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Re: cruise rpm: how low is too low?
[Re: feets]
#819312
10/04/10 07:56 PM
10/04/10 07:56 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
No problem with your post.
1wild is suggesting that buzzing around at a bazillion rpm is going to do wonders for mileage.
no, you are simply stuck in the box your build and won't recognize other's examples.
Feets, you are kind of being a dk about this.
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Re: cruise rpm: how low is too low?
#819313
10/04/10 08:02 PM
10/04/10 08:02 PM
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Joined: Jan 2003
Posts: 28,068
Irving, TX
feets
OP
Senior Management
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OP
Senior Management
Joined: Jan 2003
Posts: 28,068
Irving, TX
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1wild, are you really a 16 year old or do you just play one on the net?
I gave you my example. The hot rod's torque curve really lit up around 3000 rpm and peaked at 4900 AT WIDE OPEN THROTTLE.
I got my best mileage cruising between 2300 and 2400 AT PART THROTTLE.
What you seem to forget is that the higher speeds induce higher drag. Stick your hand out the window at 30 mph and try it again at 80 mph. I bet you'll feel a difference. The car feels the difference too.
Now either play nice or go away.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: cruise rpm: how low is too low?
[Re: feets]
#819314
10/04/10 08:10 PM
10/04/10 08:10 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
1wild, are you really a 16 year old or do you just play one on the net?
I gave you my example. The hot rod's torque curve really lit up around 3000 rpm and peaked at 4900 AT WIDE OPEN THROTTLE.
I got my best mileage cruising between 2300 and 2400 AT PART THROTTLE.
What you seem to forget is that the higher speeds induce higher drag. Stick your hand out the window at 30 mph and try it again at 80 mph. I bet you'll feel a difference. The car feels the difference too.
Now either play nice or go away.
You need to recognize what 'stay in the cam range' means.
You ran with it looking for a flaw in a 'generalized statement'
WHEN DID I TELL 'YOU' TO CRUISE AT A GAZILLION RPM?
I DIDN'T, SO YOU NEED TO PULL YOUR 'FEETS' OUT OF YOUR MOUTH. 
playing??? is that what you do on here?? 
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Re: cruise rpm: how low is too low?
[Re: feets]
#819318
10/04/10 08:47 PM
10/04/10 08:47 PM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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How low is to low?? I think the engine will let you know. It will depend on the cam , comp and cubes and weight. If I remember correctly my 5.4/330 CI motor F150 cruises at about 1800 to 2000 RPM with 3.31 gearing at 65 MPH Its fine on the flat and mild grades before it needs to down shift. A 440 CI motor set up similer should be able to cruise at even a lower RPM. But, Like I said, the engine as set up will let you know. As far as motor Efficiency goes. They are most efficient per CI at there max torque RPM. The Problem with that. Is that these cars are Grossly overpowered. At Max torque you could be making 500# plus easy on a near stock 440. Burning All kinds of fuel in its efficent max torque rpm. Again the problem, We need very little torque compared to what these engine can produce to say, Cruise at 65 MPH So with a resticted throttle the engine itself may be in a less efficient per CI, it is in a Far more efficient state in reguards to fuel consumption. A restricted throttle reduces volumetric efficiency per CI, making it run like a Smaller motor. Technically if the fuel to air ratio stays inline, and it does. The motor isnt in efficient at all. It just runs like a fuel efficient smaller motor. mike 
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Re: cruise rpm: how low is too low?
[Re: Sport440]
#819319
10/05/10 12:35 AM
10/05/10 12:35 AM
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Joined: Mar 2008
Posts: 390
kentucky
superbyrd
enthusiast
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enthusiast
Joined: Mar 2008
Posts: 390
kentucky
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i for years ran a 73 charger with this combo.....
318,wieand action plus,out of the box holley 600,mopar orange box and distributor,36 degrees total timing,manifolds,2 1/4" duals with h-pipe,40 series flows,full length exhaust,833 aluminum overdrive 4-speed,performance clutch,8 3/4" rear with 2.94 gears and sure-grip. 215/70/15's on 15X7 cragars. drove this car 3 times to columbus to the nats,(1000 mile round trip) got 23-25mpg running 75-80 mph. tached 1800 rpm at 75 mph. car pulled hills just fine. was it a powerhouse throttling up at 70mph in overdrive?? no. thats what i had a 4-speed for.if someone is trying to figure out how to keep a sizeable amount of power,while still in a higher gear,and low cruise rpm,i say,stop being lazy and downshift already. i'm not sure what "lugging the engine" at low rpms would be entailing,i mean,fire trucks,cop cars,and wreckers do it all day long sitting still.pulling alot of amps,pumps,etc.just my 2 cents......
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Re: cruise rpm: how low is too low?
#819320
10/06/10 04:45 PM
10/06/10 04:45 PM
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Joined: Oct 2010
Posts: 46
Can.
Hellrico505
member
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member
Joined: Oct 2010
Posts: 46
Can.
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Hi there, Long time reader-first time posting. I'll give my .02. I spent tremoudous amoung of hours on dyno and test track doing SAE test and stuff. What I suggest, do a highway test. Find yourself a portable tank that can be weighted(5gallon is good and a good weightscale) At cruise speed, switch tank and time record for 1/2 hour ride. make the ratio for pound of fuel/hrs. This will provide you with all energy loss while running at cruise speed. Do it a couple of time, to see if it repeat. Volume is innacurate, weight is much better. If you have acces to a rolling dyno that measure fuel rate, O2. You could install vacuum gauge, exhaust gas recorder or other. Spin the dyno at 65 MPH at a steady RPM. Measure fuel rate without load, that will give fuel rate needed for all the vehicule resistance component(tire, axle, trans, engine). Keep it steady at 65 mph and then start to load until it lug (or your assumption of lug, should be at kickdown point). Make sure you measure increment of fuel rate vs hp during that session(as futur reference). Example: without load: 5pounds/hrs +10HP : 5.1 pounds/hrs +20HP: 5.2 pounds/hrs, etc. Deduct no-load-dyno-fuel-rate from highway-fuel-rate. This give you aerodynamic resistance fuel rate and front tire rolling resistance. Now, since you are still attach to the dyno(caus you did the highway test before going on the dyno), take the highway-fuel-rate, load the dyno to that fuel-rate, keep the fuel rate steady(or dyno load) and reduce dyno rpm until it lug. Prepare to be suprise how deep it will go. If you go that route (deeper RPM) it will downshift more frequently than before. Other point to consider. if per example, you find that it could do confortably 65mph at 1500RPM, the engine may lug if you go 75mph at 1700RPM, 85mph at 2000rpm. Energy demands is sqareroot of speed. As far as future number increment test. If you ever do a modification on the car(change tire, synthetic lube, different rearend, manual trans, overdrive, procharger, etc) you will be able to compare the improvement on your next dyno visit. If you don't have acces to dyno, there are other way(hitch and BIG camper), but poorly accurate. Even dyno result can be questionnable(don't ask). I did that countless time with class 8 truck. Fuel(gas, nitro, diesel, E85, Hybrid) is energy, regardless of what it does.  Rej
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Re: cruise rpm: how low is too low?
[Re: Hellrico505]
#819321
10/06/10 05:28 PM
10/06/10 05:28 PM
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Joined: Jan 2003
Posts: 28,068
Irving, TX
feets
OP
Senior Management
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OP
Senior Management
Joined: Jan 2003
Posts: 28,068
Irving, TX
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That's a great way to do some testing but I'm not going to buy several different ring and pinion sets to do that over and over.
I was trying to get a general idea.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: cruise rpm: how low is too low?
[Re: OzHemi]
#819325
10/06/10 08:03 PM
10/06/10 08:03 PM
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Joined: Jan 2003
Posts: 28,068
Irving, TX
feets
OP
Senior Management
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OP
Senior Management
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Posts: 28,068
Irving, TX
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That's part of the building process. Step one of the mechanical bits I believe.
1) get a car
2) put stuff on it
3) cuss the car
4) kick the car
5) throw stuff at the car while hopping around on your good foot
6) fix stuff you broke while upset with the car
7) dream of driving the car some day
8) cuss car
9) fill car with gasoline
10) strike match
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: cruise rpm: how low is too low?
[Re: 1_WILD_RT]
#819326
10/06/10 11:43 PM
10/06/10 11:43 PM
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
Rick_Ehrenberg
top fuel
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top fuel
Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
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Quote:
[is your enemy for efficiency.
<snip>
 Care to explain what this means??? For many years vacuum gauges were mounted in cars & labeled as an "Economy Meter" & you seem to feel vacuum is bad??? Please explain...
One of the 3 main reasons that diesels get better MPG is the lack of a throttle = almost no vacuum, lots less pumping losses.
(The other 2 are higher CR and more BTUs per gallon of fuel).
Back to the Imp: Will this be carb's or SMPI? (I hope it is the latter).
Rick
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Re: cruise rpm: how low is too low?
[Re: Rick_Ehrenberg]
#819327
10/07/10 01:00 AM
10/07/10 01:00 AM
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Anonymous
Unregistered
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Anonymous
Unregistered
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20.1-1 comp, a power band of idle to 4000rpm, 20 somthing speed tranny with 2 speed rear...
and the cruise rpm is...... like I said, in the cam range.
It IS still apart of the total equation of optimal gas milage.
it all add's up... and anyone denying that needs to start over.
Rick...will even you deny this?
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Re: cruise rpm: how low is too low?
#819328
10/07/10 04:47 AM
10/07/10 04:47 AM
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Joined: Apr 2010
Posts: 10,570
Sunny South Florida
Golden-Arm
I Live Here
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I Live Here
Joined: Apr 2010
Posts: 10,570
Sunny South Florida
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Quote:
btw...your mom mini van gets better mph, gears aside, BECAUSE THE CAM ONLY OPERATES IDLE TO 3800RPM!!!!!!!!!!!!!
DUHHHHHHHHHHHHH
so, the engine shuts off, at 3801 rpm? seems to me, the cam operates at any speed, the engine is operating at. have i missed something here? if the cam doesnt operate over any specific rpm, the engine would shut off. perhaps you meant something else, but were too busy yelling? 
"When Tyranny Becomes Law, Rebellion Becomes Duty"
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Re: cruise rpm: how low is too low?
[Re: Golden-Arm]
#819329
10/07/10 06:13 AM
10/07/10 06:13 AM
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Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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Quote:
Quote:
btw...your mom mini van gets better mph, gears aside, BECAUSE THE CAM ONLY OPERATES IDLE TO 3800RPM!!!!!!!!!!!!!
DUHHHHHHHHHHHHH
so, the engine shuts off, at 3801 rpm? seems to me, the cam operates at any speed, the engine is operating at. have i missed something here? if the cam doesnt operate over any specific rpm, the engine would shut off. perhaps you meant something else, but were too busy yelling?
come on guys. knock it off. you're arguing semantics now! anyone with a 3rd grade education knows what he meant! let's avoid picking on each other, and debate the actual topic on hand instead of nit picking using proper english. this is an internet forum, not a college masters paper
**Photobucket sucks**
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Re: cruise rpm: how low is too low?
[Re: feets]
#819330
10/07/10 12:12 PM
10/07/10 12:12 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
I'm back on the Imperial planning thing again. 
With a stock or very mild 440, what is a reasonable cruise rpm that will return the best mileage on the highway and not lug the engine down?
I'm talking about moving over 5,000 lbs of car at 65 mph. The originally came with 3.23 or 2.94 gears. They would turn 2500 rpm at 65 mph but were sluggish around town.
I plan on dropping a 3.73 gear out back and sliding my 518 OD in the car. That will be equivalent to a 2.54 gear.
Those gears will have the engine spinning 2,000 rpm at 65 mph. Will a mild 440 have the torque at those speeds to pull that heavy of a car?
Disregard my turbos. They will not make any difference at cruise.
I remember when we dropped the TKO in the 440+6 RR with a 3.54. It got better mileage at 75 mph than it did at 65 mph. The engine was lugging at the lower speeds. The carbs could have used a little attention. That car weighed about 3900 lbs.
When I had the 833 OD and 3.23 gears in the hot rod it would pull 75 mph at 1800 rpm and 90 mph at 2200. That was using stock heads, the 236*/.474" and 232*/.483" cam, and a 3800 lb car. In this case the engine didn't feel like it was doing any work until 2700 and over 110 mph.
I know the smallish ports on a RB will help keep port velocity up compared to other engines. However, they're not going to be the same as some of the late model engines turning lower speeds in lighter cars. The 9:1 or lower compression I'm going to run won't help.
I won't be able to get away with 1600 rpm at 65 mph like the LS1 cars.
I fired off an email last week to Comp Cams to get suggestions for a bump stick but haven't heard anything back yet.
FWIW, my '96 ram was 4700 lbs w/o me. it had an NVG3500 (.73 OD, IIRC) 318 magnum, cat back, open element air filter, and MP computer. rear gears were 3.21 with 31" tall tires. 75mph was 2000 RPM. rode down the highway fine and pulled fine from 60MPH in 5th.
I think the key is wide LSA and moderate duration to keep overlap and potential cam surging down....
another comparison, a friend has a '96 impala SS with 3.73's or 4.10's (can't remember which) and a T-56, it's 4200-4300lbs w/o driver, the engine is a 396CID LT1, with a comp hydraulic roller in the 230@.050 range, and it goes down the freeway at 70 mph in 6th just fine...lower than that he does get a little bit of surge in 6th...
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: cruise rpm: how low is too low?
#819331
10/07/10 12:27 PM
10/07/10 12:27 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
This actually makes no sense because the cams "power range" is only at WOT, no one cruises at WOT unless you have a slant six in a dump truck. All new cars cruise at a much lower RPM than the peak TQ because they get the best MPG at a lower RPM. People just say this beause they want an excuse to drive fast, I however don't need any excuse, I just drive fast because it's fun
You are mistaken, it's called torque...ya know that thing that comes on when you get into the power band of the cam...
While it's true that lower rpms typically net you more mpg, it's also staying in the torque curve/power curve/band or whatever you decide to call today..
As in ...if your mill has a cam advertised 3000-6500, you are better off reving inside of 3000 than 2000 rpm.
Ever have to down shift and stomp on it to get up that hill?
you wouldn't be mashin the pedal if you were in the usable power range to begin with.
ahh you'll figure it someday. 
uhh, again, the torque/HP peaks you usually see are based on WOT....run a dyno sweep of the motor at 1/2 throttle and see if the HP and tq peak RPMS change....
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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