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Big Afr Different In One Hour

Nosure

By Nosure,
in Engines & Forced Induction

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Nosure Proficient

Nosure

Posted
Posted

the car tuned for 360kw on 1.5bar, top end of afr is 12, than the car shut down for half hour and run on the dyno again. without tune the top end of afr become 12.8. and tuner can't go any lower, because its runing out of the fuel pump. but before break is fine??

because the afr is too lean, so we drop the boost to 1.4bar on road. no idea about the afr, but tuner said it will be safe on 1.4bar. the knock is all good. no higher than 14.

anyone know the reason???

i got a nismo intank fuel pump.

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paulr33 Grand Master

paulr33

Posted
Posted

before you start the run, check MONITOR, 2 CHANNEL, AIRTEMP, WATERTEMP

check the water temp and air temp when you get normal AFR

then turn car off

and check do your dyno run an hour later

before you start the run, check MONITOR, 2 CHANNEL, AIRTEMP, WATERTEMP

compare, if they are different by a fair bit, the PFC will add in correction,

ie: it might be richening up or leaning out, based around temps you are seeing after 1 hour of not running

rob82 Mentor

rob82

Posted
Posted

I would be highly suspect on the turbosmart fuel pressure regulator - they are absolute crap.

I have had issues with three of them on two different cars I have tuned. An example was an XR6T making 750rwhp on about 25psi of boost; so 4bar base pressure and another 25psi on top of that means total fuel rail pressure of 84psi. What happen was that the rail pressure started not rising 1:1 with boost. Pull the regulator apart to find that the dodgy copper to aluminimum face they use to regualte pressure had started to etch lines across the face - hence not sealing properly. Its not even a proper ball valve. We replaced the reg with another brand new item only to find after about 10 more runs the same thing started to happen.

The other issue I had was with the click type ones on a sierra cosworth. Not sure what the issue was but when it started leaking from the vacuum source - I pulled the pin!

Kinks Grand Master

Kinks

Posted
Posted

12.8 on a rock solid tune may be fine, but if it goes from 12 to 12.8 and the tuner is out of room for adjustment then there are some serious issues that need to be addressed, especially the "out of room for adjustment" part. Who's to say whatever is at its limit has a lazy day one day and then you're at 13.5:1 or worse.

Guilt-Toy Grand Master

Guilt-Toy

Posted
Posted
Yes that is a bit lean...

Although it depends if were talking about a forged or standard engine.

Definately not safe for a standard engine making that much power...

Try a SARD reg. Top quality product.

not safe for a forged engine either

Nosure Proficient

Nosure

Posted
  • Author
Posted (edited)

I already older a sard one, hope this one is working. and i don't think the problem is the fuel pump.

because it was working fine on 1.3 bar,(AFR is about 11.5) and still some room to adjust. no point run out of the fuel pump if only add 3 or 4psi. and even stay on 1.3bar its still leaner than before.

Edited by Nosure
mad082 Grand Master

mad082

Posted
Posted

umm, if your fuel pump is maxing out, couldn't it just be getting leaner because you are pushing it so hard that it is dying? my suggestion would be to scrap the fuel pressure reg and get a new fuel pump.

you say that you don't think the fuel pump is fine, but you said in your first post that the tuner said you can't make it any richer because of the fuel pump. and in your last post you also talk about maxing the fuel pump.

you are running your pump at it's max, or very close to it and i'd guess it is slowly dying.

Nosure Proficient

Nosure

Posted
  • Author
Posted
umm, if your fuel pump is maxing out, couldn't it just be getting leaner because you are pushing it so hard that it is dying? my suggestion would be to scrap the fuel pressure reg and get a new fuel pump.

you say that you don't think the fuel pump is fine, but you said in your first post that the tuner said you can't make it any richer because of the fuel pump. and in your last post you also talk about maxing the fuel pump.

you are running your pump at it's max, or very close to it and i'd guess it is slowly dying.

yeah its possible, but the the fuel pump was ok last time on dyno,(about 2 or 3week ago) the afr still adjustable on 1.3bar. and afr is 11.5.

this time's tune is also ok before break, the afr:12, but after the break the car run on the same dyno again, the afr is go up to almost 13.

confusing.

Nosure Proficient

Nosure

Posted
  • Author
Posted
something else i just thought of, how old is your fuel filter? highly unlikely it would make a difference such a short time, but you never know.

i don't know. but my car is almost done 50000kms. and nismo fuel pump maybe done about 30000kms.

not very old.

normaly if the cat shut down half hour, the fuel pump and fuel etc`` should cooler, and afr should getting richer. but no idea why its getting leaner. i guess because the fuel pressure changed.

CEF11E Veteran

CEF11E

Posted
Posted

Some engines will run fine at 12.8. low boost engines with short blocks ie: v8's and 4 cyls with same head and block material il: both alloy.

there are a lot of cars that are tuned this lean porka cup cars are an example.

6cly engines with cast iron blocks that cool poorly in the rear 2 cyl's running high boost and agressive timing are NOT the right engines to be running such lean AFR's on, the egt's will be to high and they will be prone to detonation.

really high hp RB's should not be leaner than 12:1

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