Xbladr

I will be installing a new turbo and manifold in the spring along with a 3" dp and exhaust. I am trying to decide what size injectors to go with. I will be using the rtek 1.7 and most likely an safc. Here are the specs on the turbo

Garrett T04 60-1 Turbo
.62 TRIM
.60 A/R
.86

any help would be appreciated.

I posted this in the second gen forum but slpin was the only member to reply the general concensus was 800+cc secondaries and 720cc primaries... does anyone else think I can get away with the 550 primaries and like 920 secondaries or would upgrading primaries be a necessity... also what kind of power could a turbo like this make on avg

now

iTrader: (1)

depends how much boost you are going to run it at.
matt

Xbladr

Well It is on a stock s4 engine... so i prob wouldnt run it any higher than 10 psi or so maybe 12 but that will depend on what bpr perfromance in salem MA want to tune it to

now

iTrader: (1)

12psi
i would use the stock primaries and 680's on the secondaries.
lots of people will say this is to small but with these sizes it will be much easier to tune
your not really that far off stock.
matt

Xbladr

SO that is a pretty comparable turbo to the stock S4 turbo? For some reason I had thought it was much larger in size... Thank you though anyone else have any opinions?

now

iTrader: (1)

you could have a turbo the size of a house if you are only going to run 12psi boost
the fuel demand is the same, you only need to add more fuel when you add more boost
matt

Xbladr

well 12psi on a large turbo is different than 12psi on a small turbo the flow characteristics are much different. so you are saying 12psi on a small t3 turbo is going to produce the same as 12 psi on a t66 turbo? I dont think so the size of the wheel and turbine housing change a lot of flow characteristics. The hp potential should be relative to the injector size not psi i dont believe. But this is only speculation

now

iTrader: (1)

12 psi is 12 psi
if you dyno 260hp with a stock turbo making 12psi
any other turbo which can match the same psi will = the same hp.
more psi = more air which in turn requires more fuel = more power.
only time you get more hp out of the same boost is in exhaust changes or porting,
treat it like a n/a motor how do you make more power with a n/a?
some of the same things that will = more hp from a n/a will have similar affects on a turbo
with the exception of compression ratio.
matt

Kahren

iTrader: (13)

12 psi is not 12psi, pressure and flow are related but they are not the same thing. a large turbo makign 12 psi will flow much more then a small turbo with 12 psi. flow can change with same psi.

now

iTrader: (1)

if all else stays the same but the turbo
flow through the motor will be the same.
think of the motor as a restriction to flow in a pipe,
the only thing that might change a little is the temperature of the compressed air coming out of a larger turbo
being a little cooler, in a 2nd gen the ic is quite efficient and the difference after the intercooler would be hard to
even measure.
the only big difference would be in the amount of restriction difference between
the exhaust restriction of the two turbo's .
I still feel that stock injectors in the primaries and 680's for secondaries will
be enough for 12psi

RandomHero

iTrader: (2)

12psi is not the same for different size turbos at all. 12psi on a stock turbo is pushing it out of its efficientcy range, where the charge air will be hotter in comparison to 12psi on a larger aftermarket turbo that (if sized properly for that boost level) will be inside its innermost effecientcy range on a compressor map. Where the charge air will be cooler and more dense, therefore requiring additonal fueling (and making more power). Dont think of the engine as a restriction in a pipe, think of it as the pump thats moving air through the pipe, becuase thats what it is.

Can you do all that with the factory pump and regulator?

Kahren

iTrader: (13)

stock turboII fuel system is good for around 220whp, if you want to be safe get bigger secondary injectors and fuel pump. 680s are brely an upgrade for secodnaries

now

iTrader: (1)

I built a TII did some porting on the motor, and the turbo as well as the waste gate
ran 550 prim and 680 secondary's, supra fuel pump 12psi boost, chipped stock computer
3" exhaust, safc to fine tune with and was making well over 220whp. no problems.
the guy i built it for was talked into "the bigger injector world " and went to 680's
and 1600's had nothing but problems trying to tune it and ended up blowing out side seals.
when i asked him why he wanted larger injectors he said because he was told he needed
them. wasn't going to run more boost or anything but needed more fuel capability.
my 2 cents
matt

now

iTrader: (1)

btw 680 are almost 25% more capacity over 550's

BASTARD

iTrader: (4)

More air means you will need more fuel...No if's no and's and no but's about it... there are many many many discussions about injector size and fuel pumps on this forum as well as turbo size Vs. horsepower… there are so many variables it can make your head spin. I am by no means an expert on this subject, however I do have a stock S4 TII motor with a To4e an Haltech with the 3” DP and a hi flo catalectic converter. I have a FD fuel pump 750 primaries and 1680 secondaries (defiantly overkill for the secondaries) put down 288 RWHP@10psi on pump fuel with a mild tune. I would say you have to change it out any how so you might as well replace it with a Cosmo or Walbro type pump because if you want more out then 10psi with a 60-1 the FD pump may not be enough.

Fuel injectors 550/680’s may be enough for 10psi if you crank the fuel pressure up but why when you’re replacing all this stuff anyhow and what if you want to bump the boost up to 12 or 15 later??? I would run 680 or 750’s in the primary and go with 750 to1000 secondaries. You can always cheat a little by adjusting injector time and fuel pressure. RC Engineering said they were coming out with a 1000cc drop in replacement for about 100 bucks.

Get a fuel pressure regulator as well

Just my .02 worth… do a search there is tons of info and ideas

patman

iTrader: (3)

really simple. take the HP you want, and multiply by 7.65. that is the sum of your injector flowrates in cc/min.

so if you want 500 BHP, you need 3825 total cc/min. if you keep stock primaries, then thats 3825-1100=2700cc/min for secondaries = 1350cc each.

7.65 is based on a BSFC of .6 and 80% duty cycle. this is a fairly standard conservative number for highly modded 13B.

i personally run stock 550 primaries and 1260 secondaries, with my af61r at 17psi.

pat

Dom_C

Using the method above, the stock injectors should be good for over 285hp. So say 250rwhp? That's not to bad.
Dom

Kahren

iTrader: (13)

bsfc of .6 is on the lean side for a turbo rotary. it is more like .7 that you want to use. and stock injectors are not good for 250whp, it is more liek 220whp.

Dom_C

Yea I guess that sounds correct. 20% of 285 is 57, the 20% is the drivetrain loss so 220rwhp sounds about right. Thanks
Dom

patman

iTrader: (3)

bsfc for a rotary is generally in the .55-.6 lb/hp-hr range. and i personally ran 12psi with the stock injectors and a t4, which should have been well over 220whp, tho i never dynod that setup.

pat

Kahren

iTrader: (13)

.55 is around 12.8 afr .6 is about 12.0 a turbo rotary needs to run richer then that to be safe.

patman

iTrader: (3)

there is no direct relationship between afr and bsfc. bsfc depends on many factors, including but not limited to afr.

Kahren

iTrader: (13)

that is correct, but most of those things are pretty close to a constant.