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Spark plug gaps.

G

gorman

Hard-core CEG'er
Joined
Jun 29, 2008
Messages
1,919
Hey Guys; i've been having some misfire issues lately. I decided to take my plugs out to see what the state of play was in there. All the plugs were sandy brown and seemed to be fine. In fact, they only have 10k on them and i would have been disapointed to find anything else.

Would running the double plat's you guys have, make a noticable difference to low rev/high load ? What are the strong points of the plugs you are all using ? ...G.
 
from my sig. you might see that my car runs on gasoline or propane.

When running on gasoline i have no problems... but on propane i have low rev misfire. Once the engine gets over 3k it's away.
I have single plats... double are much harder to get here. I was hoping someone could say that double plats have a good range and would be worth the shipping to me.

i don't seem to have any arcing with my wires.

The propane setup copies the gasoline maps and then you can adjust fuel with the software. No matter how much i alter the fuel, i can't tune out the damn cough..... G.
 
The Duratec is really designed for double platinum plugs. I don't know much about running LPG, but I would think that running an alternative fuel demands everything to be up to spec. With gasoline, running single platinum plugs can cause them to wear much faster due to the waste spark ignition system. Maybe using propane causes this to show up even earlier than gasoline?
 
hetfield said:
The Duratec is really designed for double platinum plugs. I don't know much about running LPG,?
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it has its' advantages... mostly it is a very clean burn. The oil comes out almost the same color as it goes in. The oil also doesn't get contaminated by the propane and the exhaust system runs much cleaner. Looking forward to checking out the UIM. Oh and propane is half the cost of gasoline :laugh: :laugh: :laugh:.

hetfield said:
Maybe using propane causes this to show up even earlier than gasoline?
Click to expand...

i hope it's not that much earlier... the plugs have 10 -15k at the most. I may try shipping some doubles over and see .. i have some more mods coming and this problem needs to be sorted out .... G.
 
crewchiefpro said:
Spark plug wires need to be replaced if the plugs are OK. Gap should .030. to .045. Tighter is better if you have plug wire problems.
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can i ask please; when should the gap be 0.030 and when 0.045 ? Every post i've seen on plugs have recommended 0.054. I know you have a lot experience and wondered if you could give a little masterclass in spark plug gapping (what can be gained, what the compromises are with large and small gaps etc)... thanks ....G.
 
You really don't gain anything with a large gap on the plugs - at least not on a dyno. In your case I would run .025 to .030 gap since you are having a misfire issue. Smaller gaps fire much easier. Larger gaps produce more arc but I have not seen that translate into increased power or drivability.

The more fuel you place into the cylinder the more difficult it is to jump the gap. On a propane motor it should fire much easier than gas so that puzzles me. If you are sure the fuel mixture is proper then take the gap down to .025 and try it. If it still misfires then that pretty much rules out the plugs.

There is no master class, just experience with my Turbo Contour and my son's. Plus I have an 1100 horsepower race car that the plugs like no more than .030 gap ( that is using a multiple discharge ignition also so every time the cylinder fires the ignition is holding the arc for a split second longer ).

Ford's latest ( as told to me by a Ford Tech ) is one millimeter gap, no more. One MM is .0393700787 so no more than .040 at the very highest. Will you notice any difference from .054 to .035 or less in a stock Contour, NO. Will the wires last longer, Yes.
 
thanks for that Don.

I've set my plugs to 0.040 and i'm starting from scratch. I just wanted to explore the possibility that gasoline and propane have different ideal spark plug gaps. ..G.
 
FWIW, I'm reading online that LPG has an octane rating of 105. Not sure if that translates to a comparable gasoline of 105 octane or not as far as spark plug gaps though, but you might want to check into it.
 
hey zorrex; i've read similar, maybe it translates into a cleaner burn and higher knock resistance.

i think i need to get a professional tune to get the most power from the engine. i spoke to a taxi driver one time in a gas station.... he said that he had his car de-tuned just after he had it converted because it was too much. I have found out since that the propane (at low rev.s ) has to have a pulse width ratio of 1.3:1 as compared to gasoline. So maybe he had his mixture leaned out for economy and found it was less powerful and that was what he meant. I've had it all the way up to 1.4:1 and i didn't feel i was making too much power !!!! It's all new and the experience gained with this car should serve me well with the next.

are you looking for a cheaper fuel yourself ? you guys are mashing it on maize aren't you ? ..G.
 
looking at that it is obviously for carburetor engines .... so i am assuming that the ignition system is points switched. IIRC the voltages attained by points opposed to solid state switched are much lower ... hence smaller plug gap. Now you've shown me that i might spend an hour or so surfing ... thanks for digging that out ....G.
 
gorman said:
looking at that it is obviously for carburetor engines .... so i am assuming that the ignition system is points switched. IIRC the voltages attained by points opposed to solid state switched are much lower ... hence smaller plug gap. Now you've shown me that i might spend an hour or so surfing ... thanks for digging that out ....G.
Click to expand...

Crap I skipped over that part. I used the browser's search function and looked for everything about the spark plugs! LOL! Anyway, apparently propane requires a higher temperature to ignite. I'm willing to bet that's where your problem lies, although I don't know if a smaller gaps creates a hotter burn. :shrug:
 
well i'm trying to pick up info. where i can.

Been surfing, haven't found anything where someone has hands on experience.... everyone seems to pay for the job to be done.

I knew i would have to learn when i put the kit on... it's just frustrating that i can keep increasing the MPG with tuning but this last little teething problem persists.
It will come right.. it had better 'cos it's holding me up ... literally, lol

i adjusted the plug gaps last night .. went for a short trip ... felt better, saving judgement for when the car has a full gasoline and lpg map stored (fingers crossed) .....G.
 
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