|
> > > i have a nissan altima 2008 - it's an automatic that can be thrown into a
> > > 'tiptronic' mode where you can shift up and down. while test driving it, the
> > > salesman said he like to use the tiptronic for engine braking.
> > >
> > > so, i've played with it some, and it just sounds harsh on the engine. i mean,
> > > there's obviously no gas being used, but tossing it into a low gear while going
> > > 30-50mph (i go down gear by gear... 5th, 4th, 3rd... etc) the rpm's still ramp
> > > up and the engine sound binded up.
> > >
> > > is there any risk of harm to the gear by engine braking? or is it something
> > > that can be done very slightly, or is it ok to just tap down into 3rd gear doing
> > > 45mph?
> >
> > The gears and transmission, kinda. The engine, definitely. Compression braking
> > isn't all that great for the engine. It puts more wear and tear on the engine,
> > particularly because you're making it run at high revs. Also, I don't know
> > about the more modern semiautomatic transmission designs, but older slushbox
> > automatics were kinda harsh when dropping gears like that, like downshifting a
> > stick without blipping the throttle and matching revs. Any kind of jerks like
> > that are bad for the drivetrain.
> >
> > Also, you are using gas. The ECM keeps flowing fuel to the engine even at
> > closed throttle in order to keep it lit. Granted, it's small compared to wide
> > open throttle, but it's there, and two to three times more than if you left it
> > in the higher gear.
> >
> > That said, it's a valid thing to do to get more braking power, and they do it
> > all the time in racing, but normally it's engine braking in conjunction with the
> > middle pedal, and they're not really concerned with longevity past, say, a few
> > hours.
> >
>
>
>
> so, the short answer is forget about it for daily braking then eh?
And anytime the engine and drivetrain don't sound happy, there's probably a good reason for it.
|
