What is a tune?

[PeterG]

A tune, along with some after-market parts, sounded like a relatively inexpensive and step-by-step method to enhance my C6's performance. But I needed to enhance my knowledge beyond the C3s that I had rebuilt some few decades ago. I wanted learn what a tune is before allowing anyone to change components and electronic parameters in my C6.

I read Greg Banish's book, "Engine Management: Advanced Tuning".

After reading and re-reading some sections, I learned what and how many factors combine, interact, and impact performance and longevity. I learned that many specific changes should be applied based upon my C6's mechanical and electronic capabilities and how and where I plan to drive.

A tune may be the way to go, but it can involve changing aspects in ways that I failed to understand and didn't know about. I realized that I did not want some mechanical and electronic parameters changed in ways intrinsic to a tune.

I now see why a good tune can only be designed by someone whose experience and knowledge combine to mix all factors precisely and correctly. A tune can be productive or destructive.

[NORTY]

The C6 is a complex vehicle. Think of a "performance tune" as a spider web. A person changing one thing will likely effect numerous other things. In a web, one cannot touch one thread without effecting some/most/all the other threads. This is usually where tuners get in trouble.
The C6 factory tune is very rich (safe) from Bowling Green. This keeps it running cooler.
Tuners will "lean out" the A/F ratio to make the engine produce more power. It also creates MORE HEAT. During Feb./Mar it's not that big of deal. Come Jul/Aug, the cooling system can become overwelmed as the "overheat threshold" will be closer since the combustion temperatures will be higher.
Most tuners only change the tune based on WFO settings, so just cruising around might not change much. Throttle "snap" won't change much. (I thought it would, but it didn't.)

A tune will nullify your powertrain warranty. Are you still under warranty?

[Hib Halverson]

(snip).
The C6 factory tune is very rich (safe) from Bowling Green.

(snip)

I'm curious as to information on which you base the above statement. Can you post some wide-band 02 data to support it?

[NORTY]

(snip)

I'm curious as to information on which you base the above statement. Can you post some wide-band 02 data to support it?

All I have is dyno sniffer A/F ratios. Granted, they aren't super accurate @ the tail pipe, but it's better than nothing. My stock A/F ratios varied from 13.17: 1 (idle) to a range from 11.86:1 to 11.01:1 with RPM changes from 2200 to 7100. All measurements taken @ WFO (except the "idle" measurement.)
I can post up the sheet, Hib, but I'm not sure this is what you're looking for.

[Hib Halverson]

Ok.
It's just a difference in opinion on the meaning of "very rich".

At 11.0-11.86, IMO, it's not "very rich". Indeed, you're better off with the WOT AFR at 12-12.5 but GM calibrates a little rich as a detonation hedge and for cat durability.

Living out west, because we have no 93-94-oct gas, you might be better off a little rich because you may see less knock retard.

GM calibrates for 93-oct fuel. Since, out west, all we have is 91, unless the weather is really cool or your up high, you'll see detonation in WOT operation.

[NORTY]

Ok.
It's just a difference in opinion on the meaning of "very rich".

At 11.0-11.86, IMO, it's not "very rich". Indeed, you're better off with the WOT AFR at 12-12.5 but GM calibrates a little rich as a detonation hedge and for cat durability.

Living out west, because we have no 93-94-oct gas, you might be better off a little rich because you may see less knock retard.

GM calibrates for 93-oct fuel. Since, out west, all we have is 91, unless the weather is really cool or your up high, you'll see detonation in WOT operation.

Fair enough, Hib. Just for reference: The ZR1 is factory tuned for 10.7:1 @ WFO. This is even "richer."

I agree with you about 12-12.5 being better for power, but GM has many regulations/rules to abide by.

I'm not so sure it's for "cat durability" as it's for cats heating up as quickly as possible. This is why long tube headers don't pass inspection, because the cats are "too far" from the engine.
You are correct about "protection against detonation" however. The leaner a gasoline engine is, the hotter it's combustion chambers get. Conversely, the richer calibrated an engine is, the cooler combustion chamber is. This rule applies only to GASOLINE engines as DIESEL engines are completely 180 degrees different. (For DIESEL engine: more fuel = hotter.)

Yes, "out West" all we have is the 91RON. It's ok but certainly not like the gasoline of the old days.
For instance, here are some specs from SHELL OIL (1965)
Regular Shell gasoline~ 96OCT 2.4 gms pb/gal
SUPER SHELL gasoline~ 100OCT 4.0 gms pb/gal

Tuning for max power without detonation today is easier than it ever has been with the tools available today. Of course, understanding the tools may require schooling but you get my point.

[c4c5specialist]

HI there,

A different perspective here.

Tune, given the extreme LIMITATIONS of hand held/laptop tuners, is a ridiculous term.

Figure this, are you given options for MAP, TPS, airtemp, coolant temp, knock retard or other issues on a 'tuner'??? NO WAY.

There are over 1 gigabytes of information into a programming of the ECM on a 2006 Corvette.

Anyone tell me that your rewriting the entire software is full of garbage.

The hundreds of hours putting a calibration to a PCM to encompass ALL DRIVING CONDITIONS is mindboggling.

When you are rewriting a/f mixture desires and other things, you are writing for a fixed condition, WOT!!!!!!

You are not writing all conditions and all loads from the vehicle standpoint, NEVERMIND AMBIENT CONDITIONS LIKE atmospheric pressure, temperature of the air and moisture content.

The rich fuel trims on WOT DO ONE THING, prevent piston crown and ring OVERHEATING.

I can speak personally about 7 different engines I have had to either replace or overhaul due to 'tuning', every single one was due to AFR set to 13.5 to 14.5 at WOT. One was supercharged.

And in each case, the piston crown melted or shattered altogther.

Yet, if you look at a Lingenfelter/Callaway/Mallet or other reputable modifiers of Corvette, they put alot of work into calibrations.

This is why they are expensive and reliable, because your paying for the engineering, not the actual parts.

Just a technicians point of view.

c4c5specialist

[Hib Halverson]

Fair enough, Hib. Just for reference: The ZR1 is factory tuned for 10.7:1 @ WFO. This is even "richer."

Well....yeah.
The engine is supercharged. When you calibrate the fuel tables for a blower, you always run more rich at WOT than you would with an atmospheric engine.

I agree with you about 12-12.5 being better for power, but GM has many regulations/rules to abide by. I'm not so sure it's for "cat durability" as it's for cats heating up as quickly as possible.

I'm sorry but that's not correct. Calibrating rich at WOT is not for cat light off. It's to protect the cat substrate from overheating and failing during sustained wide-open throttle operation.

Tuning for max power without detonation today is easier than it ever has been with the tools available today. Of course, understanding the tools may require schooling but you get my point.

"Easier"? I disagree. With 91-oct, you cannot tune for maximum power. You either must run a retarded spark curve to stay out of detonation and knock retard--which, of course, reduces power--or you must use a higher-octane fuel. Also, I disagree on the "schooling" part. Those who understand how engines work, how engine controls function and is computer literate can learn how to do calibration work. No doubt, classroom instruction might make the learning curve less steep, but I don't think schooling is required to learn tuning.

[NORTY]

I'm sorry but that's not correct. Calibrating rich at WOT is not for cat light off. It's to protect the cat substrate from overheating and failing during sustained wide-open throttle operation.

Funny how the written word can be mis interpreted.

"Easier"? I disagree. With 91-oct, you cannot tune for maximum power. You either must run a retarded spark curve to stay out of detonation and knock retard--which, of course, reduces power--or you must use a higher-octane fuel.

Maybe I shouldn't have used a subjective term such as "maximum power." Since the sky's the limit with special fuels and a bunch of other variables.

Also, I disagree on the "schooling" part. Those who understand how engines work,

Are taught.

how engine controls function and is computer literate

Again, are taught. Be it self taught or formally taught. All techs are taught. Even "backyard" mechanics are "self taught."

can learn how to do calibration work. No doubt, classroom instruction might make the learning curve less steep, but I don't think schooling is required to learn tuning.

It depends on how "schooling" is defined. In my own personal experience, I've dealt with carbs for too many years. Always adjusting, changing jets, trying other things, changing diaphrams for CV carbs (motorcycle.) Changing whole carbs, and then changing jets. It was always "hit or miss" since I had no access to A/F metering. This is what I meant by stating "Schooling and having the right tools makes tuning easier."