david85
Full Access Member
I'm not aware of any diesel engines that came with domed pistons. Anywhere.
The confusion here might be coming from the fact that modern, direct-injected diesels have lower static compression than older, Indirect-injected diesels. Someone who comes from a gasser background might interpret this as domed vs non-domed. But that's not how it works.
IDIs usually have 20-22 Compression Ratio
DIs usually have 16-18 Compression Ratio
Dynamic compression between the two is similar, because direct-injected diesels will usually run higher boost pressure, thus pumping more air for the same engine displacement. This makes it much easier to get more power per CID of engine displacement with direct injected diesels compared to older IDIs.
However, neither style uses a domed piston.
Indirect-injection uses a pre-chamber that is built into the head, while direct injected typically has a circular recess (or 'bucket') machined into the crown of the piston.
The prechamber is where the IDI injects its fuel, before the flame propagates down into the cylinder. This is done to allow pre-mixing of fuel and results in a better burn, lower emissions, and less engine noise.
Direct injection doesn't need a pre-chamber because higher injection pressure allows for adequate fuel adomizing and mixing. The drawback is a more expensive fuel injection system, and a faster burn that results in a louder ignition knock. Modern diesels can actually pulse the injectors at high pressure to maintain good fuel mix while still slowing down the ignition event to control noise.
The confusion here might be coming from the fact that modern, direct-injected diesels have lower static compression than older, Indirect-injected diesels. Someone who comes from a gasser background might interpret this as domed vs non-domed. But that's not how it works.
IDIs usually have 20-22 Compression Ratio
DIs usually have 16-18 Compression Ratio
Dynamic compression between the two is similar, because direct-injected diesels will usually run higher boost pressure, thus pumping more air for the same engine displacement. This makes it much easier to get more power per CID of engine displacement with direct injected diesels compared to older IDIs.
However, neither style uses a domed piston.
Indirect-injection uses a pre-chamber that is built into the head, while direct injected typically has a circular recess (or 'bucket') machined into the crown of the piston.
The prechamber is where the IDI injects its fuel, before the flame propagates down into the cylinder. This is done to allow pre-mixing of fuel and results in a better burn, lower emissions, and less engine noise.
Direct injection doesn't need a pre-chamber because higher injection pressure allows for adequate fuel adomizing and mixing. The drawback is a more expensive fuel injection system, and a faster burn that results in a louder ignition knock. Modern diesels can actually pulse the injectors at high pressure to maintain good fuel mix while still slowing down the ignition event to control noise.