Supercharger mpg?

mr bigolsworth

mr bigolsworth

Well-Known Member
55
13
Pikeville nc
Vehicle Model
Si
Body Style
Coupe
I'm looking at doing force induction on my si. Curious what kind of mpg people are getting on there supercharged si and a description of your set up. Thanks for your time
Merry x-mas,
Chaz
 
Honestly I'd have to calculate it. I don't trust the imid. It's not accurate. But I will say I can sip through a 1/4 tank real fast if I'm driving it hard. It all depends on how you drive. But as soon as you cross into the boost territory. The mpg go way down.
 
:flame:So far I drove about 1000 miles with the kraftwerks kit and I got about 15 mpg but that was due to a lot of testing and tuning. I took a 300 mile trip and got about 24 mpg just average driving with the occasional wot on I-95.
 
ThePainter said:
I took a 300 mile trip and got about 24 mpg just average driving with the occasional wot on I-95.
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That's not bad. Definitely all depends on the driving style.

Gotta pay to play. (IE: gotta pay for that gas if you want to go WOT a lot)
 
bootyluvr said:
That's not bad. Definitely all depends on the driving style.

Gotta pay to play. (IE: gotta pay for that gas if you want to go WOT a lot)
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How do you do on yours? Do you have a build? I've seen pics of it in random threads, but...
 
webby said:
How do you do on yours? Do you have a build? I've seen pics of it in random threads, but...
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I'm not supercharged. I'm turbo'd.

I have a build on my Subaru forum but not here. I guess I could make one here but I am lazy.

As for MPGs.. I do ALOT of city (from site to site since I travel for work using the Subie) so I get low 20's but coming down to the Dragon I was getting high 20's-low 30's but I drive like a grandma (except when I am on the Dragon and 28 lol)
 
bootyluvr said:
I'm not supercharged. I'm turbo'd.

I have a build on my Subaru forum but not here. I guess I could make one here but I am lazy.

As for MPGs.. I do ALOT of city (from site to site since I travel for work using the Subie) so I get low 20's but coming down to the Dragon I was getting high 20's-low 30's but I drive like a grandma (except when I am on the Dragon and 28 lol)
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I know you're turbo...just wondered your Mpgs. Link to your build there?
 
Turbo cars would actually get better mpg than the SC depending on the rpm range where you dwell most. When turbo is not engaged, the mpg should be the same as stock, this is the case most of the time when you are cruising.
 
atom ant said:
Turbo cars would actually get better mpg than the SC depending on the rpm range where you dwell most. When turbo is not engaged, the mpg should be the same as stock, this is the case most of the time when you are cruising.
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Yea. That plus the sc is a constant drag on the motor.
 
Hell Im getting 22mpg mixed highway and city completely stock :(
 
SavageWS6 said:
Hell Im getting 22mpg mixed highway and city completely stock :(
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You are driving it pretty hard then. If I drive like a grandma, I can get a combined 32mpg, and that's with 220ish wheel horse power. Stock I could get 34ish combined.
 
Ya I do at times, I get angry quick in the morning in S.D going to work cause of dumb drivers. Always stuck in traffic too. Stop and go, stop and go. Highway when I was racing from S.D To Irvine I got 27mpg
 
Just for SA...

I've had my own 8th gen (K20Z3) using an Eaton MP62 (with modified RDX injectors [520cc @ ~70psi fuel pressure]) for roughly 60k miles now (car has ~120k total). Always gotten 26-27mpg with mixed driving (roughly 300 miles per tank.) Can touch into the 28-29mpg range during extended highway driving. Lowest I've experienced was ~11-13mpg at the Dragon where, obviously, you're traveling at high rev for extended periods of time (this was over the course of 2.5 days, with many trips up/down the Tail. Total miles per tank for those days was ~175 miles.)
Car is tuned to target a 12.4 A/F ratio, IRCC (don't have my fpcal's with me in Afghanistan to verify.)

OP can view profile for details on current modifications.
 
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Sleepingpanda said:
Yea. That plus the sc is a constant drag on the motor.
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Taken from Eaton's FAQ section: http://www.eaton.in/Eaton/ProductsS...motiveAftermarket/Superchargers/FAQ/index.htm

Q: What is this black plastic object on the side of my supercharger? What is a bypass valve? A: That object is the bypass valve vacuum actuator. This unit has a vacuum port that connects to the supercharger inlet between the rotors and throttle body. This actuator opens and closes a bypass valve for the supercharger. This valve is open when throttle loads are low and closed when throttle loads are high. With the bypass valve open there is no pressure being created across the supercharger. This allows the supercharger to have an almost negligible parasitic loss in this condition. With the bypass valve closed, all airflow is routed through the supercharger and boost is created in the intake manifold. In some newer applications this actuator is also controlled by a solenoid.

Q: …but my turbocharger gives me “free energy” because it uses otherwise wasted exhaust energy! A: This is a common misconception amongst people today. A turbocharger does indeed use the exhaust gas to be powered but this energy comes at a cost. The engine must provide extra pumping work during the exhaust stroke to provide sufficient energy for the turbocharger. This pumping work is not present in normally aspirated or supercharged engines and causes a parasitic loss on the system comparable to that of a belt driven supercharger.

Also, take note of the diagram, suitably labeled, "Power (required to drive supercharger)" here: http://www.capa.com.au/eaton_mp62_4th.htm
This diagram assumes the bypass valve is closed, and the supercharger is creating above-atmospheric pressure ("boost"). According to Eaton's testing reflected in the graph, it takes roughly 35hp to spin an MP62 @ 16000rpm (blower speed) - Note that most users do not exceed 16000rpm on either K20's or K24's, though there are "crazies" among us ;) (For reference, a stock diameter K20Z3 pulley (5.75"), and a 3.15" blower pulley, with a rev limit of 8600, will produce roughly a 15500rpm rotor speed on an MP62 - roughly my configuration, at present) - Speed calculator -> http://www.willbelayforfood.com/rsx/rsxmainsite/BlowerCalcPage/blowerspeed.htm -OR- (crank pulley diameter / blower pulley diameter) x drive ratio (which is 1:1 for the MP62) x engine rpm = blower rpm
 
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SavageWS6 said:
Ya I do at times, I get angry quick in the morning in S.D going to work cause of dumb drivers. Always stuck in traffic too. Stop and go, stop and go. Highway when I was racing from S.D To Irvine I got 27mpg
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God I love San Diego, and hate driving there.

Judging by your screen name, 25mpg is probably spectacular for you haha
 
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