What is your max ignition timing ?
09-16-2019, 11:07 AM
#1
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What is your max ignition timing ?
I had asked this question in a thread I posted in the Scan and Tune forum, but only got a reply from 'ls1wolf' ... maybe I get get more responses here ...
I have a 2011 GS (A6) with a Heartbeat SC. The car has headers, but has the stock cam and heads.
Boost is a modest 7.5 PSI at the top of each gear.
Car runs on 93 pump gas.
AFR stays right at 11.6 during WOT with no knock retard.
___________________________________
I know all engines are different, but I was wondering about what ignition timing I should be getting at the top of a dyno pull (6,300 revs) ...... ballpark of maybe about +18 degrees max ??
Thanks,
I have a 2011 GS (A6) with a Heartbeat SC. The car has headers, but has the stock cam and heads.
Boost is a modest 7.5 PSI at the top of each gear.
Car runs on 93 pump gas.
AFR stays right at 11.6 during WOT with no knock retard.
___________________________________
I know all engines are different, but I was wondering about what ignition timing I should be getting at the top of a dyno pull (6,300 revs) ...... ballpark of maybe about +18 degrees max ??
Thanks,
09-17-2019, 09:52 AM
#2
I would have to guess, but I would say that you’re probably going to be limited to around 14-15* @ WOT/ high rpm. When I was at 8.5psi with the stock heads/cam on 93, I was running a remote tune with only 12.5* and it was pig rich (mid-high 10:1 range on AFR on Dashlogic), so it never knocked once, so I have no idea what the KR limit was at that level on 93 octane.
What kind of timing advance are you seeing now?
What kind of timing advance are you seeing now?
09-17-2019, 11:19 AM
#3
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09-17-2019, 10:51 PM
#4
09-18-2019, 09:19 AM
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St. Jude Donor '15
40* or so at cruise is about the max I see 
(I hate this question and how people usually talk about ignition timing)
But WOT I've been up at 17-18* before but I'm also on E85. Usually more like 16*
(I hate this question and how people usually talk about ignition timing)
But WOT I've been up at 17-18* before but I'm also on E85. Usually more like 16*
Last edited by schpenxel; 09-18-2019 at 09:20 AM.
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CI GS (09-18-2019)
09-18-2019, 09:35 AM
#6
Instructor
Add it till it knocks then back it off. 7lbs is low IMO bump it to 10psi and add methonal. Works great with PD blowers
Last edited by Racerbox77; 09-18-2019 at 09:38 AM.
09-18-2019, 10:08 AM
#7
Team Owner
Asking questions like this is how motors pop. Each car is different. If you chase a timing number, you will get poor results. If you have a competent tuner, then he set the timing where it should be.
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09-18-2019, 12:27 PM
#8
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I just asked this simple question because I was interested in what the average SC LS engine has as far as timing is concerned.
I am NOT using this info in order to tune my engine ... It has already been tuned on the dyno by a very reputable tuner ... and I don't have access to anything that will allow me to go in there and change the timing anyway.
I am not 'chasing' any timing numbers !
_________________________________
This question is really not much different than asking someone what RWHP they are getting ..... Whatever RWHP somebody else puts down does not effect me, but for some reason, we all ask each other what HP numbers that get on the dyno.
I have learned a lesson with this ..... I will NEVER ask anyone again what ignition timing they get.
I am NOT using this info in order to tune my engine ... It has already been tuned on the dyno by a very reputable tuner ... and I don't have access to anything that will allow me to go in there and change the timing anyway.
I am not 'chasing' any timing numbers !
_________________________________
This question is really not much different than asking someone what RWHP they are getting ..... Whatever RWHP somebody else puts down does not effect me, but for some reason, we all ask each other what HP numbers that get on the dyno.
I have learned a lesson with this ..... I will NEVER ask anyone again what ignition timing they get.
09-18-2019, 01:06 PM
#9
Who cares what anyone else is running? Your car needs to be tuned for its particular setup throughout the rpm band. Just because one guy is running 19* and another 11.5* doesn't mean that either approach is right for your car.
09-18-2019, 08:25 PM
#10
I just asked this simple question because I was interested in what the average SC LS engine has as far as timing is concerned.
I am NOT using this info in order to tune my engine ... It has already been tuned on the dyno by a very reputable tuner ... and I don't have access to anything that will allow me to go in there and change the timing anyway.
I am not 'chasing' any timing numbers !
_________________________________
This question is really not much different than asking someone what RWHP they are getting ..... Whatever RWHP somebody else puts down does not effect me, but for some reason, we all ask each other what HP numbers that get on the dyno.
I have learned a lesson with this ..... I will NEVER ask anyone again what ignition timing they get.
I am NOT using this info in order to tune my engine ... It has already been tuned on the dyno by a very reputable tuner ... and I don't have access to anything that will allow me to go in there and change the timing anyway.
I am not 'chasing' any timing numbers !
_________________________________
This question is really not much different than asking someone what RWHP they are getting ..... Whatever RWHP somebody else puts down does not effect me, but for some reason, we all ask each other what HP numbers that get on the dyno.
I have learned a lesson with this ..... I will NEVER ask anyone again what ignition timing they get.
Besides, I gave up my ignition timing willingly!
Now, when are you gonna crank the boost up? Cause that will need another retune, and different ignition timing...
09-18-2019, 09:47 PM
#11
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I am happy with the HP I get for normal street driving here in the US and I don't have to go hunt down any special gasoline or fluids to spray into the engine.
The car basically makes the same power as a bone stock C6 / ZR1 .... good enough for me
09-18-2019, 10:01 PM
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St. Jude Donor '15
Just busting your *****. The problem is people find these threads later that are trying to tune their newly SC'd Corvette so they just stick a number in that they found and go with it. And honestly if it's a pretty common setup and a reasonable number, it will probably be fine (though probably not as good as it can be).. but not always.
I put the ignition timing as an overlay on this video of a 1/2 mile run I did, you can see the Wideband and boost #'s too.. so you can see what I was running. 17, 18*, something like that. Keep in mind that was with E85 and meth and I blew a head gasket at some point, not sure if it was this run or not. It also had 200K on the engine and has been fine with this much timing ever since once I swapped it out and added some studs so I don't think the tune alone did it..
Ignition timing is a funny thing. There are a lot of pieces really going into what works, even though the desired outcome is pretty simple, i.e. max cylinder pressure occurring at about 15* after TDC.
Pieces that matter, in my opinion:
-RPM. You have less time between TDC and 15* after TDC as RPM increases, meaning you need to ignite the fuel earlier, i.e. "higher" ignition timing to get the same result, all things being equal
-Flame propagation speed. This is a tricky mix between airflow per cylinder event going up in some setups (i.e. centri setups) or staying pretty level on others (i.e. PD setups) and AFR. More airflow, bigger/faster boom, so the less timing you need for the same result. Once you get richer than 0.85 lambda things tend to slow down a little, meaning you need "more" timing to get the same result
-Intake air temp. There's a real reason OEM's pull timing as IAT goes up.. it isn't just because they like making less power. Higher temp means faster "boom" which means you NEED less timing for the same result. The extra heat probably doesn't help with the potential for knock either, so I'm sure that's part of it too. But the factory calibrators aren't idiots for including this, though plenty of aftermarket tuners are idiots for removing too much of this in their tunes
-Octane. None of this matters if the air/fuel go boom before you want it to.. which will happen with enough heat/cylinder pressure if there isn't enough octane and promptly destroy your pistons
That's all I've got on it right now, need to get some sleep.
I put the ignition timing as an overlay on this video of a 1/2 mile run I did, you can see the Wideband and boost #'s too.. so you can see what I was running. 17, 18*, something like that. Keep in mind that was with E85 and meth and I blew a head gasket at some point, not sure if it was this run or not. It also had 200K on the engine and has been fine with this much timing ever since once I swapped it out and added some studs so I don't think the tune alone did it..
Ignition timing is a funny thing. There are a lot of pieces really going into what works, even though the desired outcome is pretty simple, i.e. max cylinder pressure occurring at about 15* after TDC.
Pieces that matter, in my opinion:
-RPM. You have less time between TDC and 15* after TDC as RPM increases, meaning you need to ignite the fuel earlier, i.e. "higher" ignition timing to get the same result, all things being equal
-Flame propagation speed. This is a tricky mix between airflow per cylinder event going up in some setups (i.e. centri setups) or staying pretty level on others (i.e. PD setups) and AFR. More airflow, bigger/faster boom, so the less timing you need for the same result. Once you get richer than 0.85 lambda things tend to slow down a little, meaning you need "more" timing to get the same result
-Intake air temp. There's a real reason OEM's pull timing as IAT goes up.. it isn't just because they like making less power. Higher temp means faster "boom" which means you NEED less timing for the same result. The extra heat probably doesn't help with the potential for knock either, so I'm sure that's part of it too. But the factory calibrators aren't idiots for including this, though plenty of aftermarket tuners are idiots for removing too much of this in their tunes
-Octane. None of this matters if the air/fuel go boom before you want it to.. which will happen with enough heat/cylinder pressure if there isn't enough octane and promptly destroy your pistons
That's all I've got on it right now, need to get some sleep.
Last edited by schpenxel; 09-18-2019 at 10:01 PM.
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09-19-2019, 11:13 AM
#13
Burning Brakes
Ignition timing is a funny thing. There are a lot of pieces really going into what works, even though the desired outcome is pretty simple, i.e. max cylinder pressure occurring at about 15* after TDC.
Pieces that matter, in my opinion:
-RPM. You have less time between TDC and 15* after TDC as RPM increases, meaning you need to ignite the fuel earlier, i.e. "higher" ignition timing to get the same result, all things being equal
-Flame propagation speed. This is a tricky mix between airflow per cylinder event going up in some setups (i.e. centri setups) or staying pretty level on others (i.e. PD setups) and AFR. More airflow, bigger/faster boom, so the less timing you need for the same result. Once you get richer than 0.85 lambda things tend to slow down a little, meaning you need "more" timing to get the same result
-Intake air temp. There's a real reason OEM's pull timing as IAT goes up.. it isn't just because they like making less power. Higher temp means faster "boom" which means you NEED less timing for the same result. The extra heat probably doesn't help with the potential for knock either, so I'm sure that's part of it too. But the factory calibrators aren't idiots for including this, though plenty of aftermarket tuners are idiots for removing too much of this in their tunes
-Octane. None of this matters if the air/fuel go boom before you want it to.. which will happen with enough heat/cylinder pressure if there isn't enough octane and promptly destroy your pistons
Pieces that matter, in my opinion:
-RPM. You have less time between TDC and 15* after TDC as RPM increases, meaning you need to ignite the fuel earlier, i.e. "higher" ignition timing to get the same result, all things being equal
-Flame propagation speed. This is a tricky mix between airflow per cylinder event going up in some setups (i.e. centri setups) or staying pretty level on others (i.e. PD setups) and AFR. More airflow, bigger/faster boom, so the less timing you need for the same result. Once you get richer than 0.85 lambda things tend to slow down a little, meaning you need "more" timing to get the same result
-Intake air temp. There's a real reason OEM's pull timing as IAT goes up.. it isn't just because they like making less power. Higher temp means faster "boom" which means you NEED less timing for the same result. The extra heat probably doesn't help with the potential for knock either, so I'm sure that's part of it too. But the factory calibrators aren't idiots for including this, though plenty of aftermarket tuners are idiots for removing too much of this in their tunes
-Octane. None of this matters if the air/fuel go boom before you want it to.. which will happen with enough heat/cylinder pressure if there isn't enough octane and promptly destroy your pistons
Good morning!
Anyway, maybe something about ignition timing should be still added:
- how do you going to use your new setup?
Less than 5 seconds on WOT at dyno or 2 miles of WOT at airfield? Two completely different things from the point of engine longevity.
I remember being in Germany 10 years ago around Christmas and because of poor navigation I ended up being 120 miles from the dock I should have been 1.5 hours before my ferry was leaving.
Well, unlimited autobahn, albeit snowing, and flatout with small Volkswagen I was able to catch the ferry. So one hour with maximum performance and that small engine was easily able to cope with that.
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schpenxel (09-19-2019)
09-24-2019, 09:15 AM
#15
Like the other guys mentioned, there's a bunch more variables. The big one you're not mentioning here is IAT. It has a HUGE effect on how much timing the engine will tolerate. Some tooners like to zero out or greatly reduce the values in the spark vs IAT tables, but they're in there for a reason. I find that the OEM compensation is actually pretty darn close even for boosted applications.
Soooooo... *IF* you have decent IAT's, you might expect something like 16* total advance up top at your flow rate, but that depends on how much timing adjustment is in there for IAT and AFR. You have to let those adjustments work if you want the engine to live and be happy across a wide range of conditions. Longer boosted runs will just drive IAT up as the intercooler heat soaks, and the ECU should retard timing accordingly.
Above all else, if it's knocking, timing MUST be reduced. I recommend that people calibrate such that there is basically no knock sensor activity under load on "normal" fuel for the application.
Soooooo... *IF* you have decent IAT's, you might expect something like 16* total advance up top at your flow rate, but that depends on how much timing adjustment is in there for IAT and AFR. You have to let those adjustments work if you want the engine to live and be happy across a wide range of conditions. Longer boosted runs will just drive IAT up as the intercooler heat soaks, and the ECU should retard timing accordingly.
Above all else, if it's knocking, timing MUST be reduced. I recommend that people calibrate such that there is basically no knock sensor activity under load on "normal" fuel for the application.
09-24-2019, 03:06 PM
#16
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St. Jude Donor '15
Just add more meth
IAT problem solved
IAT problem solved
09-25-2019, 01:38 PM
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St. Jude Donor '15
09-26-2019, 12:07 PM
#20
Melting Slicks
For many engines knock begins at a frequency beyond human hearing
never rely on audible knock as an indicator of anything
for knock sensors,
OEM typically calibrate sensor (hardware OR software calibration) to detect exact frequency range of knock inaudible sound waves throughout engine substrates (e.g. cylinder block/head and metal materials directly in contact with combustion component)
These frequency ranges are set by the exact nature of each engine's internal parts, so if any part is changed (crankshaft, valve, lifter, etc...) then it is possible the frequency of detectable knock range has also shifted and now you may or may not still be able to detect all forms of knock using calibrated OEM system.
Rule #a53471: never rely on knock sensor or use knock sensor to adjust for ignition timing performance margins
instead, use the right combination of engine/chassis dynometer and load based empirical investigation
never rely on audible knock as an indicator of anything
for knock sensors,
OEM typically calibrate sensor (hardware OR software calibration) to detect exact frequency range of knock inaudible sound waves throughout engine substrates (e.g. cylinder block/head and metal materials directly in contact with combustion component)
These frequency ranges are set by the exact nature of each engine's internal parts, so if any part is changed (crankshaft, valve, lifter, etc...) then it is possible the frequency of detectable knock range has also shifted and now you may or may not still be able to detect all forms of knock using calibrated OEM system.
Rule #a53471: never rely on knock sensor or use knock sensor to adjust for ignition timing performance margins
instead, use the right combination of engine/chassis dynometer and load based empirical investigation