6 PSI = 6x amount of fuel?

[[ion] C2]

Dumb question, but I've been pondering this, as I keep my car under 3-4k RPMs this tank of gas, attempting to see what the maximum city/hwy mileage I can get now is.

If I boost at 6 PSI, would that correspond to using 6 times the amount of fuel a normally aspirated vehicle would use? (Or maybe 7 times since 1 PSI counts as one more pound per square inch of pressure than an N/A vehicle)

Hmm?

[jackal2000]

i think not.

lets see, stock injectors flow at 22lb/hr, your theory means you would need 132lb/hr injectors @ 6psi lol

[Gr1m]

a turbo will actually increase your gas mileage unless you beat on it, it ionizes the air partices going into the engine or some bs which causes all the gas injected to burn better, and thus not wasting any which would give you better mpg. its when you beat on it that your gonna lose gas mileage

[[ion] C2]

Well if you have far more air being pushed into the cylinders, and the tune has you putting enough fuel to compensate, I thought the more air, more fuel thing would come into play

i talked to this guy who has the turbo 1.8 jetta and he gets 30MPG, lol. i haven't really checked on mine but i drive hard

[strtrydr]

From what I understand you will have to re-tune for the boost by adding more fuel but in no way is it going to be 6x

And as far as mileage goes ... on my trip to the east I got anaverage of 26MPG with my V6 ... i cannot wait until the turbo goes on.

I also have heard evidence that a turbo will actually increase you mileage IF you keep the pedal of the floor

[[ion] C2]

Originally Posted by jackal2000

lets see, stock injectors flow at 22lb/hr, your theory means you would need 132lb/hr injectors @ 6psi lol

injector flow is a max rating, lol. but still more air = more fuel, maybe not an exact ratio but it's up there i think.

i'm going to see what happens with mileage if i keep the pedal off the floor this tank, maybe a supercharger increases mileage too

[strtrydr]

I do know though for my V6 that i do NOT need to change injectors to run @ 6psi but when I go to 8psi I will have to step up the injectors to 36lb/hr.

[[ion] C2]

i'm just sayin if you're using 6 times as much air, you'd need almost 6 times as much fuel, it makes sense sort of.. lol

injector rating is a maximum number, no one runs at 100% duty cycle, unless their about to blow up their engine

[AGT]

No you have it all wrong...its 6psi missing from the tires equals 6 times more gas wasted haha j/k

What you are saying makes sense but I believe Grim has a equally confusing theory

[Vinalero]

your supercharge push the air at a 6 psi more pressure than stock, I'm no rocket scientist, but 6 times more fuel consumption would be huge, that means for the same tank of gas, you would dvide the distance you did before by 6, which is what? 30 miles? lol . Anyways, at low rpm, you probably dont boost at 6 psi as the supercharge turns with the accessory belt and it spin slower than at high rpms, where it compress the air at a higher level.

at low rpm, you wont notice much difference, even better mileage because the combustion is more complete. On high rpm however, you shoot more air in your cylinder, therefore more fuel therefore more power.

Thats my logical answer, now for technicalities, I'll pass

[[ion] C2]

right right, i'm just talking about during WOT while in boost

low RPMs i know it runs better, even better mileage, i'm just wondering about in boost

so you would use 6 times more fuel during periods when you're at 6 PSI of boost.. it's only logical, but of course you're not in boost all the time so yeah.

[DOHC_tuner]

what r u doing @ 6 psi? Up the boost or is it cause you dont have a built engine?

[Vinalero]

it doesnt work like this, its only the pressure of the air in a system that is reprensented by the 6 psi. Your tires arent 32 times bigger than flat when they are filled at 32 psi. Its only a pressure value. There is not 6 times more air getting in the throttle at high boost. Its only that instead of the engine sucking the air alone like on an N/A, the supercharge force some more air in the engine by pushing it in + the engie sucking it, so more air gets in the engine, not 6X more air.

[[ion] C2]

Originally Posted by DOHC_tuner

what r u doing @ 6 psi? Up the boost or is it cause you dont have a built engine?

i have a pulley that on a normal engine would produce 9-10 PSI, my rings are worn and boost is leaking by, what do you expect from a 176,500 mi engine lol. when i rebuild it'll spike to 10 PSI, then i'll be on meth which many have seen 13-14 PSI. of course i'll have bigger injectors than the 310cc's i have, and a custom tune.

@Vinalero: Gotcha. Also just talked to spyhunter, my theory is crap, lol.

[alerored04]

what you are not realizing is that at sea level ambient air is 14.7 psi. the 6 psi you refer to is above the normal 14.7. So following your theory you would need 50% more fuel. That is still not correct though since stock parameters run rich and there is room for more air in the stock tuning.

[DOHC_tuner]

Originally Posted by [ion] C2

i have a pulley that on a normal engine would produce 9-10 PSI, my rings are worn and boost is leaking by, what do you expect from a 176,500 mi engine lol. when i rebuild it'll spike to 10 PSI, then i'll be on meth which many have seen 13-14 PSI. of course i'll have bigger injectors than the 310cc's i have, and a custom tune.

@Vinalero: Gotcha. Also just talked to spyhunter, my theory is crap, lol.

HAha, I got a built Quad block sitting in my room ready 4 boost....but it wont see boost for a while. J/K hope you do atleast begin to rebuild the HO

[Spilner521]

Originally Posted by Vinalero

it doesnt work like this, its only the pressure of the air in a system that is reprensented by the 6 psi. Your tires arent 32 times bigger than flat when they are filled at 32 psi. Its only a pressure value. There is not 6 times more air getting in the throttle at high boost. Its only that instead of the engine sucking the air alone like on an N/A, the supercharge force some more air in the engine by pushing it in + the engie sucking it, so more air gets in the engine, not 6X more air.

You're on the right track. You don't add fuel too compensate for boost by going off how much pressure it makes, you go off how much air is being moved. A big turbo, a small turbo, and a supercharger will all pump a different amount of air at 6psi. If they were all the same at 6psi, then you could run the exact same fuel setup with the exact same amount of fuel going in whether you have a 500hp turbo or a 200hp turbo. You can't tell how much air is going in at 6psi just by saying "it's pushing 6psi", that's why you have to tune every setup differently.

[BlackJack]

interesting answers, all.....

the answer is simply this. 6psi is the amount of pressure put to your intake path in order to increase the compression when the valves close off and the piston hits the compression stroke. Your 22# injectors should handle it at 6psi, but be warned, you may get close to "going static" which is prone to happen at above 80% duty cycle.

you are not using (or needing) 6x the amount of fuel flow. If anything your IFR's can be increased by a nominal amount to keep up, but if you can afford it, I would recommend going up to 36# injectors just to be on the overkill-end of safe side. This will also prepare you for future boost increase.

your fuel requirements are going to be dictated more directly by watching your O2 readings and maintaining an optimal air/fuel ratio of 14.7 when at cruise, and as much as 11.5 when under boost. This will be evident by approximately 920-940mv from the O2 sensor.

[[ion] C2]

i have 30 lb (310cc) injectors at the moment, bigger once i rebuild, and it'll be retuned professionally

thanks for the info BJ