What does Penny want to be when she grows up?

 (Written on 2/19/2022)

As I mentioned previously, I love the look of the Spitfire. The handling and braking are on par for a sports car of this class; no reason to try and change anything about them. However, the Spitfire does not provide the performance that I'm looking for. I gave considerable thought to what my objectives for this project are, and came up with this list:

1.     Do not alter the exterior body of the car.
2.     Do not add significant weight, or significantly redistribute weight in a way that would adversely impact handling.
3.     Significantly decrease the 0-60 and 1/4 mile times of the car.
4.     Improve the reliability of the engine, transmission, and drivetrain.
5.     Make the interior comfortable for drives up to two hours in duration.
6.     In all decisions try to minimize costs.
7.     Don't compromise the car's inherent safety.

The third and fourth objectives greatly complicate the project. The engine used in the Spitfire was designed by Standard Triumph in 1953 as an 800cc engine. Its displacement was increased over the years, eventually reaching 1500cc. The engine has only 3 main bearings, and it's really not strong enough to withstand any large increase in horsepower. Road & Track lists the 0-60 time of a 1980 Triumph Spitfire as 14.3 seconds. This is glacial by today's standards.  A 2020 Honda Fit does 0-60 in 8.6s and a 2021 Toyota Prius in 9.8s. The Fit engine is rated at 130hp, the Prius at 121hp, the late 70s Spitfire somewhere around 68hp. The 14.3 second 0-60 time could certainly be somewhat improved by modifying the stock engine, but I'm looking for a significant improvement.

My first thought was to do an electric conversion. My entire career has been in electronics and computers so this would be right up my alley. Electric motors have high torque at low RPM, providing for excellent acceleration. But the trade space for electric conversions is range, weight, and cost. At this time I could not find an electric conversion solution that didn't either add significant weight, or severely limit the range of the vehicle. The cost of electric conversions at this time is also rather high. So I decided against an electric conversion.

I began to research what engine and drivetrain swaps other people have done to Spitfires. Keep in mind that the Spitfire is a small vehicle which limits your options if you don't want to change the car's looks or handling. For the transmission there is a well established upgrade:  the Ford T9 five speed gearbox. It is one of the only transmissions that readily fits into Spitfire's cramped quarters. In addition to having a fifth gear, it's reportedly quieter and more reliable than the stock Spitfire transmission. The T9 was used in many Ford vehicles sold outside of the United States. They are quite common in Europe, but only one car sold here was equipped with the T9. That car was the Mercury Merkur Xr4ti sold from 1985 - 1989, making them a bit hard to find domestically. Since the T9 can be used with a number of engines, including the original Spitfire engine, I made finding one a priority. I located one at a salvage yard on Long Island, drove there, and purchased it.

Ford T9 five speed gearbox from a low mileage 1988 Mercury Merkur Xr4ti sitting in the trunk of my car. 7/30/2021

The T9 transmission with a heavy duty gearset can handle in excess of 200hp / 200ft-lbs of torque, but from what I've read the Spitfire's differential is not that robust. Multiple people have replaced the Spitfire differential with a Subaru R160 differential. Online claims are that a properly setup R160 will take up to 300ft-lbs of torque. So my plan is to use a Subaru R160 differential. Since they appear to be common, there is no rush in buying one.

The engine is a significantly harder nut to crack. Some people have turned their Spitfires into fire breathing beasts.

A car like Ye Beast (ye-beast.com) is impressive, but this conversion obviously changed the looks and handling. So I'm not doing the V8 thing.

 

Some people have put Mazda rotary engines in Spitfires. The rotary is small enough to fit under the hood, although the installation photos I've found showed a surprising amount of firewall removed to make the entire package fit.

My two concerns with the rotary are that I have no experience working on them, and I've read that they can be rather loud. So, I'm not planning to go the rotary route. 

 

Triumph made a version of the Spitfire with an inline six cylinder engine, aptly named the GT6. There are people who have "upgraded" their Spitfire to a GT6. The GT6 has a bump in the hood to allow the inline six to fit.

I dislike the look of the bumped hood. I do know one person who pushed the engine far enough back so that the hood did not have to be bumped. I'm not sure how much this ate into the cabin space, or what it did to the shifter location. The car looks sharp, and he races it, so he did an excellent job. My biggest concern with this route, however, is using such an old engine.

 

My preference is for a modern, more readily available, cheaper, and hopefully more reliable engine. After much searching, I could not find an engine swap into a Spitfire that I was completely happy with. So I broadened my search and started looking at what engines people were swapping into other small cars. It was on a Mazda Miata forum that I learned of the Mazda KL 2.5L V6 that some people had swapped into their Miatas.

 

The KL V6 is an interesting engine in two regards. I've read that it is the most compact V6 ever manufactured, and it's an aluminum engine, making it the lightest V6 ever produced. In the United States the KL was used in the 1993–1997 Ford Probe, and the 1993 - 2002 Mazda 626. The 1998-2002 version featured solid lifters and cast crankshaft to reduce rotating mass. The stock engine produces around 170hp, but the Miata swappers claim to get 200hp with simple changes. The downside of the KL V6 is that it was designed for, and only ever used as, a transverse mounted engine in front wheel drive cars.

 

Trying to use the engine in a configuration it was not designed for presents a few issues that I'll discuss in future posts. The big headache is that it was never mated to a longitudinal transmission. The Miata folks are fortunate that a simple adapter plate can be fabricated to adapt the Miata gearbox bell-housing to the KL V6 engine. It is a Mazda engine and a Mazda transmission. 

 

I spent time searching the internet for information on the Mazda KL engine. Would it fit in the Spitfire engine bay? Could it be mated to the Ford T9 gearbox? The dimensions looked like it might just fit! I did find the bolt pattern for the rear of the engine online and made a template out of plywood. I then compared the template to the T9 bell-housing.

Can you say, "not even close". So now I knew that if I pursued this swap, the biggest challenge would be mating the Mazda KL V6 engine to the Ford T9 transmission.

 

It's not too difficult to find a several year old online post by someone who boldly states that they are going to do this, or make that. Some of these bold posts have no follow up, so one must assume they didn't succeed. Yoda said "do or do not, there is no try". Well folks, Yoda wasn't real; he was a muppet, so his advice is suspect. I became rather smitten with the KL V6 engine and decided to give it a TRY. It may or may not work. I'm committing as little money as I can to trying to make it work, and I'm not going to do anything to the car that can't be undone. Worst case scenario is that I spend some time and money having fun, learning, and eventually decide to change course.

 

That in mind, I searched for and found an inexpensive running KLG4 V6 engine at a salvage yard. It's from a 2002 Mazda 626 with 125K miles on it. On September 17th 2021 I drove up to Mansfield PA and picked up the engine.

 

Like the Mazda commercials used to say, "Zoom Zoom"!