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So whats the new plan?
The plan is to greatly improve on the Centurion design creating the Tigon diesel car. I will achieve this by superior aerodynamics, hybrid design, smaller turbocharged engine, overall weight reduction, improved part sourcing and superior gearing.
The Spitfires and GT6 cars have a solid parts sourcing community where its relatively easy to find stock as well as performance parts. I will be upgrading the parts I do not have and rebuilding and reusing the ones I do have with some exceptions. The wheels as stated in an earlier post will be upgraded to a 15" 10lb Smart wheel over the stock 13" 18lb steel units and the Centurion 13" X 6 wheels that are heavy and negatively contribute to rolling resistance. The front hubs, breaks, and shocks will all be upgraded to reduce weight and add strength and I need them anyways!
The rear end will stay stock all nuts, bolts, washers, shocks, and leaf spring will be replaced. Possible CV joint upgrade as well as lowering block will be used. I will use my stock 3.27 rear differential rather than try to locate the 3.89 diff in the Triumph Spit and GT6 overdrive units. This saves me money and gives me a big advantage with my gearing as you will soon discover.
I will still be using the Yanmar but in variable speed form and will be moving to a manual T5 5 speed transmission. They are cheap solid and easy to source. They are also easy to work on for the DIY guy like me. The are literally hundreds of combinations with this transmission which makes it ideal for a purpose built vehicle such as Tigon. When comparing the Centurion gearing to my proposed Tigon we have major advantages. Firstly we can purpose build our T5 to have better 0-60 acceleration over the 4 speed Centurion do to the lower 1-3 gearing with the T5 tranny. We also have a much taller overdrive which gives us big advantages during freeway cruising situations. The T5 is also lightweight and compact which makes it every bit as ideal as the original GT6/Spit tranny. The T5 is also much more durable and can handle much more torque which will be nice when the hybrid system is installed onto the Tigon.
For comparison the Centurion had the following gear ratios:
1st= 2.65/10.3 2nd= 1.78/6.92 3rd= 1.00/3.89 4th= .80/3.112 FDR = 3.89
Tigon proposed gear ratios:
1st= 3.75/12.26 2nd= 2.19/7.16 3rd= 1.41/4.61 4th= 1.00/3.27
5th= .63/2.06 FDR= 3.27
Again the advantage with the T5 is that these gears can easily be swapped if the need arises and there are tons of combinations and options for the builder as this was not the case for the stock Triumph transmissions used in the Centurion. Also having the fifth gear helps move gears 1-4 closer for better acceleration and in town usage with the smaller displacement Yanmar. The T5 also gives me a much taller final gear ratio of 2.06 which is ideal for freeway cruising and greater top end speed out of Tigon. The Centurions top end speed was only 65mph with its 3,000rpm 17hp 3cylinder Kubota. Tigon will have an estimated stock 2 cylinder 13.4hp diesel only top speed of 85mph and turbocharged will put it over 100mph! So here you can see Tigon doing more with less and will reap the rewards through vastly improved fuel economy compared to the original Spit/GT6 and the Centurion diesel variant.
As far as I know there are 4 different rear differentials that can be used which are:
#1. 3.27 this is stock and easiest to find
#2. 3.63 good option for acceleration and top end speed
#3. 3.89 typically used on the overdrive cars and used in the Centurion
#4. 4.11 typically seen on the track cars
This allows anyone down the road to further explore gearing options. This was one aspect that I did not like in regards to the Goldwing rear swingarm and rear differential. It had a 2.75 rear diff and that was it no other options available. Not to mention it would have made using a manual transmission difficult from a connection stand point. I think giving multiple differential options and simplifying the attachment of the drivetrain is a big improvement. No belts and chains needed just a solid heavy duty mechanical connection that will be more reliable and less maintenance.
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