'99-'00 172R vs 172SP: R is good? or the weak little brother?

[XrayYankee]

Just doing some looking at the difference, or perceived differences between the earlier (1998, 1999, 2000) 172Rs and the 172SPs. And besides the extra kW rating of the same size engine to produce the 180hp (on the SP) over the 160hp (on the R), I can't find much else different. (with the exception of maybe the leather seats, also on the SP.)
If anyone has flown both of these, is the difference (in hp) so much that the R is just too underpowered, or does the SP run at a higher RPM to achieve the extra hp, so that may be a negative? (I think I read that the R has 2,200 TBO and the SP 2,000 TBO, just to throw it out there).
Or, is it just that the R is a very nice plane and the SP, is the same thing, with just a little more pep if you need/want it.
Or put another way, are you just as excited to rent/fly an SP as an R?

Any thoughts or input, I'd be interested to hear.

[M]

The R has plenty of power climbing at the sea level. Both the R and SP
have the same engine and the SP has a finer pitch prop, so it climbs
better. Due to the coarser pitch prop, the R should have a slightly
better fuel efficiency at the same cruise speed as the SP.

[Jay Beckman]

"M" > wrote in message
oups.com...
> The R has plenty of power climbing at the sea level. Both the R and SP
> have the same engine and the SP has a finer pitch prop, so it climbs
> better. Due to the coarser pitch prop, the R should have a slightly
> better fuel efficiency at the same cruise speed as the SP.
>

How is it that with the same engine, they develop different HP ratings?

R = 160 BHP @ 2400rpm
S = 180 BHP @ 2700rpm

Is there a governor on the R model?

Jay B

[john smith]

> How is it that with the same engine, they develop different HP ratings?
> R = 160 BHP @ 2400rpm
> S = 180 BHP @ 2700rpm
> Is there a governor on the R model?

Throttle restriction.

[Greg Esres]

<<Is there a governor on the R model?>>

No, courser pitch prop. The blade has a higher angle of attack, so
more drag, resulting in less RPM. Horsepower is proportional to RPM.

[Scott Skylane]

john smith wrote:

>>How is it that with the same engine, they develop different HP ratings?
>>R = 160 BHP @ 2400rpm
>>S = 180 BHP @ 2700rpm
>>Is there a governor on the R model?
>
>
> Throttle restriction.

That is *completely* incorrect! As stated earlier, the R model uses a
higher pitched prop to keep maximum RPM's down. Thus the engine is only
able to produce 160hp output.

Happy Flying!
Scott Skylane
N92054

[Greg Farris]

They have a slightly different prop - the "SP" runs at a slightly higher
RPM, and as a result has a higher HP rating. You will not get any better
cruise out of it though. You may notice a "slightly" better climb
performance in the "SP" but basically, having flown both quite a bit, I
don't detect much difference - they fly the same.

Take a look at the panel. If you're looking into slightly older "R's" you
will likely find a King KLN89 type GPS, and an ADF. The slightly newer
"SP" series typically had Garmins, or KLN 94's and KMD-550 MFD's and they
eliminated the ADF (these are not hard and fast rules - you can find
either plane with either configuration, not to metnion the newer
G-1000's, but these are generalities). So if you want an ADF, you're more
likely to find it in an "R", and if you want a large, moving map display
you will be more likely to find it in an "SP".

Also, take a look at the W/B sheet. Those extra horsepower don't
translate to much preceptable extra performance, but they allow a
somewhat higher useful load. Depending on your needs, that could be an
appreciable difference!

GF

[Greg Copeland]

On Sat, 22 Apr 2006 13:14:53 +0000, john smith wrote:

>> How is it that with the same engine, they develop different HP ratings?
>> R = 160 BHP @ 2400rpm
>> S = 180 BHP @ 2700rpm
>> Is there a governor on the R model?
>
> Throttle restriction.

HP = torque*RPM; or h=t(rpm). If a prop is biting more air, the RPM will
be lower as a result of the higher load on the engine. Thus, the reported
HP will be lower. This is a great example of why comparing HP between cars
is usually a futile and meaningles exercise; especially when the engines
are dramatically different.

To confirm the numbers above for the sake of simple, relative
comparison:
R: t=160/2400; t = 0.067
S: t=180/2700; t = 0.067

Seems like the engines are following the same torque curve to me. ;)

For more reading...
http://en.wikipedia.org/wiki/Torque

Greg

[Robert Barker]

"Greg Copeland" > wrote in message
...
> On Sat, 22 Apr 2006 13:14:53 +0000, john smith wrote:
>
>>> How is it that with the same engine, they develop different HP ratings?
>>> R = 160 BHP @ 2400rpm
>>> S = 180 BHP @ 2700rpm
>>> Is there a governor on the R model?
>>
>> Throttle restriction.
>
> HP = torque*RPM; or h=t(rpm). If a prop is biting more air, the RPM will
> be lower as a result of the higher load on the engine. Thus, the reported
> HP will be lower. This is a great example of why comparing HP between cars
> is usually a futile and meaningles exercise; especially when the engines
> are dramatically different.
>
> To confirm the numbers above for the sake of simple, relative
> comparison:
> R: t=160/2400; t = 0.067
> S: t=180/2700; t = 0.067
>
> Seems like the engines are following the same torque curve to me. ;)
>
> For more reading...
> http://en.wikipedia.org/wiki/Torque
>
> Greg

Our club recently bought an R that had supposedly been re-propped to be
180hp. I was unsure about this but from what you're saying, it's
possible...

[M]

Robert Barker wrote:
>
> Our club recently bought an R that had supposedly been re-propped to be
> 180hp. I was unsure about this but from what you're saying, it's
> possible...

It'll probably take a STC to do this, but it should be extremely easy
to do. The engines are exactly the same O360-L2A. You can get all
that info right from their website.