Twincharging Discussion

[Vezza]

Hey guys,
been researching twincharged setups (combined supercharger and turbo) for the past year or so. Just wondering if anyone has come across a fully detailed schematic of how the nissan micra superturbo, VW or other twincharged system works. I'm not talking about the general outline of how the chargers function together but specific details on the bypass valve system (when, how does it open) and other intricacies and parameters that makes for a smooth transition from one compressor to the other.

Yes I know the easiest way is to run a compound boost setup with no bypass. However this negates the efficiency benefits of the separate compressors.

The other thing I've noted which does not make sense is the use of a sprung (non controlled) one way valve to bypass the supercharger.

Theoretically this will not work, to my understanding anyways. If the supercharger is producing 5psi and the turbo is producing 6, the valve is meant to open because the turbo pressure has exceeded the supercharger's pressure, but it won't. Because in theory, the supercharger side will have compounded the turbo's 6 psi with its 5psi to get a total of 13.04psi (two pressure ratios multiplied). That means the supercharger side will actually have 13.04psi of boost, when the turbo has 6psi. So if the turbo pressure keeps increasing, the supercharger will do the same and hence the one way valve will never open.

[trueno85]

didnt hks develop a twin charger kit for the 4age back in the 90s?

[ke70dave]

find a way to contact the bloke who makes the razorback ecus. he goes by the name of "foxtail" on rollaclub.

he has an awesome twincharge setup on a 4age (so 4agzte?)

he has some awesome fabrication. i had a good look at it when i picked up an ecu and loom from him. and its very well setup. he has 2 throttle's in the system, one of them controlled by vacume. this combats the crazy random idle you get with complicated intake tracks. i cant stress how much engenuity went into what he has done!

my understanding is that he has the turbo outlet connected to the inlet of the supercharger. no need for any valves then. (twin intercooler too, one before the supercharger and one after it) sure its not ideal. but the numbers he was getting was unreal. something like 7psi of boost at 2000rpm. and then a maximum of 18psi or so at 4000 to redline. the car was forsale sometime ago, im not sure if he ever sold it. was a matt black ke70 with roofracks.

[egg_83]

So your looking for sam. His ke is pretty impressive

[Chairs with flares]

Seems like if the SC drew air from the atmosphere and not the turbo, the valve concept would work quite well since boost wouldn't be compounded. Although you'd have to run some sort of wastegate actuator so the turbo isn't spooling against a 'dead end'...

So kinda like this;



And I'd be inclined to say that the recent systems like the VW would be an ECU controlled clutch on the SC drive, tied into everything else like boost control specific to engine temps etc.

[FAST EDDIE]

just put an sr in it

[Hen may possibly be a nut]

There was a huge thread on Toymods about it a while ago. "parallel twincharging done properly" or similar.

My thought is that unless you do some serious design and control, you may aswell just get a good, new, well sized turbo and be done with it. Doing it properly can give some benefits, but is hard.

Hen

[squish_m8]

i think the price of the custom work in the end probably isn't worth it. and in the end you will have more things that can go wrong.

just go turbo and crank some boost imo

[PRIMRK]

What size turbo should be used here? a lot of people will go t28 in a 4agte conv but with the sc12 taking up low end i can use a larger turbo and not worry about the lag it take to spool.

Have found a few people advising not to go smaller than a t3 as it you would just be selling the charger short.

[Sam-Q]

I think a T3 will selling your charger short. I personally think if you going to go to the trouble of doing twin-charging then you might as well get a huge snail, something along the lines of a turbine that gets full boost by 4500 to 5000. I don't think a little girly T3 will surfice here, hahahaha

For the actual system I like the idea of the blower pushing into the the turbines compressor and then with a one way valve to feed the additional air. I would make my own one way valve to suit probably using motorbike reeds.