Big Diesel, MPG increase ideas?

[ps2fixer]

Originally Posted by cRiPpLe_rOoStEr

Surprisingly, some econoboxes which cater to countries where they're often the only car of the household are surprisingly more comfortable than their size may suggest.

Yea, the thing has storage compartments everywhere, it feels more roomy and everything than the corolla. The body style isn't my first pick, but I'm more about function than looks, I just don't like drawing too much attention (boat tails and such). The echo I have has a vin starting with JT, so it's built in japan and came over on a ship. The era of Corolla's I like (96-97) are all or almost all US built with 4T starting VIN. Sadly the echo seems to be a bit lower build quality in some areas (door pins for example), but in other areas it seems better. Like it has rust, but not everything is rust. The Corolla I was driving has rust basically everywhere. It has some rig ups I need to fix, I don't like day time running lights (atleast give me control if I want them on auto or not) so I'll probably be disabling that in time even though it seems to work well, not a battery killer like some other brands.



@serialk11r

That's a lot of info you dropped on me xD. The corolla's I worked with are 4A/7A engines. I do have a corolla with a stick trans in it too with a bad engine. It almost sounds like there's a fair chance the trans wouldn't be too hard to be a backup for the Echo. No clue about spline counts and such, I suspect the mounts are similar or not hard to make something up.

Some looking around suggests the engine is a 1NZ-FE, atleast from one wiki page, when I searched before I had a different engine come up. I didn't check the emissions sticker to validate. Sounds like it should be pretty similar engine pattern for the 4A/7A transmissions then. Reading a bit about the 1NZ-FE, I guess it's based on the 1NZ-FXE which is a lower power output, but high compression mechanically, but valve timing is simulated to 9.5:1 ratio type of engine. I heard those can be very efficient. Wiki claims the peak thermal efficiency is around 37%. Another google search says typical diesels peak at around 42%, so that's quite impressive. It almost makes me want to find one of those engines and do an engine swap lol. ~75hp vs 108hp wouldn't be the end of the world or anything. 25% or so lower power, but say 20% better mpg under the same conditions could be worth it.

Also the 1ZZ/2ZZ engines I've avoided a bit, I've read they don't last as long as the older 4A/7A engines. I got to ride in one once and it seemed to have a nice power increase for it's size. The newer Corolla's with them seem to also be lower quality, the cheaper ones are in generally a lot worse shape than a similar priced older one.




Anyway, I have two gas/fuel suckers, and one that should basically go forever on gas. I guess I have a legit car that matches up to the logic of an ecomodder member again xD.

[cRiPpLe_rOoStEr]

Originally Posted by ps2fixer

The corolla's I worked with are 4A/7A engines. I do have a corolla with a stick trans in it too with a bad engine. It almost sounds like there's a fair chance the trans wouldn't be too hard to be a backup for the Echo. No clue about spline counts and such, I suspect the mounts are similar or not hard to make something up.

Gotta have to check if the bolt pattern is the same between the Japanese ones, which were fitted with the 1NZ-FE, and the Chinese ones which were fitted with some A-series engines.

Reading a bit about the 1NZ-FE, I guess it's based on the 1NZ-FXE which is a lower power output, but high compression mechanically, but valve timing is simulated to 9.5:1 ratio type of engine. I heard those can be very efficient. Wiki claims the peak thermal efficiency is around 37%. Another google search says typical diesels peak at around 42%, so that's quite impressive. It almost makes me want to find one of those engines and do an engine swap lol. ~75hp vs 108hp wouldn't be the end of the world or anything. 25% or so lower power, but say 20% better mpg under the same conditions could be worth it.

Don't forget the 1NZ-FXE was meant for hybrids, and it also had a lower torque output (slightly over 20% lower).

[ps2fixer]

Based on what I read (2+ sources), they said the FE and FXE are the same block, same crank, pistons on the FXE are what gives it the 13:1 mechanical compression ratio, and the heads might be a bit different because of the clearance issues with high compression.

I also read that it should be possible to put the FXE/Prius pistons in my engine to get the 13:1 compression ratio, but then I'd have to run high octane fuel, or propane/CNG. I find that pretty interesting since that seems like a pretty good compression ratios for those fuels for power and mpg.

The Atkinson cycle style design of the engine is why the power output is so much less, in theory it should be something like 15-20% more efficient on fuel. The car is only 2000lbs, so it should need a crazy amount of power to perform fine.

I like to do the math as weight to power ratio, it makes it a little easier to think of in my mind atleast. My 97 Corolla is around 2400 lbs, and is 105hp, which works out to be 22.9lbs per hp. The stock echo engine is 108hp and the car right around 2000lbs, so it works out to be around 18.5lbs per hp. If I rework the math to match the numbers up, the echo would need around an 87hp engine. With 75hp it works out to be 26.7lbs per hp. Might be a bit slow, but probably not as slow as my diesel, it takes me like a mile to get to 55mph unless I spool the turbo up and go over 2k rpm.

[serialk11r]

There's someone who posted here about his 1NZ-FXE swap many years ago, and Frankenstein Motorworks is putting a 2AR-FXE on a 2AR-FE manual trans, so I wouldn't be surprised if the bolt patterns were identical despite coming with different transmissions from the factory.

You can put a 1NZ-FXE in your car without an issue because it has a standard intake-only VVT-i mechanism. Supposedly the 2AR-FXE has no exhaust VVT-i so hooking it up to a normal Camry will make the ECU complain. I question whether it would be worth the improvement however, it's only a ~3% difference in efficiency at high load, and since you're here no doubt you're aware of pulse and glide

[ps2fixer]

Yea I've played with pulse and glide, most of my area doesn't really allow for it, the ground is more or less flat, so no opportunity to off coast down hills. I played around with it in my corolla auto at the time. About best in cruse mpg was something like 55mpg at around 45mph (basically the lowest speed the trans would let me go while lockup + 4th gear). Pulse and glide after a few attempts I got stopped to stopped mpg of around 65-70mpg. That's pulsing to like 45-50mph and gliding to 0mph. I think trying to average something like 40mph it was more like 55-60mpg. Still a large improvement, but the effort involve, traffic, etc I determined it wasn't really for me. With a manual trans and efficient take off and shifting, I suspect the numbers could be much better.

I've kind of ran with drive the vehicle as efficient as I can with more or less minor mods. Pulling up to 44mpg out of my corolla wasn't half bad when it's rated 32mpg highway, but that's with like 3 stops in a ~45 mile trip at around a steady 45mph speed. Pretty ideal for mpg. I have half a front belly pan on it, lower grill block, hood sealed, passenger mirror delete. Driving habits were by far the largest effect, the mirror delete and grill block I'd say are next biggest changers.

I actually was thinking about the mirror deletes, not sure what the legal status would be, but it seems like having a couple small screens and having backup camers on say the front corner of the car facing back would give a pretty nice view of the blind spot and an aright camera angle for backing up (atleast as far as side mirrors go).

That's pretty neat the prius engine should fit in my car, not sure how crazy the ECU would be about an engine swap, and like you say, the mpg difference probably isn't worth the effort, but the echo isn't that common, however the prius seems to be everywhere. Back a while ago I was researching the prius and at that time the results suggested the engine basically only worked in the prius so it's value wasn't great. I think I remember seeing a prius engine for $100 on craigslist around that time lol.

Another thing kind of dawned on me recently too. I kind of already knew it kind of, but it was just what I thought. Basically longer stroke vs bore size is more efficient and gives better mpg. That's effectively a truck engine and lacks big hp numbers but generally has good torque figures. I can't say how great this source is, but it seems to make a lot of sense even though it's in a 2 stroke context.

https://achatespower.com/stroke-to-bore/

Based on that logic, the echo 1.5L 1nz engine sounds to be a pretty good engine for mpg. The bore x stroke is 75×84.7mm (0.885 ratio), the corolla 1.8L (stroked 1.6L) 7a is 81x85.5mm (0.947) and the 1.6L is 81x77mm (1.05). From the limited experience I've had with the 4afe engine, it gets worse mpg and has lower power output. It seems pointless when the 7afe is better all around.

A while back I watched a video where a guy took equipment engines and swapped them into small trucks and such and were claiming some pretty crazy mpg figures, I'm thinking an f150 he claimed like 30-35mpg with the 4 cyl diesel engine. They where small engines, probably 40-60hp. Clearly diesel vs gas is hard to compare for the bore x stroke thing but the same logic should apply.

Makes me wonder what the ideal bore to stroke ratio would be for the best mpg and size the engine's displacement for the power requirements. Yea bigger engines weigh more, but in theory if the engine is the ultimate mpg design and you need 50hp from a 3.0L to have alright drive-ability vs a 1.5L 100hp and it's more fuel efficient, then that could be an interesting research point.

Clearly there's a point of no return, there's a point when the stroke will be too long and give negative effects or physical issues (piston speed, friction points, vibrations, etc), but I figured it's an interesting thought experiment. Too bad there wasn't a solid consistent reproducible test that could be done across engine designs to score their fuel efficiency in some standard way independent of the vehicle it's in.

Also it's kind of ironic that my diesel truck has almost a square bore/stroke design (same number, or 1:1 ratio) but has a low hp rate for it's massive size. 104.4 mm × 106.2 mm (0.98). 215hp and 450 ft-lbs of torque. I really thought it would be a lot longer stroke being diesel since diesel fuel burns so much slower and such.

To compare, here's a Perkins 3 cyl diesel for a tractor: 91 x 127mm (0.717) and 17.4:1 compression ratio. It's 2.5L, 45.5hp and 121.7 ft-lbs of torque. Scaling it up to 7.3L gives 132.9hp and 355 ft-lbs of torque. Generally hp/torque scales up linearly with displacement with the same designed engine, atleast based on my understanding and what I've read.

One more Perkins diesel engine, one that's higher compression ratio (23.3:1). 84x100mm (0.84), 41.6hp, 105.2 ft-lbs, and 2.2L. Scaled up that's 138hp and 3.49 ft-lbs. Pretty interesting, similar numbers even with higher compression.

I checked the toyota's d4d 4 cyl diesel and scaled it up and it's almost double the numbers of my diesel, of course it's also about 10 years newer tech in it too. Kind of funny, around a 4L version of the engine would have similar power to my 7.3L engine and I bet the mpg would be a bit better too.

I know hp/torque isn't really a measurement for mpg effects, but I found the numbers interesting. Seems like for my truck, the best FE mod would be a modern engine swap, and the echo would probably be a 3-4 cyl diesel engine swap lol.

Getting kind of off topic, but I might have to poke around a bit more to compare similar vehicle mpgs with long vs short stroke with similar sized engines and such, ideally from the same company so the engine/ecu is setup somewhat similar. Maybe there's something to using old tractor engines to get really good mpg but with low hp.

[serialk11r]

A smaller bore certainly helps, but if the cylinders are tiny the heat conduction losses are higher anyways. The difference in fuel consumption between a short stroke engine and long stroke engine of the same displacement is pretty miniscule, maybe 2-3%.

If you're willing to run a diesel (aka heavy polluter), a cheaper mod is to just run a bit lean. Ideally, you would advance ignition timing (any tuning is difficult with Toyota ECUs), but a hack would be to raise the compression ratio just a touch.

For example if you went to 1.1 lambda and raised the compression ratio by 4%, it would probably be approximately optimal (operating near the rev limit probably a bad idea though).

[ps2fixer]

The 1.6L Corolla got something like 33mpg while my 1.8L gets ~38 mpg driving it "normal". Different drivers and different cars, but my sister drives the 1.6L one now so should be interesting to see what kind of mpg she can get with it (if she tracks it). Using public sourced data supports my experience too. The engines might be almost identical, but the cam profiles and such make them act so much different. My 1.8L feels like it has power and it feels good in the corolla, the 1.6L feels overly high geared and sluggish.






I suspect there's a little more involved than just heat losses in the combustion short stroke vs long stroke. Just the stroke length difference is effectively changing the "gear ratio" of piston travel vs crank turn. Also the pressure is pressed on the piston for longer, so I'd expect more energy to be turned into movement from the long stroke. My uneducated mind would guess roughly 10% for the 1.6L to 1.8L difference. Maybe make the 1.8L into a 2.0L just by a longer stroke and get another 7% and loose some max rpm.

Another interesting thing that I've noticed is when I travel and get to hilly areas, my mpg goes up a little. I suspect it's simulating pulse and glide a little with the rolling hills.

Also, update on the echo, the gas tank leaks at the seam (1/2 tank or fuller), yay for Michigan rusty vehicles. Also the main support for the rear end on the passenger side is rusted out quite badly. I'll have to weld some plate steel in before winter. If I saw that before I bought parts for the car, I probably wouldn't fix it up and just look for another beater around winter time, but the car's design is simple enough it shouldn't be too hard to fix the rust and I'm not super worried about looks and such (it's under the car anyway).

I know people like photos, so here's some of the little beater. Kind of what you get for $250 in Michigan when the vehicle runs and kinda stops (drums and shoes worn out, no adjuster in it's design). Don't mind the broken concrete, working on getting a base setup for my driveway. Got a person coming over so using the car so they don't go cranking into the drive way too fast. Also, yes I have the rear bumper, plan to put it back on so it doesn't draw attention from the wrong people.





Resonator from a Camry works quite well for a muffler on this little thing. Not too loud, but loud enough to hear it to drive (no tach).



Rust... what rust? Bottom left part of the pic is where the rear suspension attaches to the body.





Yep it has the weight reduction in the trunk too.

Anyway, I knew the car was going to be bad, just wasn't expecting the rust to be quite that bad. Trunk is no big deal, ez to patch up. The main unibody frame rail will be a bit more involved. Clearly the car was never undercoated, once it's fixed up good enough to be safe and everything, I'll be undercoating the body. $20 or so of grease can make that car body last another 3-5 years atleast I'd guess. Solid test to see how well it stops rust since I never undercoated anything before, but the logic of it makes sense.

The only down side to that car is the suspension design, it attaches to the body right where the rust is normally. On the "upgraded" cars (corolla, camry, lexus etc) it has a sub frame and independent suspension so the attachment point is much closer to the center of the car so it can rust out a lot more before the physical integrity of the vehicle is in question.

Not sure if I should start a new thread on the echo, or just mix it in with the diesel truck talk. Not planning too much for crazy mods, just fix rust, and smooth the underside of the car out and remove any plastic catching wind.

[cRiPpLe_rOoStEr]

I have seen worse cases of rust getting fixed, even though some were not done the proper way due to the cost.

[ps2fixer]

I didn't check out the front end till after I took it on a trip, humm it's not suitable for the road lol. The main frame for the engine is rusted out, the suspension attaches to that, and it's already broken. Could buy another, but that + tank + exhaust/bumper work, brakes etc, it's starting to be a money pit. Pretty neat car though, pretty cheap built but not super horrible. Maybe I'll find a 2nd one some time and grab it for the vehicle to get good mpg with.

[cRiPpLe_rOoStEr]

Originally Posted by ps2fixer

The main frame for the engine is rusted out, the suspension attaches to that, and it's already broken. Could buy another, but that + tank + exhaust/bumper work, brakes etc, it's starting to be a money pit.

Sounds like a reasonable motivation to use it as a Guinea pig to improve your skills with, let's say, unorthodox ways of fixing a rust-bucket to keep it running somehow indefinitely