Spark timing for optimum fuel economy

[Extinct]

Has anyone ever taken a look/tested the "optimal timing table" values versus the stock high octane tables (my ride is an '02 LS1, but I assume other gas burners have similar tables) ?

I see some very light load cells have very high timing values, about what I have read elsewhere optimal timing would be.

Anyone up for a testing session, or have the low gas prices got everyone disinterested ?

Also, while you are thinking about it, I am thinking with lean cruise these numbers might even need to go a little higher ?

[harascho]

I am also working on my spark tables. Got a '07 5.3 LMG

I will post the original and my modified tables later.

I am still running, logging and changing the values. I started with +5 additional degrees throughout the whole table. I had to reduce some, others were increased by another +2,3,4 deg

Harald

[harascho]

here is my original and the modified high octan spark table.
If you do some logs don't forget the octan scaler in addition to the KR PID.

The scaler will tell you whether the ECM is still 100% using the high octan table or not.

Harald

My table is still under construction after every testdrive I adjust some areas..

[Tre-Cool]

jesus 50+ degrees of timing!!!

yikes. you probably be better off with keeping timing to around 38~42 degrees and lean off the fuel to about 16:1.

[harascho]

...I thought timing is ok as long as there is no knock activity? And just in case the load is too big the ECM starts using the low octan table..which I left untouched..

The engine loves it and I get better mileage.

Harald

[Highlander]

The only way to really tune this is on a load dyno.

[macca_779]

The only way to really tune this is on a load dyno.

I use a technique where with the DVT control move timing around until you find the most vacuum. Obviously this doesn't work for WOT. But part throttle fuel economy tuning, it works great.

[harascho]

Nice ideas, but what if a dyno is out of reach and the only way to adjust the timing is by driving - logging -- adjusting --- driving----

Imagine this with the narrow German roads, a lifted Tahoe and the Laptop on the center console..... fun stuff..

Harald

[Highlander]

Max vacuum has always been an option, but you would have to log a SPECIFIC route that you can take with pretty much a lot of accuracy in order to find those max vacuum differences. Otherwise there is no better way than a loaded dyno. I have a dyno and its only inertial and I can apply a "brake" load and its still a pain in the butt doing it via the vacuum way.

You can also do it by logging the average TPS with the cruise control engaged. There are many different ways. But the best way is just that one.

[MSURacing]

...I thought timing is ok as long as there is no knock activity? And just in case the load is too big the ECM starts using the low octan table..which I left untouched..

The engine loves it and I get better mileage.

Harald

How much has it changed your fuel economy? You are running about 10 degrees more spark than I do. What type of fuel are you running?