Fuel and timing
Fuel and timing
Here in the UK I run BP Ultimate, it's readily available if a little dearer than standard fuel but I believe it does keep the engine cleaner.
It is classified as 98RON 88MON
The stoichiometric for this fuel is 14.4 as opposed to 14.7 for regular unleaded or ethanol blends.
It developes maximum power at an AFR of 12 as opposed to 12.5 for those mentioned above.
Based on these figures I should theoretically be able to advance the timing across the map by 5 degrees.
If I have read the TTS instructions correctly it is suggested that once the VE's are squared away I can increase the timing by 2 degrees across the board, reduce the knock retard table values to 0, and do a data run to see if knock is present.
My options would then be to either add fuel or reduce timing in the relevant cells ( I would be inclined to reduce timing)
I am a bit reluctant to disable the auto knock retard, can I not still see where knock occurs to indicate where to reduce timing.
I have done one run without disabling the knock retard tables on the original timing settings ( 2013 Slim, calibration file DAB358-01-AD ) and got a max knock retard of 3.5 at 100 % throttle 3000 to 4000 RPM and 102.2 MAP, basically wot and accelerating. The events are isolated to where I deliberately attempted to ride in a manner that would induce knock. In my world it's only likely to occur riding two up and claiming a fairly steep hill.
So my experiment appears to still allow me to reduce timing over very few cells, that I have identified without disabling knock retard.
Am I missing something?
I must also confess that the timing tables have me a little confused as the instructions indicate that timing be reduced, which in my mind means that the figures in the appropriate cells need to be increased (increment) so that the spark occurs nearer TDC.
Do I have this correct.
It is classified as 98RON 88MON
The stoichiometric for this fuel is 14.4 as opposed to 14.7 for regular unleaded or ethanol blends.
It developes maximum power at an AFR of 12 as opposed to 12.5 for those mentioned above.
Based on these figures I should theoretically be able to advance the timing across the map by 5 degrees.
If I have read the TTS instructions correctly it is suggested that once the VE's are squared away I can increase the timing by 2 degrees across the board, reduce the knock retard table values to 0, and do a data run to see if knock is present.
My options would then be to either add fuel or reduce timing in the relevant cells ( I would be inclined to reduce timing)
I am a bit reluctant to disable the auto knock retard, can I not still see where knock occurs to indicate where to reduce timing.
I have done one run without disabling the knock retard tables on the original timing settings ( 2013 Slim, calibration file DAB358-01-AD ) and got a max knock retard of 3.5 at 100 % throttle 3000 to 4000 RPM and 102.2 MAP, basically wot and accelerating. The events are isolated to where I deliberately attempted to ride in a manner that would induce knock. In my world it's only likely to occur riding two up and claiming a fairly steep hill.
So my experiment appears to still allow me to reduce timing over very few cells, that I have identified without disabling knock retard.
Am I missing something?
I must also confess that the timing tables have me a little confused as the instructions indicate that timing be reduced, which in my mind means that the figures in the appropriate cells need to be increased (increment) so that the spark occurs nearer TDC.
Do I have this correct.
Last edited by WildBill2566; Aug 28, 2013 at 05:29 PM.
Stellar HDF Member
Joined: Sep 2007
Posts: 2,467
Likes: 677
From: Vancouver Island B.C.
I thnk you need to leave the knock retard turned on, but zero out the adaptive knock retard table until you are done. There are areas in the timing tables where you can add timing and not see knock retard but will be past MBT. A good indicator is vibration.
I'm just removing the learned part of the knock, which should highlight areas of knock previously hidden.
Thank you.
Ok well I advanced the timing below MAP 80 Kpa by 4.5 degrees, and still no sign of knock.
Engine temp seems to be down about 5 to 10 degrees, but I need to gather more data to be sure.
I intend to continue to advance the timing until I develope knock, then I will retard the timing back 3 degrees as advised.
I'm surprised by how far the timing is off, must have been set up for some pretty poor fuel.
Engine temp seems to be down about 5 to 10 degrees, but I need to gather more data to be sure.
I intend to continue to advance the timing until I develope knock, then I will retard the timing back 3 degrees as advised.
I'm surprised by how far the timing is off, must have been set up for some pretty poor fuel.
Outstanding HDF Member
Joined: May 2008
Posts: 2,543
Likes: 19
From: Ashland Ohio
Watch what Lonewolf says. Once you pass MBT, then it becomes TOO much timing. What you may wish to consider is doing what you are doing and advance the whole table until you get ping. Fix the ping then retard the whole table by 3*. Do not start moving single cells until ping, just the whole table.
For the most part... TTS timing tables are decent. It will be fuel and weather that will alter the needs of the engine. It's NOT crap gas that's making the difference for you..(maybe a little). it's that you are NOT in Texas with high temps and no humidity. Base cals are a starting point... not the end up point. A base cal needs to work everywhere and under most conditions. If you moved the whole table 4.5*... with no ping... I'd call it a day.
For the most part... TTS timing tables are decent. It will be fuel and weather that will alter the needs of the engine. It's NOT crap gas that's making the difference for you..(maybe a little). it's that you are NOT in Texas with high temps and no humidity. Base cals are a starting point... not the end up point. A base cal needs to work everywhere and under most conditions. If you moved the whole table 4.5*... with no ping... I'd call it a day.
Last edited by wurk_truk; Aug 29, 2013 at 04:00 PM.
wurk_truk
Thank you for your advice, I shall follow it.
I have only altered the tables upto and including MAP 70, as the manual states "only alter the table below MAP 80."
I had intended to find the ceiling then back off the altered parts of the tables by 3 degrees.
Thank you for your advice, I shall follow it.
I have only altered the tables upto and including MAP 70, as the manual states "only alter the table below MAP 80."
I had intended to find the ceiling then back off the altered parts of the tables by 3 degrees.
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