timing injection

7/28/2019 Timing Injection

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Isi Kandungan

Bil Kandungan Muka SuratPenghargaan

2. Timing Table

3. Setting the timing

4. How To Check And Setting Timing


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Timing Table

The injection timing table has values in Degrees BTDC (compression stroke). When

using an M400/M600/M800 you can choose to have either a 2D or 3D Injection Timing table

(20 x 11 sites). The Setup Parameter "Injection Timing Position - (itp)" selects Start of

Injection or End of Injection. End of Injection is normally best. When using an M4/M48 the

Injection Table is a 2D table (20 sites) for End of Injection Timing. The table is found in the

Adjust menu under FUEL / Injection Timing.

The Injection Timing may be adjusted at various RPM points and optionally at

various Efficiency Points depending on the state of the 'Miscellaneous Setup - Injection

Timing Table (itt)' parameter. The injection timing position must be selected to either start of

injection or end of injection in the ECU Manager Fuel Setup (M800). It is most common to

select the end of injection point as it is easier to relate this to the time the inlet valve closes

and it means that the values in the table will have smaller steps. At idle speed a 5ms fuel

pulse will have duration of 18 degrees of crankshaft rotation, a 10ms pulse at 3000 RPM will

last for 180 degrees and a 10ms pulse at 6000 RPM will last 360 degrees. So for the same end

of injection time we would have to have a table with very large differences from one point to

the next if we were to use beginning of injection as a timing position. It would also be

necessary to have different timing values depending on the length of the injection pulse.

Normally the ideal aim is to inject the fuel with the inlet valve open but we have to

take in to account that there is a delay between the time the injector closes and the time the

fuel passes through the valve, this delay will vary depending on engine speed and manifold

design. The closing rate of the valve and the amount of valve overlap will also have an effect

on the ideal fuel timing position.


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The best and easiest way to find the ideal fuel timing is by tuning to the richest

lambda value. Moving the injection will have an effect on the lambda reading because in-

correct timing will cause more of the fuel to condense on the port wall and so will not be

burned. As the timing approaches the ideal point the lambda reading will show richer because

more if the injected fuel is being burned. A good starting point is to have the timing at around

270 degrees at 1000 RPM and increasing by 20 degrees every 500 RPM until about 4000-

5000 RPM where the injection timing is less critical (depending on injector sizing). It is

reasonable to expect that this would give the most efficient timing point whether or not there

is any gain in performance. The fuel table can then be re-trimmed to give the desired air-fuel

mixture. When injector pulse times are long the injection timing will have less effect. To

avoid rapid transitions in Injection Timing it is advisable to limit variations between adjacent

sites to less than 100 degrees. A value of 0 is the same as a value of 720 i.e. both are Top

Dead Centre. The value may be increased past 720 degrees if necessary which allows a

transition back through 0 degrees without causing a transition problem. In other words a

value of 820 deg. is the same as 100 deg.


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It is reasonable to expect that this method will give the most efficient timing point and

provide the most accurate control of fuel mixture but there may be applications where this is

not going to give the best performance. The main reason for this is fuel atomisation. If the

injector is not particularly good at atomising the fuel better results may be found by injecting

on a closed inlet valve. This can also be beneficial for engine starting. This will allow the fuel

to atomise better in the inlet port prior to induction but will lead to a less precise control of

fuel mixture.

When the Injection Timing screen is open and the engine operating point is close to

the current cursor position the Injection Timing is forced to the cursor value rather than being

interpolated from the adjacent sites, this allows adjustments to be made without the adjacent

sites affecting the adjustment value. The quick lambda function may be used to adjust the

main fuel table when the Injection Timing screen is open. Some engines (e.g. Subaru) have

tumble valves in the inlet manifold to improve the fuel mixing at loss speed. Where these are

disabled or removed timing the end of injection at about 450 will give best results at idle

speed and starting.


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Injector Sizing

Typically in a production car an injector is selected to run at around 85% duty cycle at

maximum fuel demand. This will normally allow enough resolution in the fuel table at idle

speed to provide accurate fuel mixture adjustment and injection pulse times that are not too

short. In this case the injection timing will have little effect at high RPM / Load because the

injector will be open most of the time, by the time it closes it is nearly time to open again.

Bigger injectors can be used which would give shorter injector duration at high speed and

take advantage of the benefits of timing the fuel, however this will cause a loss of resolution

and very short injection pulses at low speed. This will cause poorer idle quality and starting,

particularly when the engine is cold. An alternative to this is to use secondary injectors

(Hi/Lo).

Fuel Conditioning and Targeting

Most injectors deliver an atomized fuel spray, and some engines have injectors with a

spray pattern specifically tailored to suit the port / valve / injector location for that engine.

Some motor sport injectors do not have a spray pattern at all and just squirt fuel in a straight

beam. This may not seem like a good idea but where high quantities of fuel are required

(particularly when using methanol) it is an effective way of getting a large quantity of fuel

into the engine but it relies on swirl in the combustion chamber for good mixing.

Injectors which target fuel directly on to the back of the inlet valve will provide the

best control of fuel mixture and response to transient changes. Engines with this type of

injector layout will respond very well to injection timing where the injection takes place with

the inlet valve open. The deviation from desired air fuel ratio will be reduced with this layout

because there is little or no port wetting. The injectors ability to atomize fuel is critical in

this instance because there is no time for the fuel to atomize in the intake manifold. Although


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this will not effect the mixture stability it may mean that there is higher levels of un-burnt

hydrocarbons in the exhaust emission. Timing the injection pulse with the inlet valve closed

(exhaust stroke) will improve fuel atomization but deviations from the desired air fuel ratio

will be greater because of the effect of the fuel layer that is created on the port wall.

Some engines used in Motorsport have injectors mounted on the air intake side of the

throttle. Typically these injectors would be mounted roughly 250 mm away from the valve.

Gains in engine performance can be found at higher RPM with this arrangement, this is partly

because the fuel has more time to atomize before it reaches the engine. There is also a slight

cooling effect generated by the atomized fuel (stand off)in the intake. The disadvantage of

this is that there is a large area of the inlet covered by a film of fuel which leads to problems

with deviations from the desired air fuel mixture when accelerating and decelerating. Other

common problems with this arrangement are fuel stand-off (reversion) and the risk of air box

fire. Injection timing can be used to reduce and help control stand-off but is more effective

with shorter injector durations.


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Idle Stability

Injector timing will have an influence on idle stability as well as tail pipe emissions. It

is expected that fuel mixtures need to be a little bit richer at idle and at low load than at

cruising speed but this can be minimised by injector targeting and timing. This will vary

depending on engine design but is significant particularly when using a closed loop idle

control system.


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Setting the timing

Look closely inside the distributor, inside the cap base, you will see the number 1

molded into the cap and into the base. These obviously indicate the number one piston in the

compression cycle. In the second picture you can see how I recommend marking the

distributor base. First I highlight the 1, then after I get the engine timing set perfect at 10 I

mark that position with a short fat line that lines up with both edges of the rotor. Then I

remove the distributor and mark a longer skinny line that shows where the rotor should be

pointed before the distributor is dropped into the block. All these marks may seem like

overkill, but it is my web site and these are the best ways to do the job. Youll thank me later

when it saves time on distributor work if the need arises in the future.

Before you install the distributor make sure the engine is at TDC for cylinder one, and

you have mounted the TFI to the side of the distributor. Drop the distributor so the rotor is

aligned with that 1 molded into the cap. Note that the actually positioning of the distributor to

the block is not important; we are aligning the rotor inside the distributor with that 1. Make

sure there is enough room to rotate the distributor in the block 1/8th turn. You will need to

rotate it to set the base timing of 10 before TDC


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How To Check And Setting Timing

1. Insure the key is OFF position

2. Place transmission in PARK or NEUTRAL, A/C and heater in OFF position.

3. Connect timing light.

4. Disconnect the single wire in-line SPOUT connector or remove the shorting bar from the

double wire SPOUT connector. Examples of the SPOUT connector:

SPOUT connector on our EFI harness:

SPOUT connector on Remote TFI vehicles may be on the inner fender:

5. Start the engine. To set timing correctly a remote starter should not be used. Use the

ignition key only to start the vehicle. Attaching a remote starter might disable or initiate the

start mode timing after the vehicle is started.

6. Read the timing from the engine dampener on the crank.

7. If the timing does not read 10 before TDC continue to step 8, if timing matches 10 before

TDC skip to step 10.

8. Shut engine OFF, and loosen distributor enough so you can twist it with your hand. Do not

loosen it to the point where the engine rotation moves the distributor.

9. Re-start engine and twist distributor to a point where 10 can be read aligned with the

timing pointer.


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10. Shut engine OFF, reconnect SPOUT connector, and insure the distributor hold down bolt

is tight.

11. Re-start engine.

12. Check timing advance to verify distributor is advancing beyond the initial setting. (This

confirms Computer control)

13. Shut off engine and remove test instruments.

timing injection

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