2023 ktm 250sx fuel

vdrsnk04 wrote:

Wouldn’t T2 work well being it is 40:1 and not really high octane? I’m sure I am way off base but thought I’d ask anyway.

Alex814 wrote:

Just run VPR. Oxygenated, leaded, ethanol-free. I believe it's the fuel used in T2. I'm not sure why so many people run VP110

JBoneMotorworks wrote:

Shaun- the 40/1 - 60/1 that they are speaking of is the air to fuel ratio, or it is posted as AF. The fuel/oil mixture is...

Shaun- the 40/1 - 60/1 that they are speaking of is the air to fuel ratio, or it is posted as AF. The fuel/oil mixture is richer at 40:1 bc it has more oil in it as compared to 60:1...all these ratios are divided by 128 oz in a gallon.

Here is a brief explanation related to a carbed bike, hopefully this simply explains it.

If you have a bike that has run @ 40:1 and then suddenly change it to 20:1 and you did not re-jet it to accommodate the change, although you have just richened your oil mix, it has leaned out the AF. Here is why.

40:1 down to 20:1 leaned out the AF bc the "thicker" and more slower moving fuel mix travels slower through the circuit but the same amount of God given air is pressurized into the engine. So the AF ratio of what the circuit will pass through it has slowed down in regard to the fuel, but not the air. So there is basically more air present ratio wise. The result of a lean AF can result in engine seizure.

Lets reverse this and go with a 40:1 to 60:1.

If you go from the 40:1 to a 60:1, although you have a leaner fuel/oil mix, your AF is richened bc now it has a FASTER mixture running through it. So again the same amount of God given air and more fuel than it needs. The bike will be potentially boggy or heavy feeling on the throttle and spooge, oil, etc is present. This is not necessarily oil, but unburnt fuel mix.

The bike will probably be down on power, fouling plugs, and what we tend to do is think "its at 60:1, how the heck am I fouling plugs with barely any oil in it". Its the unburnt fuel.

The richer you can make your 2 stroke in the fuel/oil area like a 20:1 will make much more power, but of course, going up on the jetting to balance the lean AF is key, the drawback is terrible throttle response, gummy power valves and the throttle pipe feels like it is got molasses in it lol.

The reason why the richer fuel/oil makes the better power is due to ring seal, piston seal, and film strength left on the inside of the engine.

I used to exclusively use Castor oil, (the kind you can put on a salad and eat it), and I have never seen such film strength on tear down rebuilds, oil all over coated perfect. The reason is due to the engine never getting hot enough to burn off the castor, so it leaves some behind..yes gummy power valves, but I would much rather spend some time clearing it then rebuilding top ends and cranks and plating cylinders.

I can't run castor in the new TBI's bc the rating for the premix oil is JASO rated oil and there is not a castor made that holds a JASO rating and the potential for there to be a gummy injector or whatnot is just not worth it..

Hope this helps, hope all is well with you friend- J

731chopper wrote:

Wow! So when I first bought my 125, it was spooging out the silencer and smoking more than I thought it should. I chalked it up...

Wow!

So when I first bought my 125, it was spooging out the silencer and smoking more than I thought it should. I chalked it up to something to do with the fuel injection and the motor being new. Then I fouled the plug the first time I rode it and started to question what gas the dealer put in the bike when they built it. There wasn't much in the tank so I filled the tank with the 50:1 VP I mixed up thinking this would dilute whatever they put in it enough to get it to run. I then took the plug out to clean it up and, sure enough, it was wet fouled.

I actually wet fouled the plug again trying to get it to run but after cleaning the plug a second time, I got the bike to fire and run like it should. After I got through the small amount of fuel that was originally in it, the bike runs like a bat out of hell. Looking back on it and reading what you wrote, I bet the dealer put 60:1 in the bike because they're the ones that told me to run 60:1 after all.

sandman768 wrote:

I have 3 rides, about 5 hrs on my 300SX. I have been mixing VP C-12 25% with 75% 90 Non Ethanol, figuring it’s bringing my...

I have 3 rides, about 5 hrs on my 300SX. I have been mixing VP C-12 25% with 75% 90 Non Ethanol, figuring it’s bringing my octane up to around 93-95. Map#1 feels like a slightly rich setting.. Map #2 feels super responsive & crisp, like a leaner setting. Map 1 seems to work fine with the minimum octane required, map 2 seems to want slightly better fuel IMO… I have a few motos on my bike, on a deep sand track in map 2, high rev”s, high load, my silencer tip was slightly whitish/ grey… This was with 50:1 oil/ gas ratio…

JBoneMotorworks wrote:

Post a pic of the plug if you can!

JBoneMotorworks wrote:

Post a pic of the plug if you can!

sandman768 wrote:

Be best to pull plug after a warm up & wide open run, then kill engine… correct…

JBoneMotorworks wrote:

VP110, VPR, C12, and T2 are all really high octane for these motors...run whatever you feel is best but the motors only really need 91-93 to...

VP110, VPR, C12, and T2 are all really high octane for these motors...run whatever you feel is best but the motors only really need 91-93 to run fine with great power.

JBoneMotorworks wrote:

Post a pic of the plug if you can!

sandman768 wrote:

Be best to pull plug after a warm up & wide open run, then kill engine… correct…

JBoneMotorworks wrote:

Post a pic of the plug if you can!

sandman768 wrote:

Be best to pull plug after a warm up & wide open run, then kill engine… correct…

JBoneMotorworks wrote:

Post a pic of the plug if you can!

sandman768 wrote:

Be best to pull plug after a warm up & wide open run, then kill engine… correct…

JBoneMotorworks wrote:

Ps- if you really want to make your brain hurt look up “wet line oil method” in jetting a two stroke lol

sandman768 wrote:

Be best to pull plug after a warm up & wide open run, then kill engine… correct…

JBoneMotorworks wrote:

Ps- if you really want to make your brain hurt look up “wet line oil method” in jetting a two stroke lol

bvm111 wrote:

I made it about two paragraphs into the article i found and went cross eyed 😂

JBoneMotorworks wrote:

Shaun- the 40/1 - 60/1 that they are speaking of is the air to fuel ratio, or it is posted as AF. The fuel/oil mixture is...

Shaun- the 40/1 - 60/1 that they are speaking of is the air to fuel ratio, or it is posted as AF. The fuel/oil mixture is richer at 40:1 bc it has more oil in it as compared to 60:1...all these ratios are divided by 128 oz in a gallon.

Here is a brief explanation related to a carbed bike, hopefully this simply explains it.

If you have a bike that has run @ 40:1 and then suddenly change it to 20:1 and you did not re-jet it to accommodate the change, although you have just richened your oil mix, it has leaned out the AF. Here is why.

40:1 down to 20:1 leaned out the AF bc the "thicker" and more slower moving fuel mix travels slower through the circuit but the same amount of God given air is pressurized into the engine. So the AF ratio of what the circuit will pass through it has slowed down in regard to the fuel, but not the air. So there is basically more air present ratio wise. The result of a lean AF can result in engine seizure.

Lets reverse this and go with a 40:1 to 60:1.

If you go from the 40:1 to a 60:1, although you have a leaner fuel/oil mix, your AF is richened bc now it has a FASTER mixture running through it. So again the same amount of God given air and more fuel than it needs. The bike will be potentially boggy or heavy feeling on the throttle and spooge, oil, etc is present. This is not necessarily oil, but unburnt fuel mix.

The bike will probably be down on power, fouling plugs, and what we tend to do is think "its at 60:1, how the heck am I fouling plugs with barely any oil in it". Its the unburnt fuel.

The richer you can make your 2 stroke in the fuel/oil area like a 20:1 will make much more power, but of course, going up on the jetting to balance the lean AF is key, the drawback is terrible throttle response, gummy power valves and the throttle pipe feels like it is got molasses in it lol.

The reason why the richer fuel/oil makes the better power is due to ring seal, piston seal, and film strength left on the inside of the engine.

I used to exclusively use Castor oil, (the kind you can put on a salad and eat it), and I have never seen such film strength on tear down rebuilds, oil all over coated perfect. The reason is due to the engine never getting hot enough to burn off the castor, so it leaves some behind..yes gummy power valves, but I would much rather spend some time clearing it then rebuilding top ends and cranks and plating cylinders.

I can't run castor in the new TBI's bc the rating for the premix oil is JASO rated oil and there is not a castor made that holds a JASO rating and the potential for there to be a gummy injector or whatnot is just not worth it..

Hope this helps, hope all is well with you friend- J

hellion wrote:

Good of you to explain a few things JBone. Too many people think race fuel makes their stock bikes faster. Ideally, you want enough octane to...

Good of you to explain a few things JBone. Too many people think race fuel makes their stock bikes faster. Ideally, you want enough octane to keep a bike from pinging/detonating and no more.

So, it sounds like there’s nothing in the FI system that would allow it to adjust for mods like a high compression head? Surely stock bikes are set to run on good pump fuel. But there must be quite a lot to be gained if you were to bump up compression and then use the fuel it calls for. Probably would need an aftermarket ignition like a vortex to make it all come together. Is there even an ignition available yet?

JBoneMotorworks wrote:

Hey Lee..yes you are correct. I called Vortex, they are not making anything this yr for these new MX bikes, GET ECU is making some right...

Hey Lee..yes you are correct. I called Vortex, they are not making anything this yr for these new MX bikes, GET ECU is making some right now and should have some more info in Jan on it.

The whole race gas mix ratio pump gas thing is kinda wordy and complicated and now gets a bit more specific due to the TBI.

The reason why there are more ponies to be had with a 93 pump gas has to do with the oxygenators in pump fuel, which is a good thing. 93 has roughly 3-4% oxygen in it. This helps it burn better, (O2 is highly explosive), the down side to the current method of oxygenating pump fuel is ETHANOL. It is the current standard for O2 additive but it attracts water like a sponge and pulls moisture out of thin air and collects it like a magnet.

You think, "hey I'm going to get some VPC12 110 with no ethanol in it"..that's great it will last a long time and not gum up but you also have no oxygen in it, VPC12 is non oxy. So it will burn a bit more linear as compared to 93 and not have the "punch" behind it.
So on a dyno, you would see more hp with 93 than 110...stock motor of course. If you bump up the compression, raise the octane with it to avoid detonation.


People cut their fuel to a 50/50 to get around 99 octane or so, thats great, bc you are adding oxygen into the mix but also ethanol. I recommend treating the pump gas with an enzyme to keep the ethanol at bay OR using a direct replacement fuel with a safe octane rating for the motor that has oxygen in it.

For ex) on my 23' 125sx, I'm. running VP T4 @ 40:1. It has an oxygen factor of 5.8%, unleaded, 97 octane. So it's only about max 2% oxygen over 93..thats very acceptable for an over spec oxy factor.

The other options are to run some sort of VP engine fuel like their can that is 94 efree small engine fuel and add some Nitro X (I have done this), to get a 3-5% oxy factor back in the fuel. I did a mod motor on my 16' 150sx that I cut with 110 and 94 efree and a 5% nitro oxy and you could hear that bike across the track up a Southwick lol,,it howled and run unreal.


The ECU is a non closed loop so it will never receive information back to make changes to the fuel circuit. It's called "Feedback" The lambda protocol can do this inside the ECU's that are tunable and "learn" from the feedback to it.

A small example of feedback would be like a typical PC screen that is LED. If you touch an icon with your finger on the desktop, nothing happens..however if you have a LCD screen that has a feedback and change protocol in it, you can touch an icon and it opens up and other window. Think the touch screen thing at the ATM.
So the stocker ECU is basically programmed to send a pre-determined amount of fuel over a certain rpm range given some factors and information that it gathers from the sensors, not internal engine values.
So the air temp sensor in the air-box will send info to the ECU that says, "hey it's 39 degrees out, when you send fuel, make sure you send the right amount bc cold.
The AF monitor says, "great info, thanks" and so on.
If changes are made to the head and it is cut to bump up the compression, this will make more heat, it will burn better, and more than likely lean out bc it is more efficient but the ECU won't know this so it will just continue to pump out what it has been told to push based on the sensors, not the volumetric efficiency.
So, although I want desperately to dive into the squish and porting, if I make changes that improve the flow and efficiency of the engine, I have no way to readdress this and will cause some issues.
On a 4stroke with like a Vortex, there are fuel trim dials, make a change, it runs better and a little leaner, dial in more and you are good to go.
This one, not so much.
Sorry this is wordy but it kinda lays out why it is so important to stay with the correct premix and fuel recommended by the mfg.


Talk soon! J

hellion wrote:

Good of you to explain a few things JBone. Too many people think race fuel makes their stock bikes faster. Ideally, you want enough octane to...

Good of you to explain a few things JBone. Too many people think race fuel makes their stock bikes faster. Ideally, you want enough octane to keep a bike from pinging/detonating and no more.

So, it sounds like there’s nothing in the FI system that would allow it to adjust for mods like a high compression head? Surely stock bikes are set to run on good pump fuel. But there must be quite a lot to be gained if you were to bump up compression and then use the fuel it calls for. Probably would need an aftermarket ignition like a vortex to make it all come together. Is there even an ignition available yet?

JBoneMotorworks wrote:

Hey Lee..yes you are correct. I called Vortex, they are not making anything this yr for these new MX bikes, GET ECU is making some right...

Hey Lee..yes you are correct. I called Vortex, they are not making anything this yr for these new MX bikes, GET ECU is making some right now and should have some more info in Jan on it.

The whole race gas mix ratio pump gas thing is kinda wordy and complicated and now gets a bit more specific due to the TBI.

The reason why there are more ponies to be had with a 93 pump gas has to do with the oxygenators in pump fuel, which is a good thing. 93 has roughly 3-4% oxygen in it. This helps it burn better, (O2 is highly explosive), the down side to the current method of oxygenating pump fuel is ETHANOL. It is the current standard for O2 additive but it attracts water like a sponge and pulls moisture out of thin air and collects it like a magnet.

You think, "hey I'm going to get some VPC12 110 with no ethanol in it"..that's great it will last a long time and not gum up but you also have no oxygen in it, VPC12 is non oxy. So it will burn a bit more linear as compared to 93 and not have the "punch" behind it.
So on a dyno, you would see more hp with 93 than 110...stock motor of course. If you bump up the compression, raise the octane with it to avoid detonation.


People cut their fuel to a 50/50 to get around 99 octane or so, thats great, bc you are adding oxygen into the mix but also ethanol. I recommend treating the pump gas with an enzyme to keep the ethanol at bay OR using a direct replacement fuel with a safe octane rating for the motor that has oxygen in it.

For ex) on my 23' 125sx, I'm. running VP T4 @ 40:1. It has an oxygen factor of 5.8%, unleaded, 97 octane. So it's only about max 2% oxygen over 93..thats very acceptable for an over spec oxy factor.

The other options are to run some sort of VP engine fuel like their can that is 94 efree small engine fuel and add some Nitro X (I have done this), to get a 3-5% oxy factor back in the fuel. I did a mod motor on my 16' 150sx that I cut with 110 and 94 efree and a 5% nitro oxy and you could hear that bike across the track up a Southwick lol,,it howled and run unreal.


The ECU is a non closed loop so it will never receive information back to make changes to the fuel circuit. It's called "Feedback" The lambda protocol can do this inside the ECU's that are tunable and "learn" from the feedback to it.

A small example of feedback would be like a typical PC screen that is LED. If you touch an icon with your finger on the desktop, nothing happens..however if you have a LCD screen that has a feedback and change protocol in it, you can touch an icon and it opens up and other window. Think the touch screen thing at the ATM.
So the stocker ECU is basically programmed to send a pre-determined amount of fuel over a certain rpm range given some factors and information that it gathers from the sensors, not internal engine values.
So the air temp sensor in the air-box will send info to the ECU that says, "hey it's 39 degrees out, when you send fuel, make sure you send the right amount bc cold.
The AF monitor says, "great info, thanks" and so on.
If changes are made to the head and it is cut to bump up the compression, this will make more heat, it will burn better, and more than likely lean out bc it is more efficient but the ECU won't know this so it will just continue to pump out what it has been told to push based on the sensors, not the volumetric efficiency.
So, although I want desperately to dive into the squish and porting, if I make changes that improve the flow and efficiency of the engine, I have no way to readdress this and will cause some issues.
On a 4stroke with like a Vortex, there are fuel trim dials, make a change, it runs better and a little leaner, dial in more and you are good to go.
This one, not so much.
Sorry this is wordy but it kinda lays out why it is so important to stay with the correct premix and fuel recommended by the mfg.


Talk soon! J

8tensolutions wrote:

So I am new to understanding the TBI, but are you saying the system does not adjust other than for air temp meaning it is not...

So I am new to understanding the TBI, but are you saying the system does not adjust other than for air temp meaning it is not reading the air/fuel mixture after combustion at all and adjusting the fuel according to that?  I guess I am assuming it is like EFI in a car, but sounds like I am wrong.  

In summary, you have had best success with T4 at 50:1?

JBoneMotorworks wrote:

Hey Lee..yes you are correct. I called Vortex, they are not making anything this yr for these new MX bikes, GET ECU is making some right...

Hey Lee..yes you are correct. I called Vortex, they are not making anything this yr for these new MX bikes, GET ECU is making some right now and should have some more info in Jan on it.

The whole race gas mix ratio pump gas thing is kinda wordy and complicated and now gets a bit more specific due to the TBI.

The reason why there are more ponies to be had with a 93 pump gas has to do with the oxygenators in pump fuel, which is a good thing. 93 has roughly 3-4% oxygen in it. This helps it burn better, (O2 is highly explosive), the down side to the current method of oxygenating pump fuel is ETHANOL. It is the current standard for O2 additive but it attracts water like a sponge and pulls moisture out of thin air and collects it like a magnet.

You think, "hey I'm going to get some VPC12 110 with no ethanol in it"..that's great it will last a long time and not gum up but you also have no oxygen in it, VPC12 is non oxy. So it will burn a bit more linear as compared to 93 and not have the "punch" behind it.
So on a dyno, you would see more hp with 93 than 110...stock motor of course. If you bump up the compression, raise the octane with it to avoid detonation.


People cut their fuel to a 50/50 to get around 99 octane or so, thats great, bc you are adding oxygen into the mix but also ethanol. I recommend treating the pump gas with an enzyme to keep the ethanol at bay OR using a direct replacement fuel with a safe octane rating for the motor that has oxygen in it.

For ex) on my 23' 125sx, I'm. running VP T4 @ 40:1. It has an oxygen factor of 5.8%, unleaded, 97 octane. So it's only about max 2% oxygen over 93..thats very acceptable for an over spec oxy factor.

The other options are to run some sort of VP engine fuel like their can that is 94 efree small engine fuel and add some Nitro X (I have done this), to get a 3-5% oxy factor back in the fuel. I did a mod motor on my 16' 150sx that I cut with 110 and 94 efree and a 5% nitro oxy and you could hear that bike across the track up a Southwick lol,,it howled and run unreal.


The ECU is a non closed loop so it will never receive information back to make changes to the fuel circuit. It's called "Feedback" The lambda protocol can do this inside the ECU's that are tunable and "learn" from the feedback to it.

A small example of feedback would be like a typical PC screen that is LED. If you touch an icon with your finger on the desktop, nothing happens..however if you have a LCD screen that has a feedback and change protocol in it, you can touch an icon and it opens up and other window. Think the touch screen thing at the ATM.
So the stocker ECU is basically programmed to send a pre-determined amount of fuel over a certain rpm range given some factors and information that it gathers from the sensors, not internal engine values.
So the air temp sensor in the air-box will send info to the ECU that says, "hey it's 39 degrees out, when you send fuel, make sure you send the right amount bc cold.
The AF monitor says, "great info, thanks" and so on.
If changes are made to the head and it is cut to bump up the compression, this will make more heat, it will burn better, and more than likely lean out bc it is more efficient but the ECU won't know this so it will just continue to pump out what it has been told to push based on the sensors, not the volumetric efficiency.
So, although I want desperately to dive into the squish and porting, if I make changes that improve the flow and efficiency of the engine, I have no way to readdress this and will cause some issues.
On a 4stroke with like a Vortex, there are fuel trim dials, make a change, it runs better and a little leaner, dial in more and you are good to go.
This one, not so much.
Sorry this is wordy but it kinda lays out why it is so important to stay with the correct premix and fuel recommended by the mfg.


Talk soon! J

8tensolutions wrote:

So I am new to understanding the TBI, but are you saying the system does not adjust other than for air temp meaning it is not...

So I am new to understanding the TBI, but are you saying the system does not adjust other than for air temp meaning it is not reading the air/fuel mixture after combustion at all and adjusting the fuel according to that?  I guess I am assuming it is like EFI in a car, but sounds like I am wrong.  

In summary, you have had best success with T4 at 50:1?

JBoneMotorworks wrote:

You are correct in that the EFI circuit is like a car where a throttle body is sending fuel, (and air), into the motor at the...

You are correct in that the EFI circuit is like a car where a throttle body is sending fuel, (and air), into the motor at the intake and the ECU talks to the sensors of the motor to determine air temp, AF, etc.  But since it doesn't have post exh sensors, (like O2 sensors), to monitor the combustion of what is being burned, it can't make any changes to the ECU to say, "hey, this bike is running bad/good/etc" so it can't push a diff fuel load.

I am pretty certain that O2 sensors and that level of feedback will never be an option at the moment, (with t2 strokes anyway), due to the amount of smoke and waste, I think the ECU would be in conflict at any RPM lol.

I think what will happen is someone will make an ECU with a low voltage output to control the PV and be able to tune it with fuel trim dials like a Vortex with a few map selections.

I think that if the stocker ECU wasn't responsible for the PV volts, there would be people working on options, but this ECU is pretty complicated so it may be a while.

I actually need to break the bike in for (1) hr, then take it to the dyno, but I haven't been able to get out there bc the seat was getting fitted for a GUTS seat cover and it is just done today.

Soon though, Im going with T4 @ 40/1...we will see!

 

8tensolutions wrote:

Thanks for the detail! The lack of O2 sensors definitely changes how it can adjust, but it has to be able to see AF for different...

Thanks for the detail! The lack of O2 sensors definitely changes how it can adjust, but it has to be able to see AF for different conditions, but you have found it cannot adjust properly for higher octane fuels etc because of the parameters internally being "tight".  Am I understanding that correctly?

8tensolutions wrote:

Thanks for the detail! The lack of O2 sensors definitely changes how it can adjust, but it has to be able to see AF for different...

Thanks for the detail! The lack of O2 sensors definitely changes how it can adjust, but it has to be able to see AF for different conditions, but you have found it cannot adjust properly for higher octane fuels etc because of the parameters internally being "tight".  Am I understanding that correctly?

731chopper wrote:

As I understand it, any EFI dirt bike has sensors to know the ambient temp, density, etc. which the ECU then uses to determine the amount...

As I understand it, any EFI dirt bike has sensors to know the ambient temp, density, etc. which the ECU then uses to determine the amount of fuel to send but none of them have a sensor post exhaust port to measure the air quality to then be able to readjust like our cars do. 
 

I thought our cars o2 sensor was more about emissions and making sure the car was in spec of environmental regulations rather than performance? Yes, I’m pretty ignorant to this stuff. I have just enough knowledge to be dangerous. 

8tensolutions wrote:

So I am new to understanding the TBI, but are you saying the system does not adjust other than for air temp meaning it is not...

So I am new to understanding the TBI, but are you saying the system does not adjust other than for air temp meaning it is not reading the air/fuel mixture after combustion at all and adjusting the fuel according to that?  I guess I am assuming it is like EFI in a car, but sounds like I am wrong.  

In summary, you have had best success with T4 at 50:1?

JBoneMotorworks wrote:

You are correct in that the EFI circuit is like a car where a throttle body is sending fuel, (and air), into the motor at the...

You are correct in that the EFI circuit is like a car where a throttle body is sending fuel, (and air), into the motor at the intake and the ECU talks to the sensors of the motor to determine air temp, AF, etc.  But since it doesn't have post exh sensors, (like O2 sensors), to monitor the combustion of what is being burned, it can't make any changes to the ECU to say, "hey, this bike is running bad/good/etc" so it can't push a diff fuel load.

I am pretty certain that O2 sensors and that level of feedback will never be an option at the moment, (with t2 strokes anyway), due to the amount of smoke and waste, I think the ECU would be in conflict at any RPM lol.

I think what will happen is someone will make an ECU with a low voltage output to control the PV and be able to tune it with fuel trim dials like a Vortex with a few map selections.

I think that if the stocker ECU wasn't responsible for the PV volts, there would be people working on options, but this ECU is pretty complicated so it may be a while.

I actually need to break the bike in for (1) hr, then take it to the dyno, but I haven't been able to get out there bc the seat was getting fitted for a GUTS seat cover and it is just done today.

Soon though, Im going with T4 @ 40/1...we will see!

 

8tensolutions wrote:

Thanks for the detail! The lack of O2 sensors definitely changes how it can adjust, but it has to be able to see AF for different...

Thanks for the detail! The lack of O2 sensors definitely changes how it can adjust, but it has to be able to see AF for different conditions, but you have found it cannot adjust properly for higher octane fuels etc because of the parameters internally being "tight".  Am I understanding that correctly?

JBoneMotorworks wrote:

You are correct in that the EFI circuit is like a car where a throttle body is sending fuel, (and air), into the motor at the...

You are correct in that the EFI circuit is like a car where a throttle body is sending fuel, (and air), into the motor at the intake and the ECU talks to the sensors of the motor to determine air temp, AF, etc.  But since it doesn't have post exh sensors, (like O2 sensors), to monitor the combustion of what is being burned, it can't make any changes to the ECU to say, "hey, this bike is running bad/good/etc" so it can't push a diff fuel load.

I am pretty certain that O2 sensors and that level of feedback will never be an option at the moment, (with t2 strokes anyway), due to the amount of smoke and waste, I think the ECU would be in conflict at any RPM lol.

I think what will happen is someone will make an ECU with a low voltage output to control the PV and be able to tune it with fuel trim dials like a Vortex with a few map selections.

I think that if the stocker ECU wasn't responsible for the PV volts, there would be people working on options, but this ECU is pretty complicated so it may be a while.

I actually need to break the bike in for (1) hr, then take it to the dyno, but I haven't been able to get out there bc the seat was getting fitted for a GUTS seat cover and it is just done today.

Soon though, Im going with T4 @ 40/1...we will see!

 

8tensolutions wrote:

Thanks for the detail! The lack of O2 sensors definitely changes how it can adjust, but it has to be able to see AF for different...

Thanks for the detail! The lack of O2 sensors definitely changes how it can adjust, but it has to be able to see AF for different conditions, but you have found it cannot adjust properly for higher octane fuels etc because of the parameters internally being "tight".  Am I understanding that correctly?

JBoneMotorworks wrote:

Basically yes, it is a non closed loop so it won't get information back and forth from internal changes that are made so its a "locked"...

Basically yes, it is a non closed loop so it won't get information back and forth from internal changes that are made so its a "locked" ECU.

I'm sure there are some tuners out there that are working on cracking it!  GET ECU and I believe AIM are working on it now from what I hear.

 

hellion wrote:

Good of you to explain a few things JBone. Too many people think race fuel makes their stock bikes faster. Ideally, you want enough octane to...

Good of you to explain a few things JBone. Too many people think race fuel makes their stock bikes faster. Ideally, you want enough octane to keep a bike from pinging/detonating and no more.

So, it sounds like there’s nothing in the FI system that would allow it to adjust for mods like a high compression head? Surely stock bikes are set to run on good pump fuel. But there must be quite a lot to be gained if you were to bump up compression and then use the fuel it calls for. Probably would need an aftermarket ignition like a vortex to make it all come together. Is there even an ignition available yet?

JBoneMotorworks wrote:

Hey Lee..yes you are correct. I called Vortex, they are not making anything this yr for these new MX bikes, GET ECU is making some right...

Hey Lee..yes you are correct. I called Vortex, they are not making anything this yr for these new MX bikes, GET ECU is making some right now and should have some more info in Jan on it.

The whole race gas mix ratio pump gas thing is kinda wordy and complicated and now gets a bit more specific due to the TBI.

The reason why there are more ponies to be had with a 93 pump gas has to do with the oxygenators in pump fuel, which is a good thing. 93 has roughly 3-4% oxygen in it. This helps it burn better, (O2 is highly explosive), the down side to the current method of oxygenating pump fuel is ETHANOL. It is the current standard for O2 additive but it attracts water like a sponge and pulls moisture out of thin air and collects it like a magnet.

You think, "hey I'm going to get some VPC12 110 with no ethanol in it"..that's great it will last a long time and not gum up but you also have no oxygen in it, VPC12 is non oxy. So it will burn a bit more linear as compared to 93 and not have the "punch" behind it.
So on a dyno, you would see more hp with 93 than 110...stock motor of course. If you bump up the compression, raise the octane with it to avoid detonation.


People cut their fuel to a 50/50 to get around 99 octane or so, thats great, bc you are adding oxygen into the mix but also ethanol. I recommend treating the pump gas with an enzyme to keep the ethanol at bay OR using a direct replacement fuel with a safe octane rating for the motor that has oxygen in it.

For ex) on my 23' 125sx, I'm. running VP T4 @ 40:1. It has an oxygen factor of 5.8%, unleaded, 97 octane. So it's only about max 2% oxygen over 93..thats very acceptable for an over spec oxy factor.

The other options are to run some sort of VP engine fuel like their can that is 94 efree small engine fuel and add some Nitro X (I have done this), to get a 3-5% oxy factor back in the fuel. I did a mod motor on my 16' 150sx that I cut with 110 and 94 efree and a 5% nitro oxy and you could hear that bike across the track up a Southwick lol,,it howled and run unreal.


The ECU is a non closed loop so it will never receive information back to make changes to the fuel circuit. It's called "Feedback" The lambda protocol can do this inside the ECU's that are tunable and "learn" from the feedback to it.

A small example of feedback would be like a typical PC screen that is LED. If you touch an icon with your finger on the desktop, nothing happens..however if you have a LCD screen that has a feedback and change protocol in it, you can touch an icon and it opens up and other window. Think the touch screen thing at the ATM.
So the stocker ECU is basically programmed to send a pre-determined amount of fuel over a certain rpm range given some factors and information that it gathers from the sensors, not internal engine values.
So the air temp sensor in the air-box will send info to the ECU that says, "hey it's 39 degrees out, when you send fuel, make sure you send the right amount bc cold.
The AF monitor says, "great info, thanks" and so on.
If changes are made to the head and it is cut to bump up the compression, this will make more heat, it will burn better, and more than likely lean out bc it is more efficient but the ECU won't know this so it will just continue to pump out what it has been told to push based on the sensors, not the volumetric efficiency.
So, although I want desperately to dive into the squish and porting, if I make changes that improve the flow and efficiency of the engine, I have no way to readdress this and will cause some issues.
On a 4stroke with like a Vortex, there are fuel trim dials, make a change, it runs better and a little leaner, dial in more and you are good to go.
This one, not so much.
Sorry this is wordy but it kinda lays out why it is so important to stay with the correct premix and fuel recommended by the mfg.


Talk soon! J

8tensolutions wrote:

So I am new to understanding the TBI, but are you saying the system does not adjust other than for air temp meaning it is not...

So I am new to understanding the TBI, but are you saying the system does not adjust other than for air temp meaning it is not reading the air/fuel mixture after combustion at all and adjusting the fuel according to that?  I guess I am assuming it is like EFI in a car, but sounds like I am wrong.  

In summary, you have had best success with T4 at 50:1?

8tensolutions wrote:

02 sensors are a massive part of tuning/performance and not emissions related, but air/fuel measured at the exhaust.  The tuning for sure impacts emissions though.  

JBoneMotorworks wrote:

Basically yes, it is a non closed loop so it won't get information back and forth from internal changes that are made so its a "locked"...

Basically yes, it is a non closed loop so it won't get information back and forth from internal changes that are made so its a "locked" ECU.

I'm sure there are some tuners out there that are working on cracking it!  GET ECU and I believe AIM are working on it now from what I hear.