Holley HP EFI:

During the 2011 season, I had raced my LS1-swapped Miata with a stock ECU from a Camaro and an aftermarket wiring harness. Although competitive, this setup proved challenging. My little car was plagued with driveability issues that, at times, kept it off the street. The main issue was that my tune was locked. Any time I needed to get small issues fixed, I paid to unlock my tune and ate up an hour drive out to the shop. On hot track days, I was unable to change the tune, which made me worry about my motor taking the heat. But that worry has now vanished faster then the rear tires on a 16-year-old's Mustang.


I received Holley's HP EFI system with a new LS1 harness. While intimidating at first (as all wiring jobs are), the install was incredibly simple.  Holley's claim to fame is that the EFI system "self tunes". They say the ECU is preset with settings that allow it to learn your motor for the best horsepower and gas mileage. I decided to test their claims on the LS1 Miata.


After we allowed the HP EFI to tune, the air/fuel ratios are dead on. The Monster Miata produced the same power, but its road manners were much better. With old technology, you needed someone to tune your car. This is fine, except you’re victim to due-process. The tuner would put your car on a Dyno for an hour or two, get the peak HP set and be done. The trouble with this is that there is still a lot of tuning required to get driveability and mid-RPM power to be perfect. Dyno time and tuner's time are both expensive, but the HP EFI ECU removes the need for costly tuning. It's like having a tuner constantly sitting in your car and tuning the base map. 

The biggest unexpected surprise with HP EFI was gas mileage: Before the ECU swap, the Miata averaged 23 mpg; afterward, it was getting 27 mpg! 

Unwilling to ever take "good enough," I looked farther into Holley's preset setups. Armed with only a basic understanding of tuning, I started looking.  Holley's software is seriously easy to use, making it the perfect system for people looking to learn how to tune ( I have never tuned anything before). I found some areas of the preset map where I was able to "lean out" the mixture under cruise conditions. This little switch increased the LS1 Miata’s mileage to 33 mpg!! (See below for how I did this). The other added bonus is that I can change the tune using my Toshiba Mini at the track. On hot track days, I can change settings to prevent burning up pistons and then return the settings to maximize gas mileage for the drive home.                     


What does this mean for the average car nut?

Although this system retails for $1500, it's very inexpensive in the long run. During a swap, the stock ECU, harness, and dyno time shoot into the $2500-$3500 range quickly (Expect to pay more if you're adding boost or nitrous). This is what makes the system a real value for the everyday car guy. 

The Holley HP EFI system tunes your car by itself while you drive down the road. My favorite part is it makes everything a bolt-on. If you don't know what a bolt-on is, ask your dad or grandpa. Or, if your she has an Impala, grandma will know. With the HP EFI, all I need to do is strap that new intake or set of heads on and enjoy. No more waiting for dyno appointments.  Holley's partnership with NOS means that all it takes is just a few clicks to set up for juice!!
while Holley makes harnesses for most V8 applications, other applications  are in the works for 4, 6, and 8 cylinders. It would be worth it to mention that the system just received Coast Guard Approval which means it’s golden for Marine use at this point as well. It's so versatile that there is a turbo Hayabusa running around with a Holley HP EFI.

We had a lot to do after Ls Fest. The new Holley ECU was on top of the list.

Out with the old...

 In with the new!

The install is straightforward. Although the harness looks menacing, it only has about half the connections of a stock harness. That makes it much simpler to install, as only the necessities are used. The Holley ECU tunes using the smaller MAP censor so there is no need to reuse the stock MAF censor. Removing this one sensor shaved 3 lbs. off the front of the Miata, not to mention the ECU and harness are both lighter than the old units. In total, this installation helped the Miata easily shed
almost 15 pounds!!

Holley's fit and finish rate above OEM quality. I am almost ashamed of putting it onto such a dirty motor. But we are changing a lot on the car, and progress is a messy thing.

After everything is plugged in (about 30 min. of labor), the next step is mounting the ECU. The Miata poses a strange obstacle with the battery’s location. Holley insisted that the main power connection be
hooked up directly to the terminals of the battery. In order for the supplied harness to reach, we mounted the ECU in the passenger foot well.


My little secret: I still have a stock Miata battery starting this Monster. Keeping weight down is a must, and hell it works. The big red cable goes to the SCCA-mandatory kill switch, and you can see the Holley-supplied braided line going directly to the battery.  

Setting up the ECU: 

I highly recommend playing around with the software to get familiar with it before you plug it into your ECU. I toyed around with mine while watching “Power Block” on Spike. By the time "Trucks!" was over, I had the system figured out. It's really easy. 

When you download the software, a little icon like this pops up. Double-click it to start. If you don't know what "double-click" is, call my cousin. He works in IT and can help you through the process. He'll also insult you, free of charge.  If you know how to double click but just need the insults, I can take care of that.

For a first-time start-up, open the Global Folder. If you have already synced your ECU, then click Download from ECU. Follow the "Help?" link that Holley provided on how to sync your system with your ECU. 

If you have an LS1, go to Custom Cals > LS1 4L60E - Cable Throttle Body. This will load the base map for any LSx. If you don't have an LS1, there are many options;  just look through until you see something that is close to your ride. Remember this system self-tunes and will adjust to your vehicle.

Make sure before you plug in your ecu you set up your O2 sensor. the choice is Bosch or NGK. having the ecu set up for the wrong one will damage the sensor.   

Next you'll need to activate the self-tune. Click System Parameters > Closed Loop/Learn > Advanced Control > 5. Advanced control is a speed muzzle for the learn control. When you’re first starting off, you'll want the system to react quickly and learn. As time goes by, you'll want to lower this number so the system will use what it already knows. 


After that click over to Learn Parameters > Check Base Fuel Learn Enabled > Base Fuel Learn Gain: 100%. This needs to be turned on to make the system learn the base fuel graph.

Now you can start your car and let it learn. Start off by letting it idle. Then take it for a drive. Give it small amounts of acceleration at different throttle positions. Keep an eye on your air/fuel ratios and
make sure they are within the 15-11 range. Ideally a/f ratios you want to be at 14.7 at a cruise and 12:1 at wide open throttle.

Holley has a good video demonstration of how its system tunes.

Knock Sensors and a little extra MPG.

I've looked high, low and on the Internet for the LS1 knock sensor settings. I've seen a lot of open forum topics with no answers. So I just called Holley and found out: It's 6.0kHz. Ta Da!

I found that when my car was cruising on the highway, it was in the little yellow circle of the target A/F graph. Its target ratio before was 13.0-13.6. I've seen cars cruise at 15:1 before, so I lowered the amount of fuel to 14.7:1.  

The other fuel saving tip is this: Decel Fuel Cutoff. This cuts the fuel when you take your foot off the throttle. When street driving, you don't need fuel flowing all the time. This helped the Miata get 33mpg on the highway. On track days, be sure to turn this off. Allowing the fuel to run while decelerating on track cools the cylinders and helps keep EGT (exhaust gas temp) down. 

Holley HP EFI Features:
  • Works with 4, 6, 8 cylinder engines
  • Unique lb/hr based fueling strategy greatly simplify tuning
  • Advanced idle, closed loop, and enrichment strategies allow for very stable operation
  • ECU is fully potted and can be mounted in the engine compartment or interior
  • Sealed automotive and marine grade connectors
  • Allows for use of common OEM sensors as well as customer sensor calibration input
  • Ignition Plug and Play with GM 24x and 58x LSX engines, GM HEI, Ford TFI, magnetic and hall effect trigger, and other ignition systems. New Plug and Play applications in process. Custom settings can be configured to allow many other applications.
  • 1-5 Bar MAP sensor capability
  • Two channel knock control sensor Inputs for both one or two wire knock sensors
  • Dedicated fuel and oil pressure inputs
  • Controls both stepper and PWM Idle Air Control (IAC) motors
  • Speed density, Alpha-N, or combination fueling strategies
  • 4 Programmable high or low Pulse Width Modulated (PWM) outputs and 4 fully configurable inputs can be configured for use with the following features:
  • 4 Stage nitrous oxide control
  • Integrated Water/Methanol injection control
  • Advanced idle, closed loop, and enrichment strategies
  • Fully featured boost control capability eliminates the need for a separate boost control device
  • User configurable input and output programming
  • Outputs can be programmed as pulse width modulated or switched
  • Unique circuitry allows inputs to be programmed as speed/frequency, 0-5V, 0-20V, thermistor, or switched high or low
  • Configurable for: dual cooling fans, dual fuel pumps, AC inputs, basic TCC lockup, and multiple timing retard inputs and rev limiters
  • Vehicle speed inputs
  • User programmable caution and warning outputs for all sensors


Anonymous said...

Awesome write up! Im doing an LQ4 into a Nissan 240sx this helped out a lot!

Anonymous said...

Thanks!!!! Veryinformative

Unknown said...

Excellent write up. I've been running an LS1 in a jet boat with a carb for a couple of years. Fixin to switch it over to EFI using Holley HP and going turbo. Good to know about the knock sensors. I found this page looking for knock sensor and MAF info. You answered my questions, thanks.

Unknown said...

What were you doing for gauges before going to the digital dash?

Johnny Cichowski "Johnny C". said...

I was just using some auto meter gauges.

Unknown said...

Incredible post.