Nissan RB25 COP and CAS questions

beav · Post by **beav** » Thu Jul 28, 2005 4:39 pm

Im trying to install my first mega squirt into a buddys nissan 240sx with a rb25det skyline motor swapped in. Its a inline 6 cyl with cop and the coil packs seem to have ignitors built into them so I would like to try and trigger them directly in a wasted spark configuration. I am assuming they will need dwell control but I dont really know much about them. I am hoping the dwell wont be too much of a headache to control but I am not sure what else we could use without ditching cop and I would like to keep the setup as clean and simple as possible. The only other option is to try using earlier rb coils packs that used an external ignitor and trigger them with 3 vb921's but the other coil packs may be pricey so I think ill just have to try these ones first.

The main concer is the input, using the stock cas would be ideal but it will need modification and I am not sure what will be the easiest/best solution. The stock cas seems similar to other sr20(and possibly vg30) wheels I have found posted in here in that it has an outer sensor with 360deg optical sensor and it also has a inner sensor with 6 evenly spaced holes but the thing that makes this one unique from the others I have seen is that each one of the 6 holes is longer in length than the previous. Is the 360 degree wheel out of the question because of its super high resolution? I could attempt to cover 2 holes to simlate a 180-1 wheel but at 8000rpms this thing will be pulsing at 24khz and there is just a super fine line of metal inbetween in each hole on the wheel. I may be underestimating the capabilites of the ms and this optical wheel but I am concerned this may lead to miscounts and unreliable timing control, if not the this may be a solution but then I have to figure out a way to cover two of the tiny holes which I am not even sure how I would go about and this peice of metal is paper thin. The next sensor is only 6 points or 3 per crank revolution and varying lenghts(not sure how much if any trouble that will cause), it doesnt seem like much resolution but I have seen the DSMs are running their stock CAS with 4 points and a second wheel trigger. I assume you are forced to use time based triggering and then I still have to figure out a second input to reset it, maybe cover up all but one or two of the 360 holes? Are there any dissadvantages to this or is there a certain minimum amount of resolution I should shoot for since I may have to do a little fabbing anyways? Last resort is ditch the whole thing and try and mount a vr sensor but that may be some work on this motor. What do you think my best options are?

Here are pics of the cas, they are blurry but you can see the shiny inner metal ring with the outer 360 holes (looks like a solid grey line in the blurry low res pic) and the 6 varying length inner holes

beav · Post by **beav** » Thu Jul 28, 2005 11:50 pm

Well I found the original wheel decoder post and that answered some of my questions. Looks like I will need to replicate a 6-1 crank sensor at minimum so I need at least 12-2 at the cas but I will probably go for more to try trigger return since it probably wont be any more trouble. I know now the 360 is useless and I dont think I will be able to modify or replicate the wheel without us paying someone lots of money to cnc one. I have a honda 24 pin reluctor and vr sensor that may be an option if I can adapt it into this cas, the shafts look to be very close to the same size if not the same but I dont know if the reluctor will come off of the honda shaft as its pressed on pretty tight. Still not really sure on what the easiest way to do this will be though, I remember it looking pretty tight behind the crank pulley but I may have to evaluate that option again. Anybody have any other ideas?

beav · Post by **beav** » Fri Jul 29, 2005 9:13 am

DSM 4g63 optical sensor which works with MS using 2 wheel decoder firing 2 stage wasted spark.

Althogh the casings are not identical the pickup looks identical so the wheel more than likely should be the same size, probably are since the nissan cas has a misu stamp on it

. This wheel may be a plug and play option for the sr20det guys wanting to run wasted spark, I have seen a couple on here. Now I would love to get my hands on a 3000gt/stealth cas and see what they have for a cas disk.

Sorry if I am thinking out loud here, did not think I would figure this out on my own so quick, maybe this will help somebody else

.

Edit:
actually found a pic of the 3kgt wheel

Almost useable except there are 4 inner holes instead of the 2 I was hoping for

. This may be easier to modify though if I could find one for a cheap price.

slow_hemi6 · Post by **slow_hemi6** » Fri Jul 29, 2005 6:49 pm

Well this is why what you are thinking of is called difficulty level 10

so anything here after should be taken in that light. You will spend money and waste time if you want a solution.
Anyway the best advice I would give a US citizen who can get edis6 easily is to use that.
You dont even need a CNC to machine an adapter for the trigger as any machinist with a lathe can make one. Then a bracket for the VR , the edis mods and you're away.
The problems you will face with the wheel decoder are as you probably know, The cas will have to be modified to give the right triggers which would be more complicated than the edis adapter. The dwell is not quite right with the mutiple outputs (yet but work is progressing ?) The spark outputs need to be driven and directly off the proccessor might not work for the load of two igniters so some extra circuitry could be required.
The cas actually gives a great signal for std MSNS mode with the 6 inner slots.Your problem is you have no Dissy cap or rotor button.
If I were trying to this I would go edis and then maybe when the dwell issues are sorted I would go wheel decoder using the 36-1 wheel from the edis I had allready installed.If I lived in a country that got edis, that is

Over here If I was itching to get going I would probably get an adapter made up to use a dissy cap and rotor on the CAS if room permitted till the wheel is sorted. But then if I know myself once it was running great I probably would'nt change at all.

beav · Post by **beav** » Fri Jul 29, 2005 11:58 pm

slow_hemi6 wrote: If I were trying to this I would go edis and then maybe when the dwell issues are sorted I would go wheel decoder using the 36-1 wheel from the edis I had allready installed.

Yea after weighing all the options I am thinking EDIS does make the most sense and will probably be the plan now. I was already starting to think the 36-1 crank wheel might be the best route without wasting too much time and effort. I was also starting too wory about triggering two of these ingnitors off the MS and figuring out the dwell so I liked the idea of having EDIS to fall back on. Then I talked to the owner tonight and he did not mind the idea of ditching cop for wasted spark coils so it looks like we will just go ahead and try the full EDIS6 setup so we can put all the ignition concerns behind us. Knowing that it will for sure work so we can focus on tuning instead of testing makes more sense as this motor is pretty built and not something we really want to play around with. Time to hit the junkyards

.

cdndub · Post by **cdndub** » Mon Sep 12, 2005 4:07 pm

autronic makes trigger wheels for these dizzies, I just ordered one for a customer with an SR20DET.. about $85 CDN for the wheel plus shipping from an autronic dealer, maybe a little pricey but it retains all the factory parts and should work fine with the dual trigger code in MSnSnExtra

has 4 outer windows and 1 inner.

beav · Post by **beav** » Mon Nov 28, 2005 1:29 am

skwertle wrote:I am shopping around for a standalone system. Will the Megasquirt Ver. 2 still require the purchase of a EDIS to fix this particular problem?

EDIS is still going to be one of the easier solutions because the configuration is proven and all you have to worry about is mounting the wheel then set it up like any other 6cyl instalation. Otherwise MSnExtra currently has 6 cyl spark outputs in testing stages and if it works as well as the other wheel decoder modes then it may be possible to use 6cyl cop with mostly stock parts, only drawback is using 6 outputs for ignition will mean you dont have much for optional outputs left. The stock wheel in the CAS is no good so the easiest option would probably be to purchase a replacement wheel from autronic so you can still use the nissan cas. If you want to use the stock coil packs you will need to figure out if they have the ignitor built into them or not and you will have to figure out the dwell settings. The 3rd option would be to mount a wheel on the crank like EDIS but instead use Extra to control them in a wasted spark configuration. Keep in mind though if you want to use the stock coil packs in wasted spark it might take a little research to figure out the easiest way to drive to coils from one ouput. When its time to get my friends RB25 project started I might look into at least using the stock coil packs still, probably wont be till closer to spring though.