in tunerpro or winALDL, what should i be looking at to know if my injectors are getting maxed? i really would like to know. thanks!

 

Watching the injector duty cycle is one way. If it goes over about 80% then your injectors are basically going static (open all the time). If you're running a WB, you should see it leaning out at the same point in the data logs. Two choices remain at that point - either larger injectors or more fuel pressure. Lack of fuel pressure could be due to too low a setting on your AFPR, too weak (or failing) fuel pump, or a filter clogging up. You can also watch the pulse width in the data logs, but I'm the first to admit I don't know how to tell if those are getting too large (don't know the values to watch for, and the allowable max numbers get smaller as the RPM goes up), but theoretically the injector DC % value should work the same.

Hope this helps.....

 

Dc - Third Generation F-Body Message Boards

 

Good reading!!! Only problem is: If you don't use the duty cycle %, and try to look at the pulse widths, how do you determine what the max PW should be for any given injector at each given RPM? I can do the math to determine the max time available for the injector to be able to pulse twice like our batch systems do at any RPM, But what should be the minimum "off time" to use to determine if you've gone too far?

 

i found this: TBI however! it may give insight.

Quote//:
Static is at 100% or greater. The '747/'8063/'8746 ECMs fire an injector every time a plug fires. There are two injectors. They alternate on plugs firings.

Before I go too much further this is in synchronous mode. Sync mode is sync'd to plug firings. This is the most common mode. I have seen a few cals that are always in async mode, but never an f-body cal.

So for each revolution (V8) there are four plug firings. It takes two revolutions to fire all eight cylinders/plugs. Alternating injectors, that means each injector fires twice on each engine revolution.

At 4,000 RPM (revolutions per minute), divide by 60 for revolutions per second: 4000 / 60 = 66.67 revolutions per second. Invert this value for the time of each revolution (or frequency thereof): 1 / 66.67 = 0.015 seconds. Or, 15 milli-seconds (msec) per revolution.

With each injector firing twice each revolution we need to divide the amount of time in half: 15 msec / 2 = 7.5 msec.

This 7.5 msec is the amount of time an injector has before it is fired again (at 4,000 RPM). The higher the engine speed, the less time there is for an injector to deliver the required amount of fuel.

This is why it is important to keep an eye on the injector PW. Once the PW value exceeds that given amount of time, no more fuel can be added. The darn injector is on ALL of the time.

At this point the only thing that can be done is to increase the delivery of fuel. Bigger injectors and/or higher fuel pressure is required.

As another data point at 6,000 RPM a TBI injector is static once it hits 5.0 msec of on time. For best results TBI injectors shouldn't be open for more then 85% duty cycle. At 6K RPM this is 4.25 msec's.

RBob.

Quote//:

Now that we know how much time is available to inject fuel we need to find out how long we’re asking the ECM to hold open the injectors. The easiest and most accurate way to do this is to just log it !!! So we go back to THIS thread and take a look where Rbob tells us how to get our PW to be broadcasted in the prom ID field. In summary we have to manually go into the bin file and change some things. This is more moderate level changes that won’t make any sense, but it will work. When I say manually I mean MANUALLY. We’ll go into tunerpro and open the tools drop down menu and click on advanced, then hex editor. What your are going to see looks like something out of the Matrix…take a deep breath and don’t get scared, it’s not that bad. What you are seeing is the actual programming that is on the chip, this is what our .xdf file converts into something readable for us to understand. The grandfathers of tuning used to look at this stuff and look for trends to identify timing and fuel tables and then manually edit these values…..be very glad we are where we are today. If you look you’ll see that there are addresses listed to the left and values listed across the page. We’re going to go to the following addresses and change the values to following values. For the address just look at the number D414 = 414, but in the hex editor your going to go to line 410 and then go over 4 places, if you look at the bottom of the screen you’ll see exactly what address your highlighting. I’ve attached screen shots of before and after edited parts.

Change to these values
Addr: Value:
$D414 $00
$D415 $AA
$D416 $00
$D417 $AB

What we have done is told the ECM to look up another value other than the PROM ID and put it in the ALDL stream in its position. The thread listed above also tells how to put your total timing into the ALDL stream, very handy. Now our Prom ID field in winaldl will give us a raw hex value for our PW, we then have to take whatever value is displayed and multiply it by .01526 and add in the injector bias value which can be found under the constants menu. This is where putting your log file in excel comes in handy. You can set it up to do the simple math for you. Ok so now we can do a log and see what our PW is getting up to. To get your PW as a % just divide the time available by the time used. The generally accepted limit is 80-85%. Since Rbob already did the math we know we’re going static. It will be a good learning experience to go head and log what static injectors look like. You’ll see the O2 peg rich/lean and feel the loss in power at whatever point the injectors go static.

So how do we fix this????? It’s pretty simple, we ran out of fuel, since our part throttle fueling is in the ball park and we’re still maxed out the only option is to increase fuel pressure or get larger injectors. So this means that holley is lying through their teeth about the injector size, or your motor has more done to it than just a big TB. (which it does) The procedure is to jack the fuel pressure up and then adjust your BPC until your BLM’s drop back into line. You can also lower your VE numbers as well, since both are used to calculate the actual PW. I would drop your VE 10% across the board to give yourself some more room then adjust your BPC from there. I know we’re not giving the ECM proper numbers now, but we have a big unknown in the system and it’s the injectors. As long as we’re getting the proper amount of fuel it won’t matter. It’s always better not to lie to the ECM, but in this case we have to since we’ve been lied to.

I hope I didn’t loose anyone there, please ask for verification if you don’t understand. Let’s keep it to PM’s and I’ll post up any clarifications I think are necessary. I’m not the best communicator, so please let me know if I’m not making sense.

 

im sorry but in tunerpro i cannot locate anything that says injector duty cycle, there is an egr duty cycle and an injector pulse width. but im not seeing it :\

 

I just run plenty of injector and don't worry about it......

I've never sat down and did all the calcs.
But there are several posts that have some DC info in them.


I think it goes something like this:

You only have so much time to have the injectors open and get them closed again so that they are ready to be opened the next time.
The open/closing time varies by injector design and coil resistance.
But 1.5ms is a ball park value to use on a 730.
So add 1.5ms to your PW value.
Now figure out how much time you have based on your rpm.
As long as your PW + 1.5ms is <= .85 to .90 of this value.
Your ok.
If your approaching .9 or your VE table is at 100. You need to start thinking about more injector.

 

check this out: http://www.users.bigpond.net.au/ben_...ctorsizing.xls

 

It's not a tuneable parameter, it's an ALDL datastream item/reported value.

 

Can somebody verify I'm doing this correctly?

Assume 5500 RPM, 1.5ms on/off time requirement, and an 80% duty cycle.

Does that equate to a maximum injector pulse width of 7.53ms ?

If it does, then I've built a simple little spreadsheet for various RPMs and duty cycles to use as a future reference....

 

i know, im using the datalogger that tunerpro provides.