Howdy folks.

I know just enough to be dangerous when it comes to motors. Reworked a 72 Nova 350-with a lot of knowledgeable help-and restored a couple old Honda motorcycles.

I've been mulling around some HP upgrades for my 2000 Durango R/T, but experience with my 93 Honda Magna gives me pause.

I bought my Magna with 8k on the clock. Previous owner installed V&H exhaust as well as a new carb kit. Supposed to gain an extra 10 HP or so.

Problem is, those extra 10 ponies move the power curve up, make a high-strung bike even more so and really weakens torque at lower RPM.

One of the things i enjoy about the 5.9 is the big torque on tap, pretty much right from idle. Will HP mods kill the bottom end the same way they did on my Magna?

I realize this is comparing a 5.9 L V8 to a 750cc motorcycle, but motors are motors, most HP increases come from more efficient breathing and exhausting of the motor.

For those who have swapped intake manifolds, throttle bodies, headers etc. for more horsepower, did low RPM torque suffer?

Best,

Heekma

 

any mod to the intake or exhaust flow is not really making more horsepower or torque, it is just shifting the powerband around to favor one or the other in a specific range, so in general i fyou shift the powerband UP the rpm range to gain hp you will loose low end torque and vice versa if you shift it for low end torque you will loose peak hp

 

Nevermind.

 

as a mechanical engineer who has spent some time studying this stuff, all the information i share on the topic is accurate, you are shifting the torque/hp curves, hp going up typically means that you have shifted the curves UP the rpm range and hence make more power, while adjusting the curves some to meet the new peaks, while there are exceptions here that is the most basic idea behind it.

also because hp is not a truely measured number it is just calculated (your equation is correct) that means that torque is what you should really to looking at when talking mods. In this case we are talkinga bout simple bolt on mods, it will not create any significant increase or decrease in torque with either exhaust or CAI or anything else you can bolt on. Technically more air = more fuel = more power, but only if it is burningn all the fuel and this will also cause a drop in MPG.

 

Yeah in order to shift that curve bolt ons really don't do much. Now a new cam can do that but that is a whole other topic for another day.

 

correct, bolt ons give you very minimal changes

 

anything you learned on any brand other than a chrysler toss out. mopars are work different than other brands. just my idea. after years of having mopars.

 

True different brands tend to respond similarly, but different with some things. I grew up around gm, had some friends that were die hard ford guys, and I ended up on mopar.

Now here is a definition on hp and torque I learned, it may be a over simplified but here it goes, torque is how much work can be done and hp is how fast you can do the work. That is why a 5.9l with a tune/ other mild parts can have as much torque as a new hemi, just way less horsepower. This is because the 5.9 is set up for low end torque around 2600-3600 rpm vs the hemi at like 3400-4400 rpm. Producing more torque when the engine is going faster means you can do more work faster meaning more horsepower. The only ways to change this is low end work and heads. The most important part of this though is the cam. It defines when and where a motor produces torque. All the components of a motor must be mated to each other but this is a basic explanation.