pre-cups note
- Thread starter sootman73
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WrickM
Full Access Member
I am curious, not near enough to try it myself mind you, to know how our engines would perform without pre-chambers. I can't see why it wouldn't work. i mean it igh run like crap and be really inefficient, but it should run. Put in the moose misters and now you have a lower compression DI motor ready for a big turbo lol
gatorman21218
Registered User
But what is a pre-cups function? It swirls the fuel and mixes it with air before going into the cylinder right? I agree with Rick in that the boys at Navistar designed it a certain way and to mess with it might make it run like a chevy (that is to say, run poorly). Who knows though it might just be the ticket yall idi drag racing project guys are looking for.
sootman73
Registered User
gatorman the precups are where the combustion actually begins to take place. you have the injector and glow plug in the pre-cup. the glow plug can't heat up the entire cylinder so it only heats up the precup. then once the precup is warmed up the fuel is shot in and ignites. the flame travels out of the cup and then into the rest of the cylinder.
sootman73
Registered User
i dont think you could just take them out because they extend outside of the cylinder diameter and i think there is a water jacket around them? i dont know that last part but there is on the chevy head so there must be a need for cooling there?
WrickM
Full Access Member
Exactly. that's why for a race engine it might be advantageous to do away with them. It might also make the engine entirely unusable too, but why be a glass is half empty kinda person?
gatorman21218
Registered User
Haha Yeah but if you do away with the prechamber wont it have to be direct injected? what then separates it from a 7.3PSD besides the electronics?
WrickM
Full Access Member
ok ok mr glass is half empty. if you can't remove the whole chamber you can machine out the floor of the cup giving direct access to the cylinder. Even machining part of the cup away to deflect the fuel into the cylinder might work.
sootman73
Registered User
well anything is possible but i think for the most part we are looking for a streetable truck and i think that would make the starting awefully hard in colder climates.
i dont think the precups is a big concern. AFAIK Heath Diesel isn't touching or modifying the precups....
WrickM
Full Access Member
i mean it's not like DI was new in the PSD's. older engines were DI they are just louder and less efficient. with a good atomizing injector like the mosse misters and maybe a diflected path into the cylinder to create a big cloud of diesel i think it could work. maybe (likely) not well, and it would definitely need some help cold starting but it is doable. i think.
gatorman21218
Registered User
Help me out here guys I understand the basics of how engines in general work, but when it comes to design and theory I fall short.
So what is the goal of messing with the prechambers? To get more raw fuel into the cylinder so that when ignited it creates more pressure on the piston then in the pre-chamber?
So what is the goal of messing with the prechambers? To get more raw fuel into the cylinder so that when ignited it creates more pressure on the piston then in the pre-chamber?
gatorman21218
Registered User
Detroits were DI IIRC.
What if we made an IDI a two stroke? It would take a hell of a lot of machining though
WrickM
Full Access Member
ok gator i am being a little silly here. What i am talking about is mostly to decrease compression for big race engines so that they can increase the compression in a more power friendly way. i.e. adding more boost from a turbo charger. Also a well mae DI engine (which is not really what we are talking about here lol) is more efficient than an IDI. while the cup ensures that ignition happens in a regular and predictable manner it also slows the combustion process (bad for trying higher rpms) and can make it difficult for the engine to burn the entire fuel charge.
gatorman21218
Registered User
So what about a bigger cup? that would decrees the CR. Is the block/head machinable to allow that?
Not so much related to the pre-cup discussion, but I found this comment on that page interesting....
You really don’t want to use a truck engine for a marine application. The truck engine is designed to be a vehicle engine. A vehicle engine is operated at varying throttle/rpm for city/highway use and a marine engine is operated mostly at a wide open throttle/rpm. The difference is in the pistons. The truck engine has 21:1 pistons and higher compression than a marine engine which has 18:1 pistons. If you convert a truck engine to a marine application you won’t get the horsepower you think you’ll have and you’ll have a problem keeping the engine running cool enough.
We’ve received quiet a few calls from people who have marinized truck engines and have serious overheating problems. I hope you find this information useful.
You really don’t want to use a truck engine for a marine application. The truck engine is designed to be a vehicle engine. A vehicle engine is operated at varying throttle/rpm for city/highway use and a marine engine is operated mostly at a wide open throttle/rpm. The difference is in the pistons. The truck engine has 21:1 pistons and higher compression than a marine engine which has 18:1 pistons. If you convert a truck engine to a marine application you won’t get the horsepower you think you’ll have and you’ll have a problem keeping the engine running cool enough.
We’ve received quiet a few calls from people who have marinized truck engines and have serious overheating problems. I hope you find this information useful.
