Question Turning down super charger, increasing mpg.

[Cobb]

I have a 97, v6, automatic, 4wd with super charger and for the most part it gets 17-18 mpg, squeals tires and sits still or does 0-60 in 9 seconds and the tranny hunts, shifts in a very unexpced and when cold not at all.

I checked with the dealer, they said I can use regular if I do not boost it since I have the meter and been on medium grade fuel with no problms. They said flushing the tranny could make it worse.

I checked the tire pressures, drive mostly highway at posted speeds and do not idle it. I have a kn filter too and the upgraded exhaust about 50k miles.

Anyway, I kept smelling gas and found the line on the pressure regulator was cracked. They said it used vacuum or boost to pinch off the return line to increase the fuel richness.

Would installing a check valve in that vacuum line making it unpinch the return help mpg?

[The Phoenix]

The injectors and fuel pump are not changed, and there is only the computer adjusting the A/F ratio. I think if you installed a check valve, it might affect normal operation.

Regardless, Superchargers actually INCREASE fuel economy if you do not keep your foot to the floor. Don't ask me how or why, but I've tested and proved this myself before/after installing an S/C on my 03 when I had it.

[Cobb]

??? I installed the valve. Its much more tamed, harder to squeal tires, yet does not run rough or sputter. It seems to shift better and easy to get 180 vs 150 miles at half a tank. Still on the same tank, so mpg has increased a lot.

[mustang67408]

Actually, I ran a vacuum /boost line from my S/C to the pressure regulator. As boost increases, it will increase fuel pressure (minimal but it did), Then when not in boost and under a vacuum it decreases fuel pressure(when its not needed). My mileage has stayed the same and as The Phoenix said it helps mpg as long as you keep your foot out of it. I drive it hard, so it didnt help the mpg, but if I drove it easier I suspect it would.

[Cobb]

Thats what I installed the valve in. There is ahose going to the fuel regulator on the fire wall on the drivers side with a tap to the boost vacuum meter. I put the check valve behind that so the regulator always sees a vacuum.

1 problem down, 1 to go. I know I put my foot in it, but its not shifting when I need it.

[The Phoenix]

Originally Posted by Cobb

Thats what I installed the valve in. There is ahose going to the fuel regulator on the fire wall on the drivers side with a tap to the boost vacuum meter. I put the check valve behind that so the regulator always sees a vacuum.

1 problem down, 1 to go. I know I put my foot in it, but its not shifting when I need it.

So if I'm reading right, you are potentially risking engine damage from keeping your fuel pressure lower when it's supposed to be higher due to boost?

The S/C'd trucks are already starved of fuel since the injectors/pump don't get swapped out. Bad idea to save a couple of bucks on gas.

[Cobb]

Right, its running leaner, however its not missing or sounding any different. I dont recall any 4 cycle engine suffering from damange from running lean. I know 2 strokes can be. Second the injectors are after the super vs before it. I know some 6 71 blowers use fuel to help cool and lube the rotors, but thats not the case either.

So far the only other side effect is the fact it takes longer to warm up even with the radiator blocked off.

Did I mention I am using regular gas and no unusual noises either? 16 gallons at 1.39 a gallon.

[mustang67408]

Originally Posted by Cobb

Right, its running leaner, however its not missing or sounding any different. I dont recall any 4 cycle engine suffering from damange from running lean. I know 2 strokes can be. Second the injectors are after the super vs before it. I know some 6 71 blowers use fuel to help cool and lube the rotors, but thats not the case either.

So far the only other side effect is the fact it takes longer to warm up even with the radiator blocked off.

Did I mention I am using regular gas and no unusual noises either? 16 gallons at 1.39 a gallon.

That's crazy..... I ran mine to richen everything up not lean it out.
I hope it works for you...Good Luck
The human ear won't hear it run lean or ping all the time, thats why they have knock sensors.
I fixed NEW TUNDRA (08) for a guy in Calif, who added a CAI and changed the muffler. He said it developed a hesitation. It did! When I hooked up the scan tool, you could watch the ECU pull out timing and remove injector timing and the truck would fall on its face, he didnt hear it pinging but it was, and it was running leaner. I could watch the fuel trim and tell.
THE FIX.. He has to run 91 octane and the problem went away on the first tank, now this truck runs like a stripped a$$ ape. The slower burning fuel stopped the pinging and richened the mixture because it wasn't retarding the timing and cutting the duty cycle of the injectors.

All I am saying is read your plugs and watch very carefully. I am glad it works...I think, still sound dangerous to me.
Good Luck

[The Phoenix]

As mustang said, good luck.

[Cobb]

I will keep that in mind. I thought I would try a few more tanks of high and mid grade fuel to test fuel economy while the price is still affordable. I have owned 2 scions an xa and new xb and its rumored the better fuel gives better fuel economy because it does not retard the timming as much, but from what you say it dumps more fuel.

Its just my daily driver to work the bugs out, then its likely being sold. Its ok, but I am just not a truck guy.

I read the toy manual you gave me a link to and it says in the tranny secion the tranny is suppose to shift as I describe my problem. THe torque converter locks at 50, unlocks under 50. I need to rig up a switch to lock it when cruzing at 40 and to unlock at or above highway speeds as I travel 95 and 64 like I own them and frequently travel 40-70 during rush hour and leaving od off just makes it too loud and having to dip below 50 to unlock it can be dangerous.

Originally Posted by The Phoenix

As mustang said, good luck.

[mustang67408]

I have owned 2 scions an xa and new xb and its rumored the better fuel gives better fuel economy because it does not retard the timming as much, but from what you say it dumps more fuel.

I would agree with this, what you said.
It's richens the mixture only because it isnt pinging and the ecu is not pulling timing out. It's not really richening things, its more like not leaning it out because of the ping issue. It really depends on the load of your foot & the quality of fuel,LOL

My wifes 04 Sequoia get better mileage using 91, but the book only calls for 89.

Be careful adding a switch to unlock the conveter lock up. Prolonged periods of not being locked will overheat the transmission. There is a clutch ring inside the torque conveter that locks with hydrualic pressure inside the converter, if you electrically shut off the pressure to this clutch, it will be slipping inside the converter and cause the fluid to overheat. I did this to my own vehicle back in 1984 and almost smoked my transission. I do not recommed that mod either, IMO.

[Cobb]

Thanks.

So, let me ask. What performance should my truck give me in regards to 0-60? 6 seconds, 9 seconds, 12 seconds?

I dont mind trying another tank of preminum fuel with a bottle of 104 octane booster. Heck, Ive even considered taking it to a performance shop to have they dyno it and see if its retarding timming, cutting fuel, etc and if they can reprogram it.

Thanks for the advice.

[mustang67408]

I dont know about track tmes, I have a mustang for that stuff.
Octane boost is some of the worst stuff to use. It dosnt work like you think.

Octane boosters decrease in effectiveness as their quantity increases. Just because one ounce gives you 2-1/2 numbers more, ten ounces will not give you 25 numbers. Here's a good scale of just about how decent octane boosters will work:

One ounce/per gallon ¼ 2-1/2 numbers increase

Two ounces/gallon ¼ 4-1/2 numbers increase

Three ounces/gallon ¼ 6 to 6 1/2 numbers increase

Four ounces/gallon ¼ 7 to 7 1/2 numbers increase

A good rule of thumb is that anything over three ounces per gallon is wasted. Some crazies dump in a whole can of booster, thinking they're going to get radical gains. Actually, they'll get a decrease in performance, as excessive ratios can cause the volatiles in the gas to deteriorate and excessive aromatics can make the engine run "heavy," or rich.

WILL OCTANE BOOSTERS ADD HORSEPOWER?

No. This is a misconception. Octane in itself does not add power. However, an engine that's forced to run on fuel with a lower octane than what's needed will run hot, detonate, and eventually lose power. The proper octane level will let the engine run to its full potential, but won't transform it into something special.

When a combustion chamber gets a charge of fuel, the plug sparks, and the fuel is burned. With the right octane level, the burn is clean and even. With too little octane, the burn can be uneven and a hammering can result.

NO PERFORMANCE SHOPS can tune your truck, unless yo have an aftermarket ECU. Like the UNICHIP, then it can be tuned for optimun performance or mileage, but you have to talk to the guy tuning it.

Read this--->Octane

[Arb1977]

TRDOLMAN from TTORA and Customtacos if i remember correctly was able to get 23-24 mpg out of his 305 rwhp Taco.

[mustang67408]

Originally Posted by Arb1977

TRDOLMAN from TTORA and Customtacos if i remember correctly was able to get 23-24 mpg out of his 305 rwhp Taco.

That would be SWEEETTT!