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Discussion Starter #1 (Edited)
This topic might belong in the Engine forum but I will post here. I am wondering if the engine specs on the Japan engine and US engine are the same. Here in Asia we can run on E85, not sure if US spec cars can. And I was just reading a Mazda Asia ad and it said,

"Skyactiv-G 2.0 engine power coming from the CX-5 adjustable to accommodate E85 power 165 hp at 6,000 and a maximum torque of 210 Nm at 4,000 rpm with the same machine. Plus, save an additional 20% to the front wheels with high transmission gear Skyactiv 6 Speed."

Now I think the US cars are rated at 155hp. Here is the full press release. It is in Thai but Google translator does a good job.

http://www.autospinn.com/2014/03/ชมภาพตัวเป็นๆ-2014-all-new-mazda-3-e85-พร้อมท/

This is the sticker inside the fuel cover. Is it the same in the US?

 

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Australia and North America share the same petrol engines due to similar fuel specifications sold:

A "detuned" 2 litre petrol with a lower compression ratio that runs on 91 RON fuel, up to 10% ethanol. This produces 155bhp.

And a 2,5 litre petrol that also runs on 91 RON fuel producing 192bhp shared with the Mazda 6, also taking ethanol up to 10%. The Australia vehicles include Automatic start-stop (i-Stop).

Japan and the EU and maybe other regions have a 2 litre petrol with a higher (14:1) compression ratio that gives it 165bhp but requires 95 RON which is widely sold in these two countries. The fuel quality in terms of sulphur ppm is also much better in these two regions. This will also run on up to 10% ethanol.

For other countries, it is likely that Mazda supplies parts that make the engine capable of running on E85 (for instance, Brasil). But generally this is not the case. There is a wide variation of emissions and engine components for the Mazda 3 BM sold worldwide.
 

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Is it possible to modify a 13:1 compression ratio to 14:1? What's the mechanical/physical difference between the engines?
 

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The US gets a 13.1 CR engine and japan gets the full pop at 14.1 CR. More compression more power. We get less compression because we have to make do with 87 octane and a max of 91 in some places.
 

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I use 98 oct in general. The difference won't break my bank. As such I would love to go from 13:1 to 14:1 but I believe this would require forced induction
 

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I use 98 oct in general. The difference won't break my bank. As such I would love to go from 13:1 to 14:1 but I believe this would require forced induction
Two things. First, the bhp gains to go from a 13:1 to a 14:1 compression ratio are marginal at best and would require some internal mods that would definitely fall under the "not worth it" category. For all of maybe 10 bhp? You can't feel a 5-6% bhp bump in most cases. Two, your forced induction comment doesn't make sense. It doesn't really have anything to do with raising compression. And as an extension of that, in a forced induction motor, you actually usually have to lower compression because of the increased risk of detonation. Off the top of my head the highest compression ratio on a forced induction motor that I can think of is 10.6:1 on the Subaru DI-2.0 turbo motor in the WRX and Forester. There may be examples with higher ratios but it's rare to go much over 10:1.
 

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Two things. First, the bhp gains to go from a 13:1 to a 14:1 compression ratio are marginal at best and would require some internal mods that would definitely fall under the "not worth it" category. For all of maybe 10 bhp? You can't feel a 5-6% bhp bump in most cases. Two, your forced induction comment doesn't make sense. It doesn't really have anything to do with raising compression. And as an extension of that, in a forced induction motor, you actually usually have to lower compression because of the increased risk of detonation. Off the top of my head the highest compression ratio on a forced induction motor that I can think of is 10.6:1 on the Subaru DI-2.0 turbo motor in the WRX and Forester. There may be examples with higher ratios but it's rare to go much over 10:1.
This is very true, most turbo engines have a 8 or 9:1 compression ratio. This is also why any turbo car runs like crap with when the turbo goes out. The engine just doesn't produce much power with out the turbo.

If you were going to increase the compression, you may was well have the cylinders bored out, so you can put a bigger pistons in there, swap out the injectors, throw on an exhaust manifold, a full exhaust system and have the ECU re-tuned. I wouldn't be surprised if you could get 250-300HP out of the 2.5 engine. Fuel mileage would go out the window, but you'd have a lot more power for the money.
 

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The newest BMW engines (B38, N20) run a compression ratio of 10,5 to 11:1 but then again, BMW makes some of the very best engines so it comes as no surprise they can push the envelope.
 

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This is very true, most turbo engines have a 8 or 9:1 compression ratio. This is also why any turbo car runs like crap with when the turbo goes out. The engine just doesn't produce much power with out the turbo.

If you were going to increase the compression, you may was well have the cylinders bored out, so you can put a bigger pistons in there, swap out the injectors, throw on an exhaust manifold, a full exhaust system and have the ECU re-tuned. I wouldn't be surprised if you could get 250-300HP out of the 2.5 engine. Fuel mileage would go out the window, but you'd have a lot more power for the money.

You're dreaming if you think the above mods are going to net 250hp, let alone 300. The very best Honda K series 2.0L / 2.4L Frankenstein with ported EVERYTHING, massive cams, and practically the best flowing head in the business and good ol Vtec, revving sky high struggles to get 275-300whp. No way your regular run of the mill Mazda 3 Skyactiv engine, that's been designed for FUEL ECONOMY as a #1 priority will EVER reach those numbers in N/A form. Nope, sorry, I just don't buy it.

I had an 07 Civic Si and have been on the 8th Gen forum for 7 years, trust me, I've seen it all. The amount of money it takes to reach those numbers in N/A form are 2-3x the cost of a turbo kit bolted on a stock block.

In my Opinion, the BEST way for us to squeeze decent power outta the Skyactiv is a rather mild turbo kit. The K20 has 11:1 compression ratio and handled boost just fine with the stock block. The 13:1 ratio in the US spec Skyactiv might be challenging but definitely possible with extensive and EXPENSIVE engine work.
 

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You're dreaming if you think the above mods are going to net 250hp, let alone 300. The very best Honda K series 2.0L / 2.4L Frankenstein with ported EVERYTHING, massive cams, and practically the best flowing head in the business and good ol Vtec, revving sky high struggles to get 275-300whp. No way your regular run of the mill Mazda 3 Skyactiv engine, that's been designed for FUEL ECONOMY as a #1 priority will EVER reach those numbers in N/A form. Nope, sorry, I just don't buy it.

I had an 07 Civic Si and have been on the 8th Gen forum for 7 years, trust me, I've seen it all. The amount of money it takes to reach those numbers in N/A form are 2-3x the cost of a turbo kit bolted on a stock block.

In my Opinion, the BEST way for us to squeeze decent power outta the Skyactiv is a rather mild turbo kit. The K20 has 11:1 compression ratio and handled boost just fine with the stock block. The 13:1 ratio in the US spec Skyactiv might be challenging but definitely possible with extensive and EXPENSIVE engine work.
Hey man, I never guaranteed those numbers, I'm just saying that if you totally made your engine into a performance engine rather than econo pusher, it wouldn't surprise me. You're right though, it's going to cost a lot of money to get there. I didn't think about it before, but you're right... With the right engine work, you could probably throw in a turbo.

A guy a work with has a 91 MR2 that he has dumped a TON of money in to. He's got about 20psi in to a turbo and he's running 11.5:1 compression. He's disappointed it came back from the tune and dyno at 370HP and not 400+, so he's already working on changing out cams, inter-cooler and getting yet another fuel pump, so he can further increase his performance.

Haha, he has what I call "Single guy problems". Too much money that he doesn't know what to do with it.
 

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I'm wondering if the difference between the 13:1 and 14:1 are just the pistons.

Anyway, I'd rather have a supercharger as it closely resembles NA power delivery. Any FI would likely have to run low boost because of such a high compression ratio.
 

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well we already know that at 4psi of boost the US skyactiv 2.0 is running the fuel system at %90 capacity. so even if the motor and tuning can be done to achieve a little higher boost on the SA motors they are going to need some major expensive parts to make it a reality.
 

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To further answer OP's question, we do not get the premium fuel engine configuration with flexfuel compatibility and for ridiculous reasons that I won't get into. But it involves a mixture of politics and American opinions.

I digress, 91 AKI is available everywhere in the US. It is the same as 95 RON.
 

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Hi everyone,

The idea of 14:1 compression engines in these cars and how they compare to 13:1 compression has always been something I have not been able to get to the bottom of through research on the internet.

Next time I am in Japan I will go to a dealer and try to find out the answer.

Does anyone have a reference to a 14:1 compression 2.5 litre horse power and torque output authority?

I have tried to read the Japanese Mazda web site, but as I don't speak or read Japanese can't get to the bottom of this issue. Are any 2.5 litre engines actually available in 14:1?

If you can't find out, then I will ask my wife to look into for me.

Kind regards Marc.
 

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Discussion Starter #16
Hi everyone,

The idea of 14:1 compression engines in these cars and how they compare to 13:1 compression has always been something I have not been able to get to the bottom of through research on the internet.

Next time I am in Japan I will go to a dealer and try to find out the answer.

Does anyone have a reference to a 14:1 compression 2.5 litre horse power and torque output authority?

I have tried to read the Japanese Mazda web site, but as I don't speak or read Japanese can't get to the bottom of this issue. Are any 2.5 litre engines actually available in 14:1?

If you can't find out, then I will ask my wife to look into for me.

Kind regards Marc.
Not sure if the 2.5 engine has a 14:1 or even if the US and Japan spec 2.5 engines are different. So far it is just the 2.0 engine
 

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Hey guys, is it normal that my 2013 Canadian-spec Skyactiv has a compression ratio of 12:0 as opposed to 13:1 ?
Yeah that's normal... 12:1 for 2012/13 because the old body style couldn't fit the header needed to work with the higher compression ratio.

2014 moved to 13:1 with the required exhaust header.
 

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well we already know that at 4psi of boost the US skyactiv 2.0 is running the fuel system at %90 capacity. so even if the motor and tuning can be done to achieve a little higher boost on the SA motors they are going to need some major expensive parts to make it a reality.

Injectors aren't too badly priced. Fuel pumps get up there quick though. Any sort of turbo setup would likely be in the 5500 range.
 

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Yeah that's normal... 12:1 for 2012/13 because the old body style couldn't fit the header needed to work with the higher compression ratio.

2014 moved to 13:1 with the required exhaust header.
As explained by Dave Coleman, a Mazda design engineer who worked on the various components of the "skyactiv" concept (for the exhaust manifold and compression ratio, see 2:10 in the vid).

https://www.youtube.com/watch?v=rNtS8qyjIJU
 
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