Please explain how a fuels ability to prevent detonation changes depending if air is forced in or not.

 

Simple. A forcefed car generally REQUIRES a high octane fuel because by definition it is operating at much higher compression ratio (the boost on a turboed or blown car runs anywhere from 7 psi to 30 psi), and any detonation occurrence will destroy the engine much faster than a typical naturally aspirated engine. A forcefed engine generally requires very stringent octane control and a rapidly responsive timing retard system to prevent its destruction when lower octane fuel or heavy momentary load begins to cause detonation. The stories recounted in the various "Chevron 94 is bad" threads all concern engines like this, and all recount cases of the timing being retarded by the ECU to protect the engine . The assumption made by the authors is that Chevron 94 has inadequate true octane despite its "94 octane" rating, and that Shell 91 octane works better. All these cases involve cars running one of 2 aggressive aftermarket tunes, not stock tunes.

Our C63 engines have very different requirements. While very strong in power output, MB got that power via a much more modest amount of net naturally aspirated compression, and using MUCH greater sheer displacement instead. In other words, a relatively understressed huge V8 engine versus a tightly wound, highly stressed turboed or blown small displacement engine. Furthermore, most of us run a completely stock C63 engine with its stock factory tune, and I myself, specifically, do so. So, I don't NEED high octane. Per the owners manual, an octane level well below 94 is fine for the C63 engine. So, even IF the writers on the trash-Chevron-94 are correct about its true octane somehow being worse than Shell 91's true octane, I am totally unaffected. As long as the Chevron 94 I buy has at least a "true" 91 octane, is fresh, has minimal water content, etc. it will work just fine. And, it satisfies the other key requirement that I insist on for a fuel for my cars or motorcycles: it contains no Ethanol.

I suspect that I could run EITHER Chevron 94 or Shell 91, each being ethanol-free apparently, in my car and motorcycle, but in Parksville BC, the Chevron station is the higher volume and better maintained source of fuel, and both those factors, higher volume and better maintenance, are more likely to ensure (but of course do not guarantee) better freshness and lower contamination than at a lower volume, less well maintained station. So, I buy my fuel from the Chevron station and I buy the 94 octane Chevron not specifically because it is "94 octane", but because it is Chevron's highest octane offering and has no Ethanol in it.

Jim G

 

You didn't answer the actual question I asked. Instead, you attempted to blend it into another topic.

Again, the application is irrelevant. Doesn't matter if you use an NA engine, FI engine or even a CFR engine. The ability for the CDN Chevron 94 to hold off detonation longer than the CDN Shell 91 won't change.

The input variable remains constant no matter the experiment.

 

I did answer your question. You just asked it incorrectly. Let me explain it for you even more clearly:

You asked specifically about my post in which I said:
"That was a FORCEFED engine, not a naturally aspirated engine. You BET it makes a difference - a HUGE difference. But you already knew that didn't you."

You asked:
"Please explain how a fuels ability to prevent detonation changes depending if air is forced in or not."

What you should have asked me, based on the last post that you referenced specifically, is "Please explain why a fuel's ability to prevent detonation is far less relevant if air is inducted naturally versus forced in."

And I did answer that question.

We can continue to play word games where you try to salvage your tender ego, but we both have better things to do.

In summary, the purported ability of Shell 91 to handle aggressively tuned boost situations better than Chevron 94, even if later somehow proven true, is completely irrelevant to a C63 owner unless he or she gets a supercharger kit installed on the C63.

Jim G

 

Then you have completely missed the point. The 94 HAS caused issues in the C63 as well as the other AMG with the NA 6.2l motor. At the very very very absolute least, it is a suspect, whereas the Shell 91 is not, and is also ethanol free.

Jim, I'm sorry but your first post was the best, and it has been downhill from there. Since then it has all been a one sided monologue, rather than a dialogue, as you skim read other members and then churn out some page long screed. I'm just not into that.

 

Not true. YOU completely missed MY points:

- The Chevron 94 maligning posts are not anywhere near sufficiently rigorously proven to be trustworthy

- And, even if some of the "allegations" are ever proven, they seem completely irrelevant in the context of the C63 engine's fuel requirements, and this IS a C63 forum and C63 fuel discussion

- None of the postings referenced show any shred of verifiable evidence that Chevron 94 has adversely affected any C63 engine

I make decisions based on proven facts, not innuendo on testosterone-soaked car forums.

Jim G

 

I didn't ask the question incorrectly. Your replies suggest you don't fully understand how octane works.

Your lengthy babble replies may confuse someone who's not technically inclined.

You're trying to state your M156 engine with an OEM tune will not cause the Chevron 94 to detonate. Nobody disagreed because it's likely true, but you continue to state this like we don't understand.

We (more than one of us) are saying something fishy is going on with the Chevron 94. So is the rest of the internet with practical experience and physical proof. Why it doesn't perform how it should? Who knows and who cares, BUT since it doesn't, why risk using it?

Do what you want, run potential garbage fuel (who a member here specifically gave you examples of what happened using it in their very own C63), completely misuse Leatherique, provide completely useless info about ESP module issues, whatever the next stupid thread may be about. Go nuts, I'm done with you.

 

+1

 

Only in certain provinces. There is no ethanol free 94 in Alberta.

 

Not quoting this post for any particular reason, but just to add to the general fuel discussion.

A local tuner tested various fuels. Shell 91 routinely ranked high for knock resistance. I think Petro/Husky 94 was a bit better, but it contains ethanol so your fuel economy goes to hell.

As a result, a lot of Subaru guys ran Shell 91 religiously.

 

Moreover, if the C63, as a naturally aspirated engine, won't knock, why does he need to run 94 octane in the first place?

 

Thank-you JasonOff and 640C63 fo both opting out of Jim G posting threads! Now the rest of us that actually want to have friendly interesting discussions on the forum can do so in peace.

Jim G

 

I know it's now along thread, but read it for the answer to your question: I buy the Chevron for the fact that it has no Ethanol, not because it claims 94 octane, and the Chevron station in my town is the high volume, better maintained station that improves the odds of getting fresh and non-contaminated fuel.

Jim G

 

Yes, Jim, you have saved the interwebs. Congratulations. Parade on Friday.

 

Holy s**t... I havent been on the forums much lately but this Jim kid is everywhere... Where the f**k is my popcorn when I need it?!

 

And the "kid" is 66 years old too!

Imagine me in my mid 20's **** disturbing prime!

Jim G

 

Wait what? I thought you were in your 40s!

 

I was estimating in the 60's with amount of free time he has and the fact he wrote a 300 page book on a Chevy SSR!


Jim you try and WOT runes with the 94 yet?


Cheers,


-Patel

 

Nah, but my wife says I'm "a teenager" in spirit and maturity.

Jim G

 

I wrote the SSR book in 2005, while I was still doing one contract IT project management gig after another. Now finally I have more free time!

My WOT runs have been only from right turns onto a highway and only up to about 80 mph, as there are no long straight, unpatrolled sections of highway that don't have adjacent deer forests here on Vancouver Island. And the fines and insurance add-ons form the Government run insurance are extremely punitive.

My MB dealership though says that it throws "track days" once in a while at the track (driving track, not drag strip) that we have here on The Island, so I am looking forward to getting the car onto the track sometime, hopefully with few other cars around though (Insurance does not cover off-road accidents, and while I know I will be careful and conservative, I don't know the skills, experience, and responsibility level, and drug habits of anyone else on the track at the same time).

Jim G

 

I promised myself I was going to stay out of this going forward but damn it Jim aren't you precious. 5 weeks in and an expert in all things.
As I said yesterday do what pleases you with your car and be done with it.
The rest of us will just struggle along in our obviously flawed lives when it comes to these cars or for that matter any other MB cars with which we have had good experience.

 

Wow, Alex. Hoped it help to get that off your chest. And by the way, did the email conversation you requested from me on my aftermarket contract help you get yours? I hope so, because I like to help people when I can.

Jim G

 

Well, that was just plain smarmy. Its not like Alex wouldn't help you. I guess people should know that if they do get help from you they better agree with you moving forward or its gonna get tossed in their face.

You are pissing a few people off here, and cruising through it pretty willfully oblivious, and yet the common denominator is you. Its like that driver that leaves a series of accidents in their wake and says "what, wasn't me". Alex hasn't said a mean word to anyone here, so the fact that you are even getting into with him is telling. To my eye you are looking as much the **** disturber as anyone else here, you're just doing it with a smile and burying it in page long diatribes. Ultimately, those are the ultimate website sin.....they are just kinda boring.

5 weeks of ownership and it is straight to Blowhardville.

 

Maybe you're just a bit too sensitive and reading in motives that don't actually exist?

Jim G

 

There it is.

"What? Who? Me?"

And yet you completely dodge and evade the fact that you have frustrated the holy hell out of one of the more emotionally mature members here.
Thats what you do. You are a very subtle troll, but a troll nonetheless.
Time will bear that out.

Whatevs.