twincharging prototypes needing constructive critisism (SC14 + turbo)

[TA-022]

might help.



stolen from this thread >>>CLICK<<<

[IN 05 NT]

how about an a/c electric clutch on the SC so boost till 4g, then clutch lets go...supercharger out of the picture.....

am likeing this thread...

[myne]

I came up with that a while back.

I strongly suggest against a front mount intercooler between the SC and the inlet.

Simple reason, I had one. It sucked.
Why?
Since the throttle is BEFORE the SC, the intercooler is effectively just part of the plenum.
For the engine to see boost, the SC has to first fill the plenum's vacuum, and THEN add pressure. It's a huge volume to fill. The throttle response is appaling, the low end torque is lacking, it revs UP between gearchanges which makes you sound like a douche, and it's just generally a pain in the ass.

Personally, I've gone against my own idea pictured above.

I like the simplicity of running the engine exactly as the factory intended, but with the inlet (before the throttle) seeing boost from a turbo.
Sure, it's a bit inefficient to compress the air twice, but it is totally smooth, totally predictable, and really easy.

[nick.parker]

Myne,
In your diagram above, it seems to me that the manifold pressure would ALWAYs be higher than the turbo outlet pressure, since its the turbo is stuffing the SC with compressed air which is then being further 'packed' into the inlet manifold at higher pressure still? (So the SC bypass wouldn't get a chance to work).

Edit: Ok I see, you only use boost on the turbo side to actuate the bypass, I think it would have the potential to open the bypass too early, maybe giving a dip in boost at the transition.

Cheers, Nick

[myne]

nup





But what you describe is exactly what Cameron Datto runs, and I think it's the simplest way.

[nick.parker]

I'm confused is vacuum opening or closing the bypass? Please specify!

[myne]

vac between the SC and ports opens it, boost before the SC opens it.

Basically it closes when the SC creates boost and never otherwise. Perhaps it'd be simpler to rig it so that it closes when the SC engages.

[nick.parker]

Ok thanks.
I would be interested to know what the torque curve of the engine does at the point that turbo boost begins to actuate the bypass valve, because at that point the manifold pressure would surely be higher than the turbo boost pressure.

Surely this must cause something strange (even if short lived) to happen, as the turbo suddenly needs to increase its pressure ratio to maintain the engine torque? (i.e. to keep pumping the same amount of air).

Cheers, Nick.

[brett_celicacoupe]

I strongly suggest against a front mount intercooler between the SC and the inlet.

Simple reason, I had one. It sucked.
Why?
Since the throttle is BEFORE the SC, the intercooler is effectively just part of the plenum.
For the engine to see boost, the SC has to first fill the plenum's vacuum, and THEN add pressure. It's a huge volume to fill. The throttle response is appaling, the low end torque is lacking, it revs UP between gearchanges which makes you sound like a douche, and it's just generally a pain in the ass.

yah but did your setup ALSO have a TB on the plenum that ran parallel to the one before hte SC?



more detailed replys will be coming when i get some sleep!

[brett_celicacoupe]

might help.

stolen from this thread >>>CLICK<<<

i reckon that one way valve would be VERY restrictive to air flow!

[TA-022]

it was there i thought it might be of use...this is all interesting but way over my head..lol

[DeftAnesthetik]

not sure if you seen this or not but here is a site that may interest you in your quest.

http://come.to/twincharger

[thechuckster]

very timely that you your link Deftanesthetik, Brett & I were just talking last night about how one might use megasquirt to drive his twin-charge engine.

Am curious about what kind of control is there on the 1-way valve? can you provide some more detail on it?

(btw: we seems to have used too much bandwidth from you geocities site).

cheers and well done!
Charles

[brett_celicacoupe]

not sure if you seen this or not but here is a site that may interest you in your quest.

http://come.to/twincharger

interesting. except i dont like the idea of having a one way valve. in all forms they restrict the airflow in some way.

i guess this also emphasises that megasquirt is up to such a task

[mic*]

This is a topic ive put a bit of thought into owning a 1G-GZE. Only thought tho at this point.

I think the best way based on simplicity & smoothness (as a street car) has been mentioned. Turbo - Throttle - SC - Manifold.

One point iv thought is that the SC must have a bypass (from its own outlet to inlet) for vacuum operation no matter how you run it;
If it is clutched - because its too inefficient to suck through the lobes, and yes the engine will turn the lobes to breathe.
If its not clutched - because its too inefficient for the SC to try to create a massive presure ratio as it literally tries to push every air molecule available to the manifold side. Causes ridiculous heatsoak.
I have thought that the standard 1GGZE ABV would bypass enough air to keep the SC from warming up under vacuum... as i see the SC as being permanently driven in my vision.

My pulley setup is overdriving the charger at 1.7:1 which yeilds approx 1.1 bar (16psi) WOT, slightly less at lower revs WOT. This suggests that the VE of the SC is worse than the motor, but it improves relatively with revs.

However this ratio is really a bit too high as it as the SC14 doing 11,000+ rpm if i rev the 1G right out. On good advice from Nick, 10,000 rpm's is the most you wana think about or the SC will begin to overheat.

Anyway this to me is disappointing from the twincharging perspective. I would like to have thought you could get even more boost (ie bigger ratio) out of the SC14 and still be able to redline the motor (because the pulley is permanetly driven). Which brings up my biggest point of curiousity;

In a twincharge setup as above TURBO->TB->SC (ignoring intercooling for one second), how will the SC respond in to a decreasing pressure ratio across it as the turbo starts to push harder with more revs???

Will the turbo ever get close to an equal ratio before and after SC within redline? - i doubt it because fundamentally the motor is the biggest restriction in the flow path...

And it also makes me think that the load on the SC would drop as revs go up (relatively speaking), even tho the flow is considerably greater. So would the 10,000rpm limit be able to be pushed?

Biggest problem i see to above setup is intercooling with pipework that is bareably inefficient... The SC wont like getting hot turbo air, but has it own heat too to worry about.

The aforementioned twin IC idea is interesting but would involve valves etc too.