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It was TPC Racing’s metallic Forest Green C4 development car that garnered media attention internationally for its turbo system circa 1995. The car boasted 8 lbs of boost, 450 HP, a top speed of 177 mph, and a 12.2 sec quarter mile time. It received rave reviews in magazines such as Street Power and Turbo & Hi-Tech Performance for its performance and smooth, proportionate power delivery. However, determining the reliability of an aftermarket turbo can be difficult in its early stages of life, which is why we present to you the following Guards Red 964 C4:
If the Forest Green C4 development car was the first of its kind that TPC Racing turbocharged, this Guards Red C4 was the second; the first customer car fitted with the C4 turbo conversion kit. It also features our TPC Racing methanol injection kit, providing a generous increase in horsepower while serving as a additional cooling option. What makes this even more special? After 20+ years of successfully tracking and daily driving with the original TPC turbo kit, this 964 C4 has finally returned to TPC Racing for an upgraded, modernized system.
Stay tuned as we continue to post updates on the progress of this project.
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Returning to the shop, the customer’s Guards Red C4 wasn’t fitted with all the TPC products that the Forest Green development car was. We don’t have any dyno charts from before or after the turbo installation in ’95, but we threw it on the dyno upon its arrival. The car put out an impressive 291 HP to the wheel, which is a significant margin over the stock claims of 247 crank HP (assuming a 15% loss in power to the wheels, we can estimate about 210 WHP). And remember that this car has been running on the same turbo kit for over 20 years!
Before we could get to the fun, modernized upgrades it’s important to note that a lot of the work that goes into upgrading a system like this includes basic service and maintenance of the many parts of the car, including both factory and aftermarket. We’re not going to delve into this, because it’s really a topic for another discussion.
For upgrades, we kept it fairly simple yet effective. We replaced the old turbo with a modern, ball bearing turbo, an option available in our Cayman kits. In case you’re not already familiar with its advantage, the primary benefit of a ball bearing turbo over a traditional turbo is its vastly quicker response rate, resulting in reduced turbo “lag.” From there, we replaced the old waste gate with a brand new Tial wastegate. That’s it; some service work and an upgraded, modernized wastegate and turbo and the car was ready for the dyno!
How many kilometers did the car drive?
Shouldn't it matter more than the amount of years?
Thank you
The car originally came in with about 15k mi. on it. It now has a little over 65k mi. on it. So the turbo kit has seen about 50k mi. or a little over 80k km. It's seen nearly 50 track days in that time as well.
Originally Posted by pilotjosh
TPC,
Did you (or do you) make a turbo conversion kit? I've always thought you only had the supercharger option for sale...
We originally started with turbo conversions for these cars. However, at the time it also required an engine rebuild, so the project took quite a bit of money and time to complete.
When we introduced the supercharger kit it became very popular for its reduced cost and turnaround time. At this point, the only people really purchasing turbo kits had the intention of a race car build. For this we would convert 964/993 RS into GT2 builds.
We can still offer both the supercharger and the turbo as a custom build!
Originally Posted by Vandit
The car is still on Motronic w/ the 20yo piggyback to tune for the turbo? No upgrades/development in that area?
Yes, we still tune the car on Motronic with the old piggyback tune. We still use this, because it has continued to work great over the years, and it still allows us to make changes to the tune - the one for this turbo upgrade has been the first change in tuning since the first installation.
In the past we have used Motec for race cars, and we would probably use this for any completely new builds today.
The dyno results are in, and we are very pleased with the results! The car is now putting out 400.00 lbs/ft torque and just shy of 400 Hp to the wheel! This is nearly a 200% increase in power from stock.
We're very excited to return this car to the customer and hear about his experiences both on and off the track.
The dyno results are in, and we are very pleased with the results! The car is now putting out 400.00 lbs/ft torque and just shy of 400 Hp to the wheel! This is nearly a 200% increase in power from stock.
We're very excited to return this car to the customer and hear about his experiences both on and off the track.
Hats off to you guys for building such a powerful AND reliable system.
Turbo or Supercharger - since you do both - which is better for what and what are the driving dynamics of each? How do you work with a customer to decide? It's great to see manufactures continue to develop products for these great cars.
Also, great job over in 997 GT3 land too. The DSC system sounds awesome... maybe one day we'll see something like that on a 964...
08-13-2015, 12:19 PM
Updating a 20+ Year Old 964 C4 Turbo Kit
