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-   -   $500 and 30mpg car? possible? (https://ecomodder.com/forum/showthread.php/500-30mpg-car-possible-704.html)

olderthanme 01-18-2008 07:25 PM

$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...
Engine:
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.
NO EMISSIONS TO PASS!!!


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.

Modification:

Cylinder head:
Higher compression(10:1), high squish, 1981-1984 Maxima cylinder head (maybe with a singh groove added too:thumbup:) 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.

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

Exhaust:
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.

Driveline:
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:
http://www.geocities.com/z_design_studio/

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...

SVOboy 01-18-2008 09:24 PM

I would get another car, one that can get 50mpg, like a metro or crx? The datsun would take a lot of work, I think, and aeromods would need to be part of that, prolly, :p

elhigh 01-18-2008 10:25 PM

Definitely put the older heavy flywheel back on. That extra mass absorbs a lot of your quick power output when you're dragging and that's when you don't want a heavy flywheel. But when you're looking for max mpg, more rotating mass is better - it makes it easier for the engine to coast through its dead spots in the power delivery cycle, and delivers smoother power pulses to the drivetrain. In FE, smooth is good.

Why stop at 175/65 tires? Keep looking and try to find 70's or, be still my heart, 75's. I don't think anyone is making them, or else I'd convert my truck to tall, skinny 15's tomorrow. You may find some luck in this arena searching among the VW sites - those old 15" wheels were like pizza cutters.

XFi 01-18-2008 10:38 PM

Nice ride! Always liked the Z cars. I had a 79 280zx and an 82 280zx turbo. Fun cars. Ever consider tracking down a diesel and going bio? The Datsun/Nissan Diesels in the Maximas (like the '82 pictured) should drop in pretty easily. Shouldn't be to difficult of a swap (as far as gas to diesel swaps go).
http://www.imageno.com/thumbs/20080119/0q4voclsulyp.jpg

http://www.imageno.com/thumbs/20080119/4zo1jhgq8y7h.jpg

But if you are just looking for a $500 commuter that gets good mileage...I would have to agree with SVO. Keep your toy and get a metro. :o

olderthanme 01-18-2008 11:28 PM

Actually I just parted out a LD28 engine. Still have some parts laying around. The LD28 crankshafts bring in too much $$$ to justify actually using one...LOL
The problem is that they are front sump and need to be at least mid sump.
One option is drilling out the other boss into the oil gallery and bocking off the old pickup and using a Z oil pickup/pan.
They do get 40MPG and even more with a turbo...Hmm.
There is a youtube of a diesel 240Z or 280Z blazing by at like 80mph.

I have considered getting another Z and going bio but I dunno. Maybe if I find a cheap 280ZX (much better aero than the gen 1 Z cars).

Aero mods are also in the plan... HybridZ.org went to the wind tunnel once and are going to go again this year sometime. They got down to .396 with a fairly stock body. I think with some more mods a Z that is still streetable could get down to .35 with some custom front end treatments.

roflwaffle 01-18-2008 11:45 PM

Look around for fixer uppers. Just about any four cylinder lightweight should do.

userdoubleo 07-15-2008 09:37 PM

Ok. Start with the basics, block the rear wheels, aka:cover em. Block the grill, part of it, it is an older car so it probably needs some cooling. Replace the old radiator fan, it is probably inefficient. But yeah, thinner tires is very good. If you know how to grab a long last gear, aka: so at highway speeds the engine is going only 1400 ~ 1800 rpm. That will give killer highway mileage. If you don't mind an "ugly" car consider a boattail or full underbelly for some serious mpgs. If you go all the way, $500 might be enough to pull 40mpg (if you can pick'n'pull a smaller engine at half-off days with an old rusted, busted trade-in).

Thats all I got right now...


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