Can someone tell me the difference between the Gen 1 and Gen 2 Prius?

The Gen I is smaller with no hatch-back. It uses an earlier version of the hybrid system. Older Gen I cars may be getting near the end of life for the HV battery, so it's good to be careful. Other than that, I will let the Gen I owners fill you in on the details.

Tom

 

Gen 1 had a less sophisticated braking system, applying regen and friction brakes in parallel, and regen didn't do much below 20mph. Gen 2 separates the friction brakes entirely from the pedal (except in a power-failure situation) and only uses them in emergencies, for faster reaction, and where more braking is required than regen can give. It switches over to complete friction braking when the car starts to simulate creep, below 7mph. It can extract a lot more of the energy from braking.

The Gen 2 car allows the engine to rev slightly higher, for a little more peak power, and has a larger electric motor and generator, for greater torque. The battery is slightly smaller and lighter, and lower voltage, for lower capacity. However, the Prius doesn't really need a lot of battery capacity for most driving - it's normally used as a relatively small buffer. The extra power and torque give it better acceleration.

The cars differ quite a bit in their cold-start emissions control. The Gen 1 has a special chamber in the catalyst, controlled by a valve (that can rust up), which captures high levels of unburnt fuel at startup and burns them off once the car's warmed up. Gen 2 speeds warmup by keeping a thermos of hot coolant which is pumped back into the cold engine (North America Prius only). (The 2010 car will run coolant down to the exhaust, beyond the catalytic converter, to extract waste heat from the exhaust and use that to warm up the engine quicker.)

EPA estimates are 42 City, 41 Highway, 41 Combined for the Gen 1 'Classic' Prius, and 48 City, 45 Highway, 46 Combined for the Gen 2 'Iconic' Prius, using the new testing scheme. The old scheme had:

Gen 1: 52 City, 45 Highway, 48 Combined
Gen 2: 60 City, 51 Highway, 55 Combined

The Gen 1 was a smaller car all-round.

 

Jessica,

Attached below are the individual eBrochures for the 2002-2003 Gen I Prius and the 2004-2009 Gen II Prius. They're a good source for the differences between the two generations and individual model years of the Prius.

Attached Files

Gen I:

02_prius.pdf
03_prius.pdf

Gen II:

04_prius.pdf
05_prius.pdf
06_prius.pdf
07_prius.pdf
08_prius.pdf
09_prius.pdf

 

Another good review of Prius model history:

Toyota Prius Hybrid Car Model History

 

The Gen 1 uses a MG2 which is more like a DC Brushless motor, and does not generate as much dynamicly sourced magnetic field. So, it had to have bigger magnets. The battery has higher resistance interconnects. The combination of the two means the Gen 1 should be torquier off the line, but die much more quickly in accelleration. Torquier off the line may only be to a few mph, due to the other issues. I am guestimating here based on the motor write up Argonne did. The higher heat from the battery interconnects results in the batteries going bad about 1 to 2 % before 125 K miles.

The Gen 2 Prius has a motor which generates much more magnetic field during rotation of the motor (induced field). You can feel a surge or accelleration due to this from 15 to 30 mph. But its proportionately a little slower off the line as the fixed field from the smaller permanent magnets is weaker.

The Gen 1 uses sleeve bearings in the transmission planetary gearing. This causes more wear and a greater chance of transmission failure and the need to replace the transmission fluid often. The Gen 2 uses anti-friction (needle) bearings in the planetary gearing.

 

What state are you in? If you're in California or a CARB state, then you should stick w/the 2nd gen. The 2nd gen (MY 04-09) have a 10 year/150K mile warranty on the HV battery in CARB states.

If you're one in a CARB state, to be on the safe side, I'd make sure the car was bought in a CARB state and only registered there.

See Toyota Extended Warranty Info under "As taken from the 2004 Toyota Prius Owner's Warranty..."