Jump to content
IGNORED

Throttle bodies


Urban Surfer

Recommended Posts

Urban Surfer

Where could I find a video of this procedure for an 1150 RT?

Or a step by step wright up would do.

Thanks in advance.

Link to comment
Urban Surfer

I bought a carb tune pro. Is it possible to set this up so I can adjust the throttle bodies while riding (under load)

Looks like this instrument only works vertically.

Link to comment

Hi Urban, the CarbTune would be a bit of a monster to use whilst moving (but I know it has been done).

However, if you set it up and get it to within 1.5 cm of mercury at about 4000 rpm, then it is going to be pretty good. Why do you feel you need to do it while riding? (I know some on this site do do it - especially using Twin Max units).

 

Andy

Link to comment

Andy,

 

When I sync the TB's, I always chose the 2500 RPM engine speed because at 4k RPM, the plates are opened too far and the difference in suction is not as notable as at 2500 RPM ;) And it works just great everytime for me...

 

Dan.

Link to comment

Fair point Dan, but I always select 3500 - 4500 becuase that is where these bikes seem to roun roughest and most often, so I like to get it as close as possible in that regime.

 

Andy

Link to comment
Urban Surfer

I have only found instructions how to do this using the twin max.

Seems I don't have to do it that way with the carb tune tool.

Thanks for the help!

Link to comment
Peter Parts
Fair point Dan, but I always select 3500 - 4500 becuase that is where these bikes seem to roun roughest and most often, so I like to get it as close as possible in that regime.

 

Andy

 

Beg to differ!

 

Tuning in your driveway at "4500 rpm" means opening the butterflies a TINY crack and has nothing to do with riding down the road at 4500 rpm and 60 mph or whatever where the under-load butterflies (and hence the TPS) are open much more.

 

In fact, it is screwy in the sense, that the ECU is all screwed up and confused because it is getting incomprehensible inconsistent inputs* that can not exist in real riding and were not imprinted in its little brain by BMW.

 

Ben

40F, riding weather in Toronto. yippee.

 

*the inputs are off the ECU map or at least in odd corners of the map - for example, the HES thinks you are doing 4500 rpm and TPS says you are a hair off idle.

Link to comment
do a search for Throttle body sync for dummies and you'll come up with what you need. Google or this board.

I love those guys, and had missed this one. Reading it, I realized that the next time I do a TBS, I need to get some fresh rubber tubing, and make sure that both tubes are the same length -- something I had never considered before.

 

One more comment, more applicable perhaps to an RT than to an R or GS. Because, by the next time I do a TBS I have forgotten which way I turned the BBS at the last TBS to move the balance left or right, I drew a couple of circles with arrows on a piece of tape that I stuck to the gas tank, just above the right hand throttle body.

Link to comment
Urban Surfer
Fair point Dan, but I always select 3500 - 4500 becuase that is where these bikes seem to roun roughest and most often, so I like to get it as close as possible in that regime.

 

Andy

 

Beg to differ!

 

Tuning in your driveway at "4500 rpm" means opening the butterflies a TINY crack and has nothing to do with riding down the road at 4500 rpm and 60 mph or whatever where the under-load butterflies (and hence the TPS) are open much more.

 

In fact, it is screwy in the sense, that the ECU is all screwed up and confused because it is getting incomprehensible inconsistent inputs* that can not exist in real riding and were not imprinted in its little brain by BMW.

 

Ben

40F, riding weather in Toronto. yippee.

 

*the inputs are off the ECU map or at least in odd corners of the map - for example, the HES thinks you are doing 4500 rpm and TPS says you are a hair off idle.

 

 

Soooo does one need to adjust throttle bodies under load?

And if so, how do they do it at a dealer?

Link to comment

Soooo does one need to adjust throttle bodies under load?

And if so, how do they do it at a dealer?

 

IMHO, what Ben says is absolutely right in theory, but the difference it makes in paractice is a much smaller thing.

That is why dealers & most everyone does it with the bike stationary under no load.

 

Andy

Link to comment

I do it stationary and get a good mileage while crusing, 5.1 liters / 100 kms, medium speed is ~ 80 kms/hour. Straight B roads, passing trough vilages and some twisties around mountains.

 

Dan.

Link to comment
Peter Parts

Soooo does one need to adjust throttle bodies under load?

And if so, how do they do it at a dealer?

 

IMHO, what Ben says is absolutely right in theory, but the difference it makes in paractice is a much smaller thing.

That is why dealers & most everyone does it with the bike stationary under no load.

 

Andy

 

I appreciate your measured reply. No quibble from me.

 

If your goal is simply getting the two butterflies to synch on a good day when the BBSs and the little crack of the butterflies aren't trading-off air flows or otherwise not offsetting one another falsely, driveway tuning (or MoDiTec) is OK.

 

Riding 15 minutes with a pair of vacuum gauges (or with a TwinMax that provides a lot less information) gives you a clearer picture of throat vacuums all across the throttle range. And it red-flags that trade-off mentioned above.

 

That is the Way of the Samurai. (I just made that up to sound pretentious... but you know what I mean.)

 

Ben

Link to comment
----

Soooo does one need to adjust throttle bodies under load?

And if so, how do they do it at a dealer?

 

Morning Urban Surfer

 

No, the manual states to do it stationary, the dealer’s MoDeTec is set up to do it stationary about every quality BMW shop I know does it stationary, most of us long time BMW tuners do it stationary.

 

Wouldn’t you think that if there was compelling reason to balance at road load and road speed there would be a verified written procedure for it?

 

One thing is: the less load at a fixed RPM the less the throttle plates are open for a given RPM so higher the engine vacuum is. The higher the engine vacuum the more the side to side delta.

As the throttle plates are opened farther under load the engine vacuum starts to fall off so the side to side delta is less important. As or near WOT the side to side vacuum variation is far less important.

 

People put way too much importance on getting the vacuum perfectly even side to side. The engine smoothness and even running has everything to do with even POWER side to side not even vacuum side to side.

You can short out a spark plug and still show even vacuum side to side but as we all know it will run like crap.

 

Using the engine vacuum delta as a tuning means is just an easy way to get the throttle bodies close on their opening and closing but really doesn’t indicate even power side to side.

 

If given a choice would you rather have even vacuum or even power?

 

No real harm in checking the down-the-road TB balance but no real need to either.

 

If you really want an even running engine set the TB balance (hot engine) to best possible statically at around 2k/3k then start riding the bike. Then tweak the throttle cable adjuster on one side about one nut flat and ride it again. Keep doing this until the engine is at it’s smoothest. You are aiming at even power side to side not even vacuum. Perfectly even vacuum is only important IF both sides of the engine are EXACTLY the same as far as cam grind, compression, spark timing, exhaust flow, intake flow, valve position, valve angle, valve recess, carbon build up, operating temperature, piston shape, etc.

 

 

 

 

 

 

 

Link to comment
That is the Way of the Samurai. (I just made that up to sound pretentious... but you know what I mean.)

 

Ben

Umm, wouldn't it be the way of the Teutonic Knight? :grin:

Link to comment

Yes, just for the hell of it, I used used the Carbtune on the bike in motion...I didn't see any difference :) !

 

However, it was just an exercise...I do static tuning on Darth and the bike runs like a champ :thumbsup:

Link to comment
Urban Surfer
----

Soooo does one need to adjust throttle bodies under load?

And if so, how do they do it at a dealer?

 

Morning Urban Surfer

 

No, the manual states to do it stationary, the dealer’s MoDeTec is set up to do it stationary about every quality BMW shop I know does it stationary, most of us long time BMW tuners do it stationary.

 

Wouldn’t you think that if there was compelling reason to balance at road load and road speed there would be a verified written procedure for it?

 

One thing is: the less load at a fixed RPM the less the throttle plates are open for a given RPM so higher the engine vacuum is. The higher the engine vacuum the more the side to side delta.

As the throttle plates are opened farther under load the engine vacuum starts to fall off so the side to side delta is less important. As or near WOT the side to side vacuum variation is far less important.

 

People put way too much importance on getting the vacuum perfectly even side to side. The engine smoothness and even running has everything to do with even POWER side to side not even vacuum side to side.

You can short out a spark plug and still show even vacuum side to side but as we all know it will run like crap.

 

Using the engine vacuum delta as a tuning means is just an easy way to get the throttle bodies close on their opening and closing but really doesn’t indicate even power side to side.

 

If given a choice would you rather have even vacuum or even power?

 

No real harm in checking the down-the-road TB balance but no real need to either.

 

If you really want an even running engine set the TB balance (hot engine) to best possible statically at around 2k/3k then start riding the bike. Then tweak the throttle cable adjuster on one side about one nut flat and ride it again. Keep doing this until the engine is at it’s smoothest. You are aiming at even power side to side not even vacuum. Perfectly even vacuum is only important IF both sides of the engine are EXACTLY the same as far as cam grind, compression, spark timing, exhaust flow, intake flow, valve position, valve angle, valve recess, carbon build up, operating temperature, piston shape, etc.

 

 

 

 

 

 

Brilliant!

Thanks, now I got it.

Link to comment
Peter Parts

Wouldn’t you think that if there was compelling reason to balance at road load and road speed there would be a verified written procedure for it?

 

One thing is: the less load at a fixed RPM the less the throttle plates are open for a given RPM so higher the engine vacuum is. The higher the engine vacuum the more the side to side delta.

As the throttle plates are opened farther under load the engine vacuum starts to fall off so the side to side delta is less important. As or near WOT the side to side vacuum variation is far less important.

 

People put way too much importance on getting the vacuum perfectly even side to side. The engine smoothness and even running has everything to do with even POWER side to side not even vacuum side to side.

You can short out a spark plug and still show even vacuum side to side but as we all know it will run like crap.

 

Very compelling reason(s) why shops don't do it. I guess you are kidding about BMW having instructions for owners tuning bikes with a dual vacuum gauges duct-taped to their bars. Or tuning in any other manner.

 

Are you talking about boxers or Harleys when it comes to the value of balance? If you have a way to measure the balance of power between cylinders, don't keep it a secret a second longer. Till then, I and everybody else have to use vacuum as a measure.

 

Odd to read so much objection to a simple, cheap, natural, good-methodology way to double-check a person's (or a shop's) synching. After 45 years, I have gained a modest skill at synching these twins but usually take my dual-vacuum jig (picture at URL below) and go riding around the block.

 

Ben

Link to comment

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...