Start of Injection Delay

[907DAVE]

Just came back here to re-read this thread and I think there is a few posts that are missing.

For an "all out" program would you be better off setting this at a low number across the board?

Like the actual delay at full temp, which I guess will be around or less than 1ms. Of course the program would ONLY be used at full operating temp.Would this add a timing safety net?

[cleatus12r]

Originally Posted by 907dave

Just came back here to re-read this thread and I think there is a few posts that are missing.

For an "all out" program would you be better off setting this at a low number across the board?

Like the actual delay at full temp, which I guess will be around or less than 1ms. Of course the program would ONLY be used at full operating temp.Would this add a timing safety net?

Personally for my own programming I usually only alter this map by a half a millisecond or so at the most....and it's never at the higher ICP levels (high load).

You will see that most of the time in aftermarket tuning, the higher the ICP, the higher the delay is set. There are a couple of reasons for this, the biggest being that the amount of fuel being injected is higher for a higher injection pressure. By programming in an advanced SOI based on load and RPM (basically higher ICP and higher RPM), the burn is hopefully initiated sooner and it keeps the fuel from burning too much past TDC.

The nice thing about the delay map is that it is based on EOT. My programming will leave the stock delay at low temperatures (below about 120F) and at high temperatures (above about 240F). I usually incorporate the same temperature changes in the PW multiplier map too.

If you're worried about any effects due to a time-based SOI map, then it's best to leave the map alone.

[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.