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Thread: Optimal Fuel:Air ratio for NA L61

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    Optimal Fuel:Air ratio for NA L61

    Disclaimer: Sorry if this has been discussed before, I could not find anything in a search.

    Does anyone know what the ideal AFR is for a NA L61 under race conditions?
    Race conditions for my car is running mostly WOT between 4000-6100 rpm on a road course for extended periods, up to 24 hours with pit stops every 2-3 hours.

    I found this http://www.ecotecpower.com/forums/re...=4&i=855&t=854 and it points out that the factory AFR is 14.7:1 and this is what I was seeing on my wideband originally but I increased the VE tables and tweaked the fuel pressure to get to 13:2 on the advice of some friends who race mostly V8s.

    I definitely prefer to be a little rich for longevity of the engine but "Lean is Mean" when it comes to HP and we race endurance so fuel efficiency does come into play.

    Thoughts/Opinions/Experience?

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    Most boosted L61s like 10.5:1 to 11.5:1 AFRs. Some even like 12:1. Every car is different and we mainly use 10.5:1 as a starting point and adjust fuel and timing according to the data-logs. It is ALOT of trial and error. This is all in refence to WOT on boosted L61s, I haven't messed with building an N/A L61. Idle and cruise should be ~14.7:1.

    L61/TVS - 3.1", LS1 tb, RD Fabs header, 63#, HPT

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    Don't know much, but read that it should be as lean as you can get without knock at any point. Knock should scare the living piss out of you. The main problem that I've heard is finding the right ratio for different RPM's/loads. There is no one ratio fits all and not all engines are the same. But I'm not a tuner so take that with some salt. Boy there is an old adage.
    More humans=more problems
    Don't worry nothing will be done until it's too late, there is money to be made.
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    I am very conscience of leaning out and melting pistons, a fellow Lemons racer melted a piston in his V6 toyota engine last year, it turned out that one injector had one hole blocked, not enough to show up on the wideband or the ECU to try and correct or report but over around 8 hours racing that one cylinder was lean enough to destroy the piston.

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    Ouch, guess injector cleaner would have done nothing. Almost makes you think that having them cleaned at the end of the season is a good idea. Or the start.
    More humans=more problems
    Don't worry nothing will be done until it's too late, there is money to be made.
    Maximum profit and overpopulation will ruin all the major economies.

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    Ouch, guess injector cleaner would have done nothing. Almost makes you think that having them cleaned at the end of the season is a good idea. Or the start.
    nogo04cav Quoted Post
    Yea, I run two filters, a 100 and a 10 micron, the company I brought the injectors from offered lifetime cleaning/flow testing, I should send mine back over winter.

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    Damn that covers it well! No worries for you.
    More humans=more problems
    Don't worry nothing will be done until it's too late, there is money to be made.
    Maximum profit and overpopulation will ruin all the major economies.

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    I try and learn from other peoples failures not just my own

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    That is the best way. The rich don't have to learn anything. Us pofolk have to try and do it right the first time.
    More humans=more problems
    Don't worry nothing will be done until it's too late, there is money to be made.
    Maximum profit and overpopulation will ruin all the major economies.

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    Im finding 12:1 is really good at wot na, factory was showing 12.8:1 wot but it really likes 12:1. A bit more say 11.5:1 and it throws mad fireballs from the tail pipe but dosent seem to pick up any power. I would say try to tune 12:1 wot 13:1 at half throttel and 13.8:1 for idle in a race condition
    83 chevy s10, l61 swap,colorado trans swap, full exhaust, cai, bagged and bodydropped,kyb monotube shocks, 4 wheel disc brakes, 4 link, zq8 sway bars front and rear,poly bushing through whole chassie

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