On Feb 26, 9:38 pm, IGot2P <IGo...@[EMAIL PROTECTED]
> wrote:
> codifus wrote:
> > On Feb 26, 5:41 pm, E Meyer <epmeye...@[EMAIL PROTECTED]
> wrote:
>
> >>On 2/26/08 11:27 AM, in article fq1i5l$r4...@[EMAIL PROTECTED]
"IGot2P"
>
> >><IGo...@[EMAIL PROTECTED]
> wrote:
>
> >>>My 2008 3.5 SE Maxima turns 2,125 RPM when traveling at 60 MPH in 6th
> >>>gear (drive). This is a lot more RPM than our other vehicles turn at
the
> >>>same speed and two of them are 4WD pickups which one would think
would
> >>>be geared lower.
>
> >>>Anyone know if the above is normal or not?
>
> >>>Don
>
> >>Does it have a CVT? If so the engine RPM at different speeds will be
> >>different than what you may be used to with conventional
transmissions.
>
> > I forgot about that. With a CVT though, at cruise, the RPMS should be
> > lower than with a regular tranny. When accelerating, the engine will
> > hold RPM at its best torque area while speed rises due to the CVT
> > infinitely changing the gears, so to speak.
>
> > CD
>
> First, the pickups do have dramatically larger engines but our 3.8 Grand
> Prix also ran at a lower RPM than the 3.5 Maxima thus I don't think that
> the engine size is making the difference.
>
> It does have a CVT and as CD stated it does run a higher RPM when
> accelerating. I also thought that it should be lower than normal when
> cruising but the opposite is true.
>
> Guess that I will have to look up the transmission and rear end ratios,
> measure the rolling cir***ference of the tires and do some calculating.
>
> Don
1st, Your 3.8 Grand Prix, being 300 cc larger than the maxima's has
potential to have a beefier torque rating at the low end simply
because its larger. Not much, but it is.
2ndly, domestic motors, since they cant go to higher rpms, tend to be
designed do all their work at the low end, and therefore have valve
timing optimized to make the beefiest torque down low. With a peakier
and shorter torque curve, the gearing is chosen to spread the torque
more. The rpms are lower because the torque peak is higher. The rpms
rise faster because the torque curve is shorter.
The maxima with its slightly smaller engine and larger rpm range,
spreads its torque out more. Gearing for that motor is chosen to
optimize that broader rpm band, and hence you wind up with that cruise
rpm. It's a little high, but rises more slowly. In other words you'll
be at 2000 rpms at 60 mph, then 2300 at 70 mph etc. The Grand prix, I
bet, will have a lower cruise rpm, but it rises faster as you
accelerate.
By the way, I hope you know that the 3.5 V6 in your Maxima as part of
the legendary VQ series of nissan motors. I had the 1st gen VQ in my
98 Maxima. At 80 mph in 5th gear, my engine (a 3.0 liter) was spinning
at 3000 rpms. I thought that was absurd but found out later that it
was normal for that engine. Not only that, even though it was spinning
so fast, it was dead silent and vibration free. The only way I could
tell the motor was running was by holding the ****fter. That was one
helluva refined motor. That's what made it such a great motor, well,
plus its more than decent power output.
CD
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