Ok I'm not too familiar with stock capabilities so I wanted to put this out here.

-Large streetport engine with S4 rotors
-Walbro fuel pump
-Cleaned 550cc injectors
-Stock ecu
-Front mount intercooler
-RR Fuel pressure regulator

I've already ported the wastegate on the stock s4 turbo. I wanted to know where the safe zone is on boost is. I have a wide band but really don't want to dish out cash on a SAFC since this setup is just to get me around while I work on something else.

I was thinking 8 to 10 psi would be the max I would be comfortable with, but a knowledgeable friend told me to consider the streetport and that I would need a piggyback and larger injectors.

So any thoughts would be awesome. I want to keep it safe and keep the cost down as it will be my daily. I'm very open to even keeping the boost around stock levels but would like to know if I can get a couple more psi out of it.

 

8-10psi should be ok, but keep an eye on the wideband. You can always bump the fuel pressure up a little, if it gets lean (aim for 11.5 AFR). The most likely spot for a lean condition will be in the ~3500 - 5000 RPM range.

 

Personally, i would browse around ebay, craigslist, or this very forum and find a SAFC if you intend on bumping the boost up any. At most you're going to spend a couple hundred bucks and spend an hour of your day putting it in, then another 30 minutes deciding where to add fuel as you watch the wideband.

 

That sounds like a good idea. I just needed someone else to say it I guess.

 

Yeah, its best to make sure you can adjust the fuel before turning up the power. a cheap fuel controller that you wont use but a handful of times vs. the rebuild that happens from turning up the boost without adding more fuel.

 

WAIT!!!!!!!
YOU need a fuel cut defender. FCD. Stock ecu cuts fuel to the rear rotor at around 8 psi.
You can easily pop your motor boosting past 8 psi without a FCD.

ALso. DOnt worry about a SAFC. GEt 720cc secondary injectors. stock ecu works great with it. I run 10.3 afrs on similar setup. Too rich but hella safe.

YOu have large streetport. I highly recommend bigger secondary injectors. IFFFFFFF your engine boost creeps past 8 psi... BAD BAD.


FCD AND 2x 720cc injectors is what u need.

 

I've got an FCD. I guess I should have mentioned that.

I'm thinking that bigger secondaries will have to become a reality with this setup, but I still have to break this engine in and I'll keep the boost down until I ****** up some 720s.

 

Don't run 720cc secondaries on a stock ECU alone. Get the Rtek 1.7 or an AFC if you want to do that. 10.3 AFR is too damn rich, and will cost a lot of power / potentially cause misfires on the stock coils. You can run mid 11s and be nice and safe. Uncontrolled 720cc secondaries will allow approx. 15% more total fuel in above 3800 RPM, which is completely overkill. With my Rtek 2.1, I only run about 1-3% more fuel than the stock map in the 8-10 psi range, and have solid 11-11.5 AFRs.

The stock ECU's fuel map is actually adequate for running additional boost on the stock turbo, and 550cc injectors can still keep up ( but at high duty cycles). The main reason turbo engines blow on stock fuel systems is the fuel pump. At higher-than-stock fuel pressures, the stock TII pump's flow rate takes a dive. At that point, it doesn't matter how quickly the ECU fires the injectors or what they can flow, since the pump can't keep up. A walbro alone w/ the stock FPR is a crude, but effective solution for this problem, and will even bump up fuel pressure on its own (overwhelms the stock FPR). An adjustable FPR will be even better, since it can tame the pump at low pressures, but still allow high flow under boost.