twin turbo 4 cylindar

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i was thinking of putting a turbo on my 1989 240, but i was wondering if there were any other unorthodox way of turboing a 240 because everyone is now swapping out the ka for the sr20 and i was wondering if there was any way in the world to twin turbo it. i know i would have to work out the intake manifold problem and also have to work out the exhaust because i know that one chambers exhaust helps to pull out another chambers creating a flow, but any advice would be greatly appreciated.

posted by  240SXSR20DET

The only way that wouldnt cause problems would be to split the IM into two seperate IMs, and split the EM, but that would be stupid. Just get a single turbo.

posted by  Oomba

instead of twin turbo'in a sr20 or ka24, you could always go with an rb20/rb25, they can handle the twin turbo option quite easily.

although, quite a few people do prefer just a single turbo cause it's easier to handle and can also sometimes give higher power levels.

take the 2jz-gte for example, one turbo comes in at 3000rpm and the other at 5200rpm, that only leaves another 1800rpm to hold twin boost throughout.

that's why most people just go with a single T-67 or T-88 turbo.

posted by  HyundaGuy

To get a high power output from a single turbo setup you'll need a big turbocharger. And a big turbo takes longer to spool up which gives it more lag. Not what you want.

Twin turbos may not give the numbers a single one has but it doesn't require huge ones to make decent power and also you'll reduce lag with this setup.

As for twin turbo 4 cylinders this is the only 1 I've known to have it done:

Hot Staff twin turbo AE86 (

As you can see it's mainly used for good response.

BTW the RB engines are longer than the SR20s and therefore can make the front end of a 240SX nose heavy. Also the RB20 has less torque than the SR20.

posted by  fudge


ok..... supra thing.... at least get it right while im still alive....

the small turbo works all the way UP to the 3000rpm range. thats when the 2nd one actually kicks in all the way up to wherever the driver shifts.

single turbos will make more power than twins when the single one is big enough to do so. but put 2 big ones together, and u will always have more power. its just more efficient, and less costly, to run single turbo set ups on the inlines.

also, on sequential twin turbo systems, like the one on the supra, only one of the turbos is working at any given time, not both.

u can leave the intake manifold just as it is. oomba, u have never seen a twin turbo car, have u? u have never really seen a twin turbo supra, have u? the intake manifold on those cars actually only have one entry. so how do the 2 turbos feed the intake manifold? the intercooler. wat this guy could do is just get an I/C with twin entries, and only one output, or twin outputs and then just connect them somewhere in front of the IM with a Y tube.

posted by  Inygknok

Um.... no. You don't have to split anything, if you want to run two turbos all you need to do is run the plumbing. It won't work as well as a single turbo (in a 4-cylinder application), but it's not rocket science. It's just a packaging nightmare.

This setup is just absurd, but it's a whack load of turbos nonetheless:

Good luck.

posted by  Bino

I'm suprised it only outputs 720hp with 8 turbos bolted on. I think if he wind up the boost on each turbo to 20psi he'll easily pass 1000hp. Anyway I'm sure that setup can't be good on fuel :drool:

posted by  fudge

20psi on each turbo? i would be impressed if the car was even able to push the turbos to that amount of pressure. would probably get there once it has gone through all the gears.

btw, that pic was posted on another thread a few months ago.

posted by  Inygknok

Well if you had it set up like this

You have yourself two power jets of air pushing against each other, creating pressure against each other. Bad for the turbos, Id say. In a sequential setup it wouldnt be a problem.

posted by  Oomba

twin turbo'in a 4cyl is just stupid in opinion, which is why i suggested he get an RB engine.

posted by  HyundaGuy

I like the drawing of the setup Oomba made but I'm sure twin turbos aren't setup like that. For a start the compresed air goes to an intercooler and that itself can join up the 2 turbos in a way that it doesn't oppose each other so you don't need to have a special inlet manifold.

I don't get why it's considered stupid to twin turbo a 4 cylinder, the smaller turbos would provide greater response. RB engines are heavier and longer so it'll upset the balance in a 240SX.

posted by  fudge

The turbos don't oppose each other. There's nothing wrong with the setup that Oomba drew. If you were running twin turbos and twin intercoolers there's nothing wrong with it being setup like that (except for the need for two throttle bodies, which is why nobody would set it up like that). The two turbos are not "opposing each other". They are providing pressure to a common plenum, same thing as running two turbos into a common intercooler and then a single outlet to the intake manifold.

posted by  Bino

ffs, why hasnt chrisv casted his wisdom upon you ppl?!?!?!?!

i bet hes still pissed off and expecting us to do his dirty work until he calms down (bastard :mrgreen: )

anyhow............................. wtf?!?!?! i ask again, have u seen a damn twin turbo supra?? a damn skyline??? anything?!?!?!

the damn intake manifold has just one entry in the front!! theres only ONE SINGLE entry on inline engines on their intake manifolds. EVEN on twin intercoolers, both of them feed the intake manifold through the same section (this is due to the sensors the IM has on it). it doesnt matter if its through the side, front, or rear, but it will only have one entry due to packaging, efficiency, sensor commodity and usage, etc. like i said, they will most probably be connected with a Y tube in front of the IM. in sequential set ups, both turbos will feed just one intercooler that has 2 entries and one exit.... oh just read my other post for that explanation.

wat oomba drew would mean, that in an inline engine, u would need to somehow invent a way to make one of the pipes leading from one of the turbos all around the engine just to get to the backside of the IM, or vice versa, but either way do a hella of a big invention which would be quite pointless.

in fact, even V engines have IM's that have just one entry and still manage to feed the 2 banks very efficiently. others are created in a way that they have twin entries (each symmetrically apart from each other) but end up in the same chamber, where vacuum power sucks them into the required space (like in the 300zx). and u know wat? the entries are both in the front, even in the TT model.

posted by  Inygknok

Yeah I've seen a TT supra, they actually named it the supra TT from the factory :screwy:

posted by  99integra

There's nothing wrong with the setup that Oomba drew... except the packaging of it. Yes, the Supra has a single inlet intake manifold and a Y-pipe that connects to the front of that. This design is for simplicity as well, technically you could consider the Y-pipe and the intake manifold as a single unit, we'll examine the Skyline for this exercise since the Skyline has 6 individual throttle bodies right at the head (after the "intake manifold"). So, the intake manifold has a single inlet with a Y-pipe connected to the front. For all intents and purposes they're one unit and the intake manifold has two inlets.

posted by  Bino

ehhh, no. the IM on the skyline only has one entry, and its in the front.

yes, the engine has 6 individual TB's, but i dont see wat that has to do with entries to the intake manifold itself.

another problem with oomba's design is also that, its much easier on the IM, due to the force and pressure of the incoming air, that any air entering comes from the same direction, and not from opposing forces. how do u think hurricanes are created? yes, by opposing winds crashing into each other. of course, in hurricanes, both "winds" are at different temperatures (generally, one hot and one cold), but the forces also apply. u could say it would be "chaos" inside the IM when the air enters from both sides before vacuum sucks them into the cylinders. even if its for a split second (or faster or slower), a split second can actually determine the life of an engine (it can actually determine so many things).

IMO, its simple logic, but thats just me.

posted by  Inygknok

You'll notice that I never said it was the most efficient design. I said it would work just fine, which it would. The turbos are not "fighting" each other as was inferred in a previous post. Would anybody actually design an IM like that?... NO. But the car would run just fine if they did. That's all I'm saying.

posted by  Bino

The reason I used the Skyline and the 6-throttle body example, was because most engines have a single throttle body that is mounted at the entrance to the intake manifold rather than at the exit (the 6 throttle bodies on the skyline are at the exit of the intake manifold rather than the entrance). So for all intents and purposes, the intake manifold is just piping, just like the piping going from the intercooler to the throttle bodies. So, this can all be considered a common working volume. So, any Y-pipes in this area could easily be considered as part of the intake manifold. It's all just a working volume.

posted by  Bino

i stick to my opinion that it wouldnt work "just fine" for obvious reasons which i already explained. its not the turbos that are fighting each other, its the incoming air thats coming in with tremendous force INSIDE the plenum.

posted by  Inygknok

It would work just fine, but I respect your right to disagree, so I'll leave it at that.

posted by  Bino

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