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changzuki 09-29-2012 08:57 PM

Urba Centurion Update - (Kubota diesel, 100+ MPG in mixed driving - Fall 2012 on)
The Centurion's drivetrain has hopefully been reinstalled for the last time. With roughly 2,000 miles on the last implant, the low average is 107mpg. On several occasions it has hit 124 mpg and that is in mixed driving. Final body and paintwork will have to wait until next year. As a side note, the Centurion was at a college sustainability event this week and there was a Tesla there. To illustrate again how small the Centurion is, the Tesla is larger and almost looks "portly", and the Centurion is lower at the roof. There is no comparison when looking at the rake of each car's windshield. (The students went for the Go-One in droves, the Centurion 2nd and the Tesla 3rd.)

There are youtube videos of the Centurion (one is a few driveby shots).
The link for that one is here: Centurion on the open road - Pt 1-4 - YouTube

Still much to do - over and out!

redneck 09-29-2012 10:26 PM

Cool car...

What transmission and rear end are being used ?

What is the top speed ?

Any build info you could share would be great.

Again, cool car...:thumbup:


changzuki 10-05-2012 10:58 PM

>>What transmission and rear end are being used ?
---Spitfire manual transmission and rear differential.

>>What is the top speed ?
----About 65mph where it hits the governor @3060rpm. The little Kubota is not blatting or smoking at that speed.

>>Any build info you could share would be great.
----Build info mostly follows the original plans offered by 128-mpg Diesel-Powered Sports Car There are several deviations that should yield even better results!

----The last 2 weeks were spent addressing vibrations (engine and drivetrain). Over 9 hours dedicated to drivetrain alignment and ultimately moving the engine ahead a whopping quarter of an inch but it was time well spent. Today everything is very acceptable so I might plan to move onward although winter is coming... :(

~ CrazyJerry

Phantom 10-06-2012 09:31 AM

Nice work I have wanted to create the xr3

GreenHornet 07-27-2013 03:06 PM

Hey Changzuki,

I am currently designing and building a kit car code named TIGON lol :) inspired by the Urba Centurion!

Thanks for sharing your car with all of us....

For TIGON I will be constructing my own body kit with a goal of less than .18 coefficient of drag that will be able to bolt up to any Triumph Spitfire or GT6 chassis! I am also hybridizing a 2 cylinder Yanmar engine for start stop, regen braking, and power boost. There are so many things I am doing differently from the original Centurion plans I decided to give it its own name. I guess I would consider the Urba Centurion a cousin to TIGON of sorts :D The car design has changed a few times as originally it was going to be a reverse trike design. I went back to simplicity for the sake of time and complexity with just utilizing the Spit/GT6 chassis only with relatively no modifications.

This way all Triumph Spit/GT6 owners could make use of the highly aerodynamic body kit if they desired all they would need to do is simply unbolt the heavy steel unit with 10 bolts and use those same bolts to put on my light weight composite body kit!

Anyways the TIGON build thread can be viewed in the Hybrids section of this forum here =

I wonder have you ever done any Cd testing on your Urba Centurion? The original Triumph GT6 is said to have a Cd of .32 and the Spitfire round-tail is .39 and square-tail coming in at .42 :eek:

It would be very interesting to see just how much of an improvement your modified Urba Centurion was able to make on the original Triumph cars.


changzuki 07-27-2013 08:05 PM

Urba Centurion Update - Fall 2013 (1 yr later)
Hi GreenHornet. Sounds like a very interesting build you have going on there and no doubt with all your in-depth research it should be a winner.

I've not done any cd testing on the Centurion. I did a few things a bit different than the original plans called for such as windshield rake, overall height, ground effects, etc..

The original Centurion reported 128mpg@35mph.

Lane Motor Museum reports their Centurion at 45mpg. They must have a dragging brake, deployed parachute or something.

Both cars use the 750cc Kubota triple.

Both cars use a power robbing Spitfire overdrive unit too.

My Centurion has the optional Police Interceptor 850cc Kubota and a straight 4 speed. (The 950cc Kubota may have been reserved exclusively for the station wagon Centurions - citation needed!). For 2 summers now I easily pass 1000 miles on the 10 gallon tank and the only time I drive 35mph is in such posted speed zones. We have no freeways here in my vicinity and the roads are not exactly great, so the top speed of 65mph@3050rpm is perfect. I've even incorporated some styling elements which do nothing for efficiency but are "eye candy". One of the most notable is the Carroll Shelby Scorpion wheels once belonging to the original Centurion.

I've put all work on hold for now with the Centurion mainly because I'm knee-deep in a Tri-Magnum build. For this, I've hashed out similar views as yours regarding a hybrid or pure ev, but lithium isn't quite there yet - at least not the affordable stuff. As a premier lithium battery producer, A123 showed promise but has since gone bankrupt. Unless economies everywhere get better, the only lithium market they can currently support appears to be going to cell phones and the like - not evs...

RQ Riley has updated the Tri-Magnum as a diesel-hybrid dubbed the XR-3. I have my own human/hybrid ev reverse trike dubbed "The Aurora Project" At 110 lbs it does pretty good and has some features most cars don't.

Keep up the good work - I can't wait to see what you end up with! :thumbup:

UltArc 07-27-2013 11:31 PM

Hooked. Subscribed.

GreenHornet 07-28-2013 02:40 AM

Hey Crazy Jerry :)

"Both cars use a power robbing Spitfire overdrive unit too."

Ya this is one of the first things I updated. With much time and thought I settled in on the T5 transmissions they have similar weight, compact, and are all over the place. They can also be easily modified by anyone and inexpensively at that. I will be testing a .63 and a .56 5th gear ratio.

The Triumph rear differential that I have currently is the 3.27 and will utilize it first and see how the acceleration goes! If its adequate I will keep it most likely with the .63 overdrive. If acceleration is sluggish I will bump up to the 3.63 rear diff and test out the .63 and .56.

The diesel I am using is the Yanmar 2 cylinder 3600rpm .57 Liter 13.4hp variable speed unit. The hybrid drive is a 12kw 18lb brushless dc motor and is direct drive mounted straight off the crank shaft where you would normally have the crank pulley! There are no horsepower robbing belts on the diesel engine everything has been electrified such as fan, water pump, fuel pump, alternator, AC etc. The electric water pump control module that controls the radiator fan and pump is set to run a bit warm for added efficiency as I have the electric motor hybrid drive for added boost further increasing total system efficiency! The radiator is actually a 2 row aluminum motorcycle radiator :-) I found the stock Triumph units way to big in fact as well as way to expensive new. The motorcycle unit allows me to relocate lower in the chassis which gives me better flexibility with the composite body work shape up front.

I changed up the wheels also to the Smart fortwo the tire diameter size is 22.4". Mainly to reduce unsprung weight and reduce drag as these wheels are 4.5 X 15" and weigh only 10lbs.

The top speed I have calculated with the tire selection, gearing, and available combined hybrid horsepower is a comfortable 90mph. With the hybrid drive system and crazy tall overdrive option of .57 X 3.27 = 1.86 final drive gear ratio I expect to hit some incredible freeway cruise fuel economy numbers. The only reason why I will be able to get away with this tall of a final drive is because I have the 12kw electric motor torque instantly available from the very get go! Also I have the hybrid control configured to only turn on the diesel after the car reaches 30mph which can be manually adjusted if desired. If the battery/Supercap bank gets to low the diesel will auto kick on as well. The individual will have complete adjustment of the hybrid features for individual needs and desires. Hybrid component upgrades will also be an option if desired. So many possibilities for the individual to customize and tweak for there driving styles and routes for best economy and efficiency.

So I eliminate the 2 largest fuel sucking situations for any ICE car the engine idle time during stop and go traffic and while initially starting to accelerate!

In a nutshell TIGON deviates from Urba Centurion as follows:

With a T5 manual 5 speed that has custom gearing specifically designed for fuel economy, A tiny 2 cylinder diesel that has all efficiency robbing devices eliminated, An electric hybrid drive system which allows start stop, regenerative braking, no idle, and engine shut off during pulse and gliding situations, 10lb 4.5 X 15" alloy wheels with 12lb LRR tires, Lightweight highly aerodynamic composite body shell that can be bolted and applied to any Triumph Spitfire and GT6. I maintain the original starter as a back up in the event of the hybrid integrated starter alternator failure. I am also using a hybrid battery/Supercapacitor bank geared for the urban environment which differs from all other hybrids here in North America which none currently use Supercapacitors at all to try and make better use of regenerative braking kinetic energy. Supercaps are an ecomodder/hypermilers best friend if understood and used to their full potential!

I can't list all the modifications but it is a laundry list I am sparing nothing on this as I want to beat 157mpg and preferably 235mpg at normal freeway cruise speeds around 55-60mph locally. The goal is 1 liter fuel economy such as what you get in the VW XL1. I am trying to stay optimistic but do realize I have a huge mountain to climb here. So in order to have a fighting chance everything has to be truly optimized and tuned for economy which means more cost :eek:

The main issues so far were the initial 3 wheel design platform this ate up a ton of time and money starting out. Next was the hybrid design and finding somebody that would work with the little guy. This was not that easy and has taken a great deal of time also! Lastly the Composite body shell. I figure that in order to have a solid shot of 1 Liter fuel economy I have to get as close as possible to .14 Cd and absolutely no higher than .18. So I think this will take the most time as it is absolutely critical and if done right will be the ultimate game changer in this project. Luckily I have a friend locally that is a master composite tech to help me out on this monumental task ahead of me.

Right now I am just shelling out dinero getting all the nuts and bolts together as the mechanical design and modification lists are complete. I am also working on the 2D body design sketches. I have changed them a great deal for the better from my initial posts in my build thread. Once I have the rolling chassis completely finished up I will look locally for a CAD designer who can take the body shell to the 3D level as at this point I do not have the time to try and learn a 3D design engine! Once I have a good solid working 3D model and tested I will begin the composite work!

Anyways gotta get to bed nice talking with you Crazy Jerry I will catch up with you later. :thumbup:


GreenHornet 07-28-2013 02:44 AM

Nice Pics BTW I love the changes you made to the original Urba Centurion it really makes yours look pretty bada** :-)

Ang84Indy 07-28-2013 03:40 AM

Hey changzuki, your Centurian looks great! I've been a fan of both the Centurian and the Tri-Magnum since I was a teenager (back when they were first featured in the old Mechanicx Illustrated magazine). Do you plan on making a build thread for the Tri-Magnum?

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