Start of Injection Delay

[907DAVE]

I just had another random thought pop into my head.

With large injectors with big nozzles fuel is able to be delivered faster, meaning more fuel in less time, regardless of RPM's and possibly EOT and ICP.

If you were to adjust for this faster delivery rate (less delay) would it be better to use this map to do it, since it is a time based map? Just an "across the board" change to accommodate for the big, fast nozzles.

I am aware this is no where close to the only change needed with large injectors.

What am I missing, its early and I haven't had my coffee yet.

[cleatus12r]

Originally Posted by 907dave

I just had another random thought pop into my head.

With large injectors with big nozzles fuel is able to be delivered faster, meaning more fuel in less time, regardless of RPM's and possibly EOT and ICP.

If you were to adjust for this faster delivery rate (less delay) would it be better to use this map to do it, since it is a time based map? Just an "across the board" change to accommodate for the big, fast nozzles.

I am aware this is no where close to the only change needed with large injectors.

What am I missing, its early and I haven't had my coffee yet.

Sorry I haven't been around to put some input in, Dave. I haven't been in the right frame of mind (divorce stuff).

It certainly isn't a bad idea that you have there. By lowering the values in the SOI Delay map, the PCM will command less calculated SOI advance. However, I don't think that it would be the way that I would do it. (I don't know exactly how yet since I've never tuned for aftermarket injectors though. )

Your actual SOI isn't going to change much, if my thinking is right (and I am starting with a little 7 and Sprite right now). The SOI is still going to have to happen at a somewhat "normal" time but the entire quantity of fuel has to be dragged out over a longer period instead of all before TDC. I think that the Delay should be altered slightly but only to keep the injector from emptying far too early. Did I just contradict myself there?

Bill would know, he's tuned for a lot of aftermarket injectors.


OH BIIIIiiiiillllllll!!

[907DAVE]

Dang man.........sorry to hear that.

I am just trying to wrap my head around all these different maps and how they work with each other so maybe some day I will actually know what I am doing.

Way off topic but what would be the point of increasing the MFD map to over 100 at WOT?

What do these numbers actually represent?






Ohh boy........7 on 7.....that stuff will sneak up on you.......lots of stories started with that drink.

[cleatus12r]

Originally Posted by 907dave

Way off topic but what would be the point of increasing the MFD map to over 100 at WOT? To me, it appears to be an easy way to indirectly increase the injector pulse width above and beyond what is commanded in the multiplier map. For instance, if your max MFD is 100 and it gets you a certain PW at a certain RPM/ICP, then increasing the MFD to 110 or higher will allow the PCM to calculate (using RPM/ICP) what the new, higher pulse width should be. It's a way to get the popping and stuttering that you hear in a lot of sled pulling videos too.

What do these numbers actually represent? The MFD map represents mg/stroke per injection event. It's a direct quantity.


Ohh boy........7 on 7.....that stuff will sneak up on you.......lots of stories started with that drink. You're telling me....I made 6 of them last night and drank them in about a half an hour. I slept good last night. I'd been awake for 31 hours since I couldn't sleep the night before.

Hope this info helps a bit.

[907DAVE]

Originally Posted by cleatus12r

The SOI is still going to have to happen at a somewhat "normal" time but the entire quantity of fuel has to be dragged out over a longer period instead of all before TDC.

I have been thinking about this statement a little and am confused about how this can be done.

The only way that I think this can be accomplished would be by dropping ICP to slow the rate of injection, but then you are delaying actual SOI indirectly, also this seems like a backwards way of doing things and might hurt performance/ economy.

Or am I backwards here.

[cleatus12r]

DID I DO THAT?

Whoa. I guess I need to reread my posts when I type them (or knock of the drinking and thinking at the same time).

Your SOI is going to have to be quite a bit later than normal....not around the same time because the injector is obviously going to get out the desired amount quicker. My bad.

Pay no attention to the man behind the curtain!

[907DAVE]

You are too funny!

Your post seemed to make sense to me, I just didn't understand how I was going to make it happen.

[GTS]

Quote:
Originally Posted by 907dave
Way off topic but what would be the point of increasing the MFD map to over 100 at WOT? To me, it appears to be an easy way to indirectly increase the injector pulse width above and beyond what is commanded in the multiplier map. For instance, if your max MFD is 100 and it gets you a certain PW at a certain RPM/ICP, then increasing the MFD to 110 or higher will allow the PCM to calculate (using RPM/ICP) what the new, higher pulse width should be. It's a way to get the popping and stuttering that you hear in a lot of sled pulling videos too.

What do these numbers actually represent? The MFD map represents mg/stroke per injection event. It's a direct quantity.




OK so this brings up a question or two. So you say the MFD map represents actual MG/Stroke. We all know that that can vary hugely depending on the injector and nozzle. I always assumed being it seems like this is a 0-100 scale that it was more of a percentage scale 100 being max MFD. So what is the max MFD that is recognized? I noticed when running AE on my current tunes I was only hitting a max of about 80 MFD. I was going to start by modifying the MFD to come in to 100 at the max TPP voltage that I’m seeing. But if the scale goes above 100 how far could or should a guy go with it? Or does it really continue to ask for more fuel past 100?

[cleatus12r]

Originally Posted by GTS

OK so this brings up a question or two. So you say the MFD map represents actual MG/Stroke. We all know that that can vary hugely depending on the injector and nozzle. I always assumed being it seems like this is a 0-100 scale that it was more of a percentage scale 100 being max MFD. So what is the max MFD that is recognized? I noticed when running AE on my current tunes I was only hitting a max of about 80 MFD. I was going to start by modifying the MFD to come in to 100 at the max TPP voltage that I’m seeing. But if the scale goes above 100 how far could or should a guy go with it? Or does it really continue to ask for more fuel past 100?

Concerning your part in bold and red:

Look at your low boost fuel map (it may have been renamed something like "fuel limit for boost" in your definition). That map is an actual MFD limiter.

[GTS]

Low boost fuel map is maxed out at 100 across the entire map as well is the same map for altitude. I guess if this map is a "limiter" then that would kind of answer my other questions about 100 being the top of the MFD scale. So that being said It would appear that increasing the MFD on the other maps as mentioned above would not do anything as it's being limited to 100 on this map unless you raised it higher on this map as well. I guess the question still stands though that if you incrase MFD above 100 does the PCM recognize that and will it actually ask for more fuel?