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.
INSTALL:
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!!
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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.
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.
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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.
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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.
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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.
NOTE:
Knock Sensors and a little extra MPG.
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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!
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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.
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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.
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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
LINKS!!
6 comments:
Awesome write up! Im doing an LQ4 into a Nissan 240sx this helped out a lot!
Thanks!!!! Veryinformative
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.
What were you doing for gauges before going to the digital dash?
I was just using some auto meter gauges.
Incredible post.
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