What RPM does the RB20 have to be at to time it properly? Car hates to start,etc

[goofynick6]

I've been trying to get my car to idle right and not stall out all the time lately, but I am not sure I'm doing it right.

I have the R33 RB25 and 26 manual, and each RB has to be at a different RPM to time it properly..so I was wonder at what RPM does the RB20DET have to be at to set it to 15 deg?

ALso, I checked timing AT the coil and at the loop thing and they both read the same, but Wulfgang said they are supposed to be 10 degrees difference.

Everytime I am cruising along and come to a stop, when I push the clutch in, the car just dies. The IAC works, but seems only sometimes. When I turn on the defroster, the idle jumps from 800 to 1200....so I always have it on because the car is less likely to stall with it on

Also, the car doesn't like to start up, it takes 3 tries and then I have to pump the gas pedal to get it to come to life unwilllingly.

Thoughts?

[Joe]

since you are just setting base timing its done at idle.

all of the ignition timing for RB's is controlled by the computer, so the only thing you can do is set a refrence for the ECU to go on. it will adjust the timing itself as it sees needed.

[goofynick6]

This is obvious, I'm wondering what rpm is considered idle, since mine doesn't idle properly.

[Joe]

whatever the engine idles at is considered idle lol, it actually changes with timing (at least on the 25) 1000, 750, 800, etc. just set it at whatever the engine sits at.

[goofynick6]

Well in the R33 manual, for the rb25 it says set it to like 650+- 50 and then time it, and different for the rb26dett and rb20de....but nothing listed for rb20det, so I was just curious

[Wulfgang]

I agree... you're supposed to wait for the engine to warm up, then set idle to 600 or so (sorry, can't remember the number, but mine idles around 600), then set timing using the loop at the ignitor.

I find it interesting that your idle increases when your defroster is on. That seems to indicate that your ECU knows your defroster came on. I wonder if the ECU monitors battery voltage fluctuations and adjusts idle speed to compensate...

[goofynick6]

I don't know, but as soon as the defrost (not vent or floor air) comes on, the idle jumps up.

I also find it weird my timing is the same at the coil or at the loop, since you said it should be 10 degrees difference.

Nick

[Wulfgang]

Actually, a few other people have suggested that the location may make a difference, which seems logical to me. The ignitor drivers switch the coil to ground, but there must be some delay before the coil actually fires (the spark gap has to break down, inductances have to charge/discharge, etc.). I am not sure if the delay should be 10 degrees, but that seems reasonable.

[Joe]

Well in the R33 manual, for the rb25 it says set it to like 650+- 50 and then time it, and different for the rb26dett and rb20de....but nothing listed for rb20det, so I was just curious

really? hmm...

[goofynick6]

Set it to 650 +- 50 rpms then set timing with TPS unplugged.

The RB26DETT says idle at 900+- 50 rpms, so I'm wondering if the rb20det is the same due to the 8.5:1 compression?

Nick

[DSMs_Suck]

Personally I think the timing at the loop and at the coil should be essentially the same.

I dunno wulfgang 10 degrees at 600 rpm... thats a LONG time for microcontroller.... Hell even a while for passive components (especially at such a high potential)600 rpm is 10Hz, and 10 degrees at 10Hz is..(10/360) * (1/10Hz) [seconds] = 2.7ms. (2777us!!)

[Wulfgang]

Yeah, you're right.... spark gap breakdowns are usually only a few 100s of ns. I am not sure what the RLC delay adds up to... any EE's on here?

If, IF I had a timing light I would measure the two locations and tell you difference. But that is something I haven't gotten around to buying yet, and Autozone does not rent them out.