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Who's modded a TBI system and GAINED MPG?
- Thread starter 88K5Jimmy
- Start date
DPI
1/2 ton status
I did. It's called a HONDA! 
Check out cfm-tech.com I have heard a lot of good things about them and I just bought a bunch of stuff from them but have'nt recieved it yet, i will post up when I get everything put on.
Zeitler
Registered Member
read somewhere that raising the fuelpressure would increase mpg , but it doesent make sense dumping more fuel in an engine would make you gain mpg..
DPI
1/2 ton status
88K5Jimmy said:
Not yet. Been busy with the new job and working on the upstairs of the house...
How is school going?
PhoenixZorn
1/2 ton status
Zeitler said:
Adding fuel pressure doesn't necessarily add more fuel, just the force with which it comes out of the nozzle... basically, the force of a garden hose through a drinking straw... the garden hose only shoots about 2-3 feet if unimpeded, but if you put all that water through a straw, it will shoot a good 20 feet or more... The same amount of water is coming through the straw as the hose (in an ideal environment) it just comes out faster and with more pressure behind it.
I think your analogy isn't quite right. Sure the hose shoots further, but you are restricting flow (building pressure) to get that to happen. Same as putting your finger over the end of the hose...the amount of water let out is less because you are restricting flow. Sure, that's building pressure, but you've decreased the size of the outlet to accomplish this.
In an injector, the amount of "on" time doesn't change at a given point, and the orifice of the injector doesn't change, so you end up solely with more pressure, which allows more fuel to be injected in the same amount of time.
A better analogy would be turning the water up via the faucet. Pressure and velocity increases, thus so does the total amount of water coming out, at least up to the point when the municipal water pressure is equaled, or the hose flow capacity is exceeded.
In an injector, the amount of "on" time doesn't change at a given point, and the orifice of the injector doesn't change, so you end up solely with more pressure, which allows more fuel to be injected in the same amount of time.
A better analogy would be turning the water up via the faucet. Pressure and velocity increases, thus so does the total amount of water coming out, at least up to the point when the municipal water pressure is equaled, or the hose flow capacity is exceeded.
loafer
1/2 ton status
Given the same injector pulse width(how long the injector is open for) Increasing fuel pressure will increase the amount of fuel that is discharged from the injector.PhoenixZorn said:
The advantages of higher fuel pressure come from better fuel dispersion from the injector, which leads to better fuel atomization. You can increase your fuel pressure a little bit on a stock system and let ECU compensate for it by means of the O2 sensor, but if you go too far you will be out of the range that the ECU can decrease fuel by feedback from the o2 sensor.
If you have a tunable ECU, or you have your ECU reprogrammed you can increase the fuel pressure to the limits of your injectors and fuel delivery system.
Zeitler
Registered Member
does anyone know if a TBI engine shuts of the injectors when just coasting down a hill? cuz i know most modern carengines do if the rpm is above 1400 or so..
