How to Advance your Timing
How to Advance Your Ignition Timing
This is applicable for all Celicas. The test
car used is a 1991 Toyota Celica GT with the 5S-FE engine. Other's
may be similar in results. I cannot be held responsible for any
damage that occurs to the engine or the car while this procedure
is followed. Everything is explained to the best of the author's
knowledge. Refer to a Celica manual for more infomation about
Intro: Factory timing for all 90-93 normally aspirated
Celicas (ST, GT, and GT-S) is 10º before top dead center
(BTDC). This means when the crankshaft angle of the number one
cylinder reaches 10º, the spark plug will fire. It fires
before it reaches top dead center (TDC) because the flame front
takes time to fully combust and push the piston downward.
Retarded timing: If the ignition timing on a car is retarded,
then less power is made because the air/fuel mixture doesn't completely
combust during the compression/combustion cycle. The flame front
completely combusts after the piston has started its power stroke.
This results in a loss of power.
Advanced timing: If the ignition timing on a car is advanced
(to a certain degree), slightly more power is made because the air/fuel
mixture is given time to fully combust and to allow the plug spark
to travel. When the air/fuel mixture completes combustion, there
is enough power created to slam the piston downward.
Over-advanced timing: If an improper grade of fuel is used
combined with an over-advanced timing setting, the effects of detonation
can damage the engine. Detonation is when the air/fuel mixture combusts
too early or too quickly during the compression stroke. The flame
front collides with the upward-stroking piston. Pressure in the
cylinder becomes increasingly high. Temperature rises to extremely
dangerous levels. This results in engine damage.
Octane Fact: The recommended fuel grade for all the normally
aspirated Celicas is 87 octane. Everyone should know that octane
is a knock-inhibitor. What octane does is slow down the combustion
process. So, it burns slower giving the piston time to compress
the mixture and the spark to travel. The power comes from the full
combustion of the air/fuel mixture. Higher octane gas + advance
timing = more power. I read somewhere about a guy with an N/A Supra
who advanced his timing to 25º BTDC and used 120 octane gas.
He claims to have made an extra 100 WHP. I find it hard to believe.
The power curve for ignition timing is like a parabola: only at
one single point will there be a peak power position for both torque
How do I advance my timing?
First, obtain the necessary tools.
- A timing light
- 12 mm socket
- A small piece of wire or paper clip
Make sure your car is at operating temperature. You cannot check
the timing correctly if your car has been sitting outside cooling
down all day. It must be at operating temperature.
Step 1: Jump terminals
Locate the DIAGNOSIS plug. It's a gray box on the drivers
side by the windshield wiper motor. Open it up, and jump the TE1
and E1 terminals with the wire or paper clip. You'll know when it's
jumped when you turn the key to the ON position, and the CHECK ENGINE
LIGHT is flashing the "NO TROUBLES" code (1 flash, pause,
1 flash, pause, 1 flash, pause, etc).
Step 2: Hook up the timing light
The timing light has instructions. Read them. Otherwise, listen
to me. Red clip goes on positive side of battery; black goes on
negative side. That black clippy-thingy goes on the number 1 spark
plug wire. Simple.
Step 3: Checking the base timing
Now, you have the terminals jumped and the timing light hooked up.
Start the car. The car should sound like it's lugging and the idle
should be lower than normal. This means you've jumped it correctly.
Locate your underdrive pulley. There are timing notches above the
pulley. Point and "shoot" the timing gun at the pulley
and notches. You will see what your base timing is currently set
at. Make sure youre viewing the notches dead on and not at
an angle. Stand above the engine or to the left on the passenger
side to have a dead center straight-on view of the crankshaft pulley
and the timing notches.
Step 4: Adjusting
Take the 12mm socket and loosen the holding bolt on the distributor.
You can do this while the engine is running as long as you don't
pull the distributor out (duh!). Just loosen it enough so that you
can move the distributor. Rotate the distributor upward (clockwise)
to advance timing; rotate it downward (counter clockwise) to retard
timing. Keep using the timing gun to see where you've adjusting
the timing to.
Henrys Corner. Ive done various degree setting to see
what is the best and most efficient degree to set the ignition timing
at. I was running with 93 octane for each test.
25º+ BTDC: Only good on a cold winter day. Otherwise, crappy
20º BTDC: A little better than 25º BTDC. There's still
some inconsistency in the idling, but it's not serious.
17º-19º BTDC: I havent tried it yet. Feel free to
tell me the results.
16º BTDC: Pretty good for now. Thats what I have it set
at as of December 20, 2000.
12º-15º BTDC: I didnt have any problems, but I wanted
to advance it to 16º BTDC to see how far I could push it.
11º BTDC: Seems just too close to 10º BTDC for any kind
10º BTDC: Thats factory setting. Im tired of factory.
I need change.
7º BTDC: Stupid, Henry; thats retarding your timing.
I cannot confirm 100% why crappy idle occurs. I said it was due
to detonation and the knock sensor was picking up the readings.
But theres a problem: 1990-91 5S-FEs didnt have
at least thats what I read. Also, I started
to tap on my engine with a hammer, and the timing didnt retard.
Despite that, for some reason when I set the timing to 20º-25º+
BTDC, the timing just retards on its own like there was a
knock sensor doing its job. I did check my plugs for the effects
of detonation and there was no damage at all.
My friend told me that the ECU knows that the base timing is 10º
BTDC, and it will try to retard the timing to 10º. Sounds right,
but I have evidence that disproves the theory: I'm at 16º BTDC
and my car isn't experiencing bad idle.
Step 5: Finishing up
When you've set the timing to where you like it, tighten the 12mm
bolt, and turn off the car. Remove the jumper wire. You may start
the car again to see what the "adjusted" timing is. Then,
remove the timing gun.
Is this mod worth it?
If and only if you're trying to squeeze every bit of power from
your car and you're willing to use a higher grade of gas to do it.
I can afford to use a higher grade of gas. I know some people can't,
so it may not be worth it to them.
How much of a power gain should I expect?
Hopefully, you gain some mad horsepower so you can beat Civic Si's,
but I doubt that'll be the case. I read that adding 1º of advance
produces 2 horsepower to the wheels. Of course, this is only a guideline,
and it varies from car to car.