Ignition Timing on DI Engines

Discussion of tuning specific to MAZDASPEED6/MAZDASPEED Atenza/Mazda 6 MPS vehicles
Lolmooses
Posts: 43
Joined: June 16th, 2020, 1:53 pm

Ignition Timing on DI Engines

Post by Lolmooses »

Is there a different approach to take when tuning a DI like the MZR compared to a regular PI engine? Is there a reason other than safety as to why Mazda would put in so much negative timing at low RPM high load? I've currently set any negative timing before 3000 RPM and below 2.25 load at 0 to see if anything changes and I can't say I've noticed any KR or performance difference (hard to measure without a dyno though obviously). I can see DI engines not needing as much advance due to the fuel getting into the combustion chamber quicker than PI engines, but the stock negative timing seems excessive.
2006 MS6: CS HPFP internals, stage 2 CS intake, CP-E TMIC, CS catback with racepipe, GFB hybrid BOV, CS EBCS
mituc
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Re: Ignition Timing on DI Engines

Post by mituc »

Remember a lot of timing and AFR values are there for emissions, not necessarily for operating the engine safely.
Based on the AFR and timing the exhaust gasses are supposed to have a specific content easier for the catalytic converters to munch.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
Lolmooses
Posts: 43
Joined: June 16th, 2020, 1:53 pm

Re: Ignition Timing on DI Engines

Post by Lolmooses »

I forgot about emissions, you're right. So it's primarily emissions and safety. How has your experience been adjusting the ignition timing curve on a k04 on pump gas? I'm currently targeting 0* at spool up and working my way up from there until 12* at 6500.
2006 MS6: CS HPFP internals, stage 2 CS intake, CP-E TMIC, CS catback with racepipe, GFB hybrid BOV, CS EBCS
mituc
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Re: Ignition Timing on DI Engines

Post by mituc »

Pump gas what what octane, or RON?
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
Lolmooses
Posts: 43
Joined: June 16th, 2020, 1:53 pm

Re: Ignition Timing on DI Engines

Post by Lolmooses »

93 OCT with 10% ethanol depending on the gas station I believe.
2006 MS6: CS HPFP internals, stage 2 CS intake, CP-E TMIC, CS catback with racepipe, GFB hybrid BOV, CS EBCS
mituc
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Joined: December 17th, 2011, 2:47 pm
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Re: Ignition Timing on DI Engines

Post by mituc »

I'd start with the timing tables from an OTS map and then work the way up to like 10-12 degrees at 6500rpm, 9-11 degrees at 6000rpm, 7.5-8 degrees at 5500, 6-7 at 5000, 5.5-6 at 4500, 4.5 at 4000, and like 2.5-3 degrees at 3000rpm. This should work on whatever the load curve over an entire pull will look like, it's fairly ok and on the conservative side for 93OCT/98RON for stock turbo but it depends on how much heat you're pushing into the engine which is in direct relation to boost on these tiny turbos. for the timing curve above I have in mind load values of like 2.2-2.3 in the mid range and like 1.8-1.9 at 6000rpm which is beyond the factory turbo capabilities in all-weather conditions. So you can start with that and work your way up depending on how the car is running and how the gas is resisting to cylinder heat.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
Lolmooses
Posts: 43
Joined: June 16th, 2020, 1:53 pm

Re: Ignition Timing on DI Engines

Post by Lolmooses »

That ignition curve is pretty much exactly where I'm at but at 2.0 load. BATs are at 100+*F sometimes over 110*F during a pull and I'm starting to see a degree of knock during pulls so I'm waiting on an upgraded TMIC before I target any higher loads.

Would a max limit of 1.9-2.0 at 2500 be safe for the stock rods? I've read of people going as high as 2.2 on a stock block with no issues, but I'm skeptical.
2006 MS6: CS HPFP internals, stage 2 CS intake, CP-E TMIC, CS catback with racepipe, GFB hybrid BOV, CS EBCS
mituc
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Re: Ignition Timing on DI Engines

Post by mituc »

At 2500rpm I wouldn't up load past like 1.6 or so. I didn't even mention 2500rpm because talking about performance tuning at that RPM is a totally waste of time. At that RPM I'd tune for efficiency only, for performance 3500-4000+.
I went as high as load 2.4 on a stock block but ABOVE 4000rpm. On my CX7 I turned it down to 2.2 again though because the factory flywheel is on its way out (not that the aggressive driving I'm doing with that house on wheels helps too much though). On my 3MPS when it had a stock block ringlands eventually gave up from targeting load in the 2.35-2.4 range + around 2-ish at 6500rpm with a rev limit at 7k (which I think got the ringlands eventually).
So again, I'm not mentioning anything about 2500rpm. high load there is rod snapping, guaranteed (even 3000rpm is a bit too low especially with a fast spooling turbo).
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
Lolmooses
Posts: 43
Joined: June 16th, 2020, 1:53 pm

Re: Ignition Timing on DI Engines

Post by Lolmooses »

Thanks for confirming what I was skeptical about hahaha. High load at 2500 rpm on a stock block just sounded like a horrible idea. I'm guessing too that once you upgrade to any larger turbo there's nothing at 2500 RPM anyways which essentially makes that rpm useless for performance like you said.

You mention targeting 2.4 load on a bigger turbo, what I'm wondering is since load is a measure of how much air is getting into the engine, would I be correct in thinking 2.4 load on two different sized turbos (one being bigger than the other) equates to the same power output provided all other variables (timing, ambient conditions, fueling, etc) are similar?
2006 MS6: CS HPFP internals, stage 2 CS intake, CP-E TMIC, CS catback with racepipe, GFB hybrid BOV, CS EBCS
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Ignition Timing on DI Engines

Post by mituc »

Lolmooses wrote: June 26th, 2020, 11:34 pm I'm guessing too that once you upgrade to any larger turbo there's nothing at 2500 RPM anyways which essentially makes that rpm useless for performance like you said.
Not necessarily. On a GTX3071 (gen1) I can get load 2.1 at 2000rpm in 6th :) I think by 2200rpm that can be a lot more load. Ofc that is on my 3MPS which has a forged engine, stock internals will not tolerate that too many times.
Lolmooses wrote: June 26th, 2020, 11:34 pm You mention targeting 2.4 load on a bigger turbo, what I'm wondering is since load is a measure of how much air is getting into the engine, would I be correct in thinking 2.4 load on two different sized turbos (one being bigger than the other) equates to the same power output provided all other variables (timing, ambient conditions, fueling, etc) are similar?
Same timing, same, amount of air and enough fuel to burn that air and about the same starting cylinder temperature will result in the same amount of mechanical work. The turbo is just an air pump, a tool to get air into the engine to make torque. Once it's on the engine the power output will not depend on the turbo any more.

However, there are at least two things I can think of here:
1. the more relaxed the turbo (usually that translates to "larger" but not necessarily, let's just say "more efficient") the lower the temperature of the compressed air will be. That can play a role in ignition timing and knock control if the timing curve is on the edge of detonation;
2. past a power threshold, meaning past a certain amount of exhaust gasses the charger wheel of the turbo can become a restriction if it's too small or doesn't spin fast enough. That can increase the exhaust pressure which will increase also the pumping effort of the engine which obviously will result into loss of power. But below that threshold... Load + timing at the same state of health for the engine (compression, leak, and so on) = the same power.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
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