Why is it so hard to get big power out of IDI compared to DI? (keep reading)

[great white]

Oh, I dunno, this just might be one of the reasons:

Been brushing up on a lot of old and new engineering stuff lately. Some from stuff I learned in university a long time ago, some from new texts I've been accumulating and some is from webinars I've been attending.

The math has been making my head swim, but it sure is clearing up a lot of things at the same time.

This pic was in one of my texts.

All I've done is clear up the numbers a bit for easier reading.

I'm not looking to debate it, just putting the pic out there.

Let the speculation begin.....

 

[3500GMC]

Interesting. I could see where the flame front is very offset on the IDI. Maybe friction from the piston cocking in the bore?- as opposed to the injector firing straight into the 'dish/bullet' (newer high pressure diesels) keeping the parts happier.....

 

[L98TPI]

Sexy pictures

No need for debate the facts are... well, the facts.

I am wondering what sort of fancy engine rig they used to get those photos.

The basic difference IDI to DI is that DI wastes less heat because it makes the flame ball right in the center of the bore. IDI waste a lot of their heat in the swirl chambers in their heads, for other advantages, that were more advantageous in the past.

 

[WarWagon]

Offhand moving the air in and out through the small precup hole and then the swirl effect would cost max power. I know firsthand the fact the precup hole size limits you.

There is new ground to be covered in IDI diesels esp with the forgotten art of Precup design, size, and angle. Camshafts and turbos are also recent areas to break out of the box thinking. Even the injector angle can make a difference.

The emission constraints are the most difficult item to solve anymore.

Cheap low pressure injection and low PSI injectors are still a valid trade off today in the Military Hummer engine. Esp with ability to run different fuels to some extent. Also bad, dirty, etc. fuels.

 

[6.2 turbo]

I don't have a problem making power with small precups. Aparently lots of fuel and boost hides this problem. My motor was probably fighting itself. This also makes sense as why my lower compression motors had better topend power.