15psi Still A Fuel Cut With SAFCII???

[MkIIIJoe]

Mods:
Intake K&N
Full 3 inch exhaust
DM Downpipe
DM Intercooler kit with BOV
57 trim
Turbo xs boost controller
walbro 255
stage 2 clutch
SAFC2
waideband
boost gauge
Lexus afm

Might be missing somethings but heres my case. Everything is on the car, did some tuning myself with some highway pulls. Boost is set at 15psi, if im at 3000rpm and dump it in third it will hit fuel cut reaching 15psi then ill shut her down.

it wont hit fuel cut if i roll into it (slowly put my foot to the floor) and the A/F is the same but stays at 15psi, and if i turn it up a little it will hit fuel cut at WOT

can i correct anything with the SAFC? why is it hitting fuel cut when i have all of this installed.

Fuel @ WOT is 10.8-11.0

[supra_sicc]

Yea with a lexus afm your allowing more unmetered air thru which will cause a leaner condition, which then your ecu trys to pull more fuel out. But with only 440cc injectors wont happen. Get 550s

[MkIIIJoe]

even if the car is running rich under WOT?

[MkIIIJoe]

i have 550's and a AFPR at my apt im putting them in this weekend

[93 twintrbo]

Fuel cut depends on maf voltage into the ecu. If you lean the car out to high 11 a/f it will not likely hit fuel cut unless you raise the boost ( dropping the voltage back to the ecu).

[1QwikMK3]

What the others said. I would adjust a/fr's to around 11.5-11.8 range, this will allow you more boost due to the fact that you would be reducing the maf signal to the tccs. Another thing you could do is remove or adjust out the air screw in the lex afm as sort of a coarse adjustment. You should be able to gain about another 2-2.5 psi with the screw out, just keep an eye on the afr's when you boost cause this will lean you out a little also. It's also possible that you could have a slight boost leak. Air is going in through the maf and being accounted for, but you may be losing some of that metered air on the pressure side and thus lower boost pressure than it should be for the given amount of air going in.

Another thing is MBC's (I think thats what you're running) tend to spike, thats why if you roll into the throttle and let pressure build slow you're eliminating the spike and aren't hitting fuel cut. If you decide to go electronic you'll have more steady boost control.

Good luck!

[Wreckless]

Yea with a lexus afm your allowing more unmetered air thru which will cause a leaner condition, which then your ecu trys to pull more fuel out. But with only 440cc injectors wont happen. Get 550s

The Lex MAF housing DOES NOT let in unmetered air. The Lex/550 combo was a workaround trick to use a larger MAF body so that about 20-25% more air would be entering the engine for a given MAF output value, which in turn would match up with the ~25% more fuel added by upgrading from 440cc injectors to 550's.

To use the Lexus MAF with 440's simply means you have to 'pull' MAF signal with an SAFC to compensate accordingly, and by reducing the MAF signal you're raising your boost cut point proportionally. But you'll need to run a bigger pump, and possibly an AFPR if you need more fuel at a given SAFC setting, but can't add more MAF correction due to boost cut. In which case you can bump your base fuel pressure by a few PSI and adjust your whole hi throttle map to suit.

Long story short, if you're seeing a boost cut around 15psi at a given RPM under certain conditions, and your A/F is safely into the 'fat' range at 10.8-11.0, simply pull a few more % in that RPM range on the SAFC.
While 10.8-11.0 is certainly safe, you could bring that up to 11.3-11.5ish and probably pick up some more HP safely. Of course, keep a sharp eye on A/F's and make small, gradual changes with an SAFC.

[MkIIIJoe]

you guys are spot on, while on my way home i was messing around with the SAFC, pulling some fuel out 1% at a time and yes it did work, i even turned it up to 16-17psi thus compensating for the extra psi while still pulling fuel at a very safe A/F ratio.

now running 16psi and A/F is about 11.0-11.4. running great. this weekend, im still going to add the injectors and Regulator and tune from there.


People get all scared to tune their own car, but in reality, with the SAFCII theres nothing to it, ill go get a pic of what my cluster looks like to show how and what i see when tuning

[DegreE_v.2.0]

Good shit. I can't wait to get my turbo back so I can start tweaking my SAFC.

So you're still on 440's and rocking the Lexus V8 MAF? Interesting to see those AFRs with your set up.

I have the V8 MAF as well but its sitting on a shelf until I upgrade from my 440's. But I may install it to see what happens after seeing this thread.

[MkIIIJoe]

[MkIIIJoe]

yea, some ppl say they dont see a problem with the 440's but as long as i see good A/F then i dont see a problem. always keeping an eye and maintenance up on it

[SupraTrey]

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