5.0 Explorer Timing - SCT Spark TIming Percentage - some interesting observations

[MuscleJunkie]

So I've had some interesting observations on my 2000 5.0 Limited Explorer (Big White) since I've done the Air Box Mod, K&N Filter and Throttle Cable Mod. I also have the OBX headers but this behavior was observed before their installation.

When running the truck at WOT, I would notice at certain times there would be a slight noticeable drop off in power (from baseline - not alot but noticeable) and if I let off on the throttle just slightly then reapplied throttle it would feel as if a larger surge of power would come out of the engine. The surge usually would last between 2 to 5 seconds then again there would be a slight decrease in power which would be remedied by once again letting off of the throttle slightly and then reapplying WOT. Usually this is observed at WOT above 3000 RPM in 3rd of 4th gear and even sometimes in 2nd above 2000 RPM.

I hadn't quite been too sure what could be causing this but it became less of a priority to address because it was only at WOT and the throttle modulation I mentioned above would fix it. That is until today.

Today during some testing of the 93 Octane canned tune from my SCT X4 tuner I decided to go to the gauges function and was observing the Spark Timing Percentage while I was driving. I noticed at WOT above 4000 RPM this figure would read 28.00%. When I would feel the drop in power it would be reading 28.50% then when I modulated the throttle and felt the surge the figure would go back to 28.00%. This would happen each time. Between 3000 and 4000 RPM this figure would be 27.00% and 27.50%.

So I tested out retarding the Spark Timing (in the SCT tune function) on the 2000-4000 and 4000-8000 1st by -1% then -2% and the truck has become much much more responsive and for the most part I am not seeing this intermittent drop off in power as previously described. I am also feeling that there might be even more that can be had but I figured I would post this up here before proceeding further.

So what do you all think? What exactly is going on here with what I am observing?

 

[CDW6212R]

Interesting, it sounds like the tune is off from ideal just enough to notice it by feel. The canned tunes are guesses based on what they think your engine might need the best(timing and A/F ratio). If you can adjust the timing or fuel enough to affect the performance, then the tune isn't quite right, or you're making it worse depending on how close it was to begin with.

If you get done with your changes to the airflow in and out of the engine soon, I'd suggest having it tuned properly to get the most out of it. Mention any irregularities in running like you mention here, so they be sure to address them.

 

[MuscleJunkie]

I tried dialing it up to -3% and seems as if -2% is more of a sweet spot. Spoke with SCT and they immediately asked if I had any type of CAI to which I replied yes and they confirmed (and agreed with you) that their canned tunes really would not account for any type of CAI and the behavior I was seeing was a result of needing a tune for the mods to get the best performance.

 

[MuscleJunkie]

Also BTW - what do you know about the shift pressure settings in the SCT. I tried dialing in 10% on the 2-3 and 3-4 and 5% on the 1-2. Shifts seem sharper now.

 

[SWIGIN]

I have a stand alone tranny controller in my 94 Mustang GT for years now and I can tell you that you can play with the line pressure somewhat with no problems. If you increase it too much you will make a lot of unneeded heat.

I recommend a tranny temp gauge if you don't have one already.

These trannys from what I have found out really like a Trannsgo H2 shift kit and torque converter choice is crucial to great shifts.

 

[MuscleJunkie]

The SCT has one and the truck has the tow package so I think that means a trans cooler too. What are the temp ranges for the trans I should be looking for..

 

[SWIGIN]

My tranny guy tells me to run it as cool as I can. Mine stay below 160 degrees in the hot summer days beating the hell out of it.

On cool fall or spring days the needle might not move off the 100 degree pin.

If you are going to mess with tranny tuning I highly recommend mounting a dedicated temp gauge. One day about 2 years after a major tranny rebuild with about every upgrade under the sun my temp gauge started climbing up towards 200 degrees. Till I got home it was at 250 and th damage was done.

Having a gauge you can see at all times at a glance can save you thousands.

 

[MuscleJunkie]

Thanks, I think I'll do that. How did you have the problem with yours?

 

[SWIGIN]

Turns out my converter was failing. Had I stopped right away when the temp started raising it would have been a simple converter swap instead of a complete rebuild again.

 

[CDW6212R]

The transmission can be adjusted/tuned for shift and timing by both the PCM and by hardware changes. I suggest spending some time and money to optimize the hardware things you can work on with the trans in place, and then adjust the PCM tune. The valve body is critical and some parts in it, plus the solenoids, accumulators, springs, and shifting holes, will improve the lifespan along with the shifting qualities. I'm going to try the "J Mod" soon plus the other parts, once I fix my V6 trans and get that truck working again. I think that project will help a lot, and it would be great for almost any 4R70W, at any mileage.

 

[SWIGIN]

IMO the J mod is a band aid and only the bare minimum. The Trannsgo shift kit replaces several valves in the valve body along with other hardware. I know the kit isn't free but the J mod is just a tease of what's possible.

 

[CDW6212R]

I was only touching on the parts I plan to use. Sonnax makes several items that are helpful and don't come in most "shift" kits. I have the TransGo HD kit and have installed it and many of their kits before. The big items(VB valves) that they and Sonnax include are among what I replace. The main pressure regulator is the biggest one, and Sonnax has two variations of the valve and the spring. I'm going to try their newest version, which instead of being a crank up the pressure system, it varies the pressure in all conditions.

I don't know how that will affect anything differently than the prior parts, or with existing PCM tuning, but it sounds promising. My 98 Limited has what I call a soft/slow 1/2 shift and I'd like to be a lot quicker. When I get my intended mail truck fixed, that 4R70W project is high on my list. I hope it does well enough to get me through base testing, new exhaust steps, testing, and then a new A4WD TC/trans. I would like this trans to be what I rebuild later for my Mercury, which is getting tired at 206k or so.

 

[SWIGIN]

In reality we are talking about much more than a simple shift kit. These kits that include hardware are more of a retune kit then a shift kit.

I just wanted to be sure you weren't one of the '' ZOMYGOD THE JMOD IS THE BEST AND ONLy'' guys.

 

[CDW6212R]

No I've never done the "J Mod", thus my quotes to distance me from it. I read up on it hard a few months ago when I was first planning the project. But I couldn't locate the little box with the special Sonnax PR kit(4R70W-LB1) in it, so I ended up buying another one. That thing happens to be expensive, the high side near $100, $75-80 most places, and $65 from Summit. https://www.summitracing.com/parts/sox-4r70w-lb1

I had to buy something else to get the free shipping, so I got another one of the 4R70W forward drums from Sonnax. That's the heavy duty one I'll need for this truck later, for boost.

The J Mod is very promising, if the installer understands the various hole changes, and carefully selects proper hole sizes, and the accumulator springs. Each 4R model can have varying effects by the same hole in each, so it's definitely not a deal where you find the hole sizes from one example, and assume they will do the same thing for your trans. I had settled on the sizes I was going to use, but I'm sure finding my notes will be tough. We'll see how that goes.

 

[MuscleJunkie]

So I've adjusted the shift pressure at 15% for all shift points and it seems to be a noticeable improvement.

I also am experimenting with adjusting the fuel richness at WOT - now I have it at +4% with the timing at -2%/-1%/-1%

Doing a couple of runs some of the lag/flat spots seems to have lessened or went away - will do a longer test on my next road trip next week. Any thoughts on these settings? Most I can do until I have have a professional tune it I guess.

 

[SWIGIN]

15% sounds like a lot, in my stand alone tranny controller instructions I thought it said to go no more then 10% but I could be wrong.

Of course you are dealing with a mall tune so maybe my tunes are already far above 15% from stock.

Check out http://becontrols.com/ I have the old gen1 unit but you might get some info from that site.