im putting a vtec head on my sohc zc in a week or two, im going for some higher comp. I enjoy paying for minimum octane, but i know there will be a point where i can't anymore, about what compression will i need to upgrade to higher octane?

 

If someone can break down an octane chart, that would great.

Example: 9.7 requires 91
10.5 requires 93, etc.

 

That's not entirely accurate - compression isn't the only factor for detonation.

The style of the combustion chamber makes a big difference. The Y8 head has the best design of combustion chamber vs. all other D series motors.

Also making sure the combustion chamber is nice and clean helps quite a bit, you might notice that most octane boosters are mostly made up of cleaners - by cleaning up the valves and the chamber it lowers the octane requirements of the motor.

But if your gonna raise that compression number above 9.5:1 you'll definitely want to fill her up with some higher octane fuel.

Just a thought.....



[Modified by MrTodd, 8:00 PM 10/21/2002]

 

idk im going to run 94 ultra in my b16a 10.2:1 compression,

come on peeps u got cash for a swap spend the loot on the gas and stop buying 87 getty
( getty gas contain ethanol, Ch3Choh, this compound is very prone to knocking,) the higher the octane rating, the more heat is required to oxidize it, 2,2,4-trimehtlypentane, and isomere on heptane, has a rating of 100 octane It has more c-c bonds with 4th degree carbons and 3nd degree more enegry is released upon oxidization of this substance,) while n heptane (not as many c-c bonds all primary adn secondary carbon bonding) has a rating of 0 ,so 91 octane contains 91% 2,2,4-trimehtlypentane and 9% octane

now 100 + octane rating are isomers of heptane but higher order hydrocarbons.

bottom line the higher hte rating hte less **** in your gas

a little organic chemisty for u kids at home

FUEL

ps. i know my chemisty its my major so i didnt pull this out of my ***


[Modified by CRXSIFUEL, 3:14 AM 10/22/2002]


[Modified by CRXSIFUEL, 3:16 AM 10/22/2002]

 

What the HELL was that?

Dude that flew by me about 7 times.

 

thats my passion other than my car man, im all about chemistry, calculus and physics, i plan on getting my phd in nuclear physics/ nuclear chemisty

and im dead serious about his

muhahahhaha <-----------gotta practice on my evil scientist laugh

 

Hey performula - I couldn't help reading your list of mods... How do you like your suspension setup? H&R's w/Koni yellows? That's the setup that I had in mind, do you like it? You don't happen to have any pics of your car do you?

I don't want to too low - 2.25"/2" is a little low for me, but it might be just right.


[Modified by MrTodd, 8:40 PM 10/21/2002]

 

ohh yeah cool beans, i'm gunna be running close to 11:1 on my minime setup

 

So you're using the Y8 head then?

You'll definitely need to run the highest pump gas that you have in your area.

Over here the highest we get is 91 octane, but it seems like it's pretty high quality - my 10:1 compression runs great on the 91 (chevron, not sure if it makes a diff brand names - y8 head) I've even got the distributor advanced 2 degrees, I'll try advancing it 3 & 4 degrees and see if I get any knock.

But yeah, definitely up those octane numbers.. 91 is my guess.

 

i've got 93 and 94, but 93 is more common....so im assuming, either siphon my tank, and have a gallon or so of high octane so when i get the head on i'll have a good base to tune, or get octane booster...what would be more effective?


[Modified by altoid, 12:31 AM 10/22/2002]

 

there is a sunoco on lochraven and taylor avenue that sells 102 octane (98+), altoid I know u live in the towson area, so u might want to check that gas station out.
I have a b16 10.2:1 compression and run 93 usually and it is fine, nothing under 93 has ever came close to my engine.

 

Listen to CRXSIFUEL...he knows his stuff.

BTW (this is for everyone)...no need to be embarrassed and/or defensive about loving chemistry and physics, or anything else academic. That stuff is extremely intriguing. Next to the "car thing" my greatest interest lies in physics in general and particle physics/quantum mechanics in particular. I am the only person I know who reads books on those topics "for fun".

 

holy **** thats awesome, i would love to tell people im running 102, haha

 

altoid, you can run 12:1 safely on 93 and not have problems

 

It's OK. From what I've been reading the Konis cannot handle 400 and up springs. Which I think is false, but apparently not. I've called Koni numerous times about their limits and they said the 450F 360R is fine.

Make sure you have some tire in your fender. My car looks jacked up, but lowered with 195/45R15 tires. Stick with the 205s and a 43-45 offset (in 15 inch).


[Modified by performula, 12:12 AM 10/23/2002]

 

i plan to run ~11.6 is this safe to run on 91 octane... in a b16a?

trying to decide what layer head gasket to run

thanks

 

My engine would never run any faster, as is, on 102 octane than on 94.

It all depends. if you're going to leave your timing stock and you aren't going to rev to astronimical rpms then you should be fine, assuming your N/A.

If you're going to rev high or advance your timing you need to run a higher octane.

With a motor at say, 10.2:1, and your timing at stock you would be just fine with 89 octane.. no biggy. If you ran 92 or 94 you wouldn't make any more power but your motor would be happier.

Do this. Run the highest octane you can pump, it's 92 here, and keep your motor at stock timing or a bit retarded (lol). Then on race day put a higher octane fuel in, whether it be 110 from the airport or a bottle of toluene, and advance your timing a few degrees and poof...instant race power


I don't think I helped but the typing was fun.

 

Most of the magazine articles I have read about the subject including one in the new sports compact car say that up to 11:1 is safe on pump gas (up to 93octane) not 12:1. Tortex might be right but I would not risk it, there are a lot of people who have degrees in this stuff that say other wise.

 

Very informative, thank you, that is a good explanation.

 

also keep your car as cool as possible, the hotter it gets, the more prone to detonation it will be. So make sure you have a good cooling system and if possible a low temp fan switch and/or thermostat.

 

timing will +/- few degrees and plan to rev up to but not past 9k and yes N/A

here in cali 91 is the highest pump gas availible


[Modified by cl4show, 9:09 PM 10/25/2002]

 

preventing detonation is muhc more involved than just runing higher octaine (slower burning) gas. timing, cooling, amount of fuel etc all play a factor.

in theory you can run 89 on 11:1 while running rich and having slightly retarded timing. rich = cool = less prone to predetonation.

 

My car UPDATE:

Still using Chevron 91 pump gas, I set the ignition timing as advanced as it will go (5 degrees?). It was really hard to listen to my motor, since my exhaust is so LOUD, but it seemed to get a TINY bit of knocking (or maybe it was just me) between 4k-5k rpms, WOT uphill.

I set it down to about 3(maybe 4?) degrees advanced, and it seems to run pretty nicely! I'll tell you guys right now, that comparing the stock timing, to fully advanced timing there is a very noticable power increase, mostly in the low end.

Anyways, I think different states use different levels of octane according to the air quality/density of the area. For example, high altitude states might have a max pump octane of 91, whilst sea level states will have a max of 93 octane. Because of the higher elevation, the air has less density, and thus octane requirements aren't as high - more air in the combustion chamber promotes combustability, thus detonation would be more of a problem. But with less air in the combustion chamber, things aren't gonna be quite as explosive, so a slower burning fuel might not be needed as strongly... Make sense?

This idea just popped in my head, I have nothing to back up my claims...

Have fun all.


[Modified by MrTodd, 8:10 PM 10/25/2002]

 

thats usually how it works

 

CRXISFUEL yeah i know this guy who is a chemical engineer and he gave that speech to me about octane when I said I had to run 110 on a 10.1 comp motor with 12lbs of boost.lol sounds exactly like what you said. We also disscussed the possibility of heating the fuel for more power....


Blaze