Injector Sizing Calculator

[whittlebeast]

Here is a calculator I put together that includes a correction for RPM that most calculators you find ignore. Most I have seen assume 6000 Max RPM. This gets to be a big deal on high reving motors. The yellow cells are input cells. Red are critical output cells. See what you guys think.

http://www.nbs-stl.com/tuning/InjectorCalc08.xls

Note: If you use 6000 RPM and 0 Injector Dead Time, you will get real close to the numbers posted in the MS manuals.

http://www.msextra.com/doc/pdf/html/MS3 ... .4-69.html

Andy

[racingmini_mtl]

I don't think anyone talks about opening time anymore (at least in the way it was originally done with MS). So the dead time (which needs to be computed from physical testing of the injectors) would be, in your graph, AD - BE. As you mention, AD is the commanded pulse width and BE is the actual fuel delivered at the nominal injector flow rate.

Jean

[whittlebeast]

Fixed

[racingmini_mtl]

I'm sorry but my point was not only about the naming but also about the value you assign to it. AB and EF are meaningless because there is no actual value for either since you can position B anywhere (and E will always end up at the same relative position with respect to B) and the rest of your statements under the graph are valid.

As I said, the dead time is AD - BE with BE being a computed value that doesn't have any real position with respect to the injector commanded pulse width. Another way of looking at this is to say that AD is what the MS is commanding the injector and BE is the fueling you get out of it so the rest of the commanded time is 'wasted' or 'dead'. Also, this is constant over most of the pulse width/duty cycle range or what we call the linear range of the injector (very low pulse widths and very high duty cycles are not linear and should be avoided but if they are used, they need to be characterized).

I understand that I'm not explaining anything that you don't already know. I'm just trying to explain why I think this is important so that this is clearer and hopefully not confusing for those not familiar with all this.

Jean

[whittlebeast]

Jean

I did that sketch about 10 years ago. If you have a better idea of a way to present it, feel free to come up with a sketch and I will replace the one I have in there. I did that when I was trying to get my head around what was happening.

Andy

[racingmini_mtl]

Andy,

The sketch is fine and all the other statements are also fine. The main issue is that the dead time is AD - BE and definitely not AB + EF. The other thing I mention about the BE position is that it is not actually located anywhere specific but I wouldn't know how to show that and I'm not sure it is important as long as you don't mix real injector events with virtual ones. Maybe you could use ABCDE for the real injector events (what you now call ACDFG) and use XY for the effective fuel delivered (instead of BE); this would show that this is not actually a single sequence of event but one sequence and an overlayed computed value (of course, that would also mean you'd need to correct all the statement below to reflect the new sequence).

There has been and continue to be so much misunderstanding about this whole thing that I just want to make sure that this is not another potential contributor to the confusion, even if minor. What you have is quite close and I would not be in a position to do a better job and for some reason I can't extract the picture from the spreadsheet to edit it. If you don't want to change the sequence please do correct the dead time value.

Jean

[Blown88GT]

One of our members (seijirou) has created a Dead Time Calculator for MS2 & MS3.
https://docs.google.com/spreadsheets/d/ ... sp=sharing

Injector flow data for the following Ford (some are Bosch & some are Siemens)
https://performanceparts.ford.com/part/M-9593-LU47

The following injectors are currently available from Ford Racing
M-9593-MU32 Calibration Summary
M-9593-M39 Calibration Summary
M-9593-G302 Calibration Summary
M-9593-LU47 Calibration Summary
M-9593-LU60 Calibration Summary
M-9593-LU80 Calibration Summary
M-9593-LU24A Calibration Summary
M-9593-LU34A Calibration Summary
M-9593-MU52 Calibration Summary

The following injectors are no longer available from Ford Racing but calibrations are provided for DIY tuners.
M-9593-LU24 Calibration Summary *no longer available
M-9593-LU34 Calibration Summary *no longer available
M-9593-E303 Calibration Summary *no longer available
M-9593-A302 Calibration Summary *no longer available
M-9593-B302 Calibration Summary *no longer available
M-9593-C302 Calibration Summary *no longer available
M-9593-F302 Calibration Summary *no longer available
M-9593-AA302 Calibration Summary *no longer available
M-9593-BB302 Calibration Summary *no longer available

[whittlebeast]

I updated the original link to better accommodate boosted cars. Note that the airflow velocity and CFM calcs all assume that the air is before any compressor like a turbo or blower.

See what you think.

Andy