Watch out on all the apples to oranges comparisons.

From what I understand, the RX-7 and Supra TT use pseudo sequential style turbo setups. At low speed a valve closes off the exhaust tract to the big turbo, allowing a small turbo to spool up quickly and providing good low-end response. As load, RPM, etc. increase, the valve opens up allowing the second, larger turbo to spool up, giving even more air. That is what I could find about the Supra TT at least, and I'm pretty sure the RX7's was similar from what I've heard.

Now all this leads to a lot of complexity. You have the valve and its control, half the exhaust being cut off some of the time, etc. This can be a big pain when you start upgrading and want to go for big power, possibly upgrading the turbos. That's why I'm guessing a lot of guys rip the TT system out and go to 1 big turbo. Others (like bricke said above) have set it up to a full-time parallel system where the valve to the second turbo is always open.

The TT system in cars like the Legacy or Skyline should be a true parallel system, with half the cylinders spooling one turbo, the other half spooling the other turbo. In something like a V or H engine, this makes packaging/exhaust plumbing much easier. Just hang the turbo right off its bank of cylinders. And these turbo systems can be just as "simple" as a single turbo setup.

 

True but you could not get an evo to work with a sequential setup. it wouldnt be worth it. you have 4wd you dont need to worry about spool just launch at a higher rpm and dont worry about it.

 

Why can't we all just agree that it would be an idiotic waste of time and money to attempt a fabrication of a twin turbo setup on an evo?

 

Uh....I remember a triple turbo supra being completed quite a while back. I will have to dig through my stack of magazines to find it, but it was a guy in Phoenix and I think he used it mainly as a show car. It had 3 15" JL speakers and it only made about 600hp.

 

The Skyline has a straight six in it. In my opinion, twin turbos are only worthwhile on either V/H style engines, or straight engines that are large enough. The Supra engine at only 3 liters is not large enough to take real advantage of a large, parallel twin setup. Now, if it were 5 liters or so, twin would be the way to go.

And I agree, it's ridiculous to expend mental energy contemplating a twin setup on an engine as small as the EVO's.

 

the reason Subaru has done some twin turbo setups (sequential) on their flat 4 is strictly because of the layout of the engine, it's a twin bank.

Two banks of two cylinders allow you to do a twin turbo setup fairly easily, in fact the piping works pretty well. Matrix engineering in portland did a twin turbo 2.5RS as well, I don't know the power output but they seem to think it works pretty well. Still though, no one has done a really high power output twin turbo subaru engine to my knowledge, 2.5L or else.

But, on the evo it's an inline 4...the piping and exhaust manifold setup would probably be a nightmare to do a twin turbo setup, and definitely not worth the time invested, especially for 2.0L of displacement.

 

rarson: I know the Skyline is an I6. I guess my paragraph wasn't worded very clearly since I switched thoughts mid-stream to talk about banking and such. Funny you should mention the Supra being 3L, cuz the Skyline engine a 2.6L. And it's running a true parallel twin turbo setup.

Ben: I think that a company in AZ tried to make a twin turbo 2.5RS, Forced Air Technologies maybe? I don't think they ever took it to market though. Last I heard (a few years back) they were having problems with the prototype.

 

Yeah, but all the big horsepower turbo upgrades switch it to one, as it should be.

And the GTR ('Spec's aside) is the only Skyline with the 2.6 in it. R33 and R34 GTS-T's have the 2.5 and R32 GTS-T's have the 2.0 in them.

 

Damn wireless ethernet flaking out on me again.

 

Better yet - Look into a twin charged setup - both supercharger for low end grunt and turbocharged for maximum high rpm flow. you'd never know you had only a 2.0L motor.

old mid 80s MR2s had a few of these setups making just under 600hp that felt like a V8 from idle.

 

MechTech made a twin turbo kit for the MR2 using Aerodyne turbos. One of the few cars that are known to have the kit is owned by a guy on the MR2 boards who goes by Pouya. His car makes 370ish whp and hits full boost in the high 2000rpms IIRC.

His website has a lot of info, but no performance figures. http://www.madpsi.net/PMR2.htm

I would prefer a single turbo, if it could do the same.

D