Injection Timing/Flow/duration discussion

[soutthpaw]

I was thinking this weekend and have some questions that should lead to quite an interesting and lengthy thread. My main goal is to get a better understanding of the injection theory applied specifically to the 7.3's. I don't expect Bill or anyone else to cover all the questions in one reply either... Maybe taking one point at a time as we can work through it.
My question is basically this. we know that we can regulate several factors of the compression stroke on the diesel: which I will list below.. add other factors if I miss any. How do changes of each of the parameters affect the HP, torque, and MPG performances of the engine.

• Injection Timing= when during the exhaust/compression stroke do we start putting fuel in the cylinder
• Injection duration= how long do we keep putting fuel in the cylinder during the compression stroke
• Volume= the total amount of fuel we put into the engine controlled by Pressure applied to the injector as well as the duration
• Airflow= How much air and at what pressure we put into the engine... I really wanted to leave this out to focus on the Injection (fuel) side of the equation but just in case its needed for discussion I added it.

Questions

• What effect does each parameter above have from a tuning perspective? Why would changing one over another parameter be advantagous and in what ways.. IE: one paramater works better for towing another for performance and another for MPG
• How changing other non-tune parameters such as Injectors, HPOP etc. can alter the above factors and to what extent.
• Can u add larger injectors and still get and equally good MPG's (say with a Fuel Sipper base tune): I am thinking yes as the injection duration could be shortened to make up for higher flow due to larger volume
• What are the Factory settings for these parameters
• Does any fuel get injected during the combustion stroke or only during compression..

[Jackpine]

Are you asking for the "Colonel's Recipe"? (But, if you get it, it will be "finger lick'in good")!

- Jack

[soutthpaw]

Originally Posted by JackandJanet

Are you asking for the "Colonel's Recipe"? (But, if you get it, it will be "finger lick'in good")!

- Jack

actually I have huge respect for Bill as he basically shares his recipe freely with Minotaur Software... The main reason I went with PHP over DP was that i could pursue my interest for learning more about Diesels and Bill was open to sharing....

I thoroughly enjoy the theory side of it so I figure this was a good way to start some technical discussion and hopefully lots of folks will learn from it.. In reality the % of folks that will actually try their hand at doing their own tuning is very small certainly not a threat to PHP's business. (probably the opposite effect actually) However ,it seems some other Tuners don't see it that way... I think I know the answers to some of the questions I asked so will see if my thinking is correct. I guess you can look at tuning like any other hobby or sport that people are willing to put time and effort into to get better at it.

In the world of modern auto repair, I would say there are very few techs who really understand the inner working of Computer control systems. Having taught high school auto shop in the past and maybe I will again in the future, I have always emphasized that you can't find the problem if you don't know how it works! So my goal is to get that intimate understanding of the inner workings of computer control systems. I also see the Minotaur software as a great teaching tool. the 3D layout being very visual and a good way to illustrate what is happening inside the PCM. (Hence, I would purchase more licenses for the software if I get into teaching again in the future) which will be after both my kids are in school full time.

[88Racing]

Southpaw

Good discusion topics!

Big ol'can of worms.

Lars

[Jackpine]

I THINK you knew I was kidding, I hope. Sometimes, I can sound too serious. (I blame it on my Wife - Janet will say, with a perfectly straight face that something totally hideous is "beautiful", and, because she's much more artistic than me, I'll believe her)! :o

I DO think you've opened a productive discussion topic and I hope I didn't derail it. I absolutely agree with all the points you made, and I just wish I knew more about the subject so I could contribute! But, what I know about diesels, you could put on the point of a pin.

- Jack

[soutthpaw]

yep I knew you were kidding.

[Blowby]

Injection Timing= when during the exhaust/compression stroke do we start putting fuel in the cylinder

When is the right time you ask? Let me ask what type of delivery system are you going to use, I mean in detail, since the delivery of fuel will control the point in time enough fuel enters the chamber to start ignition, the delivery system of fuel and oxygen will control the burn rate (time to complete) and the delivery system of fuel and oxygen will dictate the type of pressure and heat created in the combustion chamber to generate mechanical force on the piston and crank.

[theSLEEPER]

This is the thread I was looking for the MOST out of.

Blowby... Could you simplify your question a little? When you say "fuel delivery", do you mean the injectors? Or what?

[Blowby]

Tip hole dia, P&B ratio, oil modifications, HPO method.

[theSLEEPER]

Ok. I see what you're talking about now...

Meaning, if you were running something like Stg 2's with 80% nozzles, and stock oil, and standard 238 hybrids with 200% nozzles, and stock oil you'd want to open the Stg 2's earlier, since they're gonna take longer to empty? Or will the P&B ratio of the Stg. 2 vs. the Hybrid make the Stg. 2 empty quicker?

I'm sorry, I thought I was on track here until I started taking the ratios into account...

Blowby, who built your injectors?