A rough outline of the planned (re)build;

S4 NA 13B, all original parts w/ new front iron
Streetport or small bridgeport
Stock or T2 injectors (primary/secondary/all)
Functional 6PI
RTek stage 2 ECU upgrade
RB header
Port-matched & polished intake

Now, i've put a fair deal of thought into this build already, but I crave some feedback / naysayers. Just to test my theories with/against to make sure I haven't overlooked something critical. Any input would be greatly appreciated!

 

I would consider to try to get your hands on s5 na rotors and counterweights if your going through with a build. S5 intake manifold too. The s5 intake manifold could be done later bolt on, but once the engine is built, you wont be able to do the rotors later

 

I take it this would be due to the higher compression of the S5 rotors? I'd be willing to go with the S5 intake though for several reasons; I've read the S4 NA intake to be more restrictive? That, and the S5 6PI system is exhaust back-pressure operated, correct? The rotors I'm reluctant to swap: with my current S4 rotors being in pristine condition and with short block / internals scarcely available and hella expensive over here in Holland it wouldn't feel right ditching the original ones. On the other hand, I'm after NA power, so I might be convinced if along with my other mods the gains would prove substantial enough to make it worth while. Anyone?

Edit: If rotor-swap, the original S4 NArotors would be a good thing to store for later turbo applications? Or were those the S4/S5 turbo rotors? Additionally; would RX8 rotors be an option compression-wise? They're lighter right?

 

The S5 6PI system controlled by the computer and uses air from the air pump. If you use the S5 manifold, you'll need to use an RPM switch and extra emissions solenoid. It's not plug and play.

 

Yeah my bad. You see, the thing is; mine's a Euro FC so the 6PI is the butterfly-valve system with the actuators connected through a vacuum solenoid to the intake manifold.

While on that topic; I've noticed the RTek 2.0 for the S4 doesn't support 6PI/VDI control. There is - however - the possibility of adding one or two RPM-triggered functions. Could something be made to operate the S4's solenoid-switched vacuum operated 6PI from these programmable functions?

thanks for the replies!

 

US S4 don't have any electrical part to engage the actuators

Except the ACV i guess, but thats more emissions i believe

 

Without knowing your ultimate goal for the car, it's hard to give feedback. If you're on a tight budget, the S4 rotors and intake will be fine. If you have money to buy rotors, the S5 rotors with front and rear counterweight is a good upgrade for any build. The S5 intake will make more power on the top end from 5000rpm to redline, but the S4 intake has strait runners for better power and torque down low. For a daily driver, I prefer the S4 intake over the S5. So yeah, lots of options depending on your goal...

If you're on a budget, I'd say stick with the parts you have and get a light weight flywheel. Even the lightweight steel flywheel from around $300 US is better than the stock. Best money you'll ever spend to wake up a non-turbo.

Don't waste money on the turbo injectors. You will never run out of fuel with the stock injectors on a non-turbo. If by some miracle you did run out of fuel, a Turbo II fuel pump would be cheaper.

-Jeff

 

With your list, I'd eliminate the bridgeport thought. Streetport only. As far as injectors go, you've got more than enough. Your fuel pump is fine too. The recommendation about the flywheel is a good one. It has always been my favorite must do mod. Well, that and a header. If your motor needs to be rebuilt, as in it's about to die, go ahead and do a port job. If your motor is fine, spend your money elsewhere first.

 

If you have a euro spec S4 that mean you still have the distributor with two coils/igniters as well. Sadly without wiring the us spec ecu wont work on your car, although if it did iirc the s4 rtek ecus can set the egr output as a rpm switch.