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Whats Ign Timing Supposed To Be At Idle ?


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Just boght a consult usb cable and nissan datascan software to see for myself how all the sensors are responding ... one thing that I noticed after the car properly warmed up is that at idle (rpm 750 or so) the ign timing sits at '5' solidly..

I thought this is supposed to be 15, or am I thinking of something else?

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I was under the impression it was supposed to be 15 too.

I'm really very keen on getting a consult cable / ecutalk cable too. Overall was it worth it for you, considering the other things you can read from your car?

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yeah worth it I reckon ..

Anyway, I've just googled and it looks like timing IS supposed to be 15 degrees at (warmed up) idle but mine is 5. WTF.

Double WTF comes from the fact that about a year ago when I had my ecu remapped by Toshi, he noticed the same thing and he said the car shouldnt even be running at such low ign timing .. I suspected the guys that changed my timing belt screwed it up. Anyway, Toshi reset it to 15 (but due to a dodgy timing light it was actually set to 17 degreees instead as we later found out)

..and now the double WTF, a year later ..I connect consult and my ecu says timing at idle is 5 instead of 15 degrees. Any ideas anyone?

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ok if timing is set to 17 deg at the cam (or is it CAS? I suck at these things..) for idle/base ..how can it be 5 deg inside the cpu? Something screwed up surely? Maybe this is the reason i can't get better than 17l/100kms economy (and not the lead foot ;D )

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No idea mate, could it be possible that it was still set way incorrectly in the first place? Or maybe when it was 'fixed up'? Has anyone else other than your regular mechanic done any work to your car as well?

I'm not sure if it's possible for the timing to just shift on it's own, unless something wasn't tight enough after setting it?

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nah I had Yavuz double check it with his (good) timing gun when i went in for service (shortly after the remap a year ago) and he confirmed its 17 degrees at the CAS .. btw, no one's ever tuned this car other than Toshi with the remap (timing/AFRs) and the timing belt was done by the dealer (who outsourced it to god knows who but this was close to 2 years ago)

Anyway, is it possible for the CAS to read 17 degrees and the ECU to think 5 degrees at idle ? And what effect would that have on my power/fuel consumption?

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ok just heard back from Toshi who said its feedback and normal for the ecu to display 5 degrees in neutral on idle ..apparently if I were to jack up the car and put it in first instead it would show 15 (or 17 in my case)

So all good ..case closed :happy:

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For the R34gtt - im unsure what the base timing should be however i would have assumed it would be around 15.

Once, on my 33, i felt it sluggish - checked the base timing and it was 12 instead of 15(factory spec).

However though, if yours was supposed to be 15, but set to 5, then you would def feel it the lack of response and power.

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I don't see how it's a case closed...

The ECU is getting a reading from the CAS that says the "Crank is at X degrees"

From this, the ECU does some awesome maths and goes "I've worked out after Y time, it'll be at Z timing where I'll fire"

Now, it's making it fire at "5 degrees BTDC"

But this 5 degrees before TDC is in relation to the CAS. Which is able to be MOVED in relation to actual TDC.

If you advance your CAS 10 Degrees, then add on the extra 5 degrees from the ECU, you'll have 15 degrees of actual ign timing.

What you have to remember, is what the ECU is putting out, is in reference to the CAS position, which can be adjusted in reference to actual TDC.

Your actual timing VS timing outputted via the ECU, are offset by how much the CAS is adjusted.

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The Rb25 have an idle ignition lookup table that is based on rpm error from desired idle speed. If your idle is higher than commanded idle than the timing will be reduced to get it back to the desired rpm.

Remove some bypass idle air with the adjustment screw and watch the timing go back up to 15. If you look I bet your AAC value is very low - possibly even 0. At a hot idle AC off you should have at least 20% Duty of the AAC vavle.

Thats why on these cars its imperative when checking the timing that your know what the ECU is commanding.

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I've just checked the logs and at hot idle at around 750-800 rpm, the AAC is at 32% solidly the whole time and ign timing at 5*

by the way this is a rb25det NEO6 (GTT) ..don't know if that makes any difference

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  • 8 months later...

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