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Old 07-12-2006, 01:32 AM   #1
Cristina
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Default RPM at 65, 70, 75 MPH?

Other vehicles I have driven cruise 70 mph at about 2,500-2,750 RPM, whereas my 3 at more like 3000 at 65-70 mph. And 75 mph is like 3500, its almost 4000 rpm if I go up to 80.. Does this seem a little high or is it normal for the 3?
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Old 07-12-2006, 01:34 AM   #2
whoamI
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Default Re: RPM at 65, 70, 75 MPH?

uh my 3 does the same thing and i have driven an acura TSX that drives at 2500 or less rpms at about 60. the mazda3 just got a close ratio that is all. it makes the car sportier ^_^
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Old 07-12-2006, 02:12 AM   #3
909
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Default Re: RPM at 65, 70, 75 MPH?

[quote author=Cristina link=topic=51301.msg817509#msg817509 date=1152682354]
Other vehicles I have driven cruise 70 mph at about 2,500-2,750 RPM, whereas my 3 at more like 3000 at 65-70 mph.* And 75 mph is like 3500, its almost 4000 rpm if I go up to 80..* Does this seem a little high or is it normal for the 3?
[/quote]

Here is the calculation for the 5sp MTX

1 2 3 4 5
0 0.0 0.0 0.0 0.0 0.0
500 2.7 4.9 6.9 9.3 12.0
1000 5.5 9.8 13.8 18.7 24.0
1500 8.2 14.7 20.7 28.0 36.0
2000 10.9 19.7 27.6 37.3 47.9
2500 13.7 24.6 34.5 46.6 59.9
3000 16.4 29.5 41.4 56.0 71.9
3500 19.2 34.4 48.4 65.3 83.9
4000 21.9 39.3 55.3 74.6 95.9
4500 24.6 44.2 62.2 84.0 107.9
5000 27.4 49.1 69.1 93.3 119.9
5500 30.1 54.0 76.0 102.6 131.8
6000 32.8 59.0 82.9 111.9 143.8
6500 35.6 63.9 89.8 121.3 155.8
7000
redline 38.3 68.8 96.7 130.6 167.8

Sorry the grid gets all askew but it should be able to read right. The 5 speed is geared a little sportier than the ATX. These cars make power up top, not down low so the gearing reflects where the engine needs to be to accelerate at speed.

Hope this helps!
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Old 07-12-2006, 04:32 AM   #4
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Default Re: RPM at 65, 70, 75 MPH?

I *may* be reading that wrong, but the redline on my 3 is 6500. Your graph seems to be showing that quite a bit higher than that.
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Old 07-12-2006, 05:09 AM   #5
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Default Re: RPM at 65, 70, 75 MPH?

[quote author=ViperKillerWannabe link=topic=51301.msg817623#msg817623 date=1152693146]
I *may* be reading that wrong, but the redline on my 3 is 6500. Your graph seems to be showing that quite a bit higher than that.
[/quote]

7k is "quite a bit"??? 6.5k is the redline on the gauge, 7k is rev limit.
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Old 07-12-2006, 08:03 AM   #6
4cylDriver
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Default Re: RPM at 65, 70, 75 MPH?

A few questions, are those numbers the mph corresponding to the RPMs. If so how come if the rev limiter is at 7K why does the top speed stop at 119.

Also when it comes to fuel milage i was checking the speed vs the RPMs and in 5th gear they all seem identical. So is speed and RPM not a good judgement of fuel. Does the car burn more gas at higher RPMs.

Example, which statement is more true

the car burns twice as much gas at 4000 RPMs than it does at 2000 RPMs
the car buns less than twice as much gas at 4000 RPMs than it does at 2000 RPMs
the car burns more than twice as much gas at 4000 RPMs than it does at 2000 RPMs.

This is considering cruising RPMs, no acceleration. Just driving on a flat grade and maintaing speed.
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Old 07-12-2006, 12:25 PM   #7
Cougar_333
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Default Re: RPM at 65, 70, 75 MPH?

I'd say less than twice.

Throttle position has a lot to do with it. Your prolly only using maybe 15% to 20% throttle to cruise at 60, so its very efficient at thos speeds.

Also, fuel cut off is at 7250 - 7300RPM I think, thats what 909 ment with "redline" on the chart.
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Old 07-12-2006, 12:34 PM   #8
ewmatter
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Default Re: RPM at 65, 70, 75 MPH?

it looks like 909 posted speeds for the speed3....155mph is the top speed for the speed3, not your everyday 3.
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Old 07-13-2006, 03:23 AM   #9
909
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Default Re: RPM at 65, 70, 75 MPH?

[quote author=ewmatter link=topic=51301.msg818180#msg818180 date=1152722053]
it looks like 909 posted speeds for the speed3....155mph is the top speed for the speed3, not your everyday 3.
[/quote]

That chart is not a "Mazda 3 speed chart" It's a mathematical chart based on gear ratios and tire size. It just happens the input I used was the specs of the 3. We use charts like this when determining gearing changes, tire size changes, etc... The original post was asking if there was a problem with her 3 beacause it rev'd so high at highway speed. If your clutch is slipping it can be a problem but how do you know for sure? Easy, look at the chart. If your engine RPM doesn't match the mathematical answer then there is slippage somewhere. The chart does not imply the car goes 800 MPH, or that the engine revs to 8k freely. Please don't interpret it as such.

When you're in 1st gear and floor it, the rev limiter will kick in eventually preventing you from grenading the engine. This is an electrical kill to the spark. When you're in 4th and hit 118MPH and you're not at the ignition limiter, the top speed limiter kicks in and it kills fuel, these are 2 different limits, remember rev=spark and speed=fuel.
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Old 07-13-2006, 03:34 AM   #10
909
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Default Re: RPM at 65, 70, 75 MPH?

[quote author=4cylDriver link=topic=51301.msg817680#msg817680 date=1152705833]
A few questions, are those numbers the mph corresponding to the RPMs. If so how come if the rev limiter is at 7K why does the top speed stop at 119.

Also when it comes to fuel milage i was checking the speed vs the RPMs and in 5th gear they all seem identical. So is speed and RPM not a good judgement of fuel.* Does the car burn more gas at higher RPMs.

Example, which statement is more true

the car burns twice as much gas at 4000 RPMs than it does at 2000 RPMs
the car buns less than twice as much gas at 4000 RPMs than it does at 2000 RPMs
the car burns more than twice as much gas at 4000 RPMs than it does at 2000 RPMs.

This is considering cruising RPMs, no acceleration. Just driving on a flat grade and maintaing speed.
[/quote]

There is no statement there about efficiency in there. All internal combustion engines operate at different efficiency ratings at different RPM's. The efficiency does have alot to do with RPM, cam timing, throttle position, and load. Any answer to efficiency based solely on RPM would be completely innacurate at best.

Example: A car running at 1500RPM into a 20 MPH head wind, with 4 flat tires, and 4 passengers weighing 350lbs each would use the same amount of fuel as the same car running at 6000RPM on flat ground doing 110MPH with 1 150lb driver and no head wind. (this is all made up BS anyway so don't think I actually calculated this!!)

According to your question above and ignoring the variables the same car would use an equal amount of fuel running at 1500 RPM as it does at 6000 RPM.
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