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some further thorts...
1. Thinking that BMW will step up to the plate on bikes now some 16+ years old is futile. If they were ever going to, it would have been done by now. They have little to lose, and no upside when a few cranky old futs gripe about how their far-off-warranty machines work. I'm one of those.
2. If anyone is going to gripe about fuel quality, they're likely chasing a moving target. Fuel age? I've used 7-year old fuel from a resto project a friend did. He had a full tank sitting for SEVEN YEARS in his garage; I being the cheapskate that I am, could not let him simply dispose of it (what could he have done?). I ran some first in my lawnmower, without issues; then in my bike, again without issues. That seven years of storage was in average humidity of 70-plus percent.
3. Back in the 80s, BMW and other car makers ran into problems with fuel condensing in a gummy mess on the back and stems of intake valves. BMW tried a number of things and physical deposit removal via walnut shell blasting seemed to cure the issues - temporarily. It turned out that changing EPA regulations had altered the composition of fuel sold nationwide, leading to deposit issues. In response and after several years of poor consumer experiences, a new federal regulation required a certain minimum detergent additive level in fuels. BMW (and others, including Toyota) found the detergent level insufficient and formulated among themselves a new fuel standard, which came to be known as Top Tier, having FIVE TIMES the federally mandated detergent content. That seemed to solve the problems of the 80s. (That direct injection engines are now/again experiencing somewhat similar problems is a different matter I'll not go into). SOOOOOOO.... if you can, find out whether your local fuel supplier is giving you Top Tier gas. Here in Hawaii, it's all Top Tier, yet we (I) still have stalling issues. I've learned not to let the throttle go to rest at stops if the engine is past the high-idle warmup mode.
4. I got one of the O2 sensor signal manipulators that makes the ECU think it's 20 degrees colder, thus supposedly richening the mixture. As pointed out above, the ECU soon "learns" of this and the device has been of little use. The AX-FIED or whatever, which unit I don't have, may be better, it certainly should be for the greater cost.

Some say a little knowledge is a dangerous thing. There's "knowledge" floating about in reference to the hot stall issue, but no one seems to have reliably solved it, suggesting that either a) the problem has multiple causes and no one has correctly all of them, or b) some can sort the most pressing issue, leading to a subjectively better experience, but see a).
 

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I bought an AF-XiED & I'll let this list know how it works for me.

Given it's now winter in Michigan and my motivation to work on the bike is low, it may be a while. But I did pull the fuel tank yesterday, so I'm that far along. I'll also install additional starter circuit wiring to address the restart problem. Will probably buy the BMW harness kit 12 41 8 532 735 rather than trying to cobble together something.
 

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I have a new-in-bag BMW starter harness kit that I never used (the dealer put one on my GT after I'd already bought this one but hadn't installed it yet).

I'll dig it out of the garage and make your decent deal on it. :)
 
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Discussion Starter · #45 ·
some further thorts...
1. Thinking that BMW will step up to the plate on bikes now some 16+ years old is futile. If they were ever going to, it would have been done by now. They have little to lose, and no upside when a few cranky old futs gripe about how their far-off-warranty machines work. I'm one of those.
2. If anyone is going to gripe about fuel quality, they're likely chasing a moving target. Fuel age? I've used 7-year old fuel from a resto project a friend did. He had a full tank sitting for SEVEN YEARS in his garage; I being the cheapskate that I am, could not let him simply dispose of it (what could he have done?). I ran some first in my lawnmower, without issues; then in my bike, again without issues. That seven years of storage was in average humidity of 70-plus percent.
3. Back in the 80s, BMW and other car makers ran into problems with fuel condensing in a gummy mess on the back and stems of intake valves. BMW tried a number of things and physical deposit removal via walnut shell blasting seemed to cure the issues - temporarily. It turned out that changing EPA regulations had altered the composition of fuel sold nationwide, leading to deposit issues. In response and after several years of poor consumer experiences, a new federal regulation required a certain minimum detergent additive level in fuels. BMW (and others, including Toyota) found the detergent level insufficient and formulated among themselves a new fuel standard, which came to be known as Top Tier, having FIVE TIMES the federally mandated detergent content. That seemed to solve the problems of the 80s. (That direct injection engines are now/again experiencing somewhat similar problems is a different matter I'll not go into). SOOOOOOO.... if you can, find out whether your local fuel supplier is giving you Top Tier gas. Here in Hawaii, it's all Top Tier, yet we (I) still have stalling issues. I've learned not to let the throttle go to rest at stops if the engine is past the high-idle warmup mode.
4. I got one of the O2 sensor signal manipulators that makes the ECU think it's 20 degrees colder, thus supposedly richening the mixture. As pointed out above, the ECU soon "learns" of this and the device has been of little use. The AX-FIED or whatever, which unit I don't have, may be better, it certainly should be for the greater cost.

Some say a little knowledge is a dangerous thing. There's "knowledge" floating about in reference to the hot stall issue, but no one seems to have reliably solved it, suggesting that either a) the problem has multiple causes and no one has correctly all of them, or b) some can sort the most pressing issue, leading to a subjectively better experience, but see a).
Thanks for your thorts Honolulu. From one cranky old fut to another, it's a damn shame that BMW has little to lose and no upside when having to deal with us. But it's soooo true, they didn't make any money off my purchase did they? Will this stop me from buying another BMW down the road, probably not, but it sure as hell won't be a K13! It's looking like the purchase of an AF-XiED is in my future. Cheers
 

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Discussion Starter · #46 ·
I bought an AF-XiED & I'll let this list know how it works for me.

Given it's now winter in Michigan and my motivation to work on the bike is low, it may be a while. But I did pull the fuel tank yesterday, so I'm that far along. I'll also install additional starter circuit wiring to address the restart problem. Will probably buy the BMW harness kit 12 41 8 532 735 rather than trying to cobble together something.
Ahhh yes, winter...the one reason I love/hate living here. :rolleyes: Oh well, it gives us lots of time to figure out how to fix our bike problems. AF-XiED for me too. Where did you buy yours? Beemerboneyard?
 

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I have a new-in-bag BMW starter harness kit that I never used (the dealer put one on my GT after I'd already bought this one but hadn't installed it yet).

I'll dig it out of the garage and make your decent deal on it. :)
Awesome! And did the dealer-installed harness do the trick?
 

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Ahhh yes, winter...the one reason I love/hate living here. :rolleyes: Oh well, it gives us lots of time to figure out how to fix our bike problems. AF-XiED for me too. Where did you buy yours? Beemerboneyard?
Yes, I got the AF-XiED from Beemerboneyard. Mike was courteous enough to answer some questions I emailed them on Thanksgiving day. The conversation:

I wrote, "A couple weeks ago I saw a recommendation on k-bikes.com for the BoosterPlug, and I ordered one hoping it will cure a chronic problem my 2012 K1300S has had since new: sporadic engine stalls pulling to a stop.

Since then I've learned about the AF-KiED, and just now read a post claiming the BoosterPlug won't solve the problem, but that AF-KiED will.

However, none of the AF-XiED's product descriptions I've seen mention stalling at all. Several other benefits are promoted, but nothing about stalling.

What can you tell me?"

Mike replied, "Assuming there is nothing else wrong with your bike such as a faulty idle control device, etc the lean fueling on the stock bike will definitely be addressed by the AF-XIED. The reason the Booster Plug won't fix your issue is because it's effects are adjusted out by the ECU in the closed loop part of the fuel map and only remain in the open loop area which is not where the idle fueling is. Idle fueling is on the closed loop area of the fuel map and the only way to richen the closed loop area is through manipulation of the O2 sensor signal. That is exactly what the AF-XIED does. I hope this helps explain it."
 

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Botus says the O2 sensor (air temp) tweak of the Booster Plug is negated in close loop operation by the O2 sensor and ECU. Mike claims the AX-FIED modifies the closed loop portion of the fuel map by manipulating the O2 sensor signal. THEY ARE SAYING THE SAME THING for different products and if so, they'd both be negated in low rpm closed loop operation by the O2 and ECU.

Modern EFI operates in closed loop mode (integrated control of A/F ratio with both O2 and fuel map in the ECU) up to some point, say 1/2 throttle, then (gradually) goes beyond stochiometric to a richer fuel/air ratio that yields the best power. This is done to meet increasingly stringent emissions standards, and get better miles per gallon in the most commonly used rpm range.

Aside from simple O2 sensor signal manipulation, one of the operational intents of aftermarket devices is to reduce the point at which the A/F goes rich for power, making the power arrive at a lower rpm range. "More power" = feels good. There are several ways to achieve this, 1) replacing short term fuel adaptations stored in the ECU (which Botus strongly disfavors), or actual ECU remapping which is the (more expensive) proper way to fix what BMW may have bungled. Assuming one's machine is in fully correct working order, something very few can know for certain.

So if my reading is correct, Mike's "I hope this helps explain it" absolutely does not explain "it". I welcome anyone with better reading comprehension of the above, or deeper knowledge of EFI functional concepts, to cut it and set me straight.

vonBlitz, you might as well install the Booster Plug, since you have it, and it'll take about a 1/2 day to put it in (my experience, YMMV). Then ride some and tell us how it goes. If you later install the AX-FIED unit, we'd all like to hear how that goes, in comparison. If Botus and Mike are both correct, each device will yield similar results.
 

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Hi Honolulu, the difference is, the AF-Xied is connected to the O2/lamda sensor and spoofs the reading. This sensor is used in closed loop as you said.

The Booster plug is connected to the air temp sensor at the front of the bike. This sensor reading eventually gets corrected by the computer as it reads the other sensors/inputs, including the O2/lamda sensor.

So, if my thinking is correct, computer gets input from the O2 sensor and adjusts fuel ratio accordingly.

On a different bike, computer gets input from the booster plug, saying the air is colder than it is (I think that's the way it goes, not hotter), it adjusts the fuel ratio accordingly, but then gets input from the unadjusted lamda sensor, saying the bike is running too rich, accroding to its' stored fuel map, so it adjusts the fueling again, until the reading from the unadjusted lambda sensor is correct.

Hence, that is why the booster plug gets dialled out, but the lamda sensor does not.

This is what I remember from all my reading of the forums. I am not goign to do all that reading again :)

In your post you say
"Botus says the O2 sensor (air temp) tweak of the Booster Plug "

The O2 sensor and the air temp sensor are different sensors.
 

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The booster plug does not get connected to the air sensor at the front of the bike. It is connected to the air box temperature sensor circuit that monitors incoming combustion air. Every time I look at the sensor temperature reading on my GS 911 it is 20 degrees C cooler than ambient temperature. Noted though this is not underway.
 

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Fair enought Beech, I stand corrected.
But does the rest of my logic stand?

On a different bike, computer gets input from the booster plug, saying the air is colder than it is (I think that's the way it goes, not hotter), it adjusts the fuel ratio accordingly, but then gets input from the unadjusted lamda sensor, saying the bike is running too rich, accroding to its' stored fuel map, so it adjusts the fueling again, until the reading from the unadjusted lambda sensor is correct.
 

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I had to remove the actual PDF of booster plugs fuel injection. If you want a copy go their site directly. Trying to respect copyrights.
 

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Hi Beech,
here is a 2-page thread which compares the two, by Roger - who has tested both and is the developer of the Af-xied (note - develeoped it, doesn't sell it).
It's probably the least lenthy thread that contains explainations of how both the booster plug and afxied operate. If anyone wants to delve, there is a lot of info, but a lot of noise as well.

Hopefully we haven't hijacked the thread too much, but I'd say anyone with stalling issues can read all about it and take their chances/make their choice. If they're lucky, they may be near someone who can demonstrate the difference. I could swap out an afxied in a matter of minutes.

Now I must download and read the boosterplug booklet.

OK, I'm a fast reader :)

They are not contradicting each other (much). AF-xied only works in closed loop mode, i.e. constant speed (as stated by Roger), Booster plug only works in Open loop mode, ie. idle, and acceleration (as stated in the booklet). Where they differ is that Jens says that the lamda sensor can't be spoofed (which it can - as per emperic evidence/measurements by Roger) and that the closed loop fuel map is fixed. Roger states that the map is not fixed, but is adjusted by closed loop conditions, so a few tanks will also affect the open loop map.

Based on the above, I wonder if the AF-xied is best at adressing the constant speed stumble/hesitation (closed loop) that the Ks experience at around 3/ 4k revs, whereas the booster plug is best at addressing the idle speed stalling (open loop ).


Answer - buy which ever one addresses the issue you are having, or if you have loads of money, buy both :)

According to this threads issue - the booster plug is the way to go.

The issue I was having was the constant speed stumble/hesitation, and the af-xied fixed that.

Well, I didn't think I'd arrive at that conclusion tonight, every day's a school day 👨‍🎓
 

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Thanks, yes it is an interesting topic and benefits many people.
 
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