compression question for possible 6.9 build

[79jasper]

Anything is possible with enough money. Lol

Sent from my SM-T537R4 using Tapatalk

 

[SPR1NK]

Good point there sir
I think something like that would probably be a bit out of my price range

 

[PwrSmoke]

Direct injection means somebody made a new cylinder head (or figured out a way to adapt the old one) and used different pistons with a dished crown. Adapting the old head would not be optimal due to injector targeting. If you adapted the pre chamber area to take an injector that would spray directly into the combustion chamber, it would be way off center and at an angle. Far from ideal with a DI setup, where you want the injector targeted to the center of the dish and the outer edge of the spray cone just inside the outer diameter of the dish.

One thing to bear in mind... the very first IH/Ford IDI 6.9L had a CR of 19.5:1. They had starting problems at that ratio so they bumped it to 20.5. That wasn't enough so they bumped it again to 21.5 and that's where it stayed.

One of my farm tractors has a Neuss (a German branch of IH) D358 DI six. It has a 16:1 CR., or what's left of that after 8400 hours. It's impossible to start without ether below about 3r. I have to plug it in for cold starts because the original etherizer in inop.

 

[SPR1NK]

So is it just because of the way the fuel sprays in that makes them need such high compression to be able to stay nicely?

 

[PwrSmoke]

Yes and no. There is no short way to explain DI vs IDI and I don't have time today for the long way. If you Google "Direct Injection", Indirect Injection" and "Ricardo Comet V" you will get plenty to read. The big difference is that with IDI, the injector sprays first into a small prechamber, where combustion starts and it eventually works it's way down to the piston. The air and fuel is not mixed as well as with DI and the combustion process takes longer and is more sensitive to the fuel type and burn rate. When the fuel is mixed better, it takes less compression to heat it it to the ignition point. IDI is just old tech, that's all. They knew about direct injection but technical limitations in the injection pumps and injectors made IDI the technology what worked best for the time. Plus, back in the old days, an IDI engine was more fuel efficient than a DI... for a lot of reasons I don't have time to go into. Anyway, get to Googling!

 

[icanfixall]

The idi engine is a compression ignition engine. That means the diesel is fired off by compression and the heat developed from compressing that air. As we know when we compress air it heats up. Diesel needs about 940 degrees to ignite. You have at least that temp in the cylinder to fire off the diesel.. Ever wonder why a fast cranking engine fires quicker than a slow cranking engine. Now think about hand cranking our idi if you could. You just can't crank it fast enough to develope any heat in the compressed air in the cylinders. Now try a towed or push start in second gear. That engine is really cranking over so it fires quickly. Now think about your battery level going down and you still try to crank it over. Your engine is cranking slower and slower but you continue cranking in hopes it will fire. Well your doing bad things to the started and do you really think one more crank revolution is going to make enough heat to fire the fuel. Might but usually it wont. Now you have dead batteries and a fried starter. Yeah.. You won that one... So remember to have a fast cranking engine to cause enough heat to fire the diesel. Thats a happy id engine.

 

[Dsl_Dog_Treat]

The old flatlander 6.9 was in the low 17's and started just fine.

 

[SPR1NK]

Thanks for all the good info, I tried looking up Ricardo comet V but all I could really find was info about the guy, maybe I didn't look hard enough, but that's all I found

What's the flatlander 6.9?

 

[Dsl_Dog_Treat]

Flatlander was a user here on OB that had a decompressed compound turbo'ed 6.9.
A little searching will get you to his threads.

 

[OLDBULL8]

Beside all the other crap mentioned doing, you should change the damper pulley and flywheel for a added turbo engine or you'll be out of crank balance. Many have added a turbo without doing that, but how long the engine will last is any ones guess. Search here for the different damper pulley configurations.

 

[icanfixall]

Flatlander was a user here on OB that had a decompressed compound turbo'ed 6.9.
A little searching will get you to his threads.

I remember Barney. As I recall you got his 6.9 engine too. What happened to barney and his 6.9??? Members want to know.. We need pics too...

 

[SPR1NK]

This may be a dumb question, but what's a damper pulley?
What would better as far as fly wheel goes? I have a solid flywheel in my truck right now

 

[OLDBULL8]

Damper pulley is on the front of the engine pressed onto the crank shaft. The flywheel is on the rear bolted to the crank shaft, it depends on which transmission you have, auto or manual, as to which flywheel you use, and they are balanced to an N/A or turbo.

 

[SPR1NK]

Oh, the harmonic balancer? I've never heard it called a damper pulley
I have a solid flywheel and zf5 transmission(wish it was a 6 instead tho)
So I would need a flywheel that is balanced specifically for a turbod engine then

 

[Dsl_Dog_Treat]

I remember Barney. As I recall you got his 6.9 engine too. What happened to barney and his 6.9??? Members want to know.. We need pics too...

Yep I ended up with it a year after I helped Barney castrate TDT and turn it back to a near stock condition and the truck sat for a year unfinished until it arrived at the Dog Catcher Garage and then brought back to life for some one else to enjoy.
That engine died way before it's time due to a piston cooling jet that was misaligned and smoked a wrist pin and taking out the piston. That engine now resides in another partof the country again.