Shaking 2nd row seat / high RPMs for a given speed?+

[Heat]

I bought a new '09 Sport with manual transmission today, already have a couple of issues.

1. The 2nd row seat behind the driver shakes. The following video was taken at about 65 mph on a flat, smooth interstate:

http://www.youtube.com/watch?v=NMyzCh0YMOk

When watching the video, notice how the 2nd row passenger seat isn't shaking.

I had a cup of hot chocolate in the 2nd row cupholder, filled up to about a half inch from the top but with a coffee-style lid on it. The hot chocolate was shaking enough to splash out of the small lid opening. Luckily I had some paper on the floor in front of it, here is a picture of the splashes on the paper (I had already cleaned up the cupholder area):

http://img23.imageshack.us/img23/495/img0463.jpg

2. RPMs seemed high for the speed, it was almost like I was in fourth gear instead of fifth. I was reaching 3,000 rpms at 65 mph with the AC off:

http://img179.imageshack.us/img179/4704/img0462.jpg

In my other cars I reach 3,000 rpms around 73 to 75 mph. Is this just because the car is new, or is this just the way it is? It's almost like this car needs a sixth gear for cruising on the interstate.

Thanks!

 

[coolmazda5]

I bought a new '09 Sport with manual transmission today, already have a couple of issues.

1. The 2nd row seat behind the driver shakes. The following video was taken at about 65 mph on a flat, smooth interstate:

Normal, and my 06 used to do it even worse, until I changed the tires to Yokohamas.

My theory is that the 2nd row captain chairs are not as rugged as the first row seats and, unlike the traditional 2nd row bench seats, they don't have any lock points to the car pillars, so it makes them look shaky (dunno)

2. RPMs seemed high for the speed, it was almost like I was in fourth gear instead of fifth. I was reaching 3,000 rpms at 65 mph with the AC off:

In my other cars I reach 3,000 rpms around 73 to 75 mph. Is this just because the car is new, or is this just the way it is? It's almost like this car needs a sixth gear for cruising on the interstate.

Normal as well, I think somebody from Europe posted a pic of their Mazda5 MT in 6th gear (2.0L engine however) and the RPMs were very similar to a 5MT in the US at 100km/hr, ~63MPH, so I don't know if a 6th gear would really help (The 2010 Mazda3 has it now though).

My 2nd silly theory is that the RPM/Gear ratio is higher on the Mazda5 due to the extra weight compared to a i.e. Mazda3. In this way the good engine response is still kept even with a heavier car. I actually like that part, the car feels peppy at all speeds w/o the need to constantly downshift

 

[bulwnkl]

Coolmazda5 has it.

The 2nd row seat(s) shake because of a driveline imbalance. Most all have found it to be the OEM tires. Once those are changed out, there's no more shake. Not to say it couldn't be something else, though. I bet you'll find that the exact thing that shakes the most sort of moves around the car as your speed changes. There'll still be a certain speed where something shakes the most.

The rpm thing is just how the car is geared. It's not going to change later on. Did you not drive it before buying? Either way, it's not going to cause any problem. In fact, as cm5 said, it's geared this low in large part to give you better pep against the higher weight and aerodynamic drag of the 5 (compared to the 3).

 

[Heat]

OK, after my post I was thinking that it might be a tire issue, looks like it is.

As far as RPMs at highway speed, I rented an '09 Sport last weekend and put 700 miles on it, mostly interstate but it was an automatic. Either it didn't have a tachometer, or if it did the RPMs were not over 3,000 at 70 mph - I would have noticed if the higher than usual RPMs. With the vehicle I bought , sure I test drove it, but only for a few miles and not on the interstate - that was just to make sure that this particular car had nothing obviously wrong with it as well as to try out the Mazda5's manual transmission.

As long as I get the 28 mpg or better I guess. Plus, it's still better than the highway mileage of any other minivan. But normally a manual transmission has fifth gear at lower RPMs and lower power of course, then to pass you just drop it into fourth gear.

 

[bulwnkl]

One might suppose so, but actually automatic transmission-equipped vehicles typically have higher gearing these days. That's why you'll sometimes see higher highway mpg ratings on the A/T version of a given vehicle. I'm sure the A/T 5 you drove was turning a bit slower on the freeway than your M/T one does. At least the 5 used to be geared that way. Don't see why they'd have changed for '09. Part of the zoom-zoom, you know.

 

[coolmazda5]

Here you go, this may explain why

Transmission Gear Ratios:

                5MT   	 5AT
1st 	        3.307 	3.620 	
2nd 	        1.842 	1.925 	
3rd 	        1.310 	1.285 	
4th 	        0.970 	0.933 	
5th 	        0.755 	0.692 	
Reverse 	3.166 	3.405 	
Final drive 	4.388 	3.863

Source:
http://www.autocitymazda.com/index.php?option=com_nvdetail&task=show_car&carid=50&img=image4

 

[wmzda5]

2. RPMs seemed high for the speed, it was almost like I was in fourth gear instead of fifth. I was reaching 3,000 rpms at 65 mph with the AC off:

http://img179.imageshack.us/img179/4704/img0462.jpg

In my other cars I reach 3,000 rpms around 73 to 75 mph. Is this just because the car is new, or is this just the way it is? It's almost like this car needs a sixth gear for cruising on the interstate.

Thanks!

I have 3k rpm @100kph-105 kph thats about right

 

[Heat]

Makes sense with what I’ve seen.

But if RPMs at a given highway speed are higher for the manual transmission, why is the manual transmission rated as have a slightly higher fuel economy (28 mpg vs 27 mpg)?

Say I'm cruising at 65 mph in fifth gear at 3,000 RPMs, and a Mazda5 next to me with automatic transmission is also cruising at 65 mph in the automatic's fifth gear, but at 2,800 RPMs (estimate). How can I be getting better gas mileage?

And for what it's worth, the manual tranmission is definately "peppier" than the automatic.

 

[bulwnkl]

That's mainly because the EPA tests aren't purely steady-state, and not at 65. The automatic is burning extra fuel losing energy through the torque converter all the time until it locks up (don't know what speed that is; probably 40-50?). After that, it's likely more efficient because it's turning slower and the loss of the fluid coupling (torque converter) is gone since it's locked up.

So, that means that once the test hits steady-state 'highway' speed, the A/T is using less fuel. All the time the two were accelerating up to that condition, however, the M/T was using less fuel. On average, they're about even on the testing (within 1 mpg counts as about even, don't you think?). In each individual's driving, and accounting for sometimes large car-to-car variation, either transmission may give you better mpg under your particular conditions. Make sense?

 

[Heat]

From another thread I see that the automatic is at 2500 to 2600 RPMs at 70-72 mph. The manual transmission is at something like 3200 RPMs at 70-72, so of course the automatics will get better gas mileage at interstate speeds.

If you were wondering why the manual transmission is rated as having better fuel economy it is because the average speed for the highway test is 48 mph. From the US EPA’s website:

… The highway simulates a 10 mile trip with an average speed of 48 mph. The vehicle is started "hot" and there is very little idling and no stops…

So basically Mazda designed their manual transmission to do well on the fuel economy tests as well as to be very peppy at low speeds, but with no consideration to higher speeds (70 to 75 mph). The fifth gear of the Mazda5 is the equivalent of fourth gear in any other manual transmission vehicle I’ve driven (in the other cars you could then slip into fifth gear on the interstate to drop RPMs by 750 or so).

For what it’s worth, I love the Mazda5 with manual transmission for speeds up to normal highway speeds (55 to 60 mph), it’s only on the interstate that I have issues with it. Unfortunately, the main reason whey I bought the Mazda5 was for interstate travel (family trips), so the family would have more room on longer trips and I’ll be putting in a DVD player for the kids.

I’m not going to do anything until the car is out of warranty, but a manual transmission from oversees is one possible way to get a true fifth gear in this vehicle. I assume that it would be a relatively simple swap…