Here's the scoop. I have a galant vr4 with 8.8:1 compression, a ported head, tial gate, RC550s, safc, sitc, 2g maf, 2.5" upper ic pipe, walbro 255lph.
I was running 17psi (91 octane) and getting no knock, but my SAFC settings were up around 19-23+ between 4500rpm and 6500rpm *i have my points in 500 increments between 3000 and 6000*
This was required to eliminate knock. Well we checked my injector duty cycle, and it was peaking at 124%!!!
So.. in order to get the injector duty cycle in check, i lowered boost to only 15psi, and took my afc setting down to 3000=12 3500=12 4000=13 4500=13 5000=14 5500=14 6000=14 (all are +)
This got me no knock, and injector duty cycle of 97-100%. My karman readings were about 1850, and my o2s were about .89, however, at 17psi, with injector duty cycle through the roof, i could definitely feel a power difference.
My question is this, i guess... why is my injector duty cycle maxxing out at only +14% on the afc up around 4500rpm and higher? Do i need bigger injectors? (like 660's) And most importantly.. how much should i take duty cycle into consideration? Does it even matter? Am i running into fuel problems due to higher compression?

Any experienced advice would be greatly appreciated!

Why are you ADDING 14% more airflow on top of the 550cc injectors? Your AFC settings should be taking fuel out to compensate for the larger injectors, not adding it in. Go read one of the tutorials on how to tune with one.


Brad

Umm how is the car running with all the fuel?

You should be down around -15% not +15%

less fuel = knocka knocka
in other words.. i have tried less fuel.. my knock sum went from 0 to about 43

Well, that means that you are trying to run to much timing with less fuel...you need to adjust you timing (which you can't do) down so that you don't knock, not raise your fuel up...in some circumstances raising fuel is a good way to get rid of knock...but not in your case...you want the correct a/f ratio across the board...not a rich one.

but if your O2 volts are at .89...that seems good for a 1g right...they like .88-.90v and 43 counts of knock is TONS...I would think that your knock sensor and O2 sensor may be bad...knock sensor because of the huge amount of knock it was reading, and your O2 sensor because it is reading a decent O2 voltage when it should be reading pig rich. These are just my ideas though...your car is wacked.

try again. i have a sitc, i can adjust timing til i'm blue in the face..

well, excellent then...use timing to try and get rid of knock while maintianing a more constant and true A/F ratio also watch EGTs

The main thing that confuses me with your car is why your O2volts are still decent when the car obviously must be running pig rich judged by your settings.

Try zeroing out your fuel and see what happens...then take away some timing where you got knock...2-4 counts = -1 degree 5-8 counts = -2 degrees 9-12 counts = -3 degrees

if this doesn't help, then I think you have some F*cked up sensors.

good news / bad news
i bought a fmic, from a saab viggen.. for cheap, should make a nice fmic for a while
i found a large boost leak, my POS IC is cracked (same core as a mk3 supra, only smaller. POS)
when i get the viggen ic, things should change a bit!

SAABs us such tiny, gnat-sized turbos that I can't see a SAAB intercooler being able to support a turbo like a 16G.

just out of curiosity are logging with a POCKETLOGGER? if so the duty cycle you are looking at is logging 450cc injectors not 550cc so remove about 20-22% from your duty cycle. maxing our 550's sure is easy huh

Originally posted by Mitsuturbo
good news / bad news
i bought a fmic, from a saab viggen.. for cheap, should make a nice fmic for a while
i found a large boost leak, my POS IC is cracked (same core as a mk3 supra, only smaller. POS)
when i get the viggen ic, things should change a bit!

Click to expand...

A boost leak would've made it so you would have had to make it even LEANER, not richer like you had it.

Boost leak = less air than the ecu thought = more fuel
550's = more fuel than the ecu thought
+14% AFC = less air than the ecu thought = more fuel

Damn, Im surprised it even ran!

Originally posted by tsi20gawd
just out of curiosity are logging with a POCKETLOGGER? if so the duty cycle you are looking at is logging 450cc injectors not 550cc so remove about 20-22% from your duty cycle. maxing our 550's sure is easy huh

Click to expand...

Why do you say that it is for 450s? All the ecu knows is it gets x amount of air and therefore uses y pulsewidth. It then uses the pulsewidth to calc IDC. The difference in 450's vs. 550's is taken into account at the afc, before the ecu and pocketlogger. What the PL outputs is the IDC of the injector (assuming dead time is approximately equal for the injectors).

Ever thing about tweeking with fuel pressure.

I have 550's and have my SAFC settings up to +15 at 7500. I am running 20psi on my big 16g. Adding the fuel helps me run that much boost. I will be upgrading to 660's tonight though. More boost (more air) higher SAFC settings (more fuel). That is how I figured it. He is probly running the same principal. BTW I also have a walbro 255hp and buschur AFPR setup.

You forgot though, at the SAME afc settings, the injectors are ALREADY giving you more fuel. The afc changes the a/f RATIO, not the total amount of fuel entering the engine. This is a function of a/f ratio, fuel pressure, and injector size.

You should be leaned out.

Originally posted by tsi20gawd
just out of curiosity are logging with a POCKETLOGGER? if so the duty cycle you are looking at is logging 450cc injectors not 550cc so remove about 20-22% from your duty cycle. maxing our 550's sure is easy huh

Click to expand...

Nope, wrong.

IDC is calculated simply from the amount of time the injectors are open, compared to the amount of time avaliable for them to be open due to the length of 2 rotations of the motor.

If you are at 114% IDC, then you can at least lean it out until the injectors are at 100%, and see zero change in fuel delivery.

What is your base timing set at (check with a timing light while idling with the pin grounded and the logger UNPLUGGED).

What are the corrections you are using on your ITC?

My 14b requires almost 10% more fuel up top in order for me to run 18 psi of boost.

Is your MAF severely hacked?

No my 2g maf is not hacked at all.

My base timing is about 7 deg, i believe.

Pocketlogger is logging injector duty cycle, timing is running about 18deg. under boost.
My ITC is sitting at 0, -2, -2, -3, -3 That seems to keep knock to a minimum and make pretty good power.

I have since started running significantly less boost, since it's winter. I also bought a new EVO III 16g and a FMIC. I think my tuning curve is going to be COMPLETELY different soon anyhow.

Originally posted by tsi20gawd
just out of curiosity are logging with a POCKETLOGGER? if so the duty cycle you are looking at is logging 450cc injectors not 550cc so remove about 20-22% from your duty cycle. maxing our 550's sure is easy huh

Click to expand...

my car barely ran with 550's set on 0

i cant imagine what +15% would do

i have mine set up at minus 20 and less

When had a an SAFC II and 2gmas it ran almost perfect with Denso 660 I had to lean it out a little at on top but it ran great.

Originally posted by kpt4321
Nope, wrong.

IDC is calculated simply from the amount of time the injectors are open, compared to the amount of time avaliable for them to be open due to the length of 2 rotations of the motor.

If you are at 114% IDC, then you can at least lean it out until the injectors are at 100%, and see zero change in fuel delivery.

Click to expand...

Actually, it's the amount of time the ECU wants to keep the injectors open but as you point out once you go static (100% DC) on the injectors there is no more fuel to be had at that fuel pressure.

Steve

Originally posted by steve
Actually, it's the amount of time the ECU wants to keep the injectors open but as you point out once you go static (100% DC) on the injectors there is no more fuel to be had at that fuel pressure.

Steve

Click to expand...

Err... it's a percentage, and thus is describes that amount of time that the injectors are being requested to be open, compared to the avaliable time.

Everyone who is telling you that you're doing the wrong thing by having the corrections at +15% is wrong.

The 2g MAF will give the ECU a signal that is about 30% less than the 1g MAF. Then, the 550's add about 20% back into that. In the end, you need to add 10-15% to get everything back to zero, which is right where you are, so it makes perfect sense.

The reason your IDC was so high, was probably because of the boost leak.

yesu need to get 660s, i installed 660s after maxing 550s out and car was alot fatser and easier to tunr with more boost

i have upgraded to 650cc injectors and it helped immensely, but now i'm running at 99-100% IDC

wondering if i should go with 720's now

Then 13second is right.

You have (4) 450cc injectors right? = 1800cc of fuel per minute TOTAL capability at 100%.

With 550cc injectors a set of (4) would flow 2200cc at 100%.

With 650cc injectors 2600cc at 100%.

What we are saying is a dsm ECU has a fuel curve programmed into it calibrated for 450cc injectors, so when you use the SAFC, you lie to the ECU and tell it you are still running the 450's when really you are running 550's or 650's or whatever.

Default settings for 450's when using a SAFC is -0-.

Zero with 550's would be -18 because 550's are 18% bigger.

Zero for 650's would be -36 and so on.

I believe everyone else in saying you are WAY to rich.

Put it on the lower and do a pull.

Good luck and best wishes.

GSXTACY