Last time, we introduced you to a budget-friendly project that includes a rough, four-door ’70 Nova and a junkyard 4.8-liter LS engine with a turbocharger. Kyle Shadden spent many nights and weekends building this homegrown hot rod, and he upped the game when he fabricated a turbo system using a single 88mm turbocharger. There were many ways to wire the electronics for his build but he wanted something that would allow his car to be friendly on the street and a terror at the track. After researching his options, the Holley HP EFI ECU & Harness kit (PN 550-602N) offered the right amount of benefits without killing his budget.
Installing the system was straightforward, with clearly labeled wires and connectors. Kyle found that using the Holley software was just as easy, as he fired up his laptop and started working on getting his boosted LS engine running for the first time. Holley offers base tunes that allow you to get into the ballpark of your vehicle’s parameters, which was perfect for running the car for the first time and putting a few miles on it. He loaded the base tune into the Holley HP ECU using his laptop and the car was ready to run. The car cranked up and ran without any issues, and Kyle brought it up to temperature to make sure there were no leaks and all of the vital signs looked right.
The real test of this combination would take place at Performance Masters, located in Hixson, Tennessee. The Dynojet dynamometer is the perfect tool for tuning this boosted application, and Kyle pulled onto the rollers with high hopes of hearing glorious turbo noise without sweeping chunks of metal off the dyno room floor at the end of the day. For tuning the Holley EFI system Kyle enlisted the help of fellow turbo car friend Scottie Stone, who has a turbocharged LS-swapped Nissan 240SX that makes insane horsepower. Scottie is familiar with the tuning software and knew that Kyle wanted to stay conservative, considering that the Nova is a pump-gas street car. With that in mind, boost levels stayed at 15 psi, with a conservative ignition-timing table and plenty of fuel to make sure it didn’t pre-detonate.
After allowing the Holley system to self-learn the fuel curve and timing, Scottie tweaked the numbers ever so slightly as Kyle piloted the car for numerous dyno pulls. Even after the first pull, everyone in attendance commented on how quickly the car reached max boost, and ultimately max rpm (6,800). The moment the boost came in, the car revved quickly, and told us that there was some major torque converter slippage. As the dyno numbers came in, it confirmed our suspicion, as the numbers seemed a little “low” for a combination of this nature. Despite the torque converter issues, the Dynojet gave us some good news and great data to work with, as the little 4.8-liter LS engine put 562 horsepower to the ground at 6,800 rpm. This is a very conservative tune with 15 psi of boost, 15 degrees of timing at full boost, and a tank full of 92-octane pump gas. Scottie could’ve tuned for max power on race gas, but the converter slippage would’ve been even more significant if we really leaned on the engine.
We are pleased with the car’s performance and it will be a handful on the street, regardless of the converter issues. Holley EFI made a killer combination even cooler, and simplified what could’ve been a nightmare of a wiring project. Even though Kyle’s Nova is a little rough around the edges, it’s ready to hit the street and hurt some feelings at the local dragstrip. A great combination doesn’t always come easy, and it doesn’t always come cheap, but it’s worth all the late nights and dollar signs when the boost comes in and all Kyle can do is hold on tight and hope that it hooks.
Building and tuning a turbo car is more than just setting up the engine and turbo to work in harmony. It also involves the torque converter, transmission, and rearend ratio. Turbo cars work well with a high (numerically low) final gear ratio, as it loads the car harder. However, this heavy load created by the high gear ratio also puts a lot of strain on the torque converter. Turbo cars are especially susceptible to torque converter problems, as you need a good mix of “loose” off the line (stall rpm high enough to start building boost) and “tight” down track (so that the converter isn’t slipping in high gear).
As it turns out, the off-the-shelf Jegs torque converter was not up to the task with this car’s horsepower output. Using data such as the wheel speed, gear ratio, tire height, and engine rpm, we were able to find the car’s torque converter slip percentage using the calculators on www.tciauto.com. Our calculations produced 39.91 percent torque converter slippage, which is about 30 percentage points higher than it should be on this setup. So, just for the fun of it, we multiplied our 562 horsepower figure by 30 percent to see what we’d be looking at with 10 percent converter slippage. The answer is about 730 horsepower at the rear wheels, which is right on target for our boosted pump gas engine.
That means we’re looking at close to a 160-horsepower loss through the torque converter, and that’s not even counting the normal parasitic loss through the transmission and rearend. Just to be clear, it doesn’t mean that Kyle’s torque converter was “bad” or unusable—it simply means that it isn’t built to withstand this application of power. It goes to show you how important the torque converter can be on a turbo car, and how an off-the-shelf converter may not be the answer for a boosted application. Many custom torque converter companies offer specialized torque converters for these applications, and serious racers will often send the converter back to the manufacturer to have it tweaked if the numbers still don’t add up to their liking. We were thankful for having enough data from the dyno and the Holley EFI data logs to see exactly what this combination needs to make peak horsepower, as that will help determine our next steps in making this four-door Nova the ultimate sleeper.
1. The Holley EFI HP system is extremely easy to use. After the software is installed on your computer, simply open it and you’ll see this option screen. Click “Open Global Folder” to get started. You may also pull data from the ECU to view data logs or select a file to open for modification and tuning.
2. With its HP system, Holley provides a number of base tunes to get you in the ballpark. Kyle chose the “330ci 40 PSI Turbo” file as it was close to his cubic inches and was set up for a turbo.
3. When the file loads, you will need to configure the system using your engine’s information. Simple items such as the number of cylinders and displacement (293 CI in this case) are selected.
4. The load sensing option for this build is “Speed Density” and we chose the NTK O2 sensor option as that is the most common O2 sensor for turbocharged builds, and the brand that came with the Holley EFI kit we ordered.
5. More dropdown menus offer options for the fuel-injection system. Since we’re using all Holley components we looked for the part number in the list. We’re using the Holley 522-838 injectors, which flow 83 pounds per hour.
6. As we continue to configure our base tune, we select the ignition type. For this 4.8-liter truck engine, we select the GM LSx 24 tooth option, which refers to the number of teeth on the crankshaft reluctor wheel used to control ignition timing.
7. Although not crucial for the base tune, you can also select your rev limiter type at this time. Kyle chooses “Spark Only” and then set the rev limiter for 7,000 rpm.
8. Kyle used a GM 3-bar MAP sensor (PN 12592525), which is one of the ways the Holley system reads boost pressure. Holley offers its own versions of these sensors, and they are all listed in the dropdown menu. Custom options are also available.
9. The Holley system uses a common 100-psi pressure sensor for boost pressure, fuel pressure, and oil pressure. You can use GM sensors but the Holley sensors make for a simple setup, and even simpler tuning.
10. This is a pretty important step for Holley’s self-learning feature of this tuning software. As long as the “Base Fuel Learn Enabled” box is checked, the Holley system can either be self-tuned by the system or custom-tuned on the dyno.
11. Under the Sensors tab in the upper menu you are able to configure all of the LS engine’s sensors and also configure the gauge parameters and settings on the Holley Digital Dash unit. Here, Kyle sets the coolant temperature sensor configurations.
12. Another important function of the Holley HP system is the number of output options. You can wire in up to four outputs to be controlled by the system, which can then be operated via the Holley Digital Dash. Cooling fan(s), fuel pump(s), and much more can be added to the Holley system. More involved systems, such as the Holley Dominator EFI, have additional output options.
13. Once the base tune is loaded, the car is ready to run and drive. Kyle put a few miles on his fresh setup before strapping it to the dyno for a torture test. He built a cool mount for the Holley Digital Dash, so it will be easy to access and easy to see. It monitors anything and everything that has a sensor, so Kyle is fully informed.
14. Kyle’s Nova is strapped to the Dynojet dynamometer at Performance Masters in Hixson, Tennessee. Holley’s self-learning technology allows Kyle and Scottie to “drive” the car while strapped to the dyno. At this point, the ECU is constantly learning and adjusting the fuel curve.
15. This is a learning table, which is mostly made up of zeros. The zeros indicate no change from the base tune, but you’ll also notice positive changes and negative changes throughout the series of numbers. The Holley system is using all of its sensors to learn what the engine needs.
16. Between dyno pulls, Scottie tweaks the setup and checks the data logs to see exactly what the car is doing under full boost. At this point we notice the torque converter slippage and realize that no matter how aggressive of a tune we throw at this combination, the torque converter will be the limiting factor.
17. This table is the fuel flow rate, measured in pounds per hour. The graph features engine rpm, and manifold absolute pressure (MAP, measured in kPa), which measures manifold vacuum through boost. For dyno pulls, the most important factors are full boost and high rpm flow numbers, and our peak numbers came at 6,800 rpm with around 205 kPa. At peak, our fuel flow numbers were 358 pounds per hour. These numbers are configurable throughout the rpm and boost ranges, and adjustments are easy to make.
18. A few more pulls were made as we continued to tweak the numbers to suit the ethanol-enriched 92-octane gas. At full boost, our air/fuel ratio is 11.7:1, which is very conservative. It’s also important to note that our Aeromotive fuel pressure regulator has a base pressure of 43 pounds, with one pound of fuel pressure added for every pound of boost. That gave us a final fuel pressure of around 58 pounds at full boost.
19. The ignition timing table is once again a large field of numbers, but the most important areas for our testing are the cross section where the boost really comes into play. Our best dyno pull of the day was performed with 15 degrees of timing at 6,800 rpm with 15 psi of boost being swallowed by the tiny 4.8-liter engine.
20. During our dyno testing, the Holley Digital Dash came in handy for monitoring the engine’s performance and vital signs. The displays are fully configurable, and you can easily load different tunes onto the Digital Dash without having to use a laptop. The data log feature also works nicely for street driving and drag racing.
21. The dyno results state that our budget-built 4.8-liter LS engine put down 562.50 horsepower at 6,830 rpm. It’s important to note that power didn’t show any signs of leveling off, but Kyle didn’t want to turn the stock bottom end any higher. Peak torque numbers are only 435.16 lb-ft due to the “loose” torque converter.
22. After torturing the turbo LS engine on the dyno, Kyle tortured the tires with a celebratory burnout. Thanks to an awesome homebuilt turbo setup and the simplicity of the Holley EFI system, Kyle’s Nova is tame on the highway and brutal under boost.