possible to swap between AFM's on the run?

[myne]

http://www.users.on.net/~jvizard/myne/4agztedesprot.GIF
http://www.users.on.net/~jvizard/myn...desprotvac.GIF
http://www.users.on.net/~jvizard/myn...edesprotsc.GIF
http://www.users.on.net/~jvizard/myn...desprottur.GIF

That's the setup I thought of for twin charging.
Reason it's vacuum actuated is because engines are VERY analogue.

Wtf do I mean? Well, it all relies on your foot.
Neither of the boost setups provide exact boost all the time at all throttle positions.
Assuming at WOT the SC provides 15psi till 4000 rpm and the turbo then spools and takes it up to 25psi, you'd think it's easy. Just turn off the sc at 4100rpm.
But that's ONLY WOT.
The SC might only provide 5psi at 3/4 throttle, and the turbo might not spool till 5500rpm, so turning it off at 4100 will make a big hole in the power. The only answer is to make it analogue, or use a computer.

[mic*]

Brett,
just a thought but have you considered doing exactly what you proposed - except - switch the bypass to open instantly in response to the SC OFF conditions mentioned. Then put your 1-2 second delay on the SC clutch.

Would help turbo transition a bit i think. Would also help to stop the SC contributing to the pressure waves that'll be bouncing up and down your intake on gear shifts, but still keeping it on. Maybe add a BOV plumbed back into the bypass...

[Lambolica]

Stu and I condured up a way around that by closing the throttle to the S/C as it starts to reach maximum boost and allowing a alternate path.
ie limiting the Air available to the S/C to reduce the "double boost" issue, the flaw I think was being able to tune the ideal time for the throttle to start closing.

Bretts way is way cool as far as tuning these things out. I should try to pull up the sketches that I have for several different variations of twin charging, including twin AFM and vane flap.

[mic*]

Why does nobody else seem interested in these chargers working together? Why twin charge if they are providing boost independantly?

My plan will not happen for at least 10 months but the discission is still beaut. I hope to use a minimum size bypass around the S/C so it could be clutched for idle and cruise ONLY.

Aside from that, when your under boost team them up and strap in...

Have not looked into turbo size, but plan to but a slightly LARGER pulley on the S/C to reduce boost so that the "team up" does not get out of control by 5500rpm...

My biggest problem is going from the standard SC14 outlet on a 1G-GZE to some form of intercooling. Looking at glycol and fancy shit coz Air to Air isnt gonna require really inefficient plumbing...

[oldcorollas]

Mic,
you are overlooking something painfully obvious.

the SC DOES NOT BOOST.
the SC is a fixed displacement pump.

what goes in, comes out the other side, AT THE SAME PRESSURE.

if the turbo provides 1psi, the SC also provides 1psi.

the SC can only flow what either leaks past the turbo when it is not boosting, or what it flows when it is boosting (since turbo DOES boost, whereas SC does not)

so say the turbo is making 5psi, and the SC moves that air, but the motor can't swallow it, and there is 10psi in the manifold... thats fine.

when the turbo is also making 10psi, and the manifold is at 10psi, then it DOESN'T MATTER if the SC is there or not.. it is no longer having an effect... in practice, since the SC is overspun to provide boost from atmospheric air, there will be higher pressure in manifold than before SC... (but ONLY because the SC moves more than the engines displacement of air)

BUT, that is what the pressure controlled SC bypass is there for.... when you open that initially, you are allowing air to leak back past the SC (reducing manifold pressure), when the turbo can provide the level of boost required (and hence, it has enough airflow), then the bypass wil be fully open, and the SC can be turned off.... it is simply a working pump in a bug river of air, with inlet and outlet going to same place, so it hs no effect.

if you don't do it this way, when the SC turns off, you lose a lot of air.
remember that turbo can have pressure with almost no air flow, and SC can have no pressure with full air flow. have you read the old threads on twincharging? i think i moved them to new forum..

mic, so you are panning to NOT turn of the SC? how do you plan to get around it's rpm limits? if you underdrive it, what is the point of having it there? will turbo spool up any quicker for an engine runnign 3 or 6psi of boost (a little.. but nothing a proper turbo cannot do anyway)

Myne, looks good


parallel twincharging can work.... but the whole point of twincharging (i think) is to have SC overspun to provide high boost down low, then turn it off and use large turbo for even higher boost up high.

the easy way to do this is to have a MAP sensored engine.

the hard thing is to provide a smooth transition between SC suddenly turning off and turbo havign enough flow.

if you have them both workign all the time.. the need for SC reduces, and you also need to work out how to get turbo to spool up without compressor suge (since when it is producing lower pressure tan SC, the turbo outlet MUST be blocked (to increase pressure), or vented (to allow flow, but no pressure)...
how do you plan to get around that?

remember.
turbo = pressure but not necessarily flow.
SC = flow but not necessarily pressure.

[mic*]

Thanx stu.

S/C would act remarkably like an engine would when thinkin bout it...Ironic considering early ones were exactly like a IC engine chamber without a plug. Turbo would generate boost against it eventually...

[oldcorollas]

Thanx stu.

S/C would act remarkably like an engine would when thinkin bout it...Ironic considering early ones were exactly like a IC engine chamber without a plug. Turbo would generate boost against it eventually...

SC IS an engine POSITIVE DISPLACEMENT.. thats kinda the whole point

[mic*]

Cmon serve it up

[myne]

Think of a super charger like this :

Grab a 3a engine.
Bolt it infront of a 4a engine.
Spin the 3a at 1:1 to the 4a.
Unplug the spark plugs of the 3a
Mod the cam so that there is no compression or power stroke (only induction and exhaust)
hook the "exhaust" of the 3a up to the inlet of the 4a

What do you end up with?

For each rotation of the 4a the 3a pumps out 1.5L.
Each rotation of a 4a consumes 800cc
That means you're trying to cram 1.5L into 800cc
Boost!

Voila! you have the worlds least efficient supercharger!

[brett_celicacoupe]

Brett,
just a thought but have you considered doing exactly what you proposed - except - switch the bypass to open instantly in response to the SC OFF conditions mentioned. Then put your 1-2 second delay on the SC clutch.

Would help turbo transition a bit i think. Would also help to stop the SC contributing to the pressure waves that'll be bouncing up and down your intake on gear shifts, but still keeping it on. Maybe add a BOV plumbed back into the bypass...

yeh - definately something to think about