High Energy Ignition (HEI)

[content22207]

Some selected posts from another thread, just to get this thread started:

I know several owners, myself included, who are running true HEI with excellent results.

Bear in mind that ignition coil secondary voltage is directly proportional to its input. You can not run only 6-8 volts into a high winding coil and expect anything close maximum rated output (most HEI coils are rated at 12-14 volts input). You will get more secondary voltage than a stock Bosch coil simply by virtue of the higher number of windings, but certainly not anything close to 40,000 volts.

Bill Robertson
#5939

Are you running 12v to the coil with the stock Bosch amp or the Duraspark you were running? I know guys run 12v to the Duraspark all the time.

I am running 12.5 volts into a Pertronix coil. Voltage is something like 8 or 9 volts to the Bosch ECU at the other end. I was only test driving a Duraspark unit for Byrne. He gave me his dead Bosch unit, which I will use to make another adapter to carry with me in case my ECU dies.

My resistor grid is wired in parallel (that is how I get 12.5 volts into the coil):
Attachment 4258
Pertronix coils can of course handle full charging voltage no problem. I only step it down for the ECU's benefit. I don't trust Bosch ECU's any further than I could throw one of the damn things. If I was running an original Ford Aerospace Duraspark ECU, I wouldn't reduce input voltage at all.

The biggest advantage of HEI is the ability to open up the plug gap. .026" is ridiculously small. No wonder stock DeLoreans run like crap. The benefits of wider plug gaps have been known for decades. Nearly every other manufacturer was already running .05" plug gaps when DeLoreans were new in the showroom. GM introduced HEI in 1971. DeLorean ignition was obsolete even before these stupid little cars were nothing more than a stainless steel fantasy in the back of JZD's mind. The man was vice president of the company that pioneered HEI, for crying out loud -- he should have known better.

Speaking of which: DO NOT OPEN YOUR PLUG GAP IF YOU ARE STILL RUNNING SUBSTANDARD DELOREAN 6-8 VOLTS INTO THE COIL, NO MATTER WHAT KIND OF COIL IT IS (can I hear an "Amen" Steve?). The stock resistor grid is really better suited for breaker points than breakerless ignition.

Bill Robertson
#5939

You can get away with smaller plug gaps in high compression and forced induction engines because the mixture is easier to ignite. Some owners claim that larger plug gaps are actually counter productive in those circumstances.

In a low compression engine, like the stock DeLorean PRV, the mixture is harder to ignite. Leaning the mixture out for fuel economy and emissions exacerbates the situation. That is one reason American manufacturers were so quick to adopt HEI in the early 70's.

A Society of Automotive Engineers' study from the time: http://dmctalk.org/showthread.php?65...ull=1#post7222
I found it particularly fascinating that wider plug gaps also yielded benefits similar to increased gap projection (you don't need to change spark plug length -- just open the gap up).

Bill Robertson
#5939

Regardless of everyone's position on the stock vs. modified coil/ignition, everyone should at least agree that the stock plug gap is pretty small.

As the years went on every car manufacturer has found a way to increase secondary voltage and with it the plug gap.

A stock system works well. That has been proven through millions of real-world miles cars with a similar setup have put on the road. What I don't understand is why a car company would base their 'new' electronic ignition around the use of an off-the-shelf coil. If they were putting the money into developing this new system why not develop a new a new coil to take advantage of the breakerless ignition?

Bosch wasn't the only one to do this. Ford did the same thing over here. I just don't understand why they would stop at 6-8v at the coil. They knew in the 60's that increased primary voltage was the way to go for performance and economy. They wouldn't have resorted to dual-point distributors (and the associated headaches) if they didn't.

In the 1970's Ford used 10.5 volts primary (Duraspark breakerless ignition). Plug gaps were .044".

Bill Robertson
#5939

Here's where I found the info I was basing my statement:

http://www.autozone.com/autozone/rep...00c15280077d43

From the above troubleshooting guide:
"If no spark occurs, measure the voltage on the battery side of the coil.

Less than 6 volts - Repair the wire carrying current to the battery terminal of the coil and repeat test.

If voltage is 6-8 volts - Substitute, but do not install, a known good module and repeat the test. If spark then occurs, reconnect the original module to verify its being defective. Replace as required. Refer to step 10 if the battery voltage is present."

This is not a Ford document FWIW.

[content22207]

1978 Lincoln, stock wiring before the coil (Duraspark ECU):
FordIgnitionPrimary.jpg

Bill Robertson
#5939

[content22207]

From another thread:

All too often someone gets the idea that bolting in a new, different part will give them better performance, gas mileage, reliability, <blank> etc. You can fill in the blanks. If it was that easy the original manufacturer would have done it. In some cases they actually do see some improvement only because the part they replaced was old, worn, the wrong one, or defective. There is little if anything to be gained by putting "performance" parts into the ignition system. If every part you could bolt on to the car added the performance each claimed you could theoretically double the HP of the car. Who is going to believe THAT! A BIG problem with deviating from stock is that it becomes near impossible for anyone to help when the car has a problem. Too many variables and no good place to start troubleshooting. For a street driven car reliability is very important. To a big extant more important than a small, temporary increase in performance. Another thing to remember is most systems are like chains. Only as strong as the weakest link meaning if you don't improve the WHOLE system, improving one part of it does not improve what the whole system can do. As Martin said, "Show Me!" Put it on a dyno and show the numbers. Till then it is just a pretty and expensive part. I swear that my car always runs better after I clean it or change the oil. A very subjective effect. After spending money on a performance part you expect the car to run better, faster, etc!
David Teitelbaum

Bullshit.

Bill Robertson
#5939

It never ceases to amaze me that a small, but supposedly "guru," contingent of this community close their eyes, stick their fingers in their ears, and shout "la la la, I'm not listening" as loud as they can whenever the subject of DeLorean ignition comes up.

In 1972, the Society of Automotive Engineers determined that ignition with higher secondary voltage, larger plug gaps, and longer spark duration improved combustion. "La la la. I'm not listening."

Nearly every car manufacturer (ie: Ford, General Motors, Chrysler, Datsun, Honda, Toyota, Subaru, Mazda, et al) started installing ignitions with higher secondary voltage, larger plug gaps, and longer spark duration in the early 1970's, and has never gone back to earlier spec ignition since. "La la la, I'm not listening."

High voltage coils cost half as much as low voltage Bosch coils. "La la la, I'm not listening."

The very cars DeLoreans were supposed to compete within 1981 had already been running HEI for years (DeLorean ignition was out of date new on the showroom floor). "La la la, I'm not listening."

Excuse me for a moment while I pick up the eyeballs that just rolled clear out of my head.

Bill Robertson
#5939

... What I don't understand is why a car company would base their 'new' electronic ignition around the use of an off-the-shelf coil. If they were putting the money into developing this new system why not develop a new a new coil to take advantage of the breakerless ignition?...

Something just occurred to me: AM radio may have been the limiting factor. AM frequencies are very liable to ignition interference. On my own cars it shows up as a distinctive "tick tick" at idle, rev'ing to a continuous static hum. I'm pretty sure Europeans listened to a lot of AM radio in the 1970's. Bosch igntion may well be designed not for combustion efficiency, but rather not to interfere with AM radio reception. How else do you explain the resistor in our rotor buttons....

Bill Robertson
#5939

[Farrar]

I have always reasoned that DeLoreans have the ignition systems they do because it was quick and cheap to simply take the PRV lock, stock, and barrel from another application and drop it in. Everything I have learned about these cars suggests to me that if they had simply had more time they could have had a better product, but time was against them so we got what we got. I wouldn't be surprised to find Peugeot, Renault, and Volvos of the late 1970s using the PRV V6 to have the exact same ignition setup -- in fact, I'd expect it.

Farrar

[content22207]

Volvos do. Even the ECU is identical (helpful hint if anyone has the opportunity to scavenge a spare from a junkyard).

Bill Robertson
#5939

[content22207]

*sigh*. No, I'm asking you to prove that with your ignition modification, you achieved anything more than could be achieved with new stock components.

My ignition is now 1981 Mustang caliber. Combined with its Mustang carburetor, #5939 is exactly 37.615% faster than a factory spec DeLorean (even with new components).

Bill Robertson
#5939

[stevedmc]

My ignition is now 1981 Mustang caliber. Combined with its Mustang carburetor, #5939 is exactly 37.615% faster than a factory spec DeLorean (even with new components).

Bill Robertson
#5939

Have you ever taken #5939 up to speed? I brought 16510 up to 105 mph but got scared and slowed down since my tires are only rated for 108 mph.

[Farrar]

Didn't you once say that your engine might have slightly different cams because it was originally intended for stationary use? I would add that to your list of deviations from stock DeLorean trim, if so.

Won't matter anyway -- Martin won't believe anything without a dyno printout.

What's the deal, anyway? Martin's happy with his car, and you're happy with yours.

Farrar

[content22207]

Have you ever taken #5939 up to speed? I brought 16510 up to 105 mph but got scared and slowed down since my tires are only rated for 108 mph.

I still have a speeding ticket on my insurance, and now am CDL for the church, so I stick to 5 MPH over.

Plus I would be a little self conscious to see helicopter coverage of my performance modified little silver car embarrassing pursuing North Carolina troopers on national news.

Bill Robertson
#5939

[content22207]

Didn't you once say that your engine might have slightly different cams because it was originally intended for stationary use? I would add that to your list of deviations from stock DeLorean trim, if so.

Test driving carb conversions, and comparing their seat of pants performance to final installation on other cars, has led me to doubt that earlier suspicion.

My manifold does move more air than either a K-Jet manifold or fabricated manifolds because its runners have square cross sections, not round. I also have a big central plenum common to all cylinders (single plane) rather than a dual plane design. The combined effect is to move my power band towards higher RPM's, which anyone who has ridden with me can confirm I reach very quickly.

As soon as I capture and edit down a short segment of video, I will post visual evidence that my car is faster than a stock DeLorean.

Bill Robertson
#5939