Nissan ECU Tuning

cb_drift · Joined: 04 May 2004 Posts: 468 Location: New Zealand

can someone who has dissassembled the code please answer a few questions for me bout it? =)

why does the ca have 4 rev limiters - what exactly does each limiter value do when you change them?

where is the value in the rom that can change the length of time the ecu does a revcut for when you hit your revlimiter? I need to change this time to be MUCH less - more like the rb20 revlimiter...

Quite happy to give lots of my rom collection (quite a decent one) for this info or information about other roms that i have that someone else might not..

many thanks for your time

lawrence

ivar.mosch · Joined: 14 Sep 2005 Posts: 28 Location: Netherlands

Hmm.. I’ve no disassemble knowledge unfortunately…sorry..

But a long time ago I read somewhere it has to do with the high and low fuel and ignition maps…

first limiter = High octane fuel map
Second lim = High octane ignition map
Third = low oct fuel map
Fourth = low oct ign map

Unfortunately I don’t know if there’s any truth in this… Shocked

Maybe someone can shin a light on this theory?? Very Happy

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datsunboy · Joined: 26 Jul 2005 Posts: 209 Location: New Zealand

never heard that theory before, but it sounds very possible!

except why would there be a different limiter for IGN and fuel?
_________________
1970 Datsun 1600 CA18DET Project

The point of life is not 2 arrive at your grave all preserved & in mint condition, but 2 slide in sideways, scratched & bruised screaming F**K WHAT A RIDE!!

maff · Joined: 02 Nov 2006 Posts: 12

I read on the sxoc that its a soft and hard limit for the low and high octane maps

see here : http://www.sxoc.com/vbb/showthread.php?t=250065&highlight=rev+limit
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Adamo · Joined: 14 Apr 2004 Posts: 55 Location: Hungary

Sorry to dig this old topic, but do someone know by any chance if there is a possibility to change the behavior of the rev limit of the CA engine? I mean to make it smoother, like for example in the P10 Primera (I know it is not the same as it has SR20DE engine).
I would like to lower the hysteresis between the cut and recovery revolutions. If it works in this way at all... Or is it work to cut the fuel for a given period of time?

cb_drift · Joined: 04 May 2004 Posts: 468 Location: New Zealand

apparently there is a way to make it work like an sr limiter - but I have not tested it - so *shrug* dunno if it would work or not - and it probably needs tweaking depending on what revs you want to limit at...

rumor has it you reverse the limiters
eg at the moment you have for example
7950
8000
7950
8000

try setting to
8000
7950
8000
7950

untested rumor is all.....
if you try it - let us know - i'll test it next time ive got my hands on a ca

datsunboy · Joined: 26 Jul 2005 Posts: 209 Location: New Zealand

someone please test this Cool

the CA rev limiter isnt very cool lol
_________________
1970 Datsun 1600 CA18DET Project

The point of life is not 2 arrive at your grave all preserved & in mint condition, but 2 slide in sideways, scratched & bruised screaming F**K WHAT A RIDE!!

Adamo · Joined: 14 Apr 2004 Posts: 55 Location: Hungary

Adamo · Joined: 14 Apr 2004 Posts: 55 Location: Hungary

We tried this reversed setting. There was 50 rpm between the hard and soft cut. It gave a bit smother revlimit, but the difference isn't much. Any more idea is welcome. Wink

darkhalf · Posted: Wed Apr 02, 2008 4:14 am Post subject:

Apparently you use Rev1/Rev3 together and Rev2/4 together

One couple is soft cut and the other hard cut

I've tested this on the bench about 100rpm apart from each other

datsunboy · Joined: 26 Jul 2005 Posts: 209 Location: New Zealand

whats soft and hard cut actually mean?

is it just the lowe and upper revs that it limits between?
ie....cut revs at 7200....then regain revs at 7000 e.t.c.?
_________________
1970 Datsun 1600 CA18DET Project

The point of life is not 2 arrive at your grave all preserved & in mint condition, but 2 slide in sideways, scratched & bruised screaming F**K WHAT A RIDE!!

cb_drift · Joined: 04 May 2004 Posts: 468 Location: New Zealand

Soft cut - a rev limiter that will prevent the engine from revving on light throttle - maybe an ignition retard, maybe dropping cylinders

Hard cut - the engine will not rev past this - to prevent excessive revs you can get full fuel or ignition cuts

combined - what happens is the engine revs - then hits soft cut and slows its revving - then hits hard cut and stops revving until the revs pass below the hard cut again

ca's have a crappy hard cut that takes about 3/4 of a sec to return....
not good if you are trying to hold the revs for whatever reason Smile

datsunboy · Joined: 26 Jul 2005 Posts: 209 Location: New Zealand

ah cool....good to finally know lol
so is there any "good rules" for setting the soft cut in relation to the hard cut?
say 100rpm apart? 50rpm apart?

yeah the CA rev limit isnt all that great sounding!.......so theres no way to change it?
putting soft and hard cut at the same value......would that do anything?
_________________
1970 Datsun 1600 CA18DET Project

The point of life is not 2 arrive at your grave all preserved & in mint condition, but 2 slide in sideways, scratched & bruised screaming F**K WHAT A RIDE!!