Just one question for now?

[Manuel]

Hello everyone.

LS2 engine with E40 pcm in Australian VZ clubsport.

My question is in relation to table B3671. The original tune has 14.7 across the board to reflect the stoichiometric ratio of normal unleaded fuel,
however I am using premium shell unleaded 98 ron which supposedly has a stoichiometric of 14.35. Should this be the value that I populate in that table.

Thanks again .

[joecar]

Try it and observe the LTFT's... compare them before/after.

[Manuel]

Thanks, ill let you know.

[Manuel]

Hello Joecar.

I ended up populating the table with 14.4 for stoich, LTFT's became more negative, not sure how I am meant to interpret this.

Car feels more responsive and fuel economy has improved.

Am I on the right track by populating table B3671 with this value.

Thanks

[joecar]

14.4 might not be the right stoich AFR...

yes.

[Manuel]

Can you inform me what the correct stoich AFR is for Australian Premium 98 ron fuel.
Thanks.

[statesman]

The correct stoich AFR is 14.7 for both regular unleaded and premium unleaded.

The only difference between regular and premium unleaded is that premium unleaded has a higher RON number. The RON number is an indication of how resistant the fuel is to detonation. The higher RON number means that you can advance the spark timing more before you encounter engine knock.

There's absolutely no benefit in using premium fuel unless your spark tables are tuned for premium fuel.

[joecar]

Premium being more knock resistant allows you to run more spark advance and/or higher compression ratio.

[Manuel]

Thanks for the input fellas.

[Manuel]

Hello joecar.
I did not want to start another thread. Question is.

In near the future I am going to fit some pacemaker long tube extractors and cat back exhaust.
I know that I have to delete the two rear NB o2 sensors from the tune as there is no provision for them in the exhaust and I will only be using the NB o2 sensors fitted to each bank on the extractors.
Now when I come to tune the VE table with a wideband do I need the information from both narrow band sensors? Or can I get away with unplugging one of them, plug my wide band in its place and tune the VE table from there?

Thanks

[joecar]

Manuel,

I would do this:

tune VE using WB only (i.e. front NBO2's removed);

then install/enable the front NBO2's and see how they read and possibly fine tune VE.

( make sure MAF is disabled, i.e. MAF DTC present during VE tuning )

[Gelf VXR]

Hello everyone.

LS2 engine with E40 pcm in Australian VZ clubsport.

My question is in relation to table B3671. The original tune has 14.7 across the board to reflect the stoichiometric ratio of normal unleaded fuel,
however I am using premium shell unleaded 98 ron which supposedly has a stoichiometric of 14.35. Should this be the value that I populate in that table.

Thanks again .

I found a data sheet for BP ultimate from Australia, it also has stoich AFR 14.4, no ethanol content, during my research I also read Shell 98 had similar stoich AFR but I couldn't find a data sheet.

So you can set the PCM to the correct stoich value, don't forget if your using a wide band to set the stoich AFR to the same value. If you search efi calibrator / Greg banish he will confirm you need to set to for the stoich AFR of the fuel used.

Few fuels from the pump are 14.63 anymore, fuels these days now have at least 5% -10% ethanol lowering the stoich AFR.

The PCM can compensate with the fuel trims, but if your trying to nail down VE and MAF, I'd set the correct stoich AFR for the fuel your using.


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[Manuel]

Thanks gelf, I wonder how widely it is used.

So I am getting the extractors and exhaust fitted on Thursday.

Will the car start and run with the rear O2s not plugged in?

[Gelf VXR]

Yes I think so, but PCM will need to be updated so that the rear o2's are not reported so you don't get a warning light


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[Manuel]

Thanks.