So, I've been contemplating doing a low cost twin turbo build using refurbished OEM turbos. Question: Say you have a 6 liter v8 engine, would each bank of this engine have basically the same requirements as a 3 liter 4 cylinder and benefit from that 4 cylinder's turbo? From what I can tell, the only difference in the basic turbo requirements would be the volumetric efficiencies between the two engines but I'm far from being well versed in this stuff.

 

In a very general way, probably yes.

 

If the RPM range is similar between the two, and the 4 cylinder has a similar powerband, and makes half as much power as you want the V8 then maybe. A turbo is going to have a given volume output where its efficient, most likely if you post what your building there are people on this forum who can suggest turbos in a given budget.

 

As others have said, if ve, and rpm are similar it may not be a bad starting point, but keep in mind that most oem turbo setups are typically somewhat turbo limited (small).

 

That is what i was thinking, I would make my target hp output double that of the 4 cylinder turbo engine and build my engine around that to hopefully stay within the turbo's efficiency range. I'm looking at a couple of 2008 subaru wrx or legacy gt 2.5 liter turbos to put on a 1983 fox body 5.0. My goal is 450 to 500 hp. Those cars get 225 hp on 8 psi and the turbos are good for 20psi+ on that engine. I'm trying to go the cheap route on the the turbos because I'm gonna be putting a lot of money towards making the car handle that kind of power. I have to switch to a maf ecu and port injection, Piggyback, rebuild with forged internals, different trans.. The list just gets bigger every time I think about it.

 

Good luck on your build man.. I would search the forum. Many successful turbo 5.0 combos you can model yours after. The trail has been cut many times before. 500hp is about the limit on a stock block. I don't think I'd spend a ton on good internals without an upgrade to the block. Can't build a mansion on a crap foundation.

 

Find a couple svo or turbo coupe turbos. I had a similar setup and it was fun.

 

What you should be comparing is HP, not CID. HP is a factoring of CID and VE at that CID (and other things but this is the short version.)

As an example, smogger 454 making 235hp would be okay with a similar turbo as a warm 305. Where things change is 1)detonation tolerance and 2)where the power is made and 3)What the detonation threshold is for a set octane.

If the turbos you are looking at are capable of making the HP that you are looking for you're probably at a good starting point. I will say with the China turbos around these days be careful of the value proposition of used turbos. If you're talking about say an LQ4 with any sort of real mods besides valve springs (cam) I would be looking at a a pair of HX35s or HY35s probably. Maybe a pair of PSD turbos if you can get the late model ones with smaller turbines.

 

I've had similar thoughts re: my Taco (4.0 V-6) with a WRX (2.0L) TD-04 hung off each bank..
IIRC my Saabaru (WRX in a dinner jacket) was ~12-14psi stock rated ~225hp (@ crank), now have that TD-04 maxed @ ~18-20psi, would guess (hope) 225+ @ wheels but hasn't seen a dyno, yet..
I have the motor out of the Taco to rebuild (was well acquainted with the rev limiter for ~150k, finally got tired of my antics) and a few tired TD-04's around that could be freshened up and put to use, along with a collection and familiarity with the associated bits, flanges, etc..
Would this be a decent trail to pursue..?
Obviously haven't even gotten to the tuning side of things yet.. Though the truck does already have a Walbro 225? pump I upgraded a few years ago with an eye towards future boost (liked the TRD S/C's for it, but always have been more partial to turbo things anyway)..
I should add it will be a dune/play Toy when put back together, more interested in quick response than huge #'s..

 

What I'm asking is if your stuck using oem injectors from your supplier? If so your best bet is mopar 04852747AA which are something like 39 lb at 41 psi, these were stock srt4 injectors and would be good for modest power goals. If you want more power you could step up to mopar 68170238AB which are 57lb.

Aftermarket injectors go strait to seimens deka 60lb, very good bang for the buck, easy to tune, good consistency.

 

A TRD blower is going to do that better than turbos.

Duning is going to put the engine under a lot of load a lot of the time. Your turbo hot side plumbing would have to be robust and/or supported to keep weight off of it, yet not constraining to thermal expansion. The tune needs to be done with attention to keeping EGT in check. Inconel exhaust valves would also worth considering IMO.

 

Fully agree, but; I have the turbos, TRD S/C's are not common/cheap.. Trans is already built with a decent stall (don't recall exactly what offhand), should help spool small twins and besides getting moving most of my Duning is spent in the upper rev range..

These are very good points, thank you..!
I never thought of the valves and have no real idea where to start on tuning yet for this platform ('06 Taco 1GR)..
The hot side plumbing I think I can handle, but expansion vs support will def be a real issue..