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Varying Afr's On Dyno

jarrod83

By jarrod83,
in Engines & Forced Induction

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jarrod83 Community Regular

jarrod83

Posted
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Hey guys i recently stuck my car in to get tuned, they reached about 9 psi and started to have issues with knockin.. etc scratched their heads for a while and worked out that the air fuel ratio was changing dramatically between runs without them changing any settings.. between high 10:1's to low 12:1's on boost

my mods are intank walbro fuel pump, power fc, fmic, full exhaust n a blitz ebc.. ive tried earthing the fuel pumps earth to the battery and the results remained much the same

any ideas would be greatly appreciated

Cheers

Jarrod

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jarrod83 Community Regular

jarrod83

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yeh i would of liked them to have done this but i wasnt there as i was at work, had a mate take it up.. the ppl that dynod it turned out to be completely useless coz they could of chekd the coilpaks n pressures while it was on a dyno, n i don't want to have to send it to another place n another dyno just to get the problem resolved, just would like to know some of the most likely causes.. the earth wire on the in tank fuel pump is exposed n a little corroded.. that couldnt be causing the issue could it?!!

jarrod83 Community Regular

jarrod83

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located in perth guilt-toy, thanks for the pointers guys ill probally replace the fpr first and over the fuel pump becuz its the cheaper one to replace... are they any fpr's that are direct replacement that dont need adjusting? is the sard one any good?

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
located in perth guilt-toy, thanks for the pointers guys ill probally replace the fpr first and over the fuel pump becuz its the cheaper one to replace... are they any fpr's that are direct replacement that dont need adjusting? is the sard one any good?

It goes in this order

Test

If broken

Replace

Dont just go replacing random parts dude, test them, find the problem and then fix it the first time rather than bringing more problems into the equation

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

you said it was doing it under load, you must therefore test it in the same fashion

You 'can' do it on the street, but you wont be able to see the AFR's without a wideband and a proper read out.

Take it back to the dyno place and demand they do a semi-reasonable job. They did a half assed one last time

jarrod83 Community Regular

jarrod83

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  • Author
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yeh i got a wideband with a datalogit.. i rang up the shop this morning n askd why they didnt test the fuel pressure n they claimed coz they were borrowin the dyno they didnt have their tools with them to do it ... so now i have the dilemma of sendin it to another shop with a dyno to diagnose.. why im tryin to just fix it myself coz all the shops in perth seem to be useless..

jarrod83 Community Regular

jarrod83

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  • Author
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anyone know if a 180sx fuel pump will work in a r33 gts-t?!? i borrowed a girl my stock one because she thought her one was broken n claimed several ppl said it was the fuel pump so after we installed the fuel pump for her we found out she had a kink in her fuel line, when and got home, i tested her fuel pump n it still worked.. id swap them back sooner but shes in bali for a while .. so would it be fine to test a 180sx one in the skyline for a run to see if the afr's hold more steady on the wideband

jarrod83 Community Regular

jarrod83

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  • Author
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ahh think i might just buy the new fuel pump.. standard wiring isnt the best anyway the earth wire is exposed and a little corroded so ill buy a full replacement one... so tomei or nismo?!! i know you probally can't go wrong with either but what one would allow for more hp?

Cheers for all the advice aswell guys

  • 2 weeks later...
jarrod83 Community Regular

jarrod83

Posted
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Posted (edited)

hey guys sorry to bring up an old thread but im still having afr troubles, i bought a new tomei fuel pump to replace the walbro, no change still playing up... bought a sard adjustable fuel pressure regulator.. same results...varies between 12 n 14.4 around the 6psi mark... and varies between 9.5 and 12.2 around the 10 psi mark... im measuring the results with a innovative motorsports lc-1 hooked upto a lap top... has anyone else got any other ideas that could cause the results to vary so much

Cheers

Jarrod

Edited by jarrod83

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