High ohm injectors
20-05-2005, 11:51 AM
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I think they do ya know! zvhturbo, but there aint gonna be a great difference using low impedance Siemens injectors to low impedance Bosch Injectors, or is there, I could be wrong. 
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20-05-2005, 06:38 PM
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Originally Posted by Andreas
Define work 
Would it work?
20-05-2005, 06:58 PM
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Originally Posted by ImaRacing 700
...could you not just use resistors to bring it down to the lower ohm?
You need to add a 5 ohm resistor in parallel with EACH injector in order
for the WEBER ecu injector driver correctly
and to ensure the injector open/close events are as quick as possible.
This will provide more accurate fuelling for high impedance type injectors.
20-05-2005, 07:02 PM
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The primary advantage of low impedance injectors is a shorter triggering time. When large injectors are fitted to high output engines, low impedance injectors will often give a better idle quality because of this fact. The primary advantage of high impedance injectors is the fact that less heat is generated in the drive circuit and often no external resistors are used.
You shouldn't use high impedence injectors when the ECU is configured for low impedance injectors and vice versa. I believe you risk damaging the injectors and the ECU, or at least the injector drivers.
Resistors could be an option, but heat needs to be taken into consideration (or is that for running low impedance injectors with a high impedance ECU??). Better just to use the 'correct' injectors for the job, imo.
You shouldn't use high impedence injectors when the ECU is configured for low impedance injectors and vice versa. I believe you risk damaging the injectors and the ECU, or at least the injector drivers.
Resistors could be an option, but heat needs to be taken into consideration (or is that for running low impedance injectors with a high impedance ECU??). Better just to use the 'correct' injectors for the job, imo.
20-05-2005, 07:17 PM
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LOL, the first paragraph IS a quote as I couldn't remember which had the shorter triggering time. The rest is randomly plucked from my grey matter, lol.
21-05-2005, 08:57 AM
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Wouldn`t put a resistor in parallel.
The injector drive will pulse high then maintain a lower current to keep the fuel injector open.
A high impedance injector would then close due to the holding current being too low.
When testing my fuel injection firmware a signal that opened the 803 injector did almost nothing to a high impeadance injector, just a very quite buzzing, indicating it was thinking of opening!
Darren
The injector drive will pulse high then maintain a lower current to keep the fuel injector open.
A high impedance injector would then close due to the holding current being too low.
When testing my fuel injection firmware a signal that opened the 803 injector did almost nothing to a high impeadance injector, just a very quite buzzing, indicating it was thinking of opening!
Darren
21-05-2005, 11:01 AM
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turbodisplay,
You are right to a point BUT this is why I said 5 ohms and NOT the 2-2.5 ohms a normal injector is !!!!
This gets the hold open voltage high enough to maintain the valve open and which
allows a faster closing time.
Have actually done this with great success on 2 cars
You are right to a point BUT this is why I said 5 ohms and NOT the 2-2.5 ohms a normal injector is !!!!
This gets the hold open voltage high enough to maintain the valve open and which
allows a faster closing time.
Have actually done this with great success on 2 cars
21-05-2005, 12:15 PM
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What will interest me is if the pintle is still firmly seated when open, due to less voltage seen by the injector. Probally will, but seems a bit of a bodge.
What I should have pointed out that I was testing and only had 1ms (or less) opening time with a 10 - 20% duty cycle holding. It shows how much slower the HIGHs are at opening though!
Its this low holding current that results in the fast closing of LOW injectors.
I wouldn`t run these settings on the road.
At high flow rates the slower and less predictable opening time of HIGHs will cause a rough idle.
I`m going for LOW due to these advantages, even though the drivers will cost a stonking Ł5 more!!!!
Darren
What I should have pointed out that I was testing and only had 1ms (or less) opening time with a 10 - 20% duty cycle holding. It shows how much slower the HIGHs are at opening though!
Its this low holding current that results in the fast closing of LOW injectors.
I wouldn`t run these settings on the road.
At high flow rates the slower and less predictable opening time of HIGHs will cause a rough idle.
I`m going for LOW due to these advantages, even though the drivers will cost a stonking Ł5 more!!!!
Darren
21-05-2005, 12:31 PM
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Darren,
I agree 100%. Low inpedance IMO are the best.
VERY suprised the drivers are that much !!!
On my own designed ecu, the injectors are closed quicker using a short duration reverse voltage pulse.
(around 200 micro seconds)
This of course is kept within the injector power saturation levels.
Makes use of large injectors even more accurate to control.
I agree 100%. Low inpedance IMO are the best.
VERY suprised the drivers are that much !!!
On my own designed ecu, the injectors are closed quicker using a short duration reverse voltage pulse.
(around 200 micro seconds)
This of course is kept within the injector power saturation levels.
Makes use of large injectors even more accurate to control.
21-05-2005, 01:10 PM
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EMC is not an issue as the pulse rise times are controlled to prevent high frequency resonance.
(controlled by using a capacitor and dual polarity semiconductor suppression zener diode.)
The reverse energy EMF pulse from the injector has much more chance of causing radiated issues than the ecu driver stage.
Needless to say, it was a pain to get the original design through the CE conformance tests.
(controlled by using a capacitor and dual polarity semiconductor suppression zener diode.)
The reverse energy EMF pulse from the injector has much more chance of causing radiated issues than the ecu driver stage.
Needless to say, it was a pain to get the original design through the CE conformance tests.
21-05-2005, 02:18 PM
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So it is more like a clamp than a negative pulse?
I usually use a resistor in clamps as i find the rfi energy is disipated in the resistor.
Won`t be as efficient as a clamp but much better at reducing rfi.
Darren
I usually use a resistor in clamps as i find the rfi energy is disipated in the resistor.
Won`t be as efficient as a clamp but much better at reducing rfi.
Darren
21-05-2005, 02:49 PM
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Darren,
The driver works like this ....
High current for at least 0.7 ms then fold back voltage to hold in current (closed loop current control).
This causes back EMF when the voltage is reduced.
When the ecu, decides to close the injector, a capacative discharged pulse is applied
to slam shut the injector other than just turning the output off.
(This equates to about minus 10 volts for about 200 micro seconds)
This pulse in it self creates back EMF voltages.
So the whole output stage is clamped @ 150 volts positive (Reduce EMF of inj coil) this is high enough to prevent the reverse voltage from cause the injector to slow down when closing.
And is clamped to about -50 volts (50 volts below gnd).
Also, there is a capacitor in the circuit to slow all these pulses down enough to prevent coil resonance/oscilation and the problematic RFI.
Hope I explained that enough.
BTW, if you use a resistor to clamp, this will actually SLOW down the close
time as the self generation effect will hold the coil charged longer. !!!
The driver works like this ....
High current for at least 0.7 ms then fold back voltage to hold in current (closed loop current control).
This causes back EMF when the voltage is reduced.
When the ecu, decides to close the injector, a capacative discharged pulse is applied
to slam shut the injector other than just turning the output off.
(This equates to about minus 10 volts for about 200 micro seconds)
This pulse in it self creates back EMF voltages.
So the whole output stage is clamped @ 150 volts positive (Reduce EMF of inj coil) this is high enough to prevent the reverse voltage from cause the injector to slow down when closing.
And is clamped to about -50 volts (50 volts below gnd).
Also, there is a capacitor in the circuit to slow all these pulses down enough to prevent coil resonance/oscilation and the problematic RFI.
Hope I explained that enough.
BTW, if you use a resistor to clamp, this will actually SLOW down the close
time as the self generation effect will hold the coil charged longer. !!!
21-05-2005, 03:41 PM
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A good value of R will disipate the energy as heat and still not hold the coil on much longer.
Am i correct that with any value of r, the coil will close quicker than no resistor at all?
From experimentation i find that in any case.
Darren
Am i correct that with any value of r, the coil will close quicker than no resistor at all?
From experimentation i find that in any case.
Darren
21-05-2005, 03:49 PM
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Any resistance that is effictively accros the injector will ultimately feed the EMF voltage back into the coil creating additional magnetic hold in.
(I know this goes against my parallel resistor suggestion at the start of this thread but we are now talking low impedance injectors)
The quickest way to close an injector without reverse voltage forcing it is to just open circuit it !
In this sitauation, you do NOT want to clamp the voltage too soon which is why the clamp voltage is around 150 to 200 volts !!
RFI is prevented by adding a suitable high frequency capacitor to slow down the high frequency component rise times.
Dont forget any hold in time will manifest it self on larger injectors as these require very short durations.
If you measure any ecu injector output, it will have no significant resistance when turned off when measured relative to the positive supply.
(I know this goes against my parallel resistor suggestion at the start of this thread but we are now talking low impedance injectors)
The quickest way to close an injector without reverse voltage forcing it is to just open circuit it !
In this sitauation, you do NOT want to clamp the voltage too soon which is why the clamp voltage is around 150 to 200 volts !!
RFI is prevented by adding a suitable high frequency capacitor to slow down the high frequency component rise times.
Dont forget any hold in time will manifest it self on larger injectors as these require very short durations.
If you measure any ecu injector output, it will have no significant resistance when turned off when measured relative to the positive supply.
21-05-2005, 09:01 PM
#37
just finding my feet
sorry i started reading it and got soo lost and so asked the question i could remember 
hes tooo techy is simon , imagine pub talk with him and billabong , id just sit there drinking coke and still feel drunk
hes tooo techy is simon
, imagine pub talk with him and billabong , id just sit there drinking coke and still feel drunk
21-05-2005, 09:04 PM
#38
just finding my feet
Originally Posted by ImaRacing 700
...could you not just use resistors to bring it down to the lower ohm?
then it all went into reasons why and then it went into r values and oracles and the neo was the chosen one and i noticed the matrix was infront of me
21-05-2005, 09:10 PM
#40
just finding my feet
Si i need to ask ya some advice but im too afraid i wont understand the answer
its a simaler thing to when you lot read my posts , but yours makes sence to others 
but i do need a tiny weeny bit of advice if i ya dont mind , ill do it via PM as its also secret
its a simaler thing to when you lot read my posts
, but yours makes sence to others but i do need a tiny weeny bit of advice if i ya dont mind
, ill do it via PM as its also secret