Will, Jhodge, 007, and all engine guys!!!

I have a theory as to why newer engines have less mpg as opposed to, say, one with 20,000 miles or so. Not to go into the "breaking in" of the engine, but in the last year I have been tracking spark plug gaps at a 30,000 mile change, or there about. Seems the majority of the people that change the plugs at this interval have spark plug gaps of .040 to .041. Min. spec. is .039, with .043 being a max. In my experiance, plug gaps grow about .003 to .005 in 30,000 miles (copper/nickel plugs). My theory is that the plugs from the factory are gapped at .035 or so. This will make the spark more reliable, but it will be a small spark, causeing a rich condition of the engine, as the burn will be largly incomplete. Not enough to trip a code, but enough to affect mpg. As the miles are put on and the gap grows to .040, the spark will be larger, creating a more propperly ignited air/fuel charge. Im thinking this could also be one of the reasons that the engine, in some cases, wont light on the first starting attempt.

What say you?

 

finally doing something constructive with your free time i see

 

^

And the theory seems pretty sound to me. The same should hold true when installing an MSD ignition in the same vehicle. More thorough fuel burn should definitely improve power and economy.

But then I could just be talking out of my ass. Subscribed to follow the discussion.

 

While, I think you have a good point, I'm going with the break in period. Once the engine has a chance to loosen up it moves easier.

 

Not on a new one. But I dont belive they only grow .001 to .002" in 30,000 miles. No way.

 

Yes, I know....BUT, the engines are mostly broken in at the factory. Not saying they dont "Loosen up", but I have been wondering why there have been some starting issues (slow start, no start, etc.), but after some 10,000 miles, there isnt. Slow starting, and periodic No start isnt going to be caused by a "tight" engine.

 

Yeah, well........Im tired.

an MSD ignition wont work on the Tacomas. They only work on central ignition systems (as far as I know) Plus, the stock system puts out more voltage than the MSD's.

 

Let me know the miles, and gap of the plugs. I have about 15 vehicles that I have checked on, and they all have had spark plugs gapped at about .040 to .041, and their milage has been between 27,000 and 34,000 miles. Im betting yours are gonna be the same.

 

It was more of a theoretical idea than a direct application. Since the coil-on-plug design came out I haven't heard much from the MSD crowd. Good to know that there's a reason for it.

 

glad to know someone thinks i know what the hell is going on...lol. if i can find my gap chip i'll try to pull one from mine tomorrow and let ya know.

 

Thanks.

 

yall should check luni's new ones too...with the mileage...see where he's at

 

yeah...i've got about 7k miles on mine. his is a lil fresher.

 

AWSOME! Thats what I was thinking. A .035 gap is gonna give a weak spark. Thanks Will.

 

I think that would cause more harm than good.