Target afr

[Toyota John]

I have also heard that there are two theories for tuning this platform: leaner with less ignition and richer with more ignition. I have herd both sides form experienced tuners. I am not sure which is better but I do plan to test both. One thing i know is that DI brings new changes to the way we tune. I have a well revered tuner friend in the Subaru world who is running 12.5 on his modified 15 WRX with the turbo fa20 DI version. Normal PI turbo engines would have problems with this but he is having good results with leaner AFR. This was on a stock motor too.

[burdickjp]

Originally Posted by Kodename47

No it's not. Running richer keeps things cooler, which has it's own purpose. I'm not sure how you equate running hotter is healthier?? Less fuel AND less ignition advance = hot EGTs, which over a length of time isn't likely to be good for valves or exhaust components.

It might be worth noting that the OEM tunes this car richer than you suggest, would you consider that unhealthy?

I haven't seen anything richer than 0.85 lambda, and suspect this to be a dubious claim, as DI engines run quite a bit leaner under load than port injection engines.

Hotter in this context isn't hotter enough to be bad for valves or exhaust components. We're still talking being in MBT AFRs here.

[Kodename47]

Originally Posted by bur****jp

I haven't seen anything richer than 0.85 lambda, and suspect this to be a dubious claim, as DI engines run quite a bit leaner under load than port injection engines.

Hotter in this context isn't hotter enough to be bad for valves or exhaust components. We're still talking being in MBT AFRs here.

Stock GT86:


That's really no richer than 0.85.....

By it's very nature, running leaner is hotter. Whether that is safe or not, your choice. Safe by it's very nature is a personal opinion, you may only want it to be safe for 10k, others for 50k. Just because an AFR is "ideal" for making power does not mean that it's the best and safest AFR. Adding fuel aids in cooling and adds a safety net, I doubt there's many tuners running any form of boost that maintain mid 12s

I certainly wouldn't want to be at 12.5:1 at max RPM consistently, but you would. Who's right.... perhaps neither of us.

[steve99]

I cannot comment on boosted but all the NA tunes i have seen for these cars target low12 at leanest and most dipping into 11 at max rpm for knock resistance on our 98 ron fuels which are far inferior to usa 93 fuels and often not even as good as 91 usa.

If i go any leaner you have to remove wads of advance and loose power

Quality an composition of you fuel is going to make a difference.

On E85 can run around mid 12 afr (adjusted to petrol afr scale) at high rpm.and about 10 degrees more anvance than 98 ron

[Kodename47]

Here's a few basic AFR references, note that NONE say that 12.5:1 or leaner is ideal and richer is unsafe:



http://www.turbobygarrett.com/turbob...g_rich_vs_lean
http://www.endtuning.com/afr.html
http://www.autospeed.com/cms/article.html?&A=1595 (Note point 3)
http://tunertools.com/articles/AFR-Tuning.asp

Lets not forget, where are you measuring AFRs? Are you taking into account valve overlap?

[aagun]

first ::: FA20A is coolest and best fuel mixed engine i saw it on my life
[ame="https://www.youtube.com/watch?v=zc8aUxBZlsU"]2013 Scion FR-S | D-4S Technology Explained - YouTube[/ame]

2nd ::: AFR should works with engine timing advance
3rd ::: rich AFR with increase(add + to timing )ETA means low power , heat up and bad fuel Eco*
4th ::: lean AFR with decrease (add - to timing ) ETA means boom , poping knocking and then engine died
5th ::: boosting it throws more HP
6th ::: MY OWN boosting Table AFR target and ETA target.

[burdickjp]

I haven't seen a stock open loop AFR target table for a toyobaru richer than 0.9 lambda. Most of it stays around stoich. I've also not seen an NA tune for these any lower. Look at the OFT tunes for good examples.

If you're losing power you're out of your MBT plateau, and doing it wrong.

The big point here isn't the hard numbers, it's the concept of MBT as it pertains to AFR. If you want to lower EGTs (which isn't much of a concern with an NA application), richen it up until it starts to lose power and then bring it back some. Add timing until you don't make any more power, bring it back some. Do a happy dance. Go enjoy it.

[burdickjp]

Originally Posted by aagun

3rd ::: rich AFR with increase(add + to timing )ETA means low power , heat up and bad fuel Eco*
4th ::: lean AFR with decrease (add - to timing ) ETA means boom , poping knocking and then engine died

Conversationally, increasing timing means advancing it, decreasing timing means retarding it.
So we're discussing leaning fueling and retarding timing versus enriching fueling and advancing timing. Is that any clearer?