nix4x4

I was reading on a local 4WD forum that a guy saw an increase of 48 horsepower and 77 ft-lbs of torque from his chevy 350 just by increasing the fuel pressure from 42 psi to 50 psi. I think that his numbers are way exaggerated, but is increasing fuel pressure really a good way of increasing power?

nix4x4

Nobody wants to touch this one, huh?

chroad

How would you do it?

stormin94

I just can't see how you would get more horsepower out of more fuel PSI... that doesn't make sense...something stinks here... .....Horsepower is increased by airflow, and exhaust flow, for the most basic terms. Torque is increased by increasing compression, or displacement, in basic terms. Upping your fuel pressure does neither of those, so it doesn't make sense. But if it does work, tell me, and I'll be sure to do it. I'd kill for an extra 44 horsepower from my good ol 3.slow.

chimmike

He's full of crap.

the only time upping pressure makes power in any vehicle without any other mods is in turbo diesel vehicles.

Increasing fuel pressure without adding air to compensate makes zero power. Matter of fact, he likely LOST 40hp and is getting 40% worse fuel economy from doing that.

chimmike

Rule of thumb:

There is no such thing as free horsepower. Don't let anyone tell you there is, because they're lying.

Ignition timing doesn't increase power as much as it does throttle response, but it requires you use higher octane fuel to prevent detonation.

An old saying I used when I was doing the fast car thing:

"Horsepower costs money; how fast do you wanna go?"

mt_goat

It is true IF the engine is running too lean because of inadaqute fuel pressure that boosting the fuel pressure (or flow really) will not only give the engine more HP but will protect it from melting down. Running too lean will melt a valve or piston and your best power will come from running slightly rich (12-13 A/F)

This is a problem mainly with trucks that have added a supercharger or turbo that wasn't on the truck from the factory. The pressure can best be boosted by going to a bigger fuel pump but there are gadgets like "boost a pump" that just force the stock pump to spin faster (not a good idea).

I'm running a Walbro 190 fuel pump on my 93 for just that reason.

FredTJ

HP and torque is 100% directly related.
You can not increase (or decrease) one without a direct increase (or decrease) in the other.




Fred

FredTJ

Actually it is possible to increase power by increase the fuel pressure.
Y'all that are getting all twisted up about this concept are making an assumption (an invalid one at that) that the engine is burning all of the fuel introduced into it and burning it efficiently and that's simply not the case.

You can increase power by increasing the amount of available fuel, that is the fuel that's introduced into the combustion chamber, that is burned.

The finer the droplets of fuel that's introduced are, the more of it (and better) will burn because of the increased surface area of the total fuel change.
You can decrease the droplet size by installing somewhat smaller injectors and/or by raising the fuel pressure.

This is done pretty often in some types of racing and it works.

Increasing fuel pressure, in and of itself, does not particularly lead to increased fuel consumption as the computer (via input from the O2 sensor, etc.) will adjust the amount of fuel introduced into the chamber by shortening the injector pulse rate.

What we end up with is pretty much the same fuel load but "vaporized" to a larger extent, which leads to more efficient fuel burning and less waste.




Fred

stormin94

I understand that, and probably should have included that in my original post. Correction noted.