I finely calculated the fuel usage on my car last weekend. We were doing a tour with the local PCA group that was mostly twisty corners and short straights. Lots of time accerating thru the gears, so I expected the mileage to be poor.

For those of you who don't remember my car, I'm driving a 3.0 with PMOs. Few months ago I had the carbs tuned by a local guy who was recommended by several PCA members with similar engines.

Just wondering what the rest of you out there have similar mileage

I get 11mpg with my 2007 Suburban 2500 converted to 6.6L Duramax diesel while pulling my 11,000 lb. camper.

On the track, 8mpg...2.7l....2000 pounds. Works out to about $1 per minute, $2 if I buy race fuel at the track...

My 4 dr Dodge Cummins just got 21.5mpg on a 2000 mile trip. It's making about 370HP and about 700ft/lbs. I used it the other day to pull some big trees out of the way that fell across a hunting trail....you're probably faster than me in the twisties tho....

The '67-S got 14-18 in testing and that was a 2 liter engine. MFI was marginally better but if flogged those cars were 13-ish on the bottom end of the scale.
Mileage (mpg) is the biggest complaint of anyone who converts a CIS car to carbs. I've got PMO's on my 2.7 "built" engine and they are thirsty.

Free advice?

Soft pedal that right pedal.

My Syncro Westy with an EG33 Subie -6 gets about 15mpg @ 70mph highwa speeds. Not much difference in the twisties.

10 mpg is what Elvira got on the recent PCA tour to the mountains.

The Cayman however delivers 23 as my city/highway daily driver, 28 legal Interstate, . . . . and 9 on the track.

Last time I filled up my 914-3.2L w/Motronic I got just under 10 MPG but it's known to be running quite rich. On the other hand, my '09 Cayenne Turbo S got a record 18.4 yesterday on a mostly Interstate trip. Go figure!

My old suby NA2.5 I got a low of 17mpg when I was flogging it at the track. 30 on straight hwy. I think I averaged around 24 typical mixed. I'll be curious to see what I'll get with my new WRX turbo motor

How big are your PMO's

Bob B

Mine are 40's.

I think that we sacrifice MPGs for SPG.

Smiles per gallon.

With my '86 930 with 3.3L turbo, I get between 12MPG around town to about 18MPG on the highway. Not real efficient but boat loads of fun.

Your 10MPG probably isn't far from mine when considering you were doing hills and lots of turns, braking, and acceleration.

So, what kind of mileage are you getting?

Sorry, I didn't see the title of your post!

10 MPG is about right when you got your foot into it. I have a 3.0 with Webber 40 IDAs and when I lay into her 10 is about right.

As a good friend always says, all carbs are, are a controlled fuel leak.

My 3.0FI averages 24 city and 29 highway @ 90

My 3.2 with Motronic got 26mpg with the roof on and windows rolled up and 23mpg with the roof off and windows down.

I'm in the teens with my foot in my 3.2. But who cares?

A few things to think of.

If your fuel tank does not have a pressure / vacuum cap + carbon canister, you will be losing fuel to evaporation. You might even be losing liquid fuel due to slosh.

Many aftermarket carbs don't have a sealed bowl plumbed to the carbon canister, every time the engine is shut off, some fuel is lost to evaporation.

A vacuum advance does wonders for part throttle fuel economy. If this is missing you are losing MPG.

If the power valve , power jet , main jet setup is too rich, you will be losing MPG at lighter loads. ( RE, if main jets are rich and power valve jets lean, you are running rich at light loads. )

My 3.0 with Weber 46 carbs averages 8 mpg on the track.

My 3.0 Suby six averages 25mpg.

My little 2.2T drinks like a fish,I haven't measured consumption ,think I would be lucky to get 15mpg,was a lot worse until I put smaller main jets in.

I think you might have a teenager siphoning gas from your car while you are at work...

Carburated SBC, just did Reno and back from L.A. and averaged 16 mpg. Much better then expected. Pic at Mono Lake.

Imagine what a modern FI LS would do and with more HP. Hmm.

Hah kicked them out of the house years jeez the last one was hard to move,22yrs old and finally gone.
Funny miss them now but still feed them $$$ , mind you I live in the country near a small town that has one of the highest grime rates in my country.
Generally home most days as I'am retired,better get the gun out .

Have been monitoring mine since I just got it together. 20.5 mpg on the first two full ups. I've been going easy getting used to the car. Some lightly spirited driving on secondary roads. It has 3.2 motronic with a Steve Wong chip, 915 and 225/50/15 rear tires. So it turns slightly higher rpms with the smaller diameter tires. I was pretty happy with that, not that I would matter if it was worse.

Driven at legal speeds I can get 27mpg. This is about the same as what people get with a six speed chevy. Even with a Boxster transaxle I'm still geared Low.

If I ride my bike hard enough it will drop to about 12 mpg..
Just saying....

OT a little, Who is the carb guy that was recommended to you? I live in Olympia area and need such a person.Thanks

"All things in moderation"

24 mpg with my 3.6L, goes down to ~20 with spirited driving, goes down to about ~10 on the track ...

Aviation engines that are air cooled run rich to help keep them cool. Is that something they do with air cooled Porsche engines?

I get 27 miles per gallon with my motor, Billy. You can afford the petrol...

Tony

I'm not complaining, just wondering if its normal. I just need to plan more stops to refill the tank.

I've got it...install a 4-cylinder!

I get about 13 with my 350 SBC. Having the engine tuned now and will give an update when I've had a chance to recheck.

I don't think I can handle the power/weight if I did. Need the weight on the /6 to slow down the car

So I was going through and sorting out pictures over the weekend. This was in the group of photos at my son took at West Coast rally this year. obviously not happy that he was driving my truck that fast but even more unhappy that he decided it'd be a good idea, at that speed, to get his phone out and take a picture of it

12.5 mpg average Towing an enclosed trailer ( not at the time this photo was taken)

Rule #1 of doing stupid stuff: "Don't take pictures of yourself doing stupid stuff!"

Umm. I was there. I was in front of him in my truck. Lastly, I was apparently a bad influence! Sorry.

PS: This was our "stupid" moment...at the same moment.

Tony




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What am I missing how are both trucks running below 2500 rpm at 100+ 6th gear in my Holden/Pontiac GTO was more than that.

I could do 85 at 2200rpm in my 2004 Durango so I’m not surprised on a newer truck.

Didn't known you owned a monaro mike.

Jeff Hines' 'red beast' drank fuel like I couldn't believe when I drove it at RRC.

I will own another, but 4 door this time, G8 or a newer SS. Kids not getting any shorter.

No fuel cut on over run. No sealed system. Spirited driving. Biggish engine, probably tuned to the rich side of things. I'm not at all surprised by your numbers.

Are your tires stock sized? If they aren't, and your Odo has not been re-geared for the new tire size, your calculation is wrong anyway.
Zach

I'm sure my car will get crap mpg when it's all put together. If I could have afforded the $5k or so for EFI I would have done it....but I'm already spending too much on the 2.7RS+ engine rebuild.

I got crap mpg on my carb'd worked over 2.0 in the city, but it made 30mpg or so on the highway...since it was right between the idle and main jets at 65mph. Keeping it at 60-ish it would get great mpg.

My 3.0 with 40's gets 14.9 with my foot in it at every chance. Idle jets (60) made a big diff as well as timing advance.

This is calculated from a recent full rebuild and a 1000 mile rev limit breakin period at 5,500 rams. Now 7k.

Also to check fuel to air ratio I remove each plug and examine for rich or lean conditions and adjust each throat to nice toasty brown no soot conditions.

Only 3.5k miles just yet. Logged on gas tracker Fuelly. Free AP with multiple vehicles.

Great point forrestkhaag: setting up the cars correctly is a must. Getting a clip-on O2 sensor or putting one in all the time and tracking it can make everything happy and get probably 75% close to an FI car. Takes some skill/knowledge etc.
I'm sure I'll have my engine friend road tune mine once it's all together. He's used to dialing in MFI cars, so carbs should be simple....or maybe I should 'waste' money and used the 2.8 MFI he took of a client's car for high butterfly upgrade, HAHA. If only I had a money tree...