Avalon hybrid. What to mod?
 

So I ended up with a 2013 Toyota Avalon hybrid.

• First things first, I want to install a block heater.
• Trailer hitch is also one of the first things I want to do, and then build a small, aerodynamic trailer to pull with it.
• Radiator flaps and wheel skirts would be a nice addon.
• If possible, in the future I'd like to install a heat tank system like on the Gen II Prii.
• A wild idea of mine would be to increase the battery capacity (like with a secondary lithium ion battery) and make it a plugin. There's a company named Enginer that makes kits for this, but they're not cheap by any means.
• An even wilder idea would be to convert to CNG. I think I'd rather mess with the traction battery first though.

Any other ideas of what could and should be modded on a car like this?

Bigger traction battery would be a great start... could do smooth wheel covers and wheel skirts, you know, the low hanging fruit that OEMs seldom touch... belly pan and diffuser if the car doesn't have one already, maybe a lower air dam...

What kind of mileage are you seeing so far? They do pretty good for how big they are.
Toyota ditched the heat tank with the Gen3 Prius and switched to having the exhaust heat up the coolant for faster warm up. Heat tank seems like a complicated solution that only helps in specific use cases. Your Avalon might have a system in place to decrease warm up time, but I haven't looked into them enough to know. If it doesn't, I would lean more towards something like the Gen3 Prius' system than the Gen2.

Does Enginer still actually make kits? Those kits were alright when they first came out, but they don't make sense with all the PHEVs available now.
Unless you have money to burn, I wouldn't mess with adding battery capacity. I think CNG would make more sense and pay off quicker than messing with the battery.

Are there examples of Avalons that have been converted to plug-ins? In other words, is the Avalon designed to run in an EV only mode as it is? If not, I don't see the point in adding battery capacity. If the EV mode is like the Prius, then you'll be limited to very low power and a top speed of something like 40 MPH.

I thought Enginer went out of business due to poor products?

I'm a big fan of all those brave people on here that take on huge projects and would love to see you go forward on such an endeavor, but I wouldn't do it since the money and effort required wouldn't offset the benefit.

That said, there are plenty of projects I take on that have no payback other than increasing my knowledge of how something works. I intend to test the "virtual alternator delete" idea purely for the experience.

I think Enginer bit the dust a while ago, and Plug-In Supply has scaled back these days, if it's still in business at all. The proliferation of viable factory PHEVs has decimated their market.

Whoops, got that backward--looks like Enginer is still kicking (at least, their website is still up), Plug-In Supply is gone.

Thanks!

I get 41mpg. That's nearly all highway. That's what I got when I drove it back home (1,500 miles) going 75mph with the A/C on the whole time. Today I took it on my usual 150 mile route over the mountains. Again I got exactly 41mpg, even with the steep grades. (At least according to the average MPG meter on the dashboard.)

From what I can tell the engine warms up very quickly, so it must have some sort of exhaust heating system. Still, I'd like to warm it up before driving, especially in the winter. We get clear down to -40°F/-40°C on occasion.

A regular block heater would do. I just need to get ahold of a dealer to find out what part I need since I can't seem to find one anywhere on the internet. Then I'd also have to figure out where it goes.

However, something that can heat the engine without being near a plug would be great. And a heat tank doesn't use energy (except the pump). It would add more weight though. I've also thought of a Webasto or Eberspacher fuel burning heater. But those would likely need a small diesel tank to work. There are a lot of situations where I'll have to leave the car for hours where I can't plug it in during freezing weather, hence why something portable would be nice.

I'm not so concerned about heating the engine for comfort or solely for fuel efficiency. I want to make the engine last as long as possible. And cold starts are what do the most damage.

CNG retrofitting doesn't seem cheap either. And yes, the Enginer kits seem quite steep in price. Basically, if I want to save money I'd have to source my own parts instead of using prefabricated kits. And old Chevy Volt batteries seem to be a better bargain than DOT certified CNG tanks. Plus electricity is easier to "trick" into accepting another electric source. Electricity is electricity. But getting the engine to accept another type of fuel is not as easy.


My Avalon with has an EV mode that quits at 25mph, although I can get it to drive with the engine off at speeds below 47mph.

But that's not entirely the point. If setup right the car could run in a gasoline/electric blended mode for long stretches. So instead of 41mpg I might be able to see 60mpg or better. Of course I'd have to figure in the cost of electricity. But with electricity costing 10 cents per kWh around here (and lots of free charging station including at my place of work) I wouldn't worry about it that much.

Also I do a lot of highway mountain driving. Even if I didn't make it a plugin-hybrid, just having enough battery capacity to absorb my descents would be great.

Enginer seems alive, well, and making outlandish claims: Enginer | Solar Powered Prius Plug-in PHEV Conversion Kit with Lithium-Ion | Hybrid

If better highway mileage is your focus, I’d start by improving aero... I’m sure Toyota left some fruit on the tree... smooth wheel covers and rear wheel skirts would be a great start, could maybe get you to 43-44 highway...

Messing with the battery sounds much easier than a CNG conversion, plus IIRC any alternate fuel system needs to be EPA-certified. That's why aftermarket CNG conversions might not be so popular there as they are in less-regulated markets.

Ya. With CNG the tanks are expensive, take up a lot of room, and need to be changed (according to DOT regulations) every 10 to 15 years. Also to be able to use my home natural gas I'd need a way to compress it to 3,600psi. I've been looking for such a compressor and they are hard to find. Then there's integrating it into the engine control system. I could do a non-certified job and probably get away with it seeing how there's no emissions check where I live. Of course that could change some day.

Making a battery that falls into the same voltage range as the NiMH traction battery shouldn't be that hard. IIRC, NiMH cells range from 1.0V empty to 1.4V full. Three NiMH cells would be identical to a typical Li ion cell, going from 3.0 to 4.2V. The auxiliary battery could be connected in parallel and have some sort of BMS that could disconnect it in some extreme case or when not needed.

The only problem with this idea is that the hybrid system seems to want to keep the traction battery at around 70-80% charged, from what I gather on the dash board. Going up mountains it doesn't let the charge drop below what the dash indicates as around 50%. Driving my Leaf over these same passes I saw the batter SOC increase as much as 10 percent going down these hills. That indicates to me that I'd need to absorb as much as a 2kW of energy going down a typical mountain pass. But if the hybrid system keeps the battery voltage up near 75% SOC, I'd need 8kW of capacity to make it useful. Of course this is all just guessing. I'd need to track actual battery voltage and current before deciding on how an auxiliary battery should be constructed.

Of course it would be even better to have a system like Enginer's that has an inverter between the two batteries. That way you could chose how the energy in the auxiliary battery is to be used.