11 to 1 - too much on CA 91 pump gas?

[ERA Chas]

I'll say this once more-not sure if the OP is even watching anymore. This is solvable without going into the engine or running 20 degrees total.
I say this because every day I used to document engines' performance on DTS dynos. The bulk of those had these parameters: 91 Octane Shell pump gas, 10.75 to 11.3 CRs, 427 to 632 C/I, AFRs from 12 to 14, aluminum heads, smallest carbs were 850's, biggest were 1050 Dominators. HP ranged from 560 to 825. All cams had 108 to 114 LSAs, were SFTs or juice rollers and had advance from 28 to 36 degrees. All were tested under load and none pinged or ran hot. NONE used octane boost. The drag engines had 12.5 to 14.0 CRs and ran on C-14.
Doesn't it just make sense to try the simplest, least costly, proven suggestion???????

[Excaliber]

And ONE POINT of octane boost is 1.0- NOT .1

Who says so Chas? Is that some kind of Government regulated standard or something? Perhaps they mean MON octane instead of RON octane? Booster bottles can say whatever they want and do!

It could be 1 or .1, either way, it's fair game for the bottle to say it raises octane by a "full point", whatever that is. Not to mention there are a number of separate international standards when it comes to octane ratings.

Consider a couple of typically available boosters. Like "NOS", which claims a 7 point increase (and pigs fly). NOS is one of the best available! Tests show it actually does raise the RON by 1.8 points. Hardly a "7" point increase, but perhaps "NOS" really does raise it to a "7", depending on who and how the measurements were taken?

Wynn's, a common brand name, was good for 0.8 increase on the RON meter, while claiming a 2 to 5 point increase.

You all know "Super 104+", it was good for 0.9 boost, while claiming a 4 to 7 increase.
There are a number of boosters that barely make a .1 octane increase. Buyer beware. The bottom line is, "boosters" can make all kinds of claims without fear of running into truth in advertising laws.

I was running 12.5 to 1 compression with IRON heads on my side oiler. Knock was a constant problem. I learned a bunch about timing issues, lean or rich fuel settings, octane boosters, etc. etc. When the smoke cleared, literally after wiping the camshaft out, I went with new pistons. I was sick and tired of the constant "octane battle", the BS octane boosters and the $6 a gallon race gas. I would have tried thicker head gaskets, but my compression was already so high I needed to take drastic action.

Mostly I just backed off the timing, BUT, I could feel and measure (at the drag strip) the loss of power with reduced timing. Man that motor LOVED a lot of advance and dropping it would just kill the power. But, at least I could drive on the street...

[Bill D]

Can you add Toluene to raise the compression without any side effects?

[greg schroeder]

You'll destroy the pistons with 91 octane in time. It's funny how many people do it and then sell the car with the "never been raced" sales pitch.

If you get 116 octane fuel to set in the garage just dump in 3 gallons to be mixed with 10 of the 91 octane pump and it will be around 97 octane. Done.

I most often used 100 octane unleaded from the pump here in Scottsdale, AZ.

[Excaliber]

Destroy the pistons may be dependant on what kind of pistons he's running. Hyper's? Yeah, they will be toast much quicker than forged.

[patrickt]

If the OP is still watching, he should try what Chas has recommended. If it doesn't work, then have Barry spec out a new cam for you. Maybe you can change it out without pulling the engine. I wouldn't keep a 55 gallon drum of race gas in the garage.

[Excaliber]

Nor would I Patrick, what a PITA the whole octane booster scenario is no matter how you do it.

As far as the original OP goes, no problem, many threads have value that goes well beyond the original poster.

[greg schroeder]

Originally Posted by Excaliber

Destroy the pistons may be dependant on what kind of pistons he's running. Hyper's? Yeah, they will be toast much quicker than forged.

Yep, and the pistons will get jacked either way in time before the guy sells the car. It sort of goes along with why is my motor blowing oil. I need warranty work. All I did was nail the gas a few times when the engine was new and cold after I picked it up on the way to the dyno.

[ERA Chas]

Originally Posted by greg schroeder

You'll destroy the pistons with 91 octane in time.

Greg,
I respect that you're smart enough to run 10's but how do you account for this statement - nitrous? I didn't encourage the OP to run with detonation.

All those engines I wrote about were warrantied for 2 years and they only came back for broke pistons (and not covered) if they were sprayed by a dummy.

[MFE III]

Quote:
And ONE POINT of octane boost is 1.0- NOT .1

Who says so Chas? Is that some kind of Government regulated standard or something? Perhaps they mean MON octane instead of RON octane? Booster bottles can say whatever they want and do!

One point does equal 1. Same as points on a mortgage. One point equals 1%. When you're speaking about values less that 1 point or percent, you're talking about basis points. 10 basis points equals .1%

So if the booster bottle says it increases the octane by one point, they mean 91 octane will go to 92. And since it's written on the bottle, it must be true, right?

Matt

[ERA Chas]

Matt-maybe there's a full moon tonight?

[patrickt]

Interesting little article on boosters and some tests on them. http://www.europeancarweb.com/tech/0...ted/index.html

[Zoom This]

Wouldn't worry a bit with your combo. I have a 418W with 11:1 static CR, alum. heads and 21 degrees initial and 32 total timing. Yeah, it might ping at 100 degrees outside with too much low rpm throttle tip in, but just don't go mashin' the gas when it's 100 degrees out in 5th gear. Always used 91 octane.

[Rick Parker]

In reality if most of your driving is done within what equates to the distance driven on 1/2 a tank of fuel radius from your home you can make the engine pretty much anything you want as long as you feed it the necessary fuel (what ever that dictates). I'd like to do a 12:1 in a 289.

[Excaliber]

Matt, WHO SAYS, a point is a point or a point of a point? Where is that written in stone? What government agency specifies that every bottle of booster has to comply with your, or Chas' view of what equals a point?

I have seen studies that specifically show that some booster's claim a full point and do in fact mean that to be 0.1. There is no law that governs, nor is there even a consensus within the industry as to common standards of testing an octane booster. Every single study will vary the methodology used and consequently the end results.

Every booster product on the market, world wide, makes wild claims as to what a consumer can expect from their product. Every. Single. One. Not that they, or the mortgage companies would ever lie to the consumer. No need, they just use "fuzzy math" to keep you in the dark, all perfectly legal that way.

[Excaliber]

Back to the 11 to 1 C.R. question. I concur with several opinions on this thread that with careful use (no lugging of the engine under any circumstances) and alloy heads it won't be a significant problem.

Here's one example of a "point" from a Tuner Web site study.

Published third-party information about 104+ Octane Boost claims a "five-point" octane increase, which, in marketing terms, translates to a 0.5 jump in the AKI octane rating.

AKI (anti knock index) is really the most important number to be concerned with here, it's essentially an average of the RON (part throttle test procedure) and MON (full throttle test procedure).

[PLDRIVE]

It would help if he gave some more info. He did not say what type of car (Weight)? Is the engine already built? What do you plan to do with it? What are the cam specs?

[Barry_R]

I recently ran my 11.5:1 compression 433 cube FE EMC combination at 29 degrees to eliminate detonation running pretty marginal 91 octane spec fuel. It made "only" 640 some horsepower that way - in competition. On the 93 octane premium from the corner Exxon station I could run with 37 degrees and it made 674 horsepower.

The short answer is thus "yes". It can be done because I and many others have done it with numerous media guys and witnesses standing around watching and listening. "Cheap" and "easy" are not terms I would apply to this engine though.....

[FredBMOC]

ok, let me "dumb down" this whole thread...
Why do people buildup engines with such high CR and timing advance if knocking and detonation are such a problem? What perceived advantages are there? more power? what?
TIA for taking the time to educate me but I really know nothing about engines and am interested in learning more.

[vector1]

Originally Posted by garry viohl

482 FE with aluminum heads and 35 total timing.

Do you think it will ping? What happens if the air temp goes to 100?

Thanks.

bet i could make it ping!