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Before owning a '90 NA Mk III I owned a 1998 Toyota Camry. It was a commuter vehicle with Toyota's 2.2L 5S-FE inline four. Moderate power but on flat highway driving I was routinely getting in the mid to high 30's for MPG. I loved my '90 Supra for the Sport roof and look of the vehicle. At 200 hp in 2005 when I bought it I would be lucky to beat a stock Honda Accord but that didn't matter as racing and speed were not what I wanted out of the car.

I am now in a situation wherein I have a 110 mile per day round trip commute and will possibly for the rest of my career which could be 20 more years. I would like to get another MK III but frankly, 15-20 MPG isn't going to cut it driving that much. I know lots of people here have done swaps to get MORE power, has anyone done/looked into replacing the 7M-GE with a smaller, more efficient engine? I have thought about the 1JZ-GE non-turbo but am curious to know if an engine like the 5S-FE would work. I am assuming up front a V6 probably won't fit correctly, even if it was more efficient.

For those ready to say "This is complicated" I have a close relative with a state of the art auto shop who works on everything from Fords to Mercedes and Rolls Royce. I have expertise I trust completely to do this, what I want to know is how big a job is it to accomplish done right. I also have the budget. I commute because the job is high paying and well worth it.
 

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I also have the budget. I commute because the job is high paying and well worth it.
Have a fuel efficient daily driver and have the Supra for a once a week in nice weather kinda car.


Easiest way to get better mileage is to put in a lower final drive.
I imagine that at 110 miles it's mostly highway. If so this option will work, just expect the car to be much lazier around town with the lower gearing.

For reference, I managed 26mpg highway at 600whp on 91 octane with lower gearing, mostly around 90mph. For a 5 speed you'd be looking for something in the 3.58 range for the differential.
 

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You should be able to get 25 MPG on the hwy with the Supra motor, can't ask for much more than that.

For reference, you would be changing to a "higher" gear, not lower. Higher gearing is lower numerically, and visa versa. Good luck finding that as the one you would want would likely come from a V8 car, and you would have to deal with speedometer re-calibration.

Al
 

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Discussion Starter #5
Have a fuel efficient daily driver and have the Supra for a once a week in nice weather kinda car.
This will be my second job with a 110 mile commute; in fact, the Supra was the car I had back then. Having the Supra is part of what made the drive tolerable. There wasn't a single time I'd leave for work and not appreciate my car. I'd take the top off, turn up the stereo and cruise. I live in the Houston area now so cold weather is infrequent. Hot happens all the time but in a targa roof the air conditioner is still effective even with the top off.
 

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can you move closer to work ? I can't imagine spending that much time a week commuting

I would drive a prius on that commute man and save the $$ on gas (it would pay for itself w you milage). but, driving a prius means tucking your balls away and also giving up any semblance of something enjoyable to drive. I mean sure a prius has ac and windshield wipers, but joy to drive (compared to a normal car) it is not. 50mpg though... sd can't beat that

back to the burning question at hand, a motor swap for mpg. Im thinking modern small displacement turbo diesel. something like an audi a8 tdi. since your in texas a supra that can roll coal would would make sense too ( no cold starts)
 

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No one makes a lower 5th gear for your current transmission?
If not, then you would want to go with a more powerful engine that has a transmission that was originally paired with a higher final drive than what's on your car.
Another route you could go is swapping in a 6spd box like the 370Z transmission.
 

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can you move closer to work ? I can't imagine spending that much time a week commuting
No. It isn't bad and there is no traffic congestion. It's a long way but 90% of it is at highway speeds.

I'm thinking modern small displacement turbo diesel. something like an audi a8 tdi.
The VW/Audi TDI's are attractive. The big questions are how complex is that and how reliable. The 1JZ is bolt compatible with the 7M so that is about as easy as it gets. The 2JZ is a little more complex but not outrageous. Putting a completely different manufacturer? I can see so many ways that could be an issue. It's like that song "One Piece at a Time." "The transmission was a 53 and the motor turned out to be a 73 and when we tried to put in the bolts all the holes were gone."

Reliability is also an issue. I bought my MkIII with 90K miles on it and sold it with 160K. In that time the only maintenance I did was standard scheduled maintenance. Not one single repair because something "broke." My aunt had a A6 that was a garage queen. I drove my Camry 30 miles with no coolant once and the engine didn't even overheat.
 

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If you're going to swap a new engine in I would certainly not do diesel, and would never do anything from VAG. Put a V8 in it that has that tech where it kills half the cylinders when cruising.
 

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As Madison MKIII suggested, moving a little closer to work if possible works out if you plan on being at that job for a while. If moving is not an option, I'd get a separate car for daily driving. Probably a turbo diesel. If not I'd go for a 1JZ swap. Filling up the tank twice a week isn't as bad in Texas as it is in other places. Paying $4 or $5 per gallon is not fun for premium gas. Never know what'll happen with crude prices either:/
 

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That's coastie pricing. TX we get 93 for half that. Toll roads are 85mph, and we don't have emissions. The state inspection rules just recently made a windshield a requirement.
You guys are living another life down there. I'll be hoping I dont have to wait more than 3 more months for a 60 degree day without rain...
 

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You guys are living another life down there. I'll be hoping I dont have to wait more than 3 more months for a 60 degree day without rain...
That's why buying a boring car isn't worth it. We can do anything we want with the cars here, and there are rarely cops on toll roads. He lives an hour away from his job, that means his cost of living is cheap as hell, and driving a fun car is just that, fun. He can afford to do a good swap, there's no need to put a pos VAG diesel in it, and for what? He'd have to change the whole fuel system, and VAG got sued into the dirt for lying about their MPG. Swapping a V8 into a RWD car is super easy, and super cheap. Just add a fuel pump and you're good to go. Hell, run carbs, don't even need to worry about all the electrical. Put a rear end that has a lower gearing and just let the torque run through it sipping gas at 75mph @ 1500 RPM.
 

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"just add a fuel pump and you're good to do"

??


as if in some parallel universe a carbed v8 (or even a v8 with displacement on demand cyl deactivation) is going to somehow be more efficient than a 3L fuel injected toyota.

OP didn't say he wanted simple or reliable.

the entire premise is kind of silly anyway when you consider gas can/will go to $4 ++ at. some point. i mean it its 60 miles of boring highway wtf does it matter what car your in (in some ways..)

another better option (than any v8) how about a small 1.6 4age. you could turbo that. there are rwd trans available. it does not use diesel.
 

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Why in the world would you go to a lower power and smaller engine? If you want fuel economy you move to a larger more powerful engine, and basically idle down the highway in near stoich/lean.
 

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because of internal rolling resistance of the engine signalpuke

secondary to combustion volume (surface are of cylinder walls). a little bit of fuel is not burned right next to the cylinder walls. more cylinders that are bigger = more wasted fuel

more piston rings to slide up and down more bores, more drag.

more bearings to oil (v8) = more drag and also bigger oil pump (which also = you guessed it more drag)



a v8 is always going to have more parasitic drag than a 4cyl

don't believe me?...then why are manufacturers going towards small turbo engines in their fuel economy cars ? hell in their trucks now too, small turbo gas engines are the way to make mpg

a chevy cruze with its 1.4 turbo will be way more efficient than a LS powered GTO. any day.

ps, all engines run down the highway at stoich. that is why virtually every fuel injected car on earth has a narrow band 02 ---to run at stoich, under low load conditions (cruise, light acceleration)

your v8 will certainly use more fuel at 1500 rpm vs a 4age at 3000 rpm. rpm is not what makes an engine efficient.
 

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Otto cycle engines are not efficient at all. If you want good mpg, you put a larger motor into a smaller chassis, and mate it to a longer gear set. I've swapped most of my past cars with larger engines and longer gear sets. NA K20 CRX that ran 12s and got 40mpg, would just putt around in 6th gear doing 30mph in town, because it had enough low end torque to move the chassis. Same car could break loose on the highway at 60mph by downshifting into 4th. If you want mpg, you use gearing and torque to your advantage, not HP. It's pretty basic. Geometry alone for a V8 vs an I4, same dimension cylinder, the V8 will have more torque down low and use a lower duty cycle injector. That same geometry limits the upper rev limits, which in turn will limit the HP/L.

Yes, they're putting small turbo motors in cars. They're designed to be fast spooling and provide low end torque, which is mated to a longer gear set. They're not designed to provide any high end power.
Why bother putting a handicapped pos engine into a car when you can swap something larger for the same price? If it was worthwhile to put a shit TDI into a car and get performance out of it, people would be doing it. They're not. They're swapping Honda K-series into everything because it has the most power per litre out of anything in its size, and is basically bulletproof up to 800 hp stock other than needing upgraded valvesprings and retainers. I've seen this engine swapped into everything, MR2, Silvias, Miatas, RX8s and even AWD STi, not to mention every Honda on the planet from the Beat to the NSX. They even swap it into the old Mini Coopers and Lotus Elise.
Not one TDI swap. VAG is junk.
 

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haha you say that like I am a audi fanboy
or like I am a fan of this fantasy better mpg motor swap

not!

lets not get twisted here, there is a turbocharged 7m under my hood and race gas in my tank. def no commuting with my supra. but I enjoy pontificating on others projects...

and we are in agreement they are junk (audi+diesel). but we are talking about mpg, and in the real world these cars ..a8 tdi etc (dependable or not) --- or any small turbo diesel car (vw etc) -- get excellent mpg

I am talking about the pure principal : how to extract the most useful energy out of 1 gallon of gas

a tiny modern 4cyl will be able to produce more work from 1 gallon of gas than a huge v8. the v8 is going to waste some energy because of friction loss. Im not talking about max output of the engine...im talking about how much physical work is extracted from x amount of fuel. the size: rotating mass, ## pistons, displacement are factors in how efficient a motor can be.

same goes for compression ratio. two identical engines, but with 8.5 :1 vs 11:1.....the higher compression will always be more efficient.

same with fuel injection. high pressure 1000's psi direct injection will always be more efficient than basic 35psi fuel injection

to get the best mpg you would also have to give up wide tires and swap to low rolling resistance spec (which have noisy ride and shitty grip).

but the mk3 does have good aerodynamics going for it. does help balance the pig weight of the car
 

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I've read Heywood's book, I understand how an engine works. None of what you're saying has anything to do with the fact that putting a more powerful engine with taller gearing will make for a more efficient long distant drive because the motor will be under almost no load and near idling.
Replacing a crappy 30 year old engine with an even smaller crappy 30 year old engine is just throwing away money.
Swapping in a tiny diesel is just throwing away money.
V8s are cheap, and easy to swap. Best bang for the buck, and you then have tons of room HP wise to expand. Also very cheap to repair or upgrade.
 
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