After upgrading the cam, rockers, carb and headers on my 2001 ZZ4 the past couple of years, I’m considering upgrading the ignition. One option is the Davis Unified Ignition HEI upgrade kit. 50,000V up to 7000 RPM and an upgraded ignition module which will increase the dwell. Couple this with low resistance 10mm ignition wires and they state I can open up the gap on the plugs which will help with performance.
Anyone gone this route? What has been your experience?
Ignition Upgrade
Re: Ignition Upgrade
Another great option would be MSD. It's what I have
used on both my BH's. You can go with just a MSD 6A
spark box or the box and billet distributor, which is
what I always have done. 7,000 RPM??? Why and When??
The MSD spark box will spark the plug 5 time each
time it fires below 2,500 RPM's.
IMHO MSD is the best way to go.
Paul H
used on both my BH's. You can go with just a MSD 6A
spark box or the box and billet distributor, which is
what I always have done. 7,000 RPM??? Why and When??
The MSD spark box will spark the plug 5 time each
time it fires below 2,500 RPM's.
IMHO MSD is the best way to go.
Paul H
Re: Ignition Upgrade
I agree with Paul H, the MSD have been around forever and they really work good. I still haven't done a thing to what mine came stock with but the MSD will go there if mine ever gives me the slightest bit of trouble.
Las Vegas, NevadaRe: Ignition Upgrade
I can't see the advantage of upgrading the ignition unless your having a problem with the stock ignition . It's been proven that there is no huge noticable performance gain .
Re: Ignition Upgrade
I'm a fan of multi spark. I put a Crane multi spark setup on Joe's 383 with their external coil. There was enough room to put it behind the carb. He and I both noticed a difference in starting and the roll on feel. Especially the roll on. I suspected in his case that the timing curve just happened to be "near perfect" for the parts combination in his engine for lack of any other reason for such a significant change. Maybe his original HEI curve was "off" some.?? I later put that Crane setup on my 408 because of that. I used the MSD 6al and Blaster 2 coil on the trike, and have no regrets. That sends 560 volts into the coil. They're not kidding when they say don't accidentally touch the post when its running.... 
Re: Ignition Upgrade
Found this on a Z28 site. Credit to Damon.
FORGET VOLTAGE! Voltage is IRRELEVANT. It only takes 10-20K volts to jump the plug gap even under the most brutal conditions in a street/strip engine. "High voltage" coils are marketing crap talk. What matters is TOTAL SPARK ENERGY. Voltage is what it takes to strike an arc between the plug's electrodes, but once that's accomplished total spark energy is what KEEPS it arcing until the coil is fully discharged again and gets the A/F mix properly ignited and initiates a controlled combustion. THAT is what matters.
So back to the limitations of the HEI.....
Biggest one is the coil. Stock coils take a long time to reach saturation (full power). Doesn't matter at modest RPMs becuase there's plenty of time between plug firings. But by ~4500 they begin losing spark energy at an astounding rate. Remember the HEI was designed in the emissions era when they wanted a STRONG spark for good emissions performance but the engines of the era never went over 5000. Sotck HEIs are WELL suited to this task. They still have plenty of wollop left to fire most performance street engines to 6000, however, even though spark energy is falling off rapidly. Good enough that you'll proably never notice the difference. Even on a dyno you probably won't see but a handfull of horsepower.
Some (not all) aftermarket coils can reach saturation much more quickly. The MSD coil, for instance, can charge in literally HALF the time of a stock coil, although it doesn't have as much total spark energy as a stock coil, it can keep making that same spark energy over and over to a much higher RPM.
Remember I said that SOME aftermarket coils are like that. Others choose a different route- they have similar saturation times to stock but produce MORE total spark energy. This often makes them feel very "peppy" around town in modest RPMs and quick throttle stabs, but they still bleed off energy on the top end like a stock coil.
I'm sure there are other coils that play a balacing game between the 2 extremes.
The Module is the second restriction. 2 limitations:
1. Amperage limitation. Stock HEI modules have current limiting circuitry built in to them. They max out at 5 amps current flow through the primary coil windings when the coil reaches full saturation. Amperage relates directly to total spark energy. More amps, the more spark energy. Aftermarket modules often have higher amperage limits- 6,7,8 amps or so. That is why coils and modules are often sold as a set- they're designed to work as a team. In the case of the MSD coil it makes a lot LESS spark energy than the stock coil if paired with a stock module, so they pair it with a higher amp module to bring that total energy back up. You end up with the best of both worlds- a spark that's as strong as stock in the low/mid RPMs (give or take a little) but one that can go to much higher RPMs before it starts losing energy.
2. Minimum dwell time. Again, circuitry that's built into the module will reach a limit at a certain RPM and won't give the coil enough time to charge/discharge, which again leads to declining spark energy in the upper RPMs. Aftermarket modules (some? all?) have a reduced minimum dwell time and can perform this function to a higher RPM before it again becomes a problem.
Odds-n-ends......
In-cap coils..... yeah, they suck, but not because they can't deliver the goods. It's becuase they can "bake" up there on top of the distributor, under a plastic cover with no good way to dissipate heat, causing failure eventually. A remote, oil-filled canister-type coil is much better for temperature survival, but the rules which govern how much total spark energy it can deliver are NO DIFFERENT from that little coil sitting on top of a stock HEI.
HEI magnetic pickup..... they work good. Way past where you'll ever need to take them. Don't worry about them, they do their job quite well.
FORGET VOLTAGE! Voltage is IRRELEVANT. It only takes 10-20K volts to jump the plug gap even under the most brutal conditions in a street/strip engine. "High voltage" coils are marketing crap talk. What matters is TOTAL SPARK ENERGY. Voltage is what it takes to strike an arc between the plug's electrodes, but once that's accomplished total spark energy is what KEEPS it arcing until the coil is fully discharged again and gets the A/F mix properly ignited and initiates a controlled combustion. THAT is what matters.
So back to the limitations of the HEI.....
Biggest one is the coil. Stock coils take a long time to reach saturation (full power). Doesn't matter at modest RPMs becuase there's plenty of time between plug firings. But by ~4500 they begin losing spark energy at an astounding rate. Remember the HEI was designed in the emissions era when they wanted a STRONG spark for good emissions performance but the engines of the era never went over 5000. Sotck HEIs are WELL suited to this task. They still have plenty of wollop left to fire most performance street engines to 6000, however, even though spark energy is falling off rapidly. Good enough that you'll proably never notice the difference. Even on a dyno you probably won't see but a handfull of horsepower.
Some (not all) aftermarket coils can reach saturation much more quickly. The MSD coil, for instance, can charge in literally HALF the time of a stock coil, although it doesn't have as much total spark energy as a stock coil, it can keep making that same spark energy over and over to a much higher RPM.
Remember I said that SOME aftermarket coils are like that. Others choose a different route- they have similar saturation times to stock but produce MORE total spark energy. This often makes them feel very "peppy" around town in modest RPMs and quick throttle stabs, but they still bleed off energy on the top end like a stock coil.
I'm sure there are other coils that play a balacing game between the 2 extremes.
The Module is the second restriction. 2 limitations:
1. Amperage limitation. Stock HEI modules have current limiting circuitry built in to them. They max out at 5 amps current flow through the primary coil windings when the coil reaches full saturation. Amperage relates directly to total spark energy. More amps, the more spark energy. Aftermarket modules often have higher amperage limits- 6,7,8 amps or so. That is why coils and modules are often sold as a set- they're designed to work as a team. In the case of the MSD coil it makes a lot LESS spark energy than the stock coil if paired with a stock module, so they pair it with a higher amp module to bring that total energy back up. You end up with the best of both worlds- a spark that's as strong as stock in the low/mid RPMs (give or take a little) but one that can go to much higher RPMs before it starts losing energy.
2. Minimum dwell time. Again, circuitry that's built into the module will reach a limit at a certain RPM and won't give the coil enough time to charge/discharge, which again leads to declining spark energy in the upper RPMs. Aftermarket modules (some? all?) have a reduced minimum dwell time and can perform this function to a higher RPM before it again becomes a problem.
Odds-n-ends......
In-cap coils..... yeah, they suck, but not because they can't deliver the goods. It's becuase they can "bake" up there on top of the distributor, under a plastic cover with no good way to dissipate heat, causing failure eventually. A remote, oil-filled canister-type coil is much better for temperature survival, but the rules which govern how much total spark energy it can deliver are NO DIFFERENT from that little coil sitting on top of a stock HEI.
HEI magnetic pickup..... they work good. Way past where you'll ever need to take them. Don't worry about them, they do their job quite well.
Dave
Re: Ignition Upgrade
I guess it depends on how much you want to spend to gain a little seat of the pants performance feel .I'd make sure your bike is tuned perfectly first and then see if a new ignition change performance . If you see a big difference I may do the same to mine .
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The Mindless Philosopher
- Posts: 422
- Joined: Mon Jul 04, 2016 3:24 pm
Re: Ignition Upgrade
This is on my list of planned upgrades now that I'm on the road again. Hoss could always use a little extra spark regardless of any perceived performance gains. Functional choke on the 1901 or not, she's just crabby in cool weather. Always has been. Some extra spark could help remedy that? Even if it doesn't, it would beat burning up those cheap GM ignition modules that never really seem to last for very long.Paul H wrote:Another great option would be MSD. It's what I have
used on both my BH's. You can go with just a MSD 6A
spark box or the box and billet distributor, which is
what I always have done. 7,000 RPM??? Why and When??
The MSD spark box will spark the plug 5 time each
time it fires below 2,500 RPM's.
IMHO MSD is the best way to go.
Paul H
I already have the billet distributor.
-
The Mindless Philosopher
- Posts: 422
- Joined: Mon Jul 04, 2016 3:24 pm