Technical > Automotive > Exxon gas cleans intake valves?

Exxon gas cleans intake valves?

Your thought is incorrect, since the injectors inject into the intake manifolds or the port runner *before* the intake valve, it does indeed pass the valves. Only diesel engines use combustion chamber-injection, gasoline uses port-injection or the fuel would not have a chance to properly mix with the air.

reply to aannoonn
There is or was a group of high performance vehicle folk who apparently put some science behind rating consumer level brands of gasolines. Unfortunately I can't find them right now. I do recall that Exxon was not among the elite chosen. Perhaps that has changed by now.

The "clean your engines" claim is as old as the industry. Not saying it isn't true, just that we have no means outside of a proper lab to determine if their claims are true. Most gasolines (aside from Hess*) start out on the same boat just down the road from the war in the middle east. It's the additizing at the loading racks that is apparently the difference in qualities. Then you get into Summer vs. Winter blends, which RVP is where, which states cut with corn squeezins' and so on and so forth.

*Hess is claimed to be primarily from North Sea Crude, and not from the sand box. North Sea Crude is in my memory, considered among the best quality of crude available. I don't doubt that's true, although they are a bunch of pricks to work for.

reply to aannoonn
Detergent additives are required to keep the engine compliant with smog requirements.
Tier 1 is the marketing program to tout detergent additive packages.

reply to Formeister
Well I knew someone would be a perfectionist and dispute my blanket comment... But, there really aren't "many" yet, and all the applications I have read about in the past have been quite problematic. So, better put, the "vast majority of mainstream-production" cars use port injection...

Maybe someday it will be a good alternative, but they have a long way to go.

Check me if I am wrong, and I think I am...

If you have direct injection, doesn't the fuel pressure/pulse have to be at a higher pressure than cylinder pressure? Otherwise, cylinder pressure would keep the fuel from coming out of the injector, or even back up into the injector.

No. Because the injection happens on the down/intake stroke while the intake valve is open to take in air.

»www.animatedengines.com/

reply to mattmag
So there's one injector per cylinder, located immediately before the intake valve? OK. I always though the injector fed directly into the cylinder, like a spark plug.

reply to aannoonn
This is a little off topic but I just love Shell's claim of a nitrogen additive to clean valves. Air is 78% nitrogen, so just how much nitrogen is necessary for clean valves and how much does Shell add ?

reply to aannoonn

reply to Waterbug
It's good for your tires, too. Makes them go faster. Nitrogen - the miracle element.

I always snicker when see a car with those tell-tale "I'm a fool" green valve stem caps.

reply to mattmag
Since BMW, Ford Ecoboost, GM 2.0 Ecotec, Hyundai, Lexus MazdaSpeed, Mitshubishi & VW use the direct injection systems I wouldn't consider this a rare occurance.

reply to neonhomer
No, you are correct for gasoline DFI systems. They take the ~60 psi FI fuel and pipe it to an auxiliary mechanical pump, usually driven off the camshaft, and in some cases bump it up to 580 psi.

reply to PoloDude
Some DFI systems inject after the intake closes and piston is on the compression stroke, similar to a diesel. These systems use a much higher fuel pressure.

reply to Waterbug

reply to Formeister
DI is an interesting addition to EFI. It does increase power and fuel atomisation -thereby fuel economy and power output - but it does require Top Tier fuels in order to prevent the carbon buildup issue.

The fact that fuel does not spray on the intake valve is irrelevant, it just means that carbon deposits build up in a different area than on the back face of the intake valve. Either situation can cause a poor performance issue or oil consumption (in the case of DI) problems.
--
"from a broken heart to a hole in the sky"

reply to Formeister
DI represents a much smaller percentage of injection designs today than conventional PFI, so it is not commonplace. It is a bit silly to play semantics to most folk's way of thinking.
--
"from a broken heart to a hole in the sky"