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Old 08-21-2008, 10:49 AM   #1
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Less Obvious MPG Underdogs

I would really like to get some of you people's take on this. There's quite a few cars out there, that don't get exceptionally great gas mileage, that have lots of potential hidden under it's skin. If there's people improving a stock civic's gas mileage by as much as 50% with lower gears, aeromods, and basic engine modifications... what are the less likely candidates?

Lately I've been thinking about how cool it would be to get a Lexus SC400 (or even LS400) for dirt cheap and strip it out, even removed non-structural sections of the chassis. Get the weight as low as possible, and imrove the aero as much as possible. The engines in these cars have also been put into LESS aerodynamic cars above and get up to 35mpg, with MORE HP than the stock 260.

Today I got the bright idea that a LS400 around $1000 would make a GREAT LeMons race car, as selling bits and pieces might bring it down just around the $500 entry limit.

But what other cars are there out there that might have some insane potential once stripped of all it's needless garbage. People like me aren't concerned about having AC, power steering, even heat! Just because a car has an engine with lots of power, doesn't mean it can't still be efficient.


Top of my research list is BMW and Mercedes. Maybe Volvo?
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Old 08-21-2008, 01:22 PM   #2
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Weight isn't that much of a factor except around town where start/stop cycles consume more fuel. Even then good driving technique can get rid of most of the around town "inefficiency".

Still I really like your idea. Light is right in my book. I love elemental vehicles, all I need is an engine, wheels, seat and steering wheel. Lotus Super 7 is my current favorite.
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Old 08-21-2008, 01:30 PM   #3
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i think 4 cylinder trucks are a pretty good mpg underdog candidate as they usually have really spread out gearing so a longer rear would really stretch out the top gear. also, they can be fairly light and are probably the best candidate for the boat tail since you wouldnt have to subtract anything, you would just be putting something over the bed. the same is true for convertables, as with the ragtop, they have a hideous .cd

i dont know if anything with a v8 would be a good candidate to break 50mpg.
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Old 08-21-2008, 03:37 PM   #4
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Current 400+ HP V8 cars with 6+ liters are nearly getting 30mpg with pushrods, and pushing heavy bricks of cars.

It's never about displacement or cylinder count. It's about friction and power/air ratio. If a V8 has the same rotating mass, and same friction as a 4 cylinder, they're cosume the same amount of energy in paracitic losses. Then it's all about how much power the head is making for a given air quantity.

The V8 in the lexus is DOHC, and a narrow valve head. What does this mean? It means it can run very high compression with few hot spots, and it also means it has great low lift proporties, good for low end efficiency. It's also all aluminum, and about 410 pounds stripped of AC, PS, and the chuncky stock intake manifold.

It's also only 4 liters... pretty small for a V8.

Nonetheless, a 4 banger truck would do very well I think. I was talking to a guy today that's only getting 22mpg in his 4 cylinder truck (90's) and it's almost entirely highway. He's not the most economical driver, but still... Scary to think a new GTO would get better gas mileage.
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Old 08-21-2008, 03:56 PM   #5
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Agreed... My grandfather's Mercury Grand Marquis (I think its an 06) gets darn near 30 MPG highway @ 70 MPH with the a/c on & no hypermiling tactics. Same with my great aunt's old 88 Lincoln Town Car with a fuel injected 302. That car got about 27 highway with no hypermiling. We actually had it down here in Virginia for a few years before & after she died. We called it the PimpMobile (White w/ a white vinyl top), and had a great time in that car. For some reason full size Fords get fantastic highway mileage with no hypermiling required.

-Jay
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Old 08-22-2008, 07:48 AM   #6
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Gollum, just get Honda VX or Insight or a scooter. Mods only get you so far, and most of them are useless anyway.

Oh, and you are not going to get a Lexus dirt cheap ...unless you are looking in to putting some quality time with a frame machine.

Not trying to put you down, just my take on it.

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Old 08-22-2008, 08:22 AM   #7
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you mention rotating mass. what about reciprocating mass? its the reciprocating mass that really kills you with more displacement. in theory, the only way to really get the fuel economy from a v8 that you get from an i4, is to compress the powerband and every behavior of the motor across all throttle positions to half the rpm.

anyway i do believe the lexus can be a good candidate, but you will hard pressed to get passed 50mpg
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Old 08-22-2008, 08:48 AM   #8
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I live in the bay area. I can find the SC400 and LS400 in GOOD shape under 200k in some cases for under $2,000 ALL DAY LONG. Just hop on our craigslist. Used luxury cars become dirt cheap around here once they pass a certain age and they aren't shiny anymore. Once the new models have been around long enough for the old models to be forgotten about, they become relegated to pimpmobiles with 30 inch rims. (no joke) This actually creates a pretty good market for what I'm thinking, lots of possibilities.



Very true, I agree. There's lots you can do to reduce reciprocating mass though. I mean, I know a guy that got his aftermarket pistons on his datsun L28 down to nearly half of the weight of the stock pistons, on an engine that sees around 300 NA HP, and revs to 8,000 regularly. It's a 3 liter setup, so he's gettig 100hp per liter on a very old cylinder head design. His pistons have held up fine.

Now, that's a bit more work than I really want to do honestly. But that's why I've been looking into the SC400. The 4 liter V8 has a very light engine through and through, and the stock pistons and rods are decently light. These engines also have a very nice throttle responce and rev very smoothly and quickly. The stock reciprocating mass has been known to operate at 8,500 and beyond even with nothing more than cams and springs. In australia the oval track racers are getting these engines to 11k on stock crankshafts.

But I honestly don't know enough about the other options there are in many other cars. One can only know so much about so many cars, and I'm lacking in experience with a LOT of vehicles. Hence asking for other's ideas.
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Old 08-22-2008, 09:26 AM   #9
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There are people with Vette's who get 40mpg hypermiling. They get around 28-30mpg on the highway driving normal. Very light car and decent aerodynamic drag though (.28-.29).
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Old 08-22-2008, 11:24 AM   #10
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Wow, $2K for Lexus is a good deal, I'll give you that. So, lets focus on MPG.

Here is data from fueleconomy.gov, I believe that is the best independent source of vehicle fuel efficiency data that we have to date that is consistent and covers a wide range of models:

99' LS400 Fuel - Premium; MPG city/highway/combined: 16 / 23 / 18
99' GS300 Fuel -Premium; MPG city/highway/combined: 18 / 23 / 20

Compare with:

01' Insight Fuel - Regular; MPG city/highway/combined: 48 / 60 / 53
94' Civic VX Fuel - Regular; MPG city/highway/combined: 39 / 50 / 43

If you want to get good fuel efficiency, why not start with a baseline that's 150% higher?

I mean, you can take a lexus and use mods and driving techniques to get %5, %10, %15 improvement in MPG, but if you starting with something that's x2 times more efficient to begin with, you'll be that much further ahead!

Ross
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