R33 Spec II Ignition timing and dual boost. Why doesn't the dual boost always work?

[GeoffX-19]

PF members.

I need some advice/suggestions.

I have a spec II R33 that I imported a couple of years ago and basically it has been running like a dream, and still is.

On the weekend I decided to play around a little with the CAS and discovered that when I advanced the ignition timing a little (about 3mm on the periphery of the CAS) I found to my surprise that the car was surprisingly more responsive off boost and seemed to come on boost even earlier than it usually does.

So I thought, great, I'll leave the timing advanced a little, the skylines got a knock sensor so I shouldn't be able to do any harm. Then the next morning when I went for a drive I got my next surprise.... The boost solenoid (Spec II only I believe) decided to switch the boost at around the 4K mark. Now I've always known that it had a dual boost solenoid but have never before seen/felt it work, I always thought that the difference in boost it offered was too subtle to notice so never knew it wasn't switching. Bonus. Except after about 15km's the boost solenoid is back to normal.

So I've got a car that is more responsive, uses less fuel and for about 5km's a day gives me the amount of power that it should do.

Questions:

1. What is the correct way to set the timing on an R33 Spec II?
2. What is the factory ignition timing setting?
3. What ignition timing should I run for Aus conditions and Premium fuel?
4. How do I make my dual boost solenoid work all the time?
5. Are there many gains to be had modifying the factory computer without touching the Turbo boost level? Fuel economy, power?
6. Why does the car run better for the first 100 odd km's after I reset the computer?
7. What fuel economy do others get when driving at highway speeds?

Lots of questions I know. I'm hoping that someone has had a similar experience and sorted it out.

G.

[GeoffX-19]

Hmm anyone?

[GTSBoy]

1. As per the manual?
2. As per the manual, or as per every other RB? ie about 15deg?
3. If you run 98, then standard setting is OK.
4. Dunno.
5. Both, yes. Small? yes.
6. ECU takes a while to re-learn the "best" settings for fuel and spark timing trim. The base values in the maps are more aggressive than what they learn to. Takes maybe 100km.
7. RB25s should do as low as 10L/100km at normal cruise conditions. Maybe as low as high 9s on rare occasions, probably usually low 11s. Very sensitive to accelaration events.

cheers

[Emre]

Haven't heard of the dual boost solenoid from factory.

The difference you noticed would be due to ECU reset than anything else.

To add to GTSBoy's comments :

1- Timing light and the ignition pickup loop on the firewall.
2- RB25, 15 degrees; RB26, 20 degrees.
3- The car is tuned for Japanese fuels which are better than our fuels. I would say, the factory tune is aggressive enough.
4- ???
5- AFAIK the R33 ECUs are not programmable, an aftermarket ECU wouldn't be cost effective, unless you are chasing some power.
6- As above. By increasing the base timing by 3 degrees, you are possibly forcing the ECU to decrease it back in first sign of detonation, or even hit boost cut in future.
7- 50:50 freeway / city driving i get 13 litres per 100 kms. Possibly 11s and 15s respectively. I am playing with lean cruise at the moment and am certain it dips into single digits on freeway.

[tandy ass]

Correct me if I'm wrong here but didn't only the series 1 RB25's have the dual boost solenoid? The series 1's are the RB25's with ignitor module at the rear of the coil cover, the series 2's didn't have an ignitor unit as the transistors were built into the coils.

[SSR]

The base map settings may be aggressive but 100km seems like a fairly long time for the ECU to find more efficient settings doesn't it? I'm not certain on that, just wondering.

To me it just sounds like your ECU can't settle on that much advance without reverting back to a safer mode, it is factory after all.

[AlexinPerth]

2- RB25, 15 degrees; RB26, 20 degrees.

That sounds like the absolute timing, not the base timing.
I'm not intimately familar with the Nissan engines, but on everything else I've touched, the timing is set by forcing the ECU to revert to base timing, and then setting that - usually in the range 2-5 degrees.

Please correct me if I'm wrong.

Alex.

Edit: oops, thread from the dead, time to wake up now.

[TonyJZX]

Correct me if I'm wrong here but didn't only the series 1 RB25's have the dual boost solenoid?

as far as I know all of them are single solenoid only

The series 1's are the RB25's with ignitor module at the rear of the coil cover, the series 2's didn't have an ignitor unit as the transistors were built into the coils.

correctomondo!

The ignitor module disappeared in early 1995 with the S1.5 - you do see some '95 S1 models with the module though.

The initial problem seems to be that the OEM CPU learns what's 'wrong' with the motor and adjusts to suit. There's no easy (read: cheap) way around it.

I'm not even sure if an interceptor like an SAFC will fix it.