frozen pt cruiser

Funny "ha ha" or funny "peculiar"? (That's how my mother always replied to such questions.)

Does the sound continue after the car is warmed up? - RM

are you referring to the diesel sound when you first start it?

My 02 sounds a little "rougher" when it`s cold, but after 1 or 2 miles ... everything is fine ...

My PT (2002 with 5-speed in southwestern Ontario) has made diesel-like noises since day one. I have requested the service manager at my dealership to include my comments with the vehicle's maintenance history; that is, I will not be surprised when the engine dies prematurely.

OTOH, it has 55,000 Km so far and has never skipped a beat, summer or winter, including pulling a tent trailer to Nova Scotia and back.

YMMV.

Its not a problem, just a case of modern pistons that expand more slowly. GM has some real problems with piston slap in their cars- things like increased oil consumption.

Never had a car in 30 years that didn't sound and act "funny" when 1st starting out in very cold weather. stiff, noisy, etc.

Some late model Subarus are also plagued by piston slap. Apparently some of the marketing pressures (mileage? weight? power? emissions?) are causing the piston design parameters (skirt length to diameter ratio) to be pushed to the low end of acceptable limits - another case of creating a new problem to solve a perceived older one.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

Yep. I just had a first-hand example of how demanding hypereutectic pistons can be, unfortunately. Lucky me.

The idea is that the alloy expands less with heating than traditional eutectic or hypoeutectic alloy cast pistons (and WAY less than forged pistons), and this allows the piston clearnace to be set very small for tight sealing, which not only reduces emissions but helps fuel efficiency too. In addition, the piston pins can be centered rather than offset. They're normally offset in productin engines to provide a small force that keeps the piston "cocked" to one side in the bore and prevents it slapping around, but this adds friction. And then, as you mentioned, skirts are shortened to FURTHER reduce friction. I think any one of those ideas is fine, and maybe 2 of the 3 together would work in mass production. Certainly you make all 3 work together in a custom engine (so I hear :-p ), but it may just be too much to expect for mass production right now.

Old cars don't, they didn't have hypereutectic pistons with short skirts and ultra-thin ring lands. Detroit spent the 30s and 40s solving all those problems with things like T-slotted pistons, cam-ground pistons, strut-reinforced cast cam-ground pistons, offset piston pins, and autothermic pistons. But in the search for a little less friction and a little tighter sealing, hypereutectic pistons with ultra-short skirts are now popular and they rattle like a can of lead shot when they're cold.

At -5F, don't matter what's under the hood, it will sound a little weird until it warms a little.

--Geoff