y do i hav fluctuations of Air fuel ratio at 5.5k rev constantly

[gti[GSR]]

when dis happens my rev feels like a pull back, drop of performance for 1 sec,,,, on dyno machine at each run, it always happens at dat region, thus im not able to pull above dat region, as da a/f ratio fluctuates up n down at 12 n 13 region... not consistent at all.

i've checked my plugs iridium 6, replaced my coil packs still same 2 no avail. my fuel reg still workin jus dat da meter on it not accurate anymore.

any opinions??? could it b my tuning? could it othe things? shud i retune it ? any ideas??? besides all dis???? anyone experienced it b4? oh yea, im runnin on a rb20det.

 

[Dr.D]

cuz u bought the gtr bumper..hehehhe.. cursed by me..hehehh

 

[gti[GSR]]

trust u to come up wif dat...!!! HAhahahahah

help me ask around la,,,, da drop for 1 sec, i hate it,,,, cant rev properly once reach 5.5k

 

[Dr.D]

my friend ( name totally secretive) dyno his 4 door 370 bhp GTT..heheh..also had similiar problem, a dip during dyno also around that area of rpm. tuner said to get a boost controller to stabilize boost.. ask zephurus regarding this .. hehehe

 

[gti[GSR]]

hmmm im using wastegate to control my boost onli wor...!!! u sure or not??? where's zephurus??? wellz, i assumed u named as unknown den list zephurus in,,, its most likely its him AHHAhAhAhAHhA... but also my boost is constant at 0.9 wor... can read da boost reading on dyno machine ma... if boost creep, den it'll displayed at da comp rite???

also ur friend zephurus, did he manage to overcome dis prob???

 

[chris7880]

change ur ecu and boost up 1.5 bar den u dun have to problem dy....heheh

 

[khoyos]

if the problem occured on the dyno, surely ur tuner would have said something, or gave some comment on the problem?

if problem occured on the road, then there would be a million possibilities. if it is on a dyno, surely ur tuner could be able to pinpoint the problem... if ur tuner could not solve the problem, we all forummers could only gape our mouth, as most of us here are merely end users instead of people who could give professional advice...

 

[gti[GSR]]

i did at under 5, he said either my coil packs n my plugs, i jus replaced both, but havent tried.... i replaced to iriway plugs 7....

 

[kaminari]

RB series commonly facing ths problem, if u talking abt normal STD myb u should check those items :

1. Spark plugs
2. Coil packs (mostly coil pack problem is so obvious.Ex: Running 5 cylinder)
3. AFM (really most common for RB when too hot whether/engine bay)
4. Fuel filter (dirty fuel filter also drop the engine power)
5. Lastly, most unaware item is O2 sensor. Dirty n old O2 sensor will cause
engine Air / Fuel Ratio unstable. I change mine to new,totally different feeling
especially 4500rpm above.More smooth n torque!

My 2 cent advise :hmmmm:..... try tht

 

[gti[GSR]]

1) coil packs - replaced
2) spark plugs - re placed
3) AFM - checked previously when tuned, as fluctuations cost my car to die, no probs wif it
4) fuel filter - havent checked
5) o2 sensor, last option, den will check it.

thanks bro.... kaminari, hows ur r33, sold liao????

 

[zephuros]

Waaaa! 370bhp 4 door ar? Awesome.... Mine is about there... errr.. minus 100! hehehe... Anyway stop wasting your time chasing the problem with all those items. None of them will cure your problem except perhaps a F Con or Power FC. The solution is simple..... o spend RM300 on a FCD and you're sorted.... TRUST MEEEE!!!!! :D

Also, you're already at the flow limit of your MAF Sensor. With that kinda power your MAF is already metering close to 5.0V which means it's maxxed out! Mine showed 5.09! Sucks!

Also, if you note at the region where your power suddenly drops, your A/F goes super rich. This is the ECU trying to save your engine from catastrophic failure. Problem with the ER34 is that the ECU has way way way too many protection methods just to ensure that your engine doesn't suddenly run lean and go kaboom!

I would invest in a Z32 AFM and an aftermarket ECU or even just a piggyback. a Z32 AFM and a S-AFC will work just as well. Easy to set up too....

 

[gti[GSR]]

haAHAHHAh but i am using f con S HAAHhAhAhA... no la, i dun hav so much hp la... onli 211hp @ 5.5k, as its running lean... not rich ler... as for AFM, its still under utilised ey...!!! not evne maxing out... injectors are bigger 2...

so im chasing after da issues... coz i cant rev pass 5.5k, of coz hav to settle dis ma...!!!

 

[zephuros]

That's weird, i'm totally out of MAF voltage resolution already. I'd check this again if i were you. AND, since you already have bigger injectors then it could just be due to poor tuning... the part throttle tuning is more important that fueling and timing at WOT. Any monkey can tune at WOT!

 

[tuned]

sorry to intrude...not a skyline owner, but used to face the same problem with my previous twin turbo.....

ur lean reading is possibly when you full throttle ur ride at almost max boost and upon touching 5.5k rpm and ur car starts to jerk and power loss....

zephuros's right about the FCD....as ur factory ECU would probably have some safety fuel cut....

another possible culprit besides all those mentioned...could be a faulty cam sensor... have u check that?

 

[zephuros]

faulty cam sensor will usually manifest itself in a CEL warning or there will be a sudden and instantaneous drop in RPM from idle to 0 occasionally. Have experienced this before too... :)

 

[gti[GSR]]

sudden drop? hmmm mine at idle, sometimes it'll react strangely like i step in da accel da throttle kinda feels weird jerky feeling like 1k rpm feels sangkut, unless rev more n go past 2nd gear. dis happens onli on first.

but mr zephurus, how u check if i max'd out my afm? if i did max out, hjow come last time wif safc, dis didnt happen b4, n it happens onli now? yea part throttle aslo an issue...

dis issue lies when i rev pass above 4k, n i release my throttle, there's heaps of misfiring....

i got so much issues, i dunno how to solve any of dem. im lost...!!!!

zephurus, help me check my maf AHAHhahahah

tuned bro, ermmmm nah i also havent check my cam sensors hAhaha how to check if its faulty?

 

[tuned]

well the cam sensor, am sure your mech would know how to check..

 

[gti[GSR]]

erm,,, its hard to find reliable mechs lately HAAHhAhA unless u hav ppl who are realli gud in RB engine, pls let me noe... esp in KL area.... SUNWAY 2 far for me HAhAhAhAh....

i jus looked at my dyno sheet, dere is a dip in hp...
my a/f jumped from 12.2 to 12.6 back down 12.2 den up to 12.4 den fluctuate lagi... in dis region hp decrease from 211 to 200....

 

[kaminari]

Thanks bro.... kaminari, hows ur r33, sold liao????

Still looking for serious CASH buyer~hahaha....

After looking back ur post, i realize tht ur boosting 0.9bar!!n running on FconS.... Try lowering ur boost to 0.7-0.8 bar bro. STD ecu have boost cut at 0.9 bar...nt to mention FCD all.Last nt least, refine ur FconS tuning!
U can try unplug it 1st see hw the result....sometimes untidy wiring messing the car.

 

[gti[GSR]]

oh serious? damn maybe its my boost cut hmmm but i'd forgotten whether i installed my boost cut thingy or not... i thin i did. i cant remember. maybe it is ey,,, HAhahahA... nvm i'd beetter check.... wellz my f con s wiring is stuffed, super messy la....