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Forum nameTurbo/Nitrous Tech
Topic subjectCar falls on its face past 5000 rpms
Topic URLhttps://forums.2gnt.com/dcboard.php?az=show_topic&forum=i8&topic_id=103477
103477, Car falls on its face past 5000 rpms
Posted by seancrosariol, May-01-08 05:27 PM
I just want to say that im not a frequent poster i gather most of what i need from the search so please do not be too pissed that im asking a fuel question. I recently got my fully built motor put together and have had issues tuning it. I have not yet turboed the car but that is coming soon. Right now i have 440cc injectors, a vortech sfmu, and a 255 walboro which make up my fuel system. i have seen that tons of you guys have this setup and there is loads on info on it. I tried to mimic your fuel pressure settings but my car seems to still be getting to much fuel past 5000 rpms. (fuel pressure is set at 18 and when i rev the motor it jumps to 28) The car seems fine on the low end but it pretty much floods out and falls apart at 5100 rpms. I was also wondering if changing the disc inside the sfmu makes any difference on idle or static pressure or are the dics merely for when you turbo the car to raise the fuel pressure under boost. and lastly i was wondering what exactly adjusting the vacumn screw on the sfmu accomplishes. Is that how you adjust the idle or static pressure. Please help me if you can. and again i apologize to the donating members who are tired of answering injector and sfmu questions but vortechs instructions leave a lot to be desired.
103478, RE: Car falls on its face past 5000 rpms
Posted by DarkOne, May-02-08 02:54 AM
Sounds like you're using too big of a spring / disk combo. What are your boosted fuel pressures like?

103479, RE: Car falls on its face past 5000 rpms
Posted by seancrosariol, May-02-08 04:17 AM
i do not have a turbo on the car yet. it is still nt.
103480, RE: Car falls on its face past 5000 rpms
Posted by wickedtalon, May-02-08 04:23 AM
Should have put the SFMU on at the same time the turbo goes in. No need for the sfmu and 440s when you're NA. You're dumping fuel in because the rising rate fuel pressure regulator is doing what its supposed to and raising the fuel pressure. You may have the sping/disk set up for turbo application but you have no turbo. Add the turbo now.
103481, RE: Car falls on its face past 5000 rpms
Posted by seancrosariol, May-02-08 04:35 AM
so is there no way to make this work for now
103482, RE: Car falls on its face past 5000 rpms
Posted by RoninEclipse2G, May-02-08 05:04 AM
nope, sfmu and the injectors are just washing your cylinders down in preperation for the boost that you don't have
103483, RE: Car falls on its face past 5000 rpms
Posted by seancrosariol, May-02-08 09:04 AM
so whats my solution put a turbo on or run a more stock fuel setup. i find it hard to believe that there is no way to make these 440 injectors work on a na motor that is flowing a ton of air with a venom intake manifold, turbo cams, extrude honed head, oversized valves and a cold air intake. I had to max out the stock injectors just to get the plugs to brown up a little before.
103484, RE: Car falls on its face past 5000 rpms
Posted by RoninEclipse2G, May-02-08 09:49 AM
I'd say boost or remove the SFMU and tune the injector pulse down to something that isn't flooding the cylinders. you could also remove the sfmu and run E85, that would put you close to stoich for the ethanol
103495, RE: Car falls on its face past 5000 rpms
Posted by justins71, May-04-08 02:04 PM
You need something to control those huge injectors on an NT. SAFC, Emanage, MSNS, something. As is, it works out you need about 11psi static fuel rail pressure to get equal flow to stock injectors and hp. The SFMU disks won't change anything, or cause it to dump fuel anticipating boost because there's no boost reference to raise the pressure. On the Vortech manual, you set the top static screw (with no vacuum reference - again, you'd need a horribly-low 11ish psi), then plug in the reference hose and adjust the side vacuum screw for idle psi (theorectically should be almost 0). You're better off just leaving in stock injectors if you don't have something to lower your pulsewidth.