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I spoke with a fellow at FIC (Fuel Injector Clinic) and he informed me that Delphi low impedance injectors have an opening time of 1.13ms

That was not what I wanted to hear

hmm very slow.

I thought typical time to open was in neighborhood of 0.05ms

That number can't be right, it may be mininum On time.

There are some good ways to determine your opening time on YOUR engine.. The bench isn't a real realistic test, you don't have the exact same fuel pressure, the exact same voltage (which can be quite different than what you might see on the dash or at the battery, because it goes through relays and many other connections before getting to the injectors)..
The best way I've found for determining injector open time is to put the engine RPM around 3,000rpm, and change the # of squirts. If you have your injector open time right, the AFR will stay the same. Change between 1, 2 and 4 squirts. The reason I say to do it at 3,000rpm is some injectors are too big to idle at 4 squirts, even with MS2's higher resolution, it won't be as accurate a test as you'd have at higher rpm, like say 3grand. Once you can switch back and forth between squirts with a minimum of AFR change, you've probably got your injector open time correct.
Hope that helps.

thanks una. curious though, how can having the wrong opening time hurt performance, drivability, whatever.

If I understand it correctly, that opening time is added to your calculated opening time to deliver total opening time to the injector

Opening time + open time = total time open.

Feel free to correct me.

V

That's correct, that's why the wrong opening time can manifest itself as an AFR change when you change the # of squirts.. You see the error more, or less often, based on which way you change it.
MS2E also has more resolution on the opening time than MS1E did. .01ms instead of .1ms.. Some people found this made a huge difference.
If you use the Enhanced Accell Enrichment feature in MS2E, and want to use the "lag compensation" thing, what it does is change from 2 squirts (or 1) to 4 squirts when you punch the gas. This gets the accell enrichment to each cylinder that much sooner than it would have normally gotten there. but if your openning time is wrong, you'll have a hell of a time tuning it.
Also, having the correct opening time can do wonders for idle control with really large injectors.
All this said.. I've never bothered checking my injector openning time..

AEM calls its response time.

I downloaded AEMPro and I went poking around in their injector wizards and found my injector in there.

Delphi = Rochester = MSD = Precision = Holley

750cc injectors spec out as follows:

10V - 1.22ms
11V - 1.03ms
12V - 0.87ms
13V - 0.74ms
14V - 0.63ms

This is a far cry from what FIC told me......

I'm going to try these values tomorrow and see how it goes..... I cannot get a consistent idle with these injectors to save my life with my opening time @ 1ms

Megasquirt wants the 13V opening time which seems to be 0.74ms and the battery offset works out to be 0.1ms on average.

just out of curiosity, are the RC 750's in there DOHC?

That is a far cry because those are probably the high impedance 750's. &50 is the highest you can go with high Z. next step up is 1000 low z.

On that note, anyone have any idea on opening time for S1 SRT injectors? 1.15 seems to work best for me.

SRT Stage 1's (577cc)

10V - 1.62ms
11V - 1.28ms
12V - 1.0 ms
13V - 0.79ms
14V - 0.61ms
15V - 0.48ms

Damn fast for Hi-Z if you ask me

I entered the new values this morning and after a little table tweaking it is like day and night... I can idle at 14.5 - 14.7 all day long !!!!!!

I am soooo &*^$%^&% happy now

Next step is actually 880 low z.

DJ

I have pretty much retuned my entire sub-boost map with my new opening time and the difference is amazing especially light footing around town.

If anyone has any more time requests, pass em up and I'll see if I can find the numbers.

RC 750cc

Lo-Z

10V - 0.88ms
11V - 0.66ms
12V - 0.48ms
13V - 0.32ms
14V - 0.18ms
15V - 0.05ms

Hi-Z

10V - 1.36ms
11V - 1.12ms
12V - 0.92ms
13V - 0.76ms
14V - 0.63ms
15V - 0.50ms

WOW.. Look at that opening time on the Lo-Z's.. That's some seriously fast reaction times. Those would idle GREAT even at 4squirts, I'd imagine.

1000cc Delphi w/ resistor box? lol

I have it set to 1.25 right now. I tried to change squirts at 3000rpm a while back and the afr changed drasticly. I played w/ the opening time and couldn't get it any better, no matter what I did. Maybe I need to upgrade to the new HiRes w/ the hiccup fix...dunno.

<--MS1

Very good info in here. Thanks.

That's because resistor boxes are a bit of a hack. The injectors don't open and close consistantly because they have an inductor wired in series with them. It screws with the peak current needed to get them open, as well as the flyback clamping the diodes would normally provide. The only thing the resistor does correctly is the current while the injector is actually open.

So for Stage 1s you're using about .79ms and what for your battery offset? .2ms/volt?

Man, I didn't think the .87 or whatever I had for the 1G stock injector worked very well (my hacking around seemed to settle on 1.15ms like Pimp_Dad) but maybe I had other issues. I didn't actually have a chance to really tune them right yet. . . Hopefully soon!

Thanks for the info!

Thad

Many of today High Z injectors match or best opening times of yesterdays (80's, 90's) low Z injectors.

Pintle to ball design evolution made the moving assemblies much lighter and thus open and CLOSE much faster.

By comparison, old turbo dodge Low Z injector Batt offset table:


volts........... 320cc/min turbo dodge (ms)
6 ------------ 1010
7 ------------ 1010
8 ------------ 800
9 ------------ 630
10 ----------- 490
11 ----------- 370
12 ----------- 260
13 ----------- 180
14 ----------- 120
15 ----------- 70
16 ----------- 40

Note these values are with a Peak & Holder driver. Using 10W resistor ballast, the opening times multiply by factor of about 2.5

Those look like flow rates at certain voltages. How does that convert to opening times? I've been looking for the TD low-z injector opening times for awhile now..

That's time offset you need for them to "open" as far as I can understand.

So if you need 50Us, its offset +50

I have to admit, that makes even less sense. I'll stop asking before my head implodes.