Throttle Body Balance

[IdahoArtie]

Anyone in the Boise area have a balancer I can rent/borrow?  My 2010 RT could idle better..just checked valves, new plugs, etc.  Might as well check for balance while the Tupperware is off.

Thanks.

[dirtrider]

7 minutes ago, IdahoArtie said:

Anyone in the Boise area have a balancer I can rent/borrow?  My 2010 RT could idle better..just checked valves, new plugs, etc.  Might as well check for balance while the Tupperware is off.

Thanks.

Afternoon   IdahoArtie

 

You can just make a homemade U tube manometer, those are typically more accurate than most purpose built aftermarket balancers.

 

Just remember that your idle balance is computer controlled using electronic idle steppers so you can't change the balance even if it is off a little.  

 

 

[IdahoArtie]

Mad scientist at work.  I'll check it out!  Thanks.

[IdahoArtie]

Not sure the manometer works, but a word of caution.  The research may lead you to this video. Off the manometer......

 

 

[lkraus]

The manometer most definitely works, it is the device that all the dial gauges and electronic gadgets are emulating.  It is very simple, but has been used in laboratories since the 1600's. NIST considers a primary standard to be one that does not require calibration, and is actually the standard to which other devices are matched. The U-tube manometer is a primary standard because the difference in height between the two columns is always a true indication of the pressure regardless of variations in the internal diameter of the tubing.  

 

 BMW specifies that when the throttle cables are adjusted properly there should be less than 15mbar pressure difference between the two intakes at 1400-1800 rpm.  For a manometer filled with mercury, that means the heights of the two columns should be within less than 0.44 inches of each other. Mercury is toxic and hard to get, so I use water for a manometer fluid. The lower density means that the column heights need to be within six inches of each other, a much easier target to hit. Light oils or ATF can expand the target even more, but I would manage to spill those somehow in storage. The water gets blown out until next year.

 

With patience, I can get the water column heights within a half inch of each other, at which point the readings change depending on how snug I make the lock nut.

 

[Danny caddyshack Noonan]

Well, "in the area of" can have many meanings.  I have a Twinmax and a Harmonizer and am at the other end of Lolo pass.  Might not be a pleasant ride in this heat and if you're off balance.

[dirtrider]

On 7/27/2022 at 12:09 PM, IdahoArtie said:

Not sure the manometer works

Morning IdahoArtie

 

A manometer works great on the BMW boxer motorcycles. A (U tube)  manometer only works on a very few engines as the engine has to be a 2 cylinder opposed with a 0° or 360° firing order as a U tube manometer measures one side intake vacuum against the other side's intake vacuum. In fact a simple H2o filled U tube type manometer is probably about the most accurate device you can use as there is no moving parts (other than the H2o) so there is no real friction in the device to skew the readings. 

 

On your 2010 camhead 1200 BMW gives pretty broad specs for the warm engine cross-side  idle  balance as the curb  idle spec is  25 Mbar (10" H2o) between sides. This is with held (locked) idle steppers. If you have a GS-911 you can manually lock the steppers in sync. If you don't have a GS-911 then you can cheat by warming the engine & having  your manometer all set up, hooked up, & ready to go.  Then just turn the key off (shut engine off) , then wait about 30 seconds, then re-start the engine (then allow engine idle to stabilize). That usually gives you a good minute (or usually even more time) to check your cross side balance  as it takes the engine electronics at least that long (usually much longer) to put the idle steppers back into independent control (ie the steppers stay locked in step with each other after re-start long enough to check your cross side balance). 

 

The idle cross side balance is not user adjustable so it it is what it is but if it isn't within the 25 Mbar (10" H2o) between sides then re-check your valve adjustment, and/or check for intake vacuum leaks, or check for low engine compression.  

 

The above-idle cross side balance (1400-1800)  RPM has a  slightly  lower spec at  15 Mbar (6" H2o) side to side but BMW recommends that it be the same or lower on the side that is lower at  curb idle. (so if the L/H side is 2" lower at curb idle then the L/H side should be slightly lower at 1400-1800 PRM's). 

 

If you don't have a GS-911 to lock the idle steppers then be careful in making your adjustments, if it takes too long to make the adjustments then at some point in the adjustment process the fueling control can unlock the steppers & allow them to work independent.

 

But the good news is that at above idle on a warm engine the steppers usually go into locked with each other automatically as the throttle is opened.  (basically become throttle plate followers for first part of the throttle opening to prevent a quick dropped-throttle engine stalling)

 

The BMW camhead manual also mentions that if there is a discrepancy between sides in the 1400-1800 RPM range  that it would like them to have the L/H side to be slightly ahead of the R/H side if possible. 

 

A little trick (or more like a safety measure) is to use a brake hose pinching pliers or even a pair of needle nose pliers to completely pinch (close off) one side hose going to manometer during engine starting & first idle. You can simply use needle nose pliers with a zip tie tight across the handles).

 

This prevents the engine from quickly sucking the H2o into the engine during, or right after, starting if the steppers are not responding or there are other issues.  Once the engine is running you can slowly release the pliers (slowly slide the zip tie off of the needle nose plier handles) to allow the manometer to start responding. 

__________________________________________

If you are seeing your rough idle after riding the motorcycle for a while then you might have one of your idle steppers getting lost (engine electronics don't know exactly where the stepper pintle is at as the commanded stepper counts don't match the actual stepper counts) 

 

To catch that I will usually run a long hose from each throttle body nipple to up under the seat. Then also route the purge hose to up under the seat. Then hook the purge hose to the correct side hose then block the other side off with a plug.  (you can leave the hoses running this way if you want so you can check the engine balance at any time without having to remove the plastics or try to reach way in with hemostats to try to remove vacuum caps & attach balance hoses) 

 

Then just ride the motorcycle as normal until the rough idle shows up  (do NOT turn engine off after rough idle shows up). Then just ride home (leave engine running)  then use the needle nose (2 pairs of needle nose) or 2 brake hose close-off pliers)   to pinch off both of those hoses running to under the seat (you don't want ANY chance of vacuum leaks in those hoses as you attach your manometer).

 

Now just hook your U tube manometer up to those hoses, release the needle nose pliers (or release the brake hose clamps) then see where the cross side balance is at. If you have a lost stepper it should show up on the manometer (might even try to suck the water out of the U tube so be careful when releasing the pliers). 

 

 

[TEDZ]

I use 2 stroke oil in the manometer with white paper on the piece of wood.  Makes it very easy to see.

[Rougarou]