Injector duty

[JDR7919]

Ok guys,
I wanted to know if Im over running my injectors causing knock?

This was 1st through 3rd about 15 psi.
Rpms Inj Duty Knock Timing
1281 1% 0 19
2187 2% 0 37
2593 5% 0 36
2687 12% 0 30
3343 22% 0 30
3781 39% 0 25
4062 50% 0 22
4625 65% 0 20
4968 73% 0 19
5281 75% 0 20
5906 85% 0 24
6125 88% 7 20
6812 97% 6 16

4625 45% 0 32
4968 70% 1 18
5687 88% 2 22
5937 93% 2 23
5968 94% 9 21
6531 103% 15 15
6906 104% 14 14

4687 70% 1 18
4875 71% 7 16
5062 81% 7 18
5406 90% 15 16
5625 97% 24 14
5906 100% 24 15
5968 151% 24 12
6000 102% 30 13

 

[crunchymilk]

you're going way past your injectors capacity here. Get som injectors that will let you run under 90% at WOT IMO. Most likely this is causing the knock, so get new injectors/tune ASAP!

 

[JDR7919]

What size should I go with?
I only have maft 2.xx now but i will be getting dsmlink in the next few months.
Thanks

 

[kelvinb]

5968 151% 24 12

wow i thought mine was bad! you need some big injectors, like 650s

 

[99gst_racer]

It is generally recommended to keep your IDC's below 85%.

Your profile says you are running 550's with a 16g.... How much boost are you running?

I don't understand how your IDC's are so high with the setup you have....

 

[GVR4592]

It is generally recommended to keep your IDC's below 85%.

Your profile says you are running 550's with a 16g.... How much boost are you running?

I don't understand how your IDC's are so high with the setup you have....

I was thinking the same thing. Your injector duty is peaking way past the torque peak. Usually it will peak right at the torque peak then fall off a little after that, and our engines dont have peak torque at 6000 rpms, which is where your injectors seem have the highest dc. Do you have cams or sheet metal intake manifold? I've hit 100% duty cycle with 550's and a 16g but I was at 26 psi with pump gas and prety rich a/f.

 

[JDR7919]

Hey guys thanks for the info.
Im running about 16 pounds of boost. Sometimes it will go to like 19 or 20 and fall back down. Im using stock cams and intake manifold.

Could running too rich cause this to happen? I heard if you raise your fuel pressure some it could make your injectors a little bigger. Well, I raised the pressure to 45 and the car was bucking like crazy under any amount of boost. Does this make sense to anyone?

So if I upgrade what size would be good? I was think 660s or 720s but I read the 720 could be hard to tune with just the maft.
I want to get something big enough so I dont have to upgrade again if I get a bigger turbo.

I will be getting dsmlink in the next few months so that should help.

Thanks again

 

[crunchymilk]

680cc would be fine, out of range for the evoiii

I'm still confused how you were able to run 150% at only 20psi, I would look into your a/f ratio and make sure you're not pig rich.

 

[JDR7919]

One more question.
My o2s are anywhere from .84 to .86 which could be on the lean side. But, when I increase wot the car bucks and blows black smoke which would mean rich. How could I be rich with low o2s? I know they are not very accurate but it seem it would not be that off.

 

[99gst_racer]

Yup, sounds like you're running pig rich. That black smoke is unburnt fuel. 550's are big enough for a 16g @ 16-20 psi. Take some fuel out to bring those IDC's back down and get your AFR back up where it should be.

 

[spyderturbo007]

What is your peak airflow during that run? Also, what is the corresponding SAFC-II correction value for that rpm?

If you are going with DSMLink, I would stay out of the throttle until you get DSMLink, and go straight to 950cc injectors.

They will idle like stock and you will have all the fuel "on tap" that you will probably ever need. Besides, they aren't much more than 650's.

Enjoy

 

[JDR7919]

I dont have safc only maft.
So 950s with dsmlink? I thought that large would give me advanced timing really bad?

 

[spyderturbo007]

Nope, that's one of the nice things about DSMLink. No matter what size injectors you go with, they will idle like stock and you will retain the stock timing maps (unless you want to change them )

DSMLink isn't a piggy back like the SAFC-II. It doesn't lie to the ECU about airflow so your timing will be consistent with the stock maps.

So, when it comes to injectors.....The bigger the better.

 

[dnhieu]

It is generally recommended to keep your IDC's below 85%.

Your profile says you are running 550's with a 16g.... How much boost are you running?

I don't understand how your IDC's are so high with the setup you have....

Hey guys sorry to bring back the past but this is the only thread i could find with someone the same problem as mine. my current set up is fmic,3" turbo back exhaust, big 16g set at stock boost but creeps to 17 psi, and maft translator for tuning, 650cc injectors, rewired walbro 255, full throttle bolt on fuel pressure regulator set at 37psi (vacumme line off). my injector duty cycle is at 108% at 7k. my buddie who had these injectors before me had a 20g at 20psi and was only getting 75% injector duty cycle so something is definetly wrong. i should be able to easily run 20psi + on a big 16g. does anyone know why my injector duty cycle is so high?

thanks for the help guys
david-