Full throttle AFR leans out after a few pulls, HELP!!!

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby wendy-lad » Wed Feb 24, 2021 7:17 am

Hey guys,

Thanks for the responses!

Kojab - I'm just using the plastic gauze filter the Raceworks fuel pump came with, so shouldn't be restricted there. I've swapped the pump a couple of times too and the filter that I've pulled out each time has never crushed in on itself.

Chuff - I thought there might be something in the background still changing the VE somehow, but then it's changing the AFR way too much to be just some little background calculation in effect...?

Quip4it - That's something I haven't thought of actually... I upgraded with new wiring to the fuel pump hanger, but the actual hanger bulkhead would be a limiting factor if factory Holdens just run the GM 14amp bulkhead like talked about in that link. I'm at 43psi base and 14 psi boost, so I'm basically nearly touching 14amp under full load according to the Raceworks 340LPH flow chart... That'd be enough to make it heat up a bit and crap out, then cause a voltage loss to the pump yeah?

Might be a bit hard to test what's being drawn between the fuel pump and hanger bulkhead under load though, so does anyone know what amps the factory hanger can handle?

Thanks!

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby wendy-lad » Wed Feb 24, 2021 7:29 am

Hey Dylan,

The coolant and intake temps don't really change much between the time it's running fine and the time it starts running lean.

I can be driving and give it a 3rd-4th pull and it shows low 11's AFR, then coast for a minute or so and give it another big pull, then as it comes onto boost it'll show and hold mid 12's AFR for a second or two before I jump off the throttle cause it's about to blow up.

Thanks

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby 'quipt4it » Wed Feb 24, 2021 7:40 am

I thought you meant 340 lph when you mentioned Raceworks lol.
That would mean 57 PSI and 800+ hp (instead of the aforementioned 55 PSI).
Check your reg. is supplying at least this under those hot/ load conditions.

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby wendy-lad » Wed Feb 24, 2021 7:58 am

Hey Quip4it,

Yeah it's a Raceworks 340LPH, not a 320, not sure how I fudged that...

I've swapped the fuel pressure regulator out already and that didn't change anything, cause I didn't think they're something that could really go wrong from a bit of heat, they just sort of work properly or they don't at all, regardless of engine temp.

But yeah I could put a flow gauge before and after the reg to rule that out.

I think you're on the money though with the fuel hanger bulkhead being the weak point of the whole fuel system now.

Thanks

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby antus » Wed Feb 24, 2021 12:33 pm

I'd also suggest logging the tune. You'll see straight away if the injector rate in milliseconds is less when the AFR is less. If it is, then your looking at a sensor or the tune itsself, and the question is why is the computer wanting less fuel. if the injector milliseconds stay the same but he AFRs are noticeably leaner then your looking at the fuel hardware.
Have you read the FAQ? For lots of information and links to significant threads see here: viewtopic.php?f=7&t=1396

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby wendy-lad » Wed Feb 24, 2021 1:26 pm

Hey Antus,

I think I've attached a Word document with 2 screenshots from logs taken when running fine vs running lean.

weird afr changing 2.rtf
(526.08 KiB) Downloaded 5 times


These were with exactly the same tune...

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby Charlescrown » Wed Feb 24, 2021 2:46 pm

I did leave a reply but must have clicked the wrong button.
I'd fit a pressure gauge and take it for a run and look for any drop in pressure when the problem occurs. I recently had a VL where the pulsation damper started causing a blockage from the pump till it got to the point where it totally blocked the fuel supply. Removing the damper fixed the problem. My thoughts on a blocked pump pickup screen is the pump gets louder as the supply drops so do you hear any change in pump noise?

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby immortality » Wed Feb 24, 2021 3:13 pm

Best bet is to log fuel pressure, measuring static flow is only indicative that the pump has the potential to move X amount of fuel, what happens in real life when shit is hot and the car is moving is normally totally different.

Something like this https://www.amazon.com.au/Pressure-Tran ... B00NIK9E10

Assuming you're using the 424 PCM with 11/12p?

Some of those cheap fuel pressure regs are also susceptible to varying fuel pressures depending on varying conditions, put something decent on it but start will logging the fuel pressure.

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby antus » Wed Feb 24, 2021 3:33 pm

Nothing jumps out at me from those screen shots. The lean view is showing 1ms less injector time, but being just two screen shots it doesnt tell the whole story. You'd be better to save the log and post the XDL file. I can see from the screenshot that your running 12p and its 2 bar petrol XDF but in general its good to post that information with the logs.
I'd be using the monitor view and overlaying target afr and wideband afr in the same monitor and making sure the scale of the two items in the same so you can see how far one is from the other. Then if everything is working well you can use it to adjust your VE table, or if the hardware is not working well you'd see wideband afr tracks the target AFR in one pull, the whole way down the pull, and not in the next. I think it might be a hardware/heat problem though like the others are saying.
Have you read the FAQ? For lots of information and links to significant threads see here: viewtopic.php?f=7&t=1396

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Re: Full throttle AFR leans out after a few pulls, HELP!!!

Postby delcowizzid » Wed Feb 24, 2021 5:15 pm

Post up some logs and bin I'll have a look
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem

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