New TT will have 10:1 compression. Massive HP mod gains gonna be limited?
MBWorld Fanatic!
Joined: May 2009
Posts: 1,071
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From: NoVa
2004 S55 (SOLD, miss it every day), 2009 GL550
Most DI engines suffer from excessive carbon buld up due to PVC and blowby gasses hitting the dry hot valves or lower IM. Because in a traditional injected motor injectors "Wash down" the back of the valves and intake ports you don't usually get that in a non DI engine.
There are different strategies manufactures employ to keep it in check. DI engines make more power because they run more compression and have more oxygen per combustion cycle( due to running much leaner than traditional stoich ratio). The injectors produce more swirl and combine with the airflow to make a more heterogeneous mixtrure. This higher compression and "leaner" burn mean the engines run alot hotter than non DI. That is the first way they deal with carbon buildup. Extra heat to cook off alot of the blowby gases. They also add complex PCV Catch cans( or cyclone filters) to prevent much of the gunk from getting injested. Lastly they also add supplementary injectors in the IM to provide the "wash down" that I mentioned earlier. The new engine will employ this in some fashion I am sure.
There are different strategies manufactures employ to keep it in check. DI engines make more power because they run more compression and have more oxygen per combustion cycle( due to running much leaner than traditional stoich ratio). The injectors produce more swirl and combine with the airflow to make a more heterogeneous mixtrure. This higher compression and "leaner" burn mean the engines run alot hotter than non DI. That is the first way they deal with carbon buildup. Extra heat to cook off alot of the blowby gases. They also add complex PCV Catch cans( or cyclone filters) to prevent much of the gunk from getting injested. Lastly they also add supplementary injectors in the IM to provide the "wash down" that I mentioned earlier. The new engine will employ this in some fashion I am sure.
what he said
