testing the 4.10's
#11
05-10-2011, 12:02 AM
I was thinking that the 87 octane SCT performance tune was not the best for towing. But even when I didn't have the tune, the engine was a dog under load up a hill. I had a 1996 with the mopar PCM (5.2, 3.55 gears) and it too was the same way. But it seemed that the 5.2 was a better towing vehicle. Even with 33 inch tires.
But I can say that I had better gas mileage NOT in OD than I did IN OD.
UR, you are correct. 2200-2400K RPM with 4.10 gears is 60-70 MPH. But I was talking about air fuel mixture due to the increase of pressing down on the gas pedal. I don't want to be a dick here, but when you press your foot down on the gas pedal, it causes the throttle cable to move the butterflies on your throttle body to a more open position. That increases airflow into the intake. An increase in airflow causes a lean condition (albeit for a split second) and then your PCM compensates by adding more fuel. SO, with how the gas pedal works out of the way, you CAN stay at the same RPMs with the throttle body open at different positions. Thus causing different AFR readings depending on the load.
You are right in what you said, but we were talking apples and oranges. So trying to disprove my "apples" to your "oranges" is a dick move.
But I can say that I had better gas mileage NOT in OD than I did IN OD.
UR, you are correct. 2200-2400K RPM with 4.10 gears is 60-70 MPH. But I was talking about air fuel mixture due to the increase of pressing down on the gas pedal. I don't want to be a dick here, but when you press your foot down on the gas pedal, it causes the throttle cable to move the butterflies on your throttle body to a more open position. That increases airflow into the intake. An increase in airflow causes a lean condition (albeit for a split second) and then your PCM compensates by adding more fuel. SO, with how the gas pedal works out of the way, you CAN stay at the same RPMs with the throttle body open at different positions. Thus causing different AFR readings depending on the load.
You are right in what you said, but we were talking apples and oranges. So trying to disprove my "apples" to your "oranges" is a dick move.
Last edited by CPTAFW163; 05-10-2011 at 12:24 PM.
#12
05-10-2011, 01:07 PM
Hall Of Fame
The only time overdrive saves you fuel is when the engine is just loafing along. This is true of every overdrive in every vehicle that has one.
I don't mean to come across as a dick here: The better take-away from your little experiment would be: When there's a significant load in or behind the truck you should try to cruise at 2200-2400RPM where the engine more efficiently makes power.
I don't mean to come across as a dick here: The better take-away from your little experiment would be: When there's a significant load in or behind the truck you should try to cruise at 2200-2400RPM where the engine more efficiently makes power.
From what I notice when pulling if I stay around 2000-2200 RPM's I get good power and good mileage, however the motor might feel like it's luggin. Regardless, I just gutted the CAT's and installed a new Magnaflow but I haven't started to pull yet.
Before I was getting 5.5 - 6.5 pulling a 9000 travel trailer with the 3.55 gearing, I haven't pulled only once with the new Yukon 4.10's but not enough to tell you what I'm getting. Like I said, I got to do some figuring before I can be certin.