I have been letting my RX3 remain NA for too long. I want to run the turbo now. I still have the stock injectors in it so they will need upgrading. I would like to have good drivability since this is a street car.

What injectors would you recommend for the parts I have?

2 x Walbro 155s (Total flow capacity 45gph @ 50psi)
MicroTech LT-8 ECU
Cosmo 13B-RE (currently stock ports, but will soon street port likely w/ clipped '86 TII rotors)
Garrett TA0413 (Equivalent to a 60-1)
FMIC 24"x11"x3" (2.5" piping)
3" exhaust (RB universal main and pre silencer)
Tial 46mm (10 psi spring) (more boost to come later, say 15psi)
TII coils w/ MSD 6AL on leading coil

Thanks

 

Paul Yaw of Injector Dynamics has probably the nicest injectors out there. As far as I'm concerned there may as well be no other companies out there.

http://www.injectordynamics.com/

 

My fuel pumps limit me to about 450 flywheel hp and I am OK with that limitation. I just finished playing around with kgparts' fuel injector calculator a bit...

Stock 550cc injectors calculate to being good for about 140hp. The additional 310hp equates to 1220cc secondaries. I know that there is usually some art to connect theory to practice. With no experience my guess is to 1200 or 1300cc injectors with the same resistance as the primary injectors (Don't know that value yet though)

My friend says to just put 1680s in the secondaries and call it done.
I see others going YAW with 1000 x 4.
Some rave for 720/1200.
Saw one impressed with 800/1600.

 

i would go 720/1600's...better to have more fuel than not enough and your microtech can tune them.

 

550/1680 or 720/1680 will be plenty. get the ones that fit into the stock s4 rails. I'd honestly just do 550/1680.

also, the dual fuel pumps for a 60-1 class turbo seems overkill to me. i used to run a single Supra pump on my T04S 60-1 up to 21psi with no problems, after rewiring the pump and bypassing the resistor relay.

 

Long story short on the dual pumps...They were left over parts and their flow output added up to about what I should need with the turbo. They are setup already, plus if one dies I can limp home since they are in parallel and have built-in check valves.

 

Yaw has always impressed me.
I have been reading through the site, trying to get educated.

It looks like fuel injectors have come a long way since 1990.

 

If you have a 87-92 NA 13B, the stock injectors flow about 458cc/min @ 37psi, and are commonly called "460cc" injectors on this forum. You may want to verify your current injectors if you plan on maybe just buying new secondaries to reach your power goal.

I think you have an error somewhere unless you are running a really low fuel pressure. The stock S5 NA 13B is rated for 160bhp with the stock 4 x "460cc" injectors, while the stock S5 13BT is rated for 200bhp with the stock 4 x "550cc" injectors.

For 450bhp, you are probably looking at somewhere around 3700-4300cc/min total flow, depending on the fuel pressure, intercooler efficiency, porting, tuning, etc.

In general, better performance is posssible with the smallest injectors that will support your target fuel flow while maintaining an acceptable duty cycle. Most people take a SWAG at the fuel requirements, and then just round up to the closest injector sizes.

 

Motor is a Twin-turbo Cosmo 13B-RE with turbos not used. I removed them to help keep things simple for the first step of my efi conversion. So, 550cc x 4 is what is stock right?

 

isn't the factory primary rail for side feed injectors or something? I thought the RE was weird like that

 

Yes, side feed primaries. Getting away with upgrading secondaries only would be nice.

Are there any major problems/ short comings with 550cc/1680cc? Where to get 1680cc TII style top feed matched flow/resistance injectors? RC Eng, Marren?

 

either. or you can get bosch style injectors and witchhunter will modify them for something like $5 each.