Alright, so my dad keeps complaining that my car is slow, and that he wants my car to run more boost. If i were to get the "racing beat fuel cut controller" If it were to "trick" the computer into thinking its running lower boost, would that also lower how much fuel its dumping into the motor causing it to run lean?

 

the stock ecu is mapped until it hits fuel cut @8.5psi, once it hits fuel cut, it does not add more fuel.

so when you add the fuel cut defender, the ecu still stops adding fuel @8.5psi, it just does not do fuel cut.

so if you're running 8psi with or without the FCD, the mixture is the same. if you raise the boost the ecu won't know it, and it could run lean.

 

so FCD + 10 lbs boost = pop ? ... good to know, although it crushes my 10lbs goal ill safely stay at stock levels.

 

Some people raise fuel pressure, or drop in larger secondaries (or both) to "safley" run higher boost on am otherwise stock car. The main problem with either strategy is you end up running rich when you dont need to.

 

So what do you recommend i do? Just get an rtek 1.7 or something like that?

 

get the fcd for now (dont go higher than stock boost) then when ur ready to go higher boost get an ecu that will handle the extra boost/ fuel levels

 

that depends. basically it depends on how much power you're making. the more power you have the more fuel you need.

for 10psi, i would run an FD fuel pump (or better), and some sort of ecu. i ran Fcons, but the Rtek is probably better, or you could do bigger injectors and an SAFC.

to go beyond 10psi, you should be looking at a hybrid turbo, like a BNR stage 1.

 

I have an S4 TII and for a number of years ran a Walbro 255lph, proper flowing stock 550cc injectors, and a FCD. I didn't have any sort of fuel control beyond the stock ECU, but I did/do have a Wideband O2 sensor/gauge. And for me, the wideband O2 sensor/gauge is the key if you want that setup to work. You can run your car with a better fuel pump and FCD, but knowing your AFR's can save your engine if it doesn't go right.

Like was mentioned above, it depends on what you have done or plan on doing to your car. It says in your profile that you have a TII swap in your S4, but doesn't mention if it's an S4 or S5 TII engine and whether or not you've modified anything. You're in the same spot I was 5 years ago. When I bought my car it needed a new exhaust, so I got a downpipe, cat delete, and HKS Silent High Power along with a FCD to prevent fuel cut. The previous owner had installed the Walbro 255. With the stock intake plus cone filter, exhaust, and FCD, my car ran consistant 8lbs and sometimes 9, but never higher than 10. So very safe and slightly more fun to drive. But then I changed the intake to this:



Once the intake side was opened up, I instantly started seeing 10-12psi as I redlined 2nd and 3rd, but due to the S4 boost creep problem, I'd see 15 psi if I went above 5k in 4th. 15lbs is scary and dangerous on a stock tuned 145k mile engine. So I tore down the turbo and intake parts of the engine, removed emissions, ported my wastegate, and tried again. Boost levels were in the 8-12 region, but it still had very inconsistant AFR's. Never richer than 12's but usually in the 13's. Not ideal for a turbo engine seeing 10-12lbs of boost.

So like j9fd3s mentioned above, I bought a SAFCII and had that installed. A SAFC is only a fuel controller, so all you can do is add or subtract fuel at given RPM ranges. But it CANNOT account for boost. So mine is set really rich so my car is safe under boost, but it's always rich now. And since it cannot account for boost, it basically gives up above 5500 rpm and can't adjust enough fuel and it'll lean out to 15:1 at 12lbs of boost. In other words, the SAFC helps me from running lean most of the time, but prevents me from full throttle above 5500 rpm in 3rd and 4th gears. I'm glad I have it as it gives me some piece of mind, but it's not the ideal way to go.

The only reason why I explain all of this is because I was once in your same spot, wanting more boost/power and trying to find the most economical way of doing it. If you want to go for the FCD and bigger fuel pump, go for it. I don't regret going that route as I learned a lot about my car that way, but it was risky. It took a lot of effort and AFR monitoring to keep the engine from leaning out and blowing up. At times I almost didn't want to drive it because it was so damn stressful. My suggestion would be get a bigger fuel pump, bigger secondary injectors, and at the very least an Rtek(preferrably one with timing adjustment). My experience shows you can get by with less, but why? I've for sure spent enough on all my changes to get an Rtek, probably even a used Haltec e6k. A proper computer and tune will give you so much more potential and piece of mind. My car still runs and drives, but I'm saving for an engine rebuild and a Haltec at this point. From what I've been through, the first step a new TII owner should do beyond basic maintenance, is a standalone and tune. It's expensive, but any mod that follows can be tuned and accounted for properly.

Oh yea, I had this set-up dynoed and it did 205 whp and 200 ft lbs at 5000rpm. I can't tell you how much it would make at redline as it started to rapidly lean out to 13's+ at 5000rpm. A friend of mine with a similar set-up and rtek dyned at 225 whp. And you can see above my avatar pic, my compression ratios are not very strong.

 

I personally don't like FCD's at all. Timing will be in the area of boost the ECU "thinks" it is. In which you don't have enough timing pulled for even stock boost when a FCD installed.

Common sense tells me that timing is one of the sources of boost creep, not just the lack of wastegate flow.

 

the SAFC goes between the AFM and the ECU, and the problem you have is that the AFM is 100% open, over 4-5k rpms, so the SAFC can't increase the signal because its already @100%. it can DECREASE the signal though, so this is why people put bigger injectors in and tune it down.

the other option the Fcon/Rtek, can change the injector duty cycle directly, so you can just drive the stock injectors harder, which works at the 10psi level

 

Thanks j9fd3s, as that's the explaination I've been looking for, for a long time. No one could explain that or why the TPS measures 100% when it's maybe 25%. We went through all the settings and it seems like you can't zero out the TPS on the SAFC. Currently, my lo-throttle settings are only good for idle.

I probably won't mess with that now as I'm just driving it til the 150k engine lets go and I rebuild a JDM S5 engine and install a Haltec. The sad thing is I know all I need is a pair of injectors to remedy my leaning out issues, but I didn't realize the previous owner used an incorrect secondary fuel rail bolt until it was too late when I did my emissions delete. When I was tightening the fuel rail bolt it split the LIM threaded area. If I take the rail off again, the bolt wont hold. I have a set of S5 upper and lower intake manifolds, but seems like a lot of questionable work for an engine that could let go any day....

 

Stock timing is by far the most dangerous part of this recipe.

To compensate for the fact that the stock turbo is limited to 6.5 psi stock (and has trouble holding anything more to redline) the stock ecu starts adding timing (presumably after peak torque?) to the tune to 34* or more in some areas.

The SAFC can't do anything about this, nor can an FCD. You could just pump in the fuel to keep afr's in check but that's putting a bandaid on a stab wound. That's not to say that others haven't done just that (680 secondaries, FD pump, FCD, and a big bag of Puerto Rican luck up to 10-11 psi) and kept their engine together. TIIFC3S had a good point, by the time you play around with all these little work arounds you could probably afford a real solution.

 

the S4 TPS primarily runs the Air Control Valve, and some other emissions equipment, for anything more than 20% throttle the ECU is using the AFM.

i wouldn't lean on a 150k engine either, but more fuel will keep it together longer....

 

+1, the VE is falling off really rapidly, so timing increases. when you add a bigger turbo, VE doesn't fall off and you're suddenly running a LOT of timing (more than an NA car).

that being said, you can make a LOT of HP on the stock ECU, a friend of mine was running a 60-1@15psi with the stock ecu, and it lasted 30,000miles. he was deep into the 12's in 1994, and the car got an REW swap in 95-96...

 

a friend of mine has a 10th AE with street porting, RA super seals, Stock ECU, high volume Denso fuel pump, 750cc secondary injectors, FCD, he's running 10psi of boost and the AFR's are at full throttle and redline in the 10.8-11.3 range but he's running rich at idle and low rpms with 11.5-12.0 range. He's been running this set-up for a year now with no apparent problems other that the terrible smell of unburned gas at idle and low speeds...

 

anyone know how to tell the difference between a S4 and S5 fuel cut controller?

 

I'm not aware of any difference other than the serial numbers.

It's a moot point anyway because fuel cut controllers have been outdated by the Rtek Stage 1 ECU upgrade. It is about the same price but with way better features, and the Rtek allows you to use the stock boost gauge.
Rtek7 ECU Upgrade Detailed Information