IM6 GAS MILEAGE STINKS

IF you are only getting 10.5 mpg, you need to lean it up, man. That's awful.

It's just the excitement of the new toy. I bet you're stomping on it every chance you get...I would. F mpg's!

crhemi (Bill) poboiinhawaii posted:

It's just the excitement of the new toy. I bet you're stomping on it every chance you get...I would. F mpg's!

You are exactly right....I've been getting on it and passing cars left and right..... getting close to 12 MPG and my MECHANIC is a MASTER...motor PURRS smoothly and power. He drives a 3.8 flat six with TWIN PLUGS, 12 coils, TWIN 46 3 barrel WEBERS and and can tune any Porsche stoned on a 12 pack or fifth of Tequila.

I do drive it hard and  twin 3 barrels on a 220 HP flay six will eat gas...the MIXTURE is perfect.....

SUPERTEC PERFORMANCE(CA.), builder of motor told me to drive it hard...it will NOT be happy unless I'm cranking between 2500 and 6000 on a regular basis and the only way to keep it young is to RIDE it like a BUFFALO in HEAT! He builds the hottest flat sixes in California and I will take his word!

It is TIGHT and I have yet to shake it off of the pavement at all...I cannot get past how it handles along with its thirsty disposition!.

I'm happy as a pig in sh*t!

Banzai Pipeline posted:

SUPERTEC PERFORMANCE(CA.), builder of motor told me to drive it hard...it will NOT be happy unless I'm cranking between 2500 and 6000 on a regular basis and the only way to keep it young is to RIDE it like a BUFFALO in HEAT! He builds the hottest flat sixes in California and I will take his word!

It is TIGHT and I have yet to shake it off of the pavement at all...I cannot get past how it handles along with its thirsty disposition!.

I'm happy as a pig in sh*t!

Then 10-12 mpg it it, sir....or dude!! Drive on!!

There are some good air cooled mechanics on Oahu.  Get it tuned and you'll really be impressed with performance, plus get much better mileage.

Jim Kelly posted:

There are some good air cooled mechanics on Oahu.  Get it tuned and you'll really be impressed with performance, plus get much better mileage.

Already TUNED by the BEST.......the build profile and my driving dictates mileage. A STOCK FACTORY 2.4 gets 15 MPG with fuel injection. A 2.7RS, which is bigger and TWIN 3 Barrel WEBERS with another 75 HORSES should be 12 MPG!

Its tuned and already performing optimally....balanced and dynoed....

You didn't say what year your engine is from, but the 2.7 Rennsport engine produces 210 HP.  1973 911 weighed a little less than 2000 lbs.  Your IM may weigh slightly more, but not likely more than 200 lbs. over the 911 weight (my SAS coupe weighs 2200+ without me in it).  Even if you smoked every shift, your mileage is suspect, as your title for this thread indicates.

There are lots of sites that report mileage on Porsches of every year and HP, all of which disagree with the mileage you state in your post above.  However, if you and your mechanic are satisfied with the mileage you're getting, keep the pedal down.

Had a 1970 Boss 302 Mustang  for 12 years. Never once checked the gas milage. The point of the car was to pin you to the seat while accelerating and burning rubber . drove a Prius to atone for my sins.

I guess I was mistaken. I read the title, "IM6 GAS MILEAGE STINKS" and thought that you were (justifiably) dissatisfied. I know that I would be.

Rick Davis has a car and a 2.7 engine just like yours (only with PMOs) and he gets significantly better mileage. Dave Mitchell had a 3.0 with the big Webers and got significantly better mileage. I've driven both cars, they ran like scalded dogs.

If you're satisfied with 10.5 MPG- great (I guess), but you don't need to be in order to run well. But if that's the case, I guess I'm missing the point of the entire thread.

With my 3.6, I can get close to 30 mpg highway driving.  I've never tried to find out what it is around town.

The main problem with these S6 builds is that they go through CV boots like water, and Henry has not been able to correct the problem.

Stan Galat, '05 IM, 2276, Nowhere, USA posted:

I guess I was mistaken. I read the title, "IM6 GAS MILEAGE STINKS" and thought that you were (justifiably) dissatisfied. I know that I would be.

Rick Davis has a car and a 2.7 engine just like yours (only with PMOs) and he gets significantly better mileage. Dave Mitchell had a 3.0 with the big Webers and got significantly better mileage. I've driven both cars, they ran like scalded dogs.

If you're satisfied with 10.5 MPG- great (I guess), but you don't need to be in order to run well. But if that's the case, I guess I'm missing the point of the entire thread.

Almost 90% of my driving is on 2 lane beach road/30 to 40 MPH stuff as nearest 4 lane is 16 miles away. Car weighs 2340 and I'm 200 pounds with virtually NO highway driving. Once a week, I get out on interstate for fun/errand and open it up. Would be nice to get better mileage and will look into it, certainly, but car, now rides/idles/accelerates/etc BETTER than it has at any time during my short 3 month ownership! so I'm hesitant to rock the boat.

After reading a dozen bleeps from RENN/SAMBA/etc., it appears that most HONEST City driving is reported in the 12 to 14/15 range and I am at the LOWEST end of that. Will look into discussion with my mechanic for explanation and understanding.....

Here's something else to check.

How are you measuring miles between gas stops? The trip odometers on these cars are famous for failing - often they keep advancing but show fewer miles than actually traveled.

The Chinese repops that many of us have are much more likely to fail than real VDO gauges, but the 'real' ones can go, too (I don't know which you have).

If your trip meter IS working, remember never to reset it while the car is moving - doing so can wreck the little plastic gears inside.

Maybe I am cut from a different cloth but gas mileage just doesn't matter. Yea it would be great if you were getting in the 14/15 range but what's the cost per year... $50. It is a hobby and supposed to put a SEG on your face. If you are concerned about mileage get a damn Miata or a Boxster.  

That being said I average about 30 MPG on the Suby  The nice thing about the GPS gauges is the trip odometer is dead on accurate. 

Bob: IM S6 posted:

The main problem with these S6 builds is that they go through CV boots like water, and Henry has not been able to correct the problem.

He would have to modify the chassis angles so radically that the engine you have wouldn't fit right. Most IMs have this similar problem.

I know the issue. 

And it's not most, Rusty, just those with extreme axle angles. 

Bob: IM S6 posted:

I know the issue. 

And it's not most, Rusty, just those with extreme axle angles. 

 

INDEED...my mechanic expressed similar concern when first checking out car....but he was impressed with the build AND that the the 6 cylinder chassis configuration with the EXTREME angles, necessary to achieve the build IS the issue ! Small price to pay for having the SIX(?).

Yes, it's a small price, but it's an annoyance to have to change the CV boots frequently.

I live at 6500 ft and I get 14mpg on my little 1915 with dual IDF 40's. I can get over 20mpg on a road trip. My last 911 Cab did 19/28mpg. I do not think anyone that owns any flavor of these babies really gives a **** about mileage. After 125 miles I need to get out of the car anyway. 

majorkahuna posted:

I live at 6500 ft and I get 14mpg on my little 1915 with dual IDF 40's. I can get over 20mpg on a road trip. My last 911 Cab did 19/28mpg. I do not think anyone that owns any flavor of these babies really gives a **** about mileage. After 125 miles I need to get out of the car anyway. 

Banzai - even with your spirited driving, that seems quite low mpg (not that it matters, as you said). I wonder if the tranny has been modified for overall lower gearing (car revving at 80 like a tall 4th gear), perhaps with a lower geared ring & pinion. 

Its all moot, because it's purring, you're driving it as it should be and enjoying the sh*t out of it...and I'm jealous!   

I've got no dog in the hunt- if you're  happy Banzai then I'm happy to.

As for me, I really don't care about the gas mileage for the sake of gas mileage. I do care about it because crappy mileage figures with a 200 HP motor in a 2000 lb car indicate a problem. Guys with Kadrons just have to live with horrible mileage because there's very little that can be done to make it better. But part of the promise of Webers and Dellortos is the ability to tune the engine for "crisp" performance, which in turn yields better mileage.

Ive got a 2276 that's making north of 180 HP at the crank. When I'm dialed in, I get about 25 MPG on the highway. I've gotten as much as 30, but my idles were awfully lean until the car was fully warm.

If I had 40s on a 1915 and was getting less than 20 mpg, I'd feel like something wasn't right.

Your mileage (as they say) may vary. 

I guess I am glad to have an EFI car with OBD.

Again, the gas mileage doesn't really matter...smiles per miles, as they say 

Stan Galat, '05 IM, 2276, Nowhere, USA posted:

I've got no dog in the hunt- if you're  happy Banzai then I'm happy to.

As for me, I really don't care about the gas mileage for the sake of gas mileage. I do care about it because crappy mileage figures with a 200 HP motor in a 2000 lb car indicate a problem. Guys with Kadrons just have to live with horrible mileage because there's very little that can be done to make it better. But part of the promise of Webers and Dellortos is the ability to tune the engine for "crisp" performance, which in turn yields better mileage.

Ive got a 2276 that's making north of 180 HP at the crank. When I'm dialed in, I get about 25 MPG on the highway. I've gotten as much as 30, but my idles were awfully lean until the car was fully warm.

If I had 40s on a 1915 and was getting less than 20 mpg, I'd feel like something wasn't right.

Your mileage (as they say) may vary. 

Just to be accurate....the car DYNO'd at 227HP/ Balanced to 7400 RPM and car weighs 2340 empty.....I RARELY have seen the highway as it is 16 miles away from home and 90% of driving is on a 2 lane road at under 40mph so not even close to HIGHWAY MILEAGE scale......so my  reference is NOT usual and customary! I do occasionally hit the highway for half hour and hit it hard passing/weaving at 80/90 mph but NO TALL 5th and revs high.....perfect for Hawaii with almost NO highway interstate and almost ALL 2 lane roads.

I would expect your 2276 to get 25mpg on highway and MIGHT approach 20 myself if I had HIGHWAY(LOL).

If I was on the mainland, i would change the gearing AND I'm not sure why the original owner did the BUILD the way he did. But NO COMPLAINTS on that front, OTHER than would be nice to get a bit better mileage just like I'd like to be able to do 40 pullups rather than 23!

So the apples/oranges reference is quite different than a 1915 @20MPG highway . We have almost another LITER displacement, different car weight/gear-ratios(7:31RING and PINION) and almost NO HIGHWAY mileage.....the parameters are NOT typical by any STRETCH. Again always looking for EFFICIENCY and PERFORMANCE within given parameters.

I'll take it any day and suffer with my conundrum

Cool.

A VARIETY of BLURBS ON INTERNET: gas mileage 2.7RS...folks who get 25MPG are usually 87 years old, legally blind, and wearing STUTTGART DIAPERS

1I have a 73T that gets in the low 20 mpg range but I do very little city driving. I've used87 Octane gas for years with no problems.

2. Honestly? "72 T with stock everything? Expect an average of 15-19. A lot depends on your driving routes, your driviing habits..__

3.Now my pump is worn pretty good and it is pumping to a 2.7RS half spec bastard child and I probably get 15+ in town.

4I went from about 18 mpg to 12 when I switched to 46 PMO's

5I have been running PMO's on my 83SC with 3.0 for several years now they are very nice. I can get 17 mpg on the highway if I drive easy.

Used to average 37 mpg on back roads doing 60-65 mph in my IM with the 2.0 L watercooled VW/Audi.  In some ways it was a pretty amazing car.  Now I get 0 mpg since I don't have a car.

Hey Bob I'm assuming Henry has tried the off road boots.  Honestly, eating CV boots was my car's only problem.  Sold it before I needed to change them again.  I was very honest with the buyer and gave him 4 off road boots ($125) to try when the current ones fail.

BANZAI wrote:  "Just to be accurate....the car DYNO'd at 227HP/ Balanced to 7400 RPM and car weighs 2340 empty....."

Interesting.  I had my car weighed at Carlisle by Danny P., and it came out at 2400 lbs.  I guess the sixty extra pounds comes from the larger 3.6.

Not sure what my hp is, but the engine was all rebuilt last year, and stock figures were 272.  I have a more free flow muffler, and a Steve Wong chip that adds 16-18 hp.  So, I guess I'm in the 290+ range.

Phil:

I've been working on two CV boot solutions:  one with Henry, and one with a local Porsche racing shop (that one would require some modification to the rear shock mounting bracket to allow larger boots to fit).  It's the extreme axle angle need to fit six cylinders into a 356 engine bay, even though the wheelbase gets lengthened, and the rear fender openings moved back.

Other than the boots, I - like you - have had no other issues.  Well, except that I can't find too many roads where I can open it up beyond third gear, and even third gets me way over any speed limit... 

Bob: IM S6 posted:

BANZAI wrote:  "Just to be accurate....the car DYNO'd at 227HP/ Balanced to 7400 RPM and car weighs 2340 empty....."

Interesting.  I had my car weighed at Carlisle by Danny P., and it came out at 2400 lbs.  I guess the sixty extra pounds comes from the larger 3.6.

Not sure what my hp is, but the engine was all rebuilt last year, and stock figures were 272.  I have a more free flow muffler, and a Steve Wong chip that adds 16-18 hp.  So, I guess I'm in the 290+ range.

MY APOLOGIES on the numbers: actually 217 HP/Balanced to 7400 RPM. My guess is your 3.6 easily approaches 300HP.......and NOT TOO many places to really open it up here other than a 10 mile stretch of H2 with some curves and hills that are a HOOT for 80/90 MPH for a few minutes. Sometimes you can zip up thru the pineapple fields(2 lane road/hills) and open it up.....

My mechanic was very  impressed with HENRY's build and that he was able to  turn a 911/930 into a SPEEDSTER. He was more concerned about the fatigue of metal in the extreme angles than the CV BOOTS but welcomes any remedy that you may stumble on....his response was, " if you feed a vegan a steak, expect him to PUKE!" He says expect some idiosyncrasies with a slightly MUTANT build....I'm game...

I'm a bit confused. What is/was the intent of this post?

My original thought was that it was created seeking suggestions to remedy poor fuel economy, but that doesn't appear to be accurate.   

Or is it simply to inform the group that an IM6 has poor fuel economy, but a blast to drive?  Not saying that's wrong, just wondering what was the intent.

By all means, I didn't purchase my speedster with fuel economy in mind.  The only time I ever thought about fuel economy was last week going to wine country; I knew the complete trip mileage since I have done that exact route a millions times, so it made it easier to figure out.  

Thanks-

kevin

SF-Speedster posted:

I'm a bit confused. What is/was the intent of this post?

My original thought was that it was created seeking suggestions to remedy poor fuel economy, but that doesn't appear to be accurate.   

Or is it simply to inform the group that an IM6 has poor fuel economy, but a blast to drive?  Not saying that's wrong, just wondering what was the intent.

By all means, I didn't purchase my speedster with fuel economy in mind.  The only time I ever thought about fuel economy was last week going to wine country; I knew the complete trip mileage since I have done that exact route a millions times, so it made it easier to figure out.  

 

Thanks-

kevin

 

Having owned a couple of 911s(all factory 80s/bought new), I was a bit SURPRISED at how LOW the mileage is on the IM6. I realize that driving a stock fuel injected 911 on the mainland, including MUCH highway driving(my lifestyle back then), is NOT at all congruent with driving the IM6 with TRIPLE WEBERS in Hawaii, largely local driving on 2 lane road for 90% of time/daily driving/stop and go....

My INTENT was just to report my surprise at the consumption.....not really to complain OR seek suggestions for remedy. I have since gained both KNOWLEDGE AND perspective and have a better handle on why and it's fine....AND welcome suggestions for improvement/efficiency of function. 

Just reporting some new eye opening experiences....with an UNUSUAL automobile that seems to have some application/interest to SOC. It has been fun, certainly, and I've gained new found respect for the MADNESS and tinker management of ownership. Just thought I'd get better mileage WITHOUT clearly thinking it thru but happy and satisfied nonetheless(3 words in one)

Found some additional BLURBS on RENNLIST FORUM: interesting range

1.I get 15 mpg in my 2.4T with Webers

2. 16mpg with my, fairly stock '71 911T 2.2l with Webers. This was back country road driving and very little freeway miles

3. Around 15 mpg, 2.4 L 1973 911T with CIS running Chevron Supreme.

4. When I had my '72E w/ Webers, I got around 15 mpg around town

5. In town, my 2.4S MFI gets around 12-15 depending on my right foot. On the highway,19-21 mpg

6. 911S (210hp) coupe: 14 - 17 mpg

7.Using 91 octane in mostly city driving, I get about 15 mpg in my stock '71 T (2.2 liter.)

8. Great point with the Right Foot theory. When I switched out the 2.2 w/ zeniths and replaced w/ the 2.4 and 46 Webers...on the German Autobahn #7 from Wuerzburg to Schweinfurt, I averaged 8-10 MPG

Interesting when my 1.9 liter 4 banger with Webers gets 14mpg, compared to the huge 2.2 liter 6 cylinder with Webers gets 16mpg. Seems like mox nix to me. It is important to note that my pistons are BIGGER than yours. LOL.

majorkahuna posted:

Interesting when my 1.9 liter 4 banger with Webers gets 14mpg, compared to the huge 2.2 liter 6 cylinder with Webers gets 16mpg. Seems like mox nix to me. It is important to note that my pistons are BIGGER than yours. LOL.

 

 

INDEED: mileage can be personal as per heavy foot/light foot(LOL)

I am NOT surprised at 1.9/14 vs 2.2/16 vs 2.7/12(40WEBER 3 BARREL) as the angle of the dangle is inversely proportional to PISTONS from NANTUCKET!

I'm THIRSTY: how's about we stop for a drink? I BET YA I can drink more than you can?

Schwing!!!!!!

It's all about the smiles per gallon for me...Want to trade?

crhemi (Bill) poboiinhawaii posted:

It's all about the smiles per gallon for me...Want to trade?

NOT A CHANCE....LANCE!