Inducing Open Loop Earlier

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

Inducing Open Loop Earlier

Post by Lolmooses »

Hello, I've been trying to dial in my MAF calibration and I'm running into issues where at the same MAF voltage (let's say 3.8v for example) on one pull it'll already be in open loop by the time it hits that MAF voltage and the AFR's are where I want it, but in pulls where I go WOT a little later, it's still in closed loop at 3.8v and the actual AFR is at 13.8 when it desires 12.6 during a load of 1.5. I never experience any knock because of that, so perhaps I'm just used to PI cars, but it's concerning. Ideally I'd like to transition to open loop at any load above 1.5 and APP at 75%. What would be the most reasonable way to do this? I see there are quite a few tables concerning close loop limits and I have an idea of what to try, but I'm curious to know what more experienced users have done.
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: Inducing Open Loop Earlier

Post by mituc »

The Closed Loop/Open Loop transitioning tables are responsible for when the transitioning is done and and the Closed Loop Load Limit tables for how much the fuel trims mechanism will still work.
The later are responsible for various corrections even in open loop if the load values there are set high enough, and this is the factory approach as well as preferred by some tuners.
Personally past 3000rpm I set everything to open loop at loads higher than 1.1-1.2.
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
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Joined: June 16th, 2020, 1:53 pm

Re: Inducing Open Loop Earlier

Post by Lolmooses »

Is the factory preferred by some tuners because of smoother transitioning and therefore smoother drivability? Did you notice any harshness from getting rid of that method?
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: Inducing Open Loop Earlier

Post by mituc »

Lolmooses wrote: June 18th, 2020, 11:25 pm Is the factory preferred by some tuners because of smoother transitioning and therefore smoother drivability? Did you notice any harshness from getting rid of that method?
It is preferred because the ECU will still compensate if some hose blows up by example, or in the regions where the fuel additive packages differ from season to season, gas station to gas station, and so on, the ECU will adapt for those sometimes significant variations in oxygenated additives.

No harshness going true open loop avoce certain loads. But you have to have your MAF cal on point, if you use WMI make sure you mix the alcohol and water exactly the same all the time, and so on.
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: Inducing Open Loop Earlier

Post by Lolmooses »

I see, so if I wanted to keep it using the OEM strategy, am I on the right track in thinking that making the closed loop desired AFR table values richer and then adjusting my MAF calibration to meet those desired values would be a reasonable method of running a little richer in CL for safety?
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: Inducing Open Loop Earlier

Post by mituc »

The CL-OL-CL switching has multiple triggers: load, APP and sometimes RPM (by example on the CX7 they exit CL at 5000rpm, some CL tables don't even have entries above that RPM because of that).
The CL-OL switching is often (and mistakenly) attributed to the Closed Loop Load Limit tables which as far as I know they only have effect on the fuel trims logic, more specifically the fuel trims strategy is extended up to that load.

I'm saying this because I don't know what you actually want to do: keep the fuel trims correction strategy as much as you can or you actually want to switch to open loop at certain points (APP with the Closed Loop Open Loop APP threshold tables, and load using the Closed Loop Open Loop Load threshold tables)?

Other than that the CL and OL tables are used accordingly. If you switch the CL-OL transition thresholds, the same load, RPM, AFR, timing and intake timing advance will have the same effect within the cylinder, so you may want to keep those overlapping regions of the CL and OL tables for the same thing (AFR, Timing) in sync.
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: Inducing Open Loop Earlier

Post by Lolmooses »

At first yes I just wanted to induce OL at a certain point but after you explained things a bit I'm considering another strategy. To clarify I'm thinking of changing the values in the closed loop AFR table to target richer AFR's at let's say 1.3-1.6 load where it's currently targeting in the 13's and adjusting the MAF calibration accordingly. Perhaps I'm just overthinking it since it never actually knocks on spool up, probably because it's running negative timing at those lower loads. Does the negative timing serve another purpose or is it there purely for safety?
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: Inducing Open Loop Earlier

Post by mituc »

Lolmooses wrote: June 20th, 2020, 3:22 pm At first yes I just wanted to induce OL at a certain point but after you explained things a bit I'm considering another strategy. To clarify I'm thinking of changing the values in the closed loop AFR table to target richer AFR's at let's say 1.3-1.6 load where it's currently targeting in the 13's and adjusting the MAF calibration accordingly.
I'd rather have the MAF cal on point and target specific AFRs rather than adjusting the MAF cal to match some AFR values you have in mind.
Lolmooses wrote: June 20th, 2020, 3:22 pm Perhaps I'm just overthinking it since it never actually knocks on spool up, probably because it's running negative timing at those lower loads. Does the negative timing serve another purpose or is it there purely for safety?
Those negative timing values are both for spool up and protection. However IMHO they area bit too much on the negative side, even with a larger turbo the spool-up isn't bad at all with slightly higher timing and only if necessary lower AFRs, like 11.2-11.5 in the 3000rpm area. Some people go as low as 10.8 but that will result into puffs of black smoke which personally I dislike.
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: Inducing Open Loop Earlier

Post by Lolmooses »

Based on what I've been seeing so far, I'm having certain MAF voltages where if it's in OL the AFR matches desired very well, but the same MAF voltage in CL is off from the fuel trims trying to adjust which I'm assuming requires changing the MAF cal, thusly messing up how well it matches in OL. I'm thinking that this balancing act is more of a headache than it's worth, so I see what you mean. I'd rather have a MAF cal that gives me what I want consistently.

I agree, it's a bit too negative and I don't see a couple degrees affecting spool that badly. I'd imagine the EGT increase from negative timing isn't worth it.
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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Posts: 1324
Joined: December 17th, 2011, 2:47 pm
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Re: Inducing Open Loop Earlier

Post by mituc »

Lolmooses wrote: June 21st, 2020, 1:03 am Based on what I've been seeing so far, I'm having certain MAF voltages where if it's in OL the AFR matches desired very well, but the same MAF voltage in CL is off from the fuel trims trying to adjust which I'm assuming requires changing the MAF cal,
In your logs log both desired and actual AFR. That way you will see if the richer AFRs aren't somehow subject of fuel enrichment commanded by the ECU. If the desired matches the actual in the same line or at least next means your MAF cal is ok.
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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