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[s.mac]

you asked Jim now you are FoOKInG confused













it takes far less than that to lose Jim Gorilia

[shane@mbtech]

Originally Posted by The Gorilla

Hi,

NortherJim- This explains the basic paramiters.

Save me from typing it all out !!

'''There are a few important factors that you must take into account when modifying an electronic fuel injection engine. These are: the pulse duration of the injectors and the duty cycle.

The injector pulse duration is the amount of time that the injector is held open so that it can inject fuel into the combustion chamber. The pulse duration is controlled by the engine control unit (ECU) and is dependent on various sensors in the electronic fuel injection (EFI) system. The longer the pulse duration, the more fuel is added to the air/fuel mixture. The amount of fuel required at any one time varies by the amount of air flow, the air density, the engine load, and the engine temperature. Therefore the pulse duration will vary. However, there is only a limited amount of time that the injector can be held open at each revolution of the engine. This amount of time is reduced as engine speed increases. For example, at 600 RPM the available time is 0.1 seconds (60 seconds in a minute divided by 600 revolutions) but at 6,000 RPM it is only 0.01 seconds. The pulse duration relative to the available time at the engine red line is called the duty cycle and is expressed as a percentage. Thus a duty cycle of 80% means that at the engine red line the pulse duration (the amount of time the injector is help open) is 80% of the available time.
INCREASING THE DUTY CYCLE

Some engine tuners will tell you that if your car has a duty cycle of 80%, you have a possible gain of 20%. However, the injector is an electronic solenoid and cannot be held open for too long or it will overheat and fail. In practice most Nippon Denso and Rochester injectors will remain reliable at up to an 80% duty cycle; most Bosch injectors will remain reliable at up to an 85% duty cycle; and most Lucas injectors will remain reliable at up to a 92% duty cycle. Though even at these duty cycles it is still advisable to test the injectors. Test them specifically for their spray pattern and their flow volumes at the maximum duty cycle you require.

On a race engine I wouldn't exceed a maximum duty cycle of 80% as dyno-testing on various have shown that a duty cycle in the region of 60% to 70% produces the best power. This is because a shorter duty cycle does not allow for the proper atomization of the fuel, and proper atomization is important for the proper burning of the air/fuel mixture. I usually aim for a duty cycle at the point where maximum power is reached so as to ensure the longevity and reliability of the injectors. So, how do you adjust the duty cycle? By adjusting the fuel pressure and the injector nozzle size. On an OEM EFI system there are certain limitations on increasing the fuel pressure and the injector nozzle size. I'll discuss increasing the injector size in a while, but you can read more about increasing fuel pressure here.
INCREASING INJECTOR NOZZLE SIZE

Increasing the injector nozzle size will result in increased fuel delivery all the time. As "Langer" mentioned in engine basics, a rich fuel mixture results in power loss. Therefore, increasing the nozzle size could have a negative effect on performance and economy. The oxygen Sensor (O2S) will correct the fuel mixture for an injector that is about 20% larger than stock. However, on a pre-1996 EFI system, the ECU will ignore the O2S sensor under full throttle conditions. Furthermore, the OEM ECU will not be able to handle an injector that is more than 20% larger than stock and will suspect that one or more of its sensors are faulty and will revert to its programmed settings, which means that the fuel air mixture will not be optimal and will probably be rich as this is the failsafe setting on the ECU when it suspects that its sensors are faulty.'''''




Without going into specific Calculations,
at 85% of their Duty cycle running at
6 Bar fuel pressure [86 psi] + 1 Bar
over std, which is very high, then the
std S54/CSL injectors are capable of a fuel
poundage which equates to around
370/380 BHP on a L6 engine.

Reducing the Injector Duty cycle down to say
70/75% for a performance Race engine
High lift Cams, 12.5 CR and so on, would
equate to around 370 BHP at very best.

Its why the Fuel Injectors of the F430,
carried over from the Enzo and used in the 458
are regarded as one of best as they
use a a 5 nozzle arrangement giving immense
spray volume but without really fine atmoization
which for a high performance engine is
exactly what you really want.

Its also why back in the days of the 'real' DTM
era, 4 pots started running 8 injectors, as
the sequential injection with the second bank
of 4 mounted further up the Intake runner,
coming in at say 6000 rpm would keep
the fuel atomization from going to fine
right when the engine was making peak
power..

Regards,

The Gorilla.

Good post G man, but please stop teaching these numb nuts too much- what is it they say..... a little knowledge is a dangerous thing.

[northernjim]

Originally Posted by s.mac

you asked Jim now you are FoOKInG confused













it takes far less than that to lose Jim Gorilia

C unit!

Originally Posted by lawsy

Good post G man, but please stop teaching these numb nuts too much- what is it they say..... a little knowledge is a dangerous thing.

I have already said that

tbh I was talking more about the AFR's, which once the injectors max out when you turn the 'wick'( technical term for you there steve go look it up) up a bit, will surely lean the engine off with a result of more power ( not neccessarily safe long term power I add)

[titan]

Now thats what I call a post, cheers for that found it very useful.

[alexk]

Originally Posted by The Gorilla

Its also why back in the days of the 'real' DTM
era, 4 pots started running 8 injectors, as
the sequential injection with the second bank
of 4 mounted further up the Intake runner,
coming in at say 6000 rpm would keep
the fuel atomization from going to fine
right when the engine was making peak
power..

Regards,

The Gorilla.

Gorilla, excellent post !

Also, this is the case with superbikes like my RSV4 factory, they are running 8 injectors.