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Discussion Starter #1
I Have A 1988.5 Samurai Not Lifted With 215/75 Tires And A Weber Carb.all I Can Get Out Of It Is 18mpg Is This All It Should Do? If Not Give Me Some Ideas
 

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With larger than stock tires and a weber you are almost in the right ballpark. You should be at around 22mpg. Also depends on your driving style.
So the people claiming the weber carb improves performance AND mpg are wrong?

Also when one increases the diameter of the tires would that not drop the rpm's a bit and increase the mpg's?
 

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MPG for the weber is only slightly higher than the stock setup, but when you go to larger tires you decrease that number dramatically. Stock everything - and in perfect condition - you should be getting 28-29mpg. When I went to 31" tires and stock everything else - it went down to about 17-18mpg. Larger, heavier tires will do that. A weber will bring that back up, but not all the way. It will also increase the feel you get when you step on the skinny pedal. Although it doesn't match Suzuki's original efficiency, folks use it as a cheap way to regain some lost mpg and power.

The only carb setup that I have seen to come close to stock mpg while using aftermarket gears and bigger tires has been the Harley carb conversion.
 

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Discussion Starter #5
I Am Getting Around 20-21 Mpg Now.the Person I Bought It From Did A Bad Job Installing Th Weber.it Was Leaking Air Everywhere.took It Off And Put It Back Like It Should Be.fixing To Put A Header With 2" Exhaust I Think This Will Help.it Is A Money Pit But I Love It.
 

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its a money pit, but when you look at the cost of a newer vehicle and the repairs and maintenance on it, you're ahead with a samurai. It's the most cost effective vehicle I have owned, and I've owned a lot of different cars and trucks.

Vacuum leaks are really comon on them. The adapter plate screws like to back out, and the only way to get at them is to remove the carb. When you install one or work on one, its a good idea to use a little RTV on the threads to keep them from backing out on you down the road.

The stock carb is limited on it's response and low end because of the emissions requirements and fuel efficiency requirements. The Weber cuts all of that out and gives you a little more power and faster throttle response. The weber however, doesn't adjust it's fuel according to the driving conditions, air temperature and pressure. If you change climates and altitude, you need to manually adjust your weber for that. A properly adjusted weber will get pretty good MPG but if it's not adjusted correctly it will suck gas like crazy. You'll still get great power out of it, but at the expense of fuel consumption. If you take advantage of the lower end power and the faster throttle, you will negate any saving in fuel efficiency.

I just drove mine with the jets it came with and it worked out great. I only got about 18-20mpg with my 32s but that was because I liked to feel the extra kick off the line. I got even less fuel efficency with my mikuni dual side drafts, but that was mostly because I couldn't keep myself from sticking my foot through the floor and getting pushed back into my seat. I'm back to my stock carb now and I'm making about 20mpg on 32's but much less kick off the line than I had with the weber or the mikunis. I figure if I can't control myself, I better restrict myself.
 

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Discussion Starter #7
i love the thing it will run 65mph on the highway. I dont do it very often dont want to tear up anything.will the header help? I heard it would help the hp just not sure how much. i just painted it real tree camo with a stencil kit and it turned out awsome.Now all my buddies want me to do theirs but it is alot of work.
 

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wow, i run about 20mpg with stock engine & carb, stock exhaust (only for 2 more weeks :D) 215/75 tyres and a 2" lift... and it actually doesnt make a difference whether i drive like a granny or a leadfoot, theres barely any difference... maybe its time for me to look into a rebuild... or a 1.6, either way
 

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SammiMPG

I have an '86 tintop with a Weber, performance cam, GM alternator, stock tire size, and headers - gets 28 now that the weather is warmer up here (N. Idaho). Vastly improved performance over stock (managed 85mph on a windless level stretch). I use a Holley fuel pressure regulator to get 3.5 psi at the carb.
 

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I'm glad this subject came up because I, too, have what I thought was lower MPG than I expected to get. This is a stock 94 with the exception of 235 tires. I haven't had it over 55 for more than a split second because it starts shaking so much, but most of the time driving it is split between going 50-52 down the road 10 miles, or going 35 MPH 2 miles down the road to the river, so I haven't had the chance to empty a tank on a nice, long drive at highway speeds. It is at the shop today getting the tires balanced to help with the scary shaking, but I didn't think the 235s would cause me to get 19MPG, or am I wrong? It's also getting the ignition timing set since putting on a new timing belt and everything around that area--water pump, etc. It does have 3 cracks in the exhaust manifold, for which I am still waiting on the arrival of my header and then I'll put on an entirely new exhaust. I don't know what else could cause this, or is it really just the larger tires? BTW, I don't dog this truck either. I'm nice to the gas pedal.
 

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Perhaps I am wrong, but I find it hard to believe that tires would make such a major difference when they are still in the same ballpark. Larger tires with larger diameters also introduce speedometer/odometer error. When your odometer shows 19 miles traveled, you will have actually moved about 20.
I have been working on my '86 tintop to see how much performance I can get with good mpg at the same time. It is now shod with 205/70R15 street tires. I think I can do a swap with another vehicle and get some larger tires on it to see what difference it makes.
 

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I thought i'd get better mileage than I do too - I put it down to the fact my engine isn't fresh anymore (~150K miles). Does anyone know how much high mileage will affect MPG?
 

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as was mentioned, with larger tires and wheels than stock, not only do you have to overcome that larger diameter tire and wider contact patch with an already marginally powered engine, but your odometer will be telling you less miles have been traveled than actually have. Any gearing changes that have been done will also affect your odometer reading.

If your tire size has changed your speed and distance by 10 percent, then you need to add that to your calculations. 140 miles on 7 gallons of gas is 20mpg. Adjust for 10 percent change in distance and 154 miles on 7 gallons of gas is 22mpg.

Here's a gear ratio calculator that will allow you to figure out what your total drive train difference will be with various gear changes and tire sizes.
Suzuki Samurai Gear Calculator

Other things that will affect fuel efficiency are poorly ballanced tires, worn steering or suspension component, misaligned tires, damaged u-joints, out of ballance drive shaft, bad plugs/wires/cap/rotor, weak coil.
 

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It never occurred to me till I read this the other day when someone else also mentioned that the odometer would also be wrong, not just the speedo. So my mileage isn't as bad as I thought after all. I'm getting it out of the shop today so hopefully it'll do even better after having had the idle adjusted and the ignition timing done.
Thanks for clueing me in guys!
 

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Here is a tidbit that you can use to understand tires... say a 225/70R15. The first number, 225 indicates tread width in millimeters. The second number - 70 - is the ratio of tread width to height measured from the rim outwards. The R indicates a radial tire and the 15 indicates that it fits on a 15" rim. To calculate the diameter

Tire Dia = (tread width / 25.4) x 2 x (aspect ratio)/100 + (wheel diameter)

for the example it is Dia = (225 /25.4)x2x(70/100)+15 = 27.4 inches

You will need that to use the gear ratio calculator.
 

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I'm currently running a new stock carb on a fresh rebuilt 1.3 with a Thorley header, 2" exhaust and 215/75-15s.

My fuel economy(compensated for true miles traveled) on my trip from Baker CA to Fairfield, via Sequoia national forest and Lodi, ranged from 22 mpg, running the A/C and cruising at 65 near sea level to 27 mpg, cruising 35-45 through Sequoia which is at high elevation with the A/C off. A/C off at 65 gave me 25 mpg. If I had not compensated for the odometer error, those figures would have been lower by almost 2 mpg.

EPA rating was 24-26 mpg for the Samurai, so anything in that ballpark is doing pretty good. Of course, the closer to top speed(and full power) you get, the more it is going to suck the gas...

Car and Driver did coast-down measurements on a Samurai and found that it took 6 hp to do 30 mph, 17 hp to do 50, and 44 hp to do 70. They also found it to have a top speed of 77 mph, which based on the previous readings, I estimate to be about 57 HP.

Extrapolating, I figure that, for a stock Samurai with stock size tires, it would take, roughly, the following power to pull a given speed;
MPH = HP
30 = 6
35 = 8
40 = 10
45 = 13
50 = 17
55 = 23
60 = 29
65 = 36
70 = 44
75 = 54
80 = 65
85 = 77
90 = 90
95 = 106
100 = 123
 

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fuel consumption

Hello Suzuki lovers.
There are other draws on fuel used to move.
Consider what will happen if the brakes are dragging instead of gliding.
It will take much more fuel used to travel faster, even more fuel if the brake pads/linings swell because of the heat generated. Sometimes caused by caliper seizures.
Alignment can cost fuel too, since the tires will be dragging more than needed to maintain proper handing and steering.
The 4x4 will also dart back and forth in the lane causing unstable travel.
Another fuel waster is the 'idle to warm' habit.
Greasy side down !
arlo
 
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