1966 olds dynamic 88 daily driver/ cruiser

[Beagle]

you can hop them up but they have a couple of shortcomings. Nobody builds hotrod pumps here, you end up with European builders who are a bit pricey... the pumps don't have a huge reserve built in but are quite adequate for their design. The pump elements aren't big enough from the factory to move enough fuel to make huge HP numbers like you would need for a 12 in a 4000 pound car. A hotrodded pump can reach or exceed the price of a used Cummins here and the MB guys who beat on the OM617 kind of indicate you're on borrowed time after 300 hp. When you think about what it was designed for, that's pretty significant in it's own. I think some of the original non-turbo models where what, 88 hp?

SBG on here has done some homework on the Isuzu mills, some of which are very much like a 4BT cummins. My favorite Isuzu buildup is this one:

http://www.4btswaps.com/forum/showthread.php?3300-67-Ford-F100-with-Isuzu-4BD1T/page1

He implied that he was getting 30 or so mpg and it probably made enough snot with the compounds to get it into the 12's. It won't be cheap unless you know folks to get parts from or have good fab skills or both, and then "cheap" is a flexible term.

If I wanted to get close to your goals, I think I would get an LS, all the sensors, and the transmission out of a rolled truck / suv. A 6.0 or 6.2 would help gas mileage and run pretty strong out of the box. They're big enough to make torque like an American V8 should, but not so big you have to feed it with a garden hose sized fuel line. It'd be a fair amount of work. Look at SilverBuick or Matt Cramer's threads for a primer on what it takes for sensors. There's something like 120 pins on an ODBii computer and on a GM I think you have to get the body computer (BCM) as well for the transmission? I could be wrong there.

On a mechanical diesel, you need some wires too. Alternator and starter... maybe a glow plug relay and fuel solenoid (kill switch) if you get all fancy... and a big budget for transmissions and a rear end. I would take a bunch of measurements as I kind of question whether the NV3550 will fit in the tunnel. Speedway has a decent catalog for roundy-round dirt car stuff like hydraulic clutch pedals. I'm not real sure how well you will like trying to speed shift that trans.

On the easier to do, doesn't leave your car on blocks forever end of the scale, you could probably find a 200-4R overdrive and try to find some higher numeric gears for the rear and it would be a good start. The lower gears would help it accelerate around town. You wouldn't have to lean on the gas as hard to get it moving. The OD theoretically could help on the highway, depending on how carried away you got with the rear gear.. For the money, I think it would be the most effective start. You will "feel" the gears immediately.

[yellomalibu]

I keep seeing that lower rpm's equals better mpgs, and it just hasn't been my real world experience. MY 66 Olds with a 425 2 barrel and 2.73 gears got better gas mileage at 70 than it did at 55. My 84 C10 with a 305 and 3.08 gears (no overdrive) got better gas mileage at 80 than it did at 70.
I can only guesstimate that engines are "happy" or more efficient at different rpm ranges, and while some of that can likely be tuned with carb and timing adjustments, the cam, intake, valve sizes, compression, exhaust size, etc probably also play a role.

[Beagle]

Getting it moving up to 70 is probably what is killing the average. More gear and more gears would help that I would think... although driving dad's camry is a trip. At 65 it's always coming out of fifth gear on hills, at 75, it doesn't.

[38P]

I keep seeing that lower rpm's equals better mpgs, and it just hasn't been my real world experience. MY 66 Olds with a 425 2 barrel and 2.73 gears got better gas mileage at 70 than it did at 55. My 84 C10 with a 305 and 3.08 gears (no overdrive) got better gas mileage at 80 than it did at 70.
I can only guesstimate that engines are "happy" or more efficient at different rpm ranges, and while some of that can likely be tuned with carb and timing adjustments, the cam, intake, valve sizes, compression, exhaust size, etc probably also play a role.

Must be like the old EPA estimates . . . "Actual highway mileage may differ."

Engine efficiency is a factor. But if an engine is tuned to run on an economical mixture, more times than not, sucking in less air into the engine (smaller CID, lower r.p.m.) and pushing less air aside with the body (less frontal area, lower m.p.h.) is going to result in lower fuel consumption.


Graph from an old study that shows the impact of speed and transmission gearing on fuel efficiency

(There's a good graph of this from last year's 40 MPG Compact Sedan comparison test at http://www.motortrend.com/roadtests/...n/viewall.html but it won't paste in here)

In cars that provide real-time data (e.g. injector duty cycle, mass air flow) the results are obvious.

[hiroshima1320]

Gm ls based engines are pretty much where i was leaning. They are relatively efficient relatively affordable, have the option of the t56, and running stock or aftermarket pcms is fairly straightforward, well documented, etc. I'm just not entirely sure I can reach my mileage and power goals with the same engine. (Turbo and boost dependant tuning possibly?)

[38P]

Putting ~4,000 lbs. into the 12s could be accomplished all sorts of turbocharged GM engines.

Which one depends on how committed you are to the m.p.g. target, how much money you want to spend, and how many parts you want to make at home, and how much technology you want to employ (or avoid).

Larger engines will require less boost and allow for hitting the power target on lower octane.

Truck engines will tend to be cheaper and have more "bolt-on" support.

If I was doing the project . . . .

I'd be tempted to go with a built turbo Aurora for a unique (actually show-stopping), all-Olds vibe (an Aurora core ought to be almost a giveaway at the JY, but it will take some fabrication skills to convert it to RWD . . . These guys know how to do it: http://www.chrfab.com/Transmissions.htm )

. . . or a turbo'd six, to improve off-boost fuel economy. (You could go as small as 3.1 liters and still stay below the 135 h.p./liter threshold where things start to become more expensive)

The cheapest route is likely going to be to use a 4.8 Vortech. But that one won't really "turn the crank" for a fair number of folks.

[Deaf Bob]

I keep seeing that lower rpm's equals better mpgs, and it just hasn't been my real world experience. MY 66 Olds with a 425 2 barrel and 2.73 gears got better gas mileage at 70 than it did at 55. My 84 C10 with a 305 and 3.08 gears (no overdrive) got better gas mileage at 80 than it did at 70.
I can only guesstimate that engines are "happy" or more efficient at different rpm ranges, and while some of that can likely be tuned with carb and timing adjustments, the cam, intake, valve sizes, compression, exhaust size, etc probably also play a role.

For some reason.. Must be because I had 2-327's at the time but 1825 RPMS sticks to me as the best efficent RPM for those motors.. I was shooting for cruising RPMS there to get the best MPG My papers on that stuff are long gone... 30 years ago..
Seems you want alot of toeque at that RPM. The transition from torque to hp is always 5252 RPMS

[Beagle]

Putting ~4,000 lbs. into the 12s could be accomplished all sorts of turbocharged GM engines. ...

Sure - and get 30mpg. I'd recommend the Duramax.

[38P]

It would be easier with a diesel.

[hiroshima1320]

Matching the amout of power required to maintain a steady set speed, taking into account vehicle weight, coefficient of drag, rolling resistance, etc is a very complex equation. Not to mention an engine that is efficient at the rpm made possible by the gear ratios available. The diesel option sounds good. However withe the additional cost of diesel it is not as cost effective.

[Beagle]

Engine cost aside, it is cost effective when the fuel cost 20% more but you go 30% further on it...

you car is probably a .50 cd, I'm guessing minimum of 25 sq. ft. of frontal area. Rolling resistance .008 with modern tires,

http://purplesagetradingpost.com/sumner/bvillecar/bonneville-Index.html

Diesels excel at low fuel consumption for load, which is where the average is gonna come up from. Accelerating that mass is, as you already noted, very hard on the economy.

A 4.8 LS with a turbo might be an interesting combination to look into. The BSFC on the LS is pretty decent. A turbo mill would likely prefer premium, fuel costs start levelling with diesel.

Any of these options are gonna be a bunch of tanks of gas at 10mpg. How many miles a year are you driving?

[hiroshima1320]

Wouldn't a relatively small engine be counter productive? Woud it not be laboring too much to be efficient? I would think a 6.0 with a low boost turbo set up would be ideal as far as ls based engines go. Producing more torque down low for an efficient burn at cruising speed and be to make big power in the boost. I'm not normally concerned with economy, but I put 10k plus on the car last year. I plan on more than that in the future. I know turbo cars can be much more efficient, so I wonder if I can get boost in at low rpm for cruising, potentially a second, larger turbo for higher rpm power? I know that typically creates the valley of death, but with a 6 liter engine and speed trans, that may be negligible..

[Beagle]

disclaimer: My understanding of all of this is pretty primitive, basically I'm just another jerk with a keyboard.. I believe a lot of the generalizations below are close, but if I'm way off base maybe one of the resident genius' will correct me.

I think it's all about packaging. Look at something like the Dodge Charger, smallish V6, 300 HP, 30 mpg, pretty damn big car. I'm betting it's over 4100 pounds. How do they do it? Eight speed transmission is worth a few mpg's. Keep it in a gear where it's not loaded up and laboring at high throttle positions for long periods or spinning needlessly and generating frictional losses, you pick up efficiency.

A 4.8 wouldn't be laboring on the highway. You probably need less than 50 hp to go 75-80 with the patio like aerodynamics of a 60's car, which it should make pretty effortlessly at 1500-2000 RPM. I've never driven a turbo gas car with a gauge, I'm not sure if they are making boost or not at highway speeds. A couple of pounds wouldn't surprise me too much, where you might see some efficiency improvement recovering some of the heat energy normally blown out the exhaust pipe.

The trick, as I see it, is where you put the balance point on the performance v. economy teeter totter. The 4.8 with a turbo or a pair of turbos is more than capable of putting the car into the 12's and getting decent economy for a mobile cinder block, but 30 is a stretch. Either build it to run 12's or build it for economy and accept that it may not run 12's. Buick Grand Nationals were the closest I can think of getting what you are asking for and I never saw 30 out of one. High 20's, usually trending downwards because it was just too dang fun to hotrod them.

The aero starts really hurting economy around 60 on the older cars, I don't think the 55mph national speed limit enforced on us back when was just some random number they threw down. Somebody like my sister would get better mileage at 70 than 55 because she was always in a hurry and every pass went into second gear at 55 where it would stay in high gear at 70 and the engine was closer to it's torque peak so she didn't have to give it as much gas to get the same "feel" of acceleration. On a flat steady state drive (never happens), with no load or wind changes, it takes less HP to push the car at 55 than 70. The math says you will get better economy with the combinations that Detroit was putting out, and I still find that to be true. I can believe that people with more aggressive driving styles than mine will get different results. That's not an insult, just offering what seems to me as a plausible explanation of *maybe* why some folks get better economy at 70 than 60. I don't know anybody besides me that can actually drive 55 and not go insane.

so.. is the smaller engine with some boost that is recovering some of the energy normally blowing out the exhaust more efficient than a larger engine loafing along? I can say with a certain degree of surety "It depends" haha. A direct injection gasoline engine is the only way I can think of approaching 30 with the profile of the car at 70 or 75. The BSFC requirement is probably gonna be somewhere around .35 lb per hp per hour. Good traditional gasoline engines run closer to .42-.50's from what I've seen. DI engines would do better. DG has been doing ECU calibration full time as I understand it. Maybe a specific thread for BSFC would encourage his and others "in the know" input.

When I stop to think about it, I get more confused all the time but I basically see it as we are trying to generate a turning force. We do that by exploding a fuel in an enclosed area and harnessing the combustion process to get our turning force at the business end of the crank. We have demands for X amount of torque to produce X amount of work and the transmission doesn't care how the torque got there. Assuming the same chamber, on a multiple piston engine, you should get less mechanical losses with 6 pistons at a combustion pressure equivalent to that generated by 8 pistons (6 cylinder with boost, 8 cylinder NA). gak, nevermind. I'm going mental trying to describe the way I see it.

There's a ton more to it, like how much drive pressure it takes for the device (turbo, blower), back pressure pumping losses with a turbo, belt or drive losses with a blower. Throttle blades cause inefficiency as well. A small engine running WFO producing X amount of power should be more efficient than a larger engine with a small throttle opening if everything else is the same. I say "should"... What it gets down to for me is how to get X amount of torque and whether the engine can produce that much where X is a variable demand and ultimately, how much fuel does it require to generate X. A really small engine in it's torque peak range running wide open "should" be more efficient than a really large engine loafing. The BSFC numbers vary by RPM, and from what I've seen, those numbers get better the closer to torque peak you are.

my head hurts. If I really understood all this well enough to put it in words, I'd probably need full time psychiatric care. The short version gets down to quality and quantity of combustion pressure for a given amount of fuel. Diesel has more energy potential than gasoline per volume, which is why the MPG and 1/4 times in the same sentence usually makes me blurt out "Diesel".

Now I'm wondering about the supercharged 3.8's. Great.

[Deaf Bob]

Fact is my 6 cyl powered 4X4 chevy SWB got worse mpg than a 350 powered one and same as a 454 powered one.. All 3 were same except motors!

[Beagle]

My 110cc Honda damn near triples my 5hp briggs for number of hours run per gallon, and makes twice as much power and my weedeater makes .9 hp / cubic inch but sucks gas. It's like comparing lemons to white sugar to chalk... Any engine can be made to work in an RPM range where it does not have it's best BSFC and be made to get really crappy economy compared to the "Sweet spot" you guys are talking about.