[GreenHornet]

Looking at the Urba Centurion it gets as high as 128mpg @ 35mph constant speed and as low as 65mpg in the urban traffic environment. The vehicle could do 85mpg at 55mph which is still very good considering no hybrid here in the states can pull that off.

Looking at the numbers to me it is still not really all that practical. I think by hybridizing the basic concept huge gains can be maid both in town and on the freeway. The main fuel loss for any ICE is during the initial starting acceleration. By hybridizing the ICE with the electric motor we can eliminate this disadvantage. The next big fuel loss for any ICE comes in at idle in the urban environment. By hybridizing it we also get rid of this parasitic loss.

The trick is to size and position the components properly for vehicle integration. Many things play into the overall fuel economy. One important factor is gearing the Urba Centurion had a final drive ratio of 3.89 and 4th gear overdrive of 0.84. By swapping gears one can easily increase cruise MPG as well as enhance low end acceleration. The Urba Centurion was limited by the Spitfire Transmission gear selection which was not very wide. However consider a full transmission swap such as a Tremec T5 and presto you have just gave yourself a world of gearing options as well as greater availability. The T5 has an overdrive available at .63 which would have made a good difference with the Urba Centurion. The rear differential of the Spitfires also had a 3.27 gear available. Swap that gear with the .63 overdrive of the T5 and MPG would have been much better even. Not to mention you could also have higher 1st and 2nd drive gears on the T5 for much better acceleration potential despite having a higher final drive ratio.

Look at the VW strategy for there 1L series of cars this is not much different really. VW uses there DSG tranny in there 1L series of cars. Proper gearing can have a big effect on MPG so this has to be chosen wisely.

While I am a big fan of the T5 for the Tigon prototype my thinking is going simple and even lighter than the T5. Despite the T5 being only 75lbs and having a virtually unlimited gearing selection and configuration, I decided to go with a simple CVT arrangement to start. The CVT I decided to go with is only 32lbs and has an acceptable gear spread for in town and freeway speeds. By hybridizing the Tigon you can do away with a gearbox altogether since you have the potential for electric reverse. The CVT can handle up to 60kw of power so more than enough for the Tigon design. 60kw puts us at 80hp which so far I have the Tigon at around 46hp combined. So there is still room there for experimentation such as adding a dual electric motor or turbocharging the diesel. Depending on how it works out or doesn't work out the T5 is an excellent backup choice. It is also a perfect choice for somebody down the road who would like to have the manual despite solid CVT performance. Some people just don't like the CVT and prefer a manual so why not be able to offer both as options. The T5 would also open the door for a Lemans style Tigon as they can routinely be built to withstand 500hp or more.

I would like to see the Tigon obtain a combined 100mpg. I don't know if its attainable but it is a great number to work toward and should keep me thinking hard.