2016 3rd Gen Mazda Engine Internals for Rebuild

rdfrederick87 said:

I thought I would see what the MX-5 was running as it seems to be the Mazda "sports-car" and was shocked to find out it only has the 2.0L motor at 155 horsepower - not much of a sports car. Further more, after comparing all the specs to see they are the exact same - their site says for the Mazda 3 use regular unleaded, but for the same motor under MX-5 it says use premium. Seems like Mazda doesn't even know what they are talking about.

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I think you need to do a lot more research before you come here spouting off about things that you know nothing about. The two motors are not the same, and Mazda does know what it is talking about.
Internally, the two motors are pretty much the same. The tune on the MX5 is tweaked a bit for more throttle response and a couple other things.
The reason that the MX5 needs 91 octane is to prevent detonation. When detonation is detected, the ECU pulls timing until it stops. This means a power loss. The Skyactiv engine needs a high level of exhaust scavenging to prevent detonation using 87 octane. This is accomplished on the Mazda 3 using a tri-y header that separates the exhaust pulses and prevents them from returning spent gasses into the cylinder. Unfortunately, this header does not fit in the MX5 tunnel, so it gets a regular shorty header type exhaust. This header can't scavenge nearly as well so 91 octane is required to prevent excessive detonation. There is an aftermarket tri-way for the MX5 that makes a significant power improvement.

rdfrederick87 said:

MX-5 is 1113KG, Mazda 3 Sedan is 1303KG. Are you telling me 190KG difference determines a sport car vs. sedan? Clearly you have no idea what you are talking about.
Looking for value added feedback - not a pissing contest.

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As for not being much of a sports car, ask the significant number of high dollar sports car drivers who have had their butts handed to them by a 155 hp car. Also, the mx5 is significantly faster then the Mazda 3.
Feedback? You are getting it. If you don't like what you are hearing, oh well. Get over it.

rdfrederick87 said:

Again, original question was about the motor and facts. Sure Its sport looking - and likely fun to drive no doubt, and yes 410lbs of weight is a good chunk that would help. but at the end of the day it still 155hp NA sports car. It likely is a little faster than the 3, but unless your talking quarter seconds on track its not going to be a giant notice of a difference once you take the "fun" level out of it. .

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Quarter seconds? How about 10 seconds? Thats how much faster the MX5 is around The Streets of Willow vs the much vaunted 707hp Dodge Charger Hellcat. Get over the power trip and learn what a real sports car is.
You do realize that the MX5 is the single most raced car around the world?

rdfrederick87 said:

Again, talking Motor - not sure why people cant grasp that concept. Yes the MX5 is quicker - but the motor in the MS3 is better than the MX5. I even said the car itself was heaver, which would lead to likely a slower car. OP was about motor internals - lets talk about that.

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Once again, there are none except maybe a cam. If you want to be fast there are other ways. You are not going to make big power from this motor.

rdfrederick87 said:

Hypothetically if took a MX-5 motor in dropped it in a 3 I would get no real gain, if I took a MS3 motor and dropped it in my M3 - clearly I would being that it is 100+ HP over my current motor. Proving that in fact the motor is better.

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Thats not how it works. You are still chasing numbers. That does not mean its better in any way, it just means it makes more power. It does not mean in any way that the car will be faster. :bash::bash:

rdfrederick87 said:

While yes I agree with your racing comment, the one thing that is nice is the high compression which I am trying to hang onto. If (like in my OP) could get stronger internals I would take a stab at turbo. Anything right now over 5+ PSI would like result in catastrophic failure, but if the motor itself could take it - a small introduction of boost will yield high numbers based on the compression. I would likely need E85 to avoid other issues but that's fine - this isn't my daily driver.

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Once again, you need to do more research on the SkyActiv engine. The 13:1 compression ratio is the theoretical maximum based on bore and stroke. The way the motor works varies the compression according to the engine load.
You don't need stronger internals for the FI setup. Current FI units get about 250 hp from the 2.0. Thats more than enough for this car. You don't want to go much more than that or you risk blowing up the rest of the driveline. The transmission, clutch, halfshafts all would need to be upgraded. There is no way to be fast on a road course in a high power FWD car without a limited slip front differential.
Again, this chasing numbers is foolish. The car will never be a race car no matter how much wish it to be. If you are going to throw a lot of money at your car, get the important stuff and do it right. There is more to making a car go fast than power. Better tires- the OEM rubber sucks. Better brakes - if you are going to go fast you better be able to stop just as fast. Better suspension - if you are going to do some canyon driving or some such hooliganism you need to do more than go in a straight line. Same things apply if you intend to do track days. Why do you think that the MX5 was 10 seconds faster around Willow Springs? It wasn't because it had more power. It was because it is a faster car. There is a big difference.
If you want inexpensive useable power, get a tune. There are a couple good sources. That will get you to almost 200hp if done right.

rdfrederick87 said:

Just think about that for a minute. That's like saying if you put the MX-5 motor inside the MS3 with no weight reduction that it would produce the same numbers.

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No, read what I said. More power does not equal a better motor or better performance, period.
That much power in the Mazda 3 can be detrimental to performance.

rdfrederick87 said:

So your telling me I can just jam 15 PSI down its throat and the internals will be just fine because its FI - get real. Perhaps your the one that needs to do some more research - to think the factory fuel efficient naturally aspirated motor will take any set amount of boost is silly, especially if it was driven hard. Agreed, transmission would need to get upgraded as well to support the extra load, but need to figure what the load is first.

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As I said before, this motor is not a good platform for major power and the best you can reasonably expect with FI right now is 250 hp or so without risking blowing it up. That means not using 15 lbs of boost. 7 maybe 8 but not 15. You would need to lower the CR to do that and strengthen some other components. Mazda has already done this with the new CX9 with the 2.5 turbo motor that has 10:1 compression. Again, you really need to research how this motor works before you go throwing money at it.

rdfrederick87 said:

Sure it was faster around Willow springs because it was set up correctly- but you have to give reason. If the car is structured for track but lacks power it will loose, but so will a car that has power but lacks structure - it goes both ways.

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Both cars were as built, no upgrades. So far, your reasoning appears to equate power to being fast on the track. The above cars proves that assumption to be incorrect.

rdfrederick87 said:

As for upgrades. I am already 90% of the way through those, that's why I am asking about motor. I am currently running upgraded springs, struts, rubber, wheels, sway bars, cambers, strut bar, end links - Just waiting on brakes. I haven't done a tune yet because I am waiting on the motor solution if any. I am not going to tune it and then re-tune it after rebuild.

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The only upgrade you will find fairly easy to locate would be cams from a Miata. Other than that, there is nothing other than the usual ricer SRI mods and performance exhausts. You can't even find a header for the 3 as the factory part is nearly perfect. All attempts at "improved designs" have failed miserably.
Thats not saying it can't be done. If you have a lot of money to toss at it, custom rods can be fabricated, maybe a stronger crank too. The overall design might not work well for higher rpm applications though. The head has room for improvement. Port and polish can make a bit more power, maybe bigger valves. The plastic intake is the weak point here.
Get the tune, see where it gets you. You can always retune for future changes. That way you know if those changes actually did anything and if so what gains were made.
Seems to me if you are going through all this just to get a few extra hp, just pull the motor and stuff in a Honda Vtec. Might be cheaper and easier.