what's different about the R1150R vs RS and RT

Post by **Dr. Strangelove** » Sun Apr 08, 2007 8:48 pm

Maybe a dumb question, but I cannot find the answer.

Why does the R1150R have 85 hp, yet the r1150RS and R1150RT have 95?

They appear to have the same engine, but there must be something different. Could the RR's engine be modified or tuned differently to RS (RT) specs? and how?

tia

John

Post by **yjleesvrr** » Sun Apr 08, 2007 10:43 pm

Yes. The R1150R and GS shared the same tuning. The R1150RT and RS had a higher tuned engine - not sure exactly how BMW did it other than perhaps fuel injection mapping. The R1200R has the higher tuned engine this time around a la R1200RT and R1200ST. The R1200GS has the weaker tuned engine.

Tripton · Post by **Tripton** » Sun Apr 08, 2007 11:38 pm

'round here they like to call it "tuned for torque" .....not?

Post by **yjleesvrr** » Mon Apr 09, 2007 3:53 pm

They were tuned for higher HP as well.

Post by **Dr. Strangelove** » Mon Apr 09, 2007 9:30 pm

so, can a dealer tune the RR to RS specs? Is this a big deal, time or $$ ?

Is there a down side to this?

What advantage is there to run a tuned down engine?

Post by **DJ Downunder** » Mon Apr 09, 2007 9:41 pm

Also I think it has something to do with the tubes that go between the fuel injectors and the engine..the GS length are short and give higher torque and less horse power..the RS are longer and have higher horse power and less torque..we have the GS ones. (maybe I have to the wronge way round)

Also the RS has higher compression I think..maybe different pistons..maybe even different cams...some else here will know for sure..but you can turn a RR into an RS without too much trouble..I think.

DJ

DK · Post by DK » Mon Apr 09, 2007 9:48 pm

I think another thing that is sometimes changed is the compression ratio to increase the HP on the same engine.

DK

Tripton · Post by **Tripton** » Mon Apr 09, 2007 10:04 pm

Tripton wrote:'round here they like to call it "tuned for torque" .....not?

I meant that OURS are tuned for torque. Which they are. Having a motor that needs to wind up to high revs to release a lot of power would be stupid in a bike that may go a bit off road, like a GS. Why it is in the 1150r....not sure. Probably just to make more friendly, usable power.

Post by **Dr. Strangelove** » Tue Apr 10, 2007 8:28 am

Specs RS
Engine Type: 1130 cc, 4 Stroke - Liquid Cooled - Boxer Twin
Engine Bore and Stroke: 100 mm x 70.5 mm
Compression Ratio: 11,3:1
Valves SOHC, 4 valves/cylinder
Carburetion: Electronic intake pipe injection
Ignition System: twin spark Ignition System:
Claimed Horsepower: 95 hp (70.8 kW) @ 7500 rpm
Maximum Torque: 100 Nm (73.8 ft. lbs) @ 5750 rpm

Specs RR
Engine Type: 1130 cc, 4 Stroke - Liquid Cooled - Boxer Twin
Engine Bore and Stroke: 101 mm x 70.5 mm
Compression Ratio: 10.3:1
Valves sohc, 4 valves/cylinder
Carburetion: Electronic intake pipe injection
Ignition System: digital engine management: Bosch Motronic MA 2.4 with overrun fuel cut-off, twin spark Ignition System:
Claimed Horsepower: 85 hp (63.4 kW) @ 6750 rpm
Maximum Torque: 98 Nm (72.3 ft. lbs) @ 5250 rpm

These numbers are from the Totalmotorcycle.com site
so... the RS has more hp, more torque and a higher compression ratio.

John

Post by **DJ Downunder** » Tue Apr 10, 2007 2:45 pm

RR

Motor Type
Four-stroke, two cylinder, horizontally opposed "Boxer" engine, air cooled
Bore x Stroke
101 x 70.5 mm (3.97 x 2.77 in)
Displacement
1130 cc
Max Power
85 hp (62.5 KW) at 6,750 rpm
Max Torque
98 Nm / 72 ft lb at 5,250 rpm
Compression Ratio
10.3 : 1
Valves Per Cylinder
4

RS

Motor Type
Four-stroke, two cylinder, horizontally opposed "Boxer" engine, air cooled
Bore x Stroke
101 x 70.5 mm (3.97 x 2.77 in)
Displacement
1130 cc
Max Power
95 hp (70 KW) at 7,250 rpm
Max Torque
100 Nm / 73 ft lb at 5,500 rpm
Compression Ratio
11.3 : 1
Valves Per Cylinder
4

That's odd...you are right..but it's still odd...

Maybe it's not about max power or torque afterall but more that it gets its max power and max torque at lower revs.

DJ

R4R&R · Post by **R4R&R** » Tue Apr 10, 2007 3:17 pm

Torque is what really gets you moving. HP is a 'cooler' rating.

My guess on the differences of the two motors is:
Higher compression pistons or differently designed compression chamber(that's obvious from the specs posted above)
Different camshafts (the cam is really the brains of an engine)
Different exhaust header (the RT/RS exhaust is a two-into-one header that goes into the cat-converter. Typically better for high RPM flow.)
Fuel injection mapping (of course it's different, the other components of the engine are different).

I'm sure the camshaft specs are different but that's not a normally posted spec unless shopping for aftermarket cams. A dealer may have the differences. Valve lift and duration of lift really dictates where the power is made, and how much.

I've never noticed the intake tubes being different sizes but it could be - that's another part of the engines 'tune'.

Post by **Dr. Strangelove** » Tue Apr 10, 2007 4:47 pm

so the RS has a "hotter" cam (changes the compression ratio?), and a more flow through exhaust.

What is also interesting is that the measures for torque and hp are at different rpms. So, maybe we are sort of comparing apples and oranges?

maybe the engines are not as different as these specs suggest, although those numbers are usually counted at the top of the curve, but we don't really know that for a fact.

anybody have the hp and torque ratings for the two engines at the same rpm's?

I do know that on a recent trip to NW Ark (beautiful, btw), my friend's RS would pull away from me on uphill straights.

John

Tripton · Post by **Tripton** » Tue Apr 10, 2007 11:08 pm

A hotter cam will not change the compression ratio.

The fact that the 95hp comes at a higher RPM is what I meant by tuned for torque. The RS motor makes more power, yes, but our motor makes it at a supposedly more 'useable' lower RPM. Thus, better for lower speeds, such as on dirt. Also might* be a bit more responsive.

From what I have heard, the transition to the higher hp is more money and effort than what it is worth.

JMHO.

Post by **DJ Downunder** » Tue Apr 10, 2007 11:32 pm

I agree..Max figures don't mean much..It's what the curve of the torque and horsepower looks like that's important...We need graphs.

DJ

R4R&R · Post by **R4R&R** » Wed Apr 11, 2007 7:53 am

Dr. Strangelove wrote:so the RS has a "hotter" cam (changes the compression ratio?), and a more flow through exhaust.

No, the cam doesn't change the compression ratio - the piston, cylinder size and compression chamber design does that.

Dr. Strangelove wrote:I do know that on a recent trip to NW Ark (beautiful, btw), my friend's RS would pull away from me on uphill straights.

Hence the higher RPM power. The roadster engine is tuned for lower RPM and in the upper RPM it's past it's peak power, when the RT motor is coming on strong. I wonder how much aerodynamics plays into that to? If you drag raced the two bikes, the R would take the RT off the line, and eventually the RT would get by the R. I test rode the R1150RS right after riding the R1150R and there was a big difference in the way the bikes performed. I preferred the lower RPM torque the roadster offered.

Croc · Post by **Croc** » Wed Apr 11, 2007 2:25 pm

Anyone use a Power Commander? I understand that this is one way to produce more power. This allows for manual changing of the fuel map. I have heard that it is best used with cat removed and an aftermarket can, K&N filter etc. No idea how much extra power can be produced, though.

Croc.