Kranz Posted May 18, 2007 Author Share Posted May 18, 2007 Did you mention the UK steel turbos have a greater A/R than J-Spec? Trying to get my head round this, guess i should search for some stats but as you guys know already, is this purely because the J-Specs have a larger radius of exh turbine housing than UK, but have the same size entrance orifice as a UK or does the UK exh turbine housing have a larger entrance orfice as well as smaller housing radius than J-Spec? I wondering if the fast spooling of the J-Spec was pure influenced by it's A/R or does having a ceramic turbine give lower ineria than steel. i.e. Does having the lower inertia ceramic turbine increase it's chances of overspeeding when trying to get more than stock boost from them or is it all down to the A/R? Also is it correct that if this ceramic turbine is replaced with steel the turbo becomes laggier? If this is the case is this down to an increase or decrease of inertia and does it's characteristic to overspeed reduce which i would have thought would reinstate some form of balance in the turbine shaft or is the force/friction applied along the shaft changed so drastically the the original lubrication can't cope and chances of turbo failure on J-Spec with steel exh turbine marriage. Hope that makes sense, I've confused myself now UK turbos have a turbine A/R of 0.53... but have turbine size of 52mm major and 44mm minor. I don't know what the inlet diameter is?? J spec is an A/R of 0.35 and turbine size of 59.8mm and 48mm and an inlet diameter of 36mm. I think the smaller A/R of the J spec is partially due to the bigger radius, but not sure how much. Anyone know the figures? So the UK A/R is bigger than the J spec, but the turbine is smaller! This is a bit confusing, but what I think the purpose of this is so UK spec can make more power and J spec can spool up fast. The small A/R on the J spec will spool up ultra quick and also the light weight ceramic turbine (even though its bigger than UK spec) will accelerate faster (i.e. spool up) for a given air flow. At steady state conditions a ceramic turbine would have no advantage over a steel turbine. If the J spec turbine is replaced with a steel one the turbo will take slightly longer to come onto boost during acceleration, but will be able to produce more boost due to the greater reliability of the steel turbine at high rpm's (needed for boost above stock levels). Its overspeed problem will be only very slightly different as inertia does not have much affect at all on turbine speed at steady state conditions. Anyone got the figures to explain the A/R of the UK turbine? I know Tricky Ricky recently fitted some. Quote Link to comment Share on other sites More sharing options...
Stevie Boy Posted May 18, 2007 Share Posted May 18, 2007 UK turbos have a turbine A/R of 0.53... but have turbine size of 52mm major and 44mm minor. I don't know what the inlet diameter is?? J spec is an A/R of 0.35 and turbine size of 59.8mm and 48mm and an inlet diameter of 36mm. I think the smaller A/R of the J spec is partially due to the bigger radius, but not sure how much. Anyone know the figures? So the UK A/R is bigger than the J spec, but the turbine is smaller! This is a bit confusing, but what I think the purpose of this is so UK spec can make more power and J spec can spool up fast. The small A/R on the J spec will spool up ultra quick and also the light weight ceramic turbine (even though its bigger than UK spec) will accelerate faster (i.e. spool up) for a given air flow. At steady state conditions a ceramic turbine would have no advantage over a steel turbine. If the J spec turbine is replaced with a steel one the turbo will take slightly longer to come onto boost during acceleration, but will be able to produce more boost due to the greater reliability of the steel turbine at high rpm's (needed for boost above stock levels). Its overspeed problem will be only very slightly different as inertia does not have much affect at all on turbine speed at steady state conditions. Anyone got the figures to explain the A/R of the UK turbine? I know Tricky Ricky recently fitted some. So as the overspeeding is pretty much down to the A/R ratio rather than lightness of ceramic turbine (which makes complete sense i suppose, as this, i would expect as you say, just aid spool-up with lower inertia and not affect steady state condition) in theory if it were possible to enlarge the exh inlet port area of the turbine housing and match this to an enlarged manifold port area, the A/R ratio would be greater? I haven't really looked at the innards of to see if there's enough available casting for this to be possible, but I assume it's not otherwise it would have probably been done a fewtimes before by now. Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 18, 2007 Share Posted May 18, 2007 The A/R ratio is the shape of the 'snail' if you were to unfold it onto a flat surface. So you can't really machine it retrospectively, you need another part that has been made from a different cast. Even if you were to swap that, the next hurdle would be the log-style exh manifold, it doesn't look like it would flow a lot more. Then of course the ceramic valve would be under more stress, so it would need to be re-engineered. Not easy. The exh bypass pipe would have to be made a bit bigger too. The list won't end, will it? Quote Link to comment Share on other sites More sharing options...
Kranz Posted May 18, 2007 Author Share Posted May 18, 2007 in theory if it were possible to enlarge the exh inlet port area of the turbine housing and match this to an enlarged manifold port area, the A/R ratio would be greater? I haven't really looked at the innards of to see if there's enough available casting for this to be possible, but I assume it's not otherwise it would have probably been done a few times before by now. In theory, yes. But it would have to be blended all the way back to the narrowest part of the scroll (well inside the turbine housing), which is impossible to reach. The only way to achieve this is to open the port out by hand as far as possible, then extrude hone the turbine housing to remove any step and increase the diamater further down the scroll. This would increase the A/R a little (from my measurements the A/R would go up to about 0.40) for a 2mm increase in the diameter at the area of the scroll that is in line with the radius measurement. Quote Link to comment Share on other sites More sharing options...
Stevie Boy Posted May 19, 2007 Share Posted May 19, 2007 Are all the stock J-Spec ceramic twins CT20's and the CT12's were fitted to UK's or otherway round? Did they change model turbo to summink else on VVTI's. Tried searching till the cows came home but all i've found is stuff to confuse further. I've had a nose round cold sides visable on my the and all i can make out is cast TOYOTA text and nothing else to be seen. Is there a model year/chassis number/turbo spec link anywhere i'm missing? Quote Link to comment Share on other sites More sharing options...
Kranz Posted May 19, 2007 Author Share Posted May 19, 2007 Are all the stock J-Spec ceramic twins CT20's and the CT12's were fitted to UK's Yep, that's right Did they change model turbo to summink else on VVTI's. CT20's I think. . Is there a model year/chassis number/turbo spec link anywhere i'm missing? http://www.turbosupras.com/pages/en/pages/technical/CT20%20turbochargers.htm http://www.geocities.com/MotorCity/Pit/9975/dataBySubject/Turbochargers.html http://www.turbosupras.com/pages/en/pages/specifications/JZA80/jza80.htm There is a webpage with the difference between J spec & UK spec turbos but I can't seem to find it. i have it in a Word doc though:J Spec Vs UK Spec Turbos.doc Quote Link to comment Share on other sites More sharing options...
dandan Posted May 22, 2007 Share Posted May 22, 2007 Just to go back to the earlier question from John about my turbos... I believe the A/R is stock JDM. If anyne asks about my turbos I just say they are JDM with steel turbines and a larger thrust bearing - it saves on aggro/hassle. In theory, seen as they have a steel turbine wheel and a different bearing they are hybrids but I'm 99% sure there no funny business like a clipped turbine wheel or anything. Quote Link to comment Share on other sites More sharing options...
Kranz Posted May 22, 2007 Author Share Posted May 22, 2007 Do they have stock compressor wheels though? Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 23, 2007 Share Posted May 23, 2007 ...I'm 99% sure there no funny business like a clipped turbine wheel or anything. The clipped wheels are not exactly funny business, but they are not totally botch-free either. It is a trade-off where you lose some exh backpressure at full boost but you also raise the boost threshold quite a bit (lower aerodynamic efficiency of the exh wheels) If it is impossible to change the exh A/R it might be an acceptable compromise perhaps, as long as an informed decision has been made. The dodginess stems from some traders keeping the downsides to themselves, only mentioning the 'upside' Quote Link to comment Share on other sites More sharing options...
dandan Posted June 8, 2007 Share Posted June 8, 2007 Do they have stock compressor wheels though? I reckon they probably do. I think the turbos I'm running are effectively no different to stockers but just with the steel turbine. Maybe I'm just lucky with the tuning/condition of the motor as it's definitely the quickest BPU I've driven - and on the dyno at 1.3bar the EGT's didn't pass 840degrees C. Quote Link to comment Share on other sites More sharing options...
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