Engine finally ready for Dyno test
Discussion
I'm not sure if/how you have mapped your coil dwell time? A voltage drop to the coils is not actually an issue if you have more dwell time availible. Only at super high rpm will you run out of dwell time to charge the coils before you need to fire the plugs (obviously, if you're using a wasted spark system then it's more critical because the same coil is used for 2 cylinders).
it's worth trying to get hold of an osciloscope and a current clamp (20A rating, at least 20KHz bandwidth) and actually measure your coil charge event before and during your misfire events!
In extremis, you may find that the switching transistor in the coil driver (either in the coils or in your ECU, again, depending on what coils you have used?) has too low a breakdown voltage. (typically ~400V) in this case, the transistor will breakdown and conduct and limit the rate of change of current and hence the maximum output voltage of the coil packs. In this case, if the ionisation voltage(due to high charge density between the spark plugs electrodes) is higher than the IGBT breakdown voltage multiplied by the coil turns ratio, you're always going to have a problem. If this is the case, then two options are smaller plug gaps or a change of coil driver.
it's worth trying to get hold of an osciloscope and a current clamp (20A rating, at least 20KHz bandwidth) and actually measure your coil charge event before and during your misfire events!
In extremis, you may find that the switching transistor in the coil driver (either in the coils or in your ECU, again, depending on what coils you have used?) has too low a breakdown voltage. (typically ~400V) in this case, the transistor will breakdown and conduct and limit the rate of change of current and hence the maximum output voltage of the coil packs. In this case, if the ionisation voltage(due to high charge density between the spark plugs electrodes) is higher than the IGBT breakdown voltage multiplied by the coil turns ratio, you're always going to have a problem. If this is the case, then two options are smaller plug gaps or a change of coil driver.
Max_Torque said:
I'm not sure if/how you have mapped your coil dwell time? A voltage drop to the coils is not actually an issue if you have more dwell time availible. Only at super high rpm will you run out of dwell time to charge the coils before you need to fire the plugs (obviously, if you're using a wasted spark system then it's more critical because the same coil is used for 2 cylinders).
it's worth trying to get hold of an osciloscope and a current clamp (20A rating, at least 20KHz bandwidth) and actually measure your coil charge event before and during your misfire events!
In extremis, you may find that the switching transistor in the coil driver (either in the coils or in your ECU, again, depending on what coils you have used?) has too low a breakdown voltage. (typically ~400V) in this case, the transistor will breakdown and conduct and limit the rate of change of current and hence the maximum output voltage of the coil packs. In this case, if the ionisation voltage(due to high charge density between the spark plugs electrodes) is higher than the IGBT breakdown voltage multiplied by the coil turns ratio, you're always going to have a problem. If this is the case, then two options are smaller plug gaps or a change of coil driver.
Hi Max, Yes We went from one extreme to another with coil charge times (dwell) no change, which is what lead us to the loom, the wire to the coil is just to thin to deliver the charge, yes it is a wasted spark system but not sure what you mean by, same coil uses 2 cylinders? its 6 cylinder 6 coils.it's worth trying to get hold of an osciloscope and a current clamp (20A rating, at least 20KHz bandwidth) and actually measure your coil charge event before and during your misfire events!
In extremis, you may find that the switching transistor in the coil driver (either in the coils or in your ECU, again, depending on what coils you have used?) has too low a breakdown voltage. (typically ~400V) in this case, the transistor will breakdown and conduct and limit the rate of change of current and hence the maximum output voltage of the coil packs. In this case, if the ionisation voltage(due to high charge density between the spark plugs electrodes) is higher than the IGBT breakdown voltage multiplied by the coil turns ratio, you're always going to have a problem. If this is the case, then two options are smaller plug gaps or a change of coil driver.
The alternator, is not strong enough to give any extra voltage so there is nothing left to play with, so will also beef that up, as the engine revs. to 8k we set the lmt at 7700rpm.
Thanks for the input , was spot on to what we thought but turned to be the loom wire to thin to cope.
,
Sundance
Max_Torque said:
BTW, of you want REALLY high drive voltage for your coils (and super short dwell) then mounting some large (>5000uf) low ESR capacitors locally to the coil packs, earther directly to the negative terminals, will really help !
Looked at an amplifier its an option, but the altanator just doesnt give anything to pkay with.the Autronic R500 CDI is probably one of the best you can get but sadly only 4 channels
I have heard lots of good things about these
http://www.diyautotune.com/catalog/ign1a-race-coil...
plenty of places sell them
what plug gap r u running ?
I have heard lots of good things about these
http://www.diyautotune.com/catalog/ign1a-race-coil...
plenty of places sell them
what plug gap r u running ?
If a second wire to the coils fixed it, then it was an issue with the original wire! If changing the dwell made no difference, then increasing the voltage to the coils will also make no difference (peak spark gap voltage ISN'T in anyway linked to coil supply voltage)
The capacitor trick works whatever your alternator outputs, because it uses the caps to locally store energy, the instantaneous current in the supply wires is lower (the mean current is the same of course) so the voltage drop is lower, and hence the coil charge time is shorter. Remember, automotive coils are an inductive flyback step up devices, and NOT Transformers!
generally, misfiring that is insensitive to dwell (and hence peak coil charge current before interuption event) suggests that the firing HC pulse is "leaking out" somwhere else, be that arcing down the plug ceramic, out of any HV leads / distribution paths, or resulting in a breakdown of the firing transistor.
The capacitor trick works whatever your alternator outputs, because it uses the caps to locally store energy, the instantaneous current in the supply wires is lower (the mean current is the same of course) so the voltage drop is lower, and hence the coil charge time is shorter. Remember, automotive coils are an inductive flyback step up devices, and NOT Transformers!
generally, misfiring that is insensitive to dwell (and hence peak coil charge current before interuption event) suggests that the firing HC pulse is "leaking out" somwhere else, be that arcing down the plug ceramic, out of any HV leads / distribution paths, or resulting in a breakdown of the firing transistor.
Edited by anonymous-user on Monday 21st January 18:28
Max_Torque said:
If a second wire to the coils fixed it, then it was an issue with the original wire! If changing the dwell made no difference, then increasing the voltage to the coils will also make no difference (peak spark gap voltage ISN'T in anyway linked to coil supply voltage)
The capacitor trick works whatever your alternator outputs, because it uses the caps to locally store energy, the instantaneous current in the supply wires is lower (the mean current is the same of course) so the voltage drop is lower, and hence the coil charge time is shorter. Remember, automotive coils are an inductive flyback step up devices, and NOT Transformers!
generally, misfiring that is insensitive to dwell (and hence peak coil charge current before interuption event) suggests that the firing HC pulse is "leaking out" somwhere else, be that arcing down the plug ceramic, out of any HV leads / distribution paths, or resulting in a breakdown of the firing transistor.
There was never a problem with the old loom, the spark never blew out, this has only occurred with the new loom,
so we have now removed it to change the wire to the coils, if the problem is still there, which i doubt it will be, then I will deff look into using the capacitors, we have also re earthed at 5 points on the chassis now, Should be ready next week so will see if it has solved it. Thanks again for the input, all very helpful.
Sundance
.
The capacitor trick works whatever your alternator outputs, because it uses the caps to locally store energy, the instantaneous current in the supply wires is lower (the mean current is the same of course) so the voltage drop is lower, and hence the coil charge time is shorter. Remember, automotive coils are an inductive flyback step up devices, and NOT Transformers!
generally, misfiring that is insensitive to dwell (and hence peak coil charge current before interuption event) suggests that the firing HC pulse is "leaking out" somwhere else, be that arcing down the plug ceramic, out of any HV leads / distribution paths, or resulting in a breakdown of the firing transistor.
There was never a problem with the old loom, the spark never blew out, this has only occurred with the new loom,
so we have now removed it to change the wire to the coils, if the problem is still there, which i doubt it will be, then I will deff look into using the capacitors, we have also re earthed at 5 points on the chassis now, Should be ready next week so will see if it has solved it. Thanks again for the input, all very helpful.
Sundance
.
Edited by Max_Torque on Monday 21st January 18:28
Well finally have the new loom back, and fitted today, thought id show a few pics before it was fitted, also a oic of the new touch screen display, just waiting for the new dash to be made so it sits flush mounted, thanks Daddy Sumo,
Hoping to be ready for the 17th and meeting up with you all at Silverstone fingers crossed.
Hoping to be ready for the 17th and meeting up with you all at Silverstone fingers crossed.
GTO600 said:
Hope the new loom sorts your problem Craig, just at the start of going through the same process with a Motec system.
Thanks mate, it is a very long and sometimes tedious process to go through, but when you get it right, the benefits are worth the effort, Good luck with yours, Andyggt will be a good guy for knowledge, he also is configuring the Motec for his beast,
whats good is, if you have the patience, Juno was right, you need the patience of a saint, its def worth it in the end, I think,
but then i was decisive, now im not sure
Plumber1 said:
TuxMan said:
Well done Craig !! Keep the faith mate it will be worth it in the end !!! What's on at Silverstone on the 17th ???
Tux
Sunday service!!!! Think you have your name down for it Tux
I forget things too Hollowpockets said:
Hey Craig,
Whats the latest on this?
Think I'm going to have to make a decision quick if I'm going to do an ecu change before easter weekend.
Graham
We have had a few problems in that the ecu has highlighted other problems that had to be fixed ie fuel pressure, so now have 2 044s, and the loom wire being wrong to the coils, so now after fixing all the niggles, we are ready to do the final runs on the dyno at track and road next Tue, will post all the results on here,Whats the latest on this?
Think I'm going to have to make a decision quick if I'm going to do an ecu change before easter weekend.
Graham
Will give you my honest opinion when i see the final results, Would I do this again from scratch setting up the ecu as the guinea pig no, its to stressful, but now they have set it up, ie part throttle, cold start, overun, rev lmt, and all the throttle positions, just the finale power run to do now, so for someone else its just load the map and fine tune to your style of driving,
If the results are whats been promised, then I would recommend it, Roll on Tue.
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