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Z32 Igniton Dwell Duty

Mr Jollwah

By Mr Jollwah,
in Engines & Forced Induction

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Mr Jollwah Community Regular

Mr Jollwah

Posted
  • Author
Posted

Interesting,

Didn't think this topic would surface again.

I had the too many points in my charts before ^^60 not ^^6F, there are only 16 points not 32 thus the rpm scale is in 400 rpm increments.

The divide by 10 to convert to dwell % was gleened for some ecu tuning forum somewhere.

This appears not to be the case thankfully as 25.5% seemed to be max dwell duty % before.

so i guess i need to work out the constant to convert from ecu values in dec to dwell duty %.

will post back later.

  • 2 years later...
ST240 Enthusiast

ST240

Posted
Posted

Bump.

I know this thread is old, but I'm going to be doing an LS2 coil swap in favour of the garbage RB20 coils I'm running on my RB30.

Can anyone explain the correlation between dwell duty cycle and actual dwell time so i can set them up properly?

kjb_r33 Experienced

kjb_r33

Posted
Posted
Bump.

I know this thread is old, but I'm going to be doing an LS2 coil swap in favour of the garbage RB20 coils I'm running on my RB30.

Can anyone explain the correlation between dwell duty cycle and actual dwell time so i can set them up properly?

They are 2 different things. If frequency didn't change then there would a correlation between the 2 but because frequency increases (with RPM), then duty cycle must increase to achieve the same ON time (in milliseconds) in order to reach coil saturation.

The pic shows that duty cycle has to increase as rpm increases, simply because we have less time.

post-536-1286344473_thumb.jpg

kjb_r33 Experienced

kjb_r33

Posted
Posted (edited)
Ah ok... Makes sense. Do you know if i can even adjust actuall dwell to suit other coils then with nistune?

That pic i posted was from nistune. You can adjust it, but if you add too much duty cycle you will just burn out coils.

Millisecond adjustments with nistune are simply to compensate for lower battery voltages. Duty cycle adjustments are for the on time, which will increase as rpm rises.

Easiest way to find out what is required is to hook coil up to a scope, you will see when full saturation is acheived because current will stop climbing and level out.

Otherwise, provided the primary winding are resistances are massively dissimilar, i would just leave them.

Edited by kjb_r33
ST240 Enthusiast

ST240

Posted
Posted (edited)
That pic i posted was from nistune. You can adjust it, but if you add too much duty cycle you will just burn out coils.

Millisecond adjustments with nistune are simply to compensate for lower battery voltages. Duty cycle adjustments are for the on time, which will increase as rpm rises.

Easiest way to find out what is required is to hook coil up to a scope, you will see when full saturation is acheived because current will stop climbing and level out.

Otherwise, provided the primary winding are resistances are massively dissimilar, i would just leave them.

Thanks a lot man you've been super helpful. The thing is, I'm going from R32 coils to LS2 coils which have a WAY higher spark energy and a significantly different dwell time (I think), I guess I'll just play with it slowly. Heres some interesting data on the coils I'm using: http://www.megamanual.com/seq/coils.htm

Do you know what the "nominal dwell" would be on the stock coils?

Edited by ST240
kjb_r33 Experienced

kjb_r33

Posted
Posted
Thanks a lot man you've been super helpful. The thing is, I'm going from R32 coils to LS2 coils which have a WAY higher spark energy and a significantly different dwell time (I think), I guess I'll just play with it slowly. Heres some interesting data on the coils I'm using: http://www.megamanual.com/seq/coils.htm

It actually states on there to use no more than 6 milliseconds. It also states that the millisecond compensation is for dropping battery voltages. (both can be adjusted with nistune).

Id be inclined to get them wired up, then adjust the dwell duty cycle to achieve the 6ms.

This will give you max coil output at a duty cycle thats not going to shorten coil life excessively.

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