Thanks for clearing things up, Higgs! --and thanks to the OP for giving me one more thing to mess with

 

The problem with that logic is (assuming I understand correctly), the end of the injection timing will always remain the same. It's the start of the injection that changes. So, as fuel demands rise and the injector pulse widths become longer, the injector fires sooner but always ends at the same point.

 

Like I said, it doesn't matter at higher RPMs. Everything happens in one motion. Bang, it's done. It's not a perfect science. You won't see any difference as RPMs rise.

You will also notice that GenIV ECUs have different tables to control EOIT. RPMs included. GenIII does not. This is due to more powerful processors and smarter, more experienced engineers.....People learn, man!

Remember, our GenIII ECUs are OLD!!
If you're asking me why the engineers decided to code EOIT instead of SOIT, I don't know. I don't need to. I don't have that variable to manipulate, so I don't care about it.

 

Working in the confines of the GenIII PCM, however outdated it may seem, it is what it is. The only way we could consider what you're suggesting would be to base it off of a minimum pulse width or some other fixed point such as an idle fueling pulse width. I realize WOT isn't the concern. But, the problem still exists that the beginning of a pulse will always be changing as it's back calculated to start based off of a fixed point in our PCMs (the end timing tables we are modifying). So unless you identify which point you're suggesting specifically, your idea has us chasing a moving target.

 

Unfortunately, it's not "my idea." lol. Ask Greg Banish. Read the HPT thread....

It's simply how it works. If your injector data is correct, you aren't chasing a moving target, your pw's are already correct. Again, it's not a perfect science. The bottom line is that there are spreadsheets to calculate this, there are guys who have mechanically tested this.

You sound like a creationist arguing with science. What are these dinosaur fossils? Well, god put them there to test our faith. Right.

You're not arguing with me, man. You're arguing with the people who created the system and the ones who alter it for a living.

 

Which factory cam are we talking about, 2000 or earlier, or 2001+?
Sorry if it's a dumb question, I admit I only skimmed thru the hptuners thread.

 

Maybe I missed something here...so I'm going to lay it out nice and easy for you.

You said:
My question to you was - and still is - at what pulse width are you talking about???? If pulse width changes, the start of the injector changes. SEE PIC

This is a very simple illustration of low load/low RPM fueling (not to scale). As fueling demands change, the point at which we "start spraying" (using YOUR words) changes as well. The constant is the point at which the injectors stop spraying, which is why the PCM operates the way it does. I don't need a Banish DVD to tell me that. It's in the HPT thread I read multiple times, in which Banish commented ONCE on something not 100% specific to the debate at hand. His comment was more focused on the injection of fuel against the closed intake valve in factory calibrations. So, I don't even know why his name is being brought up here.

You have an awefully strong opinion for someone who's admitting to not knowing what is going on and why. The reason the variable is not there to manipulate is because it's not needed and ever changing based on fuel demands (as illustrated in the attached pic).

Now, I'm not saying I know for certain 100% of what's going on here either. That's why I'm asking questions....not debating science with creationism. PS - that was a total statement. But, based on what I've read, I don't think it's that hard to put 2 & 2 together...

 

ugh, look man, i just gave you the answer to the question posed. if you want to quote specific words to do i don't know what, go ahead.

please, offer up an alternative, otherwise, i'm not sure what your goal here is. you can spray your fuel whenever you want. i'm not here to fight with you but it wasn't until right now i realized that's all you really want to do.

so go ahead and philosophize, theorize, and talk, talk, talk. i posted what works, what others are doing. if you want to attack the idea or me personally, feel free. i have no time for you outside what i've already provided.

 

Dude, I'm not picking any fights. No one is throwing fisticuffs here. It's called having a debate. People in the scientific community do it all the time. It's how a hypothesis becomes a theory. We're all just trying to sort through the BS. No need to get all offended.

 

I'm not offended and it's not a hypothesis. That's my point.

The sky is blue. No it's not, are you sure, let's discuss it. No.

I am not posting to be involved in a discussion. I read information, apply it, and if it works, it just works. I'm not interested in reinventing any wheels. If you want to get into good discussions, post something deep and worth interpretation and trust me, I will go down the rabbit hole with you. But we are not talking about much here except which way to move EOIT, lol. It's a pretty inconsequential topic with regard to all the important things in life worth discussing. I'm just not going to argue about it or even discuss it really.

Try it out for yourself instead of creating a worthless "debate" on a car forum. Just go try it. Use what works for you. Just because something is new to you doesn't mean it's new to the world.

 

I'm referring to 2001+ but it may apply to all other factory cams that have zero overlap.

 

Isn't it the 98-2000 that have zero overlap?

 

Thanks to this thread I now understand what the values mean and were I was doing wrong. I am going to play with this more when I finish building the new car.

Thanks all.

 

I don't know, and I'm not sure there is a whole lot of variance in the factory injection timing between 98-02.

 

I have been playing with this on a large industrial engine using a different PCM that I can select the fueling to start fueling at the give timing event, in the middle or at the end. Now granted it is a low speed engine compared to what we have in our cars and it is a very constant rpm and loaded engine. What I have come to see is the end of the fueling is the important thing for emissions, and power, but only at low rpm like idle or part throttle cruising. What I see is that the end of fueling needs to take place were the piston is at peak velocity. I think this is causing the fuel to mix best and gives time for the fuel to mix after the injection so that you do not have rich/lean areas of fuel. This also helps tremendusly with idle or controling the engine speed at a spacific target point. As you speed up the engine and apply more load to it the pulsewidth increases and the injection begins earlier as we all know. But at higher rpms, piston speed is much greater and the velocity of the air flow is greater. There is less time for the fuel to drop out and with the greater velocity and turbulance the fuel stays atomized. If you sarted the injection at point X every time (selecting begining of fuel delivery) the injection would grow past the point of peak piston speed (peak velocity) and even to the point were the valve is closed. This makes it were all the fuel does not get into the chamber and sits on the back of the valve until it opens again. This gives too much time for the fuel to drop out and some of it can be robbed back threw the runner to other cylinders. Causing very uneven fuel distribution.

Thats what I have been seeing with our experimental fuel injection engine. Keep in mind this engine is a 6600ci straight 8 and max rpm is 900 (industrial use) and not a 7000rpm LS engine. But I would think the principles are the same.

Again, I have seen it make a huge difference in Emissions, fuel consumption, and rpm stability (which is what we are after, greener you know) but we did not loose power until we had it WAY off or was trying to inject at the start or middle of the valve event. Our best results were with ending the injection at peak piston velocity. I can see how tuning this can help in idle quality, fuel consumption at low rpm, and emissions. But as said before you get to a point in rpm and load were the injector is open for a great deal of time before the valve opens at which point the only way I see playing with this is to have a large enough injector in it to were the injection pulswidth is small like at idle, but then you will flood the engine at idle.

 

Thanks for the good informative post. Hopefully, the naysayer will read this as well. There is a reason manufacturers work with EOIT and not BOIT but since I am not a mechanical engineer I don't know why. But that's the nice thing about today's tuning software. If you know how an engine works and how to read, you can learn to tune. After that, it's all what change to what table has what effect. Easy.

Sort of like using a computer without needing to be a computer science major....lol. Thanks Microsoft. Apple. HPTuners. EFI Live.....etc.

 

Yes, quick check shows that inj timing tables are the same between 2000 and 2001. But pretty sure 2001+ has overlap, since that's how they could eliminate the EGR in 2001.

 

Ok, good to know, but it must not be enough to throw off injection timing (I guess ).

 

Well I did some testing on this tonight with a car I've been tuning. Using the spreadsheet I calculated the degree difference between the stock exhaust valve closing point and the new cam's closing point and divided by 90 and added that value to the tables. The result was that the AFR, which I had dialed in to 14.6-14.7 at low rpms changed to 11.9-12.0. So after retuning the VE table, the part throttle values below about 3000 rpms changed from being upper 80's to 50's and 60's. Thus making a much cleaner VE table. Throttle response improved greatly and there was a definite noticeable increase in torque. Also, it being a 6 speed with 3.08 gears, it had a good bit of cam surge. The injector timing change cured that too. So it appears this is something to be seriously considered when tuning.

 

Alright ******* - #1 I dropped it a long time ago. #2, I agreed with what he was saying and totally understand it. YOU were the one who initially said something about using beginning of injector timing, which is why I was debating your post. Go back and re-read the parts I quoted...there's a reason why I did that.