1990 Ford Bronco 5.8 351w
 

I was wondering what all the potential ways to increase my mpg and horsepower without spending 5000$

Welcome to FTE and the Big Bronco Forum. We will do our best to get you the most accurate info we can.

Anything to help it breathe easier... Exhaust restriction is one of the key shortcomings of these trucks. Intake isn't quite as bad so, better flowing exhaust would be a good beginning. Don't get too carried away though... about 3" single is really good sizing. If you want to spend a little more, consider headers and don't let the old-school guys try to convince you that long tubes are the only way to go. Short EQUAL LENGTH work really well and some even bolt in as direct replacements for stock manifolds. They aren't inexpensive but are worth the investment if you want to "wake up" the engine.

A good tune up never hurts. Consider a good set of ignition wires and a strong coil. Pull fault codes just to make certain there isn't anything stored in the memory that the computer may be trying to compensate for. If you get more than Code 11 or 111 chase down and fix the problem(s).

Avoid things like throttle body spacers and mystery additives. The majority of the CAI's on the market are crap because they pull air from under the hood...where its already hot. Research has proven that the stock intake plumbing is better and if it is insulated a bit, really gains efficiency.

Others will no doubt chime in as well. Again welcome.

If you want to improve MPG in a Bronco, WALK.

I appreciate the info and will definitely look into everything you said. Right now it has flowmaster 40's but the stock cat would I get a big power boost by completely removing the cat or purchasing a high flow cat? Also, a buddy of mine has a supercharger at his tow lot which would fit in my engine bay, would a 351w with stock injectors be able to handle a supercharger? Thanks again for the response

No itd run lean with stock injectors. You're forcing more air into the chamber, gonna have to add more fuel. You don't wanna remove a functioning cat, replacing it wouldn't be a bad idea tho.

Smillie, the first step to get better mileage out of these trucks is actually finding out which MPG numbers are you getting from it right now. A tune-up, fuel injector cleaning and some sensor replacing might be in order. Pretty much maintenance stuff and a soft foot on the pedal will give you a better mileage.

tell us more about your rig, is it stock or lifted with large tires? how many miles are on the motor. has it been tuned up recently?

A properly functioning catalytic converter is completely passive. Changing cats won't yield any change unless the one that is in the truck now is clogged.

It's all stock with 146xxx miles on it and it was tuned up around 7 months ago but since then ive put 7000 miles on it so I was thinking of redoing all wiring spark plugs oil and such. Anyone know what some performance wires and plugs would run and if its safe to put royal purple 5w 30 oil in?

so would i end up losing gas mileage by supercharging?

Supercharging? that would require quite a lot of work (and expensive at that) and would surely hurt your MPG.

I'm not really worried about the work I am just confused about superchargers. If more air=more combustion out of the gas moving through engine wouldn't that end up using the most gas efficiently?

you have to compensate for the extra air, which is what bigger injectors are for, also a good set of head gaskets. I know 5.0's were notorious for blowing head gaskets when adding super chargers, not sure on the 351s though, but still something to consider.

You aren't worried about the work yet you stated you didn't want to spend $5000... Now i'm confused... With the extra air you would need a Mass Air Flow system instead of the Speed Density you have to begin with, if you do this yourself with junkyard parts it will cost anywhere from $200 to $600, if you buy a MAF kit it's around $1100 - $1500. New and bigger injectors (getting a clue as to why would you require BIGGER injectors?), probably replacing internals or even rebuilding the engine, a supercharger (the only cheap one that comes to mind is a junkyard unit from a Vortec, and i don't think you want to go down that route), a kit for a supercharger... well, it could cost even more than a mint condition Bronco... And at the end you'll have a truck with a lot more HP/TQ but that consumes a lot more fuel to do so.

The supercharger/turbo way works economically with a small displacement engine which gains the capabilities of a bigger engine without reaching its consumption numbers. It might or might not be reliable, and junkyard parts surely won't help with this.

If you want a very economical truck, the mod you should consider is dropping in a 4BT Cummins diesel engine. It will requiere some fabbing but you will get the best results going that way.

like Encho said your talking an expense when going with a SC on a motor with that many miles. not to mention the efi system on your rig wont work at all either because the computer cant be tuned.

I wouldnt run royal purple on a motor with that many miles. just stick with a 10w30 or 10w40 oil. only use motorcraft or purolator oil filters. NO FRAM
run motorcraft or autolite copper plugs, get some ford 9mm plug wires and get a good quality cap/rotor. bump the timing up to 12* BTDC. then start looking into exhaust upgrades.

From perspnal experience the best power upgrades for this motor that will work with the existing EFI and fuel systems are a cam swap and a full exhaust system that includes headers. You will see pretty healthy power increases across the board and there is potential for increased fuel milage as well when you're not using the new horsepower.

A supercharger system can be added to the truck that doesn't require larger injectors or a different/tuned computer, it uses a FMU(vacuum sensitive valve) in the fuel return line to raise fuel pressure across the injectors under boost thus forcing more fuel through with each injector pulse. This system again has the potential to deliver improved fuel economy when you're not using that extra horsepower(just using the extra low rpm torque), but as with most supercharger systems this doesn't come cheap.. usually costing $3-5k. In comparison the cam and exhaust upgrade could be done for as little as $500-$800 and while it won't quite produce the same gains it's be a nice step up from what you have now.