car starts to stumble just a bit and power drops off after 5,500rpm at WOT. my narrowband pegs lean during this condition leading me to beleive not enough fuel :[

ive already:
new plugs
new fuel filter
new fuel pump

the car really shouldnt be running out of injector, im boosting stock series 5 wastegate pressure (just south of .5 bar)

the engine is S4 with rtek 1.5 and stock injectors, less restrictive intake elbow, front mount, free flowing exhaust(for the moment i have the silencer in the tailpipe)

car has had gas tank problems in the past which led me to the filter and pump, but these didnt change it at all, maybe the injector screens are clogged?

im also going to see if maybe its an AFM problem, otherwise im kinda stumped :[

 

Your exhaust is probably getting you. When I went from stock exhaust to 3" turbo-back, my "running off wastegate" boost went from the stock 6 pounds to 13 pounds. Now the S5 wastegate is better about creeping, but it will still let it creep up to 10 pounds or so.

 

Yes. Mine crept to 9 psi from full exhaust only.

Do you have a FCD?
What kind of fuel pump are you using?

 

no i do not have an FCD, the rtek was supposed to take care of that. then again only running 7psi according to my boost guage

fuel pump is a walbro 255lph

 

i suggest u dont run it hard till u figure it out.

 

OK i have the exact same problem with my 88s4 with the rtek 1.5 It doesnt always happen though, sometimes it will rev to redline with no issue. so i usually shift at 5 grand because of the very unsafe sounding spitting noise. I hate it and have not found a solid answer to this problem. ******* rtek1.5 should have fuelcut defensor built in but i peak at 5lbs of boost anyway so it should not matter. I have talked to local rotory guys who have never heard of this issue and have to constantly explain that it isnt at 3800rpms. Who else has had this problem?

 

Did you REWIRE the fuel pump? If it's getting only 10 volts it may still lean out on you.

you do need to check injector duty cycle if rewiring doesn't help. I think the SAFC II can read it (not sure , i had an SAFC 1) some electronic boost controllers can as well, and of course standalones can

 

i swapped my 13bt motor into an se model so rewiring (i think) isnt necessary. Is there such thing as a rentable "duty cycle tester"? I have no boost controller or safc, just a ginormous wastegate that luckily maxes out at 5psi and 550 primarys and secondaries. Thank you for your help and keep it coming.

john ny

 

just installed a phase narowband and it says that i am running rich when this problem occurs. I think i just wasted 35 bucks and 2 hours. Do all narrow bands dance around like crazy? All mine does is say rich on accelleration, lean on deceleration. I think a narrowband is more annoying than installing gilbert godfried and carrot top in the rear hatch area.

 

That's the point of a narrow band... unlike a wideband o2 that will actually tell you what your AFR is, a narrow only knows three conditions: Lean, Stoich, Rich. . So tuning with one becomes less of a science and more of a "Hey, it's lean here, I'm going to richen it up by a random amount until it reads rich."

Also, along with rewiring the fuel pump to make sure it's getting a good, solid 12+V constantly. I would get your injectors cleaned if they haven't ever been cleaned before. I just got mine back from http://www.cruzinperformance.com/ , This is the second set I've sent there, and I'm still really happy with the service and price.

Good luck