98 4.0 to 2.5/smaller engine

Karcastic · Apr 14, 2014

Hi,

I have a 1998 Mazda B4000 2WD auto trans, that I would like to put a smaller engine in as I commute with little extra weight. I can find donor trucks for around 500 but I'm wondering what new would cost too. I just have no idea what my options are at all really, any help/thoughts would be greatly appreciated.

Big thanks

RonD · Apr 14, 2014

Since most would want a larger engine, I think your best option would be to sell/trade the B4000 for a 2.3l/2.5l Ranger or Mazda

Rowdy Fitzgerald · Apr 14, 2014

I agree with Ron. Too much work for less power. Just trade it in or sell it.

Karcastic · Apr 14, 2014

I think that's a good idea too but I thought it's the cheapest route being I would not have to deal with insurance change/possible increase, taxes and emmissions/safety testing. Plus I would hate to part with my truck.

Is the downgrade too difficult? What's involved exactly?

Thanks everyone

adsm08 · Apr 14, 2014

Many times, if you sit down and add up the cost of the swap, vs the potential fuel savings, it takes a very long time just to break even, let alone see any significant savings.

Karcastic · Apr 15, 2014

Ok, I though there would be more beneficial options for me. Guess I should just work on improving my 4.0

Thanks again guys

Will · Apr 16, 2014

If you drive a 4.0 as if it were a 2.5 you might get the same mileage. Just because a 4.0 CAN burn more fuel doesn't mean it has to. It has almost twice the torque, which means you probably accelerate at twice the rate and burn twice the fuel, even when you aren't trying. I drive like this--put my foot down just enough to get it moving and let it build up speed on its own. I adjust my routes to avoid places where I have to accelerate quickly. If you can't do these things, a 4.0 will always get worse mileage. A 4.0 can't accelerate at a spectacular rate, but it can accelerate much harder than a 2.5. It will burn more fuel if you drive them both with the same attitude. It's the same truck and if you hook a rope to it with a stress gauge on it, it takes a certain amount of force to haul that truck down the road at a given speed. The difference between the motors if you spun them with an electric motor and measured the resistance while they weren't running would be small. The thing that matters is how much torque the driver demands of them. Torque is dictated by the amount of fuel consumed during one combustion event. A 4.0 makes much more torque because it can burn much more fuel in a rotation than a 2.5. You have to drive purposefully slow to match the 2.5 average mileage, but you can do it.

Karcastic · Apr 22, 2014

Will said:
If you drive a 4.0 as if it were a 2.5 you might get the same mileage. Just because a 4.0 CAN burn more fuel doesn't mean it has to. It has almost twice the torque, which means you probably accelerate at twice the rate and burn twice the fuel, even when you aren't trying. I drive like this--put my foot down just enough to get it moving and let it build up speed on its own. I adjust my routes to avoid places where I have to accelerate quickly. If you can't do these things, a 4.0 will always get worse mileage. A 4.0 can't accelerate at a spectacular rate, but it can accelerate much harder than a 2.5. It will burn more fuel if you drive them both with the same attitude. It's the same truck and if you hook a rope to it with a stress gauge on it, it takes a certain amount of force to haul that truck down the road at a given speed. The difference between the motors if you spun them with an electric motor and measured the resistance while they weren't running would be small. The thing that matters is how much torque the driver demands of them. Torque is dictated by the amount of fuel consumed during one combustion event. A 4.0 makes much more torque because it can burn much more fuel in a rotation than a 2.5. You have to drive purposefully slow to match the 2.5 average mileage, but you can do it.

Thanks Will

98 4.0 to 2.5/smaller engine

Karcastic

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