PFC & 6 injectors !!
#12
Ask and you shall recieve...
T-2 How to add a pair of additional 550 secondary injectors ^
o Plumb 2 extra series 5 (Gen2 T2 FC3S)-550 cc injectors into a
spacer between the inlet manifold and the plenum chamber,position
them to inject into the secondary runners.This Spacer /Auxiliary
injector holder will be available from FC-Datalogit soon.
o The series 5 (Gen2 T2 FC3S)550's are high impedance (15 ohm)so
they can be driven in parallel with the existing 850 secondaries.
o The injector drivers in the PFC are FETs.The IC contains 4
separate FETs,rated at 0.25ohm on
resistance and 3W max power dissipation for all 4.
o Driving 1 x 15 ohm injector at (say)15V BatV is 1A,so power per
FET is I ^2R =0.25W.Therefore the total power on the driver chip is
1W (at 100%injector duty)To drive the 2 secondaries together will
be 2A,and therefore power will be I ^2R =2 ^2*0.25 =1W.So the
total power for 2 primaries +4 secondaries will now be
0.25+0.25+1+1 =2.5W which is ok for the chip.
The result (FC-Datalogit team road test)was excellent.No
noticeable injector transition glitch's.Same smooth power at 1.0bar,
and injector went duty from 95%to 70%
o Note at 70%,the injector driver chip will only be dissipating
0.7*2.5W =1.75,which is fine.We plan to add a clip on heat-sink to
the chip though -all the same.You may wish to do that also.
o We also intend to scope the injector circuit -since you should really
modify the snubber circuit also.This consists of 33ohm in series with
0.47uF capacitor to ground.In theory we should halve the resistor
and double the capacitor to achieve the same.This could be modified
in the PFC,or added externally.We will explain more latter.
T-2 How to add a pair of additional 550 secondary injectors ^
o Plumb 2 extra series 5 (Gen2 T2 FC3S)-550 cc injectors into a
spacer between the inlet manifold and the plenum chamber,position
them to inject into the secondary runners.This Spacer /Auxiliary
injector holder will be available from FC-Datalogit soon.
o The series 5 (Gen2 T2 FC3S)550's are high impedance (15 ohm)so
they can be driven in parallel with the existing 850 secondaries.
o The injector drivers in the PFC are FETs.The IC contains 4
separate FETs,rated at 0.25ohm on
resistance and 3W max power dissipation for all 4.
o Driving 1 x 15 ohm injector at (say)15V BatV is 1A,so power per
FET is I ^2R =0.25W.Therefore the total power on the driver chip is
1W (at 100%injector duty)To drive the 2 secondaries together will
be 2A,and therefore power will be I ^2R =2 ^2*0.25 =1W.So the
total power for 2 primaries +4 secondaries will now be
0.25+0.25+1+1 =2.5W which is ok for the chip.
The result (FC-Datalogit team road test)was excellent.No
noticeable injector transition glitch's.Same smooth power at 1.0bar,
and injector went duty from 95%to 70%
o Note at 70%,the injector driver chip will only be dissipating
0.7*2.5W =1.75,which is fine.We plan to add a clip on heat-sink to
the chip though -all the same.You may wish to do that also.
o We also intend to scope the injector circuit -since you should really
modify the snubber circuit also.This consists of 33ohm in series with
0.47uF capacitor to ground.In theory we should halve the resistor
and double the capacitor to achieve the same.This could be modified
in the PFC,or added externally.We will explain more latter.
#13
now sombody who understand electronics better than me tell me if it can handle 3 low impediance (4 to 5ohm) injectors in series = 14-15 ohms (same ohms as the stock secondary) on each of the secondary power wires + 2 stock high (15 ohm) primary injectors... for a total of 8 injectors...
#16
I tried running two stock 850's in the primary and 4 low impedence 850's on the secondaries and it would not work. I just bought a haltech for this reason. I know from experience not just guessing. And I also tried several different resistors with no luck. The low impedence injectors draw too much current and will not open properly. I can only assume that when you are just running a pair of 1600's in the secondaries, the circuit can handel the current but when you have 4 low impedence injectors you have doubled the current again and therefore will fry the PFC or not open the injectors. Don't know if this helps much but I thought I would share my experience.
Nick
Nick
#17
I am installing a set of 1600 secondaries as we speak but the only resistors I got locally were 10 ohm 2 watts ..not the 10 ohm 1 watt that most folks use.. I spoke to a friend who is a elector-geek and he told me that it shouldn't be a problem... the 2 watt just means that those resistors can handle more voltage.
any thoughts on this ??
TIA,
3G7
any thoughts on this ??
TIA,
3G7
#18
Originally Posted by 3rdGen7' date='Feb 8 2003, 06:04 AM
I am installing a set of 1600 secondaries as we speak but the only resistors I got locally were 10 ohm 2 watts ..not the 10 ohm 1 watt that most folks use.. I spoke to a friend who is a elector-geek and he told me that it shouldn't be a problem... the 2 watt just means that those resistors can handle more voltage.
any thoughts on this ??
TIA,
3G7
any thoughts on this ??
TIA,
3G7
mike
#19
Spoke to XS Eng and they said you can use the 10 ..heck even the 20 watt..just means that they will be able to handle more power.
Something interesting they said:
Even though most folks use 1 watt that is fine for most applications and driving around the street etc... but if you're running big boost and a drag launches.. you are better off going with something like a 20 watt ! ..it's an over kill but a safety margin you'd not have to worry about.
Just something to think about.
3G7
Something interesting they said:
Even though most folks use 1 watt that is fine for most applications and driving around the street etc... but if you're running big boost and a drag launches.. you are better off going with something like a 20 watt ! ..it's an over kill but a safety margin you'd not have to worry about.
Just something to think about.
3G7