Does nonWOT timing need to be modified?

[ArthurJGuy]

• Stock displacment LS2
• 231/239 .644/.651 115+3 Cam
• TFS 220cc Heads
• LT's / 3" Catback
• TVS1900

The bypass valve on the TVS1900 is open at all times, so the car is N/A until ~100kpa when the bypass valve closes and boost comes in.

Is there any reason that my high octane timing table should be modified when NOT at wide open throttle? I'm not sure if the cam will have any effect there or not.

[5_Liter_Eater]

The OEM spark table was "theoretically" ideal for the stock setup. That cam is a far cry from stock so if you wanted to get every last drop of power and efficiency at all times you should re-tune the spark and fuel tables across the board. Unfortunately the only real way to do this is to put it on a load bearing dyno where you can hold it in a cell and play with timing to see what spark makes the most power in that cell. How much is to be gained by that is hard to tell but I can tell you I don't know of anyone (Greg Banish maybe) who does it this way. You could try setting the cruise control and playing with the timing with VCM controls and watching for an increase or decrease in delivered torque. I donno how well that would work though.

So the short answer is no, you don't have to re-tune part throttle spark. Now if you had to scale your airflow tables for bigger injectors I would make sure you scale the spark tables too.

[IDRIVEAG8GT]

In my opinion you should go set the cruise control in a high gear and make it run up a hill. As the car applies more throttle if it bucks any with that cam, increase the timing until it starts detonating, or until all the bucking and surging goes away. You're shooting for smooth power. Once you get that cell right, adjust the rest of the table up with the same amount of timing increase you put in. Just my .02 though, because I did all my street driving tuning without a dyno and it is very nice.

[eficalibrator]

...I don't know of anyone (Greg Banish maybe) who does it this way.

Well, that's how GM does it. Remember that they do the vast majority of spark mapping on an engine dyno before it ever sees a car. If you have a bigger cam with more overlap, you'll have more EGR dilution at part throttle which effectively slows the burn rate. If you want good throttle response and fuel economy in this condition, you will probably need to advance the timing some to compensate.

In practice, this can be very time consuming if you wanted to hit every cell in the spark map. My real world compromise is usually to spot check a handful of part throttle points and try to optimize them. If you find that they all want another 3-4 degrees of timing, then it's not a big stretch to say that the same adjustment can be made to all the points between them. You just have to remember that at part throttle, you're not after the knock limit but MBT. I see a lot of guys just advancing part throttle timing until they get knock activity and backing off a hair but that can leave you on the other side of the MBT curve that's just as bad as being under-sparked.

[murphinator]

I spent several years commuting 2 states from home daily and messed around with cruise timing a lot just to reduce boredom lol

I am sure a dyno is the best way but I opened up my timing histogram and watched the 4 or 5 cells that my car was primarily staying in during my highway commute which was typically 72/73 mph and stedy state , its been a while but I recall the cell it was in highlighted in yellow while the rest of the table was blue , you can also choose cell counts and it will show you which cells you are in the vast majority of the time

. I was able to add a lot of timing in those cells that were hit while maintaining speed on flat sections , downhill ( decreasing load) and slight inclines , higher inclines it might start getting into higher load cells and or boost and wouldnt take any more timing without getting into knock .

it is shocking how much less pedal pressure was needed to climb a slight grade with increased timing - the power increase was obvious , one of the most satisfying things I have done with the tuner

all this gave me an "island" of high timing in my table so I did some smoothing to blend it all in after

obviously theres some guys that have a heck of a lot more knowledge than I do in this thread lol but thats just my personal exploits into cruise timing and I felt it was rewarding

[madvette08]

If you can get to a Load Bearing Dyno, that would be best way to see if the Spark table needs to be optimized.

On the Mustang Dyno we have, I use a feature called PRO Test. With this test you can set it to hold a constant RPM, MPH, PAU Force, Power and Acceleration. Using the VCM Controls I can hold Throttle Position constant to maintain that Load. On Gen 4's it quite time consuming and on GEN 3's with the real timing tuning its a less time consuming. And of course this test is great for Tuning the MAF and VE tables.

If your going to do that on a Dyno make sure you have adequate Airflow for cooling or motor will get nice and toasty .

Ian