Resistor Tuning

[Ebbo]

I’ve just finished doing a write up on ‘resistor tuning’ and thought I’d share it with you guys. I’ve fitted one of the devices to my 1200RT and its helped town running enormously for relatively small money.

 

http://www.ebbo.org/resistor_tuning.php

 

Merry Christmas to you all,

Martin

 

[T__]

Ebbo, unfortunately in all the testing I have done on IAT resistors including the 1200RT I have shown no real gain in performance or runability with IAT skewing..

 

I have shown a slight gain in cold starting & in cold pre 02 operation (before the 02 heats & comes on line)..

 

The BMW doesn’t seem to use the intake air sensor for much once the system is up to operating temperature.. One of the problems seems to be the BMW uses a large resistance change in a non linear format..

 

I guess if you are happy go for it..

 

Twisty

 

[Ebbo]

Hi Twisty, I wouldn’t know if BMW use a larger resistance than other makers, but it does need a pretty big resistor to make a difference on the 1200, and having a GS-911 is very handy to see what offset you are actually achieving on the IAT input. Something like a 20c reduction on the ambient temperature would be close to right; do you know what you achieved with your resistor mod? It might not have been enough to make any significant difference.

[T__]

Ebbo, it’s not so much the large resistance it is more the non linear input per degree that makes it difficult to just add a simple resistor..

 

The problem is as far as I have been able to tell the BMW Ma 2.2, 2.4 & BMS-K doesn’t use the intake air temp for much once it is out of cold start & past pre heated 02 operation.. It is used (at least on the older Ma 2.2 & Ma 2.4) for a little spark trimming..

 

The main usage of the intake sensor is to tell the fueling computer the engine is in a real cold start condition (if the engine temp & intake temp are fairly close the system must be cold start enable).. If it just used the engine temp it wouldn’t know a slightly warm engine from 90°f ambient temp soak..

 

The problem with your 20°c reduction is it will only be 20°c reduction at a very specific intake temp.. It isn’t a fixed ohm of resistance per degree of intake temp..

 

What I usually use for testing is a 1k variable pot with enough pigtail to allow it to be accessed while riding.. That way not only can I trim it while riding I can overkill the change to see if actually changes anything.. I sometimes also run with an injector duty cycle meter (to see if the pulse width changes) & will monitor the 02 sensor cross counts..

 

I just don’t show much while riding as the 02 sensor(s) trumps all the other fueling inputs when in closed loop & engine temp is the predominant fueling input (well other than the TPS & engine RPM) when in throttle crowd snap open loop or extreme high RPM’s..

 

Right now I am running a 380 ohm IAT resistor (fixed resistance) in line on my personal 1200RT as it seems to help the cold start slightly (not a lot though) & allows a cleaner cold ride off.. Once the engine is up to temp it seems to make no difference in the runability that I can tell or measure..

 

Twisty

 

[Peter Parts]

Big debate rages at Pelican Parts - largely between (1) technically skilled people and (2) those who believe in magic and are pretty clueless about electronics. Adding to the confusion, the Moderator said the AIT influences spark timing which doesn't seem to be true and NOBODY contradicts THAT Moderator.

 

No one could add much to Twisty1's remarks but let me try some thoughts.

 

Here's my take. The first issue is the misconception that you can add fuel and get more horses out. The peak A/F band is pretty wide and the stock fueling is mostly inside that band, even after trivial bolt-on breathing mods.

 

Perhaps the second problem is the total arrogance people have about having finely calibrated butt-dynos. Human judgments are just fine in many areas, providing they are collected by proper experimental methods (which I happen to do for a living).

 

At some moments stock fueling falls outside that band (esp. during strong acceleration when alpha-n ECUs are faulty). For such moments, running rich feels good. Also helps you be sloppy with the throttle. And lets you lug. For sure, running rich rarely feels bad and so folks kind of like the FRK boost. I'd say the belief that BMW is cheating people by going real lean is simply a "conspiracy theory" and mostly untrue. OK... maybe mpg advertizing claims matter a bit, but not at the cost of backfiring, lost HP, etc.

 

I've seen two AIT trim factor tables. Yes, not much influence above cool temperatures.

 

The AIT sensor has a quite low resistance at summer riding temperatures. So anything much you add (like to bring it down to below-freezing readings) will still bring it down to those temperatures at all ambient temperatures and so make it rich. In other words, the added resistance swamps the AIT sensor all the way down to pretty cool ambient temperatures.

 

You can also buy an FRK-like device for half the price that also has temperature compensation. That is clever but when you really do the numbers, can't amount to much benefit over the usual range of riding temperatures providing the GS911-reading temperature your FRK has given you is OK in the first instance.

[smiller]

The first issue is the misconception that you can add fuel and get more horses out.

Most vendors aren't claiming (nor are most buyers expecting) a horsepower increase, but rather an improvement in driveability. That note aside I agree with most everything you and Twisty said.

 

Butt dynos are amazing things. The guys on the K-bike forums are reporting that for only $300 the FRK cures everything from idle problems to flat spots to cam chain noise. Hey, it even increases fuel mileage. Flat amazing what a resistor can do.

[Ebbo]

As smiller says, this isn’t about horsepower gains, you have to be realistic about what you hope to gain from this and for me that’s rideablity

 

If you’re using a 1k pot you’re about 9k off where you need to be on a nice sunny 20c day to improve running. You’re quite right about none linearity of the resistor used in the IAT, but it can be compensated for as I’ve said in my write up.

 

At the end of the day you can try one of the better devices for little real money and decide for yourself if its really better or not.

[T__]

Ebbo, 9k eh.. That is so far below 0°c on the BMW 1150/1200 IAT sensor something not right there..

 

The OEM BMW sensor is about 5.5K at 0°c.. Add 9k to the 5.5K & the system would think it has a failed sensor..

 

I have to admit the most I have ever skewed the BMW system is 5K & even that showed no measurable improvement..

 

Have you actually measured the resistance on the box you installed? 9K sure sounds out of reality on the BMW system..

 

Twisty

 

[Peter Parts]

As smiller says, this isn’t about horsepower gains, you have to be realistic about what you hope to gain from this and for me that’s rideablity

 

If you’re using a 1k pot you’re about 9k off where you need to be on a nice sunny 20c day to improve running. You’re quite right about none linearity of the resistor used in the IAT, but it can be compensated for as I’ve said in my write up.

 

At the end of the day you can try one of the better devices for little real money and decide for yourself if its really better or not.

 

As of December 2009, the discussion has moved from Shroud of Turin miracle-HP talk to reach a very sane level of understanding, as above quote shows.

 

So let me summarize: making the A/F richer is nice. I've been saying that for a year. For everybody except those concerned about mpg or tank cruising range. No serious debate about that.

 

Next question is: how?

 

An AIT fooler is very crude method. In fact and as far as I can poorly see, it is exactly the same as increasing fuel pressure with a new regulator or larger flow injectors. Those are pretty discredited methods.

 

As I understand how the ECU uses the information, it adds a constant percent enrichment to all injections at all speeds and conditions and during starting too, as Twisty1 points out BUT it disables the AIT function. Cold temperatures like -5C (23F) might add 8% across the board. I hope others will correct me here. Sounds stupidly crude, eh.

 

A whole less crude, but still pretty crude doing enrichment, is the Techlusion. If an FRK/resistor device costs $300, then a Techlusion/brain should cost $10,000 (but actually costs $250). I'd say a Techlusion does all the same for the rider but much better, adjustable, does not disable AIT sensor, etc. and has an accelerator-pump function too.

 

Footnote: my old Techlusion is still sitting under the tank. After a few months of use, I unplugged it and found not enough change in performance to justify paying a few pennies for more gas and the extra carbon emissions. The stock fueling, even with exhaust and intake mods is just fine.

[Ebbo]

Can I suggest anyone interested in resistor tuning go visit the BoosterPlug website and read the technical stuff, it won’t take more than 5 mins it’s the best I’ve come across.

 

http://boosterplug.com/

 

[T__]

Ebbo, I don’t know what he is measuring but it sure isn’t the BMW intake sensor resistance.. His tables are w-a-y off of what I have measured on the BMW system..

 

 

Now either he is misinformed or he is covering up the real resistance he is using..

 

 

If a person wants to play you can make your own temperature compensating resistive set up for the IAT circuit..

 

When I had an 1150 & did extensive playing with the Air Intake Sensor I actually made up a harness for a temperature compensating IAT but never got around to installing it..

 

All you really need is a 2nd Air Intake Sensor & install that in series with the original (& get it into the intake air somewhere).. That will increase resistance in step with the original IAT to give the fueling computer a fairly skewed & colder signal than just the original.. Problem is as the ambient temperature gets down around 0°c or so the series IAT’s will have IAT circuit resistance so high (well over 10K) that the fueling computer will probably see the resistance in the circuit as OPEN (failed sensor) so will default the IAT string to nominal (somewhere around 21°c or so)..

 

What would be needed to make a 2nd temperature sensor work is a simple temperature switch that would shunt the 2nd sensor when it gets close to somewhere in the 5° to 10°c range..

 

I just never showed enough difference in the runability to pursue the IAT end of the BMW fueling control..

 

Now on my Ducati with open loop system IAT skewing was worth the effort as that system used a lot of IAT input for fuel trim..

 

 

Twisty

 

[Ebbo]

I can’t comment on the figures provided on the BoosterPlug website because I haven’t tested to see how accurate they are. What’s of interest to me is his description of how resistor tuning works.

 

I have an Accelerator Module on my 1200RT, it uses pretty much the same basic figures for temperature setback as the BoosterPlug does, but without the remote temperature sensor (I have a BooterPlug on order). My bike now feels more like it has quite well tuned carburetors than fuel injection and it will run down to 1500 rpm and pull away gently but happily, its rather like my old Airhead used to run, I never thought I’d see it run this well, especially with a simple plug and play device that needs no set up at all.

 

Lots of people on the UKGSer website have been fitting and trying the Accelerator module these passed few weeks and reporting back favorably, its here if you want to read it http://www.ukgser.com/forums/showthread.php?t=210687 You’ll need plenty of time, it runs to 26 pages… My write up is easier to get through http://www.ebbo.org/resistor_tuning.php

 

 

 

 

[T__]

Ebbo, I guess I don’t understand as my personal 1200 runs great & pulls well down to 1500 RPM.. Sounds like all these people had problems with their bike OR it ran good all along & they only noticed it after they spent money on something they perceived made it run better..

 

Years ago during a gasoline price jump in the U.S.A. the company I worked for was testing some fuel saving measures we could implement in our current automobiles.. Things like stronger throttle return springs,, shift lights,, staged throttle cams,, etc.. The problem we ran into is most couldn’t be tested on the Dyno as they didn’t actually change the engine fueling control or air resistance,, they were more driving habit oriented..

 

We got the driving public involved in the testing process as that seemed to be the most logical way to test.. Problem was ANYTHING we did to the customers vehicles improved their fuel economy (in some cases substantially).. We needed a controller so used a known non economy adder for the baseline.. That was simply fastening a rather high tec looking device to the air cleaner of the vehicle (basically a shinny penny in a fancy aluminum box).. That was an eye opener as over 65% of the test vehicles showed improved fuel economy some as high as 6%.. What we learned from that is you can’t allow the public to test fuel economy or performance improvements if they know they have been added as they change their driving habits or start paying attention to their vehicles..

 

Like I said in my first response if YOU are happy with your purchase go for it.. To get me to buy it show me the (verified) test data..

 

 

Twisty

 

[Ebbo]

I understand where you’re coming from Twisty1, but I never was that impressed with how well my bike ran, loved the bike, just didn’t like the way it ran in town too much, it always felt lumpy and intractable. It’s a better machine now, but I can’t provide any verified test data, just seat of the pants stuff I’m afraid. When I get the BoosterPlug I’ll test it against the Accelerator and also without ether device.

 

Have a good Christams all,

Martin

[Peter Parts]

I understand where you’re coming from Twisty1, but I never was that impressed with how well my bike ran, loved the bike, just didn’t like the way it ran in town too much, it always felt lumpy and intractable. It’s a better machine now, but I can’t provide any verified test data, just seat of the pants stuff I’m afraid. When I get the BoosterPlug I’ll test it against the Accelerator and also without ether device.

 

Have a good Christams all,

Martin

 

If you can, measure the "temperature" the ECU is recording from the AIT input line with a GS911. Might be helpful to also measure at different ambient temperatures since the BoosterPlug adjusts for ambient and the FRK does miracles of every sort.

 

Although I am pretty certain the AIT line has no influence on spark advance, I have never seen definitive evidence one way or the other. The whole matter of measuring spark advance with the Motronics is a giant can of worms to the shade-tree mechanic.

[Ebbo]

I understand where you’re coming from Twisty1, but I never was that impressed with how well my bike ran, loved the bike, just didn’t like the way it ran in town too much, it always felt lumpy and intractable. It’s a better machine now, but I can’t provide any verified test data, just seat of the pants stuff I’m afraid. When I get the BoosterPlug I’ll test it against the Accelerator and also without ether device.

 

Have a good Christams all,

Martin

 

If you can, measure the "temperature" the ECU is recording from the AIT input line with a GS911. Might be helpful to also measure at different ambient temperatures since the BoosterPlug adjusts for ambient and the FRK does miracles of every sort.

 

Although I am pretty certain the AIT line has no influence on spark advance, I have never seen definitive evidence one way or the other. The whole matter of measuring spark advance with the Motronics is a giant can of worms to the shade-tree mechanic.

It’s all part of my plans for the future Peter, I’ll be able to pick that information with my GS-911 as the temperatures slowly come up next year backed up by the same ol seat of the pants road testing, but, Just as a snippet of info, I’m getting a 15c setback on the IAT sensor with an ambient temperature of 7c in my garage (that’s with the Accelerator Module). The ambient temp comes from the both cylinder head sensors which luckily agree with my digital thermometer.

 

If we don’t really know if the IAT can influence spark its maybe best to say it’s a possible, and at the end of the day it probably doesn’t matter so long as the outcome is what we want.

 

[AndyW9999]

I mentioned to a friend of mine that a lot of GSers have fitted the 'Accelerator' and are reporting positively (ukGSer link in a post above;-)

 

As he rides an RT he's looking for more feedback from RT riders....anyone?

 

Thanks for that andy ... I also found this forum discussing the accelerator ... http://www.bmwlt.com/forums/showthread.php?p=451608 Reading this all, I must say I'm more confused now, especially the RT guy that reported consumption up to 39 m/g ... I think I will follow this a bit longer to read more comments from RT riders