Increasing torque on the boxer motor?

[CoarsegoldKid]

I don't know if I read something about this on BMWST or somewhere else but here is what I remember.

 

The cross pipe between the two headers has a narrower passage than what the pipe diameter would suggest. This narrower passage is a compromise between high and low end torque. Opening the passage increases low end torque and decreases high end. I have no idea if this makes sense in the world of tuning engines and making header pipes. If it were true wouldn't it be cool to have some sort of adjustable opening inside the pipe. I remember years ago there were something like this placed on Honda tail pipes back in the 60's called snubbers for another purpose. These days it could be electrically operated.

[NewBlue]

Kind of like what BMW now uses on the 2010 RT and Yamaha's EXUP

[Tony_K]

Peter Parts on this board speaks about the crossover on his 1100s and its restrictions and how to modify it. Maybe you saw that?

[TestPilot]

Kind of like what BMW now uses on the 2010 RT and Yamaha's EXUP

 

Please explain for those of us not too exhaust savvy.

[NewBlue]

Kind of like what BMW now uses on the 2010 RT and Yamaha's EXUP

 

Please explain for those of us not too exhaust savvy.

 

Here's a wiki link to exup http://en.wikipedia.org/wiki/4-stroke_power_valve_system

 

BMW added a variabe ECU controlled exhaust valve on the 2010RT, I imagine for the same reasons Yamaha did. Although some say it's just for a deeper exhaust note I don't think BMW would add it just for sound.

[TestPilot]

Thanks.

[CoarsegoldKid]

Kind of like what BMW now uses on the 2010 RT and Yamaha's EXUP

Yeah but in the cross pipe.

Thanks Tony.

[Froy]

Boost your torque

[Jerry Duke]

+1 Froy, probably the most bang for the buck I did to my R11S. I'm seriously thinking of doing it to my R12ST, but I'm torn between keeping it bone stock and starting down that slippery slope of "just this one little mod"....

[XTrooper]

Increase torque on the boxer motor?

 

You do it like this.

 

 

The Subaru 3.6L six-cylinder boxer engine with 256 horsepower and 247 lb-ft of torque.

[prof]

Has anyone here actually modified his exhaust crossover pipe to increase low end torque? Was the result noticeable and worth the effort? I ride a lot of 2 up with luggage and would be interested in more low end torque if I can do it myself without spending on complicated mods. Can anyone provide a link to this modification procedure. My searches are finding references to it, but not an actual description.

[Ken H.]

Personal opinion it would be more effective to swap out the FD for the lower 1st gear GS one if that's what you really want/need.

[dirtrider]

Has anyone here actually modified his exhaust crossover pipe to increase low end torque? Was the result noticeable and worth the effort? I ride a lot of 2 up with luggage and would be interested in more low end torque if I can do it myself without spending on complicated mods. Can anyone provide a link to this modification procedure. My searches are finding references to it, but not an actual description.

 

Morning prof

 

 

Pretty difficult to actually increase the engine torque in the lower RPM ranges without doing engine modifications. You can maybe move the existing torque band a little but not very much with tuning ONLY the exhaust, ignition, or fueling. The key word here is move it not increase it.

 

Ken’s suggestion of a lower rear final drive gear from a GS, GSA or the R bike would be the easiest way to increase low speed or launch “rear wheel torque”

 

If you want to keep your stock final drive gearing for lower RPM’s at hi-way speeds then maybe look into the 9 degree advanced cam gears available as aftermarket. Those do lower the engine torque band a fair amount but don’t actually increase the engine torque.

 

I know a few GS riders that have installed those advanced cam gears and it does make a noticeable difference in rider felt torque in the lower engine RPM ranges with a slight loss at higher RPM ranges. It does seem to take a fuel controller to get the most out of those gears though as the cam timing seems to drive different fueling at the lower RPM ranges.

 

[Jerry Duke]

I know of a couple of guys that have taken the time, and expense, to drill out the baffle in the cross-over pipe. One said it was noticeable, the other side it wasn't...

I like the GS FD idea, but for about $200 you can get the advanced cam sprockets.

[ShovelStrokeEd]

Never mind all the fooling around with exhaust this and gear ratio that. What you really want, if you are seeking low end torque improvement, is a heavier flywheel. The motor won't make any more torque but it sure will feel like it. You'll pay a minor penalty in absolute acceleration through the gears as the motor won't be as snappy in throttle response but you will stop complaining about the high first gear ratio.

[cpallen]

Personal opinion it would be more effective to swap out the FD for the lower 1st gear GS one if that's what you really want/need.

 

exactly what I was thinking: 3.0 final drive $600. I still can remember what a 4.11 gear did for my '66 GTO back in high school!

 

R1200RT Final Drive Options and rpm calculator

 

[David13]

Sounds like that common american syndrome, megalo mania. Bigger is better, more is better and necessary.

If you are really power hungry, why not just get the K bike. I know I can never have more than one bike again, because I can't then decide which bike to ride.

But other people without that issue can.

dc

[RLJ]

You can increase your mid range torque by making some minor modifactions. I increased mid range torque by 12 ft lbs over stock with a combination of full exhaust system (laser), cam sprockets and frk module. I dont know which part did the most improvement but this was varified with back to back dyno test on with stock R1200ST and my R1200ST with the listed modifications on the same dyno the same day. Peak hp was a little more but not much. I am very pleased with the result in real world riding, especially on twisting roads. The bike really rockets from corner to corner.

[cpallen]

Sounds like that common american syndrome, megalo mania. Bigger is better, more is better and necessary.

If you are really power hungry, why not just get the K bike. I know I can never have more than one bike again, because I can't then decide which bike to ride.

But other people without that issue can.

dc

 

I don't know about megalomania, but I love my RT except it sure could use a little more bottom end, for example starting out from a stop on a hill. And it loves to cruise at 4000 rpm - in 6th gear that's wee bit too fast. That 2.91 final drive ratio would solve both problems and the bike stays quiet. Call me crazy.

[IamBob]

Sounds like that common american syndrome, megalo mania. Bigger is better, more is better and necessary.

If you are really power hungry, why not just get the K bike. I know I can never have more than one bike again, because I can't then decide which bike to ride.

But other people without that issue can.

dc

 

I SOMEwhat agree. ALMOST as bad as spending 20k or more for a Harley, than spending another 10k on engine work to TRY to break 100HP.. What's the point?

 

Do you want a Harley, or do you want HP? You're not going to get both..

 

I bought what I liked, the way I liked it and that was the RT. It's a GREAT ride, and performs enough for me to get out of trouble when I need to, but more importantly not enough power to get me into trouble I don't need.

[prof]

Thanks for all the suggestions for performance mods, but this is getting more complicated, and more expensive, than I intended. The reason for asking about a crossover modification was simplicity and cost, and of course, effectiveness. I previously had an 1150RS and my mechanic swapped the intake manifold tubes for GS tubes, and the swap did increase low and mid range torque a little, but enough to notice. This was a very inexpensive and effective mod. Yes it lowered top end speed, but the difference between 115 and 125 MPH to me is negligible, since I never ride that fast. I'm not unhappy with the stock performance, but I could use a little more low end grunt from a stop riding 2 up with luggage.

[ShovelStrokeEd]

That's where about 10 or 15% more flywheel mass would fix it. The motor makes plenty of torque and, if you compare percent of RPM range, makes more torque than the much vaunted HD. It just doesn't have the flywheel to maintain RPM under low RPM conditions.

[markgoodrich]

That's where about 10 or 15% more flywheel mass would fix it. The motor makes plenty of torque and, if you compare percent of RPM range, makes more torque than the much vaunted HD. It just doesn't have the flywheel to maintain RPM under low RPM conditions.

 

Okay, I'll bite: where does one get this bigger flywheel?

[ShovelStrokeEd]

Ah Ha! There is the rub. No one, to my knowledge makes a heavier flywheel.

 

The problem is not insurmountable though. One could take a stock flywheel to a balance shop that does automotive crankshafts and the like and have them add some slugs of Mallory metal to the periphery. Should be able to increase mass by 10% easily and they can balance it (very critical). Be sure and let them know that this thing will spin pretty good RPM so they can secure the mounting properly.

 

Other than cost of removal/replacement, it shouldn't be all that expensive a proposition.