RPM's at 80 MPH
#46
Ok, bumping this one. Sorry I didn't get to it sooner, but here's my results from monitoring with the laptop:
RPM @ 80 MPH - Dash shows 2875 ECM says 2925
Here's the odd part though, the speedometer is dead on 80, and I checked the GPS, also dead on 80, but the ECM says 76-77![Dunno](https://g35driver.com/forums/images/smilies/dunno.gif)
Why would it read that speed and then put 80 on the dash
I guess I would rather it that way then the other way around, ECM had the right speed but the dash was wrong, that would suck.
Oh yeah... 03.0 G35 Sedan, 5AT w/ 215-55-17
RPM @ 80 MPH - Dash shows 2875 ECM says 2925
Here's the odd part though, the speedometer is dead on 80, and I checked the GPS, also dead on 80, but the ECM says 76-77
![Dunno](https://g35driver.com/forums/images/smilies/dunno.gif)
Why would it read that speed and then put 80 on the dash
![Confused2](https://g35driver.com/forums/images/smilies/confused2.gif)
Oh yeah... 03.0 G35 Sedan, 5AT w/ 215-55-17
#47
Join Date: Apr 2009
Location: Tallahassee, FL (or thereabout)
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^ Most of the cars I've driven are like that. My last Trans-Am was the closest and it was still 1-2 off. My Mom's Suburban is about 5MPH slow.
But my G is completely dead on at 80. Confirmed by my cell phone's GPS, my Dad's Garmin, and a couple of Radar 'your speed is' signs. But the crazy part is even though the needle on the dash is dead on perfect, it's not really displaying what the car 'thinks' it is running. When the Dash says 80 and the GPS says 80 the car's ECM is showing 76 or 77, which is just strange to me. On my last car the ECM read the same speed as the dash. In my cousin's Bonneville he has the little HUD and it reads slightly less than 1mph off from the dash. Yet the G35 has 3-4MPH difference between the computer and dash?????
I will tell you this, while the G35 is perfect at 80, the speedometer becomes increasing inaccurate after that.
But my G is completely dead on at 80. Confirmed by my cell phone's GPS, my Dad's Garmin, and a couple of Radar 'your speed is' signs. But the crazy part is even though the needle on the dash is dead on perfect, it's not really displaying what the car 'thinks' it is running. When the Dash says 80 and the GPS says 80 the car's ECM is showing 76 or 77, which is just strange to me. On my last car the ECM read the same speed as the dash. In my cousin's Bonneville he has the little HUD and it reads slightly less than 1mph off from the dash. Yet the G35 has 3-4MPH difference between the computer and dash?????
I will tell you this, while the G35 is perfect at 80, the speedometer becomes increasing inaccurate after that.
#49
#50
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No instrumentation is 100% accurate. All instrumentation has some level of error, even the most sophisticated.
Not to mention the human eye isn't going to perceive an error of 200RPM when accelerating your car towards redline anyways.
Last edited by liche; 12-11-2009 at 03:33 PM.
#51
The thread is regarding what rpm your car is at 80mph (has nothing to do with redline)…
You absolutely can “see” the difference in 200rmp – if your tach is sitting at 3K for example and the ECU is registering 3200 – or 2800.
As it pertains to your post – the post you responded to mentions the speedo not being accurate; you said “Who cares. . . I drive by Tach only. . . .” any logical thinking person would conclude that you meant the speedo’s inaccuracy isn’t important because you drive by tach (implying it is accurate).
If the fact that you drive by tach does not imply it is more accurate – then your own question about “what’s your point” should be asked to this post: https://g35driver.com/forums/4747686-post48.html
Your responses when you debate me are always pointless – just like your inane squabble in this thread: https://g35driver.com/forums/engine-...ance-chip.html... you aren't nearly as bright as you think you are... please be better prepared when you respond to me from now on.
#53
#55
#56
#57
Just to clear things up.
03-06 RWD 5AT Sedan (open or VLSD) - 3.3 gear
03-07 RWD 5AT coupe (VLSD) - 3.3 gear
04-06 AWD (open) - 3.5 gear
All 6MTs (open or VSLD) - 3.5 gear
Minor differences in RWD 5AT rpms in 5th at 80mph can be attributed to the following:
1) Worn tires (ie shorter)
2) Shorter tires than stock
3) Taller tires than stock
4) Torque converter locked
5) Torque converter unlocked
6) Torque converter in slip-lock
03-06 RWD 5AT Sedan (open or VLSD) - 3.3 gear
03-07 RWD 5AT coupe (VLSD) - 3.3 gear
04-06 AWD (open) - 3.5 gear
All 6MTs (open or VSLD) - 3.5 gear
Minor differences in RWD 5AT rpms in 5th at 80mph can be attributed to the following:
1) Worn tires (ie shorter)
2) Shorter tires than stock
3) Taller tires than stock
4) Torque converter locked
5) Torque converter unlocked
6) Torque converter in slip-lock
#58
Just to clear things up.
03-06 RWD 5AT Sedan (open or VLSD) - 3.3 gear
03-07 RWD 5AT coupe (VLSD) - 3.3 gear
04-06 AWD (open) - 3.5 gear
All 6MTs (open or VSLD) - 3.5 gear
Minor differences in RWD 5AT rpms in 5th at 80mph can be attributed to the following:
1) Worn tires (ie shorter)
2) Shorter tires than stock
3) Taller tires than stock
4) Torque converter locked
5) Torque converter unlocked
6) Torque converter in slip-lock
03-06 RWD 5AT Sedan (open or VLSD) - 3.3 gear
03-07 RWD 5AT coupe (VLSD) - 3.3 gear
04-06 AWD (open) - 3.5 gear
All 6MTs (open or VSLD) - 3.5 gear
Minor differences in RWD 5AT rpms in 5th at 80mph can be attributed to the following:
1) Worn tires (ie shorter)
2) Shorter tires than stock
3) Taller tires than stock
4) Torque converter locked
5) Torque converter unlocked
6) Torque converter in slip-lock
#59
Just to clear things up.
03-06 RWD 5AT Sedan (open or VLSD) - 3.3 gear
03-07 RWD 5AT coupe (VLSD) - 3.3 gear
04-06 AWD (open) - 3.5 gear
All 6MTs (open or VSLD) - 3.5 gear
Minor differences in RWD 5AT rpms in 5th at 80mph can be attributed to the following:
1) Worn tires (ie shorter)
2) Shorter tires than stock
3) Taller tires than stock
4) Torque converter locked
5) Torque converter unlocked
6) Torque converter in slip-lock
03-06 RWD 5AT Sedan (open or VLSD) - 3.3 gear
03-07 RWD 5AT coupe (VLSD) - 3.3 gear
04-06 AWD (open) - 3.5 gear
All 6MTs (open or VSLD) - 3.5 gear
Minor differences in RWD 5AT rpms in 5th at 80mph can be attributed to the following:
1) Worn tires (ie shorter)
2) Shorter tires than stock
3) Taller tires than stock
4) Torque converter locked
5) Torque converter unlocked
6) Torque converter in slip-lock
#60
http://www.caranddriver.com/features...andal!-feature