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#7: 08-11-2011, 05:52 PM
broknindarkagain's Avatar
Title: ProGun & ProLife. So What
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Location: Phoenix, AZ
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under construction

What is "tuning" your car?
This is a term used for programming the settings in an aftermarket ECU
Do you mean that my stand alone or piggy back isn't plug and play?
Yes, thats what I mean
So how does one tune their ECU?
If you don't know the answer to this already, you should probably go get your car professionally tuned. If you want some basic information on how to do it yourself, I will cover the basics later on in this FAQ.

Professional tuners use one of two methods to tune a car
Dyno Tuning
This is probably the most commonly used method. Basically, the tuner will strap your car to the dyno and give it hell for a few hours while tweaking the ECU settings. Most dyno tunes are targeted towards wide open throttle driving, so normal drivability is sometimes compromised with a dyno tune.
Road Tuning
This is a less common used method, but tends to give you a much more precise tune based on real world conditions. Your tuner will drive your car around on public roads for some time, adjusting ECU settings as needed. This kind of tune will give you a good blend of normal driving and wide open throttle operation.
What are all these horror stories I've heard and youtube videos I've seen of cars blowing up on the dyno about?
Cars blow up on the dyno for several reasons. One reason is part failure.This is always a risk because when your car is on the dyno, it is being pushed to its limits. Another cause of "blow ups" is the tuner. When adjusting the air/fuel ratios, spark advance, duty cycle, etc....things can go drastically wrong.
So what will getting my car tuned do for me?
Ill sum this up as quick and simple as I can.
Your air/fuel ratios are very important. When running lean (too much air), your engine has a tendancy to pre-detonate the fuel. Pre-detonation can cause serious internal engine damage. The most common damage to Subarus from detonation is cracked piston ringlands.
Spark Advance
This is another way to combat detonation. If your fuel is ignited by spark before TDC, you're less likely to get uncontrolled detonation.
Fuel Economy
When tuning a car, this isn't really a major concern since most who do aftermarket engine management are going for as much power as possible. With that being said, a tuned ECU will run MUCH more efficiently then one that is not tuned. It will make more power and use less fuel.
I picked out a tuner and he gave me a list of mods to do before I got my car tuned. Should I listen to him?
Absolutly. Remember, the guy who is tuning your car is likely MUCH more experienced then you are. He probably knows what he is talking about. With that being said, each tuner has their strong points and their downfalls. While one tuner may be a pro at tuning Megasquirt systems, the other tuner down the street might not even know where to begin with one. Its best to provide your tuner with a car that has modifications that he is familiar with. That way he can tune it better, and there is less of a chance of it blowing up on the dyno.
Should I plan for disaster on the dyno?
Hope for the best, but plan for the worst. My first trip to a dyno resulted in a trigger wheel flying off of my crank pulley and destroying a bunch of stuff under the hood. A 3lbs metal wheel spinning at 6000rpms can cause a lot of damage when it brakes off. NEVER put your car on the dyno if you're not prepared to repair what might happen.
How strong are the straps that they use to tie down my car?
Pretty strong.....They are defiantly strong enough to hold your "stationary" 90mph car in place on the dyno. The chances of your car jumping off the dyno are slim to none as long as the tuner keeps his foot off the brake pedal.
Why was I told I need an extra o2 sensor bung?
This is pretty much standard. You need a free spot for an o2 sensor since this is what the dynos computer will measure your air/fuel ratios with
Stoich fuel mixture is 14.7to1...but my tuner told me that I want to get about 11.0to1. Why is that? Isn't that running a little rich?
Stoich fuel mixture doesn't really matter when you're running higher levels of boost. Running a little on the rich side does two things. The extra gasoline in the cylinders helps cool the cylinder walls, and it helps prevent detonation (since you detonate when the engine is lean)
What is the standard hourly rate for tuning?
This varies. I pay $150 an hour for professional dyno tuning.
How can I prepare my car to get tuned?
Make sure everything is in working order on your car before you get it tuned. This includes a fresh oil change, checking all your fluids, tires, etc. The reason is because if your car has to be shut off on the dyno and repaired, you're still paying $150 an hour for dyno time while the repairs are done. Do everything in your power to prevent this from happening.
What about Cobb Accessport? It says I don't need a dyno tune!
True. Cobb AP (and others on the market) will send you a file to flash over to your ECU. These are generic tunes that are close, but not perfect. You will always get a MUCH better tune having a pro tune your car for you.
So if I want to start street tuning my car myself, what do I need to connect to my ECU?
It depends on what ECU you are using. A laptop is a must. I like to use a power inverter so I can plug my laptop in to keep it from dying. On top of that, you need whatever cable / software that is specific to your ECU. This is usally either a USB cable or a Serial cable. Both kinds of cables cna be bought for pretty cheap. The software comes with your ECU, and some venders offer a download of the software on their website
What do I need to learn about before trying to tune my own ECU?
You need to understand how an engine runs. Not just the basics, but the computer operations and how the computer tells the car to delive air/fuel/spark to the engine. This includes air/fuel ratios, duty cycles, spark advance, ignition timing, TPS calibration, fan controls, fuel pump controls, launch control, flat shifting, map, etc. There is A LOT to it
So if I start tuning my own ECU, what will the program look like that I'll be working with?
It depends on what ECU you are using. Here is a picture of the Megasquirt software
Can I tune my car to run nitrous?
Yes you can. A stand alone ECU is a MUST if you want to do this.
Someone told me that I can set up traction control by tuning my ECU. Is this true?
Yes it is. Even if your car doesn't have traction control stock.
I got my car tuned, but I didn't end up with as much boost as I wanted. What can I do to get more boost?
Running E85 is probably the most popular thing done to acheave more boost. However, this requires its own tune.

DISCLAIMER : Tuning an ECU is a very dangerous thing to do. If you plug in one wrong setting, it can cost you your engine. If you decide to try and tune your ECU yourself, be VERY careful.

Last edited by broknindarkagain; 08-21-2012 at 11:20 PM..
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