Supercharged gas milage

[tbm34]

This little contraption just keeps getting better and better. I’ve been keeping track of my gas mileage for a while now, but wanted to wait until I ran 5 tanks of gas through on the Supercharged Vibe before posting . The mileage on my Vibe is mostly commuting about 75 miles a day 3-4 days a week. It is pretty evenly split between highway and then working my way up through the city. Stock 5-spd with alloy rims; average 31.56 mpg, n=15 Stock 5-spd with OEM steel rims and snowtires; Average 29.28 mpg, n=13Supercharged w/Unichip & alloy rims; Average 29.04 mpg, n=5.So basically I lost about 2.5 mpg with the supercharger with lots of heavy dosing of the new toy. Not much different than when I threw the OEM steel wheels and snow tires on for winter. I also just installed and mounted a boost gauge on the dash. It is a blast watching the needle jump from a vacuum of 20 in mg to 8 PSI under full boost almost instantaneously. When not punching the gas, the supercharger spins under a vacuum requiring less than 13 of a hp to maintain with the actuator/ by-pass valve. This is why the superchargers are so efficient.

[goodvibe]

I think the unichip is helping your mileage a lot. Stock, the SC runs very rich in boost.

[tbm34]

Quote, originally posted by goodvibe »I think the unichip is helping your mileage a lot. Stock, the SC runs very rich in boost.I'm Thinking the same. I think it also must be helping out the boost, as I've been reading over 8 PSI on cool mornings. The tuner also measured higher than the 7.5 psi advertised boost of the supercharger. What actually determines the amount of boost of this particular supercharger? If GM/TRD tuned down the A/F ratio, maybe they are also limiting boost through the piggy-back ECU. Another advantage of the Unichip. My dyno's seem to reflect this as I'm over 160 torque and HP at the wheel.

[Faultline]

Very impressive #'s...my turbo's fuel kit runs rich while under boost. If I want to get identical mileage to stock, I need to keep the rpms below 3k. ON long trips this is doable and probable. Around town it is doable , yet improbable.....I cant resist boost!!!!!!

[bellwilliam]

I am not so lucky on mine .I have S/C and A/F controller.before s/c - 23-27mpgafter s/c - 16-24mpgone time I actually got 13mpg, but that was during dyno and many 1/4 mile run

[noginsk]

Quote, originally posted by bellwilliam »I am not so lucky on mine .I have S/C and A/F controller.before s/c - 23-27mpgafter s/c - 16-24mpgone time I actually got 13mpg, but that was during dyno and many 1/4 mile run Looks like you are also running an auto, that would eat a few miles too.__well, looks like you guys convinced me I need a supercharger, just a matter of finding the cash. Still might be awhile. I wonder if I can get it in there without the wife finding out?

[teammonkeys]

I'm getting on average about 22-25 mpg over 5000 miles. This includes both highway and city driving, AC maybe on or off. But then again, my vibe is AWD.

[MadBill]

Quote, originally posted by tbm34 »I'm Thinking the same. I think it also must be helping out the boost, as I've been reading over 8 PSI on cool mornings. The tuner also measured higher than the 7.5 psi advertised boost of the supercharger. What actually determines the amount of boost of this particular supercharger? If GM/TRD tuned down the A/F ratio, maybe they are also limiting boost through the piggy-back ECU. Another advantage of the Unichip. My dyno's seem to reflect this as I'm over 160 torque and HP at the wheel.The only way they could limit the boost is by having some kind of ECU-controlled solenoid in the bypass circuit (Buick does this on the S/C 3800, but it only triggers under certain conditions, e.g. reverse gear) One could always find out by temporarily disabling the bypass to see if the boost goes any higher.Another factor re boost is how free breathing the engine is. A better air cleaner/CAI would increase the boost by reducing the negative pressure at the throttle inlet, whereas a freer breathing engine, e.g. ported head, free flow exhaust, etc. will actually reduce the boost under given conditions, because it presents less restriction to the airflow. [Pulleys down to 2.7" are offered for the Buick 3800 (std. is 3.75") but going smaller than 3.4" adds boost but doesn't help power unless it has headers, a bigger cam and/or ported heads.]

[futseal04]

Computers on forced induction cars are tuned to be rich on boost to keep combustion temps down....this is a good thing if longevity is a concern. Does anyone know of an intercooler package available for the GM supercharger?

[Faultline]

Quote, originally posted by futseal04 »Computers on forced induction cars are tuned to be rich on boost to keep combustion temps down....this is a good thing if longevity is a concern. Does anyone know of an intercooler package available for the GM supercharger?nope! the way the kit is designed, it sits right down on the head. I think that just 2" up , then there would be hood clearance issues....some guys are doing water injection to cool intake temps.