Piston Slap: A Self-defeating Technology Disorder?

Sajeev Mehta
by Sajeev Mehta
piston slap a self defeating technology disorder

Felix writes:

Got a Mazda 3 hatch to replace my 29-year-old MR2, and while it’s no MR2, it has its own benefits. But I detest Hill Launch Assist, and the power steering is the biggest reminder that it’s no MR2.

The Mazda power steering is better than I expected, but it’s still the first thing I notice when I start it up and always makes me want the MR2 back, three years later. I tried turning the engine off on a private road with just enough slope to keep moving, and it’s kind of scary to imagine that happening on a freeway, it’s so stiff and jerky. Is there any way to disable it and having just plain manual steering, to see what it’s like?

As for Hill Assist, what annoys me the most is not knowing if a slope is enough to trigger it or not; if I expect it, and it didn’t engage, there’s a tire chirp for no reason, and if I don’t expect it but it did engage, I sometimes kill the engine unless I’m paying attention. I can understand its attraction for weenies who are just learning stick, but I don’t need it and don’t want it.

Sajeev answers:

Calling this a disorder is a bit much, so perhaps let’s just do it, to it.

Regarding the (intrusive?) Hill Launch Assist, considering these links ( here, here) and what little I know about SCT’s tuning parameters, there’s a slim chance a performance tune could disable Hill Launch Assist while giving you a few more ponies. Better ask SCT, as I had the opportunity to 100 percent kill AdvanceTrac on my 2011 Ranger. But my tail-happy little rig should default to implementing mindless, stress-free control on slick roads. I am rather surprised you’d defeat Hill Launch Assist for similar reasons.

But hey, I live in a flat city so who cares what I think?

As previously mentioned, you can probably pull a fuse/disconnect the plug at the steering motor to experience manual steering on a car with big-ish wheels and a small tiller. I suspect you will regret it the minute you take a low speed, high steering input, parking maneuver.

[Image: Mazda]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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  • Burgersandbeer Burgersandbeer on Jan 06, 2018

    My '08 5 series has hill assist. I had no idea when I bought it. The first time I expected it to roll and it didn't I thought I left the parking brake engaged or something else was wrong. Definitely a weird feeling. After 19 years in manuals I don't need it, but I can see it being convenient in some of the steeper areas of the SF area. Hopefully having it doesn't completely erode the hill start skill.

  • NG5 NG5 on Jan 06, 2018

    Surprising that there isn't a menu option to disable Hill Assist. There is on the Ford I drive. I curbed a wheel the first time I experienced it because I was parallel parking on a hill and didn't want to shift into reverse. I didn't realize what the car was doing. The system completely fooled me about where the clutch catch point was, and as soon as you touched the throttle the brake would drop entirely. Very disorienting first experience. I turned it off for months, but now I leave it on because I think it's better for clutch wear on hills. I hate having to move quick to avoid rolling back in traffic, and the temptation to ride the clutch if traffic is creeping uphill is too great. I'd recommend learning the system and getting used to it for those reasons.

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