larger injector characteristic

[Cameron_Datto]

Iam looking at buying some injectors around 700cc , so I was wondering what was on offer , One thing that concerns me is the finding a injector that will work at small duty cycles so that the idle is still ok . Came across some good information on Youtube . looks like a Modern peak/ hold pintle stlye injector gives a good spray pattern , But the lucas disc type work good at small duty cycles ,but the spray pattern isnt as good as the pintle style . the Siemems brand injectors seem good value to buy new , What is every one using ?

Here is the links to you tube , its worth a look


http://www.youtube.com/watch?v=NIz5c...eature=related

http://www.youtube.com/watch?v=Vfyno...eature=related

http://www.youtube.com/watch?v=7oTirEZNRw8

As you can see old School injectors spray like a Garden hose

[Cameron_Datto]

One thing i found that made a difference is Battery voltage correction to get stable afrs at idle , not sure if you have a adjustment on your ECU , But i ended up disconnecting the alternator to do the adjustment ,and to add the correct milliseconds as the voltage dropped ,, This gave me a stable AFR`s @ idle when the voltage varried and also helped with starting as the voltage drops when cranking,

[MWP]

^^^ That is a good point, lots of these small but important adjustment maps get forgotten when cars are tuned at dyno workshops.

Unfortunately shitey Microtechs dont have a voltage correction map

[renxun]

aha.... voltage correction map.... reffering to AEM mate?

[Cameron_Datto]

Iam using a Wolf V4 , they have a map called " Battery Voltage Compensation " which you can adjust Ms every 0.2 of a volt ,Untill I started using this compensation Map my AFRs were not stable at idle . AT 12 Volts on the Compensation Map ,iam adding a extra 0.2 Ms with 550cc injectors and this Ms tapers down to 0 Ms compenstion @ 14.6 volts ,Smaller injectors would need more Ms compensation and larger injectors would need less Ms , If you had smaller injectors than went to Larger injectors your voltage compesaton will be to much fuel as the voltage drops ,thats if you didn`t adjust this map . I must admit my voltage dose change a bit at idle due to thermo fans cutting in ect . So on other engines if you can keep the battery voltage @ a more stable voltage This Battery Voltage Compensation isn`t as much of a concern , other than Starting when the voltage drops when cranking and just after start up when the alternator starts charging to recover the current draw from starting , when i did my Dyno Tune , i used a very good $2500 Battery charger to keep the voltage at a Constant 14.4 volts . Then i disconnected the alternator ,as the voltage dropped due to no charge from the alternator . I did my Battery Voltage compensation down to 10.5 volts by keeping the AFRs stable

If you can keep your Battery voltage stable @ idle around 14.4 volts ,you don`t have to worry about the compensation as much ,I guess it all depends how Fine you want your tune , But there is more chance of the voltage varying @ idle than above Idle speed , due the alternator not charging as much at lower RPM, And as the thermo fans cut in ect and drawing a lot of current .

You may not want to go to the extreme i did , but beware of your voltage before adusting your map .

[The Witzl]

Good point Mr Datto.
I did a similar thing, though not to quite the same extend, with my Megasquirt on my 18RGE.
Cant remember the numbers now, but i disconneted the alternator to have the car run at ~12V and adjusted voltage correction to keep idle at same AFR as with alternator connected.

I thought this was good enough, cos in most cases idle voltage would vary from 14.4V down to around 12.5V (when thermos and headlights kick in).

I didnt do it very well though, cos my idle AFRs did vary with headlights and thermofan on... and starting was a bit of a bitch.