Si_s Supe Posted June 28, 2011 Share Posted June 28, 2011 As I've spoken of before, I plan to end up BPU but my car is stock ATM. I've just bought a 3" 2nd Decat and am probably going to end up buying a Nur Spec R. My question is, can I get away with fitting just these bits for now and keeping the other cat in place, or will removing only one cat still cause the Jspec turbos to over speed?? Quote Link to comment Share on other sites More sharing options...
Homer Posted June 28, 2011 Share Posted June 28, 2011 That answer will depend on how much boost you are planning to make. If it's up to 1 bar you should be fine with the 1st cat in place. Above that at it's really not an ideal setup since the 1st cat is the most restrictive. It'll increase the EGT's considerably if you raise boost above 1 bar. If you plan on keeping one of the stock cats it's best practice to replace the 1st one with a decat rather than the 2nd. Replacing only the first one should should be okay to 1.1 bar, maybe a bit more if you have low intake temps. Alternatively if you only want to get partial BPU power and keep boost below 1 bar it should be fine to keep the 1st cat in place until you have time to replace that one with a decat. You won't get the full BPU torque until both cats are replaced or the 2nd is replaced with a sports cat. Quote Link to comment Share on other sites More sharing options...
Si_s Supe Posted June 28, 2011 Author Share Posted June 28, 2011 Alternatively if you only want to get partial BPU power and keep boost below 1 bar it should be fine to keep the 1st cat in place until you have time to replace that one with a decat. You won't get the full BPU torque until both cats are replaced or the 2nd is replaced with a sports cat. Yes, the 2nd Decat will only be a temporary measure until I can afford the other Decat, boost controller and AFR gauge. That brings me to another question! I have a Defi boost gauge with the Defi Link control module (these are yet to be fitted) Does anyone know if Defi do an AFR gauge to work with this system?? Quote Link to comment Share on other sites More sharing options...
Guigsy Posted June 28, 2011 Share Posted June 28, 2011 Defi don't do an afr. I've got the defi system but have an aem afr. You could get a defi egt guage. But it's not as usefull. Afr is more important from what ive heard Quote Link to comment Share on other sites More sharing options...
Si_s Supe Posted June 28, 2011 Author Share Posted June 28, 2011 Defi don't do an afr. I've got the defi system but have an aem afr. You could get a defi egt guage. But it's not as usefull. Afr is more important from what ive heard Damn them!! How ghey!!! Quote Link to comment Share on other sites More sharing options...
Homer Posted June 28, 2011 Share Posted June 28, 2011 Yes, the 2nd Decat will only be a temporary measure until I can afford the other Decat, boost controller and AFR gauge. That brings me to another question! I have a Defi boost gauge with the Defi Link control module (these are yet to be fitted) Does anyone know if Defi do an AFR gauge to work with this system?? Make sure your boost isn't getting above 0.9-1 bar, this is especially important in the hot weather we've been having lately (in colder weather 1 bar at 30degrees will be 1.2 bar at 5 degrees). As Guigsy mentioned, the Defi link won't add an AFR, though with a 1st cat in place the EGT's are a little more important to watch. If you can only add one gauge in the interim between this and full BPU you'd do well to add the EGT over AFR. Personally I wouldn't decat without either an AFR or EGT gauge, otherwise you have nothing to monitor what's going on in the engine. Quote Link to comment Share on other sites More sharing options...
dive_popo Posted June 29, 2011 Share Posted June 29, 2011 I have one question about that aswell, when removing the cats on jspec do you have to use the restrictor ring if having a boost controller ?? Quote Link to comment Share on other sites More sharing options...
ManwithSupra Posted June 29, 2011 Share Posted June 29, 2011 I have one question about that aswell, when removing the cats on jspec do you have to use the restrictor ring if having a boost controller ?? Yes, a boost controller will only increase boost not decrease it. You will need a restrictor ring. Quote Link to comment Share on other sites More sharing options...
Si_s Supe Posted June 29, 2011 Author Share Posted June 29, 2011 I have one question about that aswell, when removing the cats on jspec do you have to use the restrictor ring if having a boost controller ?? This is a very good question! I plan on running a 3" system all the way through with a boost controller as personally it seems odd to me having 3" exhaust with 2.5" decats and even smaller restrictor rings!? Surely have the nice free flowing 3" system then use a BC to restrict the boost! Quote Link to comment Share on other sites More sharing options...
gavin.starr Posted June 29, 2011 Share Posted June 29, 2011 Electronics can fail, a restrictor ring is just a flange basicly so not much to go wrong. I would personaly put the restrictor ring in place as a just incase precaution, and why else would some one have gone to the effort of makeing them? for what it costs its worth it. Quote Link to comment Share on other sites More sharing options...
ManwithSupra Posted June 29, 2011 Share Posted June 29, 2011 You cant restrict boost with a boost controller, only increase it. Quote Link to comment Share on other sites More sharing options...
dive_popo Posted June 29, 2011 Share Posted June 29, 2011 cheers guys ! thanks for the info, I was wondering why my boost is jumping to 1.5b sometimes... and what is different between euro spec and jspec ? nobody use restrictor ring on euro spec... Quote Link to comment Share on other sites More sharing options...
ManwithSupra Posted June 29, 2011 Share Posted June 29, 2011 (edited) cheers guys ! thanks for the info, I was wondering why my boost is jumping to 1.5b sometimes... and what is different between euro spec and jspec ? nobody use restrictor ring on euro spec... 1.5bar is really pushing jspecs mate, most people only go up to 1.2bar max.... 1.5 will shorten the life dramatically if not pop them straight away. IIRC the Euro spec (UK) has a larger wastegate that can handle the higher boost, then you just need a boost controller to increase the boost. Euro spec cars also have steel blades as opposed to the Jspec's ceramic. The steel blades can handle more boost up to 1.4bar but they are slightly slower in spooling. Really you don’t want to be pushing Jspecs past 1.2 bar any higher and you increase the chances the blades will shatter. Edited June 29, 2011 by ManwithSupra Spelling (see edit history) Quote Link to comment Share on other sites More sharing options...
Josh Posted June 29, 2011 Share Posted June 29, 2011 cheers guys ! thanks for the info, I was wondering why my boost is jumping to 1.5b sometimes... and what is different between euro spec and jspec ? nobody use restrictor ring on euro spec... Have a look at the "BPU" page. UK spec turbos have steel turbines rather than ceramic (J spec) and they have a larger wastegate so the boost doesn't rise as the restriction is removed. Quote Link to comment Share on other sites More sharing options...
Thorin Posted June 29, 2011 Share Posted June 29, 2011 cheers guys ! thanks for the info, I was wondering why my boost is jumping to 1.5b sometimes... and what is different between euro spec and jspec ? nobody use restrictor ring on euro spec... euro/UK spec don't need a restrictor ring. Make sure you read the BPU article. Quote Link to comment Share on other sites More sharing options...
dive_popo Posted June 29, 2011 Share Posted June 29, 2011 thanks guys, I knew about the ceramic vs. steel blades, but didnt knew about the wastegates I have a boost controller set to 1.15b but sometimes the boost jumps to 1.5b and imediately is cut back to 1.15 or 1.2 I can't get a stable boost, it is always playing between 1.1 and 1.2b when pushing hard... Quote Link to comment Share on other sites More sharing options...
mikeyb10supra Posted June 29, 2011 Share Posted June 29, 2011 (edited) Make sure your boost isn't getting above 0.9-1 bar, this is especially important in the hot weather we've been having lately I disagree, mine was setup for 4 years like this and never missed a beat. I had the first cat in place and 2nd cat removed and it sat happily at 1.1bar all day long with EGT's slightly hotter than usual but nothing to worry about. Scotty71 now owns my car and its still going strong Edited June 29, 2011 by mikeyb10supra (see edit history) Quote Link to comment Share on other sites More sharing options...
Si_s Supe Posted June 29, 2011 Author Share Posted June 29, 2011 You cant restrict boost with a boost controller, only increase it. Ah...gotcha!! How about using a restrictor in the vac pipes? I know the restrictor ring in the exhaust is an easy and tried & tested route to take, but having a restrictor ring in the exhaust is going to create alot of turbulent air which could be backing up and stalling the blades, defeating the object of a free flowing system. Quote Link to comment Share on other sites More sharing options...
ManwithSupra Posted June 29, 2011 Share Posted June 29, 2011 A restrictor ring does not create so much pressure as to stall the turbo. However it does create back pressure to stop the turbo from spinning too fast. If you want a totally free flowing system then you can either change your Jspec Tubs, Manifold etc to UK or get a big single. I have never heard of putting a restriction on the VAC pipes before. Quote Link to comment Share on other sites More sharing options...
Si_s Supe Posted June 29, 2011 Author Share Posted June 29, 2011 Nice one, thanks for clarifying. Bearing in mind I've got a 3" 2nd Decat and 3" cat back to go on, most the 1st decats I've seen are only 2.5". What are the pros and cons between have a 2.5" or 3" 1st Decat?? Quote Link to comment Share on other sites More sharing options...
mikeyb10supra Posted June 29, 2011 Share Posted June 29, 2011 Ah...gotcha!! but having a restrictor ring in the exhaust is going to create alot of turbulent air which could be backing up and stalling the blades Wont make a jot of difference......what about the cats when they are in there I even went as far as removing the stock recirc on mine and still just as responsive Quote Link to comment Share on other sites More sharing options...
RZtwin Posted February 4, 2012 Share Posted February 4, 2012 Is your Supra a J-Spec Supra? Also you say your EGT's went up slightly. What exactly is "Slightly" and where should the norm be for a stock TT RZ? Thank You for the info! I disagree, mine was setup for 4 years like this and never missed a beat. I had the first cat in place and 2nd cat removed and it sat happily at 1.1bar all day long with EGT's slightly hotter than usual but nothing to worry about. Scotty71 now owns my car and its still going strong Quote Link to comment Share on other sites More sharing options...
ashbuster Posted February 4, 2012 Share Posted February 4, 2012 (edited) You cant restrict boost with a boost controller, only increase it. when i had a problem with my scooby overboosting i fitted a manual boost controller (the ball and spring one) and lowered the boost down a couple of psi to stop the fuel cut. also bud on the scoobys they have a restrictor pill in one of the vac lines, like a little pill shape metal thing with a hole drilled through Edited February 4, 2012 by ashbuster (see edit history) Quote Link to comment Share on other sites More sharing options...
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