Heres how i see it.....
If your friend wants to put a 2JZ-GTE into a MA70 why not take the money you would spend on the 2JZ and the money on the old supra and buy something better...... Old supras still do have potential but they are basicly heavy, ugly, box....
Why not get a Supercharged AW11..... First gen MR2....
RWD 1.6L 4AGZE
get someone to make you a turbo setup for it and run it twincharged.. you could get huge power and better times from a AW11 and you would be happier with it because IMO the 4AGZE is WAY more reliable than the 7M-GTE from the Mk.3 supra....
First off, why would anyone twincharge, and what is twincharging. Twincharging is using a turbo charger and a super charger on the same engine. The supercharger
is a roots type positive displacement unit that boost the same at all engine RPM, with minor differences due to the engine's VE as RPM changes. So why have 2 pumps?
Why make something complicated much more complicated? well, the SC will be feeding the engine air at low RPM's. this means that the SC boosted motor is pushing out more
exhaust gas than a similar sized NA motor. for example our beloved 4agze at 8 psi is putting out the same amount of exhaust as a 2.5l NA motor. So lets look at the DSM guys. they have some big turbo's that spool up in the 4-5k range for unstreetable BIG power levels. On the twincharge car, these turbo's should spool up nicely at a usable RPM.
There are a few different plumbing possibilities with both blowers. There are even more so when you add a bypass valve into the mix. Some arrangements dont make any sense.
for example, if you have the SC blow into the TC then into the motor, when the TC spool sup, it creates a vacuum on the inlet side. this means the SC is feeding air to a vacuum.
The SC only lets a set amount of air past it, so the turbo is basically worthless in this setup. Another arrangement is the two blowers side by side. this arrangement is crap too
because the SC will be boosting and pushing air backwards thru the turbo. The motor may never see boost. A very interesting arrangement is the turbo first, then the SC,
then the motor. This is diagram 1. I call this arrangement very interesting because as far as I have been able to tell, the HKS kit worked this way. So you have a SC that takes 1.2 L of air every time it spins. If you feed it boosted air at say 8 psi, it take 1.2 liter of 22.7 absolute psi air and places it in the space of .8 liters, making for 34 psi absolute aitr on the other side of the SC. this is 19.35 psi boost. The problem with this setup is that you cannot disengage the SC at high rpm and avoid pumping power into it to compress air. Another problem is you still compress air with the 55% efficient SC making more heat than just a turbo alone. I have also heard that the SC lobes have a teflon coating that can be destroyed by too much turbo heat. so why did HKS do the kit this way? Because it was very easy to do would be my guess. The arrangement I lik ebest is the SC pumping into the Turbo, then into the engine, but with the addition of a bypass valve around the SC. At low RPM when the SC is pumping air into the motor, the boost pressure keeps the bypass closed. teh motor works like a regular SC motor. During this time the boosted motor is working on spooling up the turbo. Once the turbo begins spooling it creates a strong vacuum on its inlet. this vacuum sucks all the available air the SC can deliver. Since the SC does not compress air internally, the air is not heated, and the crank is not providing the power to compress the air anymore. the vacuum also serves to pull the bypass valve open allowing the turbo to suck in as much air as it wants. In this case you set the turbo wastegate to the high boost level you want, say 20 psi. There is no real need to disengage the SC since it is basically just free spinning. All the compression is done by the 70% efficient turbo. There is no transition to worry about from SC to turbo becasue the bypass valve will end up taking care of it. Say the driver is driving with low throttle input. The SC never engages an the bypass valve will be held open by engine vacuum. Then the driver gives it a bit of gas, and the SC engages. The SC produces boost that closes off the bypass valve and feeds the motor excess air. If the gas is held down the turbo spools up and the bypass valve opens up again to supply the extra air.
See its pretty simple ive considered it..... BUT the lack of seats and storage in the MR2 is what eventually kicked my dreams in the sack..... ah well..... i still love toyotas.... <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt='
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