Cavalier Engine RPM spreadsheet

[Nick R]

So since my car does not have a tachmoeter, I wanted to know that in 3rd gear (with TCC locked) how fast the engine is spinning. My logic is explained in the spreadsheet. The 3T40 has a 3.58:1 final drive ratio and a 1:1 3rd gear ratio. The tires in this size (P195/65/R15) make about 850 Revs/ mile. I was alittle bit... Surprised, especially by the 75MPH speed.

 

[Colt45ws]

Are you counting the chain drive?

 

[HighRpm]

i would get a tach 40 bucks and its urs sun tach is 1 my saturn goes to 3k rpm at 60-65

 

[simple_gifts]

The spreadsheet, the 21st century calculator but 200 times the cost. j/k

 

[Nick R]

Originally Posted By: Onmo'Eegusee
Are you counting the chain drive?


I didn't see anything anywhere about the chain ratio, I'm assuming that it is the "final drive" ratio in this case.

 

[Colt45ws]

Yeah, it counts against it. A 3.58 diff does not exist from what I can find so it must include chain reduction.

 

[Quattro Pete]

Originally Posted By: rudolphna
I was alittle bit... Surprised, especially by the 75MPH speed.

Surprised in what way? That the rpm was so high or so low, considering a 3-speed trans?

By the way, your numbers seem about right. Here's an online calculator for things like this...

http://www.kabamus.com/garage/gears.html

 

[Nick R]

Originally Posted By: Quattro Pete
Originally Posted By: rudolphna
I was alittle bit... Surprised, especially by the 75MPH speed.

Surprised in what way? That the rpm was so high or so low, considering a 3-speed trans?

By the way, your numbers seem about right. Here's an online calculator for things like this...

http://www.kabamus.com/garage/gears.html


Wow...

oh well I feel better because I did it myself, lol.

And so high! 3800RPM for extended periods of time seems like it should be pretty tough on the engine.

 

[eljefino]

Forget the tach, get a scangauge, you seem like you'd like to play with something like that.

"They" say you can run most motors at 80% load at 80% max RPM near forever. My old mazda 323 used to run 4k RPM on the highway, it was just geared short that's all.

 

[BobFout]

3800 RPM, or 75 MPH, is really nothing. You could drive full-tilt for hours and hours and days and days and not phase the engine. (This assumes proper fluids and maintenance). These are modern engines!

 

[Quattro Pete]

Originally Posted By: rudolphna

And so high! 3800RPM for extended periods of time seems like it should be pretty tough on the engine.

Not necessarily... these engines were designed to rev high. Driving with such constant speed on the hwy is actually easier on the engine than typical city driving with frequent speed changes.

FWIW, our Jetta turns at about 3500 rpm at that speed, despite having a 4-speed box. Same for my old A4 1.8T - and that was in 5th gear (manual).

 

[Nick R]

Originally Posted By: eljefino
Forget the tach, get a scangauge, you seem like you'd like to play with something like that.

"They" say you can run most motors at 80% load at 80% max RPM near forever. My old mazda 323 used to run 4k RPM on the highway, it was just geared short that's all.



I'd love a scangauge. But two problems.
1. Cost. Scangauge is almost $200, alot of money for me right now. Maybe later
2. Don't scangauge only work with later model cars? I don't think my cavalier supports all the gizmos. Unless someone knows otherwise. For example, my car does not have a digital odometer, it is the old fashioned scroll wheel style, and there is no trip odo.

 

[John K]

In the old days, when I had an MG Midget,1964, same as AH Sprite, it turned 4000 rpm @ 60 mph. I drove it from Cincinnati to New Orleans once and ran it at 85 mph a lot of the time, which was about 5000 mph, or higher, I think. Later I had a head on it that was milled 90 thousands, and it would pull 6000 rpm in 4th, for an indicated 100! Had trouble finding gas of high enough octane, it would run on a lot when the ignition was turned off. British sports car were known for the 4K @ 60, it seems to me it wasn't until much later that there were cars like the 240Z that combined a more reasonable rpm at cruising.....

 

[Colt45ws]

Scangauge works 1996+ with few exceptions...
I had one of the original ScanGauges in my 1998 Cavi...

 

[Quattro Pete]

http://www.scangauge.com/support/CompatibleVehicles.shtml

 

[Nick R]

It will show engine RPM, oil pressure, coolant temp, fuel consumption, all that nice stuff?

 

[Colt45ws]

Not oil pressure, but everything else, yes.

 

[Nick R]

See, I was under the assumption that the ECM in the 2.2L was pretty primitive

 

[Colt45ws]

By todays standards, yes. It would not have the power to run TBW, VCT, etc etc. But its still OBD-II and thus the SG will be able to pull all that.

 

[eljefino]

It'll show whatever you have a sensor for. If the PCM doesn't know tranny temp or oil pressure, scanguage doesn't know either. Also showing engine temp to the degree is a great way to find a dampened/ neutered dash gauge.

My generic ebay OBDII code reader/ data scanner, at $45, shows RPM but of course the readout is not particularly user friendly.