Hey guys, my single setup is running slightly above 500rwhp with stock coils an a HKS Twin Power. I currently have no breakup other ig woes. Some time back I begun collecting peices to do a direct ignition setup and now have just about everything I need.

Would you guys say to "Dont fix whats not broken" or should I switch to the DI, one coil per plug setup? Would there be any benefits over the wastespark? Perhaps IG safety, power gains, higher power capability before spark blowout etc.
The only down side I can see it that I may not be able to any longer use the Twin Power that I have since its 3 a channel unit , or rig it to the leading plugs only, or order the universal (4channel) model.

What do you think? Direct ignition, Hey or Nay???

 

the difference between direct ignition and wastespark is very simple. with wastespark the leading coil needs to fire twice for each revolution of the Eshaft, and with direct ignition it only needs to fire once.

only having to fire once doubles the time available to charge the coil, which is very helpful @high rpm.

https://www.rx7club.com/naturally-as...hread-1035364/

 

More important with direct ignition, the spark energy is used acrossed only one spark gap.
That causes the spark energy to be stronger.

This applies even with a wasted spark system like the PFC. By running two leading coils, the spark will be stronger.

 

With that said, Imay not even need a IG AMP since the spark will be stronger.
Correct??

 

Going from a stock coil /w twin power setup to an m&w cdi ignition system, I noticed zero gains @ 20 psi injecting 900cc of water. This was with 500r-sp.

thewird

 

Better Idle? Fuel economy? nothing?

 

Coils used with CDI setup?

 

M&w cdi is rubbish

Have had huge issues with these units at high hp w/i

Switch over to crane or dynatek and problems go away

 

With a coil for every plug along with the stronger spark, it allows a larger gap for better ignition.

Say I am running NGK racing plugs with a .025" gap and wasted spark on single coil.
The resulting gap is .050" plus the length of two cables.

Keeping the wasted spark but with individual coils, the spark only travels through one cable and 025". Thus I could go to a gap of .035" for better low ignition with still more power for the higher rpms and or boost or WI. GAIN GAIN GAIN!

 

No noticeable change in any regard. It ran exactly the same as before.

The M&W CDI coils...

thewird

 

Actually, I'll have to disagree with this popular misconception, and here's why: The available ignition energy will divide itself across the plugs according to the impedance present at each gap; which is most dependent upon cylinder pressure, followed by gap length. The gap impedance will be much greater for the cylinder under compression and spark energy will relate to I^2*R, so the 'compression' plug gap will be dominant. All else being equal, the current will remain essentially the same, regardless of a waste spark or direct fire setup. It is the instantaneous current flow and the gap impedance that will determine how hot the spark actually is at any given point in time.

The downside to wasted spark really seems to be the extra and/or uneven wear on the plugs (and reduced available dwell time for the 'inductive' crowd)--while the extra series plug gap in wasted spark does increase the firing voltage requirement somewhat, it also functions as a booster gap which increases the available energy at the instant the arc is established.

 

E = IR where R = r of plug gap 1 + r of plug gap 2 + r of cable 1 + r of cable 2.
Buy removing half of the equation, I will be higher across the remaining R.
That means more energy.

 

also if running wasted spark, a CDI has less time to restrike. MSD twin power only strikes twice by 3000 rpm running wastespark

 

/\ sorry, that was with the MSD 6A, have not tested the twin power

 

If you have a choice, direct fire all the way. No brainier.

As hp increase so does heat. If the plug can not dissipate the heat before the seal passes over the leading waste spark plug, it will ignite the oncoming chamber.
Also, 10deg of ignition timing at the e-shaft is not 10 deg of engine timing on a rotary.

How often do you see guys running 140+mph in the 1/4 mile with waste spark. and how many big hp PFC cars do we see on the forum. a honest 600rwhp. There's a reason....

just my 2 yen...

 

I think that has more to do with other stuff done to the car and what type of fuel your running.

thewird

 

Isn't teh factory twin coil, effectively two coils (or a single large coil with twin posts tapped at the same winding?) running in parrallel from a single ignitoer, not in series back to each other?

So both coil posts are the same polarity earthing to the block via the plug gap, not a closed loop from one post, through one lead, across the housing/centre plate/housing and back through the other plug to the other leading post? Sounds like a retarded setup to me, I don't believe one fouled leading plug (or an ignition wire falling off) will kill the other rotor? I think you are a bit mixed up bud.

 

closed loop from one post, through one lead, across the housing/centre plate/housing and back through the other plug to the other leading post

this... .. believe or not // never wondered why the timing light only works on one of the leads ?

 

I have to agree with the thewird; it has nothing to do with wasted spark, per se.

Direct fire offers a solution to some related ignition issues and seems to be preferred by purists; however, there are plenty of very fast cars that have used wasted spark--not to mention many magneto systems as well as aircraft. Distributor based systems also waste a spark--in the distributor cap.

 

Not understanding. what other stuff and what type of fuel? Are you saying if you run race gas and waste spark, there is no hp limit?
thanks.

 

are you referring to waste spark piston motors with the magneto and distributors?

 

^^ What I am saying is that a waste spark configuration, in and of itself, is not a limitation to power and that it is equally applicable to all types of spark ignition engines.

 

 

Everything has a limit and that is a silly statement. I'm saying there are more important things in making an engine go then what ignition system it is running. 7 second cars have been built with stock coils. Not saying that direct fire isn't better, but your saying you can't build a 600 rwhp car with OEM coils and its quite the opposite. That is the least significant part in a build. That is all I am saying.

thewird

 

If I am reading things correctly, I don't think he means stock coils, but stock coils on a wasted spark setup; wasted spark being the key argument. His point is not that high hp cant be achieved on wasted spark, but its not the "smartest way of doing it"

I think thats his argument