I am really hoping that someone with decent tuning skills may be able to provide an answer for me. I have a general idea of the whole timing methodology but can not for the life of me figure out why some people do certain things.

I am trying to figure out why certain people set thier timing to a fixed number... say 14 degrees as opposed to starting at something like 12 and going to 20 at redline. Right now my timing curve is around 12 at 4k and progressively getting higher until it hits about 20.5-21 at 7.25k and holds it there until the rev limiter (At 8k). I am assuming the reason that people lock thier timing so low is to reduce knock at high boost levels and the highest they can run without knock is whatever number they may be set at (Say 14). Is this truly the reason?

I know AMS on thier shop car is one that does this strange timing thing. Shane, on his car from Elite Motorsports also does this strange thing. I am pretty sure that Tym Switzer on some of his customers cars does this as well.

I tried doing the same thing just for ***** and gr1ns and all it seemed to do is lower the overall HP and TQ... the curve still stayed about the same, progressively getting higher and higher but it just wasn't as steep as an angle it seemed and the peak HP/TQ numbers were lower. I didnt adjust the fuel at all when I did this test so perhaps it was running richer or leaner for that run (Stupid logger can not log both AFR and timing at once). But it really didnt seem like it was going to pull harder or even the same unless it became alot richer.

Please help me out on this thing... it just digs at me trying to figure it out. It still seems the only reason for this is to get rid of knock and that is simply the farthest they can push the timing before it knocks. But if that is the case, why would low power DSM's at around 18psi on a 16g need this low timing. I think I saw a log from a DSM that Tym Switzer tuned that ran this strange 'locked' timing... I couldnt imagine that car would be knocking with more timing up top.

Thanks for any info!

 

What you want to know is easily found in automotive engineering textbooks. Specific spark advance is obviously influenced by quality of petrol, cylinder head design, compression, boost pressure, charged air temp etc. Lots of variables. The general shape of a spark advance curve for a petrol engine is quadratic... i.e. advanced timing at low RPM/load, very little timing at peak torque, and advanced again at high RPM. Deceleration advance can be as high as 35-45 dBTDC.

 

Additionally, some decisions have to be made in consideration to engine reliability and drivability. As you mentioned earlier, if the timing is more less fixed above X RPM, then perhaps the person calibrating the engine is opting for a safe tune if adding 1 or 2 degrees more isn't going to make a significant difference in torque. What constitutes as signficant obviously is open to interpretation and is subjective. The other things to consider are drivability and smoothness. For example hunting idle is sometimes the result of adjacent cells in the ignition map being too far apart. You get the idea.

 

Are the timing numbers that you are seeing comparable to UTEC timing numbers? I seem to recall that the timing numbers on the AEM EMS aren't comparable.

 

Well, I understand the basics of what timing is I am talking about ignition timing.. doesnt matter if it is AEM, Stock, Utec, or any other way of seeing it... it is all the same.

I was actually looking for the specific reason on our specific cars (And DSMs) the reason that some tuners will lock their timing at an arbitrary number that seems very low to me (12 or 14) compared to most 'normal' tunes that are as you suggested... 25 low rpm, 12 peak tq, and around 20 at high rpm.

I have only read that more timing will create more power.. it is possible to achieve a point where adding timing will not create more power instead it will just raise the cylinder pressure but most any tuners will say that they have never gotten to this point before the car starts knocking.

My question is simply why some tuners do this on our cars. Is it to protect against knock because of the boost they run? Are they being 'safer'? Are they running thier cars leaner with less timing... what would the reason be for not advancing the timing further than say 12 degrees at high RPM?

As for the Evo's that are tuned in this way I am almost positive that AMS's shop car is like this.. locked at 12 degrees or so all the way from say 4k to 9k. I just dont see the reason for this.

 

A set timing number is probably easier and safer to tune with, but I've never used a method that gives me full timing control.
The "normal" tunes your refering to are probably done on a piggyback, which does not give control over timing. The ECU is still monitoring and controlling most of what's going on, which makes piggyback so appealing and so easy.


Yes, there is a point where adding timing will not make anymore power. You will also get some piston damage when you reach it. Think off it as a balacing act. In achieving more power from the motor, eveything needs to be in proper proportions or you will get detonation and possibly serious engine damage; timing, octane/fuel, and boost. You can't chage one without another.

 

I certainly wouldn't tune your Evo based on DSM tunes, especially timing. I never in my life saw a 16G'd DSM with timing as low as an Evo at peak TQ. That doesn't mean it wouldn't be possible to run 12-14° at peak TQ on an Evo, but I personally would need 100+ octane or it would be certain detonation on my Evo. I'd be sweating a set 12° at peak TQ every time I stepped on the gas

I can get away with ~9° at peak TQ on pump, but many Evos are even lower than that. I am just suggesting you be a little careful with applying DSM tunes to the Evo.

The process of ignition timing may be generic, but when you start quoting advance numbers from standalone management logs/maps, it is NOT. This is particularly true of the EMS since timing is "relative" and maps can show higher or lower advances depending on parameter offsets and if/how much the crank signal was sync'd to the EMS. Syncing or not can change the timing that can be run in the main map easily +/- 5°.

When the EMS is installed, the crank signal and what the EMS reads (and what you see in the dashboard/logs) likely won't be matched. If you don't sync them though, it really makes no difference since the timing the engine will take is still the timing it will take. The only difference is how much of an advance is applied in the maps and shown in logs. Say the crank is 4° advanced compared to the EMS reading without being sync'd. Setting 8° in the map is actually 12°, but on a sync'd EMS, it's actually 8°. So if 12° actual advance on the engine is where it needs to be at a particular point, one map will show 8° (unsync'd) and one will show 12° (sync'd). That's why I say timing on the EMS is "relative".

Timing on the EMS is definitely different than what is seen with the stock ECU in the car and I will assume you saw this low timing in an AEM map. My highest advance possible on a sync'd EMS with some other offsets altered was 16° where the stock ECU would be upwards of 21-22°. Sync'd with default offsets, that max in the main map was 12° at redline...exactly what you saw. The only time I've seen 20°+ advance in an EMS for an Evo was on C16.

In any event, to get back to your original question, your best bet is to tune for your car and not worry why others timing maps seem weird (I've seen some crazy ones). Timing curves are dependent on so many variables, it would be nearly impossible to say why some run massive timing and some very little (could be very lean, running alcohol, 45+psi, etc.), some are all but flat timing and others still have several advances/retards in a "W" shape. And unless you are looking at logs with actual timing, what you see in main timing maps may not be the only advances in the mangement system. Depending on the system, there could be further advances/retards on top of the main map based on temp, boost, activated switches/conditions, etc. that you are not seeing.

If anything, for pointers, I'd look for tuners using the same management system as you with similar mods/climate/gas/boost and definitely the same car. Start low and tune your own way up...

 

Well i have gotten my pump gas tune pretty good.. My timing is (As seen from a stock ECU) is around 12 degrees at peak tq and climbs to around 20 at 7k and stays there till 8. It seems to work fine and has no detonation. I am just still wondering why people do this timing thing... I am sure the Evo that AMS has at 14 degrees, or whatever it is, is with an EMS but it is not really a map.. it is more of a result. The other thing is that it is on C16.

I know the timing is obviously drastically different stock to stock from a DSM to an Evo (I heard it is the efficiency of the Evo's head mainly that allow it to run lower timing and still create good power) but I still can not see the reason of locking timing unless it is just to make it 'easier' to tune for no knock. Alot of the DSMs that I see with this type timing are using either an EMS or a DSM Link. It would be harder to get the timing on a car to be a flat line using the DSM Link than it would be to let it run like 'normal' timing (Start low and get high) so obviously they are doing this pita tune for a reason... I just want to know what that reason specifically is :P

I guess I am just trying to learn as much as possible about tuning... i have a very fine general knowledge of it and seem to be doing just fine by doing it my way (Car pulls plenty hard and is obviously making the power it should.. trapping at 118 bouncing off the rev limiter near the end of the Qtr Mi.) But I still want to know more. The quest for knowledge is great within me I guess you could say The other reason I am asking about this is because I plan to run pretty high boost sometime soon (Not that much but still around 28-30) and I would like to know any 'tricks' that people have of higher boost levels like that.

To sum it up, I will ask the same question with more information... using a DSM Link (A piggyback) What would the reason be to try to 'fight' the stock ecu into making the timing a straight line from peak tq and on at a low number (Say 12)? It is not using some strange algorithm to decide when to truly fire.. it is what the normal ECU would crap out. Instead of say 20 degrees at the top, alot of tuners force it to drop that number down to be a flat line.. what is the purpose ever... High boost, get rid of knock, spool-up, just easier to ensure a 'safe' tune or what? I just dont get it. Hopefully some tuner that does it this way would care to chime in.. AMS, Elite Motorsports, Tym Switzer?

 

12° at peak without knock is very nice...I can only wish, but it is 100F out here
I see what you are getting at now, though I've only ever seen fairly straight timing curves using standalones, never using a piggy-back with the stock ECU. It's probably for safety due to big boost and a lean(er) mixture. If you've seen adjustments on a piggy-back to try to obtain a flat timing curve, I'd be curious as to why myself. The only reason I could possibly see doing that with the stock ECU in is if it's constantly pulling timing. In that case, I'd look elsewhere, like fuel tuning, lower boost and/or higher octane fuel. Some people prefer to run huge boost and low timing instead of lower boost and higher timing and it may just come down to that.

I'm still on the stock turbo so you'll definitely want to get someone's input running a bigger turbo with more boost. It's entirely possible that the ECU itself won't give a lot of timing on a big turbo with a lot of boost, especially if you are maxing out the MAS. I'd say, turn up the boost a little at a time carefully watching for any knock. Run ECU timing (you're using a UTEC, right?), keep an eye on AFRs and KNK. Do as many knock-free pulls as you can with ECU-controlled timing, average the timing out from all the runs at each RPM point to plug in to your timing map for your absolute values (UTEC-controlled timing) to start with as a base curve and work from there.

I can only hope that 28-30psi is going to be on high octane? It might be possible on pump with really low timing, but yikes! Anyway, I guess I wasn't much help, but I'll be keeping an eye on the thread in case I can learn something new myself Good luck with it!

 

don't forget the evo has higher compression so you can't compare the two. my timing curve runs alot of timing right before boost and tapers down to least amount at peak torque and gradually increases from there. sounds like you got it.

 

Still waiting for a good answer

 

Come on... AMS? Buschur? Switzer? Someone??

 

By the way, I would assume the reason the timing is so different from DSM's to Evo's is two major reasons. One, the head on our cars is much more efficient which enables us to run lower timing and achieve the same results but i would assume the bigger reason is the boost we run stock. Take a stock DSM that stock runs at BEST 14.7 psi... which not many do stock, thier timing is around 15 degrees at peak and almost 20 at top. Our cars run 19psi stock, around 9 degrees peak and 18 up top. The timing really isnt that far off... take a stock DSM and raise the boost to 19 and see what the ecu would do to the timing.. it would drop it to probably pretty close.

The other thing is the size of our turbo stock.Our stock turbo is damn near a '20G' as far as the air it pushes out. It spools like a small 16G for a dsm but pushes almost the same air as a 20g for a dsm. This is also a huge difference that would affect the timing.

Those are my best guesses at least which seem perfectly logical to me at least.

 

Sean Ivy, we need you in here. Need your input.

 

Pull out your dyno and sheet and look at your torque/rpm curve.
The is pretty much your answer, EVOs on stock turbos bang out peak torque down low and start to fall off esp at 6000 rpm. The reason your not adding timing at torque peak is because the cylinder pressures are the highest at that point, you can only use so much before it starts detinating. The reason your adding more timing as you go up is that the motor actually needs it to rev that high and continue making any power (due to falling cylinder pressure) and to not start misfiring. Now if you your turbo was bigger your timing curve would look a lot different, MY T67 SR20 has a torque peak at like 5500-6000rpm so my timing doesn't really start jumping up hard until after the torque peak, and only has until 8000rpm to do it.
When you comparing some one timing curve to your look at their dyno curves, Were these DSM running stock cams? EVO cams are like 256 or something. If the curve looks nothing like your then you cant really just plug in these numbers and expect to change your own curve.
-James