Performance ignition question.

[PIPTHEREDRAM]

Its time to replace my distibuter, cap, rotor, plugs and wires. Will I see any power gain if I upgrade to MSD or some other performance oriented brand?

 

[EvilSpirit]

Probably not. The factory coil doesn't have the output to require upgraded from stock spec ignition components. Daily driver grade should work just fine.

 

[PIPTHEREDRAM]

Ok thanks, if I did the coil as well do you that would make a difference?

 

[EvilSpirit]

Not unless the stock coil is defective.

The stock coil, cap, rotor, wires and plugs all are designed to operate at a given spark plug gap and cylinder pressure. It isn't until you raise the cylinder pressure that it becomes necessary to increase the coil output, and the parts to deliver the higher output.

Healthy stock ignition components work just fine with a healthy stock engine. It isn't until engine mods raise cylinder pressures and power output that it is necessary to upgrade the ignition system.

An aftermarket 50K "hot" coil and a 15K stock coil will both fire the spark plugs at only 11K if the plug fires at that, which (to over-simplify) is determined by cylinder pressure and plug gap.

OK, now let's say the plugs wear, gap increases, and the voltage needed to fire the plug is now 18K, which is over the stock ignitions 15K rating, causing a misfire. The 50K system would still fire fine at this point. In this case here, the "hot" ignition system makes more power, but in reality the real answer is simply fresh plugs.

Make sense?

 

[dapepper9]

Actually better wires are a great upgrade. They don't offer more power but more reliability. Factory wires are small and the low level of shielding allowed cross-talk. For more understanding, Google "5.9 wire routing tsb". Well known issue that if you have them crossing they'll transit their signals to each other causing misfires. Thicker wires really don't care how they're routed.

Regarding the coil, it's not that it doesn't have the strength for aftermarket components. If that was the case your vehicle wouldn't run on oe parts because aftermarket has much less resistance. The problem is it's plenty strong until you start getting into engine builds involving boost or nitrous where you're blowing the spark out. In that case an msd ignition box is the fix. Just aftermarket coils don't do anything but offer less reliability and headache

 

[dapepper9]

Also stock coil is 34-38k for those wondering

 

[Yeret]

I'm running a set of Davis Unified Ignition plug wires in combination with their distributor cap and rotor. A bit expensive, but very nice stuff. I mainly went with them because I planned on a set of headers and the wires have a heat-resistant jacket that encases the wires. 2+ years later and they're holding up to the heat just fine.

The wires also snap onto the wires with a very noticeable "click," much better than other wires I've used in the past where you weren't sure if they snapped on or not.

 

[EvilSpirit]

Also stock coil is 34-38k for those wondering

Yeah, I was just using the low number to prove a point - my post was directed at ignition function in general, and not really specific to Mag engines components. Modern tech guys miss the fun of the old Sun scopes and seeing the effects of dwell on timing, spark plug gap on secondary voltage, etc. You could watch changes to secondary voltages real time on the oscilloscope when you moved plug wires around and induced misfire from "crosstalk".

It's been a long time practice to try to duplicate the factory routing when changing secondary wires. GM had some problems in the early 80's where poorly routed secondary wires was inducing current into a sensor, with the end result being broken pistons from incorrect timing induced detonation.

Kind of a neat take on how spark plug firing demands determining secondary voltage. On the 14.5+ compression 468's the shop I worked at raced in the mid 80's it was common practice to have to index the plugs to direct the fire into the chamber and to keep the huge piston domes from smashing the ground electrodes flat. Our cure was to cut the ground straps off the plugs and "surface fire" them. This was brutal on the secondary ignition parts, mostly the rotors. Cap and rotors lasted about 10-12 passes.

 

[dapepper9]

Indexing is still pretty common for people looking to eek out everything they can. If nothing else it helps with misfire chances. My new engine the plugs will be indexed for sure

Dwell is a pretty interesting piece of data to look at when you're comparing performance engines, lol theres a reason no manufacturer uses a single coil over COP/CNP systems. Also why soooo many convert to COP/CNP systems

 

[EvilSpirit]

With the racing spark plugs available off the shelf today, from the electrodes being pre cut back to uncover the tip, to ring gap plugs, having to index plugs is all but obsolete. That was another common trick - to cut the ground strap back so it only covered 1/2 of the center electrode tip. It showed the spark into the cylinder without being shrouded by the ground strap, no matter how it was indexed. I know both NGK and Champion offer "altered" electrode plugs. Granted, part number availability is limited, and they do cost a little more, but on cars that have tight header clearance it isn't worth the time to index plugs. To each their own.

 

[EvilSpirit]

With the racing spark plugs available off the shelf today, from the electrodes being pre cut back to uncover the tip, to ring gap plugs, having to index plugs is all but obsolete. That was another common trick - to cut the ground strap back so it only covered 1/2 of the center electrode tip. It showed the spark into the cylinder without being shrouded by the ground strap, no matter how it was indexed. I know both NGK and Champion offer "altered" electrode plugs. Granted, part number availability is limited, and they do cost a little more, but on cars that have tight header clearance it isn't worth the time to index plugs. To each their own.

 

[EvilSpirit]

Sorry about the multiple posts.

 

[dapepper9]

I use NGK BKR6E and new engine will be BKR7E. Nothing special with straps, single plain one old school style. Most of the fancy strap designs today are more gimmick than anything. Depending on the plug used, indexing is still quite relevant today in my opinion. It's not a hp booster or anything like that but it does offer a quicker more complete burn. Biggest thing is the extra misfire resistance. With my build im doing anything and everything i can do take that down; aluminum heads, tight quench, peak cylinder pressure at higher rpm, quality ignition components, etc. Im stuck with 91 octane fuel and 10.2:1 compression and boost might want more

 

[EvilSpirit]

I use NGK BKR6E and new engine will be BKR7E. Nothing special with straps, single plain one old school style. Most of the fancy strap designs today are more gimmick than anything. Depending on the plug used, indexing is still quite relevant today in my opinion. It's not a hp booster or anything like that but it does offer a quicker more complete burn. Biggest thing is the extra misfire resistance. With my build im doing anything and everything i can do take that down; aluminum heads, tight quench, peak cylinder pressure at higher rpm, quality ignition components, etc. Im stuck with 91 octane fuel and 10.2:1 compression and boost might want more

You do realize that both the plugs you list have ground electrode straps, right.

While there are IMO some gimmick plugs out there with unique approaches to their ground electrodes (straps), the practice of trimming the straps back, along with the factory ones that the strap actually comes into the side of the center electrode are proven designs.

One of the best ways to prevent misfire is to use the correct heat range plug.

And if you choose to use plugs that have to be pointed in the correct direction to direct the spark into the chamber, thinking they are better than the ones that direct the spark into the chamber no matter which direction they are pointed are better - by all means, you do that. I can tell you that my Eddy headed 11.0:1, 480hp 360 shows the same flame travel in all the cylinders with non indexed trimmed plugs.

Good luck with your new build. Hope it does everything you want it to do. Great to see a younger crowd still getting their hands dirty and turning wrenches instead of video games.

 

[dapepper9]

Quite aware they have ground straps. In fact the same design that has been used for years and the same design that caused people to start indexing them for years. They don't HAVE to be pointed in any direction whatsoever but it does HELP to not have the point of ignition go around the strap.

Yes, the benefits are minimal at best. Im not denying that. However, there's something to be said for evening things out between each cylinder so that it's all the same. It's a lot like balancing the rotating assembly, having each piston/rod be the exact same weight. Yes it's not nearly as critical, not trying to make it seem that way. But the more you can have every system balanced the more predictable and repeatable your results can be.

Am i going overboard? Oh yeah, that was established when i purchased billet splayed 4 bolt main caps lol. But i am going to have about 7k wrapped up in just the engine all said and done and im doing a lot of little things that a lot of people forget about to make this whole thing worthwhile. I'd kind of like to do a different platform for my next engine and not have to redo this one

 

[dapepper9]

The whole point in indexing is consistent flame travel throughout the cylinders really.

 

[PIPTHEREDRAM]

Awesome, thank you.