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Old 07-21-2003, 02:42 PM   #1
C Dust
Scooby Newbie
Member#: 8924
Join Date: Aug 2001
Location: New Jersey
2002 Impreza WRX
WR Blue

Default Tuning Noob

Sorry for the noob questions, but I want to try to understand everthing as best I can.

What is detonation, what is knock and how does the air/fuel ratio effect the car.

Please point out any websites that may be helpful to noobs for tuning issues.

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Old 07-21-2003, 03:27 PM   #2
Scooby Guru
Member#: 12454
Join Date: Nov 2001
Chapter/Region: Tri-State
Location: Vermont
10 Toyota Taco
K8 SV650SF


Eh, quick description.

Detonation, or preignition, or knock is when the gas and air mixture in the engine ignites before the spark plug is supposed to ignite it etc. Usually this can put alot of stress on the cylinder, as well as damage it or put a hole in it or something bad like that if it's serious enough or if it happens all the time.

Your UTEC will flash the CEL when you are getting detonation, and if you datalog there is a "knock count" column in logger 1 etc. so you can see exactly where it is happening to tune it out. Gasoline octane determins it's resistance to detonation, the higher the number, the more resistant it is to pre-ignition.

Rich/lean air fuel ratio is simple. the Term "rich" means that there is alot of fuel in the mixture, the term "lean" means the mixture has less fuel and more air. The terms are thrown around so you might hear someone say "Lean out the mixture at x rpms, and richen it up here etc."

At part throttle you will see an a/f ratio of about 14.7:1 displayed in your UTEC logger when logging, that is what the car's computer tries to keep the a/f ratio when cruising at part throttle. That is a very "lean" air/fuel ratio..

When you go WOT, you are most likely seeing "rich" appear in the column. Or you should I mean. Then on deceleration you might see "lean" appear in the column under no load, that is normal also.

Someone else do how the a/f ratio affects the car question
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Old 07-21-2003, 03:37 PM   #3
Scooby Guru
Member#: 8512
Join Date: Jul 2001
Chapter/Region: South East
Location: St. Pete, FL
2002 WRX chassis...


Good for you! Hopefully you're truly interested in putting the effort and study into it that it deserves.


http://www.amazon.com/exec/obidos/tg/detail/-/1859606911/ref=pd_sim_books_1/104-5091501-7880727?v=glance&s=books (this 2nd book has surpassed the beloved Maximum Boost by Corky Bell in my recommendation list)

Plan to read, study, and think about this stuff (which is just the surface) for a minimum 10 hours a week for at least a year for a proper basic understanding. This is a career in scope, when done thoroughly (properly). You can take it to any level you care to, just don't fool yourself into thinking "learning tuning" is something you're going to pick up in the next 2 months if you actually want to understand what is going on instead of being a monkey who just knows what's bad and what's good based on what his friends said...

Good luck
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Old 07-22-2003, 10:47 PM   #4
Scooby Specialist
Member#: 33410
Join Date: Feb 2003
Chapter/Region: Tri-State
Location: wishing i was somewhere else
08 wrx


detonation is NOT pre-ignition. I would take detonation over pre-igintion anyday.

read this thread.

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Old 07-23-2003, 11:11 AM   #5
Scooby Specialist
Member#: 9898
Join Date: Sep 2001
Chapter/Region: MAIC
Location: VA near MD
2002 WRX
Water Injected Blue

Default Ditto

Originally posted by MikeWRX-NJ
I would take detonation over pre-igintion anyday.
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