Homemade st
- Thread starter pork
- Start date
solarice
Ex. Club Member
I assume you'd just bypass the sc once the turbos up to speed. Something that monitors manifold pressure would probably do. Below a set level sc on / bypass shut, above the set level sc off / bypass open.
I dont see mapping being any different as you're mapping the sc and turbo in different ranges.
Tbh pretty much how the diagram says
I dont see mapping being any different as you're mapping the sc and turbo in different ranges.
Tbh pretty much how the diagram says
Its really simple.
Say you want to achieve X amount of boost. Turbo doesn't make X amount until Y rpm. So you use a supercharger to reach X boost beneath Y rpm, at which point the supercharger is no longer needed.
Turbo's work on exhaust gas & due to the supercharger, the turbos normal boost threshold of Y rpm drops because of the extra exhaust gas and power created by the supercharger.
Superchargers are inefficient generally compared to turbo's so it makes sense to feed this unanticipated boost the turbo now makes into the supercharger. All of a sudden the X bar boost the supercharger has to make is now X minus the additional boost the turbo is making as a consequence of the supercharger being there.
The overall effect of this is the supercharger is under less stress, its lasts longer and runs cooler. i.e. a more efficient system.
The odd way the VW engineers have designed it (why I'd love to know) means that in order to make X boost the supercharger always has to do all the work itself.
Say you want to achieve X amount of boost. Turbo doesn't make X amount until Y rpm. So you use a supercharger to reach X boost beneath Y rpm, at which point the supercharger is no longer needed.
Turbo's work on exhaust gas & due to the supercharger, the turbos normal boost threshold of Y rpm drops because of the extra exhaust gas and power created by the supercharger.
Superchargers are inefficient generally compared to turbo's so it makes sense to feed this unanticipated boost the turbo now makes into the supercharger. All of a sudden the X bar boost the supercharger has to make is now X minus the additional boost the turbo is making as a consequence of the supercharger being there.
The overall effect of this is the supercharger is under less stress, its lasts longer and runs cooler. i.e. a more efficient system.
The odd way the VW engineers have designed it (why I'd love to know) means that in order to make X boost the supercharger always has to do all the work itself.
Sorry to post on such an old thread, but as an answer to the question why VW have put the turbo after the supercharger. I think it is partly because when the heat flow rate of the exhaust is high enough to spool the turbo and create sufficient boost, it then turns the supercharger off with a solenoid clutch thing and just uses turbo, which is more efficient as turbos recycle energy. Having the turbo after creates a more direct air root and less pressure loss at high rpm (motor way).
In the case of the micra st they use both turbo and super at the same time for max boost opposed to just turbo for max boost like the VW. The key thing about a supercharger is it is easier to create "relative" pressure increase with high input pressure. i.e (Pout=Pin+Work done*effective area) so it will always increase the pressure of the substance running through it assuming it is engaged and that work done>Pin, so in the case of the ST putting the sc after the turbo means both are creating positive pressure differential through more of the rev range creating more boost but also using a bit more energy for work done on the sc.
This probs make no sense to anyone just thought i would give my pennies worth.
In the case of the micra st they use both turbo and super at the same time for max boost opposed to just turbo for max boost like the VW. The key thing about a supercharger is it is easier to create "relative" pressure increase with high input pressure. i.e (Pout=Pin+Work done*effective area) so it will always increase the pressure of the substance running through it assuming it is engaged and that work done>Pin, so in the case of the ST putting the sc after the turbo means both are creating positive pressure differential through more of the rev range creating more boost but also using a bit more energy for work done on the sc.
This probs make no sense to anyone just thought i would give my pennies worth.
ow really, i didn't no the super turbo could disengage the s/c. it is a genius little engine there is so few of them about i haven't really had chance to have a proper nosy about one tho. I am looking at similar technologies for big diesel engines at the mo all be it for mainly efficiency rather than performance. The huge bonus of a super charger is you know exactly what boost you will get at what engine speed, allowing you to try and calibrate to achieve near stoichiometric combustion and for this the st is well ahead of it's time.
there is so few of them about i haven't really had chance to have a proper nosy about one tho. I am looking at similar technologies for big diesel engines at the mo all be it for mainly efficiency rather than performance. The huge bonus of a super charger is you know exactly what boost you will get at what engine speed, allowing you to try and calibrate to achieve near stoichiometric combustion and for this the st is well ahead of it's time.
