Misfire /breakup and high rpm with stand alone AEM infinity

[tioga]

Just in case someone else has this same problem I thought I would share my problem and solution. I have a 3.0l with itb’s GM LS indivual coils and am running a 60-2 tooth wheel on the crank with a Hall effect sensor and single window reluctor in the old distributor housing for a cam sensor. This setup ran great to 5-6k the more load the lower the problem would occur like a secondary ignition problem but not a ordinary one. No amount of new plugs,  coils, wires, harnesses would have any effect. The only thing that did was closing the plug gap down to a very small gap and I could see 6k but no more. The LS coils I was using are known to be good for 1,000hp turbo cars so no reason I should see problems on a 300hp NA motor. Finally I made yet another coil bracket this time using coil on plug coils and using a aluminum bracket with stainless tubes press fit in that run all the way down to the plug. This shields the coil just like OE setups where the coil is in a plug well surrounded by aluminum. Fired it up today and 7,500 with no sign stopping. Pulls hard as far as you want to twist it. In photo two you can see sitting on the cowl the last coil setup I had and the last photo shows a even earlier version.

 

Edited January 10, 2019 by tioga

[NewZed]

32 minutes ago, tioga said:

Finally I made yet another coil bracket this time using coil on plug coils and using a aluminum bracket with stainless tubes press fit in that run all the way down to the plug. This shields the coil just like OE setups where the coil is in a plug well surrounded by aluminum.

 

Shielded from what?  RFI or heat?  Is it the shield that made the difference or the COP coils?

 

No offense.  You described doing some stuff but it's not really clear why you decided to do it or why it worked.

[HuD 91gt]

I had some weird stuff go on with my LS could too. Turned out they were knockoffs.

[tioga]

My last coil design was to get the Most noise  rejection as possible. (RF and electro magnetic) Heat was not a issue. The coils I had used before were genuine GM and Denso. Both reputable brands and exactly the same problem. Plug wires were custom made magnicore and a set of NGK off the shelf corvette wires. Numerous different spark plug types were explored. The fact that the amount of coil output determined the onset of the problem, power supply and ground as well as failed components were eleminated, coil output more than enough to make the power we are making leave us with a noise interference problem. 

[NewZed]

Seems like a simpler shielding method would have worked.  Shielded wire alone maybe.  That's a lot of aluminum for an electrical interference problem.  Good luck, thanks for sharing. 

[tioga]

4 hours ago, NewZed said:

Seems like a simpler shielding method would have worked.  Shielded wire alone maybe.  That's a lot of aluminum for an electrical interference problem.  Good luck, thanks for sharing. 

 

 

Seems like it but did not.  I did when trying to isolate the problem wrap everything in aluminum foil attached to ground. Remaking my harness with twisted pairs, Rerouting my harnesses away from possible sources of noise etc. This did nothing for the problem. The bulk of the aluminum is to get me a mounting surface lined up with the plugs. The business end is the tube the coil is housed in. And maybe just this coil would work on its own but you need a way to support it and these coils are designed to simply push in the head so the tube solves the mounting issue while adding a shield at the same time. The reason I posted it was because it was a strange and persistent problem that many simple efforts of correcting did nothing to help. This leaves you questioning everything.  I was simply trying to share my experience so someone else might find the solution quicker than I did. There are people selling a bracket for the LS coils just like mine. I am not saying that you should not use that bracket or the coils but if you run into a strange problem with it/them then maybe you will remember this post and find your problem where I did. I own a European auto repair shop and have been professionally repairing European cars for 30+ years and have owned and built 70-78 z cars longer than that. I can tell you this was a very difficult problem to figure out. You have to take into account that when you encounter something like this it is not just something that pops up on a running engine. You have likely just changed a large amount of parts going to a complete stand alone system as I did or just a ignition system. New ecu, new harnesses, new crank and cam sensors, fuel delivery system, new ITB’s, tps, etc. and in my case a new motor plus the tune you are working on . This leaves a lot places to look for the cause. 

Edited December 29, 2018 by tioga

[madkaw]

I keep reading your first post , but not sure I understand your symptoms . So basically the engine wouldn’t go past 6k because of noise from the coils?

 

I haven’t had issues -except lately, and I’m not ready to blame my coils. I’ve been running my D-585’s for years . But maybe my mounting design helps me? 

 

Interesting!

[tioga]

20 minutes ago, madkaw said:

I keep reading your first post , but not sure I understand your symptoms . So basically the engine wouldn’t go past 6k because of noise from the coils?

 

I haven’t had issues -except lately, and I’m not ready to blame my coils. I’ve been running my D-585’s for years . But maybe my mounting design helps me? 

 

Interesting!

Your design down low may help. I am running two knock sensors down there and chose to move up for that reason. 

‘Yes the motor would start to pop and backfire at 6k like the timing was erratic. This first led me to thinking I had crank sensor issues. 

[madkaw]

So maybe you were having CAS issues from the noise ? 

 

My CAS is on the flywheel on opposite side of motor .

[tioga]

3 minutes ago, madkaw said:

So maybe you were having CAS issues from the noise ? 

 

My CAS is on the flywheel on opposite side of motor .

It did not show up when scoping the crank sensor  Mag and Hall effect sensors with wiring run outside the engine bay did nothing to help.  AEM showed no crank errors. It seems like the coils were self triggering. And yes I am sure the dwell was correct and tried various dwell settings from low to high as well as spec for the coil used. 

[tioga]

My CAS is also on opposite side but damper end. 

[madkaw]

I’ve  noticed when checking timing,  that the coils on 4,5,6 flicker twice the speed of 1,2,3 ? 

 

[madkaw]

So were those originally d585’s you were having issues with?

[NewZed]

1 hour ago, tioga said:

I own a European auto repair shop and have been professionally repairing European cars for 30+ years and have owned and built 70-78 z cars longer than that.

 

This would have been good to put in the first post.  Without it you're just an unknown person reporting random actions.  Just saying, we're all mostly strangers out here.

 

Interesting problem.  Not even going to guess at the root cause.  Did you open up the gap on your plugs?  Back to where you wanted to be?

 

Good luck.

 

 

[tioga]

2 minutes ago, NewZed said:

 

This would have been good to put in the first post.  Without it you're just an unknown person reporting random actions.  Just saying, we're all mostly strangers out here.

 

Interesting problem.  Not even going to guess at the root cause.  Did you open up the gap on your plugs?  Back to where you wanted to be?

 

Good luck.

 

 

Not yet. Just drove the one day but many trips to 7,500+ so feel confident the problem is gone. I have never been able to get past 6k wide open before.  Been raining ever since I installed  but I  plan to open the gap back up. I also need to fine tune the upper end of my fuel map. My VE table is just extrapolation in that area since I could never get there. 

[tioga]

12 minutes ago, madkaw said:

So were those originally d585’s you were having issues with?

First were D581’s, and second set were D585’s

[tioga]

In reading about automotive Rf interference it is known that flat plains of metal are never good. That is hard to avoid when trying to mount 6 coils for a inline 6. When you think about the intended use of these coils there are only 4 beside each other then on the other side of the motor 4 more.  That seems like that might make the noise issue occur at a higher rpm than 6 beside each other. Maybe not but something to think about. 

[tioga]

When you look at OE coil setups they are usually buried in a tunnel in the head which is it’s own shield and when not like on the newer plastic valve cover n52 bmw motor where a good portion of the business end of the coil is surrounded by plastic there are metal inserts in the valve cover that are sourrounding the coil. These fit in the head and up through the v/c. They are grounded where they push into the head. They didn’t add these for the hell of it. 

 

[madkaw]

I’ve been redlining my motor ever since I had these coils- 7200 rpm. 

 

Ill try and get a better pic of mine , but the coils are “ notched” into the square tubing. Hard to believe that small in set makes a difference over mounting on flat stock,  but maybe my coils aren’t being loaded as heavy as yours with a smaller displacement motor ? You said there was a direct correlation to loading ? 

 

[madkaw]

Have you ever noticed the timing light issue I mentioned . Definetly a diffferent pattern on last 3 cylinders