air fuel adjustments

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  • #1

    air fuel adjustments

    so im wrapping up my NA2T build and im having some trouble with my A/F ratios. first start after cooling down is tough. i have to hold the key and fish for it to start. acts like not enough fuel. after its been driven and you start it its fine. i also experience it cutting out some at full throttle. seems like not enough fuel. usually happens between 5k and 6.5+k rpm. then when i get finished driving im hearing ping as if left over fuel in cylinders. i know timing will play a big factor in this. I understand that the maf, tps, chts, O2, aacv, & ficv all have an effect on Air/fuel. im wanting to see where i need to set everything as a baseline and then what to adjust. all i can adjust really is maf, tps, ficv, timing.


    Im using:

    86t ecu
    matching injectors/O2
    upgraded t3 intake w/ stock compressor
    crap boost controller
    boost guage reads 10-15lbs (15 max at 6500rpm)
    yellow sticker maf that has been "adjusted"
    timing set to 20* advance (3rd to last mark)
    new pluks NGK BCPR7ES-11 I melted 2 of the 6 series at .35ish gap so thought id try colder plug also stock gap at .44ish
    new dizzy cap
    new dizzy rotor
    new oem ignition coil
    PRW-2

    let me know what other info you might need to help me with this

    thanks
  • #2
    pinging is lack of fuel…its detonation. 15psi is too much boost. You're melting plugs because you're detonating…you're also melting the top of your pistons.

    MAFs that have been tampered with always cause the car to run like shit, too, in my experience. Replace it with a sealed MAF that has never been tampered with. Also, turn the boost down - replace it with a ball and spring boost controller so you have consistent boost control, and run 12-13psi tops being you're on stock fuel. Watch all of your issues go away.

    Also. AACV and FICV have nothing to do with fuel, neither does the TPS (idle switch. Only fuel it affects is cutting fuel on coasting and makes it slightly leaner when idling)

    Lastly…get a wideband. You shouldn't be attempting to push the stock fuel system to its limits as you are unless you have one. Right now, you're simply speculating. You don't actually know what your air-fuel mixture is…but I can tell you for sure, its lean. Are you even intercooler? If not you shouldn't be running over ~8psi if you're 9:1 CR, and no more than ~9-10 with stock turbo internals.
    - VG30DET (HE341) 86 300ZX - 1982 280ZX Turbo - Headered NA 1986 300ZX 2+2 - 2000 Xterra -
  • #3
    im using N/A block and internals. no FMIC as of yet i do plan on it just not money right now. same for the new boost controller and wideband. ive been sitting on all this stuff for a good while and im just now getting to drive it. i know my set up isnt ideal by any means but its hell of a lot better than it was.

    ill try the extra maf i have see if it helps. is there a way to reset them after being tampered?
  • #4
    If you're not intercooled, do *NOT* run over stock boost on a 9:1 block.
    - VG30DET (HE341) 86 300ZX - 1982 280ZX Turbo - Headered NA 1986 300ZX 2+2 - 2000 Xterra -
  • #5
    Jesus Christos, you melted plugs? Retard timing and increase fuel pressure if you can until you get a wideband. I'd be surprised if the pistons weren't toasted now.
    BLOZ UP.com
    It is not recommended to confirm proper installation by driving into walls or other barriers as this could cause personal injury or damage to the vehicle.
  • #6
    Hard to start after engine is hot is likely due to vapor lock in the fuel rails/lines. Kind of common, even my 86T does it from time to time.

    Stock turbo injectors are most likely near maxed out if melting things. Get an adjustable FPR and raise pressure up about 5psi or so for a band-aid fix. But you really need to step up the injector sizing, and get a fuel pump.

    What do you have ignition timing set at? 20*ish? If so, lower it to about 15-18* and see if that helps with pinging some.

    1986 300ZX Turbo…sold
    1990 Skyline GT-R…new money pit
    2014 Juke Nismo RS 6-speed…daily
  • #7
    Originally posted by NissanEgg
    Hard to start after engine is hot is likely due to vapor lock in the fuel rails/lines. Kind of common, even my 86T does it from time to time.

    Stock turbo injectors are most likely near maxed out if melting things. Get an adjustable FPR and raise pressure up about 5psi or so for a band-aid fix. But you really need to step up the injector sizing, and get a fuel pump.

    What do you have ignition timing set at? 20*ish? If so, lower it to about 15-18* and see if that helps with pinging some.

    im getting hard to start when cold.

    timing is set to 20*ish with light not digital. ill try 15*ish.

    unfortunately this morning its had a strange tick/knock. i was going to take it to school to put on a lift but i didnt like the noise. got home and its a bit louder. its not a consistent sound im going to pull plugs and valve covers maybe even heads after a compression test. oil dip stick reads good but i feel like it could be wrong. i have oil pan gasket leak from over torqued bolts and it looks like its losing oil yet dipstick never reads low. im gonna drain the oil see how much comes out needs changed anyway.

    just frustrated yesterday was first time i got to drive it and it feel that good. it was pulling great, shifting better, breathing better no noises. only issue was lack of fuel at high rpm. just lucky its not my daily.
  • #8
    You shouldn't be hitting anything over 10 psi unless you are using racing gas or intercooler. Turn thy boost down, because you probably already killed your engine.
    http://z31performance.com/showthread…2-2-(-now-NA2T
    My build thread (:
  • #9
    Engines toast.
    - VG30DET (HE341) 86 300ZX - 1982 280ZX Turbo - Headered NA 1986 300ZX 2+2 - 2000 Xterra -
  • #10
    truth hurts but thats what i get trying to be cheap and rushing thanks guys ill let ya know what i find
  • #11
    D'oh shit.

    Originally posted by michaelp
    Are you even intercooler? If not you shouldn't be running over ~8psi if you're 9:1 CR, and no more than ~9-10 with stock turbo internals.
    I want to learn something here…NA internals create for higher compression, right? Is that why you want to run lower boost? (as the compression is already higher than a turbo motor, therefore, needs less boost?)

    Thanks.
  • #12
    i would think partly bc theres more pressure and also the ic would cool the hot air that would weaken internals? asumption obviously i dont know enough lol. really never can know too much.
  • #13
    I'll send you a $1 with pp if you up the boost and destroy the rest of the engine, recording it all on video. With your phone sideways though, none of this vertical video crap.
    BLOZ UP.com
    It is not recommended to confirm proper installation by driving into walls or other barriers as this could cause personal injury or damage to the vehicle.
  • #14
    Originally posted by BLOZ UP
    I'll send you a $1 with pp if you up the boost and destroy the rest of the engine, recording it all on video. With your phone sideways though, none of this vertical video crap.
    This! Lol
    http://z31performance.com/showthread…2-2-(-now-NA2T
    My build thread (:
  • #15
    Originally posted by BLOZ UP
    I'll send you a $1 with pp if you up the boost and destroy the rest of the engine, recording it all on video. With your phone sideways though, none of this vertical video crap.
    I will throw in $10 on this if you get it on film with a go pro.
    Build Log Link: http://z31performance.com/showthread…-VG33-HX35-WIP
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