GM HEI: Cheap and Extremely Effective Ignition Upgrade

If it's broken or just needs tweaked

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Pinhead
Posts: 611
Joined: Thu Jan 04, 2007 2:26 am

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Sun Apr 17, 2011 10:38 pm

klougnot wrote:Hi Pinhead,

I got a couple quck questions about this project.

1. I want NGK 0 ohm plugs so I can use Iridium plugs. So I need a model number if you got it.

2. What kind of plug wire do I need to hook up the caps to the coils. Any details here would help out alot.

Thanks!

-Kyle


The NGK Iridium spark plugs that I've found are 5k ohms each. As far as I'm concerned, with the power that these coils are capable of, I don't think iridiums are needed. If you still want to use them, though, the PN is DR8EIX. Note the "R" in the part number indicates that it is a resistor plug.

If you do go with Iridiums, be sure to experiment with your plug caps; I haven't decided if the bike runs better with resistor plugs and plug caps or if it runs better with only resistor plugs.

Theoretically, with the lack of turbulence that the hemispherical chambers produce, a longer spark duration would help ignite the mixture (more resistance in the plugs slows the discharge and therefore extends the spark duration).

However, there's another theory that says we want a good, strong initial spark to get the flame front to start to expand as quickly as is possible.

I haven't figured out which way is best for our machines (and my results will likely be different than a stock bike due to my highly modified engine).

I've been running the HEI system with DR8EIX's without plug resistors and it seems to work well, so I believe either way will suffice in a stock engine.

When it comes to the spark plug wires, I just bought a set of 7mm Accel universal SuperStock wire and used the "spark plug end" on the coils and screwed on my stock CB650 spark plug boots on the other end.

klougnot
Posts: 149
Joined: Wed Jun 02, 2010 1:05 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby klougnot » Mon Apr 18, 2011 1:26 pm

Much Thanks Pinhead!

So what are those no resistor plug caps anyway? I want a set of NGK plug caps without resistors. I have searched the internet with no luck.

Thanks!

-Kyle

Pinhead
Posts: 611
Joined: Thu Jan 04, 2007 2:26 am

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Mon Apr 18, 2011 2:08 pm

Your stock plug caps should have removable resistors. Use a flat-head screwdriver in the plug end and unscrew the stop... Behind that is a resistor and a spring.

If you want to run resistorless, simply remove the resistor and replace it with a slug (pipe, bolt, etc) of the same diameter and length.

klougnot
Posts: 149
Joined: Wed Jun 02, 2010 1:05 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby klougnot » Tue Apr 19, 2011 4:57 pm

Thanks Pinhead!

engineuity
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Joined: Sat May 07, 2011 4:57 pm
Location: New Jersey

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby engineuity » Sat May 07, 2011 5:07 pm

Has anyone else tried the upgrade? I have a stock (i think) '80 650 and it had a tough time starting at a 'cold' ~50*...

Would there be a possibility of running the modules with something like a CPU heatsink instead of an aluminum plate? It should make the modules separately mountable or at least cut down the application size.

Thanks

Pinhead
Posts: 611
Joined: Thu Jan 04, 2007 2:26 am

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Tue May 17, 2011 7:05 pm

Sorry for not getting back to this thread earlier.

Here's the diagram to make the 7-pin HEI modules usable on our bikes. These modules seem to be much more plentiful at the junk yard.

EDIT: R1 is 1k ohm
Attachments
7-Pin HEI.jpg
7-Pin HEI.jpg (30.16 KiB) Viewed 10635 times

sicj
Posts: 12
Joined: Sun Mar 20, 2011 10:53 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby sicj » Thu May 19, 2011 11:24 pm

So I upgraded my 81 cb650 to this mod. I wired it as shown for the 4 pin module and got no spark. then I tried another version of wiring the system...

I still had no spark. Then all I did was disconnect the ground wires of the ign pickups and the bike received huge spark from the GM coils.

I don't know why either version wired as shown did not produce spark but the moment I took the ground away from the yellow/blue wires (with white sleeves) of the pickups, I then had spark.
Attachments
modulewire.png
modulewire.png (86.75 KiB) Viewed 10626 times

Pinhead
Posts: 611
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Fri May 20, 2011 12:49 am

Welcome to the board!

You have the negative side of your reluctors floating (hooked up to nothing)? Or do you have the negative side grounded?

But you say you have spark now... Have you run the engine?

You're the only other forum member that I know of that has tried the mod. Be sure to post how it works for you!

sicj
Posts: 12
Joined: Sun Mar 20, 2011 10:53 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby sicj » Fri May 20, 2011 1:30 am

the negative wires are soldered together and hooked up to nothing.

The diagram you posted did not work, nor did the diagram I posted, until I disconnected the negative pickup wires from the module circuit. And I did that out of pure frustration since EVERYTHING in the new IGN circuit I built checked out.

The moment I disconnected the neg wires fromk the circuit the spark plug wires were arcing 1-2" away to the engine case once I hit the starter button! I knew I had spark then.

Bike fired up after 3 tries (sitting for 2 months) but I bought the bike with K&N filters and no exhaust so low idle response is garbage until I get past ~3k rpm. Going to take it to a local shop to see if can be rejetted/tuned within reason.

running NGK DR8 plugs (.040" gap), Mallory 8mm wires, GM coils, ign pickups @ 490 ohms each

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Volker_P
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Volker_P » Fri May 20, 2011 1:38 am

Welcome here! :D
In fact I don't know that module, but the scheme and your result may suggest that possible the G and W input terminals may need to be changed (Hi/Lo signal inputs?).
This may imply that you now have simultaneous ignition of 2+3 and 1+4 every 180°. Would check that out.
If you don't use the stock pickups, polarity might be inversed.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

Pinhead
Posts: 611
Joined: Thu Jan 04, 2007 2:26 am

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Fri May 20, 2011 9:05 am

If the polarity of the reluctors are reversed as Volker has suggested, your ignition advance will be severely retarded (could be causing the slow/poor throttle response).

However, Volker, it won't be the module terminals that are reversed; the W terminal has a "bias voltage" present that varies with RPM for use on a V8 engine whose coil needs increasing dwell as RPM rises.

I'd try taking the two wires that you have tied together and connect them to ground. If the bike won't run in that configuration, the reluctors' polarity is likely to be reversed.

I agree with Volker; it seems that the configuration in which you have the system wired should produce a spark on all 4 cylinders every 180 degrees... Though with the polarity going back-and-forth, the modules may be ignoring the reverse-biased voltage from the opposite reluctor.

I'd try reversing the polarity of the reluctors and tie one side to ground. If that works, disconnect the negative side from ground and hook it to the 1.4v source, which increases the reluctor signal strength.

sicj
Posts: 12
Joined: Sun Mar 20, 2011 10:53 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby sicj » Fri May 20, 2011 10:02 pm

Yes I have tried to do a simple ground on the two reluctor negative wires (white sleeves), which resulted in no spark.

I don't understand how the reluctor polarity could be reversed? I used the stock connector and wired that to the modules. strange.

thanks for the tip! I will try this and report back

sicj
Posts: 12
Joined: Sun Mar 20, 2011 10:53 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby sicj » Sat May 21, 2011 12:04 am

So I switch the wires around and tried agiain...

-blue & yellow wires (w/ white sleeve): now connected to the G terminals on the modules.
-bare blue & yellow wires: connected together and grounded
result: One intial spark the moment the starter button is pressed. No spark when holding the button

-blue & yellow wires (w/ white sleeve): now connected to the G terminals on the modules.
-bare blue & yellow wires: connected together and NOT grounded
result: no spark

FOR REFERENCE
I only get spark with this configuration...

-bare blue & yellow wires: connected to the G terminals on the modules.
-blue & yellow wires (w/ white sleeve): connected together and NOT grounded
result: spark


I must be getting spark every 180* like you guys have suggested. I've only driven the bike once since I bought it and when it had the stock IGN system setup I had good response off idle.

Now, with the GM HEI system, I have snappy idle response but under load it bogs bad till about 3k rpm then opens up.

engineuity
Posts: 2
Joined: Sat May 07, 2011 4:57 pm
Location: New Jersey

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby engineuity » Mon May 23, 2011 8:58 pm

Now, with the GM HEI system, I have snappy idle response


Is that better than it was before? What about starting?

This is likely going to be my first upgrade. I dont have idle issues, just cold starts

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Volker_P
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Location: southern Germany

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Volker_P » Tue May 24, 2011 3:01 am

To reverse the polarity of the reluctors, you probably have to swap cables blue with/without white sleeve against each other. Same for yellow/yellow-white-sleeved.
At least from my present impression of this thing, this would mean pinhead's scheme and it should work with both unstriped connected to ground then. :roll:
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum


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