Got a prius, should be interesting to mess with....

[MetroMPG]

I still want to see a pic of this "beater" Prius.

[Blacktree]

Originally Posted by ps2fixer

Anyway, I think my main focus will be the front of the car and main target would be areo and quicker warmup times, seems like the most logical starting point on this car.

I tend to agree. The faster warmup times (a combination of grille block and warmer weather) have improved my fuel economy significantly.

[hayden55]

Yup keep that Prius warm. Grill block is good stuff.

Unfortunately, the gas tank is strange so keep track of quite a few fill-ups before you adjust your scan gauge. Maybe do like 5 fill-ups.

[ps2fixer]

Been meaning to add pics, just been real busy. I mean the most I've modded the car is 50psi tires and a packaging tape lower grill block lol. I paid my mom to clean the car, she said it took her 4 hours, it was that bad. Overall the car isn't in horrible shape, little busted up, few dents, interior was horrible, broken tail light and a touch on the rear spoiler. My mom missed the rear cup holder when she cleaned it, that gives an idea of what the interior was like, really nasty. Guy I bought it from said he couldn't stand to get in the car because it stunk so bad. Oh the driver's window front track seal is missing for some reason, lot of wind noise because of that, need to see if I can modify one from a camry or something to make it work. Besides the cosmetics, the cat seems to be junk (no emissions testing here), and the radio is aftermarket (JVC, at sometime someone cared about the car). The main gauge cluster screen went blank on me once, hasn't acted up since, if it does I'll be "rebuilding" it with new caps. Steering wheel button lights don't work, 12v aux plug doesn't work which I suspect both of those are just a bad fuse. One light inside doesn't work, both tail lights have bulb issues I need to fix so I don't get a fix-it ticket.


Anyway, the car seems to warmup fairly fast, about the time I get to the post office it hits roughly operating temp for the engine (5 miles) so the trip home it does pretty good.

I just ran over to a friends house to help him with something, and it seems like I got into the super highway mode or something, targeted 45mph but held the pedal steady and it dropped to 44-43mph from the up hill and back up to 45-46 down the hill and was seeing 70mpg. I didn't check the state of charge though, might have been burning off excess battery. Car was partily warmed up and hit around 54mpg to his house (few miles past the post office), and on the way back I got around 57mpg according to the scangauge.

Check engine light came back on too, P0420 again, so I guess the cataclean wasn't able to clean the cat enough to save it. It made a difference, that's for sure but driving around low speed and the code came right back. On the highway at 60mph it must have been working well enough to not flag an issue.

I've only filled the car up twice, so I'll have to get used to the funky bladder system. That's why in my fuel logs I've added start and end fuel level % to see if those figures are consistent at all and if the balder effects the fuel level reading as well. I know on the trip it held on the full bar for about 100 miles, then around 150 it dropped down to 8/10. The % from the scan gauge changed a bit while driving like 5% or more fluctuation at steady speed.

Anyway, I need to read more about this super highway mode, like how to trigger it, what it does differently, etc. I suspect if I can get into that mode more often for longer sections of my trips, I'd see a fair increase in overall mpg. I think I have the warm up modes and such understood pretty well. It doesn't seem to require a full stop for the "normal mode" stage, at least for my car, it just is slower to kill the engine till the full stop.

[Blacktree]

I swapped an aftermarket head unit into mine (to get aux and USB inputs). I still have the stock unit, which worked fine. If you want it, you can have it for the cost of shipping.

[ps2fixer]

Originally Posted by Blacktree

I swapped an aftermarket head unit into mine (to get aux and USB inputs). I still have the stock unit, which worked fine. If you want it, you can have it for the cost of shipping.

I did some reading just like 5 mins ago, sounds like the reason my steering wheel lights don't light up is because of the aftermarket radio. One of the wires just needs to be grounded from what I read to get the lights to work. I've had the radio off since I've owned the car because it has a light show going off on the radio, distracting/annoying lol. I might have to take you up on the radio offer though. I did the same thing on my LS400 because the aftermarket radio was killing the battery on me.

The 12v aux connector must be a fuse, or it's disconnected. At least the diag port doesn't share the same power feed since it's working for the scan gauge.

[Blacktree]

There's an adapter you can buy to restore functionality of the steering wheel controls. And I think the head unit has to support steering wheel controls. But you can find it at Crutchfield for about $70.

[ps2fixer]

Oh just had an interesting idea.... The 12v battery was dead on this prius when I got it. It seems to be slow to charge, and fairly quick to discharge, so I'm thinking it might not be too healthy anyway. There are small atv batteries that are lithium ion based with a built in BMS. Of my understanding, the prius doesn't need much for amps for the 12v system to function correctly. I haven't seen any real world numbers.... but I do have a scope that could read it. I just haven't gotten my laptop up and running with the software/drivers yet. I think worst case would be with HVAC on high, headlights on, and brake lights on. Besides the car doing some 12v based stuff with the key off, it doesn't seem to need much capacity or amps. I'd assume 100 amps peak output should be plenty. As long as the car isn't used in accessory mode much, and the interior lights aren't left on, there shouldn't be much of a need for any real capacity. Just put the car in ready mode and draw off the hybrid battery.

Talking about batteries and all of that, it seems like car computers and radios would start using eeproms more for their "memory". Chips exist that have millions of write cycles for their spec, if that's not enough, over size the memory and cycle across all sections similar to how an SSD works under the hood. There really is no reason a car needs 12v power all the time besides the antenna for the key fob and the security to monitor door switches, both features I could live without but I prefer 90's era cars lol.

I don't have an exact figure, but somewhere around 4-5 hours the interior light was left on, it wasn't dead, but the battery voltage was down below 12v, I think it was 11.9v on the scan gauge. Quick search shows they are about 10w, for easy math let's say 1 amp of draw, that's about 5ah battery capacity. Based on a google search, AGM batteries lower limit is 11.6v for fully discharged. Looks like the battery that's in the car is rated at 38ah.

Clearly I need to switch the main interior lights over to LED as well, just to prevent issues drawing the battery low. Looks like they are 1w or less, which means 10+ hours would be 1ah of drain, or to give the same situation above, it would take 40-50 hours for the same draw on the battery. The actual fuel savings for the lower power use is effectively 0mpg, so that's not the root reason to change them out.

Once the battery is fully charged again, I'll have to throw my battery amp tester on it and see what it shows. I think the battery is 450cca rated even though the prius doesn't need anywhere near that much amperage.

Side benefit from the lithium ion battery should be that the charging draw should drop to effectively 0w once fully charged and the charge/discharge efficiency should be much better compared to agm/lead acid. Maybe this is one of the sources of pulling my mpg down a bit. Even at 10 amp charge (120w) I wouldn't think it would make that huge of an effect of mpg. Just sitting with the car in ready mode, the hybrid battery has 400w+ coming off it and the state of charge doesn't seem to get effected by that much at all.

Talking about state of charge, if I take the corner a bit faster onto my dirt road I've lowered the SOC drain on the hybrid battery to about 0.5%. Getting back to the corner purely on electric power takes around 13% at 20mph for roughly a 1/4 mile slightly up hill, that figure came from a rainy day too so muddy road likely didn't help at all.

It didn't seem like too many people talked about the prius's design much when searching around, but it seems like the computer is smart enough to *not* recharge the hybrid battery when the engine is cold. Earlier today when I left, I got the battery down to around 54%. After the initial take off I remember seeing 57% and I kept an eye on it for half a mile or so while it was in cold start yet (under 120F) and I didn't notice it coming up. I wasn't watching it super close though, by the time i got to the post office, I was around 59 or 60 like normal.

For take off, it seems targeting around 2000-2100rpm isn't a bad figure. It seems like it doesn't use much or any energy from the hybrid battery for take off which means all of the energy is from the engine (less round trip efficiency loss). I have to give it quite a lot of throttle at first (little more than enough to kick the engine on in EV mode) and have to let off as the speed increases. I'll have to try some other rpm targets or other ways of measuring take off to see if I can find a better target to go with.

Maybe I'm missing something, but it seems like going around 40mph the excess energy from the engine goes into the battery and it charges it up and eventually does the engine off EV only route. If I go 45mph, it seems to not charge the battery and lower the engine rpm instead. In my mind, I would think keeping the engine at the higher load and pushing the excess energy into the battery, then idling the engine and using electric assist to burn it up would be more efficient, kind of like a pulse and glide but based on engine load, really similar to the under 42mph logic. I suspect that's why at that speed limit there's such a drop in mpg in the prius speed vs mpg chart.

Increasing the mph limit for EV mode to 45mph (ideally 46-47mph) would probably make me see quite a huge mpg gain. I could slow down to 40mph, but I'm trying to not be a thorn in everyone's side.

I wonder what's the difference for the newer prius that can run into the 80mph range in EV mode. I know my car's max hp out in EV mode isn't huge, but it could do 45mph I'm sure, I suspect I could get my current 45mph mpg figures at 55mph if it was able to run in ev mode at those speeds.

Anyway, I have some ideas fumbling around in my head on things, once I catch up on things, I'll have to look into the ideas and see if I can find a net gain on making the engine warm up faster with out going crazy on hacking things up lol.

[ps2fixer]

Originally Posted by Blacktree

There's an adapter you can buy to restore functionality of the steering wheel controls. And I think the head unit has to support steering wheel controls. But you can find it at Crutchfield for about $70.

The radio controls I have zero concern with, everything else functions, just the buttons don't light up when the head lights are on so it's hard to see which button does what at night. Based on what I read, one wire that goes to the radio just needs to be grounded to make the lights work. The stock radio would also be the way to fix it and doesn't require cutting wires.

Looks like there's two versions of the radio, one with a built in amp, the other had an external amp. I'm not sure which one is stock to my car or how to tell the difference. Mine's a base model, so I'd assume the built in amp version, since that's the pattern for LS400.

I tried to find the steering wheel controls in the wire diagrams, I think this is it. Seems to be a resistor logic setup. The lights aren't shown though.



For fun, here's the "body" wiring in this car.



Just to compare, here's the same diagram for a 1997 corolla



Pretty crazy just how much extra electronic gismos are hooked up in the prius and a lot of that wiring isn't hybrid related.

[ps2fixer]

I got thinking and poking around things and came across this thread. Pretty interesting idea/concept. Basically use an EGR "cooler" as a heat exchanger to heat the coolant temp during cold start.... sounds like exactly what I'm effectively trying to do. I was trying to solver the coolant flow side of the issue when you didn't want heat, didn't really dawn on me to stop the exhaust gasses instead. From what I've been seeing, my cat is bad on this car, so either run it as is, or straight pipe it. Deleting it gives room to fab up a heat exchanger and some sort of valve to redirect the exhaust flow.

https://ecomodder.com/forum/showthre...ger-29085.html

I probably should data log some trips to measure warm up times, air temp and such so I have a base line to start with. Full grill block (at least until it warms up more) and engine compartment sealing/insulation I suspect should help tons. The EGR cooler seems like a pretty logical way to go. Clearly a micro controller would be a good idea to have hooked up so it can automate the open/close cycle. I'd say 160F and colder have it heating the engine, and over it's closed.

I suspect a 12v based heater on the oil pan and maybe a 12v heater in the coolant circuit would help things too. The inverter can put out somewhere around 1000w more than standard draws, so probably safe to have 700-800w to heat the engine. Maybe a slight pre-heat if time allows. This is sort of like a plug in block heater, but runs off the stored up energy in the hybrid battery effectively (and in turn, ideally from fuel burnt when the engine is warm and efficient).

It seems like these kinds of mods not many people do, so there's not too much info out there about this stuff. The core concept seems to make sense to me though.

I should probably grab some of those cheap temp gauges that runs off dc power to be able to see some temps under the hood. Inverter, transmission, oil pan, etc.

I haven't looked into it at all, but I'd assume the prius has some sort of coolant to oil heat exchanger setup. At least the 92-96 era toyota camry did, it went right on the oil filter threads and coolant lines ran to it and the oil filter spun onto it.

Oh just ran across this pic, pretty interesting to see the temps charted on a longer trip to compare against. Seems like inverter coolant runs around 115F in their case. I didn't realize the inverter and transmission are on the same loop. I guess a slight side benefit from running in EV mode at first is quicker transmission warmup. Ideally the inverter would be kept to air temp and I'd think letting the transmission warm up a bit more could be good, but I'm not sure what kind of temps the electric motors are seeing.


Source: https://priuschat.com/threads/invert.../#post-2749272

This is also an interesting video I saw referenced.... I guess just dumping excess heat from the exhaust manifold into the coolant can be fine as long as there's enough cooling at the radiator. Benefit is the faster warm up times, just can't heat the coolant too hot to cause issues. A simple copper pipe wrapped around the manifold some, or early in the exhaust pipe should exchange a bit of heat but not be too overkill. Fun part would be doing the wrapping lol. It seems like this head design would be pretty ideal for a hybrid engine.

https://www.youtube.com/watch?v=nNendiDFzSM