[jwa999]

Ever since I got the car, i noticed the inside of the tailpipes are always covered in black soot. I've never seen a car emit so much of it. Must be running pretty rich.
So it was a pleasant surprise today that I could still see the inside of the tailpipe after I washed the car this morning and drove it for around 30 miles. Usually they are completely black after the 15 mile trip from home to work. The inside of the tips are gorgeous, but nobody ever gets a chance to see it.

I get the impression my MPG is better, except that the tune makes the car wanna go even more :thumbsup:

Hans.

 

[verbs]

Richer tune = more soot. Leaner tune (w4m) = less soot

 

[Short-Throw]

I get the impression my MPG is better, except that the tune makes the car wanna go even more :thumbsup:

Hans.

They are made rich to protect the catalyst. If you start to hear exhaust rattle noises (from the catalyst bricks melting down) - you'll know why.

As far as MPG being better, I'll believe it when I see it. I just don't see this being possible.


Mike

 

[FreddyG]

They are made rich to protect the catalyst. If you start to hear exhaust rattle noises (from the catalyst bricks melting down) - you'll know why.

As far as MPG being better, I'll believe it when I see it. I just don't see this being possible.


Mike

Can I ask why you don't think that it could get better?

An engine is nothing more than a glorified air pump and if you tune it to use the fuel more efficiently, wouldn't that mean the mileage goes up?

Just asking, because it makes sense in my little mind! :cheers:

 

[GMX322V S/C]

They are made rich to protect the catalyst...

Mike, do you mean by guarding against misfires (which would dump raw gas into the exhaust)? Cats run hotter the more unspent fuel you throw at them; running them leaner gives them "less to work with," so if anything, they should run cooler...

 

[GMX322V S/C]

Found this in the tuning section over at LS1Tech (topic had to do with Predator handheld):

"COT Protection Off Road use only!
Catalytic Overtemp Protection (COT) is used to add fuel to cool down the catalytic converters and it should be disabled only when the catalytic converters are removed."

Another post in the same forum said the enrichment comes at WOT. Wow, learn something new every day...

 

[jwa999]

Here's some interesting reading:

http://en.wikipedia.org/wiki/Fuel_mixture

http://en.wikipedia.org/wiki/Catalytic_converter

It's counter intuitive, but a leaner mix burns hotter:

"A stoichiometric mixture has just enough air to completely burn the available fuel."
"A stoichiometric mixture unfortunately burns very hot and can damage engine components if the engine is placed under high load at this fuel air mixture."
"As a consequence stoichiometric mixtures are only used under light load conditions. For acceleration and high load conditions, a richer mixture (lower air-fuel ratio) is used to produce cooler combustion products and thereby prevent detonation and overheating of the cylinder head."

From what I read on the Catalyst, It looks like it needs a richer mixture to be able to convert the NOx, but too rich a mixture can cause a meltdown.

"When there is more oxygen than required, then the system is said to be running lean, and the system is in oxidizing condition. In that case, the converter's two oxidizing reactions (oxidation of CO and hydrocarbons) are favoured, at the expense of the reducing reaction. When there is excessive fuel, then the engine is running rich. The reduction of NOx is favoured, at the expense of CO and HC oxidation."

"Some newer systems do not employ air injection. Instead, they provide a constantly varying mixture that quickly and continually cycles between lean and rich to keep the first catalyst (NOx reduction) from becoming oxygen loaded, and to keep the second catalyst (CO oxidization) sufficiently oxygen-saturated. They also utilize several oxygen sensors to monitor the exhaust, at least one before the catalytic converter for each bank of cylinders, and one after the converter. Some systems contain the reduction and oxidation functions separately rather than in a common housing."

So I wonder what the w4m tune effect is on Engine/exhaust temps and Catalyst efficiency.

Hans.

 

[GMX322V S/C]

That is interesting, Hans. I knew running lean could burn valves and hole pistons, but everything I read about cat failure pretty much said the cat would simply become ineffective. Maybe there's a delicate ballet going on--extremely rich conditions can lead to catastrophic failure, while too lean of a condition can cause more long-term stress?

Anyway, I can confirm your observation of less soot buildup inside the tips with the tune in place.

 

[Cadillac Tony]

Back in my RX8 days there were tons of problems with the early cars flooding due to the catalyst protection. They ran the car pig rich to keep the EGTs low and not fry the cats, but people who'd start the car and then shut it off without running it for 15 minutes had a flooded engine on their hands. Even if you didn't flood the car, the tips were still black as midnight after a day or two of driving.

Later PCM calibrations that Mazda released to fix the flooding problem also greatly reduced the soot buildup on the pipes and increased average MPG, so I'd agree with your assessment of less soot and better MPG being a result of the w4me tune.

 

[Short-Throw]

Can I ask why you don't think that it could get better?

An engine is nothing more than a glorified air pump and if you tune it to use the fuel more efficiently, wouldn't that mean the mileage goes up?

Just asking, because it makes sense in my little mind! :cheers:

Let's try to keep this simple.

First of all, so nobody gets the wrong idea, I think modding cars is fun and as long as the owner doesn't mind spending his dime and accept warranty denial, I say mod away.

The problem is for anybody to buy a given mod there has to be reasons to spend the dough. The truth is most minor cheap mods do not yield anything worthwhile. This in turn has shops disseminating unsupported claims.

Now:

As far as better fuel economy, here is why I have doubts:


Please tell me what has been done to fundamentally change the operating efficiency of the engine?

What A/F ratio is being employed under cruise control conditions?

Are there any hardware changes that affect pumping losses?

3rd party unbiased testing would be a breath of fresh air, but hard to find.

As enthusiasts, we all want better and faster and we are just too willing to believe everything we hear.

When I was building my race car I inquired about how much HP it would yield on the Chassis dyno (vs an engine dyno) from the head tech. He responded by saying, "What ever you want it to be".

I'm happy to post my 30 MPG, 1200HP factory freak bone stock CTS-V dyno sheet any time!



Mike

 

[wait4me]

All im doing it just fixing the 10.0 i see on tip in that the factory tune was doing. 10 is WAY to rich for any car/situation. Well gasoline anyways, E85 is obviously different. I am not changing stioch points or any normal mode operation other than that tip in issue. I move the tip in to 13s. that is why it feels better. The coeficients are not quiet set right from the factory. I just tweek them to make them exact. I dont touch any of the cat over temp protection algorithms, Which add fuel at wot when they get hot. So the car will still command the same value at wot if it needs to.. These motors are not new technology by any means, nor are cats. I have cars with 150,000 miles on them that i tuned the same exact ways..

 

[Formula57]

All im doing it just fixing the 10.0 i see on tip...

What is "tip?"

 

[GMX322V S/C]

Throttle tip-in; opening the throttle from the fully closed position.

 

[wait4me]

Correct. Throttle tip in is opening the throttle blade from a steady state. The E67 controller uses a MAF/ coefficient blend for fuel transistions. If the airflow and throttle % are steady then the controller uses the MAF more as it is considered the stable at that point. A maf can not see a pressure drop so the computer relies on map sensor and TPS to determine if it is valid.

On a tip in, there is a pressure drop and the ecm will then use a Blend of Calculated Ve and actual maf frequency. All works well when you have the Ve and maf close. The ecm will setup coefient Zones for the amount of ERROR it has between actual o2 sensor feedback and Maf and Ve values to set itself up for a 14.7 on steady state. This is an awsome system but has to be matching in order for it to always be correct.

Since the new e38 and e67 engine controllers dont have a real Ve table for say, They are alot harder to fine tune like the older P59 or earlier ls1 based engine controllers.

The e67 for example has 30 zones. So the computer uses those zones as a reference. They are user defined with RPM and engine KPA.

1000
1750
2500
3250

Are the rpm break points, and the kpa break points are :
30.000000 45.000000 60.000000 75.000000 90.000000
30.000000 47.000000 64.000000 81.000000 98.000000
30.000000 50.000000 70.000000 90.000000 110.000000
30.000000 52.000000 74.000000 96.000000 118.000000
30.000000 54.000000 78.000000 100.000000 124.000000


That makes a table plot for the values on where you know where to make your changes..

Now where the math comes in. To calculate Ve tables on the values on coeficents are a pain without the right tools or software.. Once you know where you want to be fixing your "virtual" ve zone you have to pin point the zone based on the values in the Bin file. Then you have to make your changes and then re calculate the values and then put them in the right spot. I set up a pid to automatically do this for efilive software if people here want it. It basically takes input from a serial output 5 gas analizer and ltrims and just builds a whole new table.. The more you drive the better it makes the car drive. It just makes it smoother, more accurate, and more exact when the ecm trys to command an exact AFR, it is ALOT closer to its targer air fuel ratio. So when you command an 11.4, it goes right to 11.4...

 

[GMX322V S/C]

Thanks for the correction Jesse --so without your tune, every time we'd crack the throttle after holding it steady we'd be sending a puff of enriched exhaust into the cats? Is this where the soot came from (unburned stuff actually gets past the cats)?

 

[rjoffe]

Can you guys comment on why after market tuning on a stock setup is required ? I'm not questioning the results, and completely understand the tune requirements if any mods are made. Just curious why the factory stock setup seems to be so far off of "ideal"

Thanks,

Ron

 

[jwa999]

This went into my reasoning to get the w4m tune. I've never modded or tuned any of my cars before. They all seemed to work fine from the factory. And i've always driven stick shifts.

The caddy's automatic transmission to me was very slugish. I compared it to my wife's M45, which always seems to be in the right gear.
I absolutely couldn't not go through a fast corner and have enough engine braking going in and power going out. So I ended up always using the paddle shifters.
Jesse's w4m tune gives me more power at lower rpms and a much more responsive transmission. In every day driving (and i'm an aggressive driving when i'm alone) and i'm now having a blast keeping it in sport auto. The transmission shifts very smoothly and predictably. It gives me much more confidence going through a high speed corner and knowing that a downshift won't jerk me around. I can feel the Performance Algorithm Shifting really kicking in coming out of a corner. And there's just loads more power available.

The w4m tune is cheap. $400 spend on a $70,000 car is pittens. He should be charging more!

The tune is completely reversible. Go to the dealer or have it's annual inspection it goes back to stock.

No hardware modifications required.

Jesse from w4m seems to be very knowledgeable, he owns the car himself and had a few months to fiddle with it. I much preferred that than going to a local tune shop where they see the car for the first time.

One of the factory engineers mentioned that they "left a lot on the table" for the v2, unlike the ZR1 which was a much more accurate tune.

So, especially if you have an automatic transmission I can highly recommend it. It's easy to install and you will immediately feel the difference.

Hans.

 

[jvp]

One of the factory engineers mentioned that they "left a lot on the table" for the v2, unlike the ZR1 which was a much more accurate tune.

I'm not sure which "factory engineer" you spoke with, but it's simply not the case. The factory fuel parameters were, in part, tuned by a very good friend of mine, whom I've been speaking with behind the scenes about this subject. I'm not at liberty to say who he is or what he's been saying exactly. But, his comments are not particularly positive regarding what Jesse is doing with the tune.

If folks are happy with their tunes and feel safe that the engine is doing what it should, then by all means go for it and enjoy. But, you ARE risking issues with your engine by messing with the fuel parameters, even if Jesse claims otherwise. And, his claim about being undetectable is patently false. If GM wants to find it, they'll find it. As long as you understand those two points, you'll be fine.

jas

 

[NormV]

Why so many zones? Do they accommodate the different fuel pressures better?

Norm

 

[The Tony Show]

Can you guys comment on why after market tuning on a stock setup is required ? I'm not questioning the results, and completely understand the tune requirements if any mods are made. Just curious why the factory stock setup seems to be so far off of "ideal"

Thanks,

Ron

Liability and controlling warranty costs. Practically every mass produced car built today (especially high performance models) needs a built-in "safety net" to keep idiots from destroying the car and running GM's warranty cost through the roof.

It's hard for real "car nuts" like us to believe, but there's plenty of people out there who are going to buy a car like this and then throw cheap gas in it, let the air filter get dirty, not change the oil regularly and generally abuse the car. Also, the engineers have to try and plan for every extreme situation (like a guy sitting in bumper to bumper traffic for an hour and heat soaking the engine, then seeing daylight and flooring it), so they build in a certain amount of "cushion" to reduce the likelihood of part failures.

If you're willing to be fastidious about your service, only use the best gas, and be smart about not flooring the car if the oil's cold or the engine is heatsoaked, aftermarket tunes can pull back some of that cushion and let you enjoy more of what the car is capable of.