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Re: cruising rpm
[Re: Kern Dog]
#1567189
01/24/14 12:45 PM
01/24/14 12:45 PM
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Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
pro stock
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pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
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Quote:
Quote:
Someday I hope to go the GV route or Kiesler 4 speed auto but not in the budget now, sadly. 
Uhhh... GOOD luck with that Keisler thing....
Ummm does this mean their tranny is not as good as advertised? I know it is quite a bit of money but I did like the idea of the lower 1st gear to give some more ommphh to the 3.55's I have now. Oh well, I guess I will need to do some more research as to what path to go down here. I was thinking the A518 route but not wanting to butcher my tranny crossmember to squeeze it in.
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Re: cruising rpm
[Re: Wyle E Coyote]
#1567190
01/24/14 12:50 PM
01/24/14 12:50 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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Quote:
I've heard from a few engine builders that the "optimum" RPM for efficiency is the spot where the HP and Torque curves cross.
I do not know where you heard that gem, but ALL engines have their tq and hp curves cross at 5250 rpm, all of them. That is the nature of the formula that derives HP from TQ at a given RPM.
As for the RPM, drove San Diego to Memphis, N50's, 4.10's, three speed stick. 70+ mph most of the way, sometimes more, others less. 3500 rpm.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: cruising rpm
[Re: cjskotni]
#1567191
01/24/14 02:08 PM
01/24/14 02:08 PM
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Joined: Nov 2004
Posts: 1,708
S. Il. U.S.A.
5spdcuda
top fuel
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top fuel
Joined: Nov 2004
Posts: 1,708
S. Il. U.S.A.
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Keisler has filed for bankruptcy and is no longer in business. I don't have any personal knowledge or experience with their 4-speed auto trans, but some may be available used. You may wish to look into a Gear Vendors add on to your 727. The Gear Vendors unit does result in a shorter driveshaft and somewhat more severe driveline angles as the rear axle moves up and down, but your wheelbase is probably long enough for it not to be too big of an issue.
Last edited by 5spdcuda; 01/24/14 02:13 PM.
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Re: cruising rpm
[Re: can.al]
#1567194
01/25/14 01:53 PM
01/25/14 01:53 PM
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Joined: Nov 2010
Posts: 3,696
jersey
Spaceman Spiff
master
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master
Joined: Nov 2010
Posts: 3,696
jersey
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3.73's and 275/60/15 had no problem turning 3,500 to 4,000 most of the way to Carlisle.
526 cubes of angry wedge, pushbutton shifted, 9 passenger killer!
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Re: cruising rpm
[Re: Supercuda]
#1567196
01/25/14 03:03 PM
01/25/14 03:03 PM
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Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
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Quote:
Quote:
your maximum lo speed torque must be your cruise rpm for efficiency.
..short duration cams should be more efficient at a lower rpms than long duration cams.
I know that, but that is not what the poster stated. He stated cruise RPM should be where HP and TQ curves cross, that is 5250 for all engines, all cams, all whatever.
also, would not peak torq at part throttle occur at a lower rpm? I don't set the cruise at wot!
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Re: cruising rpm
[Re: can.al]
#1567198
01/25/14 03:38 PM
01/25/14 03:38 PM
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Joined: Apr 2012
Posts: 18,880
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RSNOMO
Moparts Torchbearer
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Moparts Torchbearer
Joined: Apr 2012
Posts: 18,880
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Quote:
what would you say is an acceptable rpm to cruise at for an extended trip?
..would 2800 - 3000 be pushing it on a 2 or 3 hour period?
Ran 85 M.P.H.+ in the 'Power Tour' for 100+ miles in the past...
440 in front of 3:23's...
That was an extreme...And the sweet-spot...
All things considered out there today, run the 3:23's...
Why buzz the engine???
And why limit yourself???
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