leelbuk Posted June 19, 2006 Share Posted June 19, 2006 I am new to turbos in general so there could be a stupidly simple answer to my problem but please bear with me! I have done a lot of reading and searching to try and resolve it but I can't. I have a 94 j-spec TT and it has both cats removed and a restrictor ring as well as a Blitz NUR spec exhaust system. When boosting my Boost Guage is only showing 12 PSI max boost which, If I work it out, is 0.85 Bar? (1 Bar ~ 14 PSI I think if I can recall from my Chemistry Degree) I have read that 0.85-0.9 Bar is about standard boost but I have also read that Twin decat, restrictor ring and full s/s exhaust are the 1st few steps in going BPU and should end up increasing a j-specs boost pressure to around 1.1 - 1.2 Bar. Is my boost guage faulty or is the car not boosting properly? Could it be that the current restrictor ring is limiting it to 0.85bar? Please help, I am a little bit stuck for ideas... Quote Link to comment Share on other sites More sharing options...
Soonto_HAS_soop Posted June 19, 2006 Share Posted June 19, 2006 Each car reacts differently to a restrictor ring, could be too small, mine had to come out several times to get the right diameter. Quote Link to comment Share on other sites More sharing options...
Suprasteve Posted June 19, 2006 Share Posted June 19, 2006 also the heat will reduce boost too compared to the winter. sounds about right but as already said it depends on the ring you have fitted. either get a bigger ring or fit a boost controller to up it. Quote Link to comment Share on other sites More sharing options...
wkdtime Posted June 19, 2006 Share Posted June 19, 2006 also the heat will reduce boost too compared to the winter. sounds about right but as already said it depends on the ring you have fitted. either get a bigger ring or fit a boost controller to up it. The heat wouldnt bring it down to 0.85 Bar, first thing i would do mate is take the restrcitor ring off completely and take it for a spin, and in third gear carefully plant the throttle and watch the boost gauge, if it starts to go towards 1.2+ then you need a bigger restrictor ring or EBC, if the boost remains the same i would have thought that you might have a boost leak some where. Can you feel number 2 coming on? What did it boost to before? or have you bought it like this? Quote Link to comment Share on other sites More sharing options...
leelbuk Posted June 19, 2006 Author Share Posted June 19, 2006 WOW 1st off, thanks for the replies. The car is as I bought it, only had it a month. I can definately feel number 2 come on, the car really pulls more, sometimes looses traction if not careful and the exhaust changes tone at 4000RPM. Also boost guage reads higher when second turbo comes on. I would think the boost guage is correct as its defo not seeing more than 1 bar as fuel cut isn't cutting in (I haven't got an FCD yet). I'll try taking the restrictor ring off and see if it makes a difference i.e fuel cut should come in. Just out of interest, where abouts in the exhaust is the restrictor ring fitted? And where do I buy another one if it is too small? I may go single turbo next year if BPU isn't enough for me so would a boost controller be more sensible as it could be used for controlling boost on a single turbo? Many thanks so far. Quote Link to comment Share on other sites More sharing options...
Suprasteve Posted June 19, 2006 Share Posted June 19, 2006 The heat wouldnt bring it down to 0.85 Bar ok i worded it badly. what i meant is in the cold air it would naturally boost higher, however now the air is hot and humid it may not boost as high. The ring may have been set to 1 bar for the cold weather ? For example mine fluctuates between 0.9 - 1.2 bar depending on how hot it is. I have to adjust the boost controller settings to compensate. Quote Link to comment Share on other sites More sharing options...
Mcgoo Posted June 19, 2006 Share Posted June 19, 2006 Mine was bpu'd when it was colder and had a 1.1 restrictor. It peaked at 1.1 and would settle about 1.0. Since the weather has warmed it peaks at 0.95 and settles at 0.85. yours sounds pretty similar to me. I think a boost controller or an intercooler may be required. You could open up your restrictor ring(normally found between the first and second decat pipes) but you may get over 1.2 in the winter which isn't what ya want if ya want your turbos to last. Quote Link to comment Share on other sites More sharing options...
Homer Posted June 19, 2006 Share Posted June 19, 2006 For example mine fluctuates between 0.9 - 1.2 bar depending on how hot it is. I have to adjust the boost controller settings to compensate. I'm with you on this. I get fuel cut at 1.25bar in the winter, but in the warm weather never see above 0.9bar. Quote Link to comment Share on other sites More sharing options...
leelbuk Posted June 19, 2006 Author Share Posted June 19, 2006 Thanks for straightening that out for me guys, I think I'll probably go down the Boost controller route then and was already planning on getting a FMIC when insurance allows (still a baby at 23 as far as insurance goes:rolleyes: ) and when money allows, got to buy 2 new rear rubbers soon and some car tax Til then I will see how it goes when the weather cools down, which I hope isn't anytime soon! Quote Link to comment Share on other sites More sharing options...
steve single Posted June 19, 2006 Share Posted June 19, 2006 I believe the internal diamiter of a 1.2bar restrictor ring is 55mm. i believe:cool: Quote Link to comment Share on other sites More sharing options...
leelbuk Posted June 19, 2006 Author Share Posted June 19, 2006 Thanks for that steve, will get it out and have a measure oh err... Quote Link to comment Share on other sites More sharing options...
wkdtime Posted June 19, 2006 Share Posted June 19, 2006 ok i worded it badly. what i meant is in the cold air it would naturally boost higher, however now the air is hot and humid it may not boost as high. The ring may have been set to 1 bar for the cold weather ? For example mine fluctuates between 0.9 - 1.2 bar depending on how hot it is. I have to adjust the boost controller settings to compensate. Are you fully-decatted? Quote Link to comment Share on other sites More sharing options...
wkdtime Posted June 19, 2006 Share Posted June 19, 2006 I'm with you on this. I get fuel cut at 1.25bar in the winter, but in the warm weather never see above 0.9bar. Homer do you use an EBC to componsate or just leave it be? I havent notice such a drop in boost in the warmer weather, may be a differnce of 0.1 bar, i do have a FMIC, is yours still the stock SMIC? if so that would exaplin the drop. Quote Link to comment Share on other sites More sharing options...
Suprasteve Posted June 20, 2006 Share Posted June 20, 2006 Are you fully-decatted? yep I also have no ring fitted ! unusual i know but i'm not alone theres others too that don't over boost when fully decatted. Quote Link to comment Share on other sites More sharing options...
captainchaos Posted June 21, 2006 Share Posted June 21, 2006 My car was running 1.2 bar when i first got the car with adding a front mount intercooler on its around the 1.3 mark does this sound right ? Quote Link to comment Share on other sites More sharing options...
Jake Posted July 2, 2006 Share Posted July 2, 2006 leelbuk, Did you get anywhere with this problem? Me and Jonboy have spent this afternoon BPU'ing his J-spec 6sp with Whifbitz decats and restrictor ring, Walbro pump, NGK BCPR7ES plugs gapped to 0.8mm and a HKS FCD but for some reason his car doesn't seem to be making anymore boost than it did before. He's only getting about 0.8bar. Quote Link to comment Share on other sites More sharing options...
wkdtime Posted July 2, 2006 Share Posted July 2, 2006 I dont know if this has anythig to do with post BPU problems, but when people say that you NEED a ristrictor ring when going double decat on a j spec i have to say this is not entirely true, i know a few members on this forum who have gone double decat on j specs and have seen boost at around 0.9-1.0bar boost with out using a restrictor ring and have not suffered from over boost, all i can suggest is to first try with out the restrictor ring and if the car overboosts then slap one in. The summer temps should not make a major difference to boost if your IC is healthy regardless of what people say, at most it may drop by 0.1bar any more than you have an inefficient IC. Some people just seem to follow the flock on this forum and dont talk from experience be it there own or others. Quote Link to comment Share on other sites More sharing options...
Jake Posted July 2, 2006 Share Posted July 2, 2006 Surely if it isn't boosting over 1.0 bar with no cats there a problem somewhere. Some people just seem to follow the flock on this forum and dont talk from experience be it there own or others.Thanks but I'm not exactly new to Supras I've decatted a few TTs and always needed a restrictor ring before. Quote Link to comment Share on other sites More sharing options...
leelbuk Posted July 3, 2006 Author Share Posted July 3, 2006 I haven't gone any further with it yet no as I have yet to uprate my fuel pump with a Walbro item yet and have only just changed the oil etc and I've just purchased an FCD. I didn't want to try taking the restrictor ring out before I've made sure the car is in tip top shape first, Plus I'm taking it to Lucifers Bristol meet and hope to get it on the rollers so I know what the car is currently producing. How can you tell how bad your IC really is? I've had a look at it and it looks normal apart from a few broken fins. The car has covered 70,000 miles so is this normal wear and tear for a standard SMIC? I will be getting a FMIC as I said earlier in my posts anyway. How do I check for boost leak? I don't have any experience really with turbos but hopefully interpro in bristol might be able to do a breif health check and the rolling road may show up problems if I have any. PS: 1 last thing, is there an easier way to get at the oil filter on the Supra? I had to take the battery out to get at it. I reckon Toyota forgot to decide where to put the oil filter during development, and then decided to "just stick it in that small gap there mate!" at the end! Quote Link to comment Share on other sites More sharing options...
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