Brought to you in part by:

.

Shop Eastwood for your Auto Restoration Needs!


  Mustangsandmore Forums
  Ford Racing
  11.1comp

Post New Topic  Post A Reply
profile | register | preferences | faq | search

UBBFriend: Email This Page to Someone! next newest topic | next oldest topic
Author Topic:   11.1comp
the last dive
Gearhead

Posts: 147
From: sydney australia
Registered: Dec 2001

posted 04-29-2002 07:57 AM     Click Here to See the Profile for the last dive     Edit/Delete Message   Reply w/Quote
does any body know what octane fuel is required to run 11.1comp?

IP: Logged

jkilroy
Gearhead

Posts: 1719
From: Vicksburg, MS
Registered: Dec 99

posted 04-29-2002 10:23 AM     Click Here to See the Profile for jkilroy   Click Here to Email jkilroy     Edit/Delete Message   Reply w/Quote
It is not nearly that cut and dry. New Corvette's run 11 to 1 on the street with nothing but pump gas and do fine. If I run anything less than 93 in my 68, which is right at 10 to 1, it will ping like crazy.

Aluminum heads can generally use a half a point more than iron. Big cams bleed off pressure allowing you to run more compression. Advanced cams tend to ping more than those installed straight up.

How about some detail on your combo?

------------------
Jay Kilroy
68' Fastback GT 390
"No such thing as a cam thats too big"

IP: Logged

cpmaverick
Moderator

Posts: 1564
From: Auburn, AL.
Registered: Jan 2000

posted 04-29-2002 11:25 AM     Click Here to See the Profile for cpmaverick   Click Here to Email cpmaverick     Edit/Delete Message   Reply w/Quote
Yeah, it really just depends on the camshaft (cylinder pressure). The new Celicas run 11:1 also.

------------------
-Charlie Ping
1970 Maverick Grabber
[email protected] with AC and overdrive.
http://www.maverickgrabber.com

IP: Logged

Dusty Kiser
Gearhead

Posts: 126
From: Bethel,Oh USA
Registered: Mar 2002

posted 04-29-2002 08:50 PM     Click Here to See the Profile for Dusty Kiser   Click Here to Email Dusty Kiser     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by the last dive:
does any body know what octane fuel is required to run 11.1comp?


Like the guys said, it isn't at all cut and dry. Cylinder pressure is the key word. Cylinder pressure is affected by, static compression, valve events, ambient air pressure, engine temperature, combustion chamber configuration, ignition timing, engine speed, engine load, fuel mixture, Fuel quality ( vapor pressure, true octane rating, what additives are used to achieve octane rating etc.) SO, let's assume you are carbureted, no PCM management for spark knock control etc. and you have an engine with a calculated compression ratio of 11to1. You want to run it on the street using 93 octane pump gas. If you have a cam with much overlap for a nice rump rump idle, keep the engine under 180 degrees, use a low cog, say 4.5 with normal street tire so the engine doesn't labor at all, and resist the temptation to want to crank in a bunch of timing at low engine speed, keep the fuel mixture slightly rich and your foot out of the carburetor, you'll probably be OK!

IP: Logged

steve'66
Gearhead

Posts: 6522
From: Sonoma,CA,USA
Registered: Mar 2000

posted 04-29-2002 08:57 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Dusty Kiser:
You want to run it on the street using 93 octane pump gas. If you have a cam with much overlap for a nice rump rump idle, keep the engine under 180 degrees, use a low cog, say 4.5 with normal street tire so the engine doesn't labor at all, and resist the temptation to want to crank in a bunch of timing at low engine speed, keep the fuel mixture slightly rich and your foot out of the carburetor, you'll probably be OK!

Very well said Dusty, especially if he's using aluminum heads. We're putting the 408w around with 11.7-1 compression and pump gas breaking it in with aluminum heads and timing locked out at 35btdc. Haven't hear a ping yet! Of course the converter stalls at over 4000 rpm.

SteveW

IP: Logged

All times are ET (US)

next newest topic | next oldest topic

Administrative Options: Close Topic | Archive/Move | Delete Topic
Post New Topic  Post A Reply
Hop to:

Contact Us | Mustangsandmore Front Page

Copyright 2003, Steve LaRiviere. All Rights Reserved.


Ultimate Bulletin Board 5.47d

Amazon Honor System Click Here to Pay Learn More

[Build a free Mustangsandmore.ws Home Page!]

[About M&M][Acronyms][Calendar][Chat][Classifieds] [Members' Pics] [M&M Mug Shots]

[ Mustangsandmore.com Bookstore] [Mustangsandmore.com T-Shirts][Tech Articles]