2 Step Tuning

[dville_gt]

Got to go out and play with my 2 step last night. Seems to be working pretty good, found out that since the area's of the VE table I hit in the 2 step are never hit otherwise they were way out of tune (very lean).

My question is:

Since there are area's of the VE table and the timing table that I can only hit while on the 2 step (like 3.2k rpm @ 150kpa on the VE table or 1.0grms of cyl air mass @ 3.2k rpm on the timing table), how should I tune those areas.

I have heard you want to tune it rich and low timing as this helps build more boost. What kind of AFR and total timing is ideal. On a side note, can the AFR numbers on the 2 step really be trusted since you are cutting spark and still fueling or does most of that burn up in the turbine?

Thanks!

[dville_gt]

Oh, and I was able to build around 7psi @ 3.2-3.3k rpm on the foot brake @ 100%tps, should be able to jack the 2 step up a little and hopefully with some tuning get a little more boost out of it out of the hole. AFR was around 12.5:1 and timing was around 20* @ 7psi on the 2 step.

[turbostang]

the one big thing to remember is that on the 2 step, you can not go by the 02 sensor - they are WAY off 99% of the time. The engine pumps out raw oxygen as a result of the deliberate misfire. The 02 picks this up as a lean condition, when in fact it's really rich.

...another thing to keep in mind, low RPM, low load - you can't hardly hurt the engine in this operating range and long as you don't do anyting stupid.

You just have to be sure that whatever you're doing out of the normal, to make it spool at that range in your VE - it needs to be 'turned off' as soon as you dump the footbrake or the brake pedal.

[dville_gt]

Won't it turn off as soon as I let off the foot brake and flash the converter? The converter I am running flashes @ ~4500rpm, so I never see any boosted region of the VE table below that unless I am on the 2 step (or stalled on the foot brake but most I see there is 1-2psi vs. 7psi on 2 step). When I am building boost on the foot brake/2 step I am entering regions of the VE table the car cannot possibly ever see when the 2 step isn't activated. Couldn't I tune those areas of both the VE and spark table to facilitate building boost quicker without any mechanism to switch the settings back when I release the 2 step since the motor will not return to those areas of the VE or spark table?

As far as the deliberate misfire pumping oxygen, since this 2 step is only cutting spark I would imagine that the mix would read rich vs. lean. Seems like if I just take away the spark it would pump raw fuel out of that cylinder. No doubting you at all just trying to imagine "how it works".

[turbostang]

Won't it turn off as soon as I let off the foot brake and flash the converter? The converter I am running flashes @ ~4500rpm, so I never see any boosted region of the VE table below that unless I am on the 2 step (or stalled on the foot brake but most I see there is 1-2psi vs. 7psi on 2 step). When I am building boost on the foot brake/2 step I am entering regions of the VE table the car cannot possibly ever see when the 2 step isn't activated. Couldn't I tune those areas of both the VE and spark table to facilitate building boost quicker without any mechanism to switch the settings back when I release the 2 step since the motor will not return to those areas of the VE or spark table?

As far as the deliberate misfire pumping oxygen, since this 2 step is only cutting spark I would imagine that the mix would read rich vs. lean. Seems like if I just take away the spark it would pump raw fuel out of that cylinder. No doubting you at all just trying to imagine "how it works".

If you have the answers, why ask the questions?

All it takes is ONE cell to make you chase your tail, I was just saying that however you are activating your enrichment on the 2 step needs to be OFF - whether it be through some sort of activation wire or otherwise.

If the two step is only cutting spark and you are still getting fuel - what's happening to that compressed air coming from the turbo? That's right, NOTHING. The oxygen is pushed right on through instead of bieng burned WITH the fuel. The sensor picks up the higher oxygen content and not the fuel vapor.

[dville_gt]

If you have the answers, why ask the questions?

trying to imagine "how it works"

All it takes is ONE cell to make you chase your tail, I was just saying that however you are activating your enrichment on the 2 step needs to be OFF - whether it be through some sort of activation wire or otherwise.

I have no way of doing that with my current PCM

If the two step is only cutting spark and you are still getting fuel - what's happening to that compressed air coming from the turbo? That's right, NOTHING. The oxygen is pushed right on through instead of bieng burned WITH the fuel. The sensor picks up the higher oxygen content and not the fuel vapor.

That makes sense, sorry, yowza.

[turbostang]

I have no way of doing that with my current PCM



That makes sense, sorry, yowza.

I don't know what the tuning abilities of what you have or how you're doing it - so the answers have to be broad. Sam can probalby better summarize what I'm trying to convey. Long story short, it's obvious that if what ever your doing on the two step carries up into the area where it makes power will be detrimental. If you use a switch for activation, that's the safest - but may not have that option?

Sometimes you overthink things so far that the answer is RIGHT in front of you and you don't see it. Overanalytical personality will get you every time

[dville_gt]

Sam can probalby better summarize what I'm trying to convey.

He had enough of me long ago!

Sometimes you overthink things so far that the answer is RIGHT in front of you and you don't see it. Overanalytical personality will get you every time

I'll be the first to agree, I am always happier knowing the logic behind answers vs. just the answer. I understand how it drives folks like you and Sam nuts, you are both doing me a favor by simply answering the question and then I go on and want further explanations, ask you to evaluate my thought processes, etc. The only reoccurring theme that I do disagree with is the notion that both of you seem to share that I think I am the expert or have all the answers. This is simply not the case, if it sounds like I am challenging your responses it is because I am trying to figure out why my current thought process is wrong and yours is right, not the other way around.

I should probably stop asking tech questions around here, I'd like to think some other folks out there are possibly learning from these threads, but probably not.

[turbostang]

He had enough of me long ago!



I'll be the first to agree, I am always happier knowing the logic behind answers vs. just the answer. I understand how it drives folks like you and Sam nuts, you are both doing me a favor by simply answering the question and then I go on and want further explanations, ask you to evaluate my thought processes, etc. The only reoccurring theme that I do disagree with is the notion that both of you seem to share that I think I am the expert or have all the answers. This is simply not the case, if it sounds like I am challenging your responses it is because I am trying to figure out why my current thought process is wrong and yours is right, not the other way around.

I should probably stop asking tech questions around here, I'd like to think some other folks out there are possibly learning from these threads, but probably not.

I understand, I want to know logic as well - but Sam and I have been doing this stuff a LONG time, we wouldn't intentionally steer you wrong. I have no qualms about admitting to being wrong either....

LOL, people benifit from someone else asking questions is implying that DFWM uses the search function!!!!

[Magnimike1]

I understand, I want to know logic as well - but Sam and I have been doing this stuff a LONG time, we wouldn't intentionally steer you wrong. I have no qualms about admitting to being wrong either....

LOL, people benifit from someone else asking questions is implying that DFWM uses the search function!!!!

That last line is a no shit