Turning up power. Pros and cons

Well some of these replies will teach you to ask a mechanical question here again won't it?

It's all gear ratios. Not just the rear either, you can have an overdrive gear for 10th or 13th and that helps too.

That's why Schneiser has there trucks spec'd with like 2.68 ratio or some crazy thing.

I had a Cascadia with 3.36 gears / 10 speed and it would run at 70 mph at about 1500 rpm. Top speed was 94. DD15 / 455 HP. Would get just over 7 mpg cruising in the low 60's over lots of mountains, but wasn't anything to write home about.

My current truck has An ISX 450 HP with 10 speed / 3.58 ratio. Milage is about the same, maybe even a touch better.

It's how your able to roll taking the hills as well. If your in 55 mph states, and you get a good head of steam going into a hill, so your power is up, we'll if bear is hungry that day, you're F.

So you need to be geared to the place you plan on running as well.

If you're mostly a flatlander, get a set of those 3.08's, or 2.60's.

Almost all the autos have like a 2.80 or 2.60 final drive, cause of the gearing in the tranny.

Those trucks with those super tall ratios are real weird when starting out though lol.

It's simple math. 100 RPM a minute less means 36,000 little bursts of fuel not going into the engine. 6 cylinders x 100 x 60 seconds.

Lot's of guys will tweak, and use a marine application injector. This uses even more fuel. A richer fuel burn results in lower Temps than a lean burn.

I pass the "Big Hammer's" all day long on the hills. Just cause I'm not that heavy. So I always like to start the fight of "The Big Hammer" got passed by Casper The Friendly Cummins Powered Cascadia, what's the point of having the Big Hammer lmfao.

 

Because not everybody wants to tug around a dump trailer locally driver. And 25%? No thanks. I'll stick to my 33% hauling frac sand.

 

Not all "fuel bursts" are created equal. Running an engine at 1500 rpm with the truck parked needs 4,500 injections of a tiny amount of fuel every minute. Running 1500 rpm with 35lbs of boost needs 4,500 injections of everything the injector can put through it.

 

Yes. Just trying to keep it basic. Without getting into the curve & usage & demand lol.

 

Dont ya love it when some failed owner operator tries to convince the rest of us that we should sell our trucks and get a company job.

 

That's a question for @superhauler. I'd wager that he would respond the same way I am:

No one made the truck I wanted. I bought this truck to run Canada and the Territories and whatever. It was the model I wanted, the sleeper I wanted, the engine I wanted (2WS), the wheelbase, the rear ends, but a 475 3406 with a 18913A. I wanted an 18, but I got the big 13. The transmission was the only thing that wasnt the right spec. I wanted double the original HP. When the transmission grenaded, I went with the 22918B.

Until the Bugatti Veyron, no one made a factory 1000HP car. No one makes a 1000HP car for under $2mil. No one makes a 1000Hp truck. If someone made a 1000hp truck, how much would it cost? You can build a 1000HP car for much cheaper than you can buy them. The same goes with trucks. Buy an old truck, and build it to your specs.

"But Six, how can you put invest $100k into an old truck?"

I've been in this truck for 10 years. That's $10grand a year for a truck that performs well and is a joy to drive. Have you ever driven a truck that's a joy to drive? Mash the throttle and hear that turbo spool and she pulls, regardless of what you have on the wagon? I get paid to play with my toys and I dont have to take my clothes off to have fun.

 

I’ve got a 2018 Volvo currently with the iShift and 3.08 rears.. great flatland truck as it’s turning 1450ish at 75. Pulls hills decently too if I flip it to Performance+ mode but MPG certainly suffers. A 3.36 or 3.58 would help it all around with power and MPG...

But back to OPs question, you should be able to turn it up to 450 at least but it depends on the rest of the driveline as others have mentioned. They wouldn’t turn the ISX up passed 450/1650 in my previous truck due to driveline limitations. You won’t see a decrease in RPM but you’ll see an improvement in pulling power and less effort to maintain cruising speed.

 

Now I'm not a mechanic by any means. Buy when I was thinking about turning up my hp from 430 to 500-550 (how ever high it could go) I was told I first had to change turbo and something else. When the shop asked why I wanted more. I told them same thing you said. They told me I DON'T want more hp, I want more TORQUE. They looked at my drive line and saI'd ok. I was lucky it was just enough (something??) Had to wait a week for something from detroit. Pulled me into shop plugged in computer. And when I pulled out WOW what a difference. I don't go faster, my rpm are about the same 12 when I used to cruise at 14. My fuel mileage is the same. But man now I pull thru PA on 76 and80 without dropping any gears, or shutting off cruise.

 

Thre are a lot of things you can do to improve the efficiency and driveability of a truck. But before you start throwing money at it you really need to educate yourself on the mechanics and fundamental physics.

Now I'm not saying you got to be a full fledged mechanic that can rebuild an engine, but you need to have an understanding of how things work together.