Fuel lean out at high rpm

s300 and SManager software questions & answers
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cho-lee
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Joined: Thu Dec 01, 2016 12:05 pm

Fuel lean out at high rpm

Post by cho-lee »

Hello,

I have some problems with keeping the afr good over 7-8k rpm up to 9k.
Injector duty cycle are way too high
Trying to add fuel but it is even worse,maybe blocking the injectors full open.

B16,CSS block,57mm BW sxe257,Gsc t1 cams/valvetrain,ngk 8
522hp 511nm @ 31 psi on vp c16

The fuel setup is walbro 255 on stock wiring,stock lines,stock fuel filter,stock rail,stock fpr.
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Spunkster
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Re: Fuel lean out at high rpm

Post by Spunkster »

What injectors are you using?
cho-lee
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Re: Fuel lean out at high rpm

Post by cho-lee »

Grams 1000cc , sorry i forgot.
I will use a relay and 14v for the pump,this should help i guess and a good fuel pressure regulator with boost reference.
Anything else i should need ?
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Spunkster
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Re: Fuel lean out at high rpm

Post by Spunkster »

Is this a return fuel system?
cho-lee
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Re: Fuel lean out at high rpm

Post by cho-lee »

Sure.stock return style.
DaX
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Re: Fuel lean out at high rpm

Post by DaX »

You have a pretty high voltage offset for your wideband (> 1V) - have you confirmed the wideband readings with another wideband, like the one on a dyno? I would recommend you try correcting the wiring issue and get a lower voltage offset. You should also consider moving your wideband to D10 to get the full 0-5V signal.

You have a fuel compensation set up to add a lot of fuel (>10%) at high engine load / open loop based on ECT. My setup is different than yours, but I checked my calibration and I am not adding nearly as much fuel in this compensation as you are.

How confident are you that your dead times are correct?
cho-lee
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Joined: Thu Dec 01, 2016 12:05 pm

Re: Fuel lean out at high rpm

Post by cho-lee »

I know the voltage setup is not ok but i have installed it the way it should be,ground on the termostat housing,tried battery negative but its the same result.
D14 would not see the full voltage range like d10,but this would not be an issue.
Tried 2 different AEM wideband and it is the same voltage difference.I adjusted the voltage to read like the AEM gauge would and this is how i use it,at least until i solve this thing...

The fuel compensation should be at 0 at hot engine and tune the table.I can do that but i dont think it would make a difference.
Dead times should be correct,they are from Grams website at base fuel pressure.
TTR
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Re: Fuel lean out at high rpm

Post by TTR »

Looks to me like your out of fuel. Need all the parts that are still stock. Make a pull and have someone watch the fuel pressure. I guarantee it starts falling off. Seen it many times.
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Hondata
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Re: Fuel lean out at high rpm

Post by Hondata »

I've seen many times people use the wrong washer under the fuel banjo fitting which causes this exact behavior.
Hondata
cho-lee
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Re: Fuel lean out at high rpm

Post by cho-lee »

I have the other fuel rail type,with simple 17mm nut,not the spider washer and 22mm nut.
Meanwhile i have upgraded the fuel rail (FIC) and an6 from the outlet of the fuel filter to rail.
Aeromotive fpr should arrive on Tuesday.I will raise the base fuel pressure,modify the injector dead times and try to go to the dyno at the end of the week.
cho-lee
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Re: Fuel lean out at high rpm

Post by cho-lee »

Hi,

Went back to dyno few days ealier and made 561hp/535nm at 32psi on Q16 this time.
The fuel problem has been resolved,inj duty cycle is lower now,about 90-100 percent after 8k rpm.It needs a little bit more pressure on the regulator just to stay at max 90percent with injectors but i will fine tune this on the drag strip.

I will upload the datalog from the 32 psi run.
My rpm curve is still not very linear,it is kind of spiky.Is this normal for rpm graph ??? I see that there are the same spikes between rpm and inj duty cycle.Dyno graph looks perfect,no spikes.
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Spunkster
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Re: Fuel lean out at high rpm

Post by Spunkster »

RPM should be smooth, this does not look normal.
DaX
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Re: Fuel lean out at high rpm

Post by DaX »

What is the specific part number of the spark plugs you are using? Make sure they are a resistor type plug.
cho-lee
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Re: Fuel lean out at high rpm

Post by cho-lee »

BKR8EIX-11 and BKR9EIX-11
Same results with both.
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