Engine Ping and Hypermiling

[2011accent]

My Hyundai Accent only has 41k miles on it. A few weeks ago I noticed what could be pinging when going up hills or accelerating. It is such a slight noise. I think I'm hearing it because while hypermiling I have the windows up, ventilation system totally off and the radio off. I got down to a little more than half a tank and filled up with premium. The rattle like noise seemed to go away until I refilled with just low octane gas.

Anyone have thoughts or experience with this?

[brick]

Yup.

http://www.cleanmpg.com/forums/showthread.php?t=44405

I'm going to treat it as if it's a carbon buildup issue for now. That seems most likely.

[2011accent]

So the research I've done is making me think that hypermiling can foul plugs because hypermiling done right requires that the engine runs too slow for the heat range of the spark plugs that are normally recommended. The only way I will be able to prove this is by pulling and inspecting the plugs. My research has shown that a spark plug has the ability to self-clean, but only when the plug's heat range correctly matches the driving style the plugs are used for.

In times past the auto gurus advocated the use of cold plugs in cars driven at highway speeds and hot plugs in cars driven in the city, or that idle a lot. Since our cars are reaching such high mpg due to driving at slower speeds, and not pushed as hard, it seems logical that our cars might need to run with plugs hotter than which are recommended.

[phoebeisis]

Maybe carbon buildup in the combustion chanber-top of rings from repeatedly squirting fuel into cool combustion chamber and cyl walls??
I don't know-cars are designed for cold starts??
Could the fuel mist be adhering to cool CC and carbonizing instead of burning??
A normal drive would eventually get CC hot for a long time- burn carbon and near carbon off- but hypermilers never give the CC and Cyl walls long periods of continuous heating and burning??

Still just two reports of pinging in hypermilers-not many considering many hundreds of hypermilers on the forum

Charlie

[msirach]

Nope. Hypermiling does NOT foul plugs. Modern ECU's control the engine operation at maximum efficiency at all ranges. Look at the fuel you are using.

[herm]

Probably low quality fuel, try chevron or shell regular and see if it goes away.

Hot weather, trashy gasoline and a slight hill are a recipe for slight pinging.. means your car is tuned at the edge for maximum efficiency... either that or deposits are increasing your compression ratio.

[2011accent]

Originally Posted by herm

Probably low quality fuel, try chevron or shell regular and see if it goes away.

Hot weather, trashy gasoline and a slight hill are a recipe for slight pinging.. means your car is tuned at the edge for maximum efficiency... either that or deposits are increasing your compression ratio.

I don't think it's bad gas because it has happened multiple times with different good brands of gas from stations that sell a lot of fuel.

The car only has 41,000 miles on it. Carbon deposits seem less likely than plug fouling.

[brick]

I know we have different cars, but I pulled my plugs yesterday and they looked great considering that they had over 91,000mi on them. See the thread that I linked for pics. I'd be interested to see what yours look like if they are easy to get at. This is interesting because you and I are wrestling with pretty much the exact same issue on totally different vehicles.

Do you drive a lot of short trips? I never had this issue before, but prior to last year I was cruising roughly 25 miles each way to work at highway speed. Now I do 10 miles each way through traffic and only do 4-5000 highway miles per year.

[herm]

Yeah, 41k miles on a 2011 means a lot of hwy miles.. probably bad plugs like you mention. Perhaps run a couple of bottles of techron thru it.

[herm]

I think the refineries are starting to short us on ethanol.. price is going up.