engine revs/noise picked up again. Same thing happened in the change from 4th to 3rd. This could easily be a totally different issue with stalling to what the usual stall problem is with BOVs. Just that this in the only occasion I've been in when the engine has felt like it stalled during driving a Supra, and just assumed this is what you guys were talking about when referring to BOVs and stalling. I think I'll stick with the stock re-circ system anyhow. There is a good saying... "if it ain't broke, don't fix it". Link to comment Share on other sites More sharing options...
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