Adding an intercooler to an old truck?

[openspaceman]

 

However, the system of injection build up and subsequent multiple injections, somewhat irrespective of pressure (altho that is needed - the term is "injection hardness" - particularly in a DI) is designed to maintain that constant pressure, hence greater torque outputs without higher bmep. So no, greater oxygen density isn't designed purely to decrease flame propogation time and a reduced CR will permit this. The idea of higher Inj pressure is merely to reduce droplet size and therefore improve mixing.

 

I think we are discussing at cross purposes, I was only trying to explain to Matty why detonation is only likely to be with an SI engine, so wouldn't affect cramming more air into a CI engine. Yes the higher injection pressure enables smaller droplet size, which increases surface area and rate of combustion. The constant pressure combustion refers to the shape of the Volume-pressure graph of the engine over one cycle..

 

As Brake Mean Effective pressure is directly proportional to torque I suspect you mean higher toque without higher peak pressure, which is what I thought I said, it was definitely Rudolph Diesel's original intent.

 

Re SI having all the oxygen neccessary for a complete burn - not at all; they might have been pushing lean burn for years but probe a SI engine exhaust (vs a CI) and you'll observe considerably higher UHC and even ultrafines. CI PM derives from fuel ash content; C as a survivor from the fuel would be be termed UHC in the vapour phase, not PM phase. This is pre-aftertreatment of course.

 

Again we weren't talking about this but rather how a premixed charge completes combustion at near constant volume before it starts pushing the piston down. My proposition is that as diesel injection gets finer and faster the cycle moves from being a combustion under constant pressure, which was envisaged by Diesel and limiting peak pressures to reduce stress on components, towards the SI concept of combustion in constant volume, because advances in engineering mean high peak pressures can be tolerated and still have long engine life.

[TimberCutterDartmoor]

Constant volume is a crap concept full stop though.

[openspaceman]

Constant volume is a crap concept full stop though.

 

Both constant volume and constant pressure combustion are idealised pressure volume cycles which never exist in practice but are used to demonstrate the principles under which engines operate.

 

I reiterate: my proposition is that as turbocharged diesels are developed with electronically controlled high pressure injectors they move away from the idealised constant air charge per 4 strokes Diesel cycle toward the idealised Otto cycle.

[MattyF]

I think we are discussing at cross purposes, I was only trying to explain to Matty why detonation is only likely to be with an SI engine, so wouldn't affect cramming more air into a CI engine. Yes the higher injection pressure enables smaller droplet size, which increases surface area and rate of combustion. The constant pressure combustion refers to the shape of the Volume-pressure graph of the engine over one cycle..

 

 

 

As Brake Mean Effective pressure is directly proportional to torque I suspect you mean higher toque without higher peak pressure, which is what I thought I said, it was definitely Rudolph Diesel's original intent.

 

 

 

Again we weren't talking about this but rather how a premixed charge completes combustion at near constant volume before it starts pushing the piston down. My proposition is that as diesel injection gets finer and faster the cycle moves from being a combustion under constant pressure, which was envisaged by Diesel and limiting peak pressures to reduce stress on components, towards the SI concept of combustion in constant volume, because advances in engineering mean high peak pressures can be tolerated and still have long engine life.

 

 

And thanks for that should of thought about the Diesel engine!

I've never tuned a diesels but spent a lot of time putting charge coolers and bigger intercoolers on rs's in some hope it would keep temps down and was always considered a good base point for any further tuning.