Hi guys. I researched my question, but didn't really find any answers to my question. I'm currently in the middle of a rebuild for my S4 TII and am planning on the Rtek 1.8 as my ECU for the time being. For the past couple summers I've used the stock 550 injectors with stock ECU and SAFCII for fuel control. Even with the SAFCII maxed, I've leaned out above 5,500 rpm, so I really haven't been able to boost it hard for a while. At this point it's obvious my stock injectors can't keep up with my exhaust; downpipe, Racing Beat presilencer, and HKS Silent Hi Power exhaust, so I need to find a way to control bigger injectors. It runs pretty well and spools fine, just can't really drive it hard.

I have a friend running a 1.7 on his freshly rebuilt S4 TII (Rebuilt S4 turbo, full exhaust, very minor streetport, top mount) and had great success with the 1.7 up until he started to go lean at higher RPM's. His builder said after the dyno runs that with a SAFC, he'd be able to solve the lean issue and be good to go. In the future I plan on a full standalone, but rebuild costs have prevented me from going to a standalone now. I'd go with the Rtek 2.1, but since I already have a SAFCII installed, I figured the 1.8 would be a good starting point for my ECU needs. When completed, I'll have a streetported S4 block, S5 turbo with ported wastegate, S5 intake manifolds, front mount, and the exhaust previously listed.

Sorry for all the background, but want to make sure everyone knows what I'm working with. I'm about to buy some RC injectors and I have the option of 750's, 1000's, and 1200's. I'm wondering if I should step up to 1000's for my secondaries since I have the SAFCII to adjust the extra fuel they provide? I've read a bunch of threads on how 4 720's are good for 12psi safely etc etc. I don't plan on running any more boost than that. But I figure the extra fuel will be nice with all the extra flow from the street port. Or should I just stick with the 4 750's as that will be more simple and sufficient for my build? I know the 2.1 would give me more tuning options. But being so cost effective, the 1.8 with SAFCII seems like it should be able to hold me over til full standalone. So it would be great to hear from anyone with experience running the bigger secondaries and if that would be a good direction for me to go.

Thanks in advance for any help.

 

Whoops, can't edit the title. I mean Secondaries...

 

Stop playing with fire and get your self the rtek 2.1 and i hope ur running with a wideband.

 

We always recommend a stage 2 when you have any sort of port. You can't get the granularity you need to properly tune with an AFC to properly tune the midrange. And don't expect to be able to tune an AFC for larger secondaries. It looks at TPS and RPM. But the secondaries can be on or off at the same TPS and RPM, so if you tune for off, you'll be rich when they are on, and vice versa.

 

I installed a wideband when I installed my exhaust, so I'm very familiar with using it to keep things safe. It's the reason I know I lean out above 5k.

Looks like I have some more research to do. Thanks for the help