4th gen ND Mazda MX-5 Miata

[strat61caster]

@chrisl @thill

Specs still aren't out, they could totally hit those power figures if they throw fuel economy out the window, Toyobaru managed to get 200 horses with D4S, no reason Mazda can't come close with true DI. BUUUT marketing a sports car with >30 COMBINED MPG will likely drive at least a handful of sales.

Also the current 2.0L claims 150 ft-lbs. of torque at 4,000 rpm, it will be at least on par with the Toyobaru in terms of torque while sliding in nearly 500 lbs. lighter.



The more I think about it, the more I'm excited, especially if Fiat stops screwing around and delivers a companion off the same chassis, a straight swap of the 1.4L MultiAir in the Abarth would be a hoot, more so if they go balls to the wall and toss some MOPAR at it, seems like 25-30 horsepower is available with a tune and mucking with the turbo putting that up into the 190 hp territory.


Here's a dynosheet that K&N published for the 2.0L in the Mazda3, for all the talk of delivering a flat torque curve on a Toyobaru...

http://www.knfilters.com/dynocharts/69-6033_dyno.pdf

[Deslock]

Originally Posted by juliog

NC: 21/28 MPG (6MT)
FR-S/BRZ: 22/30 MPG (6MT)
Mazda 3: 29/40 MPG (2.0L MT)

Since the ND will be using the Mazda 3's engine and is ~500lbs lighter:

ND: 30+/40+ MPG (2.0L MT)

The lower curb weight will improve fuel economy. The engine being mated to RWD and tuned for output and throttle response will hinder it.

[juliog]

True that. I guess convertibles also take a hit in mileage when the top is put down? Does the EPA test convertibles with the top up or down?

[serialk11r]

Originally Posted by Deslock

The lower curb weight will improve fuel economy. The engine being mated to RWD and tuned for output and throttle response will hinder it.

Actually tuning for output doesn't hinder fuel economy for faster cars because the maximum output isn't used in the test. Besides, no engine comes from the factory actually tuned for output, because they always run rich to protect the cats. I'm fairly sure the MX5 won't need to be floored to pass the EPA's acceleration test.

Back in the day of cable throttles, you'd see stuff like the maximum advance on intake cams always activated on Porsche M96 engines for throttle response but nowadays everything is throttle-by-wire and I'd be surprised if they resorted to that kind of method to improve response. With throttle by wire the ECU doesn't have to detect the pedal going down and then shift the cams around, it can open the throttle and change timing at the same time. BMW's solution was to use separate oil pumps to drive the VANOS for better response in the M cars, Toyota's was to use electric motors instead of oil pressure in the higher end Lexus cars.

Originally Posted by juliog

True that. I guess convertibles also take a hit in mileage when the top is put down? Does the EPA test convertibles with the top up or down?

I don't think they actually test the aero, they just take the manufacturer's word for it and enter it into the dyno. The manufacturer tests the drag with top up for obvious reasons. If the EPA actually puts it in a wind tunnel to measure the drag then it would probably test with top up.

[Deslock]

Originally Posted by serialk11r

Actually tuning for output doesn't hinder fuel economy for faster cars because the maximum output isn't used in the test. Besides, no engine comes from the factory actually tuned for output, because they always run rich to protect the cats. I'm fairly sure the MX5 won't need to be floored to pass the EPA's acceleration test.

I disagree... even if it's not floored or run to redline, different tuning still affects MPG.

I forgot to mention that the Miata's gearing (assuming it's shorter) will also hinder its MPG.

[serialk11r]

Originally Posted by Deslock

I disagree... even if it's not floored or run to redline, different tuning still affects MPG.

I forgot to mention that the Miata's gearing (assuming it's shorter) will also hinder its MPG.

Different tuning only affects high load and high rpm operation assuming they already optimized the rest of the map, and the EPA does not floor it in tests. In real life when you do sometimes step pretty hard on the pedal, yes it affects fuel economy, but it doesn't come up in a test where they don't use the extra power.

Remember, this is the OEM we're talking about. They do their tunes very precisely, and they don't just add fuel everywhere the way some aftermarket tuners will, because they need to meet regulations. You don't add fuel when the engine still has some extra go in it. Throttle by wire lets you control this precisely.

[Rampage]

I expect Mazda will wring out a few more ponies from the 2.0L for what is, for now, their "halo" model. Even at 155HP the reduced weight and increased HP will make the car faster off the line and out of the corners plus the weight reduction will also aid in braking. The MX-5 will likely give the twins all the competition they want in autox and on the track stock to stock. The question will be whether the Skyactive engine will accept tuning and mods (including FI)as readily as the FA20 to keep the "moar power" boys happy.

[abraxis]

Originally Posted by juliog

NC: 21/28 MPG (6MT)
FR-S/BRZ: 22/30 MPG (6MT)
Mazda 3: 29/40 MPG (2.0L MT)

Since the ND will be using the Mazda 3's engine and is ~500lbs lighter:

ND: 30+/40+ MPG (2.0L MT)

You really think the Miata will have the same gearing as the Mazda 3?

[abraxis]

Originally Posted by Rampage

The MX-5 will likely give the twins all the competition they want in autox and on the track stock to stock.

AutoX yes. That's really a chassis advantage for a smaller car more than related to power. The current and past Miatas are already fine for autoX compared to the FRS. Same with your MR2. On the track? Not so much. The Miata will always be down on power and aero compared to the FRS stock for stock.

The Miata is still going to be a Miata, not a Corvette.

[serialk11r]

Originally Posted by abraxis

You really think the Miata will have the same gearing as the Mazda 3?

It's possible they (almost) retain the final drive + top gear ratio because this is a much lighter car. Despite the convertible part, it's probably still going to have less drag as well. 30+ mpg in the city is basically guaranteed even with 10% shorter gearing (and this only affects the EPA test, close ratio and short gearing is good in the city in real life cuz you have more gears to use at low speed). With 6 speeds and a solid amount of torque and power, it's pretty hard to mess up the gearing.

Even if they do the typical 2000s strategy of making everything shorter because sports car, remember that roughly speaking 20% higher cruising rpm = 10% less fuel economy, but if you have 10% less drag it kind of cancels out.

[Atropine]

Originally Posted by abraxis

AutoX yes. That's really a chassis advantage for a smaller car more than related to power. The current and past Miatas are already fine for autoX compared to the FRS. Same with your MR2. On the track? Not so much. The Miata will always be down on power and aero compared to the FRS stock for stock.

The Miata is still going to be a Miata, not a Corvette.

I really wanted to disagree with you...because you seem to not like the Corvette or the Miata, and you are occasionally inflammatory (aren't we all?)

But what you are saying here is 100% true.

Use the tool for the job.

I loved my BRZ. I love my Miata. I would love a new Corvette.

All are great, but they aren't the same.

All 3 are great cars, pick the one you like and respect other peoples choice for getting what they wanted.

[abraxis]

Originally Posted by Atropine

I really wanted to disagree with you...because you seem to not like the Corvette or the Miata, and you are occasionally inflammatory (aren't we all?)

But what you are saying here is 100% true.

Use the tool for the job.

I loved my BRZ. I love my Miata. I would love a new Corvette.

All are great, but they aren't the same.

All 3 are great cars, pick the one you like and respect other peoples choice for getting what they wanted.

Exactly. I don't dislike the Miata or the Corvette at all. I'm a car nut and have always known I'd need a bigger garage to stash my special automotive utensils. I just call it like I see it and don't like to sugar coat my comments, it's never personal except when someone just wants to be obstinate in their opinion even against the facts. Or I could just be biased in thinking that, who knows.

Frankly, I see people calling out the warts on a FRS or BRZ but rave about their Mustang, Vette, Miata, Genesis as the second coming. No. I see FRS and BRZ folk calling out those folks thinking their exhaust fumes don't stink. No. If people would just be more honest both ways, we could cut 85% of the BS posts on forums and get to constructive dialogues. I moderate on other forums so I just have little tolerance for it because it just gets dull, repetitive and unconstructive.

Anyway, thanks for getting what I was trying to say.

[Deslock]

Originally Posted by serialk11r

Different tuning only affects high load and high rpm operation assuming they already optimized the rest of the map, and the EPA does not floor it in tests. In real life when you do sometimes step pretty hard on the pedal, yes it affects fuel economy, but it doesn't come up in a test where they don't use the extra power.

Remember, this is the OEM we're talking about. They do their tunes very precisely, and they don't just add fuel everywhere the way some aftermarket tuners will, because they need to meet regulations. You don't add fuel when the engine still has some extra go in it. Throttle by wire lets you control this precisely.

Some aftermarket tunes improve both output and MPG (often at the expense of emissions), while some OEM tunes don't (though comparing base on sporty models of a car usually also means different gearing).

To be clear, I'm not just referring to ECU adjustments and air-fuel mixture. Perhaps I should write tunes/tweaks instead.

Originally Posted by serialk11r

It's possible they (almost) retain the final drive + top gear ratio because this is a much lighter car. Despite the convertible part, it's probably still going to have less drag as well. 30+ mpg in the city is basically guaranteed even with 10% shorter gearing (and this only affects the EPA test, close ratio and short gearing is good in the city in real life cuz you have more gears to use at low speed). With 6 speeds and a solid amount of torque and power, it's pretty hard to mess up the gearing.

Even if they do the typical 2000s strategy of making everything shorter because sports car, remember that roughly speaking 20% higher cruising rpm = 10% less fuel economy, but if you have 10% less drag it kind of cancels out.

It'd be great if the US-spec ND 2.0L gets rated at 30+ MPG city, but it's not guaranteed. Assuming shorter gearing and engine tunes/tweaks for better throttle response and more output, I expect it wont be that efficient.

[serialk11r]

Originally Posted by Deslock

It'd be great if the US-spec ND 2.0L gets rated at 30+ MPG city, but it's not guaranteed. Assuming shorter gearing and engine tunes/tweaks for better throttle response and more output, I expect it wont be that efficient.

Okay sure some power-increasing engine modifications will decrease mpg, like oversized valves (very slightly). However these days it's more common to just slap on a different manifold and call it a day, and those basically don't affect mpg. ECU tuning at the OEM doesn't decrease mpg, at least not for testing purposes like I said. They might spec thicker oil or something and that might decrease fuel economy by like 1%, again not much. A different cam profile could affect things, but again from the OEM, you're not going to get any drastic changes. Besides, bigger cams give you lower pumping loss, which cancels out some of the loss due to inefficient combustion.

It depends on how the shorter gearing is done. A substantially shorter final drive will ruin the EPA test numbers, but a close ratio gearbox with the same final drive won't because your 1st and 2nd gears will be pretty close to the original, and the main waste of fuel in the EPA city cycle is running the car in 1st gear and 2nd gear too much. Typically for sporty cars you see a close ratio gearbox and often times a shorter final drive as well, sometimes just one, but I think the closer ratios are more likely.

Another unknown factor is if they choose to specify shift points. If you officially recommend to shift out of 1st at 2000rpm, then you'll show significant improvement on the EPA test. I think most manufacturers are content to let the manual transmission die off so they don't care about this, but not always. The Ford Mustang and its 1-4 forced skip shift did wonders for its city rating, even though in the real world it probably doesn't actually help for most drivers.