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

[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.

[ERA Chas]

Originally Posted by FredBMOC

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?
.

The reason is more power. Knock is not 'such a problem' if the whole combination is built to accommodate the power and it's fed and timed to match.
The advantages are real, not perceived. Barry's last post is a dramatic explanation, you will learn a lot from it.

[jhv48]

I believe it is now illegal to sell race gas in California to any vehicle with a license plate (non-race car).

So, the race gas option is off the table. Better find another solution if you need it.

[RodKnock]

Originally Posted by jhv48

I believe it is now illegal to sell race gas in California to any vehicle with a license plate (non-race car).

So, the race gas option is off the table. Better find another solution if you need it.

That is not 100% true. Unleaded race gas that meets the new state regulations as of January 1, 2010 can be sold from the pump and is being sold at a gas station near me. They can also sell leaded race gas, not from the pump, but you have to fill out some paperwork first and state that you will not use it in a street car. The leaded race gas must be used for race cars on a race track only.

FYI, the 91 octane here in CA may not be the same 91 octane that you get in other parts of the country. Our gas has a "special" formulation, just for us folks in CA.

[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!

[RodKnock]

As far as I know, no one has tested the gas that this station sells. Is it legal? I don't care. It's the State's responsibility to police the matter. Not mine.

What I do know is that is it legal to sell unleaded race gas if it meets the 1/1/10 CARB guideline. It is also legal to sell leaded race gas to race cars only to be used on the race track only.

This station sells unleaded race gas from the pump, no paperwork needed, and leaded race gas from drums in the service area, bring your own gas cans, which requires paperwork to be filled out prior to purchase per the CARB guideline. They appear to be selling racing gas in accordance with current CA law.

[ERA Chas]

I can see it coming; soon the nazis will have a "smell test" added to the regimen to bust you for using race gas on the street.

[Rick Parker]

Here in KALIFORNYA if 100 octane unleaded is being dispensed at the pump with the various taxes being assesed including road tax then it is legal for use in a "Street" car.

[bobcowan]

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.

Lots of interesting suggestions and arguments. Unfortunatly, they're all based on too little information.

What's important is Dynamic Compression, which static compression plays a role in. Dynamic compression is the key.

The second most important component is intake valve closing point. The intake valve closes as the piston is coming up into the compression stroke. If it's very late, like 85* ABDC, then the piston doesn't compress much air/fuel. If the valves closes early, like 30* ABDC, then there's a lot of swept volume, and cylinder pressures will be high.

So, do a little more research, and find out what your compression really is. Fortunalty, it's pretty easy. On a warm engine do a compression check. If your cylinder pressures are low, like <170-180psi, you'll be fine on premium pump gas and a good tune. More than that, and you'll have some problems.

Case in point, I run 13.5:1 static on premium pump gas. But the rest of my engine build, and driving conditions support that. My dynamic compression is 8.449:1. When I got to the track, I know cylinder pressures will rise so I use 110 race fuel.

If you have more engine information, you can do some calculations here to see where you're at. http://www.wallaceracing.com/Calculators.htm

[Barry_R]

Dynamic compression ratio numbers are interesting and directionally useful - but they're decidedly not the end answer. They are really neither "dynamic, nor "ratios" - just a mathematically derived value for comparative purposes. Only a single piece of the puzzle.

There is nothing in the DCR calculation to account for a well shaped and contoured combustion chamber versus a less effective wedge or hemi. Nothing in the DCR accounts for crevice volume, piston dome shape, quench, low lift valve flow characteristics, exhaust back pressure, or a plethora of other things which will definitely have a significant impact on a running engine's cylinder pressure signature or tendency toward detonation.

[Excaliber]

Quench, good point. Following Gessford Machine's advice, I had my new custom pistons spec'd to raise them in the bore to introduce some quench into the combustion chamber. One of the benefits, as I understand it, is the ability to run more advance and lower octane with less impact on detonation.

[Excaliber]

Having to run race gas just didn't work for me, it's to limiting on how far you can drive for one thing. Not to mention the extreme cost! It's not like you can just pull off the freeway at any given place and find race gas. I need something that can go the distance and is reasonably easy to care for, maintain and buy fuel at a decent price for.

Having said that, I did give up some horse power when I rebuilt for a more streetable tuned motor. Most of the time, I don't miss the really BIG power because I can barely hook up what I got anyway! Tires are always the limiting factor. BUT, when I'm running the race slicks (front and rear) and tearing up Infineon raceway, I do find myself wanting a bit more power in the higher gears.