Engine Tuning

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  • Regular price $649.00


STR has had its Handheld ECU Tuner available for a while now, and chances are you have some idea about what the ECU on your vehicle is and what tuning your ECU does. However, the true complexity of what is happening in your ECU before and after a tune may have eluded you.

Like most, you're probably just happy knowing that you've got more horsepower and a higher top speed. If you want to know more about what they do and how we tweak them to get the very best performance (we won't tell you everything. We've got to keep some secrets, right?), feel free to read on and enlighten yourself.

We have spent thousands of hours developing our ECU tunes for the last few years and have learned a lot through that period. Our ECU tuning team is made up of several guys that come from different backgrounds and bring very different and necessary skills to the table.

We have electronic experts, clutch experts, engine experts, and programing experts who have all come together under STR to develop these custom tunes. Keep in mind that altogether they have decades and decades of experience that they have all funneled into a single project. This is not a simple topic and this explanation will not be comprehensive, but it should prove interesting.

What does an ECU do?

ECU stands for "Electronic Control Unit," which is a fancy name for a little computer that does everything on your vehicle. Before we even touch it with a tune, the ECU is doing a lot of complicated stuff.

ECU out of its case showing the motherboard
This is what your ECU looks like after we take it out of the machine and out of its case. This is your UTV's brain.

When I say it does everything I really mean everything. It controls the exact moment your spark plugs fire every single time they fire, it controls exactly how much fuel enters the cylinders every single time a piston actuates, and it interprets the pressure you apply on the gas pedal and injects fuel accordingly (when you press the gas pedal you're not giving gas, you're requesting torque.

It also places artificial limits on the maximum speed and RPM. It keeps you from driving your vehicle without your seatbelts on and will cut the throttle if you press the brake and accelerator at the same time on some vehicles.

You are not really driving your vehicle so much as making suggestions to the ECU, and it decides what to do from there.

Getting Under the Hood

The first step is to figure out which knobs to turn in the ECU.  After that, it's all educated guesses and trial and error.

In order to turn knobs, we have to figure out where these knobs are and what they do. These aren't actual physical knobs of course; they're lines of program code in the ECU.

So first we find the knobs on the ECU by hooking it up to some pretty complicated computer software. At times, this search involves looking through individual lines of code by hand until they see a line that looks like spark plug timing or a rev limiter.

Apart from the lines of code that control limiters, there are 3 main knobs they look for that control spark, air, and fuel. Finding these can be incredibly difficult and time consuming.

Finding it

"We're poking around in the dark all day and then we find it!" says the ECU engineer the moment he hears a machine rev above its limit on the dyno. A quick scan of the dyno readout confirms that they've got it - the rev limit has been raised from its admirable but cramped ECU limited RPM up to an RPM that will make your hackles stand on end and get your heart thumping. It's a real eureka moment every time it happens. A testament to just how complicated the process can be.

Once those knobs are found, some things come easy. Raising the rev limiter or the speed limiter is a no-brainer. Changing the behavior of the gas pedal so that it feels better and more consistant isn't too difficult either.

These changes make a huge difference on most vehicles where you only get a fraction of your performance from the factory. Then we move on to optimizing for higher octane fuel to squeeze out more horsepower and torque, which is a whole other thing.

Trial and Error

That's where the trial and error comes in. Our engineers will tweak spark timing, air intake, and fuel injection. Thanks to their years of experience, they have some idea of what changing a spark firing angle by a few degrees will do, but they don't know exactly.

After tweaking, they load their saved program to the stock ECU (in a process called "flashing"), install that ECU back on the vehicle it came from, and give that vehicle a pull on the dyno.

After analyzing and interpreting the torque and horsepower data the dyno gives them, they take the ECU back out, bring it back to the lab and turn the knobs some more.

Rinse and repeat ad nauseam until peak power or torque is achieved. Then we do it again for high octane fuel. Then for the next model. Then the next model year. You see? It's a lot of work. We then save copies of the specific tunes we made so that we can make more copies and sell them.

But we're not done yet.

Your clutch is slowing you down

That's right - when it comes to cutting your vehicle loose, your OEM clutch isn't the clutch for the job. You can tune and optimize your engine as much as you want and it will look great when you measure the horsepower at the crankshaft. If you don't make it work with the clutch on the machine, that power will never reach the ground.

That's why our job isn't done until we've maximized power for the stock machine and designed the perfect clutch kit to get that power to the ground.

How do you build the perfect clutch kit?

You guessed it - trial and error!

The process of building a new clutch kit involves swapping out primary and secondary clutch springs and adjusting weights on the clutch arms themselves. If you've ever bought one of our clutch kits, you'll know we send them pre-weighted so you don't have to do any guesswork.

By putting different weights on different points on the arms, our engineers change the torque and horsepower that reaches the ground.

Altogether there are approximately 36,000 different combinations of weights that can be installed on each clutch arm. Each half gram and each position makes a difference. Combine that with all the different primary and secondary clutch springs that can be installed and you have hundreds of thousands of potential configurations for your clutch.

Take it to the Dyno

Luckily our guys know how to narrow that down to just a few possible candidates. First, they test a stock machine on the dyno so that they know what they're comparing their changes against. Then they make tweaks and test it again on the dyno.

Clutch + Tune = Joy

The clutch kits and ECU tunes are often designed in parallel with the same engineers working on both aspects. That way we can be sure our tunes and clutch kits work perfectly with each other and deliver the pure adrenaline that you feel when floor it.

Trust us, that's the goal - pure joy. It's an easy thing to measure your success by, too - either you're blown away that you've got this much power in a machine that you thought didn't have any new tricks, or you're not.

Experience it Yourself

We know you can tell the difference too. We expect each and every person that upgrades their machine with our tunes and clutch kits to feel like they have a brand new machine.

These kits are extremely difficult to make and to make them right, but we thankfully we've got them figured out to provide maximum horsepower, maximum torque, maximum speed, maximum drivability, and, of course, maximum fun.

Each Tune is Vehicle Specific to give you the maximum benefits. Please contact us directly to get the Specific tune made for your machine.