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Discussion Starter · #1 ·
Ok, this might sound like a fantasy that makes no sense, but my knowledge of how the skyactive engines work (maybe even engines overall) is a bit limited, so I thought I would ask the experts here the question.
So, tuning skyactive engines is considered 'stupid' and a waste of time, as they have a compression ratio of 12:1 factory.
Not considering the funding, would it somehow be possible to increase the cylinder size, thus in turn decreasing the compression ratio of the engine itself, to then again add power in the form of turbocharger or supercharger to possibly gain more horsepower than it would with the factory set up?
I'm new here, so please go easy on me 馃槄
 

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A more reasonable approach would be to find a decompression piston where it has a hole or a divot in the middle so it allows less of the air to be compressed and that would be lowering the compression ratio or you would port the combustion chamber in the head and that would also lower compression ratio boring out an engine doesn't necessarily lower compression.

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Discussion Starter · #3 ·
I didn't necessarily mean boring out the engine to get the increased chamber space, a decompression piston would work just as well.
I was just thinking if it's physically possible to somehow decrease the factory compression ratio to then in turn add aftermarket parts that bring more horsepower than the engine naturally would?
 

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The quickest and easiest way to lower the compression ratio is to put a thicker head gasket in. The two problems with that are:

1) Finding a thicker head gasket.
2) Doing this may change can timing or maybe make the timing chain not fit any more.

Those two things may end up making this not the simplest strategy. (-:

In a basic, theoretical way, the answer is yes. If you lower the mechanical compression ratio (and thus lower cylinder pressure), you can then add forced induction. That forced induction puts cylinder pressure back up, but with more O2 in there to burn, so more power.

Lower compression ratios reduce thermal efficiency (fuel economy).
 

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Considering we're getting (US trim) 184hp out of 2.5 liters with 16v, balance shafts, variable valve timing, and all kinds of goodies, it seems obvious this engine has made a LOT of compromises for fuel economy, emissions, and other efficiencies.

Maximizing horsepower was not a high priority (though they did okay on torque).

All said and done, the Mazda6 is damn good at what it tries to do - within its price and quality class.

Too many people on this forum want this car to be something it isn't. It's not a performance car and efforts to make it one aren't going to be productive. For the money you'd spend, choose a higher performance, different car. Zoom-zoom!
 

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IMO it is not worth it to think about altering compression or anything like that. These are some impressively engineered engines...
BUT there are some ways to get more power without going to that extreme/risk.
1) TUNE - tuning for premium fuel on these motors adds a TON of power - over 25hp/tq and loads of torque gain under the curve
2) Air flow - on top of the tune improving the exhaust and intake flow will help as well, especially if you do both and get tuned, but don't expected huge changes especially to peak power.

For reference, when I bought my car in late 2017 the best 0-60 I could pull (with obd reader on Torque app) was 7.6 seconds, but after tune it dropped to 6.8 seconds (and after further mods and lightweight wheels I'm down to 6.3 seconds consistently). What's more the straight line speed under represents how fast the car feels, on the track it is surprisingly fast because the power band is SO wide.
 

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...
All said and done, the Mazda6 is damn good at what it tries to do - within its price and quality class.

Too many people on this forum want this car to be something it isn't. It's not a performance car and efforts to make it one aren't going to be productive. For the money you'd spend, choose a higher performance, different car. Zoom-zoom!
I agree this is a damn good car for the constraints it's operating within!
For me, I needed to get a mid-size family sedan and wanted the most fun/sportiest one.
I really liked the power of the V6 Camry or the 4T Accord, BUT they just could not compare to the FEELING of the Mazda!

So... I've been working to intelligently improve the quickness of my 6 (within realistic expectations), and am so happy with the result (regularly get asked at racing events "what V6 did you swap into your Mazda")

The fact remains, if you really want big speed/power you should buy something else as this is only "sporty" for a mid-size sedan, and really fuel efficient.
 

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Dan, do you have a thread or something to describe the tuning process, with all the details and your long-term satisfaction with it? I have thought about it, but it's my family car and I need it to be reliable, and I need my better half to be happy with it too.
 

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IMO it is not worth it to think about altering compression or anything like that. These are some impressively engineered engines...
BUT there are some ways to get more power without going to that extreme/risk.
1) TUNE - tuning for premium fuel on these motors adds a TON of power - over 25hp/tq and loads of torque gain under the curve
2) Air flow - on top of the tune improving the exhaust and intake flow will help as well, especially if you do both and get tuned, but don't expected huge changes especially to peak power.

For reference, when I bought my car in late 2017 the best 0-60 I could pull (with obd reader on Torque app) was 7.6 seconds, but after tune it dropped to 6.8 seconds (and after further mods and lightweight wheels I'm down to 6.3 seconds consistently). What's more the straight line speed under represents how fast the car feels, on the track it is surprisingly fast because the power band is SO wide.
I'm sorry, I just don't believe the 6.3 sec 0-60 for this car. That's faster than the turbo version. Stock is about 7.9. If you have a time slip to show, please do. Otherwise I think it's BS. You don't get those kinds of gains from a tune.
 

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I'm sorry, I just don't believe the 6.3 sec 0-60 for this car. That's faster than the turbo version. Stock is about 7.9. If you have a time slip to show, please do. Otherwise I think it's BS. You don't get those kinds of gains from a tune.
Yea, its possible. The turbo version is tuned for midrange/passing power, not off the line power.
 

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Yea, its possible. The turbo version is tuned for midrange/passing power, not off the line power.
If there are slips somewhere of non-turbo 6's pulling these numbers I'm happy to be wrong.
 
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I'm sorry, I just don't believe the 6.3 sec 0-60 for this car. That's faster than the turbo version. Stock is about 7.9. If you have a time slip to show, please do. Otherwise I think it's BS. You don't get those kinds of gains from a tune.
I appreciate your skepticism ;). I've done everything I can think of to make my car quicker... Couple of points to clarify:
1) The Turbo 6 0-60 is traction limited (that's why awd CX5 is faster)
2) The tune only got me down to 6.8 sec 0-60 (on 92 octane fuel, with Injen CAI and high flow exhaust)
3) To get down to 6.3 sec:
a. got new set of ultra-light wheels (17" Traklites, 10lbs less rotating mass per wheel), makes a huge difference below 40mph (wider 8.5" rim with 235 tires)​
b. got new extra high octane, power focused tune revision for 95 octane (using ~2oz of Boostane per tank)​
c. my 2016 6 only weighs about 3200lbs, whereas a newer turbo 6 weighs about 400lbs more, @6hp/100lbs that's 24HP handicap from extra weight​

A friend has dyno'd his tuned 6 at 198HP at the wheels, I figure the extra high octane tune nets a few extra and the reduced rotating mass eqauls a few extra HP, so I'd estimate equivalent to ~210-215HP at the wheels (though the benefit of reducing rotating mass is greatest at slower speeds)

*Also because my wheels are 1% smaller diameter than stock that is a slight difference, so you could round up to 6.4 seconds

In an 1/8 mile I'm confident I could beat a turbo 6, but in 1/4 mile it would be very close.
 

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I'm sorry, I just don't believe the 6.3 sec 0-60 for this car. That's faster than the turbo version. Stock is about 7.9. If you have a time slip to show, please do. Otherwise I think it's BS. You don't get those kinds of gains from a tune.
7.0-7.2 seconds but Car & Driver gets better numbers usually.

 

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I'm sorry, I just don't believe the 6.3 sec 0-60 for this car. That's faster than the turbo version. Stock is about 7.9. If you have a time slip to show, please do. Otherwise I think it's BS. You don't get those kinds of gains from a tune.
Just as another data point, I have also OVTuned for 91 Octane in California (2014 Mazda6 GT). With Falken FK510 summer tires on, <70F ambient, and no wheel spin, I can reliably get 6.7s-6.9s 0-60 as measured directly from ECU.
 

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16.3 @84mph is the fastest my 6 ran in the 1/4mile pre tune. I haven't gone back since I gotten it tuned.


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Just as another data point, I have also OVTuned for 91 Octane in California (2014 Mazda6 GT). With Falken FK510 summer tires on, <70F ambient, and no wheel spin, I can reliably get 6.7s-6.9s 0-60 as measured directly from ECU.
EXACTLY, my first tune I was running in the high 6.7-6.9s 0-60

During quarantine I've installed full coil-overs, rear camber arms, Progress RSB, slightly stiffened the FSB.
Then I wanted even more quickness so I did two things:
1) Increase Octane - Heard that a partial e85 tune can make more, so I worked with OVT/Rafa to get a new tune while running ~96 octane (~2oz Boostane per 10gal premium fuel, about $3 per tank), because our engines are such high compression there is more room to tune for more power with higher octane.
2) Reduce Rotating Weight - shopped around for the best deal I could find on ultra-light wheels. I ended up getting 17" Motegi Traklites, shaving 10lbs of ROTATING MASS per wheel (40lbs total) compared to the stock 19s
From what I've read each 1lb of wheel weight eqauls 1HP, so theoretically that added 10HP.​

I actually think once I get my final higher ocane tune revisions and a good opportunity to do it on better surface I can hit 6.2 or even 6.1, BUT that's not what I care about, I'm focused on real world speed.
The best part about this car is how wide the power band is, and INSTANT response. My goal is for Autocross, and maybe some track days eventually.

Here's a run from the first event I've gotten to run the extra high octane tune with the ultra-light wheels, and WOW it is FAST. I was running times competitive with GTIs (actually I beat more than half of them), I even beat both EVO Xs that were there :)
 

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The carriage can always go faster than the horse, but you can only whip the horse so hard.

Get a different car if you want a performance car. Unless you wanna do an LS swap. lol A company in CO tunes Miatas with a 550 hp V8 shoehorned into a stock(ish) chassis.
 

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Here's a run from the first event I've gotten to run the extra high octane tune with the ultra-light wheels, and WOW it is FAST. I was running times competitive with GTIs (actually I beat more than half of them), I even beat both EVO Xs that were there :)
I just saw your video there! Nice handling, and wow when you were braking at the end the tail wanted to come around in the wet.
 
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