Cruising RPM with 3.73s

[95Batmobile]

Just thought I'd let everybody know, incase they were looking for a gear change.
I flow with traffic at 2,000RPM, about 60mph.
My speedo is off right now so I can't give an exact speed, but the part should be here friday to fix that [img]smile.gif[/img]
I don't see how this is going to hurt my mileage too bad now hehe

[FunkZ]

Speedo is driven off the transmission, not the wheels. After a gear change your rpm vs. speed will not change at all, you just won't be going your indicated speed.

I do ~2000rpm at 60mph with my stock 3:23's. 2500rpm is 80mph dead on.

Guys that put 4:10's in their car end up hitting the governer at 110 indicated mph before crossing the 1/4 mile mark. In actuality they're probably doing 85'ish.

What are you getting to adjust the computer for your gear change?

[95Batmobile]

Well in my car the RPM used to be about 1750-1800 at 60mph, so I am just guessing it's about 200rpm higher now since I was just flowing with traffic. It could have been 55mph at 2000rpm, I dont know. The rpm does change in comparison with speed when you switch gears... I don't know what would make you think you can cruise at the same speed and rpm with a higher gear ratio.

Do you mean it is the same until you fix your speedo? Like right now my car still shifts to 3rd at 70mph, but in reality it's about 60mph.

I got the thing from intense-racing
http://www.intense-racing.com/
Go to the ignition/electronic part and look for the "TechEdge Mini-Speedometer Recalibration controller".
It is going to be here Friday according to UPS tracking so I will let you guys know then if it works :D

[FunkZ]

Yes, it will read the same until you fix your speedo. As I said, the speedo is driven from the transmission, not the wheels. Your engine, trans and driveshaft might all be going an indicated 60mph, but with the higher gear ratio, the rear axles are turning slower than before.

[AlienInv8r]

Posts like this make my choice harder everyday. I had just about decided to stay with 3.42s rather than 3.73s since I'm always on the highway. But dang! 60@2000rpms isnt bad at all. How's your highway gas mileage? dunno if you've gotten the chance to check that out yet. Keep us informed of rpms/speed ratios after you get it corrected too.

[95Batmobile]

<blockquote>quote:</font><hr>Originally posted by AlienInv8r:
Posts like this make my choice harder everyday. I had just about decided to stay with 3.42s rather than 3.73s since I'm always on the highway. But dang! 60@2000rpms isnt bad at all. How's your highway gas mileage? dunno if you've gotten the chance to check that out yet. Keep us informed of rpms/speed ratios after you get it corrected too.<hr></blockquote>

I got the recalibrator in the mail yesterday, but the instructions aren't for a firebird :( It was dark when it got here too, so today I might go play with my car and see if I can find what these people are talking about while I can actually see the engine compartment ;)

Check my thread in the lounge too...
18.1mpg with 3.23s in the city
17.8mpg with 3.73s ;)

[Ian]

OK, on my way home from school today, i looked at my RPM's doin 80mph in 5th gear. I was at 2700 dead on.

Does this seem high for 3.23 stock gears? My car was modified when i got it, but i kind of slowly found out what stuff was done to it as i went.

Possibility for 3.42's, judging on that RPM and speed?

[Ian]

anyone?

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Ian:
...RPM's doin 80mph in 5th gear. I was at 2700 dead on.

Possibility for 3.42's, judging on that RPM and speed?<hr></blockquote>


Possibly... I have 3.42's. I turn about 1000 rpms per 30mph. 2000 @ 60, 3000 @ 90.

You were 2/3's of the way between 60 and 90.

2/3's of 1000 rpms = 667 rpms. So 2000+667 or so, yep that's right at 2700.

[Ian]

well, if i have 3.42's and dont know it, my speedo should be off right?

by how much? cause im tempted to get my car on the highway next to a friends and check.

[95Batmobile]

<blockquote>quote:</font><hr>Originally posted by Ian:
well, if i have 3.42's and dont know it, my speedo should be off right?

by how much? cause im tempted to get my car on the highway next to a friends and check.<hr></blockquote>

at 70mph mine is off by 9.1 miles an hour [img]smile.gif[/img]