hey everyone i got an 83 gls w/ sterling nikki, and no emissions. now i figured that my gas mileage wouldn't be as good as stock but 12 miles to the gallon is rediculouse!

I have a bunch of exaust leaks and a vacuume leak somewhere, but I don't think that would cause me to get that bad of gas mileage....would it?

 

Those problems could cause it to be that bad. I'm getting about 17mpg with my setup.

 

Vacuum leaks can; they're messing up your fuel mixture, and proper mixture is essential to anything regarding efficiency.

Keep in mind that the stock EPA ratings for these cars when brand new and in perfect tune was only around 21city/30highway for the 83... and in the early 80's EPA numbers were notorious for having little to no relation to actual mileage.

Variance of 50% or more was typical.

(for the 1980 pre-cat build, it was 17/26)

 

Thats pretty bad, but having leaks doesn't help. Also, I believe that the Sterling doesn't come jetted for economy. Besides that, if your driving in the four barrels all the time gas mileage will be quite bad. When I first got my car I was driving it back and forth to work, which is about 3 miles away. I probably redlined the car a dozen times in those 3 miles and I was getting about 13-15mpg. When I drive my car to school (about 30 miles) and drive a bit more conservatively I get about 17-19.

 

I am getting only 220 miles per tank. Its really rediculous

 

welcome to the 12mpg club.

 

I'm getting around 11-15. With my setup. Woo city driving. I think the worst I got in the city was 10mpg.

 

Here's a mileage chart gathered over several hundred datapoints showing the most recent data. This is the 84SE described in my signature line, and 204k mi on the original engine - NO REBUILD.

Shows Highway Miles to the left, City Miles in the middle, and Mixed Driving on the right. You can see that average driving yields about 19.3 MPG, and that's in an SE that I don't baby.



The mechanical makeup of your car has an impact on your MPG performance, but the single biggest factor is your right foot.

 

My average is 10-11 in the city.

 

I got 7miles/gal on my rotary 12a starlet lol she runs perfect but it might be running too rich???

I know I have some leaks on the exhaust but man 7miles/gal is ridiculous.....

 

On my last big trip I figured out that I get 9.0km/L Highway

Which Google tells me is "21mpg" in your strange notation...

I've got a Sterling, Ported Manifold, Racing Beat Street Port exhaust system and an original 12a with over 200,000km on it that blows borderline-rebuild compression (7.1kg/cm2 at 300rpm).

Stock ignition and ignition timing, ISCRacing Airbox (it's kind-of like the RB one), and not much else that would affect gas mileage (e-fan?)

In the city I get substantially less, especially if I'm in the secondaries all the time.

Vac leaks and a lack of tuning could definitely affect your gas mileage. I tuned my Sterling on a dyno, then backed the primaries off a notch because I was running too rich under many circumstances. Make sure your vac advance is working and that you eliminate all vac leaks.

Jon

 

I rebuilt my carburator. My mother lives about 55 miles away from me. I spend less then a quarter of a tank when I visit. The carb isn't running rich or lean either. I got a mechanical secondary.

 

Ya, I average around 200 a tank with my 83 gsl. I think I could get a lot better, but i have a sidedraft 44 mikuni, exhaust, and 13b from a gsl-se.

 

When I'm on the highway I get 23-25, city about 15-17 and combined 18-20.

 

You have many leaks?...Better fix it...

 

Well when I first got my Sterling it was jetted in the middle of fuel economy and street performance. Even with my carb tuned really rich on the primaries I can still get about 500KM/tank or a little more than 300miles/tank. The way it was sent to me I could get over 700KM/tank or 400miles/tank on the highway cruising steadily at about 80mph. First step is to fix the problems you already have. After that set your timing and do a full tune-up if you haven't done one recently and try again. Calculate your mileage over 2 or 3 fills. Do your best to drive conservatively. If it's still giving you shitty mileage pull the jets and see what it has in it. Mine was sent with .048's in the primary fuel, .027 in the primary air, .063's in the secondary fuel, and either .052's or .055's in the secondary air. I can't remember off the top of my head. After this, the only logical explanation is your right foot is too damn heavy and you need to teach yourself how to be gentle with the pedal. If you are driving carefully and your primary fuel jets are higher than a 55, your going to get very bad mileage, unless your airbleeds are really high too. Did you buy the carb straight from Sterling or did it come on the car?

 

For clarity, it's not a Sterling Nikki, it's a Bare Nikki. Big difference. I don't even think it has mechanical secondaries. (Can't remember.)
Jetting is stock.

My guess is that the fuel pressure is too high and/or the return line is compromised, and the carb's emulsion system is siphoning in fuel after a certain RPM. In any case it is running extremely (crazy) rich, and consequently is way down on power.

 

I have a Dellorto DHLA 48 and I get around 18 mpg in the city and 25 mpg
cruising on the highway @80 mph.

I can get even better if I cruise at 60 mph but thats no fun.

 

i can average 15-16 on a holley 600 with sp. just gotta keep it on the primaries.

 

well I don't drive it like an old lady but I don't stomp on it everywhere I go either. I do need to figure out where that vacuume leak is and then tune my carb after its fixed. The exaust leaks are probably a big part of it cause their bad theirs a hole the size of my fist in the back of my muffler. The guy i got it from said it backfired and put a big hole in it.

 

I have a "home-made Sterling" type Nikki that I recently rebuilt after 15 years since my last rebuild. I am the original owner of an '81GS (bought new in Mar 81) and over the years I've had between 26mpg highway (back in the early 80s, cruised about 60-65mph) and 18 city to 15 city and 20mpg highway before the rebuild (70mph cruise with a/c in Phoenix). After the rebuild and carb mods, I am getting about 24mpg at 70mph and 20mpg city (conservatively driven).

I used the MazdaTrix rebuild kit, added a custom accelerator pump linkage and more accel pump volume, left the vacuum secondaries, kept the choke (removed all but the butterfly, however) and opened up the carb to breathe better. I ground off the alignment tabs on the boosters (pri and sec), polished the venturies and cleaned or replaced everything. Hence, used some of Sterling's magic, but it's mostly a stock Nikki. I also modified my intake manifold to look like a '79, without the anti-afterburn valve and ground off the ridge between the aft rotor runners. This, combined with my Racing Beat exhaust give me a good, streetable 12a. It's got 160,000 original miles on a non-rebuilt engine that still gives 90psi compression and no leaks. Nothing wild, but much better than the original engine in performance at mileage that you can live with. I do average about 15mpg all around if driven hard.

Hope this "history" helps.

Mike

 

On my drive from Ann Arbor, MI to Houghton, MI last July (550 miles), I got 28mpg on the freeway @ 78mph. Driving around the Keewenaw, I got ~10mpg because I was driving hard down backroads. Driving back downstate at the start of May after 6 months in storage, I got 23mpg average. My last two tanks were 220 miles and 195 miles on ~14 gallons. I have a heavy foot tho...