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Guest
What effects fueling on an sr
I've had this on going problem for 6 moths now where the car leans out on boost
It's perfect on idle and cruise with solid 14.5:1 afr but as soon as I go WOT the afr dips for half a second to around 13:1 then goes back to 14-16:1 up to 7lbs or more till I bottle it and get off throttle
Car is running hordhams stage 3a with all supporting mods
So far I've tried another z32 maf,lambda sensor ,tps,spark plugs ,coil packs,ignitor,spare ecu and I've got some more 3a chips on order also fuel pressure is good and rises with boost pressure
Is there anything else that can effect fueling as I'm completely stuck
Thanks
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Guest
Fuel Pump hard wired? Vacuum leaks to fpr? 16:1 is stupid lean, so there's something serious amiss imo
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Guest
Yeah pump is hard wired and getting good voltage
Vac pipe is fine and it's rising and dropping with boost/vac as I had a gauge tapped into the fuel rail feed
It feels like it's not making full throttle even though it is according to the butterfly plate,test meter and data scan software
There are not det marks on the pistons so it's not knocking just goes lean and has no power but does boost
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Guest
Genuine hd 3a?
Genuine Nismo injectors?
Last edited by immy21; 03-09-2017 at 14:23.
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Guest
Also was it running fine then developed a fault?
Or fault since new parts installed?
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Guest
Genuine on both parts and it was running fine pulling hard with perfect air fuel ratios then it just started doing this
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Guest
Checked plugs for colour and any cylinder inbalance?
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Guest
All looked pretty similar to each other no signs of metal on them and the timing marks look in the same place and the tops of the pistons all look a similar colour
Should have a new set arriving at the motor factors tommorow so I can chuck them in for a clean start
Thanks for the replies
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Guest
Do you have a permanent fuel pressure gauge in the car, or have you just checked it stationary?
It does sound like the fuel pressure is dropping off under load.
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Guest
I teed into the line and tied it next to the boost gauge and drove the car around under load and fuel pressure rose 1:1 like it should
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Guest
Maybe the MAF wiring loom is faulty, try belling the wires through back to the ECU.
As you have proved you have fuel pressure under load, that means the entire fuel system is ok.
It could possibly be blocked injectors (but I doubt it), following that, then the fuel must be being pulled by the ECU either due to a fault in the ECU or a lack of air-flow signal.
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Guest
I moved the extra ground point yesterday on the maf to a better location but haven't been able to try the car yet hopefuly tonight but should have time to bell through the wiring later just need to find the ecu diagram again
Nissan data scan shows the afm voltage goes a tiny bit over 3 volts maybe 3.2 ish at full throttle and that's on a 12psi wastegate spring I hear these mafs are good for 500hp so 3.2v should be around 300hp but it's certainly not making anywhere near that currently
I've tried a spare ecu and it's the same but I don't have the new map eeproms yet so I guess they could be corrupted or something but I'd have expected corrupted chips to be dead and not have just lost the WOT line on the map
Is there any sensor bar the tps that tells the ecu to go to the full power line ?
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Guest
The SR map is "speed density" (MAF) based, the TPS primary function is acceleration enrichment so only adds fuel immediately whilst the pedal is pressed (and a few hundred milliseconds after).
It should be missing like crazy at those AFRs under load, is it not?
Are you sure it's not pulling in air upstream of the lambda sensor?
Last edited by hooky; 04-09-2017 at 18:42.
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Guest
So it seems the ecu is seeing the tps as it richens for half a second then goes lean after and there is no Miss firing or anything it does accelerate but it's slow to build any boost and slow to accelerate it's like putting your foot 3/4 down on the throttle it goes but just not hard but I've had a mate look and full peddle is fully open on the butterfly and the tps reads 4.3v
Any guesses what my ignition timing should be on wot acceleration I'm guessing it should be pretty low like sub 15btdc I've not checked what mine is doing but if it's thinking it's not after full power won't the ignition timing be quite a bit higher ?
I'm as confident as I can be there are no exhaust leaks pre lambda or pre wideband as I visually checked the joints and smoke bombed the pipe to see if any smoke was leaking from joins ect
Thank you for your help I'm sure it's something silly that I'm over looking but can't see what
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Guest
Ii thought speed density was manifold pressure based
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Guest
What injectors are you running? Jez says it's essential 555 Nismo injectors are used?
Have you had yours flow tested?
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Guest
Genuine nismo 555cc about a year old maybe a touch more and it was working for about 6 months probably more then the car started doing this and with work and doing up the house I've only been able to get the odd weekend here and there to try and fix it
I can't see it being the injectors as I'd expect it to get leaner and leaner as boost/rpm increase
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Guest
It was all fitted in Feb 16 new nismo injectors new garret gt2871r Used genuine z32 maf and plug worked perfectly since April this year
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Guest
Yep unlikely to be the parts then, sounds like you're down to good old fashioned wiring problems.
Any loom damage visible?
Do S14's damage the loom down in the wheel arch when they are lowered a fair bit?
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Guest
I'm hoping not as there the worst to find lol nothing seems any more exposed than normal really I pulled the whole injector and oil pack looms out before when I was checking stuff and seemed fine but have never really checked where it goes into the car
Yeah they chew the looms when low but I routed mine though the engine bay at the same time as fitting coilovers to save the loom to avoid badging/soldering later on
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