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Rb25det neo set timing

joz

By joz,
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joz Apprentice

joz

Posted
Posted

Hi all, today i was trying to verify my base timing and ran into some issues. 

At idle with tps connected, it was running 15 deg from timing light.

I then unplugged the tps which is supposed to lock it to 15 deg. The revs went up and the engine was then pinging. Timing light showed no marks but i guess it was very advanced since it was pinging.

I then turned the cas to maximum full clockwise which is max retard and the pinging stopped but timing light shows 20 deg. Could not get it down to 15 deg.

I then put back the tps and the revs dropped to around 600? Rpm and no marks again on the crank so i assume it was now extra retarded.

I don't think ecu idle adjustment can take many degrees off to adjust the idle.

But anyway with the tps in i set it to 15 deg and it idles at 1000 and runs fine. However i worry that timing is off and during pulls the timing is actually very advanced and byebye engine.

Should i keep it like this or actually find a way to set timing to 15 deg with the tps disconnected?

To achieve that can i remove cas and install it again to get more adjustments so i can put it to 15?

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GTSBoy Grand Master

GTSBoy

Posted
Posted

What you describe really shouldn't be possible.

You can't pull the CAS and put it back at any other angle than that which it came off of, because there's only one install orientation. So no go there.

For your timing behaviour to be so weird, one would have to hypothesise that your exhaust cam is one tooth off, or something similar.

A satisfactory idle speed for a Neo is <650 rpm.

And I have seen ECUs that can't get the idle under control by IACV pull the timing back to nearly 0° timing. So there is really about -ve 15-20° of delta timing available for idle control and then possibly more on the other side too.

joz Apprentice

joz

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  • Author
Posted (edited)

Wow, I'm very delighted to have your reply. I have read a lot of threads about this and seen your posts a lot. 

I think you had a post where you had a screenshot of the Nistune maps on idle adjustments and I vaguely remember seeing the maximum adjustment that the ECU can make to try to achieve the target idle is perhaps +/- 3? Didn't know they can pull or add that much delta. Also, is it possible to reset this learned advance/retard?

 

My iacv screw (black plastic) is worn and adjustments are very difficult so to use that to set to 650 RPM is not very easy. As well, as mentioned, with the TPS off max retard I can get is 20 deg which will pull the RPMs up given the same amount of air.

Workshop manual says put to iac/aac adjust. mode in Consult. What does that actually do? Put iac valve to base duty?

 

I have just ordered a consult cable and will read the ECU's timing and try to adjust CAS to the same. If it is not possible then I guess it's jumped a tooth and belt/pulley work time to align the cams to crank?

 

Thanks in advance.

Edited by joz
GTSBoy Grand Master

GTSBoy

Posted
Posted

I have personally seen my car idling at 3° when the IACV was dirty and non-responsive. As reported by the ECU in Nistune.

 

1 hour ago, joz said:

Workshop manual says put to iac/aac adjust. mode in Consult. What does that actually do? Put iac valve to base duty?

I connect to my ECU with Nistune (because it is Nistuned) and you can set the target idle rpm directly, which is what you can do with a proper Consult device. I would not expect that you can set the idle speed with your typical Consult reading software on a PC. Might be able to with some, but that requires a ton more confidence on the part of the person releasing the software!

The IACV is essentially a stepper motor and how many "steps" the ECU is putting out is the requested opening. I think it is open loop, so if the IACV won't actually open (because dirty/broken) then I think the steps will just keep increasing until they hit the max. A realistic number for the output number of steps is something in the order of 50.

Setting the idle speed is a juggling act between making a physical adjustment on the screw on the IACV so that the ECU can run the stepper motor in the middle of its useful control range so that it can maintain the correct speed across the full range of load and temperature variations you can expect.

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joz Apprentice

joz

Posted
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Posted

Took took timing cover and put crank to TDC and marks on cams line up so no tooth skipping here.

Decided to try wiring a loop on spark plug #1 and putting the coil back on and taking the timing gun signal from there.

Initially showed the same as getting the signal from the blue loop in the back. Then gun decided to die and I could not go any further.

TPS off full retard on CAS is 20 deg.......

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