RB30 engine conversion (lots of pics)

[NISFAN]

Andy,
Can you divulge who gave you this info about this Nissan Cam/crank angle sensor problem? Was it an AEM source?
There are plenty of 2litre 4 pot nissans using the stock CAS with no reported scatter, and I fail to think why Nissan would put up with a compromised system, when there are loads of fixes.

I'm not following your explanation of the problem. When you say CAS do you mean crank angle sensor? The CAS is the only thing that determines engine speed/position!!!

[tyndago]

Originally Posted by R32 Combat

Ever since the CAS was used, Nissan found that the ignition timing would drift as 4500-5000rpm. This is caused by engine harmonics in it's STD form and there is nothing physical that can be done about it. Nissan got around this be basically not using the CAS through this rev range and calculating the ignition timing using engine speed. All cars with CAS suffer from this. Which is why Toyota don't use this system. As soon as anything is changed in the valve train, the rpm of ignition scatter changes, which is why DET is so pronounced in the RB engines.

I have never heard of this in the factory ECU. I will enquire into it myself. I know that at higher RPM's we see some RPM drift. The thing is that the RPM is picked up off the CAS.

The CAS is belt driven, and I think the belt moves around a little. One a 600 hp car under load, I would see the RPMS move around 200-600 rpms up and down. Thats on a new build, with a new motor. If you are on the Datalogit group - for Power FC. In the files section, there are some logs of Nicks car 11 second runs. You can see in secessive frames the RPM's bouncing.

I remember reading that Mario - Exvitermini had issues with the Motec and the Nissan CAS. I think they were seeing something similar. Big rpm movements frame to frame.

I have a Nissan CAS that was altered to run a pre- Nissan CAS AEM. They made a new wheel for it. Seemed to work out ok on that car. It did over 900 whp.

[Hugh Keir]

Here is a logged example of the problem that is caused when a high power GTR runs the CAS for ignition timing. The graph shows a the CAS error as you go up the gears in my car, although I do not use the CAS to provide ignition timing.

The 0 to 100 scale on the left = 20° of ignition timing which if you look at the trace = 10° of ignition timing wobble

Finding a fix for this problem is straightforward when you have a non plug and play ECU like the Motec or Autronic.

It is not so easy for the Power FC, although I believe RB Motorsport are working on a solution for that ECU as well.

As mentioned earlier, the random ignition timing will give rise to lots of detonation especially up in the higher gears. This is definitely a big problem for RB26 engines.

[R32 Combat]

I know this would open a can of worms...

The guy I spoke to works for a MKIV Supra garage in Bristol.

He's working with both Gems and AEM to find out why there is a problem with the CAS on the AEM ecu.

[NISFAN]

Hugh,
That is an alarming amount of variation.
So is this a function of vibrational slackness on the timing belt, electrical noise?

Andy,
Can you not replace the nissan system with conventional crank/cam sensors with AEM?

[R32 Combat]

The variation is due to the cam belt. Any error between the crank and cam gets amplified due to the fact that the ignition/injector timing is out. It's a 'catch 22' situation.

I went to the Supra guys to ask about fitting another system to my AEM, hence getting into a long conversation with them. It's easier to do with the universal AEM than the vehicle specific unit. Why, I don't know. I've been advised to wait until AEM/Gems have a fix for this, or until they conclude that it can't be done well enough. Then I'll take the advise I'm given. Either way, the chaps will have a proper fix so the AEM is 100% accurate.

Personally, I'd like to retain the CAS but move it.

Time will tell....

[Asim R32GTR]

Originally Posted by Hugh Keir

Here is a logged example of the problem that is caused when a high power GTR runs the CAS for ignition timing. The graph shows a the CAS error as you go up the gears in my car, although I do not use the CAS to provide ignition timing.

The 0 to 100 scale on the left = 20° of ignition timing which if you look at the trace = 10° of ignition timing wobble

Finding a fix for this problem is straightforward when you have a non plug and play ECU like the Motec or Autronic.

It is not so easy for the Power FC, although I believe RB Motorsport are working on a solution for that ECU as well.

As mentioned earlier, the random ignition timing will give rise to lots of detonation especially up in the higher gears. This is definitely a big problem for RB26 engines.

Hugh,

wouldnt this be a problem on the stock ecu aswell??
How does the stock ecu take care of this problem?

Asim..

[Hugh Keir]

Nisfan & Asim,

This is equally a problem on a standard ECU and is not catered for except that it is less of an issue on a 280 BHP engine.

The problem has probably been identified by others, but is initially a problem with cambelt flex that leads to errors in ignition timing that causes uneven ignition timing which then leads to crank flex and so it builds up.

R32 Combat,

I do not know how the AEM works, but I am pretty sure that the workaround Rod has in mind will be a fix for all ECU's, so may help you when it becomes available.

[R32 Combat]

It's can't be that hard to fix. Most people don't know there was even a problem.

The CAS is a good peice of kit, it just can't be driven from the camshaft.

[NISFAN]

Combat,
What makes the AEM vehicle specific? Can you not just flush the software with the Generic stuff, and then add the type of sensor you want?

[R32 Combat]

To be honest, I think I might have got the wrong end of the stick there.

I think the only difference is the plug and what its wired up to.

The AEM car run auto boxes, VTEC, etc, but the Nissan AEM doesn't have enough extra pins in the plug to do this.

Hence vehicle specific ECU and a universal one(which I guess has a huge plug on it)

[NISFAN]

Andy,
I am thinking the Nissan CAS has a sensor to pick up the 360 slots, and another sensor to pick up cam position slots. i.e. two sensors/wiring circuits in one.
This being the case, surely you could be able to separate these into a crank mounted Hall sensor, and a cam sensor?

If the software allows it, you should be able to tell the ECU the wheel spec (36-1, 60-2, etc) and positioning, for both sensors.

I'm running DTA P8Pro on my RB26, and have cam sensor for full sequential operation. I'm pleased to say, my crank trace/timing is solid as a rock.

I was unsure whether AEM was full sequential on a 6 cylinder? Can anyone confirm?

[sleepyfox]

I'm confused - belt from crank drives cams. CAS attached to end of one cam. If we're saying that 'belt flex' causes the CAS to be out, then surely the cam timing will be out too as CAS is attached to one end of the cam, no?

[andy42uk]

Originally Posted by R32 Combat

It's can't be that hard to fix. Most people don't know there was even a problem.

The CAS is a good peice of kit, it just can't be driven from the camshaft.

THANK YOU THANK YOU Andy, and Hugh Keir for the chart.
I can feel this timming movement (honestly) it is prononced on my car by the auto box! after running the rev limiter in 3rd, and then engageing overdrive the engine revs fall right into this rev-range, and I have been going mad trying to work out why it feels so odd, and why there is such variation with DET monitoring, sometimes its terrible sometimes it flys...
It is a relief to know why at last.
Please keep us informed to your solution, esp. as it looks like I'm going RB30 as well!
Thanks a lot,
Andy.

[R32 Combat]

Fox

Yes, the cam timing does vary, but thats not as important as having the ignition timing wandering about.