Terribly lazy calibrating. Wow. You have the capability of 3D ignition maps, and you flatten it all out to locked down timing. ZERO advantage. Ability is there to make proper curves. Use it.
LOL. Figured so much. Is there a major power advantage difference? It does seem as though the motor can take a bit more timing down lower in the RPMS, but as the rpms climb the ramp rate of timing cannot continue and it it has to flatten out.
Ex. Timing from 2700 to 3500 increases +3* every 300rpms or so. As you get past 4500 timing increases 1.5* every 300 rpms.
The motor might have a knock resistance up to 24* timing advance at 3500, and the same across the board. Why not max it out at each rpm interval.
In other words, if i increased timing until I saw knock at every rpm, I will find it can resist pretty much 23-25* of timing across the board.
Question - stock / S2 /s3 all use a timing curve, starting from 13-14* around 2700 up to 25-26* by redline.
Other vendors here (not mentioning them) use a straight timing curve, 23-25* straight across all rpms.
Advantages / disadvantages? Power differences? Is there a theory behind either approach?
Flat timing tables?!? Proper timing tables should be curved to reflect the power characteristics of the motor and detonation resistance of the fuel being utilized. In general, any timing table should start with relatively low timing advance at low RPM and gradually increase are RPM rises. Timing advance should also decrease as pressure increases. Hence the reason the factory tables look like they do granted the factory tables could be better.
I'd love to know who's doing this... Frankly, I guess I'm not surprised. I've seen more than a fair share of absolutely terrible tunes from various vendors here.
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Note: I am no longer offer tuning services. Please contact another vendor for tuning. I'm no longer going to compete with people who half ass things, make empty promises, and insist on flat out doing things the wrong way. I apologize for any inconvenience this may cause...
Question - stock / S2 /s3 all use a timing curve, starting from 13-14* around 2700 up to 25-26* by redline.
Other vendors here (not mentioning them) use a straight timing curve, 23-25* straight across all rpms.
Advantages / disadvantages? Power differences? Is there a theory behind either approach?
In theory, timing advance should increase as rpm increases. The amount of timing advance will depend on things such as cylinder pressures, spool (when the turbo spools and how hard/quick it spools), turbo/intercooler efficiency, type of fuel, AFR's etc.
I am currently running 18 degrees of timing advance at 2700 rpm, climbing to 24.5 degrees by 3800-4000. I could run a couple more degrees of timing advance past 5000 rpm (26 or so).
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STAGE 3 FP Green + ported head, bolt-ons
11.5 @ 128 mph (race gas with slicks) 1.97 60ft
Last edited by wonderboy : 06-01-2009 at 12:20 PM.
LOL. Figured so much. Is there a major power advantage difference? It does seem as though the motor can take a bit more timing down lower in the RPMS, but as the rpms climb the ramp rate of timing cannot continue and it it has to flatten out.
Ex. Timing from 2700 to 3500 increases +3* every 300rpms or so. As you get past 4500 timing increases 1.5* every 300 rpms.
The motor might have a knock resistance up to 24* timing advance at 3500, and the same across the board. Why not max it out at each rpm interval.
In other words, if i increased timing until I saw knock at every rpm, I will find it can resist pretty much 23-25* of timing across the board.
Thoughts?
Increasing timing will only yield increased power to a certain point. At some point you reach MBT. Increasing timing beyond this point has no additional power benefit. In many cases though, detonation will occur before you reach MBT. It's kind of one of those things where you need to dyno tune it to find optimum timing under a given load and RPM.
As piston speed increases , the initiation of the combustion event should be slightly pushed forward so that maximum combustion pressure occurs at Top Dead Center (theoretically) . Every time rpm doubles , the actual time between 20deg. TDC & actual TDC is cut in half . However the speed of the flame-front is constant , dispite piston & crank speed . Therefore combustion event should be moved forward to maintain an efficient burn as RPMs increase .
This is why timing should increase in relation to RPMs . As I understand it .
As piston speed increases , the initiation of the combustion event should be slightly pushed forward so that maximum combustion pressure occurs at Top Dead Center (theoretically) . Every time rpm doubles , the actual time between 20deg. TDC & actual TDC is cut in half . However the speed of the flame-front is constant , dispite piston & crank speed . Therefore combustion event should be moved forward to maintain an efficient burn as RPMs increase .
This is why timing should increase in relation to RPMs . As I understand it .
As piston speed increases , the initiation of the combustion event should be slightly pushed forward so that maximum combustion pressure occurs at Top Dead Center (theoretically) . Every time rpm doubles , the actual time between 20deg. TDC & actual TDC is cut in half . However the speed of the flame-front is constant , dispite piston & crank speed . Therefore combustion event should be moved forward to maintain an efficient burn as RPMs increase.
This is why timing should increase in relation to RPMs . As I understand it .
Yep, that's pretty much correct. Directionally, the timing advance should increase as rpm increases until you see knock and/or you have hit MBT. The only thing I would challenge is that peak cyl pressures should happen slightly after TDC. ( I think it's 12-15 degree ATDC IIRC)
So the next questions are:
How much timing can we add before we get knock?
Howe can we reduce the chance of knock so that we can run more timing or more boost?
Yep, that's pretty much correct. Directionally, the timing advance should increase as rpm increases until you see knock and/or you have hit MBT. The only thing I would challenge is that peak cyl pressures should happen slightly after TDC. ( I think it's 12-15 degree ATDC IIRC)
So the next questions are:
How much timing can we add before we get knock?
Howe can we reduce the chance of knock so that we can run more timing or more boost?
From what I remember, almost all engines make maximum torque with peak pressure occurring at 20 degrees ATDC. I guess that could be considered slightly after TDC though...
From what I remember, almost all engines make maximum torque with peak pressure occurring at 20 degrees ATDC. I guess that could be considered slightly after TDC though...
15 - 20.. close enough. Keep in mind that the engine's rod stroke ratio will have some impact on where peak cylinder pressure should occur.
I think you can run closer to 12-15 degrees ATDC on race fuel, but not on pump gas, since pump gas is not as stable (ie.. knock resistance) and you will get knock.
Last edited by wonderboy : 06-01-2009 at 01:09 PM.
Yeah , wonderboy , your right about actual max pressure , I was talking theoretically , and talking out my ass to an extent . Im sure its obvious to all that max combustion pressure occurs WAAAY after spark initiation .
The best way I have found to reduce Knock is to reduce intake temps (water injection or better intercooler) & run an ethanol mix , if possible .
Fantastic stuff guys, makes perfect sense. I guess the best approach would be to work off the MBT table, back off universally from there to get a good WOT table. I think I might take the MBT timing amounts and take 10* off those, and use that ramp rate. That should put at about 18* around spool up and about 26* at redline.
Yeah , wonderboy , your right about actual max pressure , I was talking theoretically , and talking out my ass to an extent . Im sure its obvious to all that max combustion pressure occurs WAAAY after spark initiation .
The best way I have found to reduce Knock is to reduce intake temps (water injection or better intercooler) & run an ethanol mix , if possible .
No problem... I was just pointing out that there is no mechanical leverage with max combustion pressure at TDC (since the rod would be completely straight.. and in line with the it's respective crank throw)
Last edited by wonderboy : 06-01-2009 at 01:24 PM.
15 - 20.. close enough. Keep in mind that the engine's rod stroke ratio will have some impact on where peak cylinder pressure should occur.
I think you can run closer to 12-15 degrees ATDC on race fuel, but not on pump gas, since pump gas is not as stable (ie.. knock resistance) and you will get knock.
You'd want peak pressure to occur at the specific point where maximum torque is produced regardless of the fuel used; exceeding that point only increases cylinder pressure/temperature and provides no gain.
Obviously, with pump gas, peak pressure will occur far after the ideal crank angle for maximum torque due to (as you noted) it's likelihood to detonate.
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WOT Timing---curve or flat line?
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