Date: Thu, 11 Dec 1997 12:51:06 -0500
Reply-To: Scot Douglas <sdoug@CONCENTRIC.NET>
Sender: Vanagon mailing list <Vanagon@Gerry.SDSC.EDU>
From: Scot Douglas <sdoug@CONCENTRIC.NET>
Organization: Mitsubishi Motors R&D of America
Subject: Re: engine swap (ignorant questions) -> EV piston slap
Content-Type: text/plain; charset=us-ascii
barwise@TUXEDO.ENET.DEC.COM wrote:
>
> Well, you don't have to believe EV "piston slap", but is is a true,
> unfortunate occurance with some EV 5 cyl. motors, including mine.
> Afterall, they're not the *exact* same engine as used in the cars anyway,
> though they are very similar. There are many variations of I-5 engines
> in use. I only know of piston slap in the EV variation.
>
> I examined my 5 cyl. EV engine with its head off. I could actually wiggle
> 2 of the pistons in the block so you could hear them hit the side of the cyl.
> wall, and the bores had been worn out-of-round.
>
Chris Wrote this:
> yes, they are all Audi 5 bangers.
> i think the "piston slap" thing is all HYPE yes.. HYPE
I don't believe "Piston Slap" is HYPE, as it was claimed. I have a
question about the angle of the inline 5 as it is used in the Audi; do
the pistons travel vertically, or is there some angle set from
vertical? I know from my EV that the engine is on an angle and if the
engine was designed to run upright, there is a very good chance of
piston slap.
How? For cylinders that run at an angle to vertical (at least on
Mitsubishi V6 engines), there is a piston pin offset that allows the
piston to "Rock" against the cylinder wall before combustion. If this
offset isn't present, the piston will rock to whichever side under
combustion and slam into the cylinder wall, causing the knocking sound.
I can also tell everybody that EV owners are paranoid people whining
about tappet noise. I've owned cars with tappet noise and I've owned
diesels; EV piston slap sounds just like a diesel; not the little
ticking I had in my 1.8L Jetta.
It's my bet that VW engineers didn't do all of their homework adapting
the Audi-5 to the EV. Doesn't the fact that VWoA is replacing my
pistons and possibly the engine block sound like a confession of a
problem? Most people know what it's like to get the average dealer to
cover a warranty item, and usually it's not easy for a problem such as
"Piston Slap".
I think VW has a part # for the pistons that include the proper pin
offset or at least are manufactured to tighter tolerances.
It is very easy to think of our German vehicles to be infallible,
especially with such experience as Chris has with his Audi 5 cylinders,
but to come out and say piston slap is hype and tell the EV owners with
the problem they are mistaken is wrong.
German engineering is excellent, but these people are human and will
make mistakes. I think that the original Audi design was also modified
to get the 2.5L; aren't the biggest Audi 5 cylinder engines 2.3L?
--
Best Regards,
Scot Douglas
Project Engineer; Chrysler/Mitsubishi Joint Programs
Mitsubishi Motors R&D of America
P: (313) 971-0900 x32
F: (313) 971-0901
