Piston Slap: ECU Tuning 101. Ish.

TTAC Commentator pleiter writes:

Convince me one way or another, about OBD-II. I want to know if I should invest in it for personal use. I need to know things like what are the major options, is it just pigtails and a PC laptop interface, now, does it work very well with one publication or not (Chilton’s, Haynes), will I still have the risk of purchasing wrong electronic parts that are not returnable.

Also, is there any emerging market for economy chips or economy (mpg) reflash? I know cold camshaft profiles are starting to show up, but I’m looking for something easier to implement and reversible, because I’m lazy.

I have a Scion tC and two 325i’s.

Sajeev answers:

I come across questions like these on car forums all too frequently. Whenever it happens, forum veterans usually reply with, “what are you trying to do?” That isn’t a dickish comment, because people want other people to be an informed consumer of high performance automobile parts. So let’s do this thing.

Know that any OBD tuning goes far beyond the scope of Chilton or Haynes manual. But even the factory books won’t help you in the computer-tuning department.

Next? OBD-II. Aside from two extra oxygen sensors and some Big Brother monitoring abilities, it is a great system. OBD-II is very tunable, provided there’s a good software hack for your car. Most Detroit Iron uses plug-and-download OBD modules and many German/Italian rides require a little down time to remove the computer, mail it off and wait for “reflashed” processor: the result is more power and torque, with little to no penalty in fuel economy. I am having a tough time finding an easy tuning solution for Toyota products, which is quite odd considering their popularity relative to Detroit brands.

But here’s the dirty little secret: your results may vary. And I am less than optimistic about the improvement you will see (more importantly feel) on either of your cars. It may not be worth the hundreds you’ll spend to make it happen.

And, finally, custom tunes are available for 87 octane, which does save money at the pump. Low restriction exhaust and a (functional) cold-air intake can get the car moving with less throttle input. But this is still less bang for the buck: the odds these modifications paying for themselves in fuel savings sometime in the next decade are not likely.

So forget your notions and take my advice: modify to your taste, but only with performance in mind.

[Send your technical queries to mehta@ttac.com]