OK, I started to buy a few things for the turbo build today. Got the boost gauge, water temp gauge, and the intercooler. Going to go custom and use the F/IC that you guys recommend. Everything else about the kit will be easy to find/buy except the turbo..... here is where I'm having problems picking the right one for my application. I'm looking at UP TO 200HP, but not OVER 200HP. 99% of the time this will be my daily driver. These are a few ratios I'm looking at but can't seem to make a decision....so I list what I'm looking at:

T25 or T3...
.42/.48
.42/.63
.48/.60
.48/.63

I'm open to other ratios.....

 

.48/.63
with that small turbo, you'd need a lot of pressure to get it to 200hp. so forget about fast spooling, concentrate on making top end power. also, you need to vent crankcase blow-by. i assume this is on stock motor, so you will need every technique to eliminate possibilities of denotation.
it's really not that simple.

 

Thanks Spooling. With the 6000ish redline, this car will be a completely different animal then my CRX/GSR turbo with a MUCH higher redline. Going with your choice, if tuned properly, when do you think the .48/.63 will start to boost?


PS: Just ordered the BOV, intercooler, and the charge pipe kit...I'll be taking pictures when I get some items here...

 

nothing is going to be the same compared to the gsr. 1.5L large stroke small bore 73x89.4 vs 1.8L large bore , smaller stroke 81x87.2. crappy head vs great head. dual cam profiles vs 12v/16v setup.

as for the ratio's you put up there, that refers to the housings only. there can be 5-10 different wheel combos in each of those a/r ratio's that you placed.

my vote is a t25 with a .63 a/r exhaust/ and 60 trim wheel with .60a/r compressor housing(s13/s14 nissan silvia turbo). or if the t3 route .48 a/r exhaust housing/ 50 trim wheel .42 a/r compressor housing (80's volvo/ saab's).

if faster spool is wanted a nissan 300zx (z32) 5 speed turbo would be a nice fit. it's a tb22 .63/.48 which is basically a factory t2/t25 hybrid. key word here is 5 speed turbo. the auto's came with .54a/r exhaust housing. they flow 26lb/min which should support 260bhp. there off a 1.5L 3cylinder if you think about it (3.0L v6 twin turbo) and people make 400+whp on stock twins so 200hp in a fit could be possible dependent on supporting mods.(the cylinder head owns the fit!)

I happen to have a couple z32 twin's laying around btw.

 

underdog... talk to me about these twin turbo's u have lying around... I'm interested in picking one up for my build. Does it have internal wastegate, what psi is it set at, any shaft play, clean condition, and does it fit into the fit's tiny ass engine bay.

 

Thank you sir.

 

Will the s13 will spool FASTER then the z32?

 

so the compressor is .48 and the exhaust is .63? Is that backwards from normal?

 

z32 will spool faster as it is a smaller turbo. it's basically a factory hybrid, it's a t2 exhaust side with a t25 compressor. as for being backwards depends on what your looking at. backwards from a t3 or t3/t4....sort of. backwards from a t25 variant, not really. I think you may be getting a/r confused. the most important factor to a turbocharger is the wheels and what size they are=flow. different a/r (area divided by radius) housings help bridge the gap on turbos. example lets say you want a 300hp turbo but want decent spool. now there are two options(aside from ball bearing) a large wheel in a small housing (tight a/r....low numerical) or a smaller wheel with a large housing (large a/r....higher numerical)

so lets say we have a t3 turbine wheel capable of flowing lets say 300hp with a .82 a/r housing. now say you put a .48 a/r housing on it and it "chokes" down the exhaust housing to a max capability of 250hp but gains 1000rpm of spool. now lets say your willing to sacrifice some spool for more power and you want to put on a .63 a/r housing which opens the power potential to 280hp for say 500rpm of lag. as wheel size increases, as does weight which translates into lag. nissan's fix for the 300zx automatic was to put a .54 a/r turbine housing to spool the turbo's faster to eliminate the lag already caused by the automatic tranny. they sacrificed top end power for bottom end power.

now this just goes for the exhaust side of the turbo. a/r on the compressor side deals more with compressor efficency (heat) but also comes with a loss of boost onset (more volume=more time=lag) it is however far less dramatic as the exhaust side.

now lets talk compressor size or "trim" the compressor wheel is the most critical part to match in the turbo. there are maps that show how much they flow and at what pressure ratio's there capable of. going to small with to fast of spool can cause surge issues (which can break shaft's) so for the fit we need a 23+lb/min of flow at relativly low pressure ratio's(low boost)

now lets plug in some numbers here's a z32 compressor map. so lets say were running 8psi@ sea level with a 1psi drop through the air filter(common) and a 1.5psi drop through the intercooler(common on most cheap ic's) puts us at a pressure ratio of 1.7. and lets estimate power @160whp add in 18% drivetrain loss which puts us around 180bhp which translates into 18lb/min of airflow.


this is just generalized info. I might punch in the real numbers one of these days. it's getting late and just wanted to give you guys a estimated idea of what to look for.

 

ok I know I did all the math for this once before. here it is https://www.fitfreak.net/forums/fit-...ulation-2.html

 

Here are the plots from 6psi @ 112% VE ~145whp up to 13.2 psi@112% VE ~200whp
I came up with 112% ve by calculating from t1r's dyno and figuring 15% loss through the drivetrain so these numbers should be close for sea level at 80 degree's with 1psi loss through air filter and 1.5psi drop through the intercooler. realistic VE at 200hp is probably in the 85-100% range with the fit's head.

 

I'm in the same boat u are right now. I just picked up a t25 turbo from a sr20det. No shaft play in extremely clean condition, rebuilt only 5000 miles ago.. got it from zilvia.net for $140.

I just got my intercooler installed and the piping semi-routed. Got it worked so i could keep the foglights.



Intercooler is 27" long by 6.5" tall by 3" thick. It fits perfectly behind the fit's grill opening. I'm also using 2" charge pipes because i didn't see it necessary to go bigger, but maybe i will.

 

koolkevin who is doing the turbo mani for u?

 

The turbo mani i'm going to build myself. I'm going to tack weld it into place, then have my neighbor professionally tig weld it for me. The aluminum charge pipes i'm going to weld myself since i now know how to weld aluminum. =]

 

aight thankss