Yamaha TRX850 Enthusiasts Forum

With the bike goin in for a service and tune.. Be interested to find out the TORQUE output of a std R1 to compare to what what results I'll get from the dyno on Tuesday.

my 02 had about 80ft,lbs

ok cheers...

Looking thro the service manual.. No specs on the std motor are listed H/power or torque wise... From memory I heard it was 73 h/power at 7,500rpm...??????? I had the bike on the dyno (80,000km)after a std carb/airbox with K&N rebuild and std headers with staintunes(restrictors removed) and was getting 76.59 h/power. 54.75ft-lbs torque.. Any idea on the std specs??? for a stock factory motor...

cobbadiggabuddyblooo wrote:Looking thro the service manual.. No specs on the std motor are listed H/power or torque wise... From memory I heard it was 73 h/power at 7,500rpm...??????? I had the bike on the dyno (80,000km)after a std carb/airbox with K&N rebuild and std headers with staintunes(restrictors removed) and was getting 76.59 h/power. 54.75ft-lbs torque.. Any idea on the std specs??? for a stock factory motor...

Torque in a normally aspirated engine is just a function of capacity and compression ratio, no? Hence an XT 600 and and an FZR600 (just taking as an example two 600cc engines) both produce around 46 or 48 ft/lb peak torque (from memory), although the XT, revving far lower (and not breathing as well, for the sake of argument) due to the configuration will make less peak power.

So the R1 will make as much torque as a 998cc (? I don't follow new bike specs as much these days ) NA engine with a 12.5:1 (?) compression ratio, and the TRX likewise should make "850ccs of torque".

I will no doubt be flamed to a crispy critter, but IIRC from my John Robinson handy book of tuning four strokes, capacity is a very strong determinant of the torque output and CR relatively weak.

so with an R1 do they take the capacity of a 250cc /com..ratio x 4 and a TRX 425cc/com..ratio x 2 to obtain these torque readings ????

Here Cobba,these will help you(and anyone else)understand the science and math behind torque and horsepower calculations:

http://kevinthenerd.googlepages.com/torque_vs_hp.html

http://www.epi-eng.com/piston_engine_te ... torque.htm

thanks mate once again..

interesting read that ,, thanks

cobbadiggabuddyblooo wrote:so with an R1 do they take the capacity of a 250cc /com..ratio x 4 and a TRX 425cc/com..ratio x 2 to obtain these torque readings ????

The torque will be measured from the crank or the back wheel - as to what they do to calculate torque when designing the engine on paper, search me. But it's just a question of total capacity and compression ratio. Generally, more cylinders = smaller individual pistons, con rods and valves = higher revs = more revs allowing for more power. Again, _peak_ torque of, say, an XT 6 and an FZR6 will be basically similar, but the XT won't be able to get much beyond 6k revs whereas the FZR will do 11-12, hence the difference in peak power.

Similarly, TRX and R1 peak torque should to all intents and purposes bear the relationship 850cc : 998cc, modified by the R1's (I assume) higher compression ratio. Difference in power at the crank will be down to revs and the combustion efficiency of the engine (i.e. how good is it at pumping and burning the mixture).

Now how the area under the curve is distributed is another question, but (again based on my recollection of Mr Robinson's clever books rather than anything better), the four should produce a broader power and torque spread than a single or twin and give you better area, assuming that the design and materials permit the four to use the extra revs.

If you are Honda and build a 6 cylinder 125 race bike (or a CBR250RR), for example, you may find that it can do 25,000 rpm for the requisite number of hours/minutes, but that you can't actually use the revs because you can't pump or burn the fuel at 25,000 rpm very well.

It`s also down to materials used and their properties,reliability issues,lubrication specifications,shear strengths etc,etc.
Multi`s are not really my cup of tea at all,even though I`ve ridden some that do impress.
I prefer motors that produce torque lower in their rev ranges,hence I only bother with singles and twins of higher capacities,I would be very interested to get a test of the new Triumph vertical twin:

http://www.triumph.co.uk/uk/12952.aspx

You can`t beat the feel of large dollops of torque at low revs.
I don`t like the styling or the cruiser types of bikes at all but I admire the way large capacity singles and twins make their power.

Torque is work done i.e. force x distance. In an engine the force is the pressure on the piston crown, he distance is the length of the crank throw (half the stroke).

Power is just the work done (torque) done in a faster time - the more work done in a shorter time the more power produced.
The higher you rev the engine for the same torque, the higher the power.

When you produce a power/torque curve with rpm on the base line and power and torque on the same scale on the verticle line the 2 curves ALWAYS intersect at 5250 rpm when using Imperial units (lb ft. and BHP)

That Triumph folks,check out the `figures`:

http://www.triumph.co.uk/media/Thunderb ... _Sheet.pdf

LUVERLY JUBBLY,mega torque at lowly revs
Oh and anyone notice just how part of that torque figure has been achieved other than just it`s huge capacity?
Look at the first specification(hint,crank)

Are you by any chance a DR800 owner?

Mincehead wrote: I prefer motors that produce torque lower in their rev ranges,hence I only bother with singles and twins of higher capacities

1600 twin...nice. I'd like to see a Cafe Racer version of that!

Mincehead wrote:That Triumph folks,check out the `figures`:

http://www.triumph.co.uk/media/Thunderb ... _Sheet.pdf

LUVERLY JUBBLY!!!!
Oh and anyone notice just how part of that torque figure has been achieved?
Look at the first specification.

Right, who's first in line to do a tbird/TRX hybrid... YZF rear wheel conversion permitted for this one.