Turbo help, like which size and if it'll work

okay this is what I'm planning, I have a 3.1L pushrod... and I want to know a few questions, before I plan on a turbo project. First of all the setup I'm planning will be an intercooled twin turbo, one right at the end of each manifold (header, whatever). I would like to see around 400HP give or take a lil bit. I was thinking around 20 lbs of boost, would be a good target to aim for figuring it won't be a perfect setup so that should get me around where I need to be. First question, I was looking at the GT25, will they be small enough to spool off of 1.55 liters, and what kind of spool up time would I be looking at. I don't have a very broad RPM range to work w/ so I need a rather quick spool. Don't worry about a built up motor handling it unless you really really think it won't handle it, because I'm working on that too, just don't want to get into the details here, I need more turbo help then that.

The GT25 will spool probably just about instantly, because they are so tiny. Unfortunately, your probably looking at about 250 hp tops with those turbos, regardless if you run 20 psi. Btw, twin turbos doesnt mean double the hp either. CFM is CFM regardless of how many turbo's there are. Twin turbos are pretty much a waste of money imho since they make no more hp than a single turbo. Why do you think supra's convert their twin turbo's to single? :naughty: Personally, I would go with a T3/T4 single turbo which is more than enough for your 3.1L. Youll make full boost around 3,500-4,000 rpms and could probably make about 400 crank hp on about 12 psi.

^Word. Or maybe just go straght T04E. Check out the calculator I posted up a bit ago.

20 pounds would be pretty hard on pump gas. you would probably need alcohol or water injection to cool the intake charger enough to run it. if you do this you'll run into tuning problems because you cool the exhaust and make less boost if you run it too early, do a search for alcohol or water injection in this forum and in the engineering/technical forum and you'll find a interesting thread.

thanks alot for the info, after starting some test fits and plumbing planning it going to be a pain in the neck to run twins, I was planning on having a throttle body and intake end on both ends of my upper plenum which I figured would be twice as much air comming from different sides which I know would be a pain to engineer but there would be suffiecent air and would be better then just a twin on one intake... anyways that might not make sense now because I'm really tired and just want to go to bed, but I'll look into the single turbo design and probally save myself alot of headache. The only thing I worry about is the torque, I don't like driving super fast (top speed) and the fact that it's a pushrod engine so it's going to be hard to build up the RPM limit on my engine. I think I red line at like 5500 right now :/ .

oh and I was looking at the water injection earlier as a replacement for intercoolers, but I don't know much about it. I don't have much space to work with so I figured it would save alot of asinine intake piping that I don't have the space for.

lol sorry if this is a bit scatter brained my brain is in bed already

the reasonpeople do twin turbos is simplicity. instead of having to route both exhaust manifolds to one turbo with equal lengths so that you have the same backpressure on both sides (ony in a v engine) you can just have one turbo per manifold. with long inline engines (6 or more) twin turbos are sometimes used because running 6 or 8 tubes into one turbo can be dificult and take up alot of room (if you want the same length tubes from each cylender). the intake setup would be pretty easy, just have a y pipe running into one throttle body (or you can have two throttle bodies that run into a y but then you need two throttle cables and such) and then run it into the intake manifold. also to make around 400hp on 20 psi would take some stronger internals, get some forged pistons, con rods, crankshaft, balance the engine, lower compression, get a camshaft better suited for turbo application.

I would do intercooler+water injection.

Best thing about turbos is you can make power wherever you size the turbo to make power at.

I think you may want to check out the GT28RS.