Engine technology thread.

[mrtodd]

Originally Posted by Dimman

The squish area is basically used to 'push' the charge towards the plug as the piston approaches tdc, right?

As far as I understand it, yes.

[mrtodd]

Originally Posted by serialk11r

Thanks for the response!
So I take it high rev direct injected engines are a challenge to build because of the compromise between flow and combustion efficiency. Hmm.

Supposedly this is where the D-4S system really shines. The idea behind using 2 injectors per cylinder is to create excellent fuel dispersion without the requirement of intake porting that promotes charge motion. That being said, the intake porting should be shunted towards high flow, as opposed to high tumble.

I was really sad when we found out the FA20 was not going to have any sort of variable lift control for the cams, but the D-4S system is definitely a gem in and of itself and it makes me excited all over again. Even so, imagine how amazing this engine would be with VVTL-i tacked on in addition to everything else...

[arghx7]

Originally Posted by Dimman

The squish area is basically used to 'push' the charge towards the plug as the piston approaches tdc, right?

It depends how the combustion system is set up... I've got some diagrams I can dig up for a few well-known engines if anyone is interested. You could talk about the squish zones on a pentroof DOHC head port injected engine. They usually push concentrated pockets toward the outside edge of the combustion chamber and piston. So that's not really toward the plug. On a wankel rotary engine, there are strong squish flows in the trailing portion of the combustion chamber.

I haven't seen much published stuff on squish zones in GDI engines. Maybe there isn't a whole of squish flow, or maybe it's not that important compared to the tumble and swirl flows.

[mrtodd]

Originally Posted by arghx7

I've got some diagrams I can dig up for a few well-known engines if anyone is interested.

Definitely interested!

[Dimman]

With the DI systems and charge motion, we are basically also less dependent on intake velocity because we are adding kinetic energy from the high pressure pump too, correct?

What are some of the pressures and velocities of DI fuel spray?

[arghx7]

Well as far as squish zones go, below are squish zones on some well-known port injected engines from tdifferent angles. Here's the taper squish zones on a 1ZZ engine:



Here are squish zones on a 2JZ:




Here are squish zones on a Subaru EJ255 boxer engine:



and here is the squish zone (which is very knock prone) on a wankel rotary engine:



If you have a different combustion chamber shape (wedge for example, on a GM pushrod V8) then the squish flows will be different. I don't know too many specific details about squish flows on GDI engines.

Originally Posted by Dimman

With the DI systems and charge motion, we are basically also less dependent on intake velocity because we are adding kinetic energy from the high pressure pump too, correct?

What are some of the pressures and velocities of DI fuel spray?

Lots of time and money are spent to answer those questions. These things are figured out during the development of combustion systems often by guys who have a PhD. The nominal high pressure fuel system pressure varies with the injection system and load, where higher load has higher fuel pressures. They typically vary between 120-200 bar, so do the math. There are fuel pressure specs in the 2GR paper in the sticky. Generally speaking you use higher pressure under heavier loads for better atomization and hopefully knock resistance, while at lower loads you want lower fuel pressure to reduce the amount of energy used by the high pressure fuel pump.

The spray does induce additional kinetic energy into the system. Expensive computer models and optical engines (transparent single-cylinder with high speed photography) are used to study these effects. Maybe I've posted something like this before, but here are some visualizations of spray patterns based on fuel pressure and start of injection timing on a prototype flex fuel Ecoboost engine.

[Homemade WRX]

Originally Posted by serialk11r

Homemade WRX do you have offset/rod specs yet, or if you're not allowed to say, when will you be?

As usual, I'm tight lipped on prototype stuff. Over the years, with shops trying to knock off designs, I find it best to say little.

I still have the larger issue of what's the point of doing the internals for more RPM and air if I can't add fuel, adjust timing, raise redline, etc...still pushing those aspects with certain manufacturers in what free time I don't have

Race season is upon us, so keeping up with 3MI Racing stuff, new parts development and racecar stuff with Turn In Concepts, I don't sleep. I also don't have time for my own cars. See my reduced frequency in posting on here.

I still can't wait to get hands on the engine though. The FA20 has the front burner reserved.

I also just realized they started doing Vendor accounts. Time for me to switch to my 3MI Racing account and see about switching over to vendor status.