The truth about the 2019 Miata rev limiter

It took us a while and some connections, but we finally have a hard tech answer to the rev limiter question from a legit technical (aka, not marketing) source inside Mazda and backed up by testing.

The tach is offset by 300 rpm - at 7200 rpm actual, it reads 7500 on the dash. This is unrelated. We've known about this since we started dyno testing last week, we were waiting for more information. It appears this may only be in the US (North America) for reasons unexplained. The ND1 also has an offset tach and of course it's been a Miata feature for a couple of decades. All further references to engine speed will be actual, not indicated.

The 7500 rpm "overshoot" rev limit is only available in 1st and 2nd gears. Why? Because Mazda does not want sustained 7500 rpm use, and that's the only way to guarantee it will be a transient limit. Otherwise, the car has a 7200 rpm limiter.

No, we have not yet checked to see if you can sit on the 7500 limiter in 2nd yet. We will find out.

We have confirmed that there is a 7500 rpm limiter in 2nd on the dyno. In our first gear test, things happened pretty quickly and we could not confirm the limit. We have confirmed the 7200 limit in 3rd and 4th. 5th and 6th will never reach the limiter on the road without significant power adders.

So there you go.

The important question is...have we named this yet?  RevGate? RMPGate? Gaugegate?

Why would we? It's not a scandal. It's a technical aspect that wasn't properly explained. The 7500 overshoot limit is just like an overboost option on a turbo car. Usually, that's touted as a feature.  I mean, I understand it's fun to light the pitchforks and sharpen the torches, but there are probably more important things to get all hot and bothered about. The car's fun, it'll be faster and it's responding really well to bolt-on exhaust mods. Can't complain about any of that.

So does it display 7800 rpm in 1st and 2nd or is the tach offset only in 3rd gear up? 

Just curious 

Adam

I've seen it peg past 7500 on the street in second but of course it happens pretty quickly and it almost looks like the needle just has some momentum. Still, I'd say that it probably shows the same offset in every gear based on that.

I have requested that whoever is driving the 2019 tonight do the "sustained redline in 2nd" test, maybe we'll find out then. I'm stuck driving the V8 ND to test some CAN programming, darn the luck.

Thanks for checking and confirming all of this Keith. Should make autocrossers happy. 

Keith Tanner said:

 

I have requested that whoever is driving the 2019 tonight do the "sustained redline in 2nd" test, maybe we'll find out then. I'm stuck driving the V8 ND to test some CAN programming, darn the luck.

Yes, terrible luck. 

Keith Tanner said:

The 7500 rpm "overshoot" rev limit is only available in 1st and 2nd gears. Why? Because Mazda does not want sustained 7500 rpm use, and that's the only way to guarantee it will be a transient limit. Otherwise, the car has a 7200 rpm limiter.

Let me guess -- 7500 RPM in second puts it just over 60 mph? :)

Thanks for following up. I guess the only remaining questions I'd be curious about are A: should an autocrosser who will bounce off the limiter in 2nd rather than attempt a shift many times in their car's autoX career be worried about durability, and B:  pending that it doesn't suffer a drastically shortened life, will the powerband of the stock car or with typical power mods justify moving the limiter up to 7500 all the time, or beyond? 

Again, thanks for the digging and relaying the info.

So, um, is the tach off by 300 at idle too?

That would seem ridiculous I guess, but purposely making a guage read wrong is not my area of expertise.

In reply to Robbie :

I doubt it is off at idle. Could be a linear function where the error is proportional to rpm above a certain value. I'm used to temperature gauges reading inaccurately, but always figured a tach would read correctly. I agree with and understand what Keith is saying that  this doesn't matter, but it just seems like a very odd and silly deception for no apparent reason. 

Has anyone at Mazda explained why they made an inaccurate tach?

Nigel Tufnel: The numbers all go to eleven. Look, right across the board, eleven, eleven, eleven and... 

Marty DiBergi: Oh, I see. And most amps go up to ten? 

Nigel Tufnel: Exactly. 

Marty DiBergi: Does that mean it's louder? Is it any louder? 

Nigel Tufnel: Well, it's one louder, isn't it? It's not ten. You see, most blokes, you know, will be playing at ten. You're on ten here, all the way up, all the way up, all the way up, you're on ten on your guitar. Where can you go from there? Where? 

Marty DiBergi: I don't know. 

Nigel Tufnel: Nowhere. Exactly. What we do is, if we need that extra push over the cliff, you know what we do? 

Marty DiBergi: Put it up to eleven. 

Nigel Tufnel: Eleven. Exactly. One louder. 

Marty DiBergi: Why don't you just make ten louder and make ten be the top number and make that a little louder? 

Nigel Tufnel: [pause] These go to eleven.

Apparently the inaccurate tach is a US thing according to a comment made by my tech contact, and I can tell you it dates all the way back to the 1.6. 7200 rpm redline, 7500 on the dial. Go figure. 

Loads on the reciprocating parts go up exponentially with engine speed. I’ll bet Mazda knows exactly how many trips to 7500 can be expected before you reach the mean time before failure, and I’ll bet that number is greater than can be expected over the planned lifespan of the engine. Will autoxers bouncing off the rev limiter constantly shorten the lifespan of their engines? Possibly, but when has that not been the case?

i believe an autoxer has already clocked a car at 61 mph in 2nd. I’ve seen over 60 indicated. 

In reply to aircooled :

I have volume knobs that go to 11 on my Gibson. Because, you know, they go to 11. 

Sounds to me like Mazda has figured out the US market wants the car to redline to 7500.

This thread is evidence!

So, they accommodated. 

(But it is a little strange)

pinchvalve said:

The important question is...have we named this yet?  RevGate? RMPGate? Gaugegate?

Yamahagate. Yamaha had the same issue with its 50th anniversary R6s. Bad enough that they bought back ones from owners who bitched enough. Lame.

codrus said:

Keith Tanner said:

The 7500 rpm "overshoot" rev limit is only available in 1st and 2nd gears. Why? Because Mazda does not want sustained 7500 rpm use, and that's the only way to guarantee it will be a transient limit. Otherwise, the car has a 7200 rpm limiter.

Let me guess -- 7500 RPM in second puts it just over 60 mph? :)

 

Did the math. 7200 puts it just over 60. So much for that theory!

Appleseed said:

pinchvalve said:

The important question is...have we named this yet?  RevGate? RMPGate? Gaugegate?

Yamahagate. Yamaha had the same issue with its 50th anniversary R6s. Bad enough that they bought back ones from owners who bitched enough. Lame.

Except it wasn't just that it was limited above 1-2 gears. The redline was 1500-1800rpm lower claimed............all day, 'ery day. And they used that has a huge selling point when they released the 2006 R6 and it was also a bit down on power compared to claims........that's what initiated the buy backs.

z31maniac said:

Appleseed said:

pinchvalve said:

The important question is...have we named this yet?  RevGate? RMPGate? Gaugegate?

Yamahagate. Yamaha had the same issue with its 50th anniversary R6s. Bad enough that they bought back ones from owners who bitched enough. Lame.

Except it wasn't just that it was limited above 1-2 gears. The redline was 1500-1800rpm lower claimed............all day, 'ery day. And they used that has a huge selling point when they released the 2006 R6 and it was also a bit down on power compared to claims........that's what initiated the buy backs.

that sounds like the "250"hp rx8...

I think most people asking about this (autocrossers) don’t really care about the actual RPM, they just want to know the MPH while it’s eating the limiter in 2nd. 

Agreed, although with fixed gearing that's the same thing. And of course, they're only interested in second gear. Autoxers are weird.

I could have a "tach rescaler" programed and in our car by the end of the day if the actual indicated RPM is important. Send money.

Keith Tanner said:

codrus said:

Keith Tanner said:

The 7500 rpm "overshoot" rev limit is only available in 1st and 2nd gears. Why? Because Mazda does not want sustained 7500 rpm use, and that's the only way to guarantee it will be a transient limit. Otherwise, the car has a 7200 rpm limiter.

Let me guess -- 7500 RPM in second puts it just over 60 mph? :)

 

Did the math. 7200 puts it just over 60. So much for that theory!

Did you account for the decrease in actual rolling radius from tire deformation?  I typically use a ~3% average squish factor for the tire revs per mile, based on the trends I had seen for this data in the Tire Rack specifications.  So assuming my 'stock ND' inputs are all correct, after the correction I'm seeing theoretical 2nd gear limits of 59 mph @ 7200 rpm and 61 mph @ 7500 rpm...Which correlates almost perfectly with the real world observations being reported.

That squish may change with speed. I did not invest a lot of time in it as it's not really a critical question for me. I also understand that tire sizes are approximate and not mathematically ideal.

Keith Tanner said:

Agreed, although with fixed gearing that's the same thing. And of course, they're only interested in second gear. Autoxers are weird.

I could have a "tach rescaler" programed and in our car by the end of the day if the actual indicated RPM is important. Send money.

Takers on that will be 0, lol

The only people complaining weren't going to go out to the dealer and buy a new one anyway.

The actual mph and actual rpm limit are irrelevant when the car is by itself on the autox course.

They are only useful when comparing to other makes and models. 

So, as long as you apply all the same squish factors etc to both in your comparison, you should be fine.