Shell Gas and Pinging

[rslifkin]

Steve - Your SRT8 has knock sensors, so it will pull timing if 87 is put in, and not ping. It will lose some power, and maybe a bit of mpg.

My Jeep requires 91, according to the manual. With fairly aggressive timing and no knock sensor, it's pretty sensitive to fuel quality. If I get a tank of cheaper, off-brand gas from a lower traffic station, and it sits in the Jeep for a while, it'll ping a little around 1/2 throttle after a few weeks, necessitating a top-off to keep it happy.

 

[ChuckBerry]

Originally Posted By: SteveSRT8
This makes pinging, if it's genuine pre-ignition knocking, a VERY bad thing!


To be exact, ping/knock and pre-ignition are not the same thing. As I understand it, ping/knock is detonation of isolated pockets of fuel/air mixture due to over compression and/or excessive heat. Pre-ignition is having the fuel/air mixture detonate prior to the spark firing by some heat source other than the spark, like a hot spark plug, some very hot carbon deposit on the piston head, etc.

 

[kr_bitog]

Originally Posted By: deven
I have noticed something interesting in using Shell Gasoline. My two cars (Acura TL and MB E350) when fed Shell 93 octane with V-Power, both cars get a slight ping especially at start-up. For a bit now, I have been going back and forth with the V-Power and Mobil 93 octane. Whenever I fill up with Mobil Gas, there is no pinging in either cars!

My question is if anybody here has had similar experience as mine or I am just going senile(don't answer that..lol)

Thanks,
Deven


I find certain car is sensitive with Shell, my guess is due to the burning speed after ignited (not the octane capability withstand heat before ignited) . The V-Power is less problematic compared with other grade, but on my car the ping get cured by gapping the plug on the lower side of the spec. Somehow I find ExxonMobil is the smoothest even though sometimes I still put Vpower when is on sale.

 

[TurboFreak]

Hi Guys,
A search lead me to this post so I had to register and add to the subject. I had started a thread discussing this same issue on the turbo forums. My car is a 2.2 turbo Dodge from the late 80s. I have tuned performance cars for the last 8 years. Here in the Dallas area there are very few choices for fuel. There is QuickTrip convenience stores, RaceTrac, 7-11 convenience store (which carries Citgo), and a freaking Shell on every corner of my 30 mile drive to work. Citgo is the "only" fuel I buy that I can actually get any decent power tune from while pushing 22 psi boost easily all day long with no knock, so I fill up there religiously.
When I "have" to get fuel from Shell (if only thing around) I get knock at partial and full throttle right when I get back on the highway resulting in having to detune ignition timing by at least 3-5 degrees in all load areas with the addition of raising fuel from 11.4:1 A/F ratio to 10.5:1 or richer to get rid of it. It is very aggravating to lose 10-15 HP (or more) just on a tank of gas from somewhere else. From both stations 93 octane is used. While researching the websites of Citgo and Shell you will find 1 main difference between the two, and funny marketing statements from Shell. Citgo basically says "Where from Houston, and we provide fuel", Shell on the other hand boasts page after page about providing fuels for Formula 1 and how their fuels exceed the amount of detergents in the fuels over federal requirements. It is hilarious to me how Shell's marketing spits out the fact they provide racing fuel to Formula 1 while speaking of their daily fuels being so clean for the environment and how clean it keeps the engine. I tear down and rebuild performance engines and I'll say, I have never come across an engine that was as clean as they state that used their gas on a daily basis. An engine's mechanical life will be longer using fuels which resists detonation as opposed to using fuels that keep your valves clean (per marketing) but can not resist detonation from occurring.
This post is not for everyone, but it is for the folks who enjoy the performance factor of their cars. If you noticed pinging or knocking from a specific fuel, it would be your best bet not to use it. In my car, fuels from Shell have granted better gas mileage by about 2 MPG, but that fact may be heavily swayed by the fact I can't drive my car "normally" with the knock present and HP reduced.

Chris Robertson
TurboFreak.com