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oldcorollas
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003

Re: Twincharging, lets make it work

Sun, 21 August 2005 07:00

tricky wrote on Sun, 21 August 2005 16:18

Yeah, the idea of sucking all the inlet air through the turbo seems like an unnecessary restriction. Your idea, oldcorollas, has these in parallel, which seems like a significantly better idea, although a greater amount of pipework will result. Throttling the supercharger seems like it would be a good idea, but maybe unnecessary? perhaps this is something that could be investigated in a modular R & D setup.

As far as the three throttle bodies are concerned, yes, these will be subject to quite a bit of pressure, but the butterflies should handle it, and if not, it probably wouldn't be too much of a challenge to retrofit reinforced butterflies in standard throttles (again saving a bit of money in using pre-existing parts).

In a ideal world, one way valves would be perfect, but existing models don't come close to ideal, especially in extreme circumstances, so I think utilising throttles over one way valves is wise.

It would be interesting to get such a setup running and compare it to a good PD supercharger, 'cos basically they do the same thing. The systemic losses incurred in the form of flow restriction (throttles/valves/bends) and excess piping (loss of charge pressure/boost response) could cause some issues, but I'm sure there is nothing insurmountable.

good points..

more pipework ys, but filling pipework with air will not really be an issue, since the SC can provide nearly full boost from idle in just a few revolutions.

the idea if throttling the SC actually came form some of my SC only ideas Wink

... ie you still have a plenum throttle, but for first maybe 30% of pedal travel, there is no boost, then from 30% to 100% throttle, the pedal just moderates the amount of boost in a linear fashion (maybe a modern EBC will be required here).... this does two things, reduces pumping losses (but may make more heat due to double pumping..), and makes thr throttle much more reliable as a source of control...

i hate the way my stock turbo car will sometimes hit boost halfway thru an intersection in first gear if the pdal is too far down.... i like NA linearity Wink

.. i guess i want a linear boosted car Very Happy

i looked at one way valves very closely, but in the end decided that with fast throttle cahnges, they will end up falling to bits... they will work tho, in fact the turbo putput throttle is effectively just that, since it is both volume and pressure based.. but the SC must be controlled by throttle plates as you are restricting it, not just waiting till it does something..

i totally agree.. there will be losses, but it's hard to compare to a Lysholm SC... the lysholm seems to be good up to around 2:1 pressure ratio, sometimes 2.5, but they get hot (IC will help this), but they certainly cannot do 3:1 ratio.... the twincharge is for the peson that wants a little bit more.. ie 30-40psi range.... we are not talking sensible numbers here...
ie a 4AG with 30psi will have around about 400-450Nm of torque.. maybe from about 5000rpm up.. close to what a 5L motor does, but will have around 250-300Nm below 5000rpm..
the lysholm will give you a good 300Nm from low to high rpm...

so.. basically, it's all about the top end charge... i'm not sure what you would do with a 450Nm 1.6L engine.. maybe put it in a dragster Wink

but yes.. an R&D setup is planned. eventually..
Cya, Stewart

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