Injector duty cycle - is 100% ok? [Archive] - Mitsubishi Lancer Register Forum

Injector duty cycle - is 100% ok?

01-04-2009, 02:11
Is 100% duty cycle ever acceptable?

If so, why?

If not, why?

01-04-2009, 04:43
After mid 90's the flow pattern of the injector becomes a jet, rather than a nice conical spray. The atomization and burn can be effected.

01-04-2009, 09:01
Does it heat up the injector being held open 100% of the time?

01-04-2009, 09:13
anything electrical being forced to function at 100% would suffer with some heat but nothing to the point thats worrying, thats not your worry, your worry is engine damage, your running at wot and high rpm then you have a fueling issue its not best practice, upgrade them and remap is the answer for safety.

01-04-2009, 09:19
Over about 94% (if you measure IPW/time rather than some other methods that measure IPW/available time which may be less than 100%) on the stock Evo 9 injectors I find you lose fine control of the AFR and have a little step where it goes richer, at this point the injectors are not closing. Theoretically you could overheat them, especially low impedance injectors, although ours don't run the sort of current most low impedance injectors do because of the resistor packs. The stock FQ360 runs 100% IDC.

Personally I've not heard of the spray pattern changing, and not noticed any effect on power or misfires when you cross 94%. I raised the fuel pressure to bring it down, but there was no difference in the tune apart from the injector size to compensate - it wasn't faster or slower.

Jason's point is good, and on the stock ECU if you are at 100% at high revs on the first pull through a gear, the protective lean spool effect won't richen up as you drive the car hard repeatedly through the gears, brake, and do it all again etc.

Personally, I run mine in the 90% to 100% range depending on the fuel I use (even a 10% methanol mixture needs a bit more IDC to get the same lambda, which was my real reason for raising the fuel pressure).

01-04-2009, 11:23
I've got some good pictures somewhere of injectors being tested. The difference at running over the specified max duty was was very noticable in the dispersion pattern. These were not from an Evo, but I would expect the same effect.

01-04-2009, 11:59
You would expect some change in smoothness, tolerable ignition timing, unpredictable AFRs, loss of power or reliability, yet none of us see these features. I also can't see how if the fuel pressure is satisfactory that you would change from a conical distribution to a jet - there is a cap on the end of the injectors like a shower head, not like the old pintle designs. I wonder if your picture was of a pintle injector?

01-04-2009, 12:05
I'll see if I can dig them out, been a while since I last saw them.
I had some low mileage <10000 miles RC injectors cleaned last week, the differential in flow between them was large before cleaning, and the pattern after cleaning was vastly improved. These were fitted to an Evo and run on nothing less the 99 and a little meths.

01-04-2009, 12:07
What was the difference?

I suppose the problem is if we don't want to go over 90% then we won't get the most out of the stock turbo unless we raise the fuel pressure. Most stage 1 people don't want to buy injectors...

01-04-2009, 12:15
One injector was faulty and suspected of causing a failure, but the other 3 had more than a 5% difference between them.

01-04-2009, 12:18
That's when you need that individual cylinder knock sensing John ;) Have you finished it yet... you've had all last night and this morning to sort it out :D

01-04-2009, 12:21
I've been trying to get Dundas charts downloaded, to see if I can get my logger using them.

Here is my commute home last night, more fun than usual, AFR mid 11s, low 11s as lean spool effect reduces, but at 7000 RPM and near enough 1.5 bar the IDC is 96%, and this is with 3.6 bar fuel pressure, and it is not the coldest day of the year. Maybe I could do with some injectors, but if I did I'd just put E85 through them!

01-04-2009, 16:31
John, get some 750 injectors and make the most of the added timing!!!!

01-04-2009, 17:48
What added timing? Noticed no movement in knock threshold with various injectors before on a variety of cars.

You guys are on placebos ;)

02-04-2009, 21:39