turbolou

icedancer

I also personally witnessed Dave Hills announcement in Bowling Green in May of 2005:

93 octane is RECOMMENDED for the C6, but it is REQUIRED for the Z06.

He went on to reiterate REQUIRED for the Z06.

Has he revised that statement? Or has Chevrolet made a WARRANTY statement that the 91 octane available in the western states will be adequate?

I sure hope this is not a case of caveat emptor.

Michael A

In this case (rare I know), California tried to do the right thing, and get out of using ethanol as an oxygenate. The farmers lobbied Congress to the point that the EPA mandated California use of ethanol, even though it is more expensive than other oxygenates.

Thanks, Feds! Now our gas is even more expensive, and our engines produce less power.

Michael

vizkiz

Porsche's minimum recommended fuel is 93 octane, but they sell those in Cali, don't they?

glass slipper

Federal law requires all vehicles sold in the USA to be CAPABLE of running on 87 octane. The C6 Z06 is not exempt from this law so the sky is not falling! Dave Hill may have had his statement taken out of context or may even have misspoken (I wasn't there), but rest assured, if you were willing to take the HP hit, you could conceivably run 87 octane. 93 octane is available here and that is what I run in my ZR1. And one day when I get a C6 Z06, I'll do the same, can't see buying all that HP and then leaving some on the table for pennies a gallon. Ok, dimes a gallon.

SWCDuke

Oh!!! So was the USC cite or agency regulation for that one.

The Z06 fuel spec is "93 PON recommended, 91 PON minimum", but here's the real deal:

If you don't use 100 PON race gas, your Z06 will be limited to 150 HP!

Duke

Z06forski

couldnt you just add some octane booster to add a couple of points ? used to do this in the past, just do not know if you can do this in the Z

DJWorm

Everyone in California should cancell their orders and have the cars shipped to Pennsylvania !!

glass slipper

A letter to car manufacturers from the EPA. You are correct, it's a federal regulation, not law.
http://www.epa.gov/otaq/cert/dearmfr/vpcd9701.pdf
An excerpt from the letter...FTP is Federal Test Procedure, SFTP is Supplemental Federal Test Procedure, HWFET is Highway Fuel Economy Test, and finally 91 RON and 96 RON is equivalent to 87 PON and 93 PON or what we refer to as regular and premium.

"Under the provisions of section 27 of 40 CFR Part 86, EPA began to require manufacturers to show, prior to certification, that knock sensor equipped vehicles could operate on 91 RON gasoline without effecting emissions or fuel economy. To do this, manufacturers have to demonstrate that the knock sensor output does not alter spark timing during FTP operation, or that the fuel economy difference between 96 RON testing and 91 RON testing is within 3 percent. Either option requires the manufacturer to run special testing.
...
EPA has rarely found that knock sensors come into play when tested with 91 RON fuel. There is no likely motivation for a manufacturer to design a calibration that results in spark retard while operating on recommended regular octane gasoline. Therefore, in lieu of test data, EPA will require that manufacturers submit a statement attesting to one or more of the following:
1. The knock sensor does not activate in any way during the FTP (or the SFTP as applicable) and the HWFET, and the calibration is designed to operate on 91 RON gasoline without the need for park adjustment.
2. The city and highway fuel economy test result differences between comparing 91 RON operation and 96 RON operation is ithin 3%, and there are no emissions increases (beyond normal test variability) using 91 RON fuel when tested on the FTP (or SFTP as applicable)."
...Hope this is what you're looking for. Oh yeah, I'm from the Government and I'm here to help.

SWCDuke

Thanks for the source info. I wasn't aware of this, but do you know that it's still in effect - kind of casts a cloud on GM's "93 recommended, 91 minimum" requirement UNLESS Z06 won't get through the FTP on 87 PON without timing retard that reduces fuel economy by more that 3 percent.

Duke

glass slipper

I don't know for an absolute fact if it's still in effect, but if I were a betting man, I'd say it is. I say that because the EPA doesn't want a repeat of what Cadillac did in the early '90s. All the EPA tests are run with the A/C off, so Cadillac had one fuel/spark program for when A/C was off and another (more aggressive one) for when the "Climate Control" was on that gave more HP but increased emissions. And of course we know most Cadillacs had the Climate Control on, one of the few cars that was faster with A/C on . Anyway, the EPA made them have a recall to replace the ECM chip. I think since then the EPA has gotten wise to the tricks that can be played with the computer which is what generated this regulation and I think is here to stay. Damn Cadillac, they were smart, but not smart enough to not get caught .
...I think (emphasis on "I think") the "93 recommended, 91 minimum" is to get max performance. In other words, you can run 87 octane, you just won't get close to 505 HP but part throttle operation will be acceptable as in very little spark retard. I say this because the FTP and HWFET are done at light to moderate throttle with A/C off and moderate ambient temperature (not 90+ degrees). Given those conditions, I think 87 octane would work with very little spark retard allowing GM to stay within the 3% window. The SFTP is a different story as it uses more aggressive throttle.
...I'll do some more research and see if I can confirm my "bets" and "thoughts".

Michael A

I think Chevy would have to say this, because while it will run on 87, they don't want their customers using it, or they will get all kinds of complaints about lack of power and pinging. I'd venture to guess the same kind of cheapskate who would run 87 in a Corvette, would also be the type to sue GM to get some money out of them for how badly their car ran on 87.

Michael

glass slipper

We'll see exactly what Chevy says when the owners manual comes out, but the EPA has already spoken: the engine must be capable of running on 87. The car won't run "bad" on 87, it just won't make as much HP (and I'm sure the owners manual will address the reduction in power as it has in the past). Therefore, any lawsuit will have no basis. Pinging is not detrimental to the engine, in fact, it is the point of max efficiency for the engine without causing mechanical damage. If the engine parts could mechanically withstand it, detonation would actually be the point of max efficiency. Diesel engines are about the closest you'll get to "detonation", ever wonder why they get better MPG (besides having no throttle valve thus greatly reduced pumping losses).
...Running 87 in a Corvette is not necessarily a bad thing depending on the circumstances and doesn't mean a person is a cheapskate. My daughter runs 87 in her '99 coupe in the winter because the lower ambient temps and less humidity significantly reduces the octane requirement to the point she sees no reduction in HP or MPG. As a college student, she wants to save where she can without sacrificing anything. So from the "cheapskates" point of veiw, they might look at the guy using premium in the winter and think "gee, if that guy was smarter...". It's all about perspective and I certainly respect yours, in fact I've run 93 in my ZR-1 exclusively since brand new...winter or summer.
...There are a lot of variables when it comes to octane requirement and knock, but really, the sky is not falling.

SWCDuke

I wouldn't say that "pinging" is not harmful. Sustained detonation such as pulliing a mountain grade can cause damage, but most most detonation on modern cars with knock sensors is usually transient in nature and rarely causes harm, though detonation damage can be cumulative.

The best bet is to reduce throttle or shift to a lower gear if detonation is more than just transient.

Especially with today's high compression ratios and marginal fuel octane, the point of maximum thermal efficiency is the ragged edge of detonation. Modern spark advance maps are more aggressive than would be possible without detonation sensors, so the OEMs set them up for best efficiency, and the control electronics will retard as required if detonation is detected, and inlet air temperature is a BIG factor. Detonation tendency increases as inlet air temperature rises. High coolant temperature is also more prone to detonation. If it's 100 degrees outside and your coolant temp is 220, the control electronics will probably have to retard unless you run higher than commonly availalbe octanes - like 100 PON unleaded race gas, but spark retard is for the most part transparent to drivers.

This is one of the reasons why modern cars get better overall mileage than pre-detonation sensor engines from 10-15 years ago, even though model for model and engine for engine, modern cars are mostly heavier and more powerful than their non-detonation sensor ancestors. Modern engines on average are operating at higher thermal efficiency than older model engines that don't have detonation sensors.

Duke

glass slipper

In the '80s before knock sensors, GM had the spark advance on the ragged edge and consumers complained about the "ping" they would hear sometimes. GM did say ping was not harmful and even had a campaign that stated it was the sound of fuel economy because...well it is.
...Sustained detonation will damage an engine very quickly if not brought under control. However, detonation and ping are two completely different things. Knock implies autoignition and an infinite range of severity can be present. Normal combustion flame speed is about 200 ft/sec. Detonation is more explosive in nature (the rate of the chemical reaction is greater than the rate of expansion giving rise to a pressure pulse from the autoigniting region) with the end gases igniting so quickly the "flame speed" is about 2500 ft/sec. Nonexplosive autoignition (the rate of expansion is greater than the rate of chemical reaction) has a pressure pulse too small to be measured and the "flame speed" is 400-800 ft/sec. With autoignition, two different types of vibration may be present. Detonation will give rise to a very rapid increase in pressure throughout the combustion chamber that will be a direct blow on the engine structure resulting in damage (immediate or cumulative) as we both stated above. The ear will detect a thudding sound from the impact and subsequent free vibrations of the engine parts. Depending on how much of the end gas is left before autoignition occurs nonexplosive autoignition has a small to large pressure difference in the combustion chamber and the resulting gas vibrations can force the walls of the combustion chamber to vibrate at the same frequency as the gas. An audible sound may be evident called knock. Ping is a less severe form of knock occurring when little of the end gas autoignites. This slight autoignition is desirable because it will speed the combustion process at a time when the flame speed is decreasing. Max power is obtained when the spark is adjusted to the point of audible knock. However, severe knock can cause failure, ping as GM advertised, is the sound of fuel economy but is not severe enough to cause damage.

SWCDuke

Detonation is "pinging" or "knocking", which are just a verbal descriptions of the sound. Pinging is probably lighter detonation than knocking depending on your point of view.

Detonation damage is due to overheating of the combustion chamber boundaries. The detonation shock waves increase the rate of heat transfer by up to an order of magnitude, which can rapidly overheat aluminium pistons and already hot exhaust valves.

Duke

CFRA_7

For driving around town you don't need anything beyond 87. When you use 91 or 93 on the street you are just buying expensive insurance in case you find a need to go WOT.

DJWorm

On Chevy's web site, the C6 Z06 specifications were added today:

......" 93 Octane REQUIRED. " !!!!

icedancer

can't find it on the Chevrolet site, got a link?

mwittkopf

c6 specs

and click "engine"

It is right there unfortunately.

Mike