V8Astro Captain

iTrader: (1)

I'm working with a 7747 ECM. I edited the bin to display the calc'd airflow where the battery voltage is usually displayed.

Now that I can get a rough idea of what the airflow is at certain RPM vs. MAP conditions, I want to get a grasp of how to properly set the INT delay.

My O2 sensor is located pretty far downstream...maybe 24 inches from the header collector. It is a 3 wire heated O2.

My OEM setup was a 4.3 with the O2 located in the main stem of the Y-pipe. In this location it was even further downstream from the engine.

I'm thinking of using the INT Delay vs. Airflow values from the $A0 code AULP bin. This is what my van had from the factory.

How will I know if it's right?

Grumpy

I moved mine back 6' from stock, notta problemo

Your worring about a non issue, IMO.

V8Astro Captain

iTrader: (1)

6'...wow. Yeah that's ALOT further back than mine

That's good to know. One less thing to worry about...

Out of curiousity, did you move the O2 sensor 6ft down because you had to? Or just to see what would happen?

thanks Grumpy

Grumpy

Back when Beta testing the WB stuff, I had a bunch of extra bungs welded into the exhaust to see what varing levels of exhuast back pressure, and EGTs would have on it. When done with that tried moving the stick one around to see how that effected things. It's where it is, just cause it eases working on the engine just a tad easier.

Also, when I was doing feedback stuff and closed loop things on the ecm bench I built a bunch of phoney feedback devises for being able to run closed loop on the bench. The C3 and P4 ecms are really insenitive to the transportation times from what I've seen.

funstick

if these were sequential obd2 systems there would be an issue. but the obd1 systems dont respond to transport delay becuase there no expected respones other then the voltage swing.. now the ford eec iv bank-bank might care but i dopnt think its that picky.

Grumpy

So you have a hac of an OBDII system file?.
Or just guessing?.

On the OBDI systems why did GM even put it in there?. With the exhaust slugs intially moving at about sonic speeds, I just doubt may folks can really sit down and test for stuff like this. How'd you come across the data to say it doesn't matter?.

HighHopes85

V8-

Depending on how far you want to get into it, about the only insight that I can give is that your O2 is only the final word of the entire system.

A few methods of modeling both CFI and EFI are given in SAE 930856 and although I don't grasp the entire document yet, I am starting to come to the conclusion that when I start tuning transient conditions, it's going to be a little tougher than I thought.

If the INT delay for the '747 is a fix for taking care of the time lag constant (could be worded a bit better I suppose), then the document might be something you want to get ahold of (there are many engineering universities that will have SAE documents...and you can probably just waltz on into the engineering library of a public university). But if the INT delay is for something else, then disregard this post.

Good luck, -85Y

V8Astro Captain

iTrader: (1)

Thanks all.

These SAE documents sound like they could be very interesting. I've read about them in some of the papers in the DIY archive. I might have to go dig some up...

HighHopes...I'm pretty sure that the INT delay vs. Air Flow in the 7747 is used so the ECM doesn't respond to the wrong changes in O2 voltage. Meaning the ECM makes an injector PW change, then it has to wait a minute for that batch of fuel to go thru the engine and pass the O2 sensor. It can then determine whether it made the proper change in injector PW. I think, correct me if I'm wrong, it uses THAT info to calc the O2 error.

HighHopes85

Ahh, I see what you are saying about the INT delay.

The document I mentioned is almost more of a "Why you can't tune transients perfectly" so it goes into a lot of lag times (sensor, injected fuel to the back of the valve, etc). The author brings up some neat stuff, but since it isn't related to the thread, I won't jabber all about it.

Grumpy

Without looking as I recall the delays are usec.
Not msec, usec.

Your talking about levels of magnitude of what the oems worry about to make CAFE numbers.

I got to visit an oem's Emission Lab last week, and the EPAs just has the screws down so tight, that they (the oems) are doing barrel rolls to keep up. The flaw in the EPA is no checks and balances so they just enforce whatever the bright idea of the day is, bad science not withstanding.

And when it comes to Patents, and the SAE stuff it's no longer about being truthful in the patent data, they are patenting the ideas, and general mechanics.

If you want to get a handle on the real data you have to go back to the 30s for it (1930s). With the understanding of the early stuff you can see thru the computer modeling etc etc, and *get* whats going on.

Sorry to stray.....

V8Astro Captain

iTrader: (1)

No no, please stray

You're into all the stuff I wish I had the chance to do...