Aftermarket plugs

[FLTRI]

Not to  but:
When using other than stock plugs be sure to verify the resistance of the plug you want to use.

Since the ECM reads the after-ignition voltage to determine burn quality (detonation), different expected resistance will provide different values to the ECM. This will affect ignition timing advance and aggression.


The problem with this is the owner/rider/mechanic/tuner has no idea if it is occuring other than to run the bike for a while in all conditions in data mode. Then look at all the data to determine if the ECM was retarding the timing where it should need to.

We stay with the stock plugs for this reason and no other reason as we like NGK, Bosch, Autolite, etc, but they do not list their resistance values.

Sorry if I sound like a broken record but............
Bob

[RainDodger]

Yeah, actually I don't get the aftermarket plug thing either. I would bet that no one can tell the difference between plugs on any given street engine. The stock plugs work just fine. Put them in and be done with it. No error codes. And they're cheap!

[moose]

remember that harley does not make their own plug so are they really aftermarket

[FLTRI]

"remember that harley does not make their own plug so are they really aftermarket"

The mfg of the item is not what aftermarket refers to. In the automotive industry aftermarket refers to parts and assys made to compete directly with the original part or assy.

Aftermarket plugs are absolutely fine IF they have been measured and match HDs specs for resistance.

I have no personal liking for champion plugs but when it comes to how the ECM looks at a given resistor plug's resistance/voltage and makes performance changes based on that feedback, I see no reason to experiment without measurement and testing.

As always, JMHO, Bob

[WVULTRA]

Bob:

Would you have any reservations with running the 6R12 "Gold" vs the standard 6R12?  Not much of a price increase, and thinking they might be a bit more durable?

Thanks for your comments!

[7hogs]

So what is the stock resistance?

[FLTRI]

Bob:

Would you have any reservations with running the 6R12 "Gold" vs the standard 6R12?  Not much of a price increase, and thinking they might be a bit more durable?

Thanks for your comments!

Simply haven't had any problems with the stock plugs' lifespan or reliability so I have reservations to change without return.

[Wingnut]

I agree with Bob. Tried just about every plug out there. Save your time and money. Stock plugs are just fine.

[fxrp]

I don't know if anyone said OEM plugs didn't work well. But an NGK, Autolite, Champion (who I think makes HD plugs), etc work fine and do not affect the ECM/timing. One of the major tuners in this area uses Autolite almost exclusively.

Paul

PS Look here:  http://harleytechtalk.net/htt/index.php?topic=1585.0

[FLTRI]

I don't know if anyone said OEM plugs didn't work well. But an NGK, Autolite, Champion (who I think makes HD plugs), etc work fine and do not affect the ECM/timing. (How did you come to this result?)
One of the major tuners in this area uses Autolite almost exclusively.(Maybe he doesn't know about the Delphi ion-sensing knock retard feature, and figures if the engine runs on other plugs it's probably ok OR he has done proper resistance measurement on the plug he uses to assure the same resistance as the stock plugs that the ECM knock sensing software was written for)

Paul

PS Look here:  http://harleytechtalk.net/htt/index.php?topic=1585.0

Look, use whatever you want but just be aware of possible concequences to your decisions.

"PS Look here:  http://harleytechtalk.net/htt/index.php?topic=1585.0";
With all due respect I don't believe there is a tuner, Delphi EFI specialist, or anyone with ion-sensing technology experience that posted, just some guys who say NGK plugs are good. I do know they are good as well as most other spark plugs, BUT it is the resistance built into these plugs that the Delphi ECM reads and reacts to, so ANY other resistance (voltage return) value will affect ignition timing advance routine. This alteration happens without the rider even knowing it.

[fxrp]

So what is the stock resistance?

I just went to the NGK web site and they do list the resistance. So what is the OEM resistance?

Paul

[ToBeFrank]

it is the resistance built into these plugs that the Delphi ECM reads and reacts to, so ANY other resistance

I have a hard time believing the system doesn't compensate for the plug resistance... i.e. read the voltage (or likely the voltage is already a known value) and current during spark and the plug resistance is calculated from Ohm's law.

(voltage return) value will affect ignition timing advance routine

The voltage is a known value (80V). The current is what is read as the ion signal. As you're indicating, the only way to make sense of that current value is to know the plug resistance. As I said, I doubt they hard code (i.e. assume) the value of the plug resistance.

[ederdelyi]

A little info on ion sensing:

http://www.fs.isy.liu.se/~larer/Projects/main.html

IME/IMO a properly designed and functioning ion sense system used to control detonation/optimum spark timing should be relatively immune to the plugs and wiring unless there is a gross difference from the OEM components. It's more likely that "other" factors are pushing the system to the limits of what it is programmed to deal with ... after all, us HD folks do tend to push these things just a little harder than may be prudent :>)

A resistor plug in a specific heat range from any reputable maker should be "transparent" as far as ion sensing is concerened. Plain vanilla plugs and wires should suffice, high buck stuff need not apply :>)

[V24me]

WVULTRA,
I tried the HD gold plugs and was not happy with them.  I checked the gap, and only changed the plugs.  The exhaust note was different, the idle changed, the motor didn't seem to run as smooth. 

I can't explain it, and I've tried to noodle it and don't get it, but I switched back and forth twice and same thing.

I use autolite with one range cooler, and they seem to work great

WHAT IS THE STOCK RESISTANCE???

[moose]

I'm thinking the HD gold plugs are to put more gold in hd's pocket

jmho

moose

[ederdelyi]

Resistor plugs typically have a 5k DC resistance value (+/- 10%):

http://www.ngkntk.co.uk/working/RunScript.asp?sname=Resistor+Plugs&smenu=TechSpark_2&page=171&submenu=TechSpark&p=ASP\Pg171.asp

I just measured several NGK DCPR7E,  Autolite 4164, and HD 6R12's --- they all measured in the 4.7 to 5.3k range. HOWEVER, IF the plug were to cause problems with the ion sense circuitry and or software it would be due to the plugs AC IMPEDANCE, which you cannot measure with a simple ohm meter. The AC impedance is frequency dependent and would require an impedance bridge to measure. I'd lay odds that they would all likely appear close to identical .... BWTFDIK :>)

EDIT: Fixed link

[Biker]

So are we saying my Champion RA8HC plugs are trashing my engine?     

[ederdelyi]

Not me :>)

[Clintster]

Out of curiousity, I have a set of NGK iridiums in the top of my toolbox.  4.6 resistance, so they should be in range?  Don't ask me why I use Iridium, warm fuzzy feeling.  Believe it or not I think they improve performance, no science to prove that.

[ederdelyi]

If you are asking me ...

Try 'em and see what happens. if the bike runs like it did before and no codes get thrown you are good to go, IMO. And no, I won't ask! :>)

[roadglide65]

I used to get a lot of 1356/1357/1353 codes with the stock plugs and wires.

On a wim I put a set of S/E wires and a set of S/E plugs and it quit throwing codes I still get one every once and awhile but not like i used to, So does any one think I might be screwing up the ECM??

[ederdelyi]

>>So does any one think I might be screwing up the ECM??<<

Throwing codes does not "screw up" the ECM. A no combustion code is the ECM alerting you to the fact that it has detected what it thinks is a misfire. The ion sensing as implemented in the HD version of the Delphi system looks for both misfire and detonation. In the case of a misfire it could be a temporary lean condition or a fouled plug, bad plug wire, etc. If detonation is detected, the ECM will attempt to solve the problem by retarding the spark advance. This can happen with no code being thrown and unless you have some way of monitoring the ECM data you may never know that it is happening. This is what Bob (fltri) is talking about. It's a fairly common problem with high compression EFI HD TC motors and one of the reasons that both the fuel and spark maps must be a part of any good tune.

If something in the ignition system is somewhat out of spec then a code may be thrown that is somewhat of a "red herring". In other words, there may not be a serious problem. This stuff is not 100% bulletproof and may not always play nice with the mods that are commonly done to most HD's and never see a compotent tuner.

[fxrp]

I used to get a lot of 1356/1357/1353 codes with the stock plugs and wires.

On a wim I put a set of S/E wires and a set of S/E plugs and it quit throwing codes I still get one every once and awhile but not like i used to, So does any one think I might be screwing up the ECM??

Try something else. Pull the ECM harness and check the wire at pin #27 (ION Sense). Make sure it is seated well in the plug and making good connection with the ECM pin. I had a couple of 2004s that were throwing the same codes and the wire wasn't fully seated in the harness plug.

Paul

[roadglide65]

>>So does any one think I might be screwing up the ECM??<<

Throwing codes does not "screw up" the ECM. A no combustion code is the ECM alerting you to the fact that it has detected what it thinks is a misfire. The ion sensing as implemented in the HD version of the Delphi system looks for both misfire and detonation. In the case of a misfire it could be a temporary lean condition or a fouled plug, bad plug wire, etc. If detonation is detected, the ECM will attempt to solve the problem by retarding the spark advance. This can happen with no code being thrown and unless you have some way of monitoring the ECM data you may never know that it is happening. This is what Bob (fltri) is talking about. It's a fairly common problem with high compression EFI HD


If something in the ignition system is somewhat out of spec then a code may be thrown that is somewhat of a "red herring". In other words, there may not be a serious problem. This stuff is not 100% bulletproof and may not always play nice with the mods that are commonly done to most HD's and never see a compotent tuner.

Thanks ED just didn't know if the S/E wires might be playing havoc with ECM or not.

<<TC motors and one of the reasons that both the fuel and spark maps must be a part of any good tune.>>

I know that's part of my problem,, one of these days Ill find some one that fit's that bill. 

[roadglide65]

I used to get a lot of 1356/1357/1353 codes with the stock plugs and wires.

On a wim I put a set of S/E wires and a set of S/E plugs and it quit throwing codes I still get one every once and awhile but not like i used to, So does any one think I might be screwing up the ECM??

Try something else. Pull the ECM harness and check the wire at pin #27 (ION Sense). Make sure it is seated well in the plug and making good connection with the ECM pin. I had a couple of 2004s that were throwing the same codes and the wire wasn't fully seated in the harness plug.

Paul

Thanks Paul that is one of the thing's that was check early on.