[gtfoxy]

Originally Posted by cmitchell17

I agree, but stoich is the optimal tradeoff between emissions and fuel economy given you have a three way catalyst.

My understanding is that you enrich for more power since that extra little fuel you give it is just to ensure that you use up all your available oxygen in your charge before it goes out the exhaust, it would seem like this factor would be more important as rpm goes up, you would also think timing would be dependent upon rpm as well, needing more timing as rpm goes up, but I'm not sure that's the case looking at stock timing tables and from what I've read. Timing is more directly dependent on cylinder pressures.

Starting inverse, ignition advance has absolutely nothing to do with RPM, aside from a decreasing dwell time as RPM rises, instead it’s a direct correlation to other dynamic conditions.

I asked you to ponder ignition advance timing in regard to pumping losses in a cyclical system, which you seem to not have done, so I ask again; Why is ignition advance, always BTDC, when considering your swing set scenario ? How would a swing be if connected to other swings where when on a returning pass, free from other forces, respond if a connecting swing be forced upon by a building counter force? Newton’s first laws of thermodynamics apply here. Every action & all that.

Now consider varying fuel types & the fact Petrol fuels vs Ethanol fuels make max power with lesser timing BTDC, considering aforementioned pumping losses, why might that be? Granted it makes more power but why? Do vaporization, meaning latent heat value, play a role here? Why?

You intrinsically touch on something, “cylinder pressure”. What does that mean?

Is it static or dynamic?

A better question is “Is timing based on something solely different such as compression (which is dynamic), vaporization, distribution, homogenization of the A/F mixture, & flame propagation rate?”

Look into latent heat value of Ethanol blends vs Petrol blends & correlating flame propagation rates. Even look into energy density/Kg. Then look at piston acceleration rates vs RPM, as a comparison to BSFC & ponder why are Ethanol blends the go-to for more power.

Now for your other catch, why do you need more fuel, beyond stoich, to mix “extra” fuel with O2?

Is there really “extra” given so much reliance on the MAF & its correspondent tables & metering or is there something else going on in the chamber in relation to hogonization & distribution?

I remember a paper written some time ago on DSI (GDI whatever) engines espousing stratification, which I get, but it was largely a misnomer as stratifcation is a chemical process where, in this instance, gaseous bonds, meaning CO to CO2, as an example, are a function of said distribution, homogenization(i.e. Proximity) of various vapor gaseous & atmospheric components interact in a tiered enthalpic condition.

Fuel for thought.

& no, stoich is stoich. That means X +Y= W+Z. The rest outside of mathematics is real world error. Gas mix ratios, meaning mathematical CO2/ H2O ideals are indeed a hypothetical, but a mathematically supported hypothetical. The rest is misleading bull shit. Emissions, i.e gas mix ratios, are the result of a stoich burn, as is maximum BSFC, but that is a function of an entropic system, which is never perfect.

You’re on the right track, you just need to look at it from a different perspective.

[6spdhyperblue]

I wonder what setting dynamic to disable would make it do

[cmitchell17]

Originally Posted by gtfoxy

Starting inverse, ignition advance has absolutely nothing to do with RPM, aside from a decreasing dwell time as RPM rises, instead it’s a direct correlation to other dynamic conditions.

I asked you to ponder ignition advance timing in regard to pumping losses in a cyclical system, which you seem to not have done, so I ask again; Why is ignition advance, always BTDC, when considering your swing set scenario ? How would a swing be if connected to other swings where when on a returning pass, free from other forces, respond if a connecting swing be forced upon by a building counter force? Newton’s first laws of thermodynamics apply here. Every action & all that.

Now consider varying fuel types & the fact Petrol fuels vs Ethanol fuels make max power with lesser timing BTDC, considering aforementioned pumping losses, why might that be? Granted it makes more power but why? Do vaporization, meaning latent heat value, play a role here? Why?

You intrinsically touch on something, “cylinder pressure”. What does that mean?

Is it static or dynamic?

A better question is “Is timing based on something solely different such as compression (which is dynamic), vaporization, distribution, homogenization of the A/F mixture, & flame propagation rate?”

Look into latent heat value of Ethanol blends vs Petrol blends & correlating flame propagation rates. Even look into energy density/Kg. Then look at piston acceleration rates vs RPM, as a comparison to BSFC & ponder why are Ethanol blends the go-to for more power.

Now for your other catch, why do you need more fuel, beyond stoich, to mix “extra” fuel with O2?

Is there really “extra” given so much reliance on the MAF & its correspondent tables & metering or is there something else going on in the chamber in relation to hogonization & distribution?

I remember a paper written some time ago on DSI (GDI whatever) engines espousing stratification, which I get, but it was largely a misnomer as stratifcation is a chemical process where, in this instance, gaseous bonds, meaning CO to CO2, as an example, are a function of said distribution, homogenization(i.e. Proximity) of various vapor gaseous & atmospheric components interact in a tiered enthalpic condition.

Fuel for thought.

& no, stoich is stoich. That means X +Y= W+Z. The rest outside of mathematics is real world error. Gas mix ratios, meaning mathematical CO2/ H2O ideals are indeed a hypothetical, but a mathematically supported hypothetical. The rest is misleading bull shit. Emissions, i.e gas mix ratios, are the result of a stoich burn, as is maximum BSFC, but that is a function of an entropic system, which is never perfect.

You’re on the right track, you just need to look at it from a different perspective.

I guess the thing is, even knowing all that the OEM's don't try to come up with a completely analytical solution to the calibration. But they do have millions worth of equipment and engine dynos to empirically come up with it, I think they start off building single cylinder engines for testing then scale up. Even though they are starting to use more CFD and computational stuff but not exclusively.

That being said they developed tables in the tune (which is the same for any LT1, Corvette, Camaro, GMPP, etc) such as the MBT table, which I believe the virtual torque tables reference to decide if current timing is this much away from this MBT table, there is this much loss in torque. I know a lot of people don't like to look at these tables and think they are meaningless, but I think they reflect exactly what timing we should be trying to achieve. Of course when we deviate with different combustion chamber, compression, it changes. I would think it could change too with significantly bigger cams too.

I know I said all that but I haven't even taken the time to try to back solve the torque coefficients and try to repopulate a high octane timing table off it (there is only so much resolution in the MBT table and i'm not sure I want to even try back solving the VT coefficients haha) But just eyeballing the table at peak HP and .88 gpc, its at 24 degrees, there is also an alcohol modifier though so at E80, you pull back out 9 degrees of timing so you're now at 15 degrees at WOT, which way conflicts with everyone else wanting to run 30 degrees of timing just because with ethanol.

[cmitchell17]

Originally Posted by 6spdhyperblue

I wonder what setting dynamic to disable would make it do

Which setting are you talking about?

[6spdhyperblue]

airflow -> dynamic air -> high rpm -> they set it to disable above 400rpm and re-enable 300rpm

[cmitchell17]

Originally Posted by 6spdhyperblue

airflow -> dynamic air -> high rpm -> they set it to disable above 400rpm and re-enable 300rpm

I thought this was to tell it to ignore speed density factors when determining the air per cylinder number? Most stock calibrations are set to ignore at 4000 rpms do to the superior accuracy of the MAF over speed density at high rpms.

[6spdhyperblue]

Yeah that’s true. Just wondering if you tried it. It doesn’t make sense but if GM did it, figured it was worth trying

[cmitchell17]

Originally Posted by 6spdhyperblue

Yeah that’s true. Just wondering if you tried it. It doesn’t make sense but if GM did it, figured it was worth trying

I have done it before yes when re calibrating the MAF based on wideband feedback. I used that table, its very weird though you would think if you just installed your cam on an un-tuned tune if you turned high rpm disable to 400 rpms then you would start running a lot better and not cutting out and dying since your motor can now run based off only feedback from the MAF sensor versus erroneous and invalid feedback from speed density using a uncalibrated VVE table.

Anyway I think the only difference it makes is how it calculates that final airflow value and weather or not it uses speed density. I am going to try it again though just to see if I notice a difference, because like you said if GM did it, its got to make a difference although we have seen them do a lot more dumb things that don't make sense.

I am in the process of moving more of my tables back to the way I had them or back to stock after trying to use the GMPP tune setup. However, I still have there main high octane spark table and there PE table. I know everyone is freaking out about there PE enrichment being at 1.08 which if you are running E10 is about 13 AFR and 13.5 AFR if you are running non ethanol fuel.

I've run my motor at WOT in closed loop at stoich before. I know everyone freaks out and says not to do this ever, but I believe there is a difference in doing in for a few seconds versus running it like that for minuets or hours. I did this so I could see how the factory system trimmed fuel so I could use it for feedback to correct VVE.

I personally think the 1.08 PE EQ Ratio GMPP chose is good, I think this is where they found peak power at so I am going to run it. Basically I took the difference from the LT535 tune and the stock LT1 crate tune and used that difference to add it to my stock PE EQ ratio for alcohol (since I usually only run E85) which I actually took the stock PE EQ ratio table from a 5.3 flex fuel truck tune. It still ends up coming out at about 1.08-1.09 through the rpm range.

[MrChrisLS3]

To begin, my tuning knowledge isn't great.

But going back to page one there are a few things that struck me about this set up.

First, running a relatively high overlap cam with stock exhaust. The main reason for the overlap is to use the vacuum created by the escaping combustion gases to pull fresh air into the cylinder. The stock system, while not bad for a factory set up, will still restrict the velocity of the exhaust gases, thus reduce 'pull' that the overlap is intended to produce. You need to let the exhaust escape quickly to get the overlap effect to it's fullest.

The other thing that struck me was the post that showed the catalytic converter being cracked. There is no way to get reliable data from that o2 sensor at that point. So, trying to tune to the enth degree with a failing cat is like herding cats (the pet kind)

I would start with the old school physics. The whole idea of a larger cam with more overlap is to get more air in faster. Fix the exhaust restriction and the catalytic converter issue, then go in for your fine tuning.

[cmitchell17]

Originally Posted by MrChrisLS3

To begin, my tuning knowledge isn't great.

But going back to page one there are a few things that struck me about this set up.

First, running a relatively high overlap cam with stock exhaust. The main reason for the overlap is to use the vacuum created by the escaping combustion gases to pull fresh air into the cylinder. The stock system, while not bad for a factory set up, will still restrict the velocity of the exhaust gases, thus reduce 'pull' that the overlap is intended to produce. You need to let the exhaust escape quickly to get the overlap effect to it's fullest.

The other thing that struck me was the post that showed the catalytic converter being cracked. There is no way to get reliable data from that o2 sensor at that point. So, trying to tune to the enth degree with a failing cat is like herding cats (the pet kind)

I would start with the old school physics. The whole idea of a larger cam with more overlap is to get more air in faster. Fix the exhaust restriction and the catalytic converter issue, then go in for your fine tuning.

So I always thought that for velocity you want the smallest diameter you can get that still optimizes overall restriction? I would assume the majority of the stock exhaust diameter (except for the restrictions where in necks down in some places that probably have minimal effect on the overall system) is sized to be optimized for 455 hp?

Also I am not sure what cracked the primary cat, but you are thinking that one small crack negates its efficiency? And thats why it probably throws a code? Which makes very good sense since its only throwing the code for bank 1 which is the drivers side which is the side I dropped the socket in which is the side in the picture. That being said hopefully if I completely delete the primaries maybe the smell won't get much worse than it is now. Problem is now I have a permanent code stored for catalyst inefficiency on that bank and I don't think anyone has found a way around getting permanent codes to go away, thats why you always have to tune the codes out before installing the hard parts.

Also how would this effect the fuel feedback (sensor 1) O2 if it is located before any cat at all?

I am going to try ordering the Bullet delete pipes, but for some reason they have the only shipping option as 2 day air and its $150?

Ok I now see why shipping is so much, they are coming from Kuwait haha explains why they are the only ones able to make them anymore.

[MrChrisLS3]

Originally Posted by cmitchell17

So I always thought that for velocity you want the smallest diameter you can get that still optimizes overall restriction? I would assume the majority of the stock exhaust diameter (except for the restrictions where in necks down in some places that probably have minimal effect on the overall system) is sized to be optimized for 455 hp?

Also I am not sure what cracked the primary cat, but you are thinking that one small crack negates its efficiency? And thats why it probably throws a code? Which makes very good sense since its only throwing the code for bank 1 which is the drivers side which is the side I dropped the socket in which is the side in the picture. That being said hopefully if I completely delete the primaries maybe the smell won't get much worse than it is now. Problem is now I have a permanent code stored for catalyst inefficiency on that bank and I don't think anyone has found a way around getting permanent codes to go away, thats why you always have to tune the codes out before installing the hard parts.

Also how would this effect the fuel feedback (sensor 1) O2 if it is located before any cat at all?

I am going to try ordering the Bullet delete pipes, but for some reason they have the only shipping option as 2 day air and its $150?

Ok I now see why shipping is so much, they are coming from Kuwait haha explains why they are the only ones able to make them anymore.

This is a really good read on exhaust systems and how they effect air flow, cylinder pressures, etc.

http://www.epi-eng.com/piston_engine...technology.htm

One thing to keep in mind, is that while wanting to achieve a certain power level, one of the main factors that manufacturers have to achieve is emission control. The factory system wants to hold those gasses going into the converters to burn up as much Co2 as possible. The camshaft, timing, fuel trims are all coordinated to meet this balance of performance and emission efficiency, but it is a compromise, none the less.

By putting in a bigger cam with more overlap and keeping the stock system, you are asking that system to handle even more exhaust gas. You're creating more back pressure in the system, which is reducing the desired effect of the overlap. the intake wants to bring in more air, but there's no room for it.
This also effects the velocity of which you speak. While pinching a garden hose creates more velocity, it doesn't create more volume. Yes, the water shoots farther, but it doesn't shoot more water.

As you will read in the article, what you want is a vacuum in the exhaust manifold when that valve opens, this creates a rush of escaping gasses. With a properly timed overlap, that rush of exhaust going out, creates a rush of intake air coming in, that is your velocity.

The article gets even deeper when starts to talk about exhaust tuning, which is what some people mistakenly refer to as 'good back pressure'. Check it out, if you want to maximize that cam to the enth degree, this is where it's at, on both the exhaust and intake side.

[cmitchell17]

So I finally got my cat delete pipes in. When I took off my stock cat pipes I found that my drivers side inside honeycomb completely gone haha, so I am assuming this stuff will blow out and not get clogged anywhere? I looked in the drivers side secondary cat pipe and everything looked normal on that cat and I didn't see any clogs.

After driving it around I have to honestly say it sounds like complete crap now. It sounds like a straight pipe kids truck. It is extremely raspy now which you can very easily notice it in the cab now, I kind of felt the stock NPP was a little too loud, especially in sport or track at WOT, at part throttle the tone and sound is excellent. However, now it is 1000 times worse.

The other unfortunate part of this is I have not been able to discern any increase in airflow while accounting for atmospheric conditions. Needless to say, these delete pipes will probably be coming off as soon as I can get them off. So is anyone interested to trade a set of stock cat pipes for these? I paid $363 + a very unreasonable $150 shipping since they come from Kuwait. Would anyone be willing to trade their stock cats for the cat delete pipes?

My plan is to gut the inside of my passenger side cat and put the stock pipes with gutted insides back on. My hope and theory is that the stock pipes have this inside double wall, which I am hoping is what is able to quiet them down and take some of the rasp out. Since my drivers side cat was completely blown and gutted out, and I didn't notice obnoxious and loud sound from that hopefully this will work and still eliminate the cat honeycomb that is supposedly very restrictive.

[cmitchell17]

So I "gutted" my other passenger side cat and tried to save the material out of it. I couldn't get some of the interior foam that holds the honeycomb completely out. I put the stock pipes back on with both gutted cats. So I am really surprised it worked, I believe I am now back to stock exhaust sound level with stock rasp level. It is a very very noticeable difference between the cat delete pipes and stock pipes, not sure if its the double wall or the material or what.

I did notice at first it seemed kind of muffled almost like it was clogged, the only thing I could think of that could have happened was that some of the fiberglass insulation looking stuff, that I believe is what holds the ceramic honeycomb in place and maybe insulates it, blew into the second cat and maybe got clogged up in it. What doesn't make sense is why didn't my drivers side cat that completely blew out when I didn't notice, why did this have no effect or clog anything where I would notice?

So good news is now I got rid of the primary cat that is supposedly very restrictive, and I have stock look from the underside and no loud raspyness that you get with delete pipes.

Bad news is I see no noticeable difference in airflow or airmass or acceleration (I don't have a dyno to compare) between stock pipes with cats, stock pipes without cats, and cat delete pipes.

[BlueinTN]

Originally Posted by cmitchell17

Thanks for the feedback.

So "cylinder airmass" or "airmass per cylinder" has actual been called a few different things over the years between GEN III, IV, and V so its a little confusing. But basically it is supposedly the PCM "final say" on what it believes the true mass of air in the cylinder to be at that exact moment in time. My fuel trims from tuning myself are also within 5% and only about +/- 3% at idle, but I imagine at idle its difficult for the O2 feedback to work correctly given the high overlap cam.

I have to bump my idle speed up past 950rpm to get rid of the stumble and surge, but I kind of would rather live with the bad smell and vibration than have the car sound like its even more broken.

The cam card TSP gives doesn't include advertised duration, only duration @ .050.

Unfortunately I never got it dynoed and also never had a dyno of it stock.

I forgot to mention I am at 1000 ft above sea level and I notice a difference in baro of about .5 psi driving back to Florida.

I read a few of your post and I know what you want.



A really good tuner can get that cam to work. A good friend of mine went thru what your doing tuning his Challenger with a cam from hell. Him tuning himsself never got it to idle below 1000 rpm. he really worked at it.



He finally went to a tuner and I think it was at least 30 revisions but they got it. 650/700 RPM and dead steady idle AC on etc. You can do it with these new style fuel injection controls. His car doesnt have a MAF but they can calculate the air column going thru the motor at idle and get it to work. Wild guess I dont think they look at AF at idle.