1991 GT-R

[Jjtxaz24]

9 minutes ago, BK said:

It's almost a knee jerk response now isn't it, "it's the coils". Most of the time it's true though.

Any good coils that dont require me upgrading the whole ignition system (harness, coils) 

14 minutes ago, GTSBoy said:

Missing at revs under load should usually be blamed on coils before anything else, and then after that, on just about everything else in the ignition system (coil loom, ignitor, CAS).

The loom is new, so is the ignitor. I did have to replace one coil (company I got the car from sent it out for me and it worked so I've left it)

CAS is OEM on the car. Never changed it. My pig tails on my injectors could use some love. 

[GTSBoy]

New genuine (not fake!) OEM coils are a good choice. Splitfires are the only aftermarket same-form-factor coilpack that I would consider.

But seriously - these days, Audi R8 (or equivalent) coils or R35 GTR coils are the way to go. If you need to replace coilpacks it is foolish to stick with 35 year old tech when 1 year old tech is available, 11ty times better and only slightly more expensive to put in place. Good coils are only $50 each these days, whereas the stockers and Splitfires are still up around $100 each.

Then you can get rid of the ignitor too.

Put the effort into making it better, not same.

As to the rest of the ignition system. You probably need to put a scope onto the CAS signal to see if it is messy or not. The Nissan ECU at least manages to punch through a lot of the crap that the CAS puts out (better than most aftermarket ECUs seem able to), but there is still a limit. At the least you should make sure that the bearings aren't stuffed, the wiring connections are good, etc.

A high rpm miss can also be a shortage of fuel. What do you know about the health of all that stuff?

[Jjtxaz24]

16 minutes ago, GTSBoy said:

New genuine (not fake!) OEM coils are a good choice. Splitfires are the only aftermarket same-form-factor coilpack that I would consider.

But seriously - these days, Audi R8 (or equivalent) coils or R35 GTR coils are the way to go. If you need to replace coilpacks it is foolish to stick with 35 year old tech when 1 year old tech is available, 11ty times better and only slightly more expensive to put in place. Good coils are only $50 each these days, whereas the stockers and Splitfires are still up around $100 each.

Then you can get rid of the ignitor too.

Put the effort into making it better, not same.

As to the rest of the ignition system. You probably need to put a scope onto the CAS signal to see if it is messy or not. The Nissan ECU at least manages to punch through a lot of the crap that the CAS puts out (better than most aftermarket ECUs seem able to), but there is still a limit. At the least you should make sure that the bearings aren't stuffed, the wiring connections are good, etc.

A high rpm miss can also be a shortage of fuel. What do you know about the health of all that stuff?

I see your point. The maintenance I'm doing is to upgrade to new tech and also allow me to drive it, it is not a daily driver but I enjoy using it. Being the only source of income makes that a bit difficult. Not to worry though, it makes sense on upgrading the coils and getting rid of the ignitor. It was a route I had considered and was looking more into I just wasnt there financially yet.

As I was rebuilding the turbos I cleaned out the coolant and oil lines, replaced all the gaskets both cooper ones and for the piping as well as cleaned out and in some instances replaced some banjo bolts cuz they were just old and had tons of build up. My coolant temps stay much better now as before I was pretty high, higher than normal. 

Point being, as far as I know the fuel system is decades old, OEM and probably needs a refresh. I could rerun new fuel lines, replace the pump, and clean out the injectors and replace the pigtails as well. I was honestly thinking the cutting out was a fuel issue. Maybe clogged injectors or a few pigtails acting finicky. 

Your feedback is appreciated. 

[Jjtxaz24]

Ok, little update. I ended up ordering a kit that will remove the ignitor and bring my coils to modern times. They are the LS2/LQ9 coils.

I have a Nistune ECU and it was advised through articles and forums to change the dwell time down to a 4.3. I looked through the nistune software guides and all I found was this:

Also, I tried to bring the idle down threw the screw located in the passenger side think it's called the AAC. it's the idle adjustment screw. I tightened it and lowest idle I got it down to was 925-950 rpms. The manual says the RB idles at 950 but I've read through the forums it likes to be at 600-800. That's why I tried to lower it. 

[joshuaho96]

The ECU sets the idle target. If you haven't disabled this function in consult the ECU will be fighting you the whole way. The manual spec is 950 so it will open up the AAC and adjust timing to get to 950 rpm.

[Jjtxaz24]

2 hours ago, joshuaho96 said:

The ECU sets the idle target. If you haven't disabled this function in consult the ECU will be fighting you the whole way. The manual spec is 950 so it will open up the AAC and adjust timing to get to 950 rpm.

Ok, so 950 it is then. I just felt like it was idling to high. 

I havent made any changes to it just yet. 

[joshuaho96]

9 hours ago, Jjtxaz24 said:

Ok, so 950 it is then. I just felt like it was idling to high. 

I havent made any changes to it just yet. 

Generally speaking you should only adjust the idle adjustment screw if you have Consult readout to log the AAC valve duty cycle. I believe recommended target is 35-40% in warm idle.

[Jjtxaz24]

On 1/30/2020 at 10:48 PM, joshuaho96 said:

Generally speaking you should only adjust the idle adjustment screw if you have Consult readout to log the AAC valve duty cycle. I believe recommended target is 35-40% in warm idle.

Looking through the manual it states 950 so that's what I left it as. 

Any of you guys ever use the LQ9 coil upgrade kit from CX Racing. Picked that up this weekend and it isnt a plug n play harness. I sent em an email but they wont respond till during the week. 

Also, need help in changing the dwell time to adjust for the new LS2/LQ9 coils. Havent installed it yet. Might order the plug and play harness that wiring specialties sells for that conversion. 

[joshuaho96]

5 minutes ago, Jjtxaz24 said:

Looking through the manual it states 950 so that's what I left it as. 

Any of you guys ever use the LQ9 coil upgrade kit from CX Racing. Picked that up this weekend and it isnt a plug n play harness. I sent em an email but they wont respond till during the week. 

Also, need help in changing the dwell time to adjust for the new LS2/LQ9 coils. Havent installed it yet. Might order the plug and play harness that wiring specialties sells for that conversion. 

I would check when you can in Nistune to see the AAC Valve live value at warm idle, make sure you have some range both above and below or you might have idle issues.

As the documentation suggests you want to change the dwell vs voltage values and not much else. In theory you could probably leave them stock but you won't realize the benefit from them.

[Jjtxaz24]

20 hours ago, joshuaho96 said:

I would check when you can in Nistune to see the AAC Valve live value at warm idle, make sure you have some range both above and below or you might have idle issues.

As the documentation suggests you want to change the dwell vs voltage values and not much else. In theory you could probably leave them stock but you won't realize the benefit from them.

I read and looked through the documents for Nistune but unsure as to what to change the values to to get the recommended 3.4 sec change. 

[joshuaho96]

4 hours ago, Jjtxaz24 said:

I read and looked through the documents for Nistune but unsure as to what to change the values to to get the recommended 3.4 sec change. 

I would go look up the LS2 coilpack recommended voltage vs dwell time spec. Then if you know the base dwell time for a given voltage then you can convert from the raw 0-255 values to milliseconds.

[Jjtxaz24]

I have a spare harness that i will be using to get the new one that i ordered set up to make it a plug and play. I get the main harness is the coils and power, what is the 2nd one on here for (circled in red). On the current loom that's in the car. it looks like a black wire, which I'm assuming is Ground and 2 white wires. On this wiring specialties harness below it only shows 2 wires... I tried to look it up in the Manual and didnt find anything relevant to what it is. 

 

Edited February 4, 2020 by Jjtxaz24
changed file to a jpg