Calculating available injector PW.

[Six_Shooter]

I've been try to get rid of some detonation that is occurring once I'm in boost, usually over 7 PSIG, and I'm trying to determine if I may be out of injector.

Doing some looking around on TGO, the common table is this:

RPM......PW ms
1,000....60 ms
2,000....30 ms
3,000....20 ms
4,000....15 ms
5,000....12 ms
6,000....10 ms

I can't seem to get the same results with the basic formulas that are presented, being (RPM/2)/60 I think there is another part that deals with how many injection events per revolution, but it hasn't been made clear in what I've looked up.

FWIW, according to the reported PW in the datastream, it seems that I'm getting close to or out of injector at about 5500 RPM, and just close above and below that.

[RobertISaar]

well, at 6000RPM, you have 10mS per revolution. if you run the injectors as double-fire, then beyond 10mS at 6000 is doing nothing. single-fire is 20mS.

engine revolution time in mS = (60 / RPM) X 1000.

1 injection event per 2 revs(single fire/SFI) maximum injector ontime = ((60 / RPM) X 1000) X 2
2 injection events per 2 revs(double fire) maximum injector ontime = (60 / RPM) X 1000
3 injection events per 2 revs(???? fire) maximum injector ontime = (60 / RPM) X 1000 X (2/3)
4 injection events per 2 revs(???? fire) maximum injector ontime = (60 / RPM) X 1000 X (1/2)

you should be able to make an injector duty cycle value as an item using BPW and RPM assuming your calibration doesn't switch between firing modes.

[EagleMark]

http://www.thirdgen.org/techboard/di...pping-why.html

HTH!

EDIT: How come your numbers are double what I have been useing?

http://www.thirdgen.org/techboard/po...07-post68.html

[RobertISaar]

not sure what kind of application BMmonteSS calculated those for, but 6000RPM for example:

60 sec / 6000 RPM = .01 seconds per revolution
.01 sec X 1000 = 10 mSec

since we're dealing with 4 cycle engines, the engine revolves twice for a full cycle, so at 6000RPM, there are 20mSec in which to inject fuel before the injector is open at all times.

[lightning-jr]

http://www.thirdgen.org/techboard/di...pping-why.html

HTH!

EDIT: How come your numbers are double what I have been useing?

http://www.thirdgen.org/techboard/po...07-post68.html

I made one for TBI 35-6800, tis in word. If those numbers are 100% that might be your deal 'cause I show 6ms @ 5k 100%
My chart also shows 80 & 85%.

[EagleMark]

not sure what kind of application BMmonteSS calculated those for, but 6000RPM for example:

60 sec / 6000 RPM = .01 seconds per revolution
.01 sec X 1000 = 10 mSec

But it takes 2 revolutions (720 degrees not 360) to make a full cycle. So divide 10 mSec by 2 = 5 mSec

If you have BPW in data stream the conversion is (X * 0.01526 + 0.396) with .396 being the injector bias in the bin. Then make a new value in ADX for Injector Duty Cycle with linked output from X = BPW and Y = Engine RPM
( X * Y / 60000 * 100 )

This works on V8 TBI, not sure if changes are needed for inline 6 and MPFI?

[RobertISaar]

But it takes 2 revolutions (720 degrees not 360) to make a full cycle. So divide 10 mSec by 2 = 5 mSec

why divide by 2? the engine rotates twice per 4 stroke cycle, so 10mSec for rev 1 and another 10mSec for rev 2 for a total of 20mSec in which to inject for the next intake event at 6000RPM.