Spark advance?
 

I am playing around with my "Transmission Only" stock tune to see what I can do for max fuel economy. What is a "normal" amount of spark advance at 87 octane? It's at 1.25 right now and seems fine. Do I keep bumping it until I get valve rattle, then back down one notch? That's pretty much the drill I remember from adjusting a distributor long ago.

Thanks.

Unlike the distributors, these modern vehicles are able to retard timing if it becomes over advanced.

Have you tried running the other tunes? For me, the tow tunes get me by far the best fuel economy.

I have. I ran the stock towing tune until I got my 87 Custom Performance. I have run the 87 Performance for about 8 weeks. I'm just playing around with it. Initially it looked like I was getting better MPG. but it was because my wheel size got whacked when I switched tunes. I've just about got that dialed in so I can make a good comparison. I must remember to WRITE IT DOWN this time. It seems that the tranny only tune is doing a hair better on gas, but I can't tell until I get the tire size right. I guess then I could do a tank on each (all three) and compare. Is there a "normal range" on the spark advance?

What kind of mileage were you getting on the tow tune?

What do you mean by range?

Also, which programmer do you have?

Seems like the tow was about 14-14.5 (about 70%city/30%highway.) Seems like Custom 87 Performance was a shade better. Truck is on '04 SCrew 5.4.
Tuner is the Gryphon (original, not CTS) I'll be doing a little more highway driving this weekend. Curious to check it there. I once (only once) got 18 an an all highway trip. It was before the Gryphon, but I had fresh oil/filter. I'd love to see that again.

Oh....range. I mean "what degree of spark advance is normal/acceptable with our trucks?" Mine's at 1 or 1.25 right now. Just curious if I should advance it more, leave it alone, or back it down some.

one more time. I'm talking about the TIMING setting in the "Custom program" options. Sorry. I do realize that the advance changes automatically under load.

The typical setting is 0. This doesn't mean that the advance is zero but the degrees of advancement from the baseline is zero.

If you advance it too much, the computer will automatically start pulling timing. Often it pulls in large amounts and makes people think they need to then advance more. You probably aren't at the point yet but if you keep a spread sheet and have a very regular route, you'll be able to see when it yanks a bunch of timing because performance and mileage will drop. I would not keep raising the timing advancement without running higher grade fuel.

Perfect. That's what I needed to know. So, do you think I'm ok at 1.25?

Without sitting in your truck I can't say for sure. I will say that if you were to carry that 1.25 to the level 2 or 3 tunes, you'd probably be asking for trouble. Basically you are only adding timing to the stock engine tuning.

I should add things like cam timing are modified in the other tunes, which is why you can't drop the ignition timing to run low octane on a high octane tune.

Your mixed driving looks pretty good. I have a spread sheet with a weighted average for mileage. I'm currently sitting at 45% city driving with 14.8 mpg on nearly 6000 miles.

Also, do not trust the electronic MPG displays, they all lie. Only use hand written or spreadsheets.

In the Transmission Only tune, you're probably OK with that spark advance, since the tune itself has not modified the engine parameters at all. I would be VERY careful about trying to advance the spark on either the Level 2 or Level 3 tunes though. The spark has already been adjusted in those tunes for best performance.

- Jack

Yep. I tried to advance the timing on Bill's Custom Performance, and immediately brought it back because the valve were rattling. Do you have any idea how far it's advanced in those custom tunes? Just wondering how much is (clearly) too much.

Drove to Auburn, AL last weekend and got 15.8 MPG on the Custom Performance tune. The tankful was probably 90% highway, but some idling around town getting out of game traffic. There were five people, with about 70 lbs. of sousaphones (marching tubas) in the bed.

I feel like I should be able to do a little better than that on the highway. Before I had my tuner, I actually got 18 hwy going to and from Auburn (just went, then came right back, so it was ALL hwy.

I am giving the Tranny Only tune another try to see if it's higher or lower than the 15.8. Obviously it's not a direct comparison because this tank will be only about 30% hwy. After that, I give the stock Towing a try.

I always calculate my MPG when I fill up. I WISH I was getting what the Gryphon says:)

Do not advance the timing on Bill's tunes. He is the automotive engineer. Five people and gear? That is like carrying an extra 600 pounds. That will have some influence on fuel mileage. Also, higher speed highway will have an effect compared to slow highway. For mileage comparisons you need to try them all under nearly the same exact conditions. That is how I found my tow tune actually gets the best mileage.

Heh. Found that out REALLY quick when I tried. that's why I'm playing around with the trans only tune instead I wish we could know the exact specs on Bill's tunes, but that would be bad for PHP's business. I know my truck will never get the mpg of my wife's minivan, but I want to get all I can. The Gryphon was designed as a performance tool, not an economy tool, I get that. But......if Bill were to write a "max mileage" tune I'd definitely be interested.
I guess you can only do so much with a 5000K-plus vehicle pushed by a 5.4l V8. I REALLY like my truck....everywhere but the gas station.

BTW-Is you Tow tune one of Bill's, or stock?

He isn't only adjusting ignition timing. Some of the gains also come from cam timing adjustments. He also has full access to fuel strategies and things I can't even imagine, especially part throttle where any gain would be found. Something you do not have access to.

He used to have mileage tunes and people hated it. It was weak in performance and people had this strange idea that they could load that tune up and hot rod around and it would give them better mileage. I'd say close to 70% of mileage gains are solely on the driver. Other things like maintenance and strategic modifications bring up the last 30%. Buy a vacuum gauge. It gives you real time manifold pressure (vacuum). More vacuum means less air, less fuel and better mileage. It trains you how to drive.

My tune was a custom by Cody. I had asked him to do a bunch of crazy things because it was a special application tune and, although it took a few tweaks, he pulled it off. It is only giving me 13-14 around town and up to 18 highway so nothing super special. Just consider that it will cost you 20-30 cents per mile to drive the truck. Want to cut down on cost? Streamline errands to minimize mileage.

Also, one tank is not a reliable test. If I showed you my mileage you'd see numbers ranging from 10 to 17.9.

Everything Longshot just said is bang on. I asked Bill for a tune that would maximize highway economy but still give me good passing performance when I needed it. As far as I'm concerned, he nailed it.

My truck, a 4x4 SCrew with a bed cap and factory tow is probably a lot heavier than yours. I get about 15.5 mpg in highway driving averaged over MANY tankfuls (I use a spreadsheet do do this). And, one factor that has a big effect is headwind. If I'm driving into a headwind at 70-75 mph, it probably cuts my mileage by at least 2 mpg.

Do try the tow tune, and don't "tinker" with it much. I think you'll like it.

One thing you CAN try though if you're trying for economy, is to change the part throttle shift and torque lock points. I reduced mine by the max for all upshifts and downshifts and gear ranges. My goal was to get the truck into the highest gear possible at the lowest speed with the torque converter locked. This has reduced the tendency of the truck to downshift so quickly on uphill grades and of course gets it into 4th gear at lower speeds. There's probably a bit of "point of no return" here, I may have reduced these too much, but I can't tell much difference between what I have and a more mild reduction. It's all about optimizing the engine load for efficiency.

This only effects part throttle acceleration. Wide open throttle is not changed.

- Jack

Thanks both of you. I have already reduced Converter lock the max amount on 1-2, and 2-3. I had it way dow on 3-4, but I was having problems with downshifting at unusual times so I brought it back closer to center. My shift points are lowered by only 1 MPH. Maybe I'll try lowering it some more. If I do, should I keep the downshift points matched with the upshift ones?

Yes, they must be the same to avoid transmission confusion and trouble.

Oh yeah. You told me that on another post. I was studying the graph you posted. What are the units on the axes? I would guess MPH, and RPM, but I'm not sure.

The graph is actually multiple graphs overlaid upon each other. The X axis is time from the start of recording. The Y axis is just a scale where the individual graphs must be multiplied or divided by factors of 10 to match. Or in other words, just the red line is MPH with the graphed line being 10x of the true value. The green line is 1/10 of the true RPM.

Ahh... Makes sense. Will study it some more tonight. Thanks again.

MPG is all about driving habits. The headwind is an aerodynamic issue (drag) and definately makes a difference. With my 2006 4.6 4x4 SCAB 6.5' bed at about 200' MSL, I find I get the best mileage at an effective 55-60 mph (accounting for any/no headwind). About 19 mpg if traffic cooperates. Increase speed above 65 mph and mpg drops about 3-4. Add a light trailor and the road friction (extra tires) comes into play-drop 2 mpg. Sitting at lights in town traffic...is like pouring gas onto the road while idling. Makes me want to scream as mpg drops to around 9-10. Strangely (or maybe not) my truck responds best to moderate acceleration to cruise speed rather that a slow acceleration. This is using the canned 87 tow tune.

I drove a friends 2005 5.4 2wd SCAB 5.5' bed this summer at higher elevations, (2000-4800' MSL) and saw very similar results. No tuner on his truck and it felt like a wallowing pig compared to mine.

I also tried running a three consecutive tanks of no-ethanol gas as an experiment. Despite theory on energy potentials of ethanol blend vs pure gas, my actual results showed no difference whatsoever in my mpg.