Explain why the 4x4 and 4x2 would not get the same mpg until you switch to 4x4?

You would think they would get the same mpg, maybe because the 4x4 is a little heavier or geared different.

 

More component's to turn, more load on the engine

 

Front axle drag seems like the biggest issue imo. I assume that it is because the days of getting out in the mud to turn the front hubs to the lock position have given way to the convenience of running the front axle full time.

My first regret that front hubs are no longer part of the deal is that when I tow up a steep hill on pavement it would be nice to use low range and not have the front tires engaged on hard surface. Also the hit that mileage takes is huge...

Then again I do not know if this new generation runs the front axle continuously but I assume so...

 

Weight also makes a difference.

 

weight makes a big difference.

 

Does anyone know what the weight difference is 4x2 vs 4x4?

 

This is based off the 2015s but a 4x2 Prerunner V6 DCSB curb weight is 3985. The same truck in 4WD is 4220.

 

Again on the 2015s, but a 2wd access cab 4 cylinder 5 speed comes in at 3615 pounds and a 4wd access can 4 cylinder 5 speed weighs in at 4030 pounds.

 

Wait, how does it add only roughly 200lbs in the V6 but almost 400lbs in the 4banger access cab?

 

You know, I was setting here trying to figure that out myself. But that info comes straight from Toyota's website. Which on a side note, Im really shocked they havent updated the site to show the '16 Tacoma.

Heres the link:


http://www.toyota.com/tacoma/features.html#!/weights_capacities/7113/7513/7594/7188

 

Front Diff, transfer case, drive line, front half shafts et al I expected to be in the 350 to 400 lb range so 200 lbs seems low although I am not complaining if that is the case.

 

2016 4x2 vs 4x4 is approx 250lbs depending on model.

 

Getting back to the mileage issue, how much would you expect the weight (similar to 1.5 to 2 passengers) effect the gas mileage and do you think the weight is the main reason for the difference?

 

Probably the simple answer is because no one should trust the weight numbers on the web for Toyota, they all typically refer to some fictitious configuration they build two units a year of...

But my guess would be that in the comparison made I think for the I4 it is a 5 lug vs a 6 lug while for the V6 it is 6 lug vs 6 lug. The I4 comparison is probably picking up the extra 200 lbs in moving from a 5 lug suspension to a 6 lug - but I could be wrong about whether that I4 configuration is a 5 lug or not.

EDIT: Indeed - if I change the comparison on the I4 to be with an AT so that we can do a 4x2 prerunner to 4x4 comparison the weight difference is now just 240 lbs. If I leave it at AT and select the 4x2 to not be a prerunner then we go back up to a 400 lb difference. I'm going with the original comparison for I4 was 5 lug 4x2 against 6 lug 4x4.

 

Well it depends on whether you are talking highway or city, but we can make an estimate using an online calculator.

Using this site:

http://ecomodder.com/forum/tool-aero-rolling-resistance.php

And putting rough figures similar to a Tacoma:

4000 lbs, Crr .011, Cd 0.4, A 30 sq ft, and defaults for the rest of the values we get 20.31 mpg at 65 MPH with drag being 75% aero drag (which would be independent of weight). So likely the difference for 200 lbs is not a lot. Lets try...

Same parameters as above but weight at 4200 lbs gives us 20.06 mpg at 65 MPH. So for highway, essentially little or no change. But of course for city things would be more complicated since you are accelerating that additional mass a lot rather than just dealing with a minor increase in rolling resistance from the weight.

Fortunately this is a question lots of people have had, and some Googling will get you this study:

http://www.drivealuminum.org/research-resources/PDF/Research/2008/2008-Ricardo-Study.pdf

Which on page 29 has the results for weight reduction on a vehicle very roughly similar to a Tacoma (its a more efficient small SUV but of the same chassis weight as the Tacoma). There a 200 lbs increase in weight took city mileage from 21.2 to 20.9. Looking across multiple other vehicle configurations in the study that's usually about the size of it, 200 lbs will change mileage by about 0.3 MPG for vehicles getting similar mileage to the Tacoma.

 

Weight

 

+1, but difference is small. My current Tacoma gets the same MPGs as my 2009 Prerunner. Even in the old days with locking hubs MPGs were lower due to weight and drag.

 

2015 2nd gen specs per toyota build site PDF's

5-lug axle 2wd AC 2.7L weight: 3615
6-lug axle (prerunner) 2wd AC 2.7L weight: 3810
4x4 AC 2.7L weight:4050

 

You are turning an extra gearbox (transfer case) in the 4x4 and pushing the CV axles. I just got finished converting my truck to 4x4. There is a huge difference in how easy the wheel spins without the CV axles installed.

But having said that, I still get exactly the same gas mileage as before my conversion.

 

This is a question? Is there no science before posting?