Trivia question

[Potty_Pants]

Hi guys,

DI Carbon deposits...

All DI engines are different some worse then others, jury is still out on Hyundai.

I would assume its better to have a lower reving engine generate deposits then a higher reving engine (basically 1500 rpm cruise vs 2800 rpm) ? Note Fuel injection doesnt apply here different animal.

I would assume a larger engine would have more depoisits (on the average)

I would assume a larger engine reving lower would last longer then a higher reving V6 with a smaller intake before walnut blasting was required ?

I would also assume a higher compression and/or turbo would exasorbate the carbon build up.

if you've stayed at a holiday inn express please mention that in your reply.

thanks

ppp

 

[Gunkk]

I know we have an engine expert or two around that will likely correct this (feel free!), but I'll toss in my two cents...

DI engine deposits are simply soot. Soot is a result of incomplete combustion of fuel. Injector timing and spray flow characteristics, air/fuel mix characteristics inside the cylinder, and spark timing all contribute dynamically to the formation of soot.

Higher detergent fuels may help retard this, but if the engine is susceptible to soot formation, then it will happen.

Deposits inside the engine, namely on valve components, are a combination of:

1. Combustion Products (result of a chemical reaction)
2. Intake air flow characteristics that allow deposits to collect on surfaces (eddy currents). EGR that allows excess particulate recirculation.
3. Cylinder internal flow properties and dynamic combustion behavior.
4. Surface stiction/adhesion behavior
5. Lack of deposit cleaning process

#1 is inevitable
#2 is related to blowback from the cylinder on the intake valves during intake cycle, and/or deposits from exhaust gas recirculation.
#3 is a function of engine design
#4 is inevitable
#4 valve wash is not present in DI engines. In non-DI cars, the injectors are outside the cylinder and "wash" the valves to mitigate adhesion and provide a cleaning process.

Higher detergent fuels designed to "wash valves" in port-injected and throttle-body injected engines won't work, as there is no "valve wash" process in a DI engine.

So to answer PPP's question: Size doesn't matter. How you use it does matter

Interesting article on the Theta:
http://www.hyundai-blog.com/how-hyundais-theta-engine-works

See also:
http://lmgtfy.com/?q=deposits+in+direct+injection+engines

http://www.autoobserver.com/2011/06/direct-injection-fouls-some-early-adopters.html

http://www.google.com/url?sa=t&rct=...koCABw&usg=AFQjCNFt7IiffnRieRK2El7FN8nov1EzRQ