[Diy_efi] forum and calculating sequential injection time

Jay Rabe jayrabe
Tue May 17 20:39:33 UTC 2011

Thanks for the forum link and the its out there replies.

Im running 5 82lb/hr injectors on a 2.3L engine (its a 5 cylinder turbo.)  I
had guessed at injector timing and couldnt get it to idle smooth at 14.7.
It needed a displayed (new LC-1) 12.8 to not bobble at idle, i was getting
about 7% CO.  Making the injector event happen 50 degrees earlier than my
guess, lowering ign timing 1 degree, and lowering injector pulse i got CO
down to about .2%. Thats a pretty huge difference.  It now idles smooth at
14.7 like this.

  I failed emissions with it running closed loop at 14.7:1.  It was
occasionally lean misfiring while they were testing it, im guessing from
incorrect injector timing not allowing it to run smooth at 14.7:1.

I tuned it at idle with a gunson CO meter.  Not exactly a drive it and log
or watch whats going on type of tool.  Its basically only useful parked.  I
ordered a used May something something CO meter i'm going to break apart and
use as a reference for injector timing.

I'd like to still make a sequential timing calculator for when i tune other
cars, at least to get the inj. timing in the ballpark.  Bruce Bowling sent
me a paper on seq. inj. timing i still need to read and try to get my head
around.  Thats my best lead so far.


On Tue, May 17, 2011 at 2:55 PM, Mike <niche at iinet.net.au> wrote:

>  from what i recall of the issue vs batch and sequential is the difference
> is not that much,
> batch can use smaller injectors, sequential needs injectors with more flow,
> batch seems to work fine on many production cars as half the time the spray
> is against the (hot) closed inlet valve, so some vapourisation takes place,
> timing the sequential might not allow as much time for evaporisation
> (comparitively),
> so the first (and quite important) question arises:-
> Why introduce complexities in respect of sequential when batch seems to
> work fine ?
> regards
> Mike
> At 02:20 AM 5/18/2011, Jay Rabe wrote:
> I have heard people refer to the forum quite a bit but never found anything
> but archives of this email list.  Is that what people are referring to as
> the forums?
> I know theres issues with the mailing list but figured its worth a shot to
> ask about sequential timing.  If anyone cant get through the diy list my
> email is jayrabe at gmail.com
> I am trying to figure out how to calculate sequential injector end time.  I
> have searched for hours and havent found much helpful besides
> http://www.oocities.org/fwarner_au/mc_things/efiithoughts.html which i
> believe was/is someone on here.  I started a topic on this at efi101<http://efi101.com/forum/viewtopic.php?p=45567#45567>but i havent really gotten anywhere there.  I know on the dyno with a 5 gas
> analyzer is the correct way to do it but i dont have the $ for dyno time.  I
> need to get through emissions (adding a cat too for the tailpipe tests)
> My standalone has a visualizer/gui<http://i240.photobucket.com/albums/ff267/rabemotorsports/sequential7A.jpg>which is kinda cool but doesnt help calculate injector timing.  I tuned the
> -60 row with a gunson CO meter in the tailpipe (no cat currently) and got
> the sequential timing close from idle up to 3krpm.
> Im thinking of making an excel based calculator to help figure out
> sequential timing (at least ballpark) but i cant find the calculations
> needed.  the above oocities link is missing intake pressure/vacuum as well
> as injector distance from the valve.  Can anyone on here point me to
> calculations, a book on this, or anything else helpful to figure out
> sequential injection timing?
> Thanks in advance.
> Jay
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