dcamcoTII

I'm looking to upgrade my fuel system on a budget. Has anyone here run 720cc secondaries on stock tuning?? is it REALLY worth it to buy the safc?? I'm running a mild streetport, full intake/exhaust, series5 turbo, and I have a walbro 255. I'd like to get my fuel resolved before I drop th enew motor in and fire it up.
Thanks in advance

FC Drifter

720s are a definate must for the mods you have. but to answer your question, i do think the s-afc would be worth it. i have 720s in my T2 and they arent tuned yet. the car gets horrible gas mileage(around 8 mpg) and it isnt as fast as i know it can be. to me its worth it.

NZConvertible

Injecting 15% more fuel into you engine is going to result in a definite loss of power from running horribly rich. Probably black smoke too! You'll definitely need an S-AFC to tune them down to more suitable mixtures.
Here's something else to think about. Have you had the car dyno'd so you can see if you are indeed running lean? You don't mention how much boost you're running or if you're experiencing boost creep with that S5 turbo. This is something else a dyno run can show. AFAIK the stock turbo on mild boost (~10psi) cannot make much more than 250-260hp (can anyone confirm?), but the injectors are able to flow enough for ~300hp @ 80% duty. So it's not the injectors that are the problem, it's the stock ECU and the fuel pump. You've taken care of the pump, so get it dyno'd to see if you really need to add more fuel via an S-AFC. If you do, get one and get it dyno-tuned.
When you get it dyno'd, see if they'll also measure boost pressure and injector duty cycle. If you can't get rich enough mixtures without exceeding 80% duty cycle, then you need bigger injectors. 720cc/min secondaries will only be good for ~45hp more, so consider how much further you plan to upgrade.

dcamcoTII

well I haven't even started the motor so I have no idea what my boost will look like, but i plan to keep it around 10psi. I am just assuming I will run lean and taking necessary precautions. So are you saying that I should just try an safc for starters on the 550's? The reason I wanted to put the 720's in is because i figured it would be much easier while the motor is apart, plus i know i will need them if i want to do anymore upgrades. I plan on going all the way with this motor so my next planned mod is a haltech, which is the reason i wanted to avoid buying the safc.

RX7Kid

I have 550 primaries and 720 secondaries i also have a s-afc i was a 8 pounds of boost on our dyno and we had 193 HP at 12 to 1 airfuel a little rich but the boost on the street is 13 to 15 pound depending on the intake air temp. This is on the stock intercooler so it gets heat soaked almost instantly on our dyno so we cant get full boost like on the street. I do not have a boost controller i am going to put on a manual soon just lazy i guess. On my power curve if you calculate the HP at 15 pinds off bosst i am around 260 , Not bad for a motor with 60,000 miles.