2-Step, Alky and XFI

[NY Twin Turbo]

I jumped into a thread in the "Performance ECM Upgrades" section with some questions. But there wasn't much feedback from you guys. So I'll give it a shot here in this section.

Why do we want to totally deactivate alky when in 2-step?

When we are not using the 2-step, we build boost normally on all 6 cylinders. So the actual AF is a reflection of the combined combustion of fuel and alky. Now, assuming the tune is good in the "boost building" areas of the VE map, there should be little to no correction to the fuel. Right?

Now, when we launch the car things are different. We activate the 2-step. Now spark will randomly be cut from the sequence. Raw fuel, alky, and uncombined oxygen spills into the exhaust stream messing up all the AF readings. This is why it is typical to not allow any O2 correction in the "building boost" areas of the VE map.

So why take alky out of the mix? If the XFI is using only it's VE number to fuel the motor, and this number normally represents the presumed presents of alky, and now that alky is gone, wouldn't the cylinders that do fire be going lean during 2-step?

If the VE number was right before, then it should still be very close. And if it was close with the alky involved, and then there is no Alky, then now it's lean. No?

I know we don't normally sit on the 2-step for hours at a time. So I understand a point made about a crisper power response after disengagement of the 2-step. But doesn't that raw fuel, alky and oxygen get thrown out into the headers and then expand and burn to help spool-up?

And if washing down the cylinders is concerned, then I guess this makes sense too. But is that all there is to it?

Or should we be using a "race only" tune that has higher VE numbers in the 2-step region of the map to compensate for the absence of alky?

 

[Mr.Spool]

I jumped into a thread in the "Performance ECM Upgrades" section with some questions. But there wasn't much feedback from you guys. So I'll give it a shot here in this section.

Why do we want to totally deactivate alky when in 2-step?

When we are not using the 2-step, we build boost normally on all 6 cylinders. So the actual AF is a reflection of the combined combustion of fuel and alky. Now, assuming the tune is good in the "boost building" areas of the VE map, there should be little to no correction to the fuel. Right?

Now, when we launch the car things are different. We activate the 2-step. Now spark will randomly be cut from the sequence. Raw fuel, alky, and uncombined oxygen spills into the exhaust stream messing up all the AF readings. This is why it is typical to not allow any O2 correction in the "building boost" areas of the VE map.

So why take alky out of the mix? If the XFI is using only it's VE number to fuel the motor, and this number normally represents the presumed presents of alky, and now that alky is gone, wouldn't the cylinders that do fire be going lean during 2-step?

If the VE number was right before, then it should still be very close. And if it was close with the alky involved, and then there is no Alky, then now it's lean. No?

I know we don't normally sit on the 2-step for hours at a time. So I understand a point made about a crisper power response after disengagement of the 2-step. But doesn't that raw fuel, alky and oxygen get thrown out into the headers and then expand and burn to help spool-up?

And if washing down the cylinders is concerned, then I guess this makes sense too. But is that all there is to it?

Or should we be using a "race only" tune that has higher VE numbers in the 2-step region of the map to compensate for the absence of alky?

Some of us don't take alky out of the mixalky is a major part of my setup and I don't need to torch a cylinder.it really depends on the combo how much your displacing.i have seen cars go soft on the 60ft and 330 slower because they hit the motor too hard with the meth and really couldn't use.i have a fast one here that loves the meth just footbrake and fly.

 

[haywire4130]

I get what you're saying after some thought, you could definately tune it to be correct in the VE table since the cells for that kpa range/vs 2 step rpm would almost never be used in normal driving, except for maybe a split second since the rpms would climb lightning fast at the boost level most of us launch at.
I stand by my cylinder wash theory though, and it was easier for me to momentarilly disable alky while 2 step is active, my car rips out of the hole.

 

[Sydwyndr]

If you are using a TR6 ignition then you can add the alky system signal to it to not activate while the 2 step is active

 

[NY Twin Turbo]

I get what you're saying after some thought, you could definately tune it to be correct in the VE table since the cells for that kpa range/vs 2 step rpm would almost never be used in normal driving, except for maybe a split second since the rpms would climb lightning fast at the boost level most of us launch at.
I stand by my cylinder wash theory though, and it was easier for me to momentarilly disable alky while 2 step is active, my car rips out of the hole.

I have used the foot brake and/or trans brake to apply and hold load on every VE cell leading up to a launch. After continuous repeats and tests, and messing with the AE tables, I've got those cells pretty God damned good (with or without O2 correction and no matter how fast or slow I tip into the throttle)! I set my alky (dual nozzles) to turn on light and early and then ramp it up soft (so as not to drown the motor). I do this so I can take advantage of it more often because I normally run very low boost on the street. Having it this way means alky plays a big part in the fueling at a very early point in spool up (about 3 PSI).

So, when I started seeing posts made by others giving advise on turning off the alky, I thought I was missing out on some big secret.

 

[NY Twin Turbo]

Some of us don't take alky out of the mixalky is a major part of my setup and I don't need to torch a cylinder.it really depends on the combo how much your displacing.i have seen cars go soft on the 60ft and 330 slower because they hit the motor too hard with the meth and really couldn't use.i have a fast one here that loves the meth just footbrake and fly.

This is good to know.

Thank you very much. See above comments.

 

[NY Twin Turbo]

If you are using a TR6 ignition then you can add the alky system signal to it to not activate while the 2 step is active

Yes. But why?

Any more theories on how this is beneficial are greatly appreciated.

 

[Sydwyndr]

When the car comes off the 2 step generally the air fuel ratio is a lot richer than normal which will cause possible issues with how quick the turbo comes up and how quick the car reacts

 

[NY Twin Turbo]

When the car comes off the 2 step generally the air fuel ratio is a lot richer than normal which will cause possible issues with how quick the turbo comes up and how quick the car reacts

So your saying that it's a false richness left over from the 2-step?

And then after the launch, When you enter the cells you allow correction in, this will immediately and incorrectly tell the XFI to pull fuel out, thus causing the motor to go lean?

 

[Sydwyndr]

After a few runs you can tune the VE where it needs to be instead of a wild swing from lean to rich.....

 

[Mr.Spool]

I have used the foot brake and/or trans brake to apply and hold load on every VE cell leading up to a launch. After continuous repeats and tests, and messing with the AE tables, I've got those cells pretty God damned good (with or without O2 correction and no matter how fast or slow I tip into the throttle)! I set my alky (dual nozzles) to turn on light and early and then ramp it up soft (so as not to drown the motor). I do this so I can take advantage of it more often because I normally run very low boost on the street. Having it this way means alky plays a big part in the fueling at a very early point in spool up (about 3 PSI).

So, when I started seeing posts made by others giving advise on turning off the alky, I thought I was missing out on some big secret.

So you adjusted the alky curve but the pump pressure dictates how big of a fuel roll the alky is playing.getting the light to turn on is a matter of 40psi of less depending on where you put the controls.i have used these kits for a long time and moved many curves.guys leaving on high boost with an aggressive alky curve could be into the 100psi area and in a eye blink at max psi.if the engine can use it it won't be problem but if it can't It can create a lazy rpm and turbo climb.i have logged egts and seen a loss of power when overspraying.

 

[Mr.Spool]

Yes. But why?

Any more theories on how this is beneficial are greatly appreciated.

The wideband if pretty far from the action and only looking at the Afr from all the cylinders not individually.

 

[king kong]

Good Stuff ..... Thanks Guys !