mOtOrHeAd MiKe

iTrader: (8)

Our LeMans wagon is going to be backed by a 4L60E, 3.08 gears and 28" tall tires... should do well on the highway. Project cost is estimated at $10-12K.

Forcefed86

iTrader: (4)

Miatas are about as dorky as it gets IMHO...

Rx7 swaps are the way to go! Look at norotors.com for ideas. The engine bays are huge in the 86-91 models.

When I had the 2.73's in my 86 RX7 with the 200-4R OD trans and L/U converter I would see over 30mpg highway at 70+ and click off mid 10 second 1/4 mile passes.

Had a mildly built 3.8 (buick grand national motor).

Very comfortable to drive. Sold it for $6500. Was roughly 2750lbs with out driver.

aknovaman

iTrader: (7)

Just buy a used VW diesel off craigslist for about $3k and be done with it. 45-50mpg. Do a muffler delete and a cold air intake. Burnouts are easy and the straight pipe turbo sounds cool too. Upsolute performance can burn a chip for the factory ECU for better performance.

garys 68

iTrader: (1)

That is the most logical and practical answer on here.
You should be kicked off this board immediately.

redtan

iTrader: (5)

Miata, 240sx or rx7 would be my choice.

Put in an aluminum 4.8, t56 and 2.73 gears.

Wouldn't be surprised if you could pull mid-high 30s with that thing and still scoot pretty well due to the power/weight ratio.

BadWolf

what are some ways to actually get better mileage with the yukon?

would it be possible to add a tune that would get better mileage? less fuel at cruise and idle?

redtan

iTrader: (5)

Weight reduction and lower numerically gears.

Technically you should be able to do a custom open loop tune, but would require a very good tuner and you should really have at least 1 (if not 2) widebands in the car to monitor AFR.

gofastwclass

iTrader: (2)

One of the first problems with a Yukon (or any truck / SUV / van type vehicle) is you are trying to drive a brick wall down the highway. Aerodynamics on those vehicles suck plain and simple. Weight is the next factor, but not nearly as much while moving at steady state (i.e. highway) as aero unless you are accelerating or decelerating.

There are some things within the engine, exhaust, drive train and PCM calibration that can help a good bit but in the end it's still a brick wall from an aerodynamic perspective.

aknovaman

iTrader: (7)

Perhaps go fast should throw up his mpg and vehicle weight as a sample of what can be done with a custom tune. Plz don't mention who did the tune or how it was done as the tuner is not a sponsor.

ls1nova71

iTrader: (4)

Although it's probably a tad outside the 12k budget, an early 2000's 6 speed Corvette, as G Body said, would be my choice! They get around 30 mpg on the highway. If you're dead set on doing a swap though, you could put a 4.8 in it! Probably have the only one of those around.

OR, you could just get one of those hydrogen generator things that I have to hear about from my neighbor every time he comes over. His Jeep Liberty gets like 100 mpg or something. LOL!

Forcefed86

iTrader: (4)

I just bought a 99 vette 6spd last year. (for 12k actually!)

While it does get 30mpg or so crusiing 70 in 6th, I still average 15mpg or so by the time you figure city driving in. If I baby it a week I can average 18mpg. Still not great IMO. Something lighter weight with a taller gear is the way to go.

BadWolf

my suburban (04 2wd 5.3L) is averaging about 12-13 mpg city/highway lol i really thought it would get a little better then that but its been super cold so i think thats made a bad difference

also i think my clutch fan is on all the time. im really considering a swap to electric fans

Forcefed86

iTrader: (4)

That may give you a whole .02 mpg savings.

IMO cheapest and easiest way on your current rig would be to buy cheap tires as narrow and tall as you can fit. Then run alot of tire pressure.

MX6.0

I think a lot of that depends on which state you live in. If my car were pre-96 it would have never passed the sniffer test with no cats or emissions equipment. Here they only plug in the obd2 plug and look under the car...too easy.

It's going to be tough to find a car that's lighter and is as easy to swap as the Miata. I'm running a 3.23 rear so it'll cruise at 80mph at 2K rpm. I've never kept my foot out of it long enough to get an accurate mpg, but I'd imagine it would be pretty good.

BadWolf

well my thoughts are if the fan is dragging the motor down that could cause a loss of mpg

i had a 5.0 mustang years ago that had a clutch fan that went out. it was doing the same thing my burb seems to be doing, sounds like an airplane driving down the road. i picked up 3 mph at the track taking it off, thats basically 30hp

im sure your probably right though, probably wont make that much difference but i figured every little bit would help

operatorfailure

iTrader: (3)

I have thought of building a mpg ls car. I would do it to prove you can do it, not to save money. If it was done to save gas you're so far in the hole to start you will never make it up. I think you could build a turbo 4.8 in a 240 and get 25 mpg on the hwy and run low 11's fairly easily.

Jason454

Unless your looking for a project it would be cheaper to drive the suv you have. 10-12k plus an extra car to insure and maintain every month.....equals a lot of gas.

gofastwclass

iTrader: (2)

Latest MPG was high 23, low 24 -ish highway at roughly 70 - 75 MPH. Vehicle weight is around 3700 with a full tank (without me or the lady). I would probably do better if I didn't drive so fast...

1997 Thunderbird lowered 1.5 to 2" with 16" factory size wheels:
Gen III 5.3, electric fan, 4L60E with a junkyard transmission cooler, 3:23 gear with "411 style" custom tuned PCM using a 99 Corvette intake, LS6 valve springs and a Muscle Car oil pan kit. True 2.5" dual exhaust into 2.25" factory Thunderbird mufflers using some butchered and hacked (i.e. poor flowing) C5 corvette manifolds up front. Modified aftermarket custom air intake for a 99 Silverado.

I feel there is room for improvement if I build some good flowing short or mid length headers (nothing factory fits) and adjust the air intake to work as a "cold air" / ram air setup at speed. Right now the intake picks up some bleed through air from inside the engine compartment if stationary, however while moving the air temps stay within 3 - 5 degrees of ambient.

I realize not everyone has fabrication skills, but people astonish me with these 10 to 12K builds for essentially stock cars. My original budget was $2000 excluding the price of the vehicle which I already had and got cheap. Everything in my swap except consumables, the Silverado cold air kit, LS6 springs and driveshaft are straight from the junkyard.

Full details on the car and budget are in my signature.

fieroguru

iTrader: (1)

Here's the build thread:
https://ls1tech.com/forums/conversio...peed-swap.html

cobalt964

out of budget range, but light, super simple, fast, fun, and good mpg. 1974-1986 Porsche 911 with 5.3. 28mpg. 2280lbs.