Ok, everyone talks about how hard it is to tune stock 550 primaries with 1200 or 1600 secondaries, soooo

I have a stock port 1987 13B turbo engine with about 5000 miles on it, stock S5 turbo, 3 inch turbo back exhaust with Apexi N1 muffler, LT8S via laptop, NPR front mount, and 4 stock injectors that are on their last breath. Im looking to keep this setup for at least another year cause Im a poor bastard. So with 4 new RC Engineering 750cc injectors I should have enough fuel for this right? I have no boost controller and dont really see more than 10-12 psi of boost.

The main reason I want to do this is because Ive heard the RC 750s will drop right into the S4 turbo fuel rails, correct? (I have heard of some O-ring issues that require extra or bigger O-rings, can anyone elaborate?)

 

I believe for the price, RC sells 1000cc for the same price. I would go 4 1000cc all together. It will also give you room to grow in the future. Right now i am using them. No complains here..

 

I use the RC 750 x 4 now on a ported engine with a BNR stage 1 turbo. You should have enough fuel.
I had to grind the casting flange between the primary injector ports to get the fat body RC's to fit.
I have a 88 S4 so I imagine you will have the same cast web between the ports.
I used the stock grommets with no problems.

 

I use 2 GSL-SE 700cc injectors and two RC 1000's.... and yes the 1000's are the same price as all the other smaller sizes. It's when you go above 1000 when they become "custom" and more expensive. As far as the o-rings, all you need is another mazda oring at the bottom...use the same one as the top, mazdatrix sells them. Make sure RC doesnt give you honda o-rings (I think they are blue instead of black), they are the wrong size.

 

Cool! As long as I can retain the factory fuel rails Im happy. Yeah, I might just go with 1000cc secondaries just to be well prepared. I just adjust the %stage right? Like from 50% right now to 60 or 65%?

 

On the Microtech? It's easy. If you are using 550CC primaries and 1600CC secondaries, set the %stage to 95% and then tune as normal. The "backwards staging" of the Microtech makes tuning staged injection a breeze. For 1200CC, 70% or 75% is probably close.

65% sounds about right. You may need to experiment with this number a bit. If you are running all 720CC, keep the %stage at 50%.