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Old 01-18-2008, 07:25 PM   #1 (permalink)
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$500 and 30mpg car? possible?

Hey Guys,
This is a great forum.
I currently have 2 cars.
My daily driver is a 2004 Nissan Frontier crew cab short bed with the 3.3 liter V6. 17-22mpg.(which is why I want a fuel economic car...)

My toy: 1974 Datsun 260Z.
Stock the CD is .454 with a frontal area of 18.5 ft^2 (BAD!!!)
The car has a 2.6 liter inline 6 making around 130 horsepower stock.
My car is gutted and being lightened as much as possible as it will be a gas guzzling twin turbo race car down the road. In 2010 I will be transplanting this race engine and drivetrain that I am currently building. Until then the car is open to whatever mods that I want to do and I want MPG!

The car has these mods:
Coilover suspension(ride height adjustable from 3" to 7") with adjustable stiffness Tokico Illumina strut inserts.
$400 SPEC lightweight 11lb flywheel (still have original 26 lb flywheel that may go back in for better low end torque)
$400 SPEC clutch that can hold 250hp.
15X8 steel rims with 225/60R15 cheapo tires
upgraded 4 piston front brake calipers from a 4X4 toyota pickup
removed dash and replaced with a 2LB aluminum dash that I fabricated. (35+ Lb weight savings)
More comfortable and lighter Eclipse seats...and some other little things like a new wiring harness Etc...
flat-top pistons from an earlier model Z(raising the compression ratio to 9.2:1)
earlier model, more powerful, twin SU carburetors(have been giving me trouble for 4 years, need rebuilding)
now rebuilt block with new gaskets and bearings(same pistons/bore though) as of Winter 2007.
Mallory 6A ignition
long-ish tube header and 2.5" exhaust to hollowed out muffler(loud!)
Engine short-block has probably 15,000 easy miles left on it before it gives up the ghost.

I would like a car that I can daily drive to school and back for the next 2 years with $500 in the car itself. I can either modify the Datsun with the money or get a disposable Geo Metro for a couple hundred and sell most of the parts on Ebay to help make up the cost difference.

My thoughts:
Use the 260Z and modify it to produce the best MPG. It's already got cheap insurance from being 35 years old. ($30 a month...LOL)
Many guys are making almost 30MPG on modified 300 horsepower turbocharged varieties of these Nissan L6 engines.
I can get a cylinder head that is setup for fuel injection for $100 and increase compression to 10.2:1 (should be fine with Chevron 87-89 octane gas.)

I think lowering the car to the most extreme reasonable limit (3" ground clearance) and narrower yet tall tires will help my MPG.
I was getting about 17 MPG and definitely not driving economically. Maybe I could get 20MPG with the engine in the current state with carbs but refined driving style.


Cylinder head:
Higher compression(10:1), high squish, 1981-1984 Maxima cylinder head (maybe with a singh groove added too) for more low end torque and detonation resistance over the current open chamber head. I can sell the head when I'm done with it for around $150.

1975-1976 280Z non-EGR EFI intake manifold with a cold air intake.

I think I could put a restrictor right behind the header in-between the flanges to help with low RPM torque. Not really willing to put another muffler on it though.

1981-1983 280zx non-turbo 5spd transmission, heavier old flywheel, the newer clutch, stock ratio differential.

It looks like I can cruise at 70MPH at 2600RPMS with the later transmission, 175/65R15 tires, and a stock ratio differential. Now it's more like 3300RPMs at 70MPH which is deafening with the loud exhaust.
Used this calculator:

Pics and description of car here

If 30-35MPG can be attained, which I think it can, then I'd defiitely go for it.
Especially if I drive it like you guys do.
I don't really want to get another car and have more insurance to pay. Would consider it though...

I'd like to hear some input from you guys...

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