Factory sub tank - sourcing and fitment discussion (1 Viewer)

[grinchy]

and glad to have the options!
I did some tables last night to see what kind of errors there were in several different approximation methods for serial senders, but the path of least resistance is definitely an aftermarket gauge and sender in a ohm rating that is easily supported, like 0-90.

I'm pretty sure KISS is going to win for me, which is (option #2). That is the easiest to wire (no resistors), the easiest to bypass and return to stock if necessary, and gives me what I need most of the time (main fuel tank state), and what I need probably very occasionally (sub fuel tank state) but both (one at time) very accurately.

Only real loss is distance to empty, which will only work on the main tank when the sub it empty, but as that is already wrong due to my tire size, it's not too much of a loss.

There are definitely several paths to success here, depends on what folks want, what the costs and complexity are, etc.

 

[grinchy]

2 of 4 boxes received
Roughly 42 1/2" by 20" by 6".
Part 77001-60831 7700160831

 

[linuxgod]

Only real loss is distance to empty, which will only work on the main tank when the sub it empty, but as that is already wrong due to my tire size, it's not too much of a loss.

Heh cruising range is so inaccurate, especially when towing, that it hardly seems like a loss to me

 

[grinchy]

One open question which required the tank to evaluate was 'what is going on with the two emissions ports'. The answer turns out to be - quite a lot!
The pink/purple port appears to me to be the 'in' and the green the 'out'. There are internal pipes that they both hook to, which look to circle the perimeter of the tank. The pink/purple plumbs in toward the back of the tank, the green toward the front. The internal pipe where they plumb in is at the top of the tank, then it goes down to half tank level for the perimeter run. I assume this pipe is open at the ends . . .

For photo reference, the pink/purple is over that vent pickup

I have a pretty crappy vid I took (my old iphone SE fits thru the fuel out hole), some screen shots below.

 

[brasskey]

I hope this works out. I wasn't 100% happy with the 12.5 LRA in my 2016, but would love extra fuel on my 2018. Thanks for taking the plunge @grinchy. Looking forward to the updates.

 

[rcork]

are you sure those pipes in the tank are for emissions? If this tank were used on a diesel I would think maybe Mr. Toyota was returning warm excess fuel from the engine to the tank to heat the tank. But that's only a WAG on my part.

 

[grinchy]

I hope this works out. I wasn't 100% happy with the 12.5 LRA in my 2016, but would love extra fuel on my 2018. Thanks for taking the plunge @grinchy. Looking forward to the updates.

Well, there are a few variants on the tank plumbing, and in the diesel models the evap canister lines run to something called a fuel cooler. Both the main and sub tanks are used for petrol/gas or diesel, no difference in the tank part numbers.
There is a different fuel siphon on the diesel variant at the sub tank.
I didn't study the diesel versions too much, enough of a rabbit hole over here on the petrol side.

The lines (green and purple) are definitely evap lines. The hoses are called

and the color codes are common to the evap lines on the US model car, for example.

The way I see this flow is main tank evap -> charcoal canister (stock) becomes main tank evap -> pink/purple -> green -> charcoal canister, so putting them in serial.
Another, likely viable option would be to tee them in. Plug pink/purple, hook up main tank evap and Green sub tank to a tee, and hook that to charcoal canister. The routing I suggest first is what they do for the global model with charcoal canister, but that emissions system has a few less parts than the US emissions . . .

Definitely only an educated guess at the moment

 

[unclemat]

Is the subtank metal or plastic? Kinda hard to tell from the pic.

 

[grinchy]

Is the subtank metal or plastic? Kinda hard to tell from the pic.

when I tap it the sound is dampened metal, but the new car features proudly talks about this structure

A magnet sticks to the sub tank stongly . . . so I think main is polymer and sub metal

 

[unclemat]

Huh, so "recyclable material" means metal?

 

[grinchy]

I hope this works out. I wasn't 100% happy with the 12.5 LRA in my 2016, but would love extra fuel on my 2018. Thanks for taking the plunge @grinchy. Looking forward to the updates

Huh, so "recyclable material" means metal?

I haven’t tried to stick a magnet on the main tank, but maybe?

 

[TheIcemanCometh]

Regarding the sender for the aux tank. If a non-NA vehicle where would the wiring go? I am assuming to the instrument cluster in a non-NA vehicle which is smart enough to know about both tanks and combine the data.

 

[grinchy]

Regarding the sender for the aux tank. If a non-NA vehicle where would the wiring go? I am assuming to the instrument cluster in a non-NA vehicle which is smart enough to know about both tanks and combine the data.

The non-US vehicle plugs the sub tank sensor into the dash gauges via a few interconnects, and the dash gauge 'somehow' knows what to do with it.
The US vehicle reuses the same 10 pin connector for the EEC (evap canister), runs it thru a different set of interconnects, and may or may not provide the pin to the dash gauge. The dash gauge is a different model number and has an EEPROM . . .

The senders are the same in main and sub tank, so I plan to just use a simple switch at the front dash (probably under where the tire pressure reset is) to swap it between the main tank (almost always) and the sub tank (once in a blue moon, for just a few min). I will be running a wire up to the front to do this.

 

[grinchy]

Box 3 - the filler
Box 4 - the fuel pump

Are in the house.

All expected parts are in.

I made a mockup of the evap canister and was looking for a good relocation point for it.

1. Due to AHC (which I guess 'could' be moved with significant effort) the right (Passenger) side behind wheel is out. For the US TLC this will work perfectly though.
2. Due to some HVAC (I think) fittings, the left (US Driver) side behind the wheel is out, but it could fit if I separate the canister from the relays and what not that make it 5 inches longer (effort estimate - medium to significant)
3. There may be room behind the gas tank at the tow hitch. It may be 1" below the frame (so a skid will be required). This puts the EEC below the sub tank. I did a bunch of google searching, it wasn't clear if this is a huge no no or a non issue . . . EEC isn't gravity dependent. I guess it's a go with maybe some thought around putting in a 'high' point on the evap hoses. It's not an issue for the manifold or fresh air vent. (effort estimate - low + skid) <- current option
4. Move the EEC to underhood by the radiator on right (US passenger side). Small investment in tubing and fittings. Some fab. (effort estimate - medium) <- 2nd choice

Anyone have an EEC degree and want to share wisdom?

 

[terdrocket]

Or..... Modify brand new sub tank to fit around evap with big f'n hammer? Call it the quarter gallon mod.

 

[unclemat]

Or..... Modify brand new sub tank to fit around evap with big f'n hammer? Call it the quarter gallon mod.

Ahem. The goal was factory like solution. That ain'it...

 

[terdrocket]

Ahem. The goal was factory like solution. That ain'it...

If it was at all possible to reshape the tank, it would beat the madness of having to relocate the evap/charcoal crap. That's what LRA had to do.

 

[grinchy]

If it was at all possible to reshape the tank, it would beat the madness of having to relocate the evap/charcoal crap. That's what LRA had to do.

I considered a custom tank for sure, but without seeing what was going on with the evap etc on the factory tank I was leery of screwing it up, and factory was certainly seductive. But yeah, moving the evap is definitely going to be a thing.

 

[linuxgod]

Does the evap canister vent at all? If so under the hood might be a bad place for it.

Did you change your exhaust pipe to dump out behind the tire instead of straight out the back? If so could you put the canister DS rear where the exhaust normally dumps? Or maybe that's what you were thinking in #3?

 

[TheIcemanCometh]

I considered a custom tank for sure, but without seeing what was going on with the evap etc on the factory tank I was leery of screwing it up, and factory was certainly seductive. But yeah, moving the evap is definitely going to be a thing.

Does this apply only to the LX?? That is if doing the similar on an LC 200 relocating the evaporator would not be needed.