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, Tue, 14 Aug 2001 10:52:36
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Hello Kevin,
Well, basically you are correct, however I would argue that these cold start injectors will flow enough fuel to allow a slight increase in your boost level. What follows is a segment of an e-mail I recieved from Richard Lamb who runs ERL in the UK. This is what he says about the use of cold start injectors etc. (Quite long!)
The minimum setting for the MF2's pressure switch is 3 psi. It could mean that at 2099 rpm there is no fuel at all until the big rush of boost. at 2100 rpm - the MF2 is only beginning to injection fuel - and it may not be adequate. Si this is the reason for asking the threshold of the MF2.
The limitation of the MF2 dealing with low boost and low RPM is caused by the pressure switch and pressure switch alone. Most application for the MF2 is over 10psi. Your only solution to cure this problem would be installing a MAP sensor and max out the 2000-RPM potentiometer.
At present, set your pressure switch to 3 psi and hope that the fuel come in earlier and cure the leaning problem.
I don't believe that your problem is caused solely by the cold-start injector but the switch-on time for the cold start injector is quite slow compared to a fuel injector : here is a typical comparison -
Cold start injector: 4-5ms
16 ohm fuel injector: 1.8-2ms
2.5 ohm fuel injectors: 0.8-1ms
(closing time is approximately the same)
As you can see, the MF2 will start at around 2-3ms before incrementing, your cold start injector may not flow any fuel until the MF2 get to approximately 5ms.
The duty cycle for the mf2 is between 2ms to 12 ms (full injection). If you translate these range to fit into your cold start injection it will mean that the fuel will only flow between 5ms to 7ms ! ie- your cold start injector can never give progressive fuelling - audibly it may sound OK but mechanically it is all too much for the cold start injector to cope.
The cold start injector is just used as an On/Off fuel valve - not really suitable for accurate fuelling.
Pretty interesting reading!
To conclude I am going to replace my cold start injector with one from a 1993 9000 2.3T, and hopefully will see better results.
Angus
posted by 213.40.1...
, Tue, 14 Aug 2001 10:52:36
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