paulrenn Posted October 23, 2002 Share Posted October 23, 2002 Hi all I was just idly wondering to myself about what, if any, benefits we could get by using differently sized turbos in the sequential system. For example, the first turbo could even be made smaller, so that boost builder earlier (spins up faster), while the second turbo could be made larger to give an even bigger slug of power when it comes online. I'm not sure how the stock Supra turbos match up in the Toyota turbo family lineup. I'm wondering whether turbos from other models (eg Celica turbo) could be fitted without having to change the manifolds etc (i.e. same housing sizes, same bolt pattern, etc). Anyone have a diagram of the Toyota turbo family sizing? Any thoughts? Quote Link to comment Share on other sites More sharing options...
Branners Posted October 23, 2002 Share Posted October 23, 2002 The only problem would be the transition, when the second turbo comes on line the drop in power as it tries to spool up would be more than just noticeable. I dont think theres any other reason why it cant be done and it would be good to see somebody try, but you still have the limitation of the exhaust manifold which is very restrictive on the sequential system. JB Quote Link to comment Share on other sites More sharing options...
paulrenn Posted October 23, 2002 Author Share Posted October 23, 2002 Why would there be a drop in power? My understanding of the sequential system is that both turbos operate together once the first turbo has prespooled the second. You obviously need to get the sizing right so that the total flow is still the same or more than the stock turbo setup, but I thought this could be a way to get less lag. Isn't it the case that the stock turbos are both identical sizes? Quote Link to comment Share on other sites More sharing options...
Branners Posted October 23, 2002 Share Posted October 23, 2002 The small turbo is pushing a certain amount of air, you are then trying to make a second much bigger turbo spool up so the drop in power is from the second turbo taking longer to spool up (big turbo, big spool time) and while it is spooling it takes airflow from the 1st turbo. The prespool would not be sufficient to spool up a larger turbo as it was designed for a specific size of turbo. As I say, if you can accept a drop in power at transition and then a big kick from the second turbo it might work. Im not sure what the first turbo would do when both teh first and second turbos are on line as the airflow characteristics might be a little strange. JB Quote Link to comment Share on other sites More sharing options...
Ian C Posted October 23, 2002 Share Posted October 23, 2002 The airflow would be quite strange indeed. The outputs of both turbos simply 'meet in the middle' so the airflow from each turbo has a choice of three directions - towards the intercooler, towards the other turbo, or back the way it came. Obviously, it's never going to go back the way it came, and if both streams are of the same speed and pressure, it's not going to go into the other turbo either. But consider what may happen if one stream meets with a weaker stream. Some of the air will try and go towards the 'weaker' turbo as the flow of air from it is not as strong. this will cause turbulence and probably a loss of airflow. Some of the airflow from the strong turbo will therefore go the wrong way, and the airflow from the weaker turbo will stall. Overall, you'll end up with less air going towards the intercooler and some pretty rough turbulence effects. That's my theory, anyway. Fire away -Ian Quote Link to comment Share on other sites More sharing options...
Syed Shah Posted October 23, 2002 Share Posted October 23, 2002 But wouldn't they have to be the same size? I thought that was a must for a sequential setup? Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted October 24, 2002 Share Posted October 24, 2002 Originally posted by Ian C The airflow would be quite strange indeed. The outputs of both turbos simply 'meet in the middle' so the airflow from each turbo has a choice of three directions - towards the intercooler, towards the other turbo, or back the way it came. Obviously, it's never going to go back the way it came, and if both streams are of the same speed and pressure, it's not going to go into the other turbo either. But consider what may happen if one stream meets with a weaker stream. Some of the air will try and go towards the 'weaker' turbo as the flow of air from it is not as strong. this will cause turbulence and probably a loss of airflow. Some of the airflow from the strong turbo will therefore go the wrong way, and the airflow from the weaker turbo will stall. Overall, you'll end up with less air going towards the intercooler and some pretty rough turbulence effects. That's my theory, anyway. Fire away -Ian Do you not think they would take the path of least resistance i.e. towards the intercooler ? Quote Link to comment Share on other sites More sharing options...
Ian C Posted October 24, 2002 Share Posted October 24, 2002 I don't think it would. I'm trying to think of good analogies or explanations that work in text form and failing dismally at the moment. I've never re-written a post as much and then just copped out. -Ian Quote Link to comment Share on other sites More sharing options...
Adam W Posted October 24, 2002 Share Posted October 24, 2002 I'm 99% sure you're right Ian but I can't remember enough fluid dynamics to fiure out why I think what would happen is, turbo number one would produce 50 units of air, turbo 2 would then come online and produce 80 units of air. You'd get about 110 units of air heading towards the intercooler, but 20 units of air blustering around getting confused because of the pressure difference between #1 and #2 turbo exits. Not sure if thats an accurate explanation, but I'm positive you'd get lots of inefficiency, heat build up, etc. Quote Link to comment Share on other sites More sharing options...
Supra Pilot Posted October 24, 2002 Share Posted October 24, 2002 Ian, well put together m8:thumbs: Quote Link to comment Share on other sites More sharing options...
Ian C Posted October 24, 2002 Share Posted October 24, 2002 Lol I thought of lots of analogies, such as the flow of water through a hose that is teed off to the bottom of a bucket that also has water in it, or a parallel resistance circuit in electronics, but they are impossible to get over in text form. you'll just have to trust me Or try it out and wonder why the little turbo gets it's vanes sheared off when #2 comes online -Ian Quote Link to comment Share on other sites More sharing options...
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