Big Dog's Factory Stock Fuel Injection (S&S VFI)

[ezrstl]

I was reading through some of the 'Fuel Injection' threads and thought I might try to clear a few misconceptions of Big Dog's S&S Fuel Injection.
The S&S VFI that Big Dog uses on all of the fuel injected models is a 'self tuning' system that utilizes Wide-Band O2 sensors. The Wide-Band sensors have the ability to 'tell' the ECU to send as much fuel to the engine as it needs. The 'bottle-neck' on the entire system is the programming restrictions from the EPA. Hopefully my explanation on this will be clear...

Every EFI Big Dog has a Base Fuel Map. This ONE map controls most of the fuel to both front and rear cylinders. The Base Fuel Map cannot be changed in any way; the owner and dealer are both 'locked out' from making changes to the Base Fuel Map. Why? In order remain EPA compliant. Now, it sounds like I just contradicted myself, because I began by saying that the Big Dog EFI is a 'self tuning' system. So, if that Base Fuel Map cannot be changed, how then does the EFI system make fuel corrections? Remember, I said that the Base Fuel Map controls most of the fuel. The fine tuning adjustments are made by what is called the 'Adaptive Maps', and each cylinder has it's own Adaptive Map.

Let's say you are cruising down the highway in 6th gear at 2700 rpm, and at 23% throttle. Your Base Fuel Map in the ECU tells the injectors to run at pulse width of 3.27 ms (the bigger the number, the larger the pulse width, the more fuel the injectors blow at the engine). But because of the non-stock exhaust and air cleaner you are running, the pulse width of 3.27 ms isn't enought fuel to keep the engine happy, and if we cannot change the factory set Big Dog Base Fuel Map; because the EPA's restrictions locked us out, what is going to take care of the lean condition?

This is where the Adaptive Maps come in; and each cylinder, front and rear, has it's Adaptive Map. The Adaptive Map get's fed information from the facotry Wide-Band O2 sensor in each exhaust pipe. The O2 sensor tells the Adaptive Maps to either richen or lean out the Base Fuel Map. Basically, if the Base Fuel Map is not rich enough, the Adaptive Map tells the ECU to add fuel or richen the mixture by increasing the pulse width of the injector. So, when we are cruising down the highway in 6th gear at 2700 rpm, and at 23% throttle and the 3.27 ms pulse width isn't enought fuel, the Adaptive Map will add to the pulse width in order to keep the engine happy. The Adaptive's will also lean the pulse width if needed.

Now, enter the friendly EPA for a second time around. These Adaptive Maps have a limit on them too. The EPA's restrictions are that the Adaptive Maps can only move around 28% from the Base Fuel Map. That sounds like a lot and in some cases it is. But, add more compression and a more aggressive cam to the non-stock exhaust and air cleaner you already have, and the Adaptive Maps will 'Limit Out' and your Check Engine Light will come on. The light is telling you that the engine wants more fuel in a certain area (throttle position/rpm).

Once we make these type of modifications, we need a fully programmable ECU. The S&S unit allows us to make full and complete fuel corrections to the Base Fuel Map and has more un-restrained Adaptive Maps that are able to run and make the fine tuning changes the engine wants.

I haven't run into an EFI Big Dog that had air cleaner and exhaust mods only and needed the programmable S&S ECU. So far, all the bikes with just air cleaner and exhaust mods, the factory Big Dog ECU could handle the fuel needs. This is not to say that there are not Big Dog's with just air cleaner and exhaust mods that might need the programmable ECU; we just haven't run into them yet.

I have tuned 117's, 124's and a 145 using the S&S ECU and have had excellent results everytime. It a great piece of hardware with excellent fuel and timing management software. The only thing that must be changed on an EFI Big Dog when using the S&S unit is the ECU itself. Unplug the factory unit, plug in the programmable S&S unit and put it on the dyno in order to build the Base Fuel and Timing Maps. Then ride it and let the factory Wide-Band Exhaust Sensors feed information to the Adaptive Maps and let them make the final changes and tune on the Base Fuel Map. Another feature of the S&S ECU is after you ride it for a month or so, you can merge the Adaptive Maps into the Base Fuel Map, but that's a whole 'nuther story...

I have also worked with HD's Race Tuner, the Power Commanders on HD's and Metrics, and the Bazzaz unit for sport bikes. They all are designed to allow the user to optimize injector pulse width, and build the timing maps. Some like the S&S unit, Power Commander V, and the ThunderMax also give exhaust gas analisis to give even greater power to properly tune the engine.

Finally, I hope that this doesn't sound like an ad for S&S. It isn't. I only hoped to clear a few misunderstandings about the EFI controller that Big Dog elected to use on their bikes.

 

[KnotSo]

Great info and we all appreciate you sharing this:2thumbs:

 

[Brew]

Thanks for sharing...:2thumbs:

 

[Maxim_es]

Great post, thanks for sharing!

 

[chacha]

Good write up. So if the S&S VFI is not the same as the S&S ECU, where do you get an S&S ECU? And what do they cost?

 

[Mickeetwo]

Thanks for the info :2thumbs:

 

[ezrstl]

Good write up. So if the S&S VFI is not the same as the S&S ECU, where do you get an S&S ECU? And what do they cost?

I should have been more clear on this point. The S&S VFI (Varible Fuel Injection) uses the same S&S ECU (Electronic Control Unit) that I am speaking about. Actually, ECU is the verbage that Big Dog uses and S&S calls it a VFI Module. Sorry for the mix up.

 

[rwill20]

:flag:Thank You,good info.

 

[ezrstl]

I recieved an e-mail this morning from a member named Earl. He mentioned that he spoke with S&S about the sensors being Wide-Band or Narrow-Band and was told that they were Narrow-Band. I had a very similiar conversation about 3 months ago with S&S. One of our customers has a EFI Big Dog and is wanting to step up to the 585 cam. With the aftermarket air cleaner and exhaust, I felt that the stock ECU (VFI Module) would 'limit-out' and throw up a check engine light. So, after speaking with S&S, I was assured that the stock O2 sensors will work with all of the performance upgrades. The same O2 sensor in a stock Big Dog is the exact same sensor S&S uses on all of their VFI engines, including the 145's. This left me under the impression that the sensors were Wide-Band.
BUT, after again speaking with S&S this morning I was told the sensors S&S uses are NOT Wide-Band like I said they were in the first post. After talking at length with S&S about the 2 different types, the Wide-Band sensor is faster at sending information to the ECU. My question to S&S then was why were the S&S systems not using Wide-Band. Expense. Wide Band is faster but just like a computer, speed cost money and Wide-Band sensors are quite a bit more than their Narrow-Band cousin. At first, this didn't sit well with me, but he explained that the sensors they use can and do make the same changes, just not as fast. Speed is a relative term, what's fast to some is not fast to others. The question is, 'How fast does the sensor have to be?' This is, unfortunately, debatable, but there are some concrete facts in the equation that can help us hone in on an exceptable answer. Two of those 'facts' are the length of time the engine remains stationary throttle positions and rpms. The fuel maps for all of the EFI modules I have worked with are laid out similiar to a square grid. Throttle Position generally runs up the side of the grid and the RPM runs across the top. Where any particular throttle position and rpm meet on the grid; this area is called a 'site'. Each site has a number in it, and that number is the pulse width information for the injector. As we ride, each site tells the injectors how much fuel to send to the motor. During that time, the exhaust gas sensors read the fuel mixture and tells the adaptive maps to do one of three things richen, lean or leave the mixture as is.
Wide Bands are faster at doing this but both send the same information. One important factor is the length of time the engine spends at each site on the fuel map. This is when the sensors have time to make the changes to the adaptive maps. Understand, that there is not a tremendous amount of tuning going on when you are quickly on and off the throttle. Most of the tuning is done at constant throttle speeds and slow roll ons. It's true we don't always ride at steady throttle settings, so this is where is may take a few miles to make complete and proper changes to the map.
Finally, accurately creating the intial Base Fuel Map is of great importance, but a competent dyno facility can do the job for you.

 

[chacha]

Thanks for the clarification -- so can any shop reprogram the S&S ECU? How is the EPA lock-out removed to get upload a new base map?

Good insights...many thanks.

 

[Nomad2day]

I was reading through some of the 'Fuel Injection' threads and thought I might try to clear a few misconceptions of Big Dog's S&S Fuel Injection.
The S&S VFI that Big Dog uses on all of the fuel injected models is a 'self tuning' system that utilizes Wide-Band O2 sensors. The Wide-Band sensors have the ability to 'tell' the ECU to send as much fuel to the engine as it needs. The 'bottle-neck' on the entire system is the programming restrictions from the EPA. Hopefully my explanation on this will be clear...

Every EFI Big Dog has a Base Fuel Map. This ONE map controls most of the fuel to both front and rear cylinders. The Base Fuel Map cannot be changed in any way; the owner and dealer are both 'locked out' from making changes to the Base Fuel Map. Why? In order remain EPA compliant. Now, it sounds like I just contradicted myself, because I began by saying that the Big Dog EFI is a 'self tuning' system. So, if that Base Fuel Map cannot be changed, how then does the EFI system make fuel corrections? Remember, I said that the Base Fuel Map controls most of the fuel. The fine tuning adjustments are made by what is called the 'Adaptive Maps', and each cylinder has it's own Adaptive Map.

Let's say you are cruising down the highway in 6th gear at 2700 rpm, and at 23% throttle. Your Base Fuel Map in the ECU tells the injectors to run at pulse width of 3.27 ms (the bigger the number, the larger the pulse width, the more fuel the injectors blow at the engine). But because of the non-stock exhaust and air cleaner you are running, the pulse width of 3.27 ms isn't enought fuel to keep the engine happy, and if we cannot change the factory set Big Dog Base Fuel Map; because the EPA's restrictions locked us out, what is going to take care of the lean condition?

This is where the Adaptive Maps come in; and each cylinder, front and rear, has it's Adaptive Map. The Adaptive Map get's fed information from the facotry Wide-Band O2 sensor in each exhaust pipe. The O2 sensor tells the Adaptive Maps to either richen or lean out the Base Fuel Map. Basically, if the Base Fuel Map is not rich enough, the Adaptive Map tells the ECU to add fuel or richen the mixture by increasing the pulse width of the injector. So, when we are cruising down the highway in 6th gear at 2700 rpm, and at 23% throttle and the 3.27 ms pulse width isn't enought fuel, the Adaptive Map will add to the pulse width in order to keep the engine happy. The Adaptive's will also lean the pulse width if needed.

Now, enter the friendly EPA for a second time around. These Adaptive Maps have a limit on them too. The EPA's restrictions are that the Adaptive Maps can only move around 28% from the Base Fuel Map. That sounds like a lot and in some cases it is. But, add more compression and a more aggressive cam to the non-stock exhaust and air cleaner you already have, and the Adaptive Maps will 'Limit Out' and your Check Engine Light will come on. The light is telling you that the engine wants more fuel in a certain area (throttle position/rpm).

Once we make these type of modifications, we need a fully programmable ECU. The S&S unit allows us to make full and complete fuel corrections to the Base Fuel Map and has more un-restrained Adaptive Maps that are able to run and make the fine tuning changes the engine wants.

I haven't run into an EFI Big Dog that had air cleaner and exhaust mods only and needed the programmable S&S ECU. So far, all the bikes with just air cleaner and exhaust mods, the factory Big Dog ECU could handle the fuel needs. This is not to say that there are not Big Dog's with just air cleaner and exhaust mods that might need the programmable ECU; we just haven't run into them yet.

I have tuned 117's, 124's and a 145 using the S&S ECU and have had excellent results everytime. It a great piece of hardware with excellent fuel and timing management software. The only thing that must be changed on an EFI Big Dog when using the S&S unit is the ECU itself. Unplug the factory unit, plug in the programmable S&S unit and put it on the dyno in order to build the Base Fuel and Timing Maps. Then ride it and let the factory Wide-Band Exhaust Sensors feed information to the Adaptive Maps and let them make the final changes and tune on the Base Fuel Map. Another feature of the S&S ECU is after you ride it for a month or so, you can merge the Adaptive Maps into the Base Fuel Map, but that's a whole 'nuther story...

I have also worked with HD's Race Tuner, the Power Commanders on HD's and Metrics, and the Bazzaz unit for sport bikes. They all are designed to allow the user to optimize injector pulse width, and build the timing maps. Some like the S&S unit, Power Commander V, and the ThunderMax also give exhaust gas analisis to give even greater power to properly tune the engine.

Finally, I hope that this doesn't sound like an ad for S&S. It isn't. I only hoped to clear a few misunderstandings about the EFI controller that Big Dog elected to use on their bikes.

ezrstl,
I have spoken of the BDM installed version of the VFI having a single band O2 sensor in which I should say is really a narrow band O2 sensor not a wide band O2 sensor.
I agree the ECU uses an adaptive map and it is locked and limited in the tables by S&S for BDM on how far the tables can be modified in normal operation which does suck for the bike owner. From my understanding they can do a 20% learn from the base tables. Yes, throttle position, air temperature all play a part in the signal the ECU gets back from the O2 sensors to distribute the rate of fuel in ms that is dispenses until it sees the bike not under a load or in the case of a cold engine creating friction giving more fuel in the aspect it creates more power to over come this until the warm up table is satisfied.
I believe our bikes use a Zirconia metal type sensor which is old school, I could be wrong here which also is a narrow band sensor. Yes the lambda voltage does swing allowing you to change the map or be adaptive but has a limited voltage range and the voltage spikes back and forth to compensate for the load or cruising according to all the ECU inputs.
The Narrow Band Sensors to my understanding are readily identified 2,3 or 4 wires, ours have 4. A signal, ground, and 2 for the internal heaters in them to bring them up to temperature quicker for optimum performance. These sensor are not really designed for all out performance and yes can be used in tuning but to meet the needs to get a vehicle moving, cruise and make adjustments in those areas to save fuel and have a efficient running motor and to try to keep it at a 14.7 AFR which is good to meet those standards of a efficient motor burn and output of gases.
Now come the Wide Band Sensors the newest generation of O2's which perform the same as above but with 2 good qualities the narrow band can't compete with. With the new high efficiency motors, cars anyway and our O2 sensors are just car sensors, specifically Ford I think but are used on numerous vehicle makes, can make the adjustments quicker and have a larger "wider" band that it operates in which takes out the jerky motions of the narrow band spikes.
Wide band sensors typically have 5-6 wires.
Wide band sensors are calibrated to have a wide output response, whereas the passenger vehicles and OEM bikes are calibrated to have most accuracy around stoichiometry and very lean mixtures. A racing car or performance bike will spend much of its time at the opposite end of mixture strength, over-fueling for maximum performance.
That is what we are doing to our bikes, well some of us.
I use a Thundermax ECU with wide band sensors on my BDM Bulldog with good results.
I bet the S&S Replacement ECU is a fine piece as well and gives you all the functionality one could want. I am not sure if they have the data logging capability, perhaps you know seeing how you work with them.
Do you what the O2 sensors type really are that S&S uses? From the ones I removed they are a 0258986615, 4 wire. Ever search I have done just points them as being a universal basic sensor.
Perhaps my thinking is wrong here on what is narrow band and wide band O2 sensors and what BDM uses but that is the beauty of this site and what knowledge it is brings...
Thanks for your write up as well.
Neil

 

[erldawg]

Thanks for the clarification -- so can any shop reprogram the S&S ECU? How is the EPA lock-out removed to get upload a new base map?

Good insights...many thanks.

This responce is for S&S module only.....

To unlock the S&S EPA ECU module in our bikes it must be replaced. The new ECU module from S&S will be programed with a new base map for the particular engine size, pipes, air cleaner, throttle position sensor, etc: When ordering the replacement module this information is supplied to S&S and their staff will provide the base maps. After installing, the new module will learn and adapt to your engine and you'll have the ability to merge the maps and then it'll keep learning from there.
Any competent S&S VFI tuning center or anybody with the Pro Tune software and a USB cable can make map changes on the new module.

 

[erldawg]

ezrstl and Nomad ....

Great write ups. You two are light years ahead of me in learning about the EFI systems in our bikes and I'm trying to catch up. The problem I have is finding decent information on these systems so I'm not in the dark when it comes to troubleshooting and repairing these things. Hence that's why I ask so many questions and have had conflicting answers that's when I call S&S.

I find the explainations on the wide vs narrow very interesting and it would seem that the wide band is definitly faster in adjusting the amount of fuel to the injectors yet I remember reading on RB racing webite they actually use narrow band. Dislaimer is this may be on the tubo models only. I'll need to return and read it again.
If either of you can pass along any reading I'm more than welcome to have it.

Here'some interesting reading http://www.rbracing-rsr.com/efiharley.htm

Great write up guys,
Earl

 

[nine lives]

I like my carb.:2thumbs:

 

[V]

I like my carb.:2thumbs:

X2

But that is good info and the way of the future.

 

[fmschatz]

Great writeups on the EFI'S. I have replaced my ECU with the S&S programable ECU, with the dual runner air cleaner and the three upgrade cams for the X-wedge engine. Works great

 

[dnespolo]

Fred I would like to do some like that too. What do you mean when you say it works great compare to the original. More power, more..... what?
Thank you

 

[Boomer]

Great writeups on the EFI'S. I have replaced my ECU with the S&S programable ECU, with the dual runner air cleaner and the three upgrade cams for the X-wedge engine. Works great

X2 on more details! Which Air and Cams?

What did the ECU run ya? $500?

Now that warranty isn't much an issue, I might as well start upgrading my lil beeotch....

 

[RRRUFF]

Great info!

 

[dnespolo]

X2 on more details! Which Air and Cams?

What did the ECU run ya? $500?

Now that warranty isn't much an issue, I might as well start upgrading my lil beeotch....

Same here thinking about it.