Cruise Control - High RPMs on hills

Toyota isn't the only manufacturer that has this issue and it's been around for at least a decade or two. RPM's are kept low cruising as low RPM = better fuel economy. Vehicles are geared to take advantage of that so ANY hills result in a drop down and higher RPM's. It's certainly worse now then before but I don't use cruise when I want fuel economy. I could pull at least 3 MPG better highway fuel economy 20 years ago in my Dodge if I used my go pedal and not the cruise going and coming back from Silver Lake. It was just hilly enough that it shifted and killed economy. If I used the go pedal and some smarts I could almost always stay in top and OD just by picking up a little speed downhill and easing up going back up.

The first time I really watched it I was pretty shocked at how much cruise killed mileage in your typical 4x4.

I'll add this. I have a new [2020] work vehicle, 2500 Ferd. That dang thing will jump to 4-5K all the time as soon as it hits a hill. I was far happier with my V8 GMC and the new Ferd has more engine rattles and knocks at 12K then my GMC had at almost 250K miles.

 

When the post started it said 5300 rpm, it's been changing ever since. There's a video of someone's truck running at 5500 rpm going over a hi-way overpass. Like that's normal.

 

So you "don't need a big ass half ton" yet you have 3 2nd Tundras..... Which are big ass half tons.

 

Don't need a big ass half ton, so I got a big ass 3/4 ton. Gasser, worse fuel milage then any Tundra made.

 

Congratulations! Discovering this officially makes you a Tacoma Owner! And yes, it happens to everyone who uses cruise control. If you REALLY want to feel bad about it, then have your ECO display on which shows gas mileage. Then, when you start up one of those hills, and the gears downshift, you will see your mileage drop like a ROCK down to the around 10mpg range until you crest the hill. The best thing you can do with your new truck, is to go easy on the gears, when driving around town and when getting on the freeways. Take your time, as the transmission is a "learning" transmission. I was careful with mine, and that is why I am getting insanely great gas mileage, for the truck, both around town and on the freeway.

 

Our interstates here are 80 MPH, plus hills, and wind. I don't mind the taco for flat, windless driving. Occasionally it will shift every 30 seconds when the wind is blowing. I try to just turn up the radio and not pay attention but it is annoying. I drove an f150 yesterday, on a stretch of road where the tacoma can't maintain speed the f150 stayed in 9th gear. It was amazing.

 

Not to high at all. The only downside is lower fuel economy.

 

You understand this engine has been around since long before the Tacoma, right? It is geared for MPG, but still makes its power at 3500 RPM. This engine has a smaller displacement than the 4.0L and still has 42 more HP.

I guess I'm not sure what people are doing to their trucks. I had cruise set at 70 today, like I always do on my commute, and the truck never went over 2200 RPM

 

You must be on flat land. Any slight grade causes my truck to downshift causing the rpms to go over 3k. If its flat, of course the rpms stay around 2k or less.

 

Now go look at the RPM range where the 3.5 makes it's power VS the old 4.0. Peak HP can mean very little depending on the RPM range that the engine and vehicle typically run at. A 750 HP F1 engine isn't going to be worth a darn rock climbing even though it has a high HP rating.

 

Definitely not. I live in the hills of Michigan. On flat ground my truck will run about 17-1800.

Given that you have a 2021, it's possible that the truck is still learning.

 

I'm not arguing that. I'm saying it is NOT as detrimental as everyone is trying to make it out to be. This engine was designed to get the power there. This engine is also, at least part time, direct injected while the 4.0 is not.

 

If l remember correctly the 4.0 made peak HP about 700 RPM lower so not that big of a difference.

 

Detrimental.....ehhh, 5K RPM always produces more wear then 2500 RPM. Will you notice it the first 50 K, nope.

The 3.5 is not a BAD engine, few people say it is. It is however, a very poor match for a truck engine, especially with a transmission that is geared high enough that every steady state driving will cause it to drop out of 6th for little to no reason at normal highway speeds.

Your 3.5 has more peak HP but it isn't even 1 1/0th of a second faster in 0-60 times. That should say something right there.

Check out torque VS RPM specs also between the two engines.

The 3.5 was dumped into the Taco for nothing else then higher FE numbers in artificial driving circumstances. And it can do that VS the old VVT 4.0. [the 4.0 VVT-i would have been a FAR better choice]

 

I mean, the Taco in 6th will pull past 70mph no problem. It's people expecting V8 performance that are "having issues".

 

IDK ... I use CC all the time and while yeah it may downshift a couple gears to get up to speed with what you've set it at ...
I'd never consider 'skyrocketing' to over 3,000 RPM as ANYthing to be concerned with. 6K is redline, right?
If yer already doing 75 mph ... In CC ... Of course it's gonna downshift and RPM's going up, on an incline, because you told yer truck you wanna keep going 75 mph. I think you're worrying too much. I've found the cc on my 2020 2.7 to be perfectly acceptable.
In fact I think it works very, very well.
Besides ... you gotta rev the engine way up every now and then ... Gotta keep the grasshoppers burned out of the cylinders y'know ..

 

Saying this is a "poor match for a truck engine" is pretty weak, to be honest. EVERY manufacturer uses engines across multiple platforms. My Mustang growing up had a 3.8L V6 which could also be found in the Ford Windstar and Ford Ranger. The 5.0L can be found in the Mustang and F150. The Pentastar V6 from the Wrangler is also found in minivans. I could go on and on. What you match it with is what makes the difference.

The "issue" with these trucks is gearing, not the engine. The 3.5L makes 42 more HP than the 4.0L, but the 4.0L is faster off the line. The 3.5L is geared for MPG. Nevertheless, it was designed from the factory to run the RPMs that it runs. Again, it is direct injected (part time) while the 4.0 is full time port injected. Change the gearing and you have an entirely different truck.

 

It's still the engine output at normal driving RPM ranges and application including gearing that is way to tall for non boosted engine output at normal truck RPM ranges. Now toss a turbo or two on it and you now have something completely different as the engine can produce more HP and torque at a lower RPM because it can move more air then a non boosted engine of the same displacement at the same RPM. Engines, when you break them down, are merely big ass air pumps that move air that has had fuel added to it, compressed and ignited. That's it.

 

I hope you're right. I have only 1k miles on it now.

 

Yeah, give it some time. Granted, I'm running 70 and not 75, but still. 35k is alarming at first, but the engine is designed to sustain that if necessary. I just like to make sure the truck is up to temp (or close) before pushing it if I can.