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post #1 of 15 (permalink) Old 04-22-2009, 06:51 PM Thread Starter
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More info on the 08 miss

Been thinking hard about this but not sure why the coils fix it.

I am thinking the issue is just too much timing is causing the miss.

When I extracted the timing curves from a Dynatek a while back the timing was higher than advertised by about 7 degrees if I remember right, I might still have my notes.

Timing has to do with when the plug fires in relation to where the piston is, the more advance the earlier it fires, if it fires too early combustion process completes before it is supposed to which is approx. 15 degrees after top dead center. Too early it should be running lean at part throttle.

So why would it do it under part throttle but not WOT? This is what got me to thinking. When the throttle is wide open more fuel enters thus it takes longer to burn the mixture because there is more to burn thus the combustion process does not finish as early as part throttle.

If someone with a programmable CDI on their 08 would simply flip the dip switches to curve one which has less timing than curve two then this would tell us if it is simply too much timing or not.

I no longer have my 08 or I would test it.



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post #2 of 15 (permalink) Old 04-22-2009, 08:53 PM
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Todd;

Interesting perspective. I just got all the stuff on I bought from you (J.G. in Nor Cal) and jetted it to your specs and it runs fine, no miss with just the Dynatek non-programmable.
These things really fire at 15 degrees ATDC? That seems to be a major step backwards, my experience is with V-8's, but I always liked 32~36 BTDC on a no nitrous no blower engine.
This problem, in my mind, is electrical. With you finding 7 degrees difference from advertised timing curves, something isn't right. Is Dynatek Q.C. up to par?
I can see people jetting themselves into a miss, but adding a box and getting the problem sems pretty clear. If changing the coils covers it, then something is going on with the coils and their interaction with the box. If the carbs are up completely on the main jets at that point, then it stands to reason the miss would get worse, not clear up, as more fuel is needed and not forthcoming. It would just lean out til it dies.
Timing could be impacted by how fast the coils saturate and discharge when signaled to do so. It does not take delay in that process to move the curve a couple of degrees. Every performance dist. I ever ran, (again, V-8) had all the timing in by 2000 RPM, or sooner. Timing not keeping up with an engine gaining RPM means, in essence, that the spark is happening later, and a miss. Firing the plug when the piston is already heading south 15 degrees on the power stroke seems like the ragged edge.
If the engines that are missing could be read on a dyno with good numbers printing I think this would be found quickly.
Helluva mystery, tho.
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post #3 of 15 (permalink) Old 04-22-2009, 09:22 PM
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Do the Teryx run the same curves as the Brute Forces?

Could you get the guy you sold your 08 in or someone local with an 08 in for testing?
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post #4 of 15 (permalink) Old 04-23-2009, 06:07 AM Thread Starter
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Todd;

Interesting perspective. I just got all the stuff on I bought from you (J.G. in Nor Cal) and jetted it to your specs and it runs fine, no miss with just the Dynatek non-programmable.
These things really fire at 15 degrees ATDC? That seems to be a major step backwards, my experience is with V-8's, but I always liked 32~36 BTDC on a no nitrous no blower engine.
This problem, in my mind, is electrical. With you finding 7 degrees difference from advertised timing curves, something isn't right. Is Dynatek Q.C. up to par?
I can see people jetting themselves into a miss, but adding a box and getting the problem sems pretty clear. If changing the coils covers it, then something is going on with the coils and their interaction with the box. If the carbs are up completely on the main jets at that point, then it stands to reason the miss would get worse, not clear up, as more fuel is needed and not forthcoming. It would just lean out til it dies.
Timing could be impacted by how fast the coils saturate and discharge when signaled to do so. It does not take delay in that process to move the curve a couple of degrees. Every performance dist. I ever ran, (again, V-8) had all the timing in by 2000 RPM, or sooner. Timing not keeping up with an engine gaining RPM means, in essence, that the spark is happening later, and a miss. Firing the plug when the piston is already heading south 15 degrees on the power stroke seems like the ragged edge.
If the engines that are missing could be read on a dyno with good numbers printing I think this would be found quickly.
Helluva mystery, tho.
I guess I didn't explain it right. You want the peak pressure pulse from combustion to happen at 15 degrees ATDC not the timing. You will get as much as 35 degrees BTDC on timing.

All this is in theory and hard for me to convey what is on my mind here.

I just need someone with the miss and a programmable box to switch it to curve one and either confirm or eliminate timing as the issue.

I really can't figure out how the coils fix it.

Todd



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post #5 of 15 (permalink) Old 04-23-2009, 08:25 AM
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Okay Todd, referring to the combustion event makes your 15 degree number make sense. Were you ever able to determine if there is a wide range of function numbers on the stock coils?
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post #6 of 15 (permalink) Old 04-23-2009, 05:14 PM Thread Starter
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They are not but Teryxpilot did some testing for me and so far curve one on the programmable one which has less timing cured the issue.


I wish someone would run their Teryx nearly out of gas and put in some premium in and see if it goes away. The higher octane would slow the burn down.



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post #7 of 15 (permalink) Old 04-23-2009, 06:09 PM
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Your running the most advanced timing with 87 octane pump gas???? I'm guessing you are likely going to have problems (miss fires).
I'm pretty sure you need the cooler burn of premium gas to run timing over 6 degrees over the stock curve. I'm just not sure how aggresive the curve of the Dyna Teryx vs the BF750 VDI curves (my basis of comparison), but I would think it would be similar.
So if you are running 87 octane pump gas and reduce the timing curve to +3-4 degrees over stock instead of +7 degrees does the miss go away? This is where I would start.
I thought that was one of the reasons these CDIs came with different curves so you could adjust the timing for the fuel octane level.
This is one of the reasons a stock CDI runs better on 87 ocatane as the timing is lower and it can run better with the hotter burning lower octane fuel and premium slightly hurts performance of a completely stock machine.

Last edited by DougS; 04-23-2009 at 06:18 PM. Reason: Added more stuff.
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post #8 of 15 (permalink) Old 04-23-2009, 07:53 PM Thread Starter
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Your running the most advanced timing with 87 octane pump gas???? I'm guessing you are likely going to have problems (miss fires).
I'm pretty sure you need the cooler burn of premium gas to run timing over 6 degrees over the stock curve. I'm just not sure how aggresive the curve of the Dyna Teryx vs the BF750 VDI curves (my basis of comparison), but I would think it would be similar.
So if you are running 87 octane pump gas and reduce the timing curve to +3-4 degrees over stock instead of +7 degrees does the miss go away? This is where I would start.
I thought that was one of the reasons these CDIs came with different curves so you could adjust the timing for the fuel octane level.
This is one of the reasons a stock CDI runs better on 87 ocatane as the timing is lower and it can run better with the hotter burning lower octane fuel and premium slightly hurts performance of a completely stock machine.

DougS,

Most people don't have the programmable and the non-programmable one has the number two of the programmable as it's only curve which is the most advanced.

The people who have the programmable one usually use curve two as it is what they call the High Performance curve.

We program the programmable ones that we sell before they go with a different curve in the stock curve location.



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post #9 of 15 (permalink) Old 04-23-2009, 09:49 PM
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Todd...i sent you a PM back in december when i got my nonprogrammable dynatek from you. I remember telling you in the messege that 2 of my riding buddies have the non programmable dyna and 1 has the programmable. The only way us with the non programmable could cure the miss was put the stock cdi back in, but the guy with the programmable one could just switch to dip switch 1 or 4..he didnt get his programmable from you thats why dip 4 uses the stock curve whereas you sell them with a more advanced curve on dip 4. we all have the dyna coils now and havent had any miss since. Back in decemeber when i wrote you, you didnt have enough complaints to look into the miss problem. I remeber you sending me a link to dynatek to return my dyna for repair which i did and it was returned stating it was functioning as designed. Thats when i went high and low trying to find a cure which got everyones attention. There pricey but the 200$ coils fix the problem.
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post #10 of 15 (permalink) Old 04-23-2009, 10:13 PM
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Todd...i sent you a PM back in december when i got my nonprogrammable dynatek from you. I remember telling you in the messege that 2 of my riding buddies have the non programmable dyna and 1 has the programmable. The only way us with the non programmable could cure the miss was put the stock cdi back in, but the guy with the programmable one could just switch to dip switch 1 or 4..he didnt get his programmable from you thats why dip 4 uses the stock curve whereas you sell them with a more advanced curve on dip 4. we all have the dyna coils now and havent had any miss since. Back in decemeber when i wrote you, you didnt have enough complaints to look into the miss problem. I remeber you sending me a link to dynatek to return my dyna for repair which i did and it was returned stating it was functioning as designed. Thats when i went high and low trying to find a cure which got everyones attention. There pricey but the 200$ coils fix the problem.
So can you run regular gas with the coils and the advanced curve with no issues?
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