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I have just purchased a set of R35 coils for my RB26.
The instructions require a change of dwell time.
I am running a Power fc and a datalogit unit.
However, i am unsure what figures/ numbers i should change for this to work.
Attached is a screen shot of the datalogit dwell setting for std rb26 coils and the dwell table for R35 coils.
Any help would be greatly appreciated.
Thanks in advance
The ign vs battery voltage is a multiplier which is why it is 1 at 14V as this should be pretty well your normal system voltage. The other table is crank degrees at various engine speeds.
To do the conversion you divide 60,000 by rpm to get available milliseconds per 360 degrees. If you want to convert ms to crank degrees at a certain rpm it will be crank degrees dwell= 360 x desired ms/available ms per revolution.
Or dwell degrees= 360 x (dwell in ms) x rpm/60000
Obviously there are physically limitations, 2 stroke or rotary you need to fit both dwell and discharge time within 360 crank degrees, sequential 4 stroke in 720 degrees, being mindful sustained high duty cycle will kill most coils.
Thanks Slides for your prompt reply,
From your reply, i gather that we keep the ign vs battery voltage as it is.
Keeping the 14V as the normal system voltage, that would give a dwell time for the R35 coils to be 3.8 ms.
Therefore the valve of 3.8ms form your fomula would result in
10000 rpm: 228
8000 rpm: 182
4000 rpm: 91
2000 rpm: 46
1000 rpm: 23
480 rpm : 11
Does this look right?
Like you mentioned, I do not want to kill the coils.
Yes that looks the same as my calculation sheet.
I used the above dwell table on my 2JZ running R35 coil packs with the PowerFC and it basically behaves like an early rev limiter at 4250rpm.
I changed the values to 2.8 - the rev limiter effect was the same, but moved to 6250rpm.
Using the stock values for the stock dwell, around 1.7-1.8 proved to work well and there was no rev-limit effect.
I'm not sure what is going on, but those values didn't work for me at all and the stock ones did.
I run anywhere from 2.8-3.8 on aftermarket ECUs so I know the coils are good for it, but perhaps the way the PFC handles dwell is archaic...
First: PFCs/Datalogits are somewhat archaic and esoteric in nature. Sometimes dealing with them is voodoo with their poor documentation.
Second: Since you're essentially chopping your dwell time in half I'd confirm that you're actually running DFI with your individual COP and not waste spark, since I'm not familiar with your flavor of box, how many discrete ignition ouputs does it actually have?. I'd also confirm voltages when you're seeing that rev limiter, a global 25% increase of dwell at 12 volts isn't insubstantial.