Thread: Spark blow-out / break up and bucking from 2.5k-4.5k rpm (custom AEM EMS install).

I'm not looking for help, just documenting my issues so I can keep track of what's happening and what I've done.

I alluded to the new problem I'm having in this post: http://www.sr20-forum.com/tuning/24991-i-need-help-someone-aem-ems-their-sr20-fixed-4.html#post325672

The car is now starting up and working amazing well. It's so close to being perfect. There is a glaring problem though. Like the title says from 2.5k-4.5k and anywhere from 70kPa on up (easiest when WOT) I'm getting severe ignition issues causing the car to buck and surge until after 4.5k rpm where the problem goes away and the car pulls very strong.

The timing map has typical safe settings. The fuel isn't overly rich or lean I don't believe.

Messing with a couple of things like coil dwell settings and swapping to much better plugs have helped a bit but not completely solved the issue.

There is a setting I can change in the AEM calibration that removes the problem all together, but it causes other issues and I'm pretty sure it's not the right solution. However, it does show that the ignition system is adequate and the problem lies in the AEM settings.


Keep in mind I have the newer style CAS (with the built-in coil) and am using 2-wire (passive/"dumb") coils with external ignitors. So this is not a "stock" configuration by any stretch of the imagination.


After bashing my head against the problem for a while now and learning a lot more about AEM's trigger setup in the process, I decided a call to AEM tech support was in order. I spoke to a tech today who said everything I did was correct, and all the settings I had were correct. He said the engine should work flawlessly. He explained a few more things and I learned a bunch more about the AEM trigger settings and ignition settings. He said my hunch about the one setting I changed to make it work was correct. I shouldn't have to change that setting, and that is the wrong way to fix the problem.

He basically told me they have all sorts of problems with the Nissan CAS discs. It's not just a problem the RWD guys have, or the GTi-R guys, or the KA24DE guys. All the Nissans have trouble with the stock CAS disc and AEM EMS. He said the next step is to swap the stock CAS disc to their 24+1 disc and that should sort everything out.

I have a 24+1 disc that I used to use with VEMS and I'm going to see if it is the same. If it is, I'm going to install it and give things a whirl.

Wish me luck.

Man I hope that fixes it , boost withdraw is a bad thing!

What exactly is the disc btw?

Here is a picture of a stock CAS disc.


Here is a picture of the 24+1 disc I got for VEMS a long time ago.


Here is a picture of the 24+1 disc AEM provides.


Here is where it mounts inside the FWD distributor.


Here is the info from the FSM on it.

Looking at those pics I see that the VEMS and AEM discs are very similar, but different enough to make me want to buy the AEM disc. I'm sure if I tried long enough I could get the VEMS disc to work, but I'm going to order the AEM disc and avoid that headache.

So more than likely more of us might have this problem... post up the link where you buy it from.
Thanks

You apparently have to call them and go through their tech guys. They will want to make sure the disc is necessary, and they are the only ones who keep inventory on the discs so you'll need to talk to a tech directly.
I was asked to e-mail them a picture of my current CAS disc (so they know which one to send me). I've sent them the e-mail and I'm awaiting a response.

Edit: I had to be proactive and call them back before close of business day in CA. They took my info and are shipping me the CAS disc. It was $25.

Well, everything I have seen, the disc is only necessary on the RWD distributors. The FWD ones didnt' seem to have the breakup issues. I have not run across that at all my self, though I have only put aem on 4 cars and 3 of them were mild turbo setups.

Brent

Hey Ben, when you get this in you should do a quick writeup of how to swap out the disc and what settings you make in the ignition setup in the AEM PRO software. It will help a ton of people I think that move in this direction.

Brent

I know for sure the GTi-R guys have a lot of trouble with the stock CAS disc as well.

As for directions on what settings to change, I may have some insight into that later, but AEM has what looks like comprehensive directions right here.
Forum post: Nissan CAS disc
Direct link to word document: http://forum.aempower.com/forum/index.php?action=dlattach;topic=20345.0;attach=3850

Great thread!!