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stony

RB CAS drive gear replacement info.

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stony    11

Mine would only backfire out the intake and exhaust. If you changed the cas drive gear like I described above then it may be your problem. Just rephase the coils as described above. If u havent changed the gear then its probably the start up cal just needs tuning. I found I needed to add 40% across the map just to get it started. Obtw I found that the injector wizard did not work for me.

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Ok, so I have been working on this problem now for about a year and I seem to be getting no where with it. I took the car down to a local performance shop that I knew would be familiar with the motor and they are telling me that the problem is the greddy style intake and the non circulating blow off valve. They said I would have to go with a stand alone ecu to fix the timing or put the stock parts back on. Can anyone confirm this? I was hoping to avoid the great expense of a stand alone and the added hassle.

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Ok, so Mack from McKinney says the intake and the BOV are not the problem and that there must be a mechanical knock or some sort of wiring problem. I checked the Knock sensors again today and they ohm out to what everyone says they should so I don't think they are the defective. I have checked continuity from the sensors to the ECU and the wiring is fine. So now my question is what else could cause this except for an actual knock? The check engine light is not on and there are no codes so how do I know if there is knock if the computer is not telling me so?

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OK so what about the Maf? Does it read air temp? Lets say it is to close to the motor because it probably is and it is getting to hot and there for giving bad info to the computer. I noticed the other day when I started the car up and put the timing light on the crank that at first it was spot on 15 degrees and as the motor warmed up it started to decrease until it was at zero or below.

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The MAF does not have any type of temp sensor in it. Well not by conventional means as it measures air flow via the cooling effect on a hot resistor, kind of like a temp sensor but not. But its strange that the computer is doing this. Does consult have a timing indicator?

 

Yes the consult shows the timing. If you look at the video that I posted earlier in this thread you will see how it is jumping around.

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HowlerMonkey    12

I've replaced the sensor with a resistor near 1 megaohm......might have been 770k to eliminate a false sensing of knock from pulling timing when I was chasing something similar but you have to be careful when running without that protection.

 

I was using a late ecu on a L28 and some sensors are sensitive enough that the valvetrain noise of the older engines trigger false knock senses.

Edited by HowlerMonkey

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SloperZ    0

OK so what about the Maf? Does it read air temp? Lets say it is to close to the motor because it probably is and it is getting to hot and there for giving bad info to the computer. I noticed the other day when I started the car up and put the timing light on the crank that at first it was spot on 15 degrees and as the motor warmed up it started to decrease until it was at zero or below.

I had my MAF placed too close to the turbo and recirc from the blow off valve and I was having a lot of trouble once the engine warmed up. I moved the MAF about 12 in. farther away and put another bend in the intake piping and the problem was fixed. This may be worth looking in to.

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Ok, So I plugged the Cold start valve this afternoon to see if that would make a difference and again no change. Can anyone verify that a freddy intake manifold or a greddy will work with the stock ECU. I am preferably asking this in hopes that some one who actually has one running on a stock ECU will chime in and confirm or deny. I have ask a few people and I get conflicting answers. Mack from McKinney motorsports says that it should work fine and the performance shop in town says that you have to have a stand alone ECU to run an aftermarket intake manifold.

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I had a Freddy intake manifold with my stock RB25 ECU, it ran like stock, stock turbo, stock 98 240sx exhaust, stock injectors etc..made 268whp and 273wtq on 12psi 

 

Thanks for chiming in on this flatrate. That is the consensus that I am getting from other sites as well. The performance shop in town that is the only shop that I know of that is familiar with the RB motors is telling me that the stock ECU wont work with the aftermarket intake plenum. In turn without even offering to do any diagnosis of the problem they are telling me that the only way to fix the problem is to get a stand alone ECU. I just can't give in to this assessment without hearing it from someone more reasonable.

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NewZed    56

The attached picture and text is from the 1990 300ZX EFEC chapter, page EFEC-24.  Maybe it has some clues.  Each point is an ignition timing value, but there are other conditions used by the ECU also. Maybe the ECU is acting on an erroneous condition indication.  Battery voltage, starting signal, temperature...  I'm not sure what the text means by the ECU detecting injector pulse width since it is the ECU that sets injector pulse width. Probably a translation grammar error.  I assume that the RB engine management is similar, they all seem to use this map from the early 90's on.

post-8864-0-63524900-1384231369_thumb.jpg

Edited by NewZed

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So the shop called today. They claim that they were able to get it to 15 degrees with the CAS fully advances in the slots. They took everything apart to make sure that everything was installed right and they said everything was spot on. So they then put it back together with exhaust cam advanced one tooth and now they say it reads 15 degrees with the CAS in the middle of the slot like it should. Does anyone know if this is an acceptable solution? I don't want to drive it like that for very long if that will cause any harm. I am going to go drive it tomorrow and make sure that everything feels and looks good before bring it home.  

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flatrate    1

Doesnt really matter where the CAS ends up, cam timing should be set to stock, or degree'd in if using aftermarket cams. ts Vital that the cam timing is right on, if its not it throws everything else off.

 

My CAS is nearly all the way advanced, i know my cams are installed correctly because i degee'd them when i built the engine. I also run 20 degrees of base timing not 15 like a stock 25.

 

If it stops pulling timing then maybe its now correct?? hard to say 

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So if the tech advanced the exhaust cam one tooth wouldn't that now make the intake cam late or retarded? I got the car back today and it seems to run ok but when I hit boost the wide band goes strait to 10s and the power falls on its face or flat lines and hesitates. Seems like there is still a lot to do to make this right.

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I stuck the timing light on it today to make sure that it is at 15 degrees as the tech said it was and I'll be darned if it isn't the same as it was when I took it into them. It's as if it is not going into base mode like it should because when I put the timing light on it at idle tps connected it shows -5 degrees and when I disconnect the tps it revs just a little bringing the timing up just for a second and then it drops back to idle and timing is back to -5 degrees. On other sites people are saying that when they plug their tps back in that the timing may drops to 10 degrees but never have I seen anyone say that their timing is negative. Can anyone make sense of this. Please embellish me with any circumstances where the ecu would retard timing at idle. Does it think there is to much air or not enough fuel at idle? Could the crank pulley be wrong or can it be installed out of time? 

 

I can tell that the tech put the timing belt back on too tight as it is making a lot of noise. Is it bad to drive it like this?

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flatrate    1

i'd put the cam timing back to stock.. If he just changed the exhaust cam then it wont have an effect on the actual events the intake is going thru as its DOHC..

 

How are you checking timing are you using the timing loop in the back of the coil harness or are you retrofitting a wire into the number 1 coil?

 

i haven't read your entire thread.. but have you replaced the knock sensors? checked to make sure there torqued properly etc

 

Id also make sure the engine is grounded well, and in more than 1 place.

Edited by flatrate

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I have tried all methods of getting the timing signal but the one that works best for  me is to pull the signal from an extension wire between the coil pack and the plug.

 

I have not replaced the knock sensors but I have ohmed them out and everything seems to be OK. I also do not have any check engine codes coming from the ECU. I would think that if it were not getting knock signal or if it was faulty then it would throw a code.

 

I have a large 4 gauge wire run strait from the battery to the engine block. 

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