Speaking of hybrids, did anyone see the Hyundai HyperIonic at SEMA this year? Bisimoto who usually tunes high performance cars took a Hyundai Ionic, tuned the ECU, changed the body a bit and added 19x7.5 carbon fiber wheels by Carbon Revolution. The car supposedly gets 80mpg on the highway. The carbon fiber wheels are about $4,500 each and the titanium lug nuts / bolts are about $50 each. I always wondered why people are not into modifying their hybrids for better mpg and bragging rights.

There is also a guy on YouTube (can't remember his name) that put lithium ion batteries into a first generation Honda Insight and he was getting 150mpg on the highway. I think he got the used batteries from a Nissan Leaf and then made an electrical box that could communicate with the Honda system. Very cool stuff.

I like the idea of using the ICE as a range extender instead of being connected to the wheels. Basically just a generator charging the batteries. As a boy, back in 1964, I drew up plans and sketches for just such a set up. I keep telling my wife this and she keeps telling me I should have patented it! The new London Black Cabs use just such a design:
https://www.youtube.com/watch?v=qOxnJQP2_0E
Very interesting video.

You rarely see modified hybrids because, unless you travel to a major city, the majority of buyers are aged 55+ and are usually penny pinchers. Don't think I've seen anyone younger than that in a Prius. And don't forget, most hybrids have auto gearboxes, driving enthusiasts or people likely to modify a car simply wouldn't drive a car with no gearstick, and who can blame them. I'm pleased some manufacturers are offering hybrids now with manual gearboxes ONLY, all of Suzukis mild hybrids are manual only, at least in the UK.

I'm sceptical about range extenders, it just means you're more likely to use it that find a charge point, your clean electric vehicle is still relying on 100% fossil fuel to get its energy. I'd rather go full EV and avoid fossils if I could.

The London Cab is a full EV, but with a range extender for longer trips. No one would buy a Range Extender EV then run it on petrol, when they can charge it from the mains, for next to nothing. The problem with most EVs, just now, is they have the range for over 90% of journeys, but occasionally fall short. The Range Extender option covers that. Once batteries technology improves, as forecast, then Range Extenders will no longer be necessary. Why anyone buys a Hybrid, other than a PHEV, is completely beyond me.

Wayne Gerdes has gotten over 180mpg out of a stock Insight with manual in hypermiling competitions. Check Ecomodder, and maybe Cleanmpg, if you want to see modifying for a hybrid. Though the most successful hybrids are Toyotas, and most people buying that brand just want a reliable appliance car.

For the original Insight, one person installed a turbo from an old Sprint. Another took out the muffler to put on a drop down fifth wheel driven by an electric motor for steady speed coasting. Several has installed a MIMA; it's a manual override of the amount of electric assist.

For the gen two Prius, people were using grill blocks and removing the air box snorkel in order to suck in warmer engine bay air. Many also used block heaters year round to shorten the system's warm up cycle.

It is the KISS way of doing it as opposed to how the Volt works. The issue with series hybrids is that the energy conversion losses will mean an efficiency loss, specially at higher speeds. Which makes it better to use it on a longish range plug in as opposed to something like the Prius PHEV.

You can already get the i3 REx which has such a range extender. Then GM had plans for series hybrid(can't recall if it had a plug or not) that used a Sterling engine back in the '60s. Audi had a small fleet of A1 E-tron PHEVs that used a 250cc rotary as a series range extender back before the 2008 recession.

Nissan is selling a non-plug hybrid in Japan that is just the Leaf drive train with an ICE range extender. it is selling well there, but Japan's speeds are lower than in the US.

Every time I go on Ecomodder my computer crashes because of viruses on that website. This happens when I use different computers as well.

I watch F1, so I guess you could say that's where you can actually see hybrids getting modified all the time for better power and fuel economy. Nowadays the cars make a combined power of 1,100hp during the race and around 1,300hp during qualifying. About 200hp comes from the battery. The engines are also restricted, they can only use 3 engines for the whole year, which means the engines now are covering around 2,600kms. A 24h LeMans prototype usually covers a distance of 5,000kms during the 24 hour race. There was a BMW F1 car about 20-30 years ago that made the most power (about 1,450hp); but that was made to only last the qualifying session, about 30kms.

The fact is that most buying a hybrid are doing so for the efficiency. While they might do small mods like grill blocks, there isn't much one can do to improve the efficiency of the car without the gains not being worth the cost of the mod, or messing with emissions, which many hybrid owners care about.