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Discussion Starter #21
the pig weight of the car
Let's talk about this, too. I have read in the past the complaints about the weight of this car. One person pointed out the insane number of electric motors in the car for the n ways adjustable electric seats. Assuming my plan is to drive with the roof off as much as weather allows, which in Houston is a substantial fraction of the year, where is weight savings available?
 

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isn't it flat as shit in texas ? or was that just the panhandle area - most of my trips have been there

weight will not help much there if its flat and not a lot of stop and go. I bet really lame low rolling resistance tires, possibly even a touch smaller/ not as wide (Im crying inside as I type this) would give you the most bang for the buck

really though, any effort you spend in the name of "better mpg" has to net a return. and no motor swap will ever do that, just buying a touch (and keeping same engine) more gas will always be cheaper.

now if you had to replace stuff thats a different story. of if your aiming for some odd duck mpg build yeah it could be fun to spend a little on it. spend a little time over at prius chat and see how the freaks there get down ---aka the extreme end of doing mpg mods--they squeeze more mpg out of already high mpg cars and the same ideas apply to the supra
 

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I wouldn't trust an electric motor for long range driving daily. A full EV? Perhaps, but so much more goes into those cars than you think to give them good range at high speeds.

Signal puke, I wasn't suggesting a diesel engine swap, and certainly not an old one. An actual diesel daily driver, they aren't horrible to drive and give great highway mileage. Having a 2nd car that's for pure fun is what I'd prefer if I didn't do a 1J or 2J swap. A V8 with cylinder deactivation and longer final drive is a great idea but at what cost? And how well would that integrate into an older Toyota:/
 

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V8 swaps are pretty easy and cheap. Plenty of room in the engine bay of the Supra. Should be just about the same as swapping an LS1 into an FC, FD, S13, S14, etc. Search around for threads on those swaps to get an idea of what's required. Basically universal LS mounts welded in, and then whatever transmission you want to use. Might even be an adapter already for your current transmission.
There are also videos on youtube of MkIII supras with the swap, so I'm sure there are build threads somewhere.
 

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Signalpuke, you have a very, very odd conception of what will make a vehicle more efficient. No offense but you're completely missing the mark.

Every engine has a different set of conditions it needs to run at its maximum efficiency. A lot of it has to do with how lean it can run the engine while cruising, while not causing damage or excess long term wear. Less moving parts (or weight) in the engine is a factor, as is reducing internal engine drag. Sticking a v8 in there that takes 30% more effort to turn over at cruising speed is not going to net you better fuel economy. An engine with less parasitic loss from drag while having a tune that will let it run at, or more lean than stoic during the varying load conditions will burn less fuel.

An example of this is the FR-S/brz/86 platform. Those engines have very little internal drag, but they rev at 3250ish during cruise on the highway. This in itself may take less energy to turn it over than a big v8, BUT with relatively light load conditions the engine needs to run relatively rich in order to prevent light load detonation. This hurts fuel economy.

There are way more factors at play here than have been discussed. Generally speaking, a well tuned smaller engine with a power band that matches cruise RPM will net you the best fuel economy.
 

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I'm speaking from experience. Putting a larger engine in, and a longer gear set, is the easiest way to get better fuel economy. I understand all the internal friction stuff you guys are talking about. If you want to compare two engines to each other, then sure, put that into the discussion, but that's not the point here. Otto cycle engines, regardless of cylinder configuration, are NOT efficient at all. Gaining a percent or two of efficiency due to less internal drag, or less rotational mass, it not going to increase fuel economy like putting an engine in the car that can move the chassis down the highway with ease at 1200-1400 RPM. A V8, by design, has the low end torque to do this, and it won't break a sweat doing it. It's cheap, it's easy, and if you want more power in the future, it's not going to cost a lot of money to do it.
 

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so you have taken an already 20+ mpg car, with a 4/6 cyl engine that was already fuel injected and swapped a v8. and got better milage? Im calling bs

cheep and easy to swap a carbed v8 sure. not to hard to swap an LS (5.3 etc). but come on, cars with those motors from the factory generally got much worse mpg than the supra

the op original premise, I have a supra with a 7m and i want better mpg, is not solved in any way with a v8 swap.
 

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Signalpuke, I can speak from experience as well. I lost my old credentials but I had a v8 supra for a long time. Your anecdotal evidence just isn't cutting it for me haha.

In order for the big v8 to make that torque it needs to burn a set amount of fuel. Put simply, a set amount of fuel mixed with a set amount of air has the potential to make a set amount of power.

Inefficiency wastes this "set amount" of potential power. A more efficient engine will send more of that power to the wheels instead of bleeding it off as wasted heat. That v8 running at 1500rpm may take more or less energy to run any given 4 cylinder at 3300. The comparison is how efficient the engine is at extracting that potential energy, and how much is soaked up by the engine internals.

This is a science discussion my friend. Not an anecdotal evidence discussion. Again, not trying to toss turds around the room here and offend everyone. Just trying to educate.
 

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Ask anyone that has swapped an FD, they get high 20s, low 30s on the highway with just an LS1 and T56. I don't know what rear end is in the MK3, but if you are going down the highway at just above idle, then I'd expect mid 30s would be very easy to achieve. It's not a difficult concept, you put an engine designed to move a heavier chassis, into a lighter chassis, and run longer gearing to keep highway RPMs down.
 

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In the future someone may come up with a electric motor swap and a battery pack where the fuel tank is now. That would be interesting. Until then, practicing hyper mile driving is about all you can do. Accelerate gently, get into the next gear as soon as possible on a manual tranny, coast when you can, don't race up to stop lights, 35 psi tire pressure, let the dumb asses that want to race you pass by. About the differentials, manual transmission cars came with either 3.91 or later 3.73. On the face of it, 3.73 looks like 5% better mileage but the EPA fuel economy website doesn't show much of a difference. City driving you're looking at 16 mpg. Highway driving you can get about 24 - 25. For the best mileage check your tuneup items like spark plug gap, timing, throttle position sensor and dashpot, the VSV's that operate the starting pressure up on the fuel pressure regulator, EGR VSV, air cleaner filter.
 

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A V8, by design, has the low end torque to do this, and it won't break a sweat doing it.
Maybe not, but it will break a spindly rear axle that was designed for an in-line 6. Have to change the rear end for that swap (with custom fabrication), possibly to a Ford IRS 8.8 from a Cobra. And that's where you get your taller gears from. They do make a 2.73 for that rear.

Al
 

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it is all about volumetric efficencies.

it is always better to be at lower RPM and and higher engine load for better overall VE.

Op

point blank a 110 mile commute is a 2+ hour hike one way (yes expect to always be closer to two hours than not due to weather, accidents etc), honestly that will be unsustainable long term. Ideally you need to get closer to that job regardless of mode of transportation.
 

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A competent tuner (or you) can make your car run pretty lean under certain conditions and not sacrifice driveability. One of my other non 2jz high power turbo cars gets excellent mpg on the highway if I'm not driving it like an animal.... and that's with E85 too..... because I tuned it that way.

I know this isn't an "engine swap".... but a lot of your mpg is in the tune. Making more torque at a lower rpm makes a huge difference as SignalPuke mentioned above, but the trick is being able to make the torque without using a lot of fuel to do it. And how long can you do this without torching exhaust valves from high egt. You don't want to set your shit on fire/glowing red to save a few dollars on gas do you?
 

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Let's talk about this, too. I have read in the past the complaints about the weight of this car. One person pointed out the insane number of electric motors in the car for the n ways adjustable electric seats. Assuming my plan is to drive with the roof off as much as weather allows, which in Houston is a substantial fraction of the year, where is weight savings available?
Easy: seats, driveshaft, wheels, brake calipers, carbon fiber hood, rear seat removal.
Medium: aluminum bumpers, plexiglass / polycarbonate windows.
Hard: break out the hole saw and start figuring out what you can live without.

However, I feel this is missing the point. A Mk3 Supra is entirely in its element on the highway, and removing weight from the car won't really help with mileage in steady state cruising. Has been mentioned, the 3.73 differential is your friend here, transmission swaps are also an option. The T56 has a wide ratio gear set with a 0.50 sixth gear that I want for my car, but it won't pair well with most Supra differentials, even if you are doing 85 mph.

From experience, my 89 Supra weighed about 3900 lbs with me in it, had a 1jz-gte at roughly 340whp, and 3.73 differential. I'd routinely get high 20's (think 27-28 mpg being the norm), and even saw a touch over 30 mpg on one occasion. From other experience, our 2000 LS400, which is completely stock, gets 30-32mpg quite easily at highway speeds.

If I were building a Mk3 for mileage, I'd focus on the easy weight reduction stuff, but leave the interior alone. Heck, upgrade the stereo, they're great cars for that. I'd leave the roof on and windows up, because aerodynamics, although... I wouldn't blame you for removing the roof. I'd research reasonably safe and legal hypermiling techniques. As for the engine setup? Two things come to mind.

One, the VVTI 1UZ from the... everything. Seriously, these engines were Toyota's version of the small block Chevy, you can find them everywhere. Efficient, reasonably powerful (which is useful, in a heavy car), and, a point that I feel has been dramatically overlooked in this thread, THEY ARE CHEAP. If gas is cheap in Texas, and your whole reason for starting this thread was to figure out the best way to squeeze the most out of $2/gallon gasoline, at some point you have to consider the math involved. How much project Supra costs are you willing to spend in hopes of extracting more mileage from each gallon? You're putting on a lot of miles, yes, but $10k worth of Supra project buys what, roughly 5000 gallons of fuel? Which, at say, 25 mpg, takes you... 125k miles, or roughly 1100 (rounding down) trips at 110 miles.

All this math talk is why I can't understand electric car owners sometimes. Yes, a Tesla is a neat car, but for what they cost, you can buy a REALLY nice LS400 (or 430, 460...) for a fifth or less the cost, have a nicer car, AND drive it for a lifetime or two before the cost of gas and maintenance has equaled the purchase price of the Tesla. So, while us enthusiasts have perhaps missed the point here, I think this whole thread is about math and financial sense. To which I must say...

Supras don't make financial sense. They're something we do for the emotional reward of driving them. :)

The other, perhaps more obvious option here, is to just do what Toyota did, and install the "fuel efficiency special" engine that was designed for exactly the hypothetical question that is the basis of this thread. I'm talking, of course, about the 1JZ-FSE and 2JZ-FSE. Look them up sometime. Good luck finding one (I've only ever seen one or two pop up on ebay over the years), and if you find one, you'll have your hands full adapting it to work. But, if you can pull it off... 40mpg Mk3 Supra? I think it could be done!
 

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Those engines are great. I really wanted to swap one in the past, but there wasn't a lot of good/cheap ECUs available at the time to tune VVTi. I wish the forum at Toyota 1UZ-FE & 2UZ-FE V8 Technical and Performance Forums was still up, had a wealth of information on the Toyota V8 platform. It's really too bad that Toyota always paired their V8s with an automatic. The engines really shine with simple bolt-ons and a manual gear box. Never understood why the SC400 guys always pluck them out for a JZ. Slap a R154 on it and a TRD supercharger and open up the exhaust, done.
 

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OP, sounds like you are about to embark on a project car to get you to your high paying job. I would advise against it because I have a 120 mile a day commute myself and would love to drive my Supra to work everyday, it just isn't practical even if it was fuel efficient.

Some other questions to ask:

Do you have a family? If so, will you need to pick them up/drop them off without getting back to the house first? If no, will you have a family in the future? Planning ahead will work wonders here and save you thousands of money and time in the future.
Do you occasionally go to lunch with co-workers and vendors?
Will you need to drive your car to other sites other than your primary work location?
At some point will you need to have cargo space?

Ask yourselves these questions and maybe your answer may come to you easier. Good luck with your decision.
 

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Just a couple of observations....
Never seen a late '80s to early '90s Toyota run A/F at stoich at highway speeds, just steady state.
they all seem to be around 16-18 to one at light throttle. Only when accelerating, or pulling up a hill did they richen to the 14-15 range.

American V8s don't give good mileage with the rear end ratios readily available for the MkIII diff.

And last but not least, I run a 4.56 rear end gear behind an all motor 7MGE, and can knock down 22 mph on the highway. But around town hunting mustangs, I can see the needle on the gas gauge fall.
Small price to pay for humiliating V8 owners...
:)
 

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Interesing premise for a swap - and a Mk3 would make an outstanding highway cruiser or long-distance daily commuter, the only bummer really is the gas mileage.

Personally, I'd be looking at a VVTi 1JZ-GTE swap and leaving it pretty much stock aside from intake/intercooler/exhaust mods, with an R154 5-spd and a 3.58 or 3.73 rear end.
The VVTi 1UZ would also be a good option, and one that could be done relatively elegantly with its factory auto trans and full accessories - I'd also opt for a taller 3.58 or 3.73 rear end.

Wildcard heresy option: Honda K24 with a CD009. With basic breathing mods even NA easily makes more HP and TQ than a stock or near-stock 7M-GE. The CD009's gearing would match well with a 3.73 or 3.91 final drive for the Honda's RPM range. I'd bet that with the right gearing combo that 32-35mpg could be achieved in NA form. Similarly, a small turbo like a GT28RS would be pretty easy and could be done on the stock engine with some Kpro tuning, and make mid 300's no sweat, and still get fantastic mileage. Hell I bet you could even tune it to run decently well at ~5-7psi of boost on 86 octane and still make mid 200's which would be more than enough to keep up with highway traffic.

Only issues would be sorting out the oil pan and subframe clearance, and ideally, mounting the engine as far back as possible. That would be good for weight distro and the K24 itself would be pretty decent weight reduction. The CD009's shifter housing would likely sit too far back for a MK3 tunnel, so you'd need something like the GK Tech shifter tripod set for it that moves the shifter forward. Only real issues beyond that are making gauges happy and functional and figuring out how to make an electric VSS signal run the MK3's speedometer. That's also an issue with the VVTi 1UZ swap, though.
If one were willing to go full custom on a K24 adapter, a K24+W58 trans would solve that problem and drive & shift nicely. Paired with some 3.73's and a small ~300whp turbo setup and it'd eat up the highway miles no sweat. Lightweight 16 or 17in wheels that are relatively narrow, 7.5 or 8in wide with decent A/S sports tires.

Yeah, not a bad idea for a highway cruiser!
 

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Discussion Starter #39
Thanks for all the responses. To provide a little more background, my avatar picture (the only one I can find of me in my MkIII) was taken in 2008 when my family was only four people. I sold the car when child #3 was born later that year. The child in the car seat is now 16 and her older brother is about to go to college so we will have only four in the family again. We also own a minivan and a medium SUV so this car is SOLELY about me having a car I like to drive 110 miles a day for a rewarding, well paying job. I could probably afford a brand new MK V but it lacks the two things I want: targa roof and manual transmission. If I was given a Mk V I would sell it for a targa IV SE with a standard. My problem is I want a car configuration that nobody builds anymore.

Regarding cost, I thought that since the 1JZ was available in the MkIII in Japan that this should be an easy swap. The point made by one poster is correct; at $1.97 this morning for gas it doesn't make sense to put $5K in to a car to get 3 MPG better mileage. If, otoh, it is an easy swap to put a much lower mileage engine into a nearly 30 year old car then it makes sense.

I also know that on occasion Mk III's without a working engine are available. If I have to put in an engine anyway why not get one that is more efficient.
 

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1UZ vvti info... The engines really shine with simple bolt-ons and a manual gear box. Never understood why the SC400 guys always pluck them out for a JZ. Slap a R154 on it and a TRD supercharger and open up the exhaust, done.
It honestly wouldn't surprise me to find an SC in the garage someday. I don't think they're the most gorgeous car out there, at least in stock form, but I drive a Miata daily, so... opinions being subjective and all... For me, it's the chassis underneath them that is so nice to drive. Plus, they're really comfy!

The lack of the factory manual option, at least in SC form (lucky Soarer owners!!!) is a real bummer. Not that it couldn't be fixed, but UZ adapters are surprisingly pricey. Get what you pay for I suppose, particularly when your options are few.

Interesing premise for a swap - and a Mk3 would make an outstanding highway cruiser or long-distance daily commuter, the only bummer really is the gas mileage.

Wildcard heresy option: Honda K24 with a CD009.

Only real issues beyond that are making gauges happy and functional and figuring out how to make an electric VSS signal run the MK3's speedometer. That's also an issue with the VVTi 1UZ swap, though.

Yeah, not a bad idea for a highway cruiser!
Can confirm, Mk3 makes a fantastic long distance commuter. I used to put on about 350-400 miles a week commuting to a job in / around Phoenix, and drove either the Mk3, or the Miata. Depended on how hot it was gonna be that day, as the Miata had working AC.

As for the Honda idea, if Toyota can put a badass four banger in a Supra race car, why can't we do it to street cars? Though I must say this is perhaps the first time I've ever heard the idea of v-takking a Supra haha. We need to get you out of the desert and into the garage brother, it's doing funny things to your brain. :p

As for the speedometer issue, I seem to recall seeing a Marlin Crawler VSS adapter. Now that I think about it though, that may have been to convert a transmission with a mechanical speedometer output, such as R154 or W58, to an electronic signal, rather than the other way around...

Thanks for all the responses. To provide a little more background... My problem is I want a car configuration that nobody builds anymore.

Regarding cost, I thought that since the 1JZ was available in the MkIII in Japan that this should be an easy swap. The point made by one poster is correct; at $1.97 this morning for gas it doesn't make sense to put $5K in to a car to get 3 MPG better mileage. If, otoh, it is an easy swap to put a much lower mileage engine into a nearly 30 year old car then it makes sense.
Background is certainly helpful, one situation can vary so much from the next. I'm guessing you're looking for a comfortable, two door, four seater?

An SC300 or 400 would be an easy recommendation from me. There were a small handful of SC300's with factory manuals, they came with the W58. Swaps are available commonly enough. Porsche still makes the 911 as well, but I know very little about them. Mustangs are surprisingly nice these days, and seeing 30mpg out of a GT isn't impossible. Their MT82 transmissions can be a weak point if driven hard, fair warning.

If you're set on the Mk3 (I wouldn't blame ya! I drove mine about 25 feet the other day and it was the best part of my weekend haha), then I'd say I agree with Wreckless, 1jz vvti, low numerical gear in the differential. Keep it stock other than the basics, enjoy a fun, nice to drive car with high 20's, low 30's on the highway. :)
 
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