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Discussion Starter #1 (Edited)
With a little hope and planning I'll be getting a tune on my car next year during the dog days of summer to make sure it is an all weather tune, so I figured I could start documenting what could or should be done as part of the tune to make things better for my car. So I'm taking this thread more as a blog people are welcome to follow me on and provide comments on, moreso than a discussion. ***UPDATE: OrangeVirus Tuning has offered me a free tune in response for a thorough review of their business and their tune product. This will likely happen in January (2015)***

I think getting a tune and even experimenting with a tune isn't so dangerous because of the highly sensetive knock sensor and Safe Mode that will remain untouched by the tune. So if the tuner or myself does anything idiotic that would cause the engine to predetonate itself to death the knock sensor will pick it up, and shift from the screwed up tune map to the safe mode map before too much if any damage is done. I believe the tune can even change the thresholds to add an extra layer of safety.

Objectives of Tune:
  1. Eliminate touchy throttle pedal at light throttle application as a result of using 91 Octane
  2. Improve fuel economy at light-medium throttle load including up to 85mph worth of RPM ((3k with my MTX) in 6th gear only
  3. Eliminate tendency for knock at 2500-3500rpm with medium to high load after installation of high flow muffler
  4. Eliminate major dip in torque band from 3500-4300rpm which was exaggerated by the high flow muffler
  5. Maximize performance of SRI, which shortened the intake length and subsequently reduced intake air column momentum
  6. Maximize combustion chamber pressure at top dead center for 50% load and up at all RPMs (i.e. run full otto cycle 13:1 compression ratio), fuel economy be darned
  7. Maximize spark timing for 50% load and higher where they ECU is not doing it automatically, fuel economy be darned
  8. Give the engine a higher redline so I'm not running into it all the time and the car can be a bit higher RPM going into the next gear.
  9. Eliminate the car from pulling back timing on hard shifts (mostly 1-2 shifts)
  10. Increase torque below 3K RPM at 50% throttle or more, fuel economy be darned.
  11. Eliminate the funny business when letting the clutch out in first and second gear (after clutch is let out completely the ecu dials back the power),
  12. Eliminate atkinson cycle in 1st gear for all loads and RPMs.
  13. Prevent Exhaust Gas re-circulation from putting carbon on the intake valves or creating knock due to introducing heat and junk in the combustion chamber.
Tune Changes to Meet Objectives:


1. Since the ECU and knock sensor will advance the spark as far as it can go, which on 91 is far enough throttle response is too much for initial throttle touch, then the simplest way to dial back the spark and power is to pull back some fuel at 0-10% load so the engine runs a little more lean so it encounters knock a little sooner and pulls back the timing a bit. Also less fuel is less energy, so I would think a small change in fuel would go a long ways and not require adjustment to airflow to compensate which makes this change simple, and may increase fuel economy.

2. Similar to #1 to some extent, reduce the fuel a very tiny amount above say 200RPM to run more lean, but this may not be worth much or could even be negative for fuel economy if it pulls back spark to the point it is less efficient requiring more throttle and fuel to compensate (Self defeating). I'm not expecting much here, but the safest thing may be to leave fuel alone above 2k. From 2k up to 3k in 6th gear (each gear has it's own set of maps) which is equal to 85mph, ensure that at less than say 30-40% load the engine should be forced to stay in atkinson cycle mode/ on a non aggressive cam and A/F ratio

3. This may be the tougher nut to crack, as I'm not sure the muffler is really creating a problem as much at is simply allowing the engine to generate more torque, which per some mazda tech info they simply plot a peak possible torque at a given compression ratio (and octane) as an upper bound for knock resistance (i.e. more torque equals more knock if compression ratio and octane remain the same). Still, I think the potential here is to advance or more likely retard the timing of the exhaust valves a bit (following adjustment of the intake valve) to see if evacuation of the cylinder can be improved, if it is really a case of the reduced backpressure of the exhaust allows the air to be scavenged too quickly and bouncing back into the chamber with the air pulse, while not hurting the benefit of the overlap with the intake valve on the exhaust stroke, impacting effectiveness of the end of the power stroke, and suction at the beginning of the intake stroke.

4. I'm frankly not sure what timing is causing this and it seems to be worse in the lower 2 gear and almost non-exstent in the higher gears), but I'm most frequently accelearting hardest in the lowest two gears so it bothers me a lot. Hopefully peeking at the stock tables will shed some light on what is happenig to spark timing, intake valve timing, and exhaust valve timing from 3k-4.5k in gears 2 and 3 to see if there is something Mazda was trying to compensate for knock or what. If not then it will be trial and error trying to get rid of this

5. The fix here is pretty obvious it just a matter of how much is just right. The SRI shortens the intake length by almost half over stock if you take into account the width of the hood the intake air is ducted through. This is a big deal for several reasons, at all RPMs any time the intake valve is closing late that timing is based on the assumption the momentum of the intake column of air is reacting the compression of air in the chamber during the initial part of the compression stroke, called the Ram Effect. So with the SRI there is less momentum than stock timing is set for. So Atkinson cycle is even more atkinson cycle with an SRI, since the late closer will let even more air bleed back out of the chamber since the momentum of the intake aire is less, which may be a good thing for fuel economy, who knows. This is the reason CAI's make better torque (i.e. more power at lower RPMs), because the Ram Effect is still compatible with the stock tuning, whereas with the SRI the stock tune is closing the intake valve too late giving back some compression. When the late intake valve closer on the compression stroke is for performance the same error is going on, which means the real world compression ratio is less than it should be, so by advancing the intake timing under high load so the intake valve closes earlier in the compression stroke will increase the amount of air shoved into the combustion chamber for a higher pressure at top dead center. At high rpms (5k and up) you can see from dyno plots the lower momentum of the intake air becomes a big advantage to the SRI even with the stock tune, which means it is likely that earlier closer of the intake valve will result in greater peak horsepower. So the expectation is that with a cold air box and a proper tune, the SRI will make more power and torque at all RPMs than a CAI.

6. As TickerGuy said the stock tune is to ensure compliance with emission requirements at all cost and similarly even fuel economy, so it is expected that we are not running a true 13:1 compression ratio at WOT on 87 octane, it may be pulling back a little to an atkinson cycle to avoid knock. But if you are willing to run 91 octane or higher, with a cold air box, and if still necessary dump in extra fuel and run a little rich then it likely is possible to run at maximum air mass into the combustion chamber with no bleed out via advanced intake timing closing the intake valve sooner than stock on the compression stroke. This means more available fuel for combustion, and because this also increases the true compression ratio, the efficiency of combustion is increased for better fuel economy and more power.

7. After intake and exhaust timing is sorted out and the powerband has been smoothed, and fuel delivery increased to run somewhat rich, then advance the spark timing for high load and max timing tables up to the point of knock in 90degree plu sweather, but not at the expense of an uneven power band and torque band accross the rpm range

8. Easiest to do, change the current value of 6200 rpms to 6500 rpms and walla, new higher redline and all the speed benefits and engine internals durability risks that come with it! I think 300 RPMs isn't a big difference and if you look at the tach, true redline isn't until 6500 anyways, so I'll trust the tach guys got together with the engineer guys to determine that 6500 is the limit you'd really want to go to. Or maybe not... LoL.

9. Disable or reduce "spark smoothing" that is causing the car to pull back timing on hard shifts if it is possible with Mazdaedit tuning software. May not be possible...or maybe mazda already fixed it with the latest tune, as ballsy can spin his tires on a 1-2 shift, which I cannot do...I need to get an ECU reflash prior to custom tuning for sure.

10. Not sure why there is such a big ramp in torque from 2k to 3k. It's way beyond the natural torque profile of an engine, so I think that it is likely revising intake and exhaust timing below 3k under high and max load will improve that. It would be great to stomp on the gas at 2200 rpm and feel some push into the seat, rather than it slowly building, making you resent not downshifting.

11. I'm not sure what is going on exactly, but clearly the ECU knows when I'm letting the clutch out, because right after I completely let the clutch out the acceleration decreases noticeably, like when I was experiencing bad knock and the car was pulling back timing. The ecu is programmed to give more power to be strong when letting out the clutch, but once the clutch is out acceleration is sluggish. It's obvious if I ride the clutch a little in 2nd at 1k RPM the car starts to buck as it cycles back and forth between adding power and taking it away. The end result is a two step throttle application (one amount to let out the clutch then more after the power is dialed back) which is annoying, giving a bobble head affect to everybody in the car. If possible whatever compensation setting in the ECU is doing this needs to be killed. I can modulate the gas and clutch pedals just fine without it's help.

12. How much fuel is really saved by being in Atkinson cycle in 1st gear which realistically is only used for acceleration (moderate and higher loads) and for a very short time, especially with how short first gear is? So advance the intake valve timing to run Otto Cycle from idle to redline at all loads in 1st gear.

13. Set EGR valve to closed almost all the time. Only have it function enough to keep the valve working properly. It's easier than adding an EGR block off plate. I'm a pretty green guy with a strong appreciation for catalytic converters, but I have no remorse for doing this. EGR always struck me as grasping at straws. My super efficient mazda 6 that is CARB illegal will still have fabulous emissions compared to a 15 year old car or a brand new full size pickup that are both still considered CARB legal.

References:
  1. Valve Timing for mild racing cam, and intake and exhaust overlap explained: http://www.iskycams.com/degreeing.php
  2. Another take on Valve timing with some explanations of what can happen if timing is too early or too late: http://www.compcams.com/Pages/416/valve-timing-tutorial.aspx
  3. Description of Variable Valve Timing: http://enginebuildermag.com/2014/01/the-inner-workings-of-variable-valve-timing/
  4. SAE Skyactiv article. Some description of cam timing and other related discussion: http://articles.sae.org/10335/
  5. More skyactiv timing discussion and thorough breakdown of mechanical bits. http://www.motoiq.com/MagazineArticles/ID/2105/131-Compression-and-40-mpg-on-87-Octane-fuel-Introducing-Mazdas-Skyactiv-Technology.aspx
 

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following along!
Everything you've got there looks pretty good as far as goals/plans. I would also see how far you can push the intake timing to see about more duration and some overlap. The problem there, and where I see the most risk for failure.. if there isn't enough clearance at TDC for the larger valve opening at peak for the cam... Surely not though since it's not a bigger lobe, just at a different time? o_O That aside, I believe you're safe taking some risks. The CX7 and mazda speed crew sure did early on, just to find out they get audible "KNOCK" warnings and timing pulled by the ECU, lol.
 

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Discussion Starter #4 (Edited)
I would also see how far you can push the intake timing to see about more duration and some overlap. The problem there, and where I see the most risk for failure.. if there isn't enough clearance at TDC for the larger valve opening at peak for the cam... Surely not though since it's not a bigger lobe, just at a different time? o_O That aside, I believe you're safe taking some risks. The CX7 and mazda speed crew sure did early on, just to find out they get audible "KNOCK" warnings and timing pulled by the ECU, lol.
:yesnod: Advancing Intake valve timing will be the solution to objectives 5 and 6. It will kill 2 birds with one stone for hopefully an eyebrow raising increase in hp. You can't vary the duration though, that is part of the physical cam profile.

Does anybody know if this is a clearance motor? I wouldn't be suprised if it is, the pistons are somewhat shaped for that with large chamfers on the sides. The service manual should say something about it for timing chain service, head replacement or valvetrain work tasks. Maybe somebody with enough time can do some digging.

Between early opening during the exhaust stroke that keeps the intake valves clean per the mazda engineers statements and the atkinson cycle that leaves the intake valves open really late the intake valves may have very large duration, and the intake valve timing is an electric phaser with 70 degrees of range, it would be prudent to make it a clearance engine.

The engine runs suprisingly lean for 13:1 compression ratio, even more so with the airflow mods. My cold air box had eliminated any knock even on 87 octane at nearly 100 degrees ambient, so I'm hopeful that between 91 octane and running rich I can succeed in running full otto cycle and advancing the spark a bunch too. I still have that nomex laying around I can wrap the entire intake system with as well.

I spent months with my car tripping into safe mode on a daily basis, so I'm pretty confident it will keep knock related timing issues in check
 

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Discussion Starter #6
When this is all done in a year, I think I will do a dyno run and pay for somebody with a bone stock 20104/2015 6 MTX to run with me on the same dyno the same day as a control to set the losses relative to crank numbers. That will provide a good quantification of the sum total of all the changes to convert them to crank values for proper perspective.

A year is a long way off so no promises here, but a bit of hope.
 

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Sorry, I couldnt think of a way to word it. With the huge range of timing and the ability to move the intake came so much you can simulate the valve operation that a larger duration normally gives, but without pushing the valve further into the chamber. It would be limited to how fast the system can make those changes if it could be achieved across the board for all 4 cylinders though... just a thought.

But yes, I agree by far, that intake variation is the key to making more power from this car. I mean.. look at the gains some of Honda VTEC swaps make... 30-40HP.. bump in compression and tuning timing and lift. If that an indication of what's to be had on our platform from running the higher compression more often and bumping the timing advance and intake timing... *drool*. 230HP.. soo 210WHP? that's a bit more "fun". But, as we've always talked about, I'm more interested in the gains BEFORE the stock tune bumps up at 3,000+ :D. Sounds like that's one of the major goals though.

As for clearance, the mazda skyactiv breakdown use to show the piston to valve relationship, and it does appear clearanced for the valves. The question is, how much? Typically it would be 0.1+ for an OEM application, but is that 0.1 at mazda spec tune, or at TDC with maximum valve opening. You can safely run down to 0.50 and less, but then you're getting into risky waters. I'm at about 0.05-0.06 (it's been awhile and I've forgotten which it was, but it was tight, lol) PtV with my formula's new top end, but it's not a daily... no way I would run it that close on a daily driver, lol.
 

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Discussion Starter #9

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Discussion Starter #10
Sorry, I couldnt think of a way to word it. With the huge range of timing and the ability to move the intake came so much you can simulate the valve operation that a larger duration normally gives, but without pushing the valve further into the chamber. It would be limited to how fast the system can make those changes if it could be achieved across the board for all 4 cylinders though... just a thought.
I don't think VVT is working within a single revolution of the cam, I think it is working to change angles over time, many revoltions to advance or retard the camshaft. With the new expensive electronic phase maybe I'm wrong. It would be obvious in the tuning parameters if it gave both a valve opening and valve closing set of time tables, instead of a single table.
 

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Discussion Starter #11
But, as we've always talked about, I'm more interested in the gains BEFORE the stock tune bumps up at 3,000+ :D. Sounds like that's one of the major goals though.
.
Oops I actually forgot to add that explicitly. Added as objective #10 . Thats quite a few objectives!
 

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Discussion Starter #12
Just bumping this thread since I've added a lot more info to the opening post.
 

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Discussion Starter #13

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Discussion Starter #16 (Edited)
I guess I should update this thread since I left it hanging. I've currently got the 4th iteration of the tune flashed and logged. We may play with exhaust timing a bit more for WOT as a science project since my exhaust seems to have made things so different than what other people have experienced.
 
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