Non stock exhausts VS hot boxers

[peter f]

Well Gurus

Bible of Everything (http://www.haynes.co.uk/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&storeId=10001&productId=40207&langId=-1 ) states - page REF*39 - that most non stock exhausts cause the engine to run leaner, which make them to run hotter.

In fact...erm...well.. (12S VS Athens traffic ).

Any explanation? (my full HPE is a kat equipped thing - mind)

[throttlemeister]

Change back pressure/flow/scavenging and you need to change the intake too as it is all related. So yes, the bike will run leaner.

If you have a cat, that should not change things too dramatically for you, but you have to keep in mind that bikes these days are running very lean to start with. Proper fueling with a PCIII or RB will not only make them run better, but also keep them running cooler.

Mind you, that with the cat you might want to remove that as it does not like proper fueling that much, causing it to either clog up or die, or both. Not over night, but they are expensive little things.

[on2wheels52]

But on the flip side, would not the decrease in backpressure aid in getting the 'hot' exhaust out of the engine, maybe not making up for the increase due to the leanness but offsetting it a bit?
Plus the aftermarket one is usually lighter. Wouldn't the engine have to do less 'work' than before? (nitpicking)
I think the real reason it would run hotter is because the modification will tend to induce more right wrist action, and that will cause the engine to work 'harder'.
Jim

[peter f]

>>> wrist action <<<

He He ...but no > I'm talking about riding the thing in Athens (have you ever been there?).

Since RapidBike3 is installed and I can switch it on/off at will > I'll try to do some tests and I'll post the results here - or I'll try to map (to the handlebar "operation mode" shifter) some more mild 3d maps (not me - the guru who does RB3 tricks).

Silly question > could make any difference using fully synthetic stuff instead of semi synthetic (15W-50)? (better heat "dissipation"?? - or that's plain stupid? )

[throttlemeister]

Originally Posted by on2wheels52

But on the flip side, would not the decrease in backpressure aid in getting the 'hot' exhaust out of the engine, maybe not making up for the increase due to the leanness but offsetting it a bit?
Plus the aftermarket one is usually lighter. Wouldn't the engine have to do less 'work' than before? (nitpicking)
I think the real reason it would run hotter is because the modification will tend to induce more right wrist action, and that will cause the engine to work 'harder'.
Jim

No. With increased scavenging, more exhaust is removed from the chamber, and at the same time, because you have a higher flow out, it sucks more air into the chamber through the intake. If you add more air for the same amount of fuel, you will get a leaner mixture. Leaner mixtures burn significantly hotter. If a mixture gets too lean, it can get so hot it melts the piston and the valves.

If you add fuel by using a RB or something, and not only correct the exhaust changes but also set it up for proper fueling (aka not like EPA wants), you mixture becomes significantly richer, and burns more slowly and cooler.

This can make huge differences in air cooled engines.

[Deans BMW]

Originally Posted by throttlemeister

No. With increased scavenging, more exhaust is removed from the chamber, and at the same time, because you have a higher flow out, it sucks more air into the chamber through the intake. If you add more air for the same amount of fuel, you will get a leaner mixture. Leaner mixtures burn significantly hotter. If a mixture gets too lean, it can get so hot it melts the piston and the valves.

If you add fuel by using a RB or something, and not only correct the exhaust changes but also set it up for proper fueling (aka not like EPA wants), you mixture becomes significantly richer, and burns more slowly and cooler.

This can make huge differences in air cooled engines.

The bikes ECU attemps to maintain a predetermined A/F ratio within its limits using its airflow caculations along with the oxygen sensor, the after market black boxes (trickers) modify the predetermined A/F ratio. With the Beemer, the ECU will do its job with such as a Remus or Akro etc. The after market black boxes can optomise the A/F ratio and in some cases like the MoTec also optomise the advance curve to take even further advantage of the potential increase in airflow thru the engine thus even better power characteristics.

Or something like that

[peter f]

Originally Posted by Deans BMW

T With the Beemer, the ECU will do its job with such as a Remus or Akro etc.

Erm...you mean that stock ECU can cope with flow/back pressure alteration(s) and thus...well...the ex (stock pipe) lean mixture "equals" the current (HPE) lean mixture?

If so...Yikes! I forgot the question...

He He

[Deans BMW]

The stock ECU can cope within limits. Riding in hot weather slowly in heavy traffic IMHO requires low throttle settings and keeping the RPM low, you do not lug your engine with LOW THROTTLE SETTINGS AT LOW RPMS. I have seen a lot of riders with aircooled Beemers riding in heavy traffic on hot days running in lower gears thinking if they run below 3 or 4K R's they will be lugging the engine. The only thing they are doing in that situation is ensuring that their engine runs as hot as possible.

On my R1200ST, when returning home on my 3 mile very rocky unmaintained dirt road in the summer, temps in the 90's, the prevaling breeze is always to my back thus virtually no airflow over the engine, I run in 2nd or 3rd at 1,500 RPM with only the slightest throttle opening, the engine stays nice and cool. I have a full Remus system with the race can, very little back pressure. Everything else box stock. My A/F ratio remains the same as stock even with the decrease in back pressure, admittedly a little on the lean side.

[MaineRoads]

I was told the bikes ecu could compensate also......except if you run for extended periods at wide open throttle, the bike will then run on a preset fueling map and then you could run into "lean" trouble.

[BMW Atlanta]

it's much more involved then the computer adjusting for a set A/F ration, that only happens off idle and in cruise mode. The current generation R12's will adapt fairly well just off idle throughout out the RPM range if operated at less then 80% throttle opening with just about any aftermarket exhaust and air filter. However once you go into WOT mode, the ECU no longer adjusts and goes into a static map which will be on the lean side, potentially lean enough to rob hp, but not dangerously lean. If you plan on the bike to be a track or race bike, re-mapping would be highly recommended as the bike will be spending alot of time in WOT condition where it could greatly benefit from more fuel. For most folks on the road this is of little concern unless you have an overwhelmingly loud birdie on your shoulder reminding you of the overly lean condition at prolonged WOT conditions.

[Peter Parts]

I never have reservations about things BMWAtlantla posts and stated all very clearly here. In the comments below, I can speak only about what I see in the Motronic 2.4 and not sure how the R12S ECU might differ.

In thinking about fueling, there are number of critical issues that he or Roger for that matter, may not have a satisfactory handle on.

1. Of greatest importance, nobody has a sense of how often people jog their throttle. Each time you jog it, you return to map (static) mode which is not lean, unlike feedback (closed-loop). Hint: a couple of times a minute, unless you've fallen asleep.

2. Nobody has a sense how big of a jog is needed to return to map mode or how little a jog will keep you closed-loop.

3. Nobody has a good sense at what point at low throttle settings, you are committed to map mode. Related to that, and to Deans BMW observations, nobody has a good sense at what road speeds and gears you are in that range since you can't just eyeball the degree of throttle advance. Likewise, nobody is sure where the ECU thinks WOT begins (80%???) or when riding, actually knows when you hand gets there.

4. Nobody has a good sense how long it takes for the ECU to decide you are no longer moving your throttle and/or accelerating (PCIII is very fast, but stock ECU is not).

5. Nobody has a sense of how fast the ECU segues into close-loop mode once it decides you are no longer accelerating.

By now - finally - there's no serious dispute about the general outlines of the alpha-n 2.4 software architecture. But without a good sense of these issues, a lot of discussions are poorly anchored in the real-world.

[BMW Atlanta]

ditto all of that. I can comment on what our perception is on the dyno though. The new BMS-K is much faster at switching from open to closed loop then the previous motronic versions and it's almost seemless according to the gas analyzer and dyno curve.

[roger albert]

Rearding Ben's post:

#1 Of course no one knows what anyone else does, but they ought to have a sense of their own habits. Maybe I'm wrong, and that only comes from closed-course guys

#2 look inside a few TPS, and play on a dyno and read the gas sniffer, and you'll get a good

#3 See #2 and numerous posts here from early on back when people were actually experimenting and figuring things out instead of writing pseudo-learned and/or speculative "informative" papers. Btw, iirc, WOT is defineed around 75deg.

#4 and #5 About 1 second, or a tick over that.

Ben, do not confuse your own ignorance with others'

[shreddr]

what the hells up with this forum? shall we change the name to Boxers and Insult Forum? Jesus when the moderators got chips on their shoulders somethings going on.

[MaineRoads]

Too many experts, a tech forum should be for learning (for people like me), But many have nothing more to learn apparently.

[peter f]

Originally Posted by MaineRoads

Too many experts, a tech forum should be for learning (for people like me), But many have nothing more to learn apparently.

PEACE gentlemen.

Sum-Up >

1. that silly 12S ECU does (or DOES NOT) have "some" learning/adaptation/something/anything capabilities on hand?

2. if yes, and forgetting WOT and the likes (useless in real-life/non track) is that "some" "good enough" with regard non-stock pipework? I mean : is the lean mixture the good/OK lean mixture? (or should I/you operate with RB3 always ON?)

[roger albert]

Not sure why sheddr thinks there's a chip. One does get tired of sniping (yes, I'm using that word too much of late) from the same quarters. You can't spend all your time spoon feeding the same problem children on the same task. Well, I can't anyway.

Steve, I think everybody has more to learn. I'd quit doing tech stuff if I didn't. But the basics and rehashes do get boring sometimes, so one focuses on new things. For me, it's racing. For Ben, it's (apparently) delving into the ECU. Not a bad thing. I'd encourage it. Ben knows a crapload more about them than he did a couple years ago and brings up very good points these days. It's all good.

[shreddr]

Originally Posted by roger albert

Rearding Ben's post:


Ben, do not confuse your own ignorance with others'

This is the chip i'm talking about...

[Peter Parts]

Originally Posted by shreddr

This is the chip i'm talking about...

Thank you, shreddr. It is disheartening to be charged with ignorance since I recently put some time and money into answering the issues I raised on one of those new-fangled part-load dynos. And thanks to BMW Atlanta for acknowledging with a "ditto" the significance of raising these points (and thanks for providing some answers too).

But I think I owe MaineRoads an explanation - I suppose some members might feel like they are coming into a movie in the middle.

An essential heat issue in this thread, as ThrottleMeister, Deans BMW, and others have pointed out is the air-fuel ratio. To this matter, there has been an ongoing discussion about the A/F of the R1100S. Nobody says the normal map-based mode is lean (and I seem to be still taking a lot of heat in reporting my measurements that it is happily smack in the middle of the max power peak kind-of-rich A/F). Also, there's general agreement the closed-loop mode is kind of lean (and causes surging as a result and could propel overheating too).

So the important question becomes: how much of the time is the R1100S (and possibly the 1200S) in closed-loop mode. BTW, if it were closed-loop a whole lot of the time, you'd have surging a whole lot of the time. Likewise, each of the issues I mentioned in my first harshly-criticized post, is part of what determines if your bike's ECU is closed-loop or not at any instant in time.

For example, each time you jog the throttle, the ECU returns (or remains for a while longer) in map-mode. If you grab tight and/or jog the throttle roughly every 5 seconds as I do, you are not likely to ever be in closed-loop mode and therefore not llikely to be too lean for Athens or for any after-market muffler and air-filter.

Pay attention to your throttle hand and see how often you are jogging the throttle even a wee bit. Post your experience. Be sure to loosen your throttle-lock first!

Hope that helps.

I leave it to readers to decide if I am a stupid old jerk who is wasting everybody's time and posting harmful mis-information.

[throttlemeister]

To be fair Ben, your opinions have shifted significantly from the past. Much of the animosity is a result specifically from the way you presented certain things in the past.