19th January 2007, 10:14 PM
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#256 (permalink) |
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I am not suggesting that there are not harmonics present in the crank / cam rotational positions, however that is easily dealt with in the software, which no one on here is able to inspect. The fact that the CAS has 360deg markings and 6 windows suggest to me that the RPM signal is processed in varying ways according to the RPM (Correlation of cylinder windows with crank angle degree, coupled with rotational acceleration rationality checks - note the varying window lengths). The whole nissan CAS issue was only raised after multiple users (me included) had issues with the piece-of-crap AEM ecu that is clearly unable to process the signal correctly (even at idle)
Do you really think Nissan would use a sensor to determine timing that is both more expensive, more complex and less effective than a crank wheel? The car was manufactured for what 9 -10years? I must have missed the change to crank AS on grp A racers, R34 or Z-tune, or mines or HKS or or or or...... For info the 360deg markings would give rise to a 24Mhz signal at 8000rpm, a 60-2 gives a 8Mhz at 8000rpm. I also see RPM saw-toothing when logging from datalogit, however this is not necessarily the same signal used by the ECU to process spark timing (you don`t see the timing jumping around with RPM for example). There is a world of difference between the signals passed on the I/O bus and the sample frequency used and the internally processed signals. Last edited by ExScoobyT; 19th January 2007 at 10:21 PM. |
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19th January 2007, 10:22 PM
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#257 (permalink) | |
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19th January 2007, 11:00 PM
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#258 (permalink) |
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There are lots of opinions about the CAS issue, but no hard facts as to exactly what the stock ECU does with the signal. All standalone ECU would rather not use a crank position signal from the camshaft. 99% of car's don't use this method. This must say something.
As far as I'm concerned, the CAS isn't what I want, I want a #1TDC position and a crank position. This is the usual method. Blame the AEM, blame the CAS, the argument will rage on forever, but please not here. I will prove the CAS crank position variation when I'm running again and post my finding. I'm as curious as everyone else.
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20th January 2007, 10:25 AM
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#259 (permalink) |
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CAS wobble is a huge issue.
Whether it is a crank harmonic, cambelt harmonic or a problem that is amplified as poor timing which the creates uneven power output from each cylinder which then causes more harmonics I don't know. What I can say is I have logged the relationship between the flywheel and the sync position provided by the CAS. My timing is driven from the flywheel so is not affected by crank and cambelt harmonics, but cam timing is also out by the amount shown on the graph below. The graph shows the CAS wobble on my engine under full power through the gears at TOTB V, the 0 to 100 scale on the left is 0 to 20° CAS wobble, so there is a + an - 5° error. You not be given access to the workings of the ECU and will never really know well your unit will perform. Gutted for you Andy that you have to pull your engine apart again so soon, here is hoping that you overcome all the difficulties this time. 
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RB30 - Sequential Gearbox - Acceleration Demo Video R34 GTR VSpec II NUR for sale TOTB II ¼ mile Drag Shootout champion. TOTB IV 4th TOP speed @193.8 MPH. TOTB 6 10.3 @ 150 MPH ¼ mile 194 MPH at 1 mile Shakespeare County Raceway 10.120 ¼ mile RB Motorsport Built OS Giken 3 litre engine and OS Giken sequential gearbox. Twin HKS 3037S turbos 480 BHP ea. Motec M600 ECU. |
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25th January 2007, 04:21 PM
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#261 (permalink) |
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One of the best threads/discussions I have ever read.
A good place to learn about the RB30 Best of luck with the rebuild Andy, a learning curve. Hopefully in a few years I will be RB30ing my car. |
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25th January 2007, 04:54 PM
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#262 (permalink) |
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If anyone wants any more pics an anything, (whilst its all in bits again) nows the time to request them.
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25th January 2007, 06:23 PM
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#263 (permalink) | |
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Quote:
Could I have one of you scratching your head whilst looking into the engine bay? 
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25th January 2007, 06:29 PM
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#264 (permalink) | |
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Regards, Scott. GTROC Members Secretary. Please feel free to PM me with any GTROC Membership or Merchandising issues. OO SKYLINE OO My R32's full restoration: http://www.gtr.co.uk/forum/upload/77...ht=restoration |
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26th January 2007, 09:38 AM
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#268 (permalink) | |
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BIG TUNERS
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Only when I have been there,done that, will I offer people any advise on the subject!!!! |
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26th January 2007, 09:50 AM
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#269 (permalink) | |
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Quote:
 But joke aside.... would you dare to comment on this?? Asim... |
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26th January 2007, 10:55 AM
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#270 (permalink) | |
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Seriously though I can probably add my view on this topic, but you must understand a few things 1st. 1. "Tuner" one who tunes? 2. In my day a tuner was a person who syncronised carbs,changed the jets and chokes etc and optimised the ignition timing and contact breaker points dwell to optimise the running of the engine. 3. The fact that a company or joe public fits power enhancing parts to his car does not make them "tuners". 4. This old time tuner has been replaced by the clever computer literate person who presses buttons on a keyboard. What an easy time he has of it as well. 5 I spend my time building engines ,gearboxs and other major units and am not very often involved with the "tuning" of cars on the dyno. Anyway ,briefley, my view on the subject. Take a say 650ps car on the dynapack. Fitted with F/Con Pro, map sensor,but no V-Cam so the timing belt cover is removed in order to optimise the cam timing.Mapped to suit. On the same day, same air pressure,humidity, temp. Remove the Pro and substitute an AEM ems.Remap car. the first thing you find is that the car will not accept the same amount of timing advance with this unit as the Pro. I can accept that the figures are not really 100% important, you know the Pro measures in degrees , the AEM measures in "eggs", so what just makes it harder for a geriatric like me to get my head round. But the bottom line is that "what the f ck" we have just lost 20 ps top end and a big load of torque on the way up. Now my view on this as a spanner wielding mechanic is that there must be an ignition timing variance between the cylinders. You are tuning to the one displaying the most advance and some of the others may be perhaps 4 or 5 degrees behind it! Thats where your power has gone. As regards the CAS, well ,run the car on the dyno with a good CAS installed and it wont show any timing fluctuation up to the limit of the timing light, in our case about 6000` rpm .That is with the engine loaded. Without it being loaded it does vary up to about a degree, but what is noticeable is that when loaded there are absolutely no harmonics issues with the belt when properly tensioned and under load.On the overrun it way "wag" about a bit. Shame really that the AEM does not,at the moment, do what it says on the box.It would be a good bit of kit. For the moment we will stick with the HKS unit!! Tony
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