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Top 2GNT Technical Performance/Engine Engine Management Systems & Controllers topic #4228
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Subject: "Timing advance with the S-AFC" Previous topic | Last topic
TeamMetalJimJun-05-03 01:24 AM
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#4228, "Timing advance with the S-AFC"




          

This is treated as somewhat of a curse for turbos...but what about the N/A guys. Bill actually came up with this idea and I figured I'd just bring it up here.

Its a known problem(for turbo guys) - leaning out with with a MAP modifier like the S-AFC will advance the timing. This COULD be a blessing for the N/A guys. I think the general consensus is that we should see about 17 degrees at WOT without leaning it out. How much timing have you seen while leaning it out? 20, 25, 30 degrees? How much did you "lean"? 10%, 20%, 50%? Is it worth persuing as a N/A mod? I mean, it'd be nice to get a few degrees - but it'd be nicer if we could get as much as we want.

The thing about it is, most N/A guys don't have adjustable fuel pressure regulators and don't upgrade to larger injectors. Well what if we did? I don't have an SAFC, but I do have a Field SFC - it does the same thing though(just another MAP modifier). I'll have an adjustable regulator soon enough, and it will be installed before I get the turbo on as well. I don't know how far the ECU will take the timing, or if there's a limit or anything. I suppose the only way to see would be to crank up the fuel pressure and lean it out till the trims are descent. Maybe if that's not enough advance, I could install some larger injectors and see if the ECU advances the timing even further. I have some 30lb injectors for the secondary rail - I could throw those up front and check it out.

What do you guys think? Worth looking into? I know at least one of you have datalogged the "SAFC timing advance"...otherwise how would we know about it? Any N/A guys out there with adjustable FPR, SAFC, datalogger, and possibly bigger injectors willing to check it out? Most of the turbo guys have all of this stuff, but I think the only way to really check this out safely would be to open the wastegate(disable the turbo) but I have no idea if that's even possible without getting any boost creep. I don't want anyone blowing up just to test this theory. But if you CAN disable the turbo without creeping...hmm.

I was planning to look into it after installing my 8-inj fuel system and before installing the turbo, but I just wanted to run the idea past you folks first.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

  

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Replies to this topic
RE: Timing advance with the S-AFC, Global Ruler Of All ThingsDarkOne, Jun-05-03 04:07 AM, #1
RE: Timing advance with the S-AFC, Teamner947, Jun-05-03 04:43 AM, #2
      RE: Timing advance with the S-AFC, ModeratorVX100, Jun-05-03 05:41 AM, #3
           RE: Timing advance with the S-AFC, TeamMichael_97RS, Jun-05-03 06:21 AM, #4
                RE: Timing advance with the S-AFC, BlkTalon96, Jun-05-03 10:33 AM, #5
                     RE: Timing advance with the S-AFC, steve0677, Jun-05-03 11:20 AM, #6
                          RE: Timing advance with the S-AFC, Nitrous_RS1997, Jun-05-03 11:40 AM, #7
                               RE: Timing advance with the S-AFC, TeamAvenger, Jun-05-03 01:11 PM, #8
RE: Timing advance with the S-AFC, TeamMetalJim, Jun-05-03 10:37 PM, #9
RE: Timing advance with the S-AFC, TeamMichael_97RS, Jun-06-03 05:02 AM, #10
      RE: Timing advance with the S-AFC, DarKReaLity, Jun-12-03 06:45 AM, #11
           RE: Timing advance with the S-AFC, Global Ruler Of All ThingsDarkOne, Jun-12-03 07:08 AM, #12

Global Ruler Of All ThingsDarkOneJun-05-03 04:07 AM
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#4229, "RE: Timing advance with the S-AFC"
In response to Reply # 0




          

It does happen, it is a known phenomenon. However, it would be cheaper, to get the added timing advance, to purchase (and make work) an AFX ECU. When you consider the cost of larger injectors, an adjustable fuel pressure regulator, and an safc, you're well beyond the price of an upgraded ecu.

However, just increasing the timing advance may not give the NA power gains you think it will. It would also be an expensive theory to test and tune.

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'95 Eclipse TurboGS (garage deco)
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Teamner947Jun-05-03 04:43 AM
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#4230, "RE: Timing advance with the S-AFC"
In response to Reply # 1
Jun-05-03 04:45 AM by ner947



          

for the record, i was playing around with my AFC and my datalogger this morning on the way into work - with about -2% in the AFC i got about 19 degrees of advance, with -4% i got about 21-22 degrees of advance.

edit: so, i guess you could say it's a 1:1 ratio. seems like a pretty reasonable guess to me. i vote that someone else tests this though, for a good 2nd opinion.


2016 WRX STi Limited (current)
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ModeratorVX100Jun-05-03 05:41 AM
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#4231, "RE: Timing advance with the S-AFC"
In response to Reply # 2




          

Without adjusting my SAFC I would get 20 degrees advance at WOT. With it adjustaed to -10% at the top end, at WOT I would see 23 degrees advance.

I had thought about just leaning it out more to get more timing advance, but I figured it is safer to not push things too far.

And, even though the SAFC could be used to control the amount of fuel added at part throttle and low rpms, with bigger injectors and a new fuel pump I think you would see some driveability issues while cruising around, most likely using too much gas while just driving around, and it would be difficult to get the thing to run right with normal driving (WOT would probably be easier to tune, actually). And of cours the cost of the setup, as Dino mentioned, is costly for what you would get.

Now, we could try bigger injectors that are only a little bit bigger than stock, which would not need the fuel pump. You'd still have to do the tuning at low RPMs/throttle position, but it would not be as far off from stock as the huge injectors/fuel pump/regulator setup would so it might be easier to do. But, I'm not sure how many more degrees of timing you could squeeze out of the car by doing this. If the "a little bit bigger injectors" aren't too expensive, then it could be worth a shot testing it out.

"Tutto fa brodo."

Todd Scungio
98 RS
15.173 @ 90.70 MPH

And also a 2011 Ralliart

  

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TeamMichael_97RSJun-05-03 06:21 AM
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#4232, "RE: Timing advance with the S-AFC"
In response to Reply # 3


          

I'll be swapping back to stock injectors and trying to get the car running.

But I have 30lb injectors that will get a adj. FPR and redo the fuel system. Unless the stock injectors handle everything without being pushed too hard. (which I kind of doubt they will in the final set up). That will most likely be the thing I'll play with when the quad TB is underway. Then I can see timing advance, etc.



15.9 @ 86.7mph

Injen CAI, 55mm TB, P&P Intake, Crower Cams, Hooker Header, ERT/Catco Cat, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

  

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BlkTalon96Jun-05-03 10:33 AM
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#4233, "RE: Timing advance with the S-AFC"
In response to Reply # 4




          

I know Dino mentioned the AFX ECU, but what about all us guys who aren't a 97. There was a thread a few days ago in the performance section and they were discussing the possiblity that the 96 and 97 ECUs are interchagable, but I don't think anyone ever came up with a 100% definate answer. I have a 96, so hopefully it is true, but if it's not, the SAFC might be my only other option (not counting a stand alone which is way too much). Anybody know FOR A FACT if the AFX ECU would work in my 96 MT? It's not worth $500 to me to take a gamble and possibly mess my car up. Anybody know?



--Alpine 7893 Head Unit
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steve0677Jun-05-03 11:20 AM
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#4234, "RE: Timing advance with the S-AFC"
In response to Reply # 5


          

i believe talonspeed is buying the afx ecu for his 96. he's had the 97 in the car for a week now and its still running perfectly. im sure he will give everyone an update.



03 rally red evo viii - stock
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Nitrous_RS1997Jun-05-03 11:40 AM
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#4235, "RE: Timing advance with the S-AFC"
In response to Reply # 6


          

if all you want is timing advance, dont waste money on bigger injectors, FPR, and SAFC. just get a Programmable MSD DIS-2.

www.TeamKLR.com
1997 Silver RS
Wiseco 10.5 Pistons
Eagle Rods
T3/T4 Turbo
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Greddy Exhaust
440's

  

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TeamAvengerJun-05-03 01:11 PM
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#4236, "RE: Timing advance with the S-AFC"
In response to Reply # 7




          

How does the programmable DIS2 Advance timing? It would have to manipulate the crank angle sensor signal to do that would it not? As far as I knew all the ignition ampliers could only retard timing. Not advance it. Correct me if I'm wrong though.

-"Easy Mac"
05 Mazda RX-8 (RR8 #88)
99 Eclipse RS 398whp & 372lb-ft

  

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TeamMetalJimJun-05-03 10:37 PM
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#4237, "RE: Timing advance with the S-AFC"
In response to Reply # 0




          

Those are some good numbers Nathan & Todd. 23 max so far. I wonder if thats the limit.

About the costs...Something like the SAFC definately will cost some ching. Honestly though, most people interested in tuning buy one anyway. The FPR - right now you'de have to buy an adjustable one. But if we could come up with a way to modifiy ours like this http://www.charm.net/~mchaney/fpr.htm or this http://www.fwdmopar.com/sites/dennis/adjfpr.html then it wouldn't cost so much. I mean even if someone came up with an idea like the B&M command flow for our regulators - they're cheap too(relatively speaking). And a datalogger - mine was $122. Yeah it starts adding up....but then again modding always just starts to add up.

I think it'll be a cold day in hell(Sorry Gary) before we see another revision of the AFX ECU. At least thats what it seems like. It sounds to me that this tuning method that hasn't been explored to any great extent with the stock ECU. I'm just trying to explore it.

Dino, why don't you think that having an advanced curve would do much good? The AFX ECU guys seem to enjoy it tremendously, but they have good fuel curves as well. The plain ol stock ECU/SAFC combo can get you the timing - but it robs your fuel. I just think that if you could compensate for the fuel with an adjustable FPR then you would be able to enjoy the same benifits - unless the stock ECU limits the advance. Am I way off base? What am I missing?

I'd like to see more datalogged results. I hope 23 is NOT the advance limit. Like I said, I'm sure some of you turbo guys that used to lean out with the SAFC have an idea of how far the ECU takes the timing.

And btw, I don't think that it's nessicarily dangerous to test this theory. I won't be running boost here so knock would be just as dangerous as if I had filled with a bad tank of gas - bad but not tremendously dangerous. Knock at 10 pounds of boost is a different story. As far as being expensive for me - well I've already bought all of this stuff for the turbo system, but it'll be installed before the turbo and I thought it might be interesting to check out the possibility of actually having a good amount of timing advance with the stock ECU...on behalf of our N/A brethren.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

  

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TeamMichael_97RSJun-06-03 05:02 AM
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#4238, "RE: Timing advance with the S-AFC"
In response to Reply # 9


          

I'm pretty sure the 96 and 97 are the same programming/pin lay out. Everything I see for replacement parts, etc. Has 96/97 lumped together. But I don't know for sure.

I don't know enough details about the programable to know if it uses it's own trigger wheel (which is would have to if you wanted to do any timing advance). No one is going to make a universal box that reads every type of crank trigger, too many variables to make that practicle.

Jim, our ECU runs so rich that leaning it out and getting the timing advance is a double bonus.

  

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DarKReaLityJun-12-03 06:45 AM
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#4239, "RE: Timing advance with the S-AFC"
In response to Reply # 10


          

i'm still trying to find out where is the issue that all us turbo guys have with " too much timing advance". for what i have read, i read no one on this board blowing up their engine due to that, just detonation due to a lean condition on fuel parts related issues,is all i've heard and read. if i was to slap on 52lb injectors,have the right disk on the SFMU(1:1), lower the fuel pressure, and adjust the SAFC a little leaner to compensate, maybe it's not an issue with too much timimg advance as long as you got the right amount of fuel to what you can handle @ your max boost.
if you're going 20+ psi, i think the only issue we got is not running race gas due to lack of octane. i'm currently not having any issues on timing advance for awhile while 15psi, sometimes i even spike to 17psi, and no problems. just sucks my clutch is shitty, but i don't think it's a big issue, unless you're truly making 350+ HP, which is then you should be concerned while making high boost 20+ psi. my goal is 450HP. i don't know, if you guys could clarify that, please i like to discuss about it.

  

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Global Ruler Of All ThingsDarkOneJun-12-03 07:08 AM
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#4240, "RE: Timing advance with the S-AFC"
In response to Reply # 11
Jun-12-03 07:08 AM by DarkOne



          

May people that blow thier motors due to a "lean condition" do it in fact due to excessive timing advance. When you compensate to a large degree with an SFAC, you're throwing off the ECU's calulated load%, which in turn causes it to advance timing. Under less load, more timing is acceptable and desirable. Under high loads, less timing is needed to stave off preignition. When the ECU thinks load is around 70% due to a modified MAP output when it in fact should be nearly 100%, expect to see 30 someodd degrees of timing advance. WOT, uphill, whatever. You'll knock, and in turn break things no matter how perfect your fuel curve is.

People blow these motors because of detonation. They tear it down, see a cracked piston, and know that the motor was detonating. However, most people don't seem to realize that detonation is not just caused by lean fuel mixtures (which really cause HEAT, and HEAT causes preignition) but by many things including improper timing curves. So yes, many people here that have have blown their motors have done it due to improper timing curves, they just don't know it.

______________________________
If a sentence found online has 35% misspellings or greater and includes at least two racially charged expletives, chances are it is a YouTube comment.

'95 Eclipse TurboGS (garage deco)
'95 TSi AWD (restoring a survivor)
'97 Talon ESi-T (poor impulse control)
'99 Eclipse RS-T (daily beater)
'13 Evo X (mostly stock)
'17 Sienna (Middle Aged Dad Mobile)



Factory Service Manuals: http://nawdu.de/files/

  

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