Coil Dwell, I don't think its right causing weak spark. - Page 2

Spaceball 1 · Sep 11, 2008, 05:16 PM

yes 60/8000 is 0.0075 seconds per rev and let me edit my other post i started to type to fast and inerchanged cycle and rev a few times and few incorrect times.

GrocMax · Sep 11, 2008, 05:16 PM

AEM has always had messed up coil dwell settings.
A coil dwell factor setting of 35 means 3.5mS, the dwell vs RPM and dwell vs voltage tables are multiplier tables. So if your factor was 35, and both tables were a flat 100, your dwell time is fixed at 3.5mS.

dwell max of .5 tooth is retarded, it needs to be 1 to 1.25, bit SOME trigger setups cannot tolerate settings above 1 tooth. You theoretically have 2 teeth for charge and recovery, but the way they do their triggering won't let you use all of it.

A constant charge inductive coil with a system voltage (13-14v) dwell time requirement above 3.5-4ms is very rare. The factory coil driver IC inside the coil may or may not have a current (and/or temp) limiting driver (I doubt it does having seen some IC toasted coils), so be careful. The only way you're going to find out how far you can go is by lab scoping under your running conditions and finding out at what point you get full saturation. The variables are input voltage, temp. They SHOULD have a 2D table to vary dwell with load, as you don't need full saturation at all loads, it just overheats the coil driver IC and coil.

A high dwell inductive waste spark system is RPM limited, you'll run out of charge and recovery time somewhere between 8500-9500 RPM. True 4 channel inductives don't have this time limitation.

Info- The DSM ign transistor is a current limiting type, the most you will get out of it is 7A. The 85.5-90 RX7 ign module is a 9A current limiting module with very good coils. There are automotive inductive coil specific IGBT's (direct ECU trigger) available that are capable of anywhere between below 10A and above 30A per unit.

GTVEVO · Sep 11, 2008, 07:53 PM

Quote:

Originally Posted by GrocMax

AEM has always had messed up coil dwell settings.
A coil dwell factor setting of 35 means 3.5mS, the dwell vs RPM and dwell vs voltage tables are multiplier tables. So if your factor was 35, and both tables were a flat 100, your dwell time is fixed at 3.5mS.

dwell max of .5 tooth is retarded, it needs to be 1 to 1.25, bit SOME trigger setups cannot tolerate settings above 1 tooth. You theoretically have 2 teeth for charge and recovery, but the way they do their triggering won't let you use all of it.

A constant charge inductive coil with a system voltage (13-14v) dwell time requirement above 3.5-4ms is very rare. The factory coil driver IC inside the coil may or may not have a current (and/or temp) limiting driver (I doubt it does having seen some IC toasted coils), so be careful. The only way you're going to find out how far you can go is by lab scoping under your running conditions and finding out at what point you get full saturation. The variables are input voltage, temp. They SHOULD have a 2D table to vary dwell with load, as you don't need full saturation at all loads, it just overheats the coil driver IC and coil.

A high dwell inductive waste spark system is RPM limited, you'll run out of charge and recovery time somewhere between 8500-9500 RPM. True 4 channel inductives don't have this time limitation.

Info- The DSM ign transistor is a current limiting type, the most you will get out of it is 7A. The 85.5-90 RX7 ign module is a 9A current limiting module with very good coils. There are automotive inductive coil specific IGBT's (direct ECU trigger) available that are capable of anywhere between below 10A and above 30A per unit.

GrocMax, Its nice to hear as others chime in and confirm the way I think several of us have felt and add some very good technical info so thanks. I do see your point to having a Load vs Dwell type table added but I think we know its a small chance it will happen. I think I might be able to help with temp a little bit by lowering dwell in the lower rpm ranges.

The next question I don't get is why they have the Max Dwell set at 4 on the EVO 9 base cal, sounds like possible issues could happen. I am beginning to think AEM Goofed both the 8 and 9 Max Dwell Factors.

EVO8_PR · Sep 11, 2008, 11:24 PM

Just got back from the dyno, had some slight misfires before.Today the only thing I changed was the Dwell Max to 1.0 tooth and Dwell Min to 0.1 tooth and had no problems @ the dyno. On the street I ran the car 1st thru 4th gear to +/- 135mph and no hiccups whatsoever.

GTVEVO · Sep 12, 2008, 08:23 AM

Quote:

Originally Posted by EVO8_PR

Just got back from the dyno, had some slight misfires before.Today the only thing I changed was the Dwell Max to 1.0 tooth and Dwell Min to 0.1 tooth and had no problems @ the dyno. On the street I ran the car 1st thru 4th gear to +/- 135mph and no hiccups whatsoever.

Thanks for the confirm, after I calced stuff out I was pretty sure the .5 Max Dwell was causing an early cap even with the stock Dwell vs RPM tables. Thanks for taking this test into consideration its much appreciated. If you are still running the Stock Dwell vs RPM table you should be very very safe and still have room for some improvement if needed.

I think we are onto some great findings here where the stock EVO coils can get some good use out of them.

EVO8_PR · Sep 12, 2008, 04:16 PM

Quote:

Originally Posted by GTVEVO

If you are still running the Stock Dwell vs RPM table you should be very very safe and still have room for some improvement if needed.

What would you recommend with this table? Raise the 8000 rpm to somewhere around the 65 mark and calculate to 3200? or just go flat @ +/- 100?

Spaceball 1 · Sep 12, 2008, 05:47 PM

I went flat at 100 till 8000 then -10 for each 800 from there. It really not nessary though unless you rev past 8000.

GTVEVO · Sep 13, 2008, 09:43 AM

Quote:

Originally Posted by EVO8_PR

What would you recommend with this table? Raise the 8000 rpm to somewhere around the 65 mark and calculate to 3200? or just go flat @ +/- 100?

Spaceball 1 gave a good strategy, as for myself I am running a flat 105 with max dwell at 1.25. I would say somewhere in both of our areas is going to be a good reliable setting. My car needs and wants to rev past 8k so I am going to try to get everything I can out of it. I will probably end up backing it down in the lower rpm ranges just to ensure I don't build too much heat.

awdboosted · Sep 13, 2008, 01:20 PM

I personal don't think you need to mess with the dwell.. I had a simular situation with my coils on the stock computer. I replace spark plugs. that didn't work.. Gap them tighter.. Still didn't work.. Then I replace the coils and it went away. I'll bet that you just have a bad coil or the boots just arc-gaping on you.

GTVEVO · Sep 13, 2008, 04:59 PM

Quote:

Originally Posted by awdboosted

I personal don't think you need to mess with the dwell.. I had a simular situation with my coils on the stock computer. I replace spark plugs. that didn't work.. Gap them tighter.. Still didn't work.. Then I replace the coils and it went away. I'll bet that you just have a bad coil or the boots just arc-gaping on you.

Well thats your opinion, after looking I would say the data speaks for its self. In your case with the Stock ECU ignition isn't much as a problem with the stock coils so you probably did have a bad one. But when you move over to the AEM and your coils don't seem to work as good there is a logical explanation so I figured I would find the answer and help others who also have questioned it. The generic answer of "The AEM Box doesn't drive the coils very well with the EVO" doesn't work for me because you don't hear this with other platforms. Anyone that does tuning should always be open to learning something new.

awdboosted · Sep 14, 2008, 01:50 PM

I'd agree with you about open to learning something new. After reading the thread more i kinda jump on and posted not reading everything.. Sorry about that. So are you just experiencing miss fire and thats what make you believe the wizard isn't set up properly? I just have never had a miss fire and I'm still on stock coil on the AEM.. The only miss fire I was getting is tuning with Q16.. If you get lean the car just breaks up. Give it some fuel and it goes away. Thou in the wizard The 9's dwell vs RPM and Dwell vs battery is different then the 8's

GTVEVO · Sep 14, 2008, 03:03 PM

Quote:

Originally Posted by awdboosted

I'd agree with you about open to learning something new. After reading the thread more i kinda jump on and posted not reading everything.. Sorry about that. So are you just experiencing miss fire and thats what make you believe the wizard isn't set up properly? I just have never had a miss fire and I'm still on stock coil on the AEM.. The only miss fire I was getting is tuning with Q16.. If you get lean the car just breaks up. Give it some fuel and it goes away. Thou in the wizard The 9's dwell vs RPM and Dwell vs battery is different then the 8's

To start I experienced misfire when I ran a GT3076 at 20 psi up until I gapped down my spark plugs to like .18 which is way to small of a gap to have a good burn so that right there told me the spark was weak but I ran it. With this gap new plugs would only last a few passes and I could then see misfires especially in the 3rd and 4th gear pulls at the track in the logs. The longer I ran the plugs the worse they would get so I would switch them frequently. After I kind of got sick of doing this I didn't understand why I couldn't run the stock coils as hard as others. I had local friends that was running stock plugs and stock plug gaps with GT35R kits along with Meth and pulling 30 psi on the stock ECU all day long I couldn't even run pump gas with lower boost and a smaller turbo. I have seen several others speak of this similar problem on this and the AEM boards also. Anytime some one asked about this issue all we received was the AEM seems to degrade the stock coils, I have began to believe this and that the problem couldn't be fixed. At that point I built a 1g coil setup for my car to cure my issues, I knew for a fact the stock 1g ignition is good till 700 +/- whp and on high boost levels without issues. This did fix my problem for a while on the GT3076 but as I changed the setup on my car to a PT67 I noticed it didn't seem to operate as well as it should either so I decided to revisit this issue and find a logical answer. This is the answer I have found and it seems to be right with myself and anyone else that tests it. The difference is quickly noticeable at high boost and in the higher rpm. After calculating it out it just makes sense, we are full aware that the aftermarket COP systems are much better and can generate much more spark energy but why not get everything you can out of the stock coils because it too is a very good designed system for what it is.

I never had any misfire issues on the stock ecu rich or lean and race or pump gas.

awdboosted · Sep 14, 2008, 05:12 PM

That may be another issue I've never had any misfires at 20psi. But like I said the there is no wizard for 9's but they are set up differently then the 8's That may be the case.
Also are you guys check your timing with a light gun when you are making the changes.. I was told you would need to by AEM..

GTVEVO · Sep 14, 2008, 07:16 PM

Quote:

Originally Posted by awdboosted

That may be another issue I've never had any misfires at 20psi. But like I said the there is no wizard for 9's but they are set up differently then the 8's That may be the case.
Also are you guys check your timing with a light gun when you are making the changes.. I was told you would need to by AEM..

Yes I understand there is no wizard for the 9 but there is for the 8 and they make you assume that the wizards are there to give you accurate settings and in this case it does not. Next the base cal Dwell settings are different between the 8 and 9 and there is no reason they should be to my knowledge this is why I started questioning the difference. Also questioning the Max Dwell on the 9 because it is set to 100% or 4 teeth in the base cal file for the 9 which makes no sense at all and could potentially cause someone to over dwell/heat the coils. This is just one more example that shows the base cal files need to be looked at more closely in my opinion.

I have heard so many different stories about checking the timing with a gun it isn't even funny. Yes I checked my timing and it has been adjusted correctly but it has no impact to a coil dwell issue. If changing the coil dwell is causing the ignition timing to change I think we have a whole different issue happening but I have yet to see that on issue with my car. Thanks for the heads up though. Anytime I have called AEM......well..... I will leave it at that.

Spaceball 1 · Sep 14, 2008, 07:29 PM

Quote:

Originally Posted by awdboosted

I'd agree with you about open to learning something new. After reading the thread more i kinda jump on and posted not reading everything.. Sorry about that. So are you just experiencing miss fire and thats what make you believe the wizard isn't set up properly? I just have never had a miss fire and I'm still on stock coil on the AEM.. The only miss fire I was getting is tuning with Q16.. If you get lean the car just breaks up. Give it some fuel and it goes away. Thou in the wizard The 9's dwell vs RPM and Dwell vs battery is different then the 8's

I am not really trying to start any thing, wait yes i am.... Have you even looked at a base cali that AEM gives out for cars? Most cars won't even start or run. I do not and would not trust anything given to us, including the wizards. I use them as a guide.

Take a look at the 1st and 2nd gen coil dwells they are also way different than the evo 8 and 9.