# need rough starting fuel values

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Hi,

Have a hilborn injected 434 ChevÂ in a canamÂ replica race car project controlled by G4 extreme running sequential.Â  Engine has been dyno'd in the US - I know how much fuel it needs at WOT in each RPM incrementÂ for best power.Â  I have it running well and have tuned idle and no load.Â  Â To get me in the ball park at WOT before I start testing can you pse supply fuel table values that will give approx the following injector duty cycles with a master fuel of 13:Â  16.8, 23.1, 29.9, 37.1, 47.2, 56.9, 64.7, 69.6, 72.2, 73.3.Â  Not after any of your proprietory maths! - I would really appreciate your help.Â  Email me offline at [email protected] if you prefer.

Cheers, Andrew Robertson, Wellington

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Hi Andrew

I make no promises on this information.

The equation you are looking for is

Fuel % = [ Inj Duty * 1200 / rpm + (corrections in ms, like battery voltage, etc)] / Master fuel * 100 + (corrections in %, warmup, IAT, etc)

Assumption is the Inj Duty DOESN'T take into account corrections, otherwise enter zero for corrections.

Hope to see you at Hampton Down soon.

Cheers

Andy

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Hi Andrew

Swap '/ Master fuel * 100' around so it is '*100 / Master fuel' or use NO brackets ().

With 13ms Master, 6000rpm, Inj duty 75%, you get injector time of 15ms and fuel of 115%.

If these are real numbers you will need to increase the Master Fuel value. Try Master at 18ms giving 83.3% fuel.

The duty doesn't change just fuel table %.

Any questions let me know.

Cheers

Andy

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Hi Andrew,

You have not mentioned at what RPM each of those duty cycle numbers are. If you can provide the RPM details I can help you with the fuel table numbers. Also are you running your load axis as TPS or MAP?

Cheers,

Scott

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Hi Andrew,

All of those injector DC numbers are not possible to achieve with a 13ms master fuel number, 100 kPa MAP reading and the RPM specified. I have included what the fuel table numbers would be if you were running an 18ms master.

RPMInjector DC %Fuel Table Number
2000 16.8 73.8, 53.0 with 18ms master
2500 23.1 81.5, 58.9 with 18ms master
3000 29.9 86.9, 63.5 with 18ms master
3500 37.1 94.0, 67.9 with 18ms master
4000 47.2 Not possible (Max Inj DC reached 44.6%), 92.8 with 18ms master
4500 56.9 Not possible (Max Inj DC reached 50.7%), 81.4 with 18ms master
5000 64.7 Not possible (Max Inj DC reached 56.4%), 83.0 with 18ms master
5500 69.6 Not possible (Max Inj DC reached 62.1%), 81.0 with 18ms master
6000 72.2 Not possible (Max Inj DC reached 67.5%), 77.6 with 18ms master
6500 73.3 99.7, 72.0 with 18ms master

Cheers,

Scott

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Hi Andrew,

Yes, adjusting idle as above should give you a good starting point. I would recommend having it tuned professionally or using a wideband O2 sensor when tuning to get it correct.

Good spotting with the 4000 RPM value, yes, 75.9 in the fuel table is what it should be.

Cheers,

Scott

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