4.56 gears and fuel economy
#41
RE: 4.56 gears and fuel economy
If the large diameter tire you put on a Ram pickup
has 'High Rolling Resistance'
and most aggressive tread 'mudder tires' do
then changing the gearing is not going to get you back to the same MPG.
A large diameter tire slightly lifts the truck higher
this lets more air travel underneath the rough underside of the truck
and the drag of the air get worse.
In addition,
a large diameter tire 'sticks out more' from the enclosed fender well
and more of it hits the air,
this FURTHER makes the aerodynamic drag worse.
There are large diameter tires specially built by the tire companys to roll easier.
These are the 19.5 diameter commercial truck tires.
These 19.5 tires and their ability to improve MPG is thoroughly written up in the
Cummins Ram Diesel forums like TDR and DTR
Today with the 125 day supply of new Ram pickups sitting idle at the dealerships
it is easy to find out what differential gear ratios do to highway MPG.
Find a dealership and salesman that will let you and friends/wife/son/brother
'convoy' a few Rams on the same highway at the same speed in the same weather conditions.
Compare 4.56 equipped Power Wagon
to 3.55, 3.73, 3.92 and 4.10 Ram pickups.
If you want to be accurate ballast them to the about the same curb weights by choosing which person/child goes in what Ram.
You are not doing anything that Dodge engineers have not done before.
Out in the Western USA and during winter in Canada
you can see future years Rams traveling in convoys to test them out.
These Rams are equipped with computers and sensors recording thousands of readings
- including MPG - second by second.
has 'High Rolling Resistance'
and most aggressive tread 'mudder tires' do
then changing the gearing is not going to get you back to the same MPG.
A large diameter tire slightly lifts the truck higher
this lets more air travel underneath the rough underside of the truck
and the drag of the air get worse.
In addition,
a large diameter tire 'sticks out more' from the enclosed fender well
and more of it hits the air,
this FURTHER makes the aerodynamic drag worse.
There are large diameter tires specially built by the tire companys to roll easier.
These are the 19.5 diameter commercial truck tires.
These 19.5 tires and their ability to improve MPG is thoroughly written up in the
Cummins Ram Diesel forums like TDR and DTR
Today with the 125 day supply of new Ram pickups sitting idle at the dealerships
it is easy to find out what differential gear ratios do to highway MPG.
Find a dealership and salesman that will let you and friends/wife/son/brother
'convoy' a few Rams on the same highway at the same speed in the same weather conditions.
Compare 4.56 equipped Power Wagon
to 3.55, 3.73, 3.92 and 4.10 Ram pickups.
If you want to be accurate ballast them to the about the same curb weights by choosing which person/child goes in what Ram.
You are not doing anything that Dodge engineers have not done before.
Out in the Western USA and during winter in Canada
you can see future years Rams traveling in convoys to test them out.
These Rams are equipped with computers and sensors recording thousands of readings
- including MPG - second by second.
#42
RE: 4.56 gears and fuel economy
ORIGINAL: HemiBuell
AirRam, I agree correctly calculated gears are very important and overlooked when people modify vehicles.
I have a question for you. In one of the previous posts you say that lower rpm's can burn more gas when under load.
Are you saying that at a given RPM, say 1500 RPM's, the motor burns more fuel when pulling a trailer or going up a hill at 1500 RPM's versus driving down a flat road at 1500 RPM's?
How does the fuel injection know to burn more fuel because the truck is under load versus unloaded at the same RPM. Doesn't the truck just sense engine RPM, air temp, air flow....
Only thing I can think of is reading a pressure from the tranny, but even then there are so many variables between tangent force to the ground at the tire and pump pressure in the transmission.
AirRam, I agree correctly calculated gears are very important and overlooked when people modify vehicles.
I have a question for you. In one of the previous posts you say that lower rpm's can burn more gas when under load.
Are you saying that at a given RPM, say 1500 RPM's, the motor burns more fuel when pulling a trailer or going up a hill at 1500 RPM's versus driving down a flat road at 1500 RPM's?
How does the fuel injection know to burn more fuel because the truck is under load versus unloaded at the same RPM. Doesn't the truck just sense engine RPM, air temp, air flow....
Only thing I can think of is reading a pressure from the tranny, but even then there are so many variables between tangent force to the ground at the tire and pump pressure in the transmission.
This experiment will help you gain an understanding on what effects fuel economy. Lower the load on the vehicle at any given RPM and your fuel economy will improve…
SPEED SAFE, AIR RAM
#43
#44
RE: 4.56 gears and fuel economy
ORIGINAL: HemiBuell
I wouldn't call using the overhead very scientific. I thought you had some actual engine management knowledge to share.
I'm still not convinced but I do understand why it would happen.
I wouldn't call using the overhead very scientific. I thought you had some actual engine management knowledge to share.
I'm still not convinced but I do understand why it would happen.
Let me try again...
ORIGINAL: HemiBuell
In one of the previous posts you say that lower rpm's can burn more gas when under load.
Are you saying that at a given RPM, say 1500 RPM's, the motor burns more fuel when pulling a trailer or going up a hill at 1500 RPM's versus driving down a flat road at 1500 RPM's?
In one of the previous posts you say that lower rpm's can burn more gas when under load.
Are you saying that at a given RPM, say 1500 RPM's, the motor burns more fuel when pulling a trailer or going up a hill at 1500 RPM's versus driving down a flat road at 1500 RPM's?
ORIGINAL: HemiBuell
How does the fuel injection know to burn more fuel because the truck is under load versus unloaded at the same RPM. Doesn't the truck just sense engine RPM, air temp, air flow....
How does the fuel injection know to burn more fuel because the truck is under load versus unloaded at the same RPM. Doesn't the truck just sense engine RPM, air temp, air flow....
Your computer controles the A/F ratio through information gathered by several difference sensors... one of them is the throttle positioning sensor..… If you hit a hill going 60MPH@2200RPM and your throttle position is approximately 10% open buy the time you reach the top of that hill your throttle position will have to be open much more (30%-40%) to maintain that the same speed you hit the hill at… Your speed has not changed and as long as your transmission did not down shift your RPM’s would have stayed the same… but that additional throttle allowed more air and fuel in… which was needed to maintain the 60MPH@2200RPM speed/RPM..
When you set the cruz speed to say 60MPH@2200 and start heading up hill... the truck will eventually start to bog down due to the weight of the truck vs. the incline of the hill, the PCM will since this loss in set SPEED and open the throttle % to maintain the set speed. If you where heading down hill it would not requior the same throttle position and would close the throttle % to maintain the set speed… Going up hill you can still maintain the same SPEED/RPM but you need to give it throttle to maintain it. As long as the transmission does not downshift you will maintain the same SPEED/RPM going up this hill... so in OVERDRIVE SPEED and RPM go hand in hand. When the hill becomes too great to overcome with just adjusting the throttle position % the transmission will downshift into a lower gear which will add the needed torque to overcome the hill… but this also causes the RPMs to go through the roof.
A good example how the load effects actual throttle blade % while maintaining the same SPEED/RPM…. …. If you ever set your cruz control and lightly place your foot on the peddle to let it “RIDE/FOLLOW†the peddle movements controlled by the PCM you will notice that although you have set the speed to 60MPH@2200RPM’s you will feel the peddle go down and up in an attempt to maintain the same speed... each time the peddle goes DOWN you use more fuel... each time the peddle goes UP you use less fuel... Its the same principal here.
I hope I was able to help you understand how it knows to add more fuel… Throttle blade positioning would be the answer to your question…
ORIGINAL: HemiBuell
Only thing I can think of is reading a pressure from the tranny, but even then there are so many variables between tangent force to the ground at the tire and pump pressure in the transmission.
Only thing I can think of is reading a pressure from the tranny, but even then there are so many variables between tangent force to the ground at the tire and pump pressure in the transmission.
SPEED SAFE, AIR RAM
#45
RE: 4.56 gears and fuel economy
ORIGINAL: HankL
Find a dealership and salesman that will let you and friends/wife/son/brother
'convoy' a few Rams on the same highway at the same speed in the same weather conditions.
Compare 4.56 equipped Power Wagon
to 3.55, 3.73, 3.92 and 4.10 Ram pickups.
Find a dealership and salesman that will let you and friends/wife/son/brother
'convoy' a few Rams on the same highway at the same speed in the same weather conditions.
Compare 4.56 equipped Power Wagon
to 3.55, 3.73, 3.92 and 4.10 Ram pickups.
And on a side note, you guys are making this thing waaaaaaayy to complicated.
#46
#47
RE: 4.56 gears and fuel economy
ORIGINAL: stripper
That seems about right. How long have you had them in?
You like them over your factory gears?
Brad
ORIGINAL: dodgetk81
I have a Powerwagon with 4.56 And the factory 33" tires. Its a 5speed auto and Im getting 11.0 MPG city/highway.
I have a Powerwagon with 4.56 And the factory 33" tires. Its a 5speed auto and Im getting 11.0 MPG city/highway.
That seems about right. How long have you had them in?
You like them over your factory gears?
Brad
#48
RE: 4.56 gears and fuel economy
magnethead,
go check the official curb weights on the Ram Power Wagon
better yet, weigh one for yourself
it is not a 8000 lb truck with the 5.7
http://www.trucktrend.com/roadtests/..._overview.html
Note my suggestion to ballast all the trucks in the convoy to about the same weight.
If you use your search button
you'll see that I advocate trying do comparable tests whenever possible,
including swapping two tires between trucks so that the 'average' tire loads are the same too.
If you don't think that a Dodge dealership salesman
wouldn't agree to let you swap tires between Rams,
then you don't realise that A REALY GOOD salesman
wants to learn things too,
including everthing possible about Rams & MPG.
For a salesman, the MPG problem with pickup trucks is a HUGE issue right now and the good ones want to be able to advise not only their current possible customers - they also want to be able to give good advice to PAST customers.
If the salesman who sold your Ram to you 3 years ago
gave you simple tips about how to improve your MPG
and the tips worked,
how would you feel about that salesman
the next time you were shopping for a vehicle?
There are new car salesman who try to trick customers
and there are also salesman who try to help the customers however they can,
including making sure they get good repairs and financing.
Speaking of ballasting trucks,
did you know that if you coast a truck down a steep hill
at least at three different weights
it can tell you things about the truck
(aerodynamics, rolling resistance, drivetrain loss, top speed)
that otherwise would take millions of $ of equipment?
go check the official curb weights on the Ram Power Wagon
better yet, weigh one for yourself
it is not a 8000 lb truck with the 5.7
http://www.trucktrend.com/roadtests/..._overview.html
Note my suggestion to ballast all the trucks in the convoy to about the same weight.
If you use your search button
you'll see that I advocate trying do comparable tests whenever possible,
including swapping two tires between trucks so that the 'average' tire loads are the same too.
If you don't think that a Dodge dealership salesman
wouldn't agree to let you swap tires between Rams,
then you don't realise that A REALY GOOD salesman
wants to learn things too,
including everthing possible about Rams & MPG.
For a salesman, the MPG problem with pickup trucks is a HUGE issue right now and the good ones want to be able to advise not only their current possible customers - they also want to be able to give good advice to PAST customers.
If the salesman who sold your Ram to you 3 years ago
gave you simple tips about how to improve your MPG
and the tips worked,
how would you feel about that salesman
the next time you were shopping for a vehicle?
There are new car salesman who try to trick customers
and there are also salesman who try to help the customers however they can,
including making sure they get good repairs and financing.
Speaking of ballasting trucks,
did you know that if you coast a truck down a steep hill
at least at three different weights
it can tell you things about the truck
(aerodynamics, rolling resistance, drivetrain loss, top speed)
that otherwise would take millions of $ of equipment?
#49
RE: 4.56 gears and fuel economy
If you are buying gears strictly for a possible MPG gain consider this. It will typically take you over 50,000 miles to even recoup a typical gear gear change cost assuming you gain 1 mpg. Also consider that people who do put down the money for any mod are more likley to exagerate the benefits. The CAI and 180 thermostat threads are other prime examples.