FAQ: Spark Advance (Timing, Retard)

AA wrote:

I was told by someone (a friend who tunes for INTENSE) who spoke to an engineer from GM claiming 26º BTDC was optimum for max torque in a 3800.

Keep in mind that this is also for burning gas - if you are burning E85 I think it burns slower (? not 100% sure right now) which means you need more advance to achieve the same optimum burn timing. That's also at a particular RPM. The faster the engine is spinning the more advance you need to have the burn happen at the optimum time. So even WOT does not have a flat timing curve - it will go from lower to higher as your RPMs increase. So maybe 26 is optimal at the top of the typical RPM range? Only a dyno can really answer this.

charlie wrote:

uhhhh what?

Back when the DHP boards were active, there was one guy with a Grand Prix running a 3.4" pulley on 87 octane. It ran 13.9 in the quarter mile. I'm guessing his boost was somewhere in the 2-3 PSI rage. I think the same car was able to be tuned for 40+ MPG hywy. All spark tuning and breathing mods.

deekster may be right about the E85 timing being different.

EDIT: Here it is, from 2008!

'99 Black GTP Sedan
3.4-2.6" PB Quick Change pulleys, Custom CAI, XP Cam, N* TB, LQ4 MAF, SLP headers, 42.5# Injectors, 180/195* thermostat.

13.501 @ 103.392 on 91 (2.4 60-foot).
13.82 @ 105.28 on 87 octane! (2.42 60-foot).
263kph top end as shown on the GPS.
All this and 39MPG to boot. What more can a man ask for?
* Just another enthusiastic amateur tuner! *

Link: http://www.hptuners.com/forum/showthread.php?16358-97-GTP-unexpected-findings-in-tune

Interesting and real cute, but I am trying to safely run consistent sub 13 second quarter miles. not be a cheapskate hypermiler on 87 octane.

Here is my current spark table. Nowhere near perfection but this is my latest upload. As you fellow tuners know, what you see isnt always what you get when you tune. My WOT timing advance is 17-18 right now with 0 KR at in all cells.

I would say to just keep experimenting as much as possible. Keep bumping up the timing while at the strip between runs until you and/or the times notice a worse result.

matt270avian wrote:

I would say to just keep experimenting as much as possible. Keep bumping up the timing while at the strip between runs until you and/or the times notice a worse result.

That's the plan

deekster_caddy wrote:

AA wrote:

Years ago, I was told once by a respected someone in the 3800 tuning community that 26º spark advance is the point for generating optimum torque in our engine.

Keep in mind that this is also for burning gas - if you are burning E85 I think it burns slower (? not 100% sure right now) which means you need more advance to achieve the same optimum burn timing. That's also at a particular RPM. The faster the engine is spinning the more advance you need to have the burn happen at the optimum time. So even WOT does not have a flat timing curve - it will go from lower to higher as your RPMs increase. So maybe 26 is optimal at the top of the typical RPM range? Only a dyno can really answer this.

Interesting Mr.Deek. Instead of shooting for 26* in the power cells I will go for ~30 and see what happens.

Charlie, might I suggest making or buying a "happy knob" so that you can adjust timing on the fly without having to flash a new tune every time?

matt270avian wrote:

Charlie, might I suggest making or buying a "happy knob" so that you can adjust timing on the fly without having to flash a new tune every time?

Thanks but no thanks.

charlieRobinson wrote:

matt270avian wrote:

Charlie, might I suggest making or buying a "happy knob" so that you can adjust timing on the fly without having to flash a new tune every time?

Thanks but no thanks.

Any particular reason why?

matt270avian wrote:

charlieRobinson wrote:

matt270avian wrote:

Charlie, might I suggest making or buying a "happy knob" so that you can adjust timing on the fly without having to flash a new tune every time?

Thanks but no thanks.

Any particular reason why?

I'd rather dial in the tune and be done with it.

Advise using a stepped attenuator like this one, so you'll know where you're at (and it "goes to 11":

http://glass-ware.stores.yahoo.net/trstat.html

I wouldn't want a continuously variable happy knob, either. Makes it easy to get "too happy".

Knobs are nice if you don't want to pay for dyno time, because you can evaluate and A/B test the adjustment so easily. You can tell when you've reached the optimum timing easier, then set your tune accordingly. You don't need to keep the happy knob installed permanently.

charlieRobinson wrote:

deekster_caddy wrote:

AA wrote:

Years ago, I was told once by a respected someone in the 3800 tuning community that 26º spark advance is the point for generating optimum torque in our engine.

Keep in mind that this is also for burning gas - if you are burning E85 I think it burns slower (? not 100% sure right now) which means you need more advance to achieve the same optimum burn timing. That's also at a particular RPM. The faster the engine is spinning the more advance you need to have the burn happen at the optimum time. So even WOT does not have a flat timing curve - it will go from lower to higher as your RPMs increase. So maybe 26 is optimal at the top of the typical RPM range? Only a dyno can really answer this.

Interesting Mr.Deek. Instead of shooting for 26* in the power cells I will go for ~30 and see what happens.

I would just make changes slowly and watch your knock and O2 sensor. For WOT, pretty much keep advancing until you see KR, then back off a degree at a time until it's gone. Don't just shoot for the moon!

And go buy Greg Banishes Advanced Engine Tuning book. http://www.amazon.com/Engine-Management-Advanced-Greg-Banish/dp/1932494421 worth every penny.

deekster_caddy wrote:

charlieRobinson wrote:

deekster_caddy wrote:

AA wrote:

Years ago, I was told once by a respected someone in the 3800 tuning community that 26º spark advance is the point for generating optimum torque in our engine.

Keep in mind that this is also for burning gas - if you are burning E85 I think it burns slower (? not 100% sure right now) which means you need more advance to achieve the same optimum burn timing. That's also at a particular RPM. The faster the engine is spinning the more advance you need to have the burn happen at the optimum time. So even WOT does not have a flat timing curve - it will go from lower to higher as your RPMs increase. So maybe 26 is optimal at the top of the typical RPM range? Only a dyno can really answer this.

Interesting Mr.Deek. Instead of shooting for 26* in the power cells I will go for ~30 and see what happens.

I would just make changes slowly and watch your knock and O2 sensor. For WOT, pretty much keep advancing until you see KR, then back off a degree at a time until it's gone. Don't just shoot for the moon!

And go buy Greg Banishes Advanced Engine Tuning book. http://www.amazon.com/Engine-Management-Advanced-Greg-Banish/dp/1932494421 worth every penny.

I regretfully bought that book. Didnt learn a damn thing I didnt already know from internet searches/studies. In fact, I learned MORE on the net; stuff he doesnt even cover. I would advise to NOT waste your money on it and instead read from experienced people on the net.

im not doing anything to adjust my timing except writing new tunes to the pcm. no knobs of any sort.

Deek, the latest generation doesn't "read and retain" like you and I did - they "scan and absorb". This puts them at an advantage when taking in a lot of information quickly lots of sources, but makes it more difficult when you hand them a book.

I'll give you $5 shipped for that book, Charlie.

AA wrote:

I'll give you $5 shipped for that book, Charlie.

I'll give you $6, lol. Every bit of information I can get the better.

As far as the happy knob, AA basically said my exact point. It doesn't have to be permanent, just use it as a tool to get everything where you want it and adjust the tune accordingly. Makes the process a little smoother and faster IMO.

I will take $15 shipped for the book.

PM me if you want it.

charlieRobinson wrote:

I regretfully bought that book. Didnt learn a damn thing I didnt already know from internet searches/studies. In fact, I learned MORE on the net; stuff he doesnt even cover. I would advise to NOT waste your money on it and instead read from experienced people on the net.

im not doing anything to adjust my timing except writing new tunes to the pcm. no knobs of any sort.

Wow, really? Every tuning topic is covered in detail, and in language that's easy to understand. The reason I mentioned it again is because the questions you are asking here are covered in there. Sorry to have wasted your money! Sell it to AA.

Or read it again, because it answers your question.

deekster_caddy wrote:

charlieRobinson wrote:

I regretfully bought that book. Didnt learn a damn thing I didnt already know from internet searches/studies. In fact, I learned MORE on the net; stuff he doesnt even cover. I would advise to NOT waste your money on it and instead read from experienced people on the net.

im not doing anything to adjust my timing except writing new tunes to the pcm. no knobs of any sort.

Wow, really? Every tuning topic is covered in detail, and in language that's easy to understand. The reason I mentioned it again is because the questions you are asking here are covered in there. Sorry to have wasted your money! Sell it to AA.

Or read it again, because it answers your question.

Yeah, it's too basic but no worries. I got it because i wanted to learn.
Please show me which pages talks about timing advance while using E85. Or how the 3800 performs with different combinations of boost and advanced timing. It's not there but it can be found on the net by other tuners with documented dyno graphs. It's an interesting read but doesnt delve very deep into the world of supercharged 3800 tuning. It barely scratches the surface, really.

$15 shipped if anyone wants it!

It doesn't discuss E85 specifically, but the discussion about timing does cover different types of fuel and different cylinder pressures, and how that affects the combustion speed, which is what you are really interested in. Ethanol has a slower combustion, which slows the flame front, requiring an earlier ignition. How much, and what is ideal, depends on the shape and size of the combustion chamber, the exact mixture of fuel, the exact blend of fuel and the air fuel ratio you are at, the air temperature, etc. What's optimum? Only a dyno will really tell you if you are getting it right. That's pretty much what he says, I'll have to find the page numbers when I have the book out again.

That's also why nobody else's dyno sheet can specifically tell you what YOUR optimum mixture will be - there are too many variables that affect your optimum. Those are the things he discusses - what those variables are and how they affect the end result. Understanding those things is very important to what adjustment you make next - do you need more fuel or different timing? How is the RPM affecting the advance? etc. Yes, the specifics you need for your engine are not in there, but the concepts are - all of them.

deekster_caddy wrote:

It doesn't discuss E85 specifically, but the discussion about timing does cover different types of fuel and different cylinder pressures, and how that affects the combustion speed, which is what you are really interested in. Ethanol has a slower combustion, which slows the flame front, requiring an earlier ignition. How much, and what is ideal, depends on the shape and size of the combustion chamber, the exact mixture of fuel, the exact blend of fuel and the air fuel ratio you are at, the air temperature, etc. What's optimum? Only a dyno will really tell you if you are getting it right. That's pretty much what he says, I'll have to find the page numbers when I have the book out again.

That's also why nobody else's dyno sheet can specifically tell you what YOUR optimum mixture will be - there are too many variables that affect your optimum. Those are the things he discusses - what those variables are and how they affect the end result. Understanding those things is very important to what adjustment you make next - do you need more fuel or different timing? How is the RPM affecting the advance? etc. Yes, the specifics you need for your engine are not in there, but the concepts are - all of them.

Exactly. This is all common stuff you can get off a wiki page or some nerd's home page. No need to buy a book for it. I was hoping this book would educate me on more advance subjects with actual tuning. He uses screen shots from HPtuners and I like that but it just didnt take me where I was hoping to go. I will give it credit for the topic of fuel injectors though. There was info about injectors that I did not previously know about. Other than tho, I will stick to the net for my research. He has a pretty good collection of books he's authored and I would love to flip through them if they were ever made available at a public library but that will never happen.




Just did a library search for engine tuning books and found this one:
http://www.amazon.com/Modify-Management-Systems-Motorbooks-Workshop/dp/0760315825

nothing by greg b tho.

Right, but the point of the book and it's content is about the concepts you need to know to take your tune to the next level. If you understand the concepts, you can apply them to your actual tune. Do you need more timing or more fuel? What does the dyno and wideband tell you? There is plenty of free info on the net about what the ideal A/F ratio / Lambda is for E85, so after that it's up to you for the rest because every engine is different.

The other problem you are going to have is that you really need to do the optimization on a dyno. Get all the concepts down, over and over, then book some dyno time and execute what you've learned!

deekster_caddy wrote:

Right, but the point of the book and it's content is about the concepts you need to know to take your tune to the next level. If you understand the concepts, you can apply them to your actual tune. Do you need more timing or more fuel? What does the dyno and wideband tell you? There is plenty of free info on the net about what the ideal A/F ratio / Lambda is for E85, so after that it's up to you for the rest because every engine is different.

The other problem you are going to have is that you really need to do the optimization on a dyno. Get all the concepts down, over and over, then book some dyno time and execute what you've learned!

Yeah, I reckon. Dont see a point in going to the dyno until the build is complete. Still got a couple years left until that happens. It will be interesting to see how much more the dyno tune can make after I do my noob tune on it. I, of course ,would hope the dyno would bring out more power but I would smile if they cant get more than a couple horses out of what I give them because my tune is already primo.

The problem with tuning your setup at the track is that you can get a feel for how it's doing overall, but you have no idea about what RPM range is working and what isn't. Because you are using E85, you can and should be running more timing than an E10 or 'pure gas' setup will run. But you also need the right fueling, and to see where the limits are for your current injectors. E85 requires a lot more fuel.

Why are you handing your tune over to someone else? Just watch your power curves, KR and fuel mixtures at the dyno and make the adjustments yourself, now that you understand what you need to know about fueling and timing. Because really it all comes down to fueling and timing, and the concepts don't change. You either are making the power or you aren't. You can probably run a lot more timing at the higher RPM and airmass levels, based on what I saw a few pages back in your timing map, but only if the fueling is good, and you aren't seeing KR.

Remind me - are you using a wideband O2? Do you still have a cat?

deekster_caddy wrote:

The problem with tuning your setup at the track is that you can get a feel for how it's doing overall, but you have no idea about what RPM range is working and what isn't. Because you are using E85, you can and should be running more timing than an E10 or 'pure gas' setup will run. But you also need the right fueling, and to see where the limits are for your current injectors. E85 requires a lot more fuel.

Why are you handing your tune over to someone else? Just watch your power curves, KR and fuel mixtures at the dyno and make the adjustments yourself, now that you understand what you need to know about fueling and timing. Because really it all comes down to fueling and timing, and the concepts don't change. You either are making the power or you aren't. You can probably run a lot more timing at the higher RPM and airmass levels, based on what I saw a few pages back in your timing map, but only if the fueling is good, and you aren't seeing KR.

Remind me - are you using a wideband O2? Do you still have a cat?

I have a wideband with HPTuners and 200 cell cat that will be replaced with vacuum/electric cutout sometime down the road.

0KR right now with 18* WOT on a 2.8" pulley @ ~11.0-11.3 AFR currently. I havent tuned WOT for a few weeks now. I am confident I can drop pulleys. Just need a snout mill tool.

Great! Keep it up, I would work on timing and fueling some more before you drop pulley sizes again. When you drop pulleys, you need even more fuel, etc.

My understanding of E85 is your ideal base A/F ratio should be around 9.8. So your setup sounds a bit lean. Maybe you want to work on that before you drop pulley size again. WOT should be a bit richer.

Did you change the Stoich setting to 9.8? Here's an article suggesting lambda is 9.9 and WOT A/F should be around 8.6-8.9 (and we are supercharged, so it may need to be even richer than that).

http://www.rockettbrand.com/downloads/tech_bulletins/Tech-Changing%20from%20Gasoline%20to%20E-85.pdf

I don't run E85, just basing what I'm saying here on what I've read online about it. That's another reason I'm not giving you specific advice, but again - the concepts are still the same.