Question on PT spark advance

[ronbo422]

I'm in the hunt for some slightly better fuel economy out of my 5.7 w/6-speed trans. I know from previous tuning experience (2 1/2 decades ago) that adding a few degrees, in the cells where the car cruises at, will help.

My question is does the Dodge mapping use PT Base for its spark advance under light-load applications, or does it use MBT Base in those instances? Or is it a combination of maps?

I added a degree or two in PT Base where the cruise control is set to 65MPH on flat road. (Aircharge - .25g, RPM - 1504, MAP ~50kpa, Advance - 23.5?).
After adding those couple of degrees in PT Base map, there was only a tenth or two of actual timing change on my next test drive. So that got me thinking and looking for another table. That's when I found the MBT Base map, and the advance value is 24? in that particular cell. In the PT Base map, I had raised it to 25.5?. The MBT Base map value seemed more accurate of what I was logging.

So, I figured I'd seek some insight from the forums.

TIA,
Ron

[LilSick]

is your pt vvt adjustment disabled? wait 2014 is it gpec or what os?

[HaasExp]

That's when I found the MBT Base map, and the advance value is 24? in that particular cell. In the PT Base map, I had raised it to 25.5?. The MBT Base map value seemed more accurate of what I was logging.

That makes sense as the MBT map actually "caps" the maximum allowable timing advance. You will need to increase the MBT map at that rpm/load cell (and surrounding cells) to allow the timing to reach what you are commanding in the PT base map.

[ronbo422]

is your pt vvt adjustment disabled? Wait 2014 is it gpec or what os?

GPEC2 OS is 68212721ah

VVT is still enabled.

[ronbo422]

That makes sense as the MBT map actually "caps" the maximum allowable timing advance. You will need to increase the MBT map at that rpm/load cell (and surrounding cells) to allow the timing to reach what you are commanding in the PT base map.

Thanks! That's good info to have going forward.
~Ron

[LilSick]

Yes, and i would disable vvt in - Spark > Adv > Part Throttle VVT & MBT VVT

My 6.4 gets better mileage with the cam at around 117 deg cruising (ECL); and those spark adjustments disabled.

I think cam timing is gonna yield larger efficiency improvements than the 2 deg of ignition timing but curious what ya find

[ronbo422]

When you recommend disabling them, they're tables. How do I go about disabling them?


Ron

[rays04gtx]

Torque model>general> Table 45542 is spark efficiency table. the spot that's circled I've had good mileage results with increasing those #s by 5-10%

Keep in mind 90% of the time your car is under .40 aircharge your off the gas, my point is , those High spark values you see are there to burn unburnt fuel.

You're not going to gain much in the way of fuel millage with increasing spark values above .70 aircharge.

Next step in mileage quest should be VE(speed density) , I myself don't do a lot of Neural Network tuning , but it's my understanding that's the area you want to spend some time on for better Fuel Mileage

[LilSick]

When you recommend disabling them, they're tables. How do I go about disabling them?


Ron

Yours is different huh? Post the tune

[LilSick]

Torque model>general> Table 45542 is spark efficiency table. the spot that's circled I've had good mileage results with increasing those #s by 5-10%

Keep in mind 90% of the time your car is under .40 aircharge your off the gas, my point is , those High spark values you see are there to burn unburnt fuel.

[ECM] 45542 - Spark Efficiency Inverse: "Converts a desired spark efficiency into a spark retard. Usually used for torque management purposes." i dont think so...

Whats your understanding of that table ray?

[rays04gtx]

Look at the Attachment EF(A) , you'll see that it's commanding 28* @ 4300RPMs while on the PT table, @75 KPA , but the MBT Table {Attachment EF(2)} in the 75-80KPA area max is

27* @4016 &26* @ 4416 table, that 28 it's Commanding is coming from Table 45542 because this engine is operating below 73% (BSFC)

when we bumped Cell value 81.4 & 88.2% up to 30* we gained 3mpg out of this ole pig of a ram truck.

[ronbo422]

Yours is different huh? Post the tune

Here's the tune I was working with.

[HaasExp]

Look at the Attachment EF(A) , you'll see that it's commanding 28* @ 4300RPMs while on the PT table, @75 KPA , but the MBT Table {Attachment EF(2)} in the 75-80KPA area max is

27* @4016 &26* @ 4416 table, that 28 it's Commanding is coming from Table 45542 because this engine is operating below 73% (BSFC)

when we bumped Cell value 81.4 & 88.2% up to 30* we gained 3mpg out of this ole pig of a ram truck.

That has to be some weird NGCx ECU logic right there. Does not seem to do that on the GPECs, which I assume is the ECU in question.

[PurpleRam]

Gpec depends on what fuel boundary , Gpec also has a few more tables to call on/use before it gets to this.