Will a distributor fit with stock setup?
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DR.BOOSTER said:
I can tell you what is needed with a Gen7 and BS3. You will need to ask Cal about the XFI. Cal has a C3I Adapter to do the conversion if you dont want to cut your harness.
Distributor with mag pick-up $100-$350 (New or used)
Ignition Box $170-$700 ( Dont need ignition controls with these ECMs not sure on XFI)
Coil $100
Universal length wires $50
norbs said:
I have 3 of the ACCEL 300s, already.
When you're working with basically your own code, the sky is the limit for doing things....
I've been reading thru the MSD catalog most of the evening, and the mj ratings of the various boxes are interesting. While some of the claims might be useful for the exotics, I still don't see where the real advnatage lays, other then to make up for the code that the ecm uses. Launch assist, rev limiting, over boost protection can all be done effectively with code. It would seem folks should be asking the ecm manufacturers to get the code end more compatible.
The only real difference that I see, is that the dissy sets a min firing voltage (due to the cap/ rotor air gap), but with the fast rise time of a DC that shouldn't even be an issue. Unless, some how adding the timing chain, into the equation is somehow an advantage.
EightSecV6
MDBL
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- Jul 18, 2001
bruce said:I have 3 of the ACCEL 300s, already.
When you're working with basically your own code, the sky is the limit for doing things....
I've been reading thru the MSD catalog most of the evening, and the mj ratings of the various boxes are interesting. While some of the claims might be useful for the exotics, I still don't see where the real advnatage lays, other then to make up for the code that the ecm uses. Launch assist, rev limiting, over boost protection can all be done effectively with code. It would seem folks should be asking the ecm manufacturers to get the code end more compatible.
The only real difference that I see, is that the dissy sets a min firing voltage (due to the cap/ rotor air gap), but with the fast rise time of a DC that shouldn't even be an issue. Unless, some how adding the timing chain, into the equation is somehow an advantage.
Bruce, you ABSOLUTELY must have a background in engineering.
I am looking into making the change and here's what I see. You have to have a distributor such as a MSD Pro Billet Distributor. You have to have a coil HVC or Blaster SS or similar. Then you have to have an ignition box like a 6AL or 7AL. Oh and a harness to wire it up. Does this sound correct? On cars with aftermarket engine management I would think it would be an improvement over the stock setup. Cars with a stock ECM setup may not see any gains. Now, how do you find the pros and cons of using different coils and ignition boxes? Are all of them the same or similar in function? I would guess so. It probably comes down to personal preference.
If you wanted, could even make say a unilite type distributor work with the stock SFI ecu setup with a little customization. To me the good thing about going distrib on a fast car is moving to an affordable high perf CDI ignition. If you wanted to make a VR signal distributor work, well there are converter modules from GM even in the boneyards (that process the VR pickup signal into a digital square wave) that could probably be made to work on a budget.
Seems to me there are 2 main possibilities for why power might go up in our case with a distrib. 1) Either the waste spark scheme is somehow bad for power or 2) the high performance CDI used with the distributor setup works better at high power levels and high rpm vs the stock inductive waste spark setup.
To me, 2) is a given and easy to understand. Esp the better performance at high rpm part of a CDI vs an inductive system that's trying to adequately charge and fire 3 coils in less than 10ms at > 6000 rpm. At 8000 rpm we're down to only 7.5ms available. Since the spark signal only comes out from the ecu on one EST line, and since there must be some dead band in between each spark firing pulse there is simply not enough time left to fully charge the coils at high rpm. That is probably a big issue, esp in cyls that now hold say 3x-4x + the amount of fual/air charge at wot than the stock engine did...
For 1) it seems that if the cyls are firing correctly there shouldn't be any big issues with a waste spark, no more at least than having say 1600+ deg exh gas blowing back through the cyl when the waste spark fires during overlap time. If the cyls are misfiring though (per 2) above), well maybe things could change.
JMO.
TurboTR
Seems to me there are 2 main possibilities for why power might go up in our case with a distrib. 1) Either the waste spark scheme is somehow bad for power or 2) the high performance CDI used with the distributor setup works better at high power levels and high rpm vs the stock inductive waste spark setup.
To me, 2) is a given and easy to understand. Esp the better performance at high rpm part of a CDI vs an inductive system that's trying to adequately charge and fire 3 coils in less than 10ms at > 6000 rpm. At 8000 rpm we're down to only 7.5ms available. Since the spark signal only comes out from the ecu on one EST line, and since there must be some dead band in between each spark firing pulse there is simply not enough time left to fully charge the coils at high rpm. That is probably a big issue, esp in cyls that now hold say 3x-4x + the amount of fual/air charge at wot than the stock engine did...
For 1) it seems that if the cyls are firing correctly there shouldn't be any big issues with a waste spark, no more at least than having say 1600+ deg exh gas blowing back through the cyl when the waste spark fires during overlap time. If the cyls are misfiring though (per 2) above), well maybe things could change.
JMO.
TurboTR
V6RACER said:
The ecm just tells whatevers on the other end when to fire. It's just generating the same darned *dwell* signal as the distributor would. Once you go to CD, all that unit really looks at is the point open, ie time to fire signal. With a conventional coil, dwell is important since you're trying to *saturate* the coil with just a 12v potential across the ign coil, with CDs it's ~400 volts. Using this 400 volts gives, what's called a faster rise time.
*Spark energy* is generally rated in mj. Mili-joules. An HEI is in the nieghborhood of 20-30 mj, a CD can go from 90-170 mj.. Now with a CD the coil dumps, it's potential electrical energy in just several msecs., while a conventional coil, can maintain it's potential for well over .5 sec.. So what the CD guys try to do, is generate several sparks, to make up for this lack of spark duration.
The critical part in all this thou, is what's happening in the combustion chamber. Once the coil sees the signal to fire, the voltage starts to build, across the spark plugs electrodes. As the voltage builds, there are some atoms torn off the electrodes, and this becomes the ion trail, that the spark follows (just like in the lightning photos were there are all sorts of trace spark events before the lightning strike).
There are as many manufacturing theories about ignitions, as there are cam manufacturers.. It seems all the good entry level ignition text books are now gone, and about the most informative one around nowadays, is Dr Jacobs book How to Optimise Your Ignition System. But, it's tainted since the good Dr is also selling his own brand of ignition systems. If you look up some of the patents quoted on the various ignition bits, you'll see some of the patents have little to nothing to do with the way the unit really works.
While there is some personal preference, there are some items that just don't work, or are troublesome. A quick search here, will show a trail of problems with the DIS4, but some folks have had good luck with them.
If you want to *think*, or *guess*, feel free to, but research and understanding what's going on will always make your car faster, and less prone to breakage.
For the EE's of the group, I'm just trying to put things in lay terms to answer his guestions.
TurboTR said:
One of the biggies of DIS thou, is that they are firing only 1/3 as often, and that keeps the heat way down, and the coil's resistance.
I can see the CD being the way to go, but it should work just as well with the stock coils, if not better. Since you can use one CD unit per coil, and have multispark to very high RPM levels.
It'll be interesting thou, when the newer CNP stuff and CD come on line. MSD has a whole series of new coils and spark boxes, in the latest catalog.
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