Gas Mileage?
Thread Starter
Joined: Nov 2006
Posts: 8,482
Likes: 31
From: Huntsville AL
Gas Mileage?
Ok, I have a question for you guys. What is your gas mileage and your set up?
Reason being, I know it is normal for people to get 20-24mpg in our gens on the highway. Well, heres the thing. I was out last weekend averaging about 80-85mph on the highway. It was about 90* out, full tank of gas. Actually, let me start over.
Car was above 1/8th tank. Filled it up and it took 10 gallons. Drove on the highway down and back, and it was 279 miles. Parked the car at the house, and now I sit at a quarter tank mark. I am guessing that I used about 8.5 gallons.
That makes my MPG 32.8
Is this possible? Math is right (279 divided by 8.5), but the whole scenario is wrong! Hot outside, 80-85mph, 4k rpm...
12A
Holly 600
Stock ports
RB header
2.5" straight through exhaust
2GDFIS
Reason being, I know it is normal for people to get 20-24mpg in our gens on the highway. Well, heres the thing. I was out last weekend averaging about 80-85mph on the highway. It was about 90* out, full tank of gas. Actually, let me start over.
Car was above 1/8th tank. Filled it up and it took 10 gallons. Drove on the highway down and back, and it was 279 miles. Parked the car at the house, and now I sit at a quarter tank mark. I am guessing that I used about 8.5 gallons.
That makes my MPG 32.8
Is this possible? Math is right (279 divided by 8.5), but the whole scenario is wrong! Hot outside, 80-85mph, 4k rpm...
12A
Holly 600
Stock ports
RB header
2.5" straight through exhaust
2GDFIS
Thread Starter
Joined: Nov 2006
Posts: 8,482
Likes: 31
From: Huntsville AL
Here is a picture during the drive. Odometer was reset when I got gas. I know I am not doing 80 in this picture, I was slowing down when I took it.
Thread Starter
Joined: Nov 2006
Posts: 8,482
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From: Huntsville AL
Full Member
Joined: Oct 2005
Posts: 58
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From: Pittsburgh
Try fill the tank till it clicks off then one more time. Travel then refill preferably at same station, till second shutoff and do the math. the best way though is to do it over time. My grandfather kept a little book... yeah like I have the time to do that. He was able to do it because you sat your butt in the car waiting for the kid to fill it up. Oh and It was 39.9.
Thread Starter
Joined: Nov 2006
Posts: 8,482
Likes: 31
From: Huntsville AL
Back. It shut off at 8.8, but I kept it going until it hit 9 gallons.
Think I was joking when I said 9 gallons
Tank is full, 283 miles. 9 gallons.
31.44444444444444444444444 mpg
Think I was joking when I said 9 gallons
Tank is full, 283 miles. 9 gallons.
31.44444444444444444444444 mpg
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Thread Starter
Joined: Nov 2006
Posts: 8,482
Likes: 31
From: Huntsville AL
Yeah. Honestly I drive hard in the city. I see no more than MAYBE 16mpg city (if I am easy) but this highway cruise has me mystified. I never floored it, just brought it up to speed on primaries only.
Its funny, because everyone laughs at the 600 being too much for a stock port, yet I get this mileage.
Its funny, because everyone laughs at the 600 being too much for a stock port, yet I get this mileage.
Thread Starter
Joined: Nov 2006
Posts: 8,482
Likes: 31
From: Huntsville AL
I am thinking... the piston engine is efficient at XXXX RPM. When the ratio's for the speed make more than the RPMs Gas mileage.
Like, if at 3000 RPMS you are doing 60 at 30mpg, but at 4000rpms you are doing 80 at 20mpg, then 3000 rpms would net you more distance per gallon than higher speeds. Would the rotary (or combination I have) net me more MPG at 4000rpms than 3000rpms? I would be going faster, yet be using a little more gas.
Hard to explain, had a few beers tonight.
Like, if at 3000 RPMS you are doing 60 at 30mpg, but at 4000rpms you are doing 80 at 20mpg, then 3000 rpms would net you more distance per gallon than higher speeds. Would the rotary (or combination I have) net me more MPG at 4000rpms than 3000rpms? I would be going faster, yet be using a little more gas.
Hard to explain, had a few beers tonight.
I need a new user title
Joined: Oct 2005
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From: Yaizu, Japan
Part throttle with a 600 is no problem. It's full throttle where you're losing efficiency. But that's a debate for a different thread.
Actually, the larger bore of the primaries might be helping you here. If you have enough power to do 80-85 on primaries alone with this setup, but would have to dip into the secondaries with a smaller carb, it might be more efficient that way. That's just a guess, though.
Actually, the larger bore of the primaries might be helping you here. If you have enough power to do 80-85 on primaries alone with this setup, but would have to dip into the secondaries with a smaller carb, it might be more efficient that way. That's just a guess, though.
Last edited by PercentSevenC; Jun 17, 2008 at 01:12 AM.
Thread Starter
Joined: Nov 2006
Posts: 8,482
Likes: 31
From: Huntsville AL
Part throttle with a 600 is no problem. It's full throttle where you're losing efficiency. But that's a debate for a different thread.
Actually, the larger bore of the primaries might be helping you here. If you have enough power to do 80-85 on primaries alone with this setup, but would have to dip into the secondaries with a smaller carb, it might be more efficient that way. That's just a guess, though.
Actually, the larger bore of the primaries might be helping you here. If you have enough power to do 80-85 on primaries alone with this setup, but would have to dip into the secondaries with a smaller carb, it might be more efficient that way. That's just a guess, though.
)But since then, there was a nut/bolt added to where it is a mechanical secondary after about 2/3rds the way down the pedal, hence removing the 5000 "dead zone" of primaries only.
I never really got on the gas enough to build the vacuum enough to get the secondaries opened (well, if I did it was very very little, I can feel it), so I believe with the primaries opened only (since the prim's are bigger than the prim's on the nikki/sterling) I can get more "oomph" with it.
Rotary Enthusiast
Joined: Dec 2007
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From: Texas
Yea that's one thing I love about them takes me about 2 gallons to drive to Schlitterbahn and back (62 miles round). Oddly enough my LT1 vette get's about the same hwy mpg as my 12a. The drag co e is exactly the same with a C4 body as a FB body. So good engine with a good aerodynamic body is energy effecient.
Rotary Enthusiast
Joined: Dec 2007
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From: Texas
Just was something I have been thinking about in terms of high performance vehicles. The C4 I don't think it's much heavier it's just a motor with a boat body.
I was thinking it's more due to the body. At least the highway mileage.
I was thinking it's more due to the body. At least the highway mileage.
After a close study of your pic from driving, im surmising that since your oil has no pressure, that is going to save you gas :P
I agree with the rotaries efficiency at mid rpm, inertia, lack of resistance (aeros bearings tires etc), clean oil, and a good slippery premix. Maybe a lil more than atmospheric pressure under the hood allowing a slight charge? Definatly running on 2barrels at 80mphs with a light foot and some drafting. Can draft about anything with 4 wheels...
I agree with the rotaries efficiency at mid rpm, inertia, lack of resistance (aeros bearings tires etc), clean oil, and a good slippery premix. Maybe a lil more than atmospheric pressure under the hood allowing a slight charge? Definatly running on 2barrels at 80mphs with a light foot and some drafting. Can draft about anything with 4 wheels...
Thread Starter
Joined: Nov 2006
Posts: 8,482
Likes: 31
From: Huntsville AL
im getting close to 28mpg on freeway and averaging 25mpg with mixed.
The setup is...
12A (178,000 miles without rebuild)
rebuilt carb with mechanical secondaries
K&N airfilter with RB Intake
NGK plugs and wires
RB headers, No cats, Magnaflow muffler
I think the biggest thing is keeping it under 2k and not having a heavy foot. And keeping the carb tuned and fluids checked.
The setup is...
12A (178,000 miles without rebuild)
rebuilt carb with mechanical secondaries
K&N airfilter with RB Intake
NGK plugs and wires
RB headers, No cats, Magnaflow muffler
I think the biggest thing is keeping it under 2k and not having a heavy foot. And keeping the carb tuned and fluids checked.
Joined: Mar 2001
Posts: 31,835
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From: https://www2.mazda.com/en/100th/
the difference is, it takes MORE power to accelerate the pos upside down boat, cause its really heavy.
Thread Starter
Joined: Nov 2006
Posts: 8,482
Likes: 31
From: Huntsville AL
Part throttle with a 600 is no problem. It's full throttle where you're losing efficiency. But that's a debate for a different thread.
Actually, the larger bore of the primaries might be helping you here. If you have enough power to do 80-85 on primaries alone with this setup, but would have to dip into the secondaries with a smaller carb, it might be more efficient that way. That's just a guess, though.
Actually, the larger bore of the primaries might be helping you here. If you have enough power to do 80-85 on primaries alone with this setup, but would have to dip into the secondaries with a smaller carb, it might be more efficient that way. That's just a guess, though.
