Fuel economy and horsepower - best combo

How can readers enjoy their cars while spending less?  With gas selling at $4 + per gallon, fuel economy is a major factor in our ability to enjoy our cars.  Many readers drive their projects regularly.  I'm on track to drive about 8,000 miles this year between my '67 lemans and my '65 Bel Air.  

What can I do to increase both power and horsepower in my cars?  These are not necessarily mutually exclusive goals.

Would anyone be interested in an article that competed for best fuel economy in a powerful car?  The guidelines that I would use are: 250 or 300 HP at the rear wheels, curb weight over 3,000 lbs, and better than 15 second quarter mile time.  This would be targeted to street drivers.  I would like to see what kind of numbers could be generated and how they did it.

I would be very interested in the best combination of engine displacement, camshaft selection, gearing, etc.  

I thought you said you were going to drive your car? I put 4,100 miles on just my Skylark in September =P  I'm probably going to have about 14,000 miles on it this year, and the engine was out of the car June-August

My car currently get's 17mpg and is at least as quick as 13.3sec @ 106mph and there is more in it for both mpg and quarter mile time.  It weighs almost exactly 3800lbs with me in it and a full tank of gas, more than that with spare tire and such.

I had averaged 19.5mpg before I pulled the engine in June, but changed a bunch of things and am still working my way back up to it.  At 106mph it should have easy 12's in it and I think there is more mph in it as I don't have the tune nailed down yet, and will probably be capable of 11's but I'm installing a scattershield before I start doing high rpm clutch dumps off the line.

I've had a slower 455 in it, a ~320hp one, that averaged 23mpg highway, 18'ish around town. I think I can get over 20mpg with the current combination, which when dialed in should be kicking a bit over 500hp by the parts and cam in it.

The key is a good overdrive, a dialed in tune with timing and fuel for both cruising and track and then being easy on the gas pedal while driving.  IMO, getting a distributor dialed in for OD cruising and track is a major pain, battle of comprimise.  
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The Silver Buick- '77 Skylark coupe w/ a Fuel Injected Buick 455&TKO-600, '72 Centurion Conv't - 455w/TH400, '67 T-bird 4Dr (suicide) w/428&C6. '69 Firebird replaced!

http://www.bangshift.com/forum/index.php?topic=6189.0

djvpontiac:
How can readers enjoy their cars while spending less?  With gas selling at $4 + per gallon, fuel economy is a major factor in our ability to enjoy our cars.  Many readers drive their projects regularly.  I'm on track to drive about 8,000 miles this year between my '67 lemans and my '65 Bel Air.  

What can I do to increase both power and horsepower in my cars?  These are not necessarily mutually exclusive goals.

Would anyone be interested in an article that competed for best fuel economy in a powerful car?  The guidelines that I would use are: 250 or 300 HP at the rear wheels, curb weight over 3,000 lbs, and better than 15 second quarter mile time.  This would be targeted to street drivers.  I would like to see what kind of numbers could be generated and how they did it.

I would be very interested in the best combination of engine displacement, camshaft selection, gearing, etc.

I think the article would be a good idea, if you could break it down into 2 categories, "Modern" EFI w/Overdrive transmissions & "Vintage" Carburetor equipped with "non" overdrive type transmissions, if it was a competition the EFI computer controlled overdrive equipped cars would have a serious advantage over the earlier carburetor "non" overdrive equipped cars, especially if turbo charging was allowed, or maybe do a computer controlled & "non" computer controlled categories with any available transmission option... I think the Modern would win hands down... JMHO  
"Fill Your Library Before You Fill Your Garage"   Good luck "Budnicks"

Silver Bu knows of what he writes.

The keys to fuel economy with decent performance are:

1. Lowest possible mass air consumption at cruise (the optimal combination of slow engine speed and small cubic inch displacement)

2. Highest possible part-throttle thermal efficiency within fuel octane limits (expansion ratio)

3. Highest possible average cylinder pressures (within octane limits) under acceleration.

4. Accurate control over appropriate lean part-throttle mixtures.

Thus, the best blend of economy and performance is going to be a high-compression, small cube engine, with good heads, closed-loop fuel injection, and a relatively mild cam (or even a Miller/Atkinson-Cycle camshaft), that's boosted within an inch of its life by an alcohol-fueled, charge-cooled turbo system.  Gearing would be deep overdrive at cruise with a multi-speed transmission to boost torque during acceleration.  (If this sounds a lot like what Ford's doing with their EcoBoost engines (excluding the alcohol and high-boost elements), you move to the head of the class)

The UK "Wizard of NOS," Trevor Langfield, would likely counter that a progressive pulsed nitrous oxide system on the same engine would yield better average fuel economy than a turbo(off the bottle, of course).  

As for a 300+ h.p./3,000 lb vehicle . . . an old Thunderbird Turbo Coupe mill hopped and swapped into a smaller RWD chassis (Fox Mustang, Pinto, Mustang II) would fit this bill nicely on a microscopic budget.  
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460_BBF_Turbo-in-CC (formerly Dr511scj) "This guy has no life other than posting endlessly on carcraft.com." -- Car Craft, July 2005
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October 1, 2003: " I'm thinking a couple of...turbos, blowing through an old Powerstroke intercooler...on a Super Cobra Jet-head 460 would be mad cheap and make sick power."
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"I have no problem with your...talking to several versions of yourself...or pointing out our failure to do a turbo story ...." --Douglas "CC/Rambler" Glad

Silver Buick,
Unfortunately my travels don't currently take me more than 10,000 to 12,000 and once there is salt on the roads my classic cars stay put until a good rain cleans the streets.  So I'm happy with 8,000 per year between my lemans and bel air.

Which car is giving you that performance and mileage combo?  It's hard to imagine a 455 getting 19.5 mpg.  How to you measure it? I've calibrated my odometer against mile markers so I know what I'm getting is real.  Is that mpg a combo of street and highway or pure highway?  My Lemans is getting consistent 10.5 mpg from tank to tank with a blend of highway and city.  My Bel Air just got 12.8 mpg.  Neither car has an over drive yet but that won't help much for local driving.

How do you set your timing for economy?  For performance, I've always advanced the timing until I get pinging under hard throttle and then back down a little til it disappears.  I've never played with the springs to impact mechanical advance curve.  

Budnicks,
I agree the computer controlled should win.  I'm personally interested in the carberated version of the article be even a bench racing version with suggestions on cam selection, carb selection, displacement comparisons would be useful.  All things being equal will a 283 that makes 250 HP be more fuel efficient than a 350 that makes 250 hp?  What would be the trade offs?  

460 BFF,
You are way beyond me technically but I follow some of what you are saying.  Let's get more specific.  My cruising car is a 65 Bel Air.  Currently it has a 283 with a powerglide.  The books say the engine is worth about 195 hp - when it was new.  In comparison to the 330 hp crate engine in my LeMans, the care is anemic.  I'd like to see about 250 hp and some solid torque to make the car more drivable but I'd like to keep the mileage up.  For now I'll leave the power glide but may change to a 5 speed or an automatic with an over drive at some point.  In the mean time I'm considering engine options.  Here are some choices:
1) Rework the 283 to get to the 250 hp point.  What would you recommend here?  Vortec heads? a small 4 barrel, headers?
2) I have a 383 (350 block with 400 crank) that needs a rebuild.  What could i do with that?  Vortec heads?  May not be the best choice for mpg but I already have it.
3) build up a good old fashion 350.  Again your recommendations?

If all three were built for minimum 250 hp, how would the mpg vary assuming they were all tied to the same trans?  

I measure my mileage two ways.  I have a set route that is exactly 220 miles of non-stop highway driving I make semi-regularly.  I know that if I fill up at gas station A, that pulling up to the pumps at gas station B is 220 miles, GPS'd the route so many times I don't even bother half the time now, been running it for over 6 years.  The other way is on road trips, I keep a log of fuel put into the gas tank and a GPS'd mileage (though now I know my odo is 4% off from these records), so that over the course of a couple thousand miles I have a talley of fuel in the car and it averages out pretty nicely. Tank to tank can have variations depending on how you fill up the car.  I've seen as high as 22mpg, but I don't put much stock in that number, and consider it more of a flyer and the pump being finicky.

BTW, when I had the lo-po 455 in it, that got 23mph highway, it was likely an easy 14 sec car, I just never got to a track in that combination (and I was worried about breaking the 7.5" diff at the time).

I had a '69 Firebird with a lo-po 400 in it, that with a 700r4w/lockup and 2.73 gears out back averaged 18mpg around town and 25-28mpg on the highway with a Q-jet and points. That was my college car and I was thankful for the mpg's!  It was slow though with the 2.73's, barely making it into the 16's, though it was traction limited... A converter, gears and sticky tires may of got it into the low 15's or better, but may come with an mpg penalty.

I'm currently working on a theory of reducing pumping losses by putting a bigger cam in the car to kill vacuum.  However I'm running into the bottle neck of what is the leanest fuel mixture that can burn and still come up with usable power because less vacuum means more air molecules in the cylinder and leaner AFR when compared to a high vacuum (more pumping losses) cam, looking for maximum HP and maxium mpg.  It's a balance though.

If I could fabricate a massive EGR system, to pump inert gas into the intake to effectively reduce the displacement of the engine, I'd try that, but I'd want it computer controlled (which I can do with the megasquirt).  When I EFI my Centurion I may retain the EGR and see if I can increase the mpg's by kicking the EGR all the way open or closed with an electro-vacuum switch.  It is just a theory though, if the gasses are homogenized it may not burn well.  
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The Silver Buick- '77 Skylark coupe w/ a Fuel Injected Buick 455&TKO-600, '72 Centurion Conv't - 455w/TH400, '67 T-bird 4Dr (suicide) w/428&C6. '69 Firebird replaced!

http://www.bangshift.com/forum/index.php?topic=6189.0