Why is my injector duty cycle so high?

[PropXprt]

TIMA O2-R TPS RPM KNCK INJP Duty Cycle
27° 0.80V 30.6% 3063 0 4.61ms 15
27° 0.76V 30.6% 3156 0 4.61ms 15
28° 0.06V 30.6% 3250 0 4.86ms 16
28° 0.06V 30.6% 3313 0 4.86ms 17
28° 0.68V 30.6% 3375 0 4.86ms 17
28° 0.78V 31.4% 3469 0 4.86ms 18
27° 0.59V 32.5% 3531 0 5.12ms 19
27° 0.10V 33.3% 3625 0 6.66ms 25
26° 0.84V 35.3% 3750 0 7.17ms 28
26° 0.88V 37.6% 3875 0 8.45ms 34
24° 0.90V 38.8% 3969 0 9.98ms 42
21° 0.92V 39.6% 4125 0 11.26ms 49
18° 0.92V 51.4% 4313 0 15.36ms 70
18° 0.92V 68.6% 4469 0 18.69ms 89
18° 0.92V 100.0% 4719 0 18.69ms 94
18° 0.92V 100.0% 4875 0 16.64ms 86
19° 0.92V 100.0% 4969 0 16.64ms 88
20° 0.92V 100.0% 5188 0 16.38ms 90
21° 0.92V 100.0% 5344 1 16.64ms 95
21° 0.92V 100.0% 5500 1 16.38ms 96
21° 0.92V 100.0% 5688 1 16.64ms 101
22° 0.92V 100.0% 5781 1 14.08ms 86
24° 0.92V 100.0% 5969 0 9.47ms 60
30° 0.70V 100.0% 6188 0 9.47ms 62
28° 0.57V 100.0% 6000 0 11.26ms 72
23° 0.59V 100.0% 6250 0 6.40ms 42
32° 0.76V 9.0% 6344 0 0.00ms 0
45° 0.16V 9.0% 5969 0 1.28ms 8
45° 0.00V 9.0% 5688 0 1.28ms 7
45° 0.00V 9.0% 5344 0 1.28ms 7
45° 0.06V 9.0% 5094 0 1.28ms 6
45° 0.04V 9.0% 4844 0 1.28ms 6
45° 0.02V 9.0% 4563 0 1.28ms 6
44° 0.02V 13.7% 4313 0 1.28ms 5
42° 0.16V 18.8% 3688 0 1.79ms 7
39° 0.02V 19.6% 3031 0 2.30ms 7
38° 0.02V 20.8% 3156 0 2.56ms 8
37° 0.39V 22.4% 3156 0 2.82ms 9

Do you all have any ideas why my injector duty cycle is so high. I am having a hard time getting rid of this (backfire.) I don't know and can't tell if it is because I am to lean or to rich. This pull was done at 15-16 psi. (All of my current mods are in my vehicle profile)

[pneumo]

I can think of two reasons for getting a backfire; either you're running too rich, or you're getting maf overrun.

Your profile doesn't show a different maf, so I assume you're still on the stock maf. Have you modified it at all? Since your profile doesn't show a SAFC or maft, you are limited in what you can do. Try simply backing out the large plastic adjusting screw in the bottom of the maf. This will lean out the A/F ratio slightly and push off maf overrun.

[vr4play]

According to your O2 #s, you are running rich. How do you compensate for your bigger injectors, the chipped ECU? From your profile, you are only running 16psi on 680's, turn up the boost to 20psi and see what you get.

[PropXprt]

I am only running a stock maf with 680cc injector compensation on the chip. I was going to turn the boost up more but I was a bit hesistant because of the backfire. Tonight or tomorow I will turn the boost up some more and see what I get and if that doesn't help I will modify my maf like mentioned. I will report back in a day or two with another log or two.

Thanks for the replies.

Rob

[Dark_Horse]

Originally Posted by vr4play

According to your O2 #s, you are running rich.

Narrow band O2 isn't the best way to tell if he's running rich/lean. Even if narrow band were a good indicator, a 0.92 isn't rich.

PropXprt - You have very good timing #'s even under full boost, you could try leaning your fuel out from 4K up. Can you log gm/sec or lb/min?

I have a hard time believing that you have maxed out 680cc injectors since they are good for 47lbs/min at 100% IDC (11:1 A/F ratio). I seriously doubt that an E16G can put down that many lb/min at 11:1.

[PropXprt]

I use MMCD tools for logging; is there a way I can log these parameters with this. I never could figure out how or where to log lb/m using this program. Also what is gm/sec? Maybe gallons/minute. Thanks again you all.

[Dark_Horse]

Originally Posted by PropXprt

I use MMCD tools for logging; is there a way I can log these parameters with this. I never could figure out how or where to log lb/m using this program. Also what is gm/sec? Maybe gallons/minute. Thanks again you all.

I'm sorry, I meant grams/revolution.

From a quick glance at the documentation, possibly logging air volume would give you something like gm/rev or lb/min?

I'm sure you've seen this site, but just in case you haven't. http://mmcdlogger.sourceforge.net/

[THE REAL DEAL]

Originally Posted by Dark_Horse

Narrow band O2 isn't the best way to tell if he's running rich/lean. Even if narrow band were a good indicator, a 0.92 isn't rich.

true. that's more close to stoich than anything.

[spyderturbo007]

My understanding is that you can only log MAS frequency on a 1g, which is about useless.

[PropXprt]

I didn't want to start another post, so I am bringing this one back up that I started a couple weeks ago. Well, I was looking through some previous posts and I read that base pressure is supposed to be 38 (with the vacuum hose disconnected from the fpr), well I checked my base pressure the correct way and found out that my base pressure is actually 44psi, but when I hook that hose back up it goes down to 38. I didn't think I would need an afpr with my 190lph, but I guess I do. Well this brings me to my next question, would the base fuel pressure being raised above 38 cause my injector duty cycles to be high? Thanks again for input, I feel blind trying to diagnose this problem alone.

[pneumo]

So your base pressure is higher than stock, which means it'll make your car run a little richer. Fuel pressure won't have any effect on duty cycle.

Did you get a SAFC or some type of fuel control? Even with a stage 3 Keydiver chip you'll still need some fuel control to fine tune it.

You're not overrunning the FPR with that pump, but you could use an AFPR to lower the pressure and lean it out.

[scottsee]

Originally Posted by pneumo

So your base pressure is higher than stock, which means it'll make your car run a little richer. Fuel pressure won't have any effect on duty cycle..

sorry, fuel pressure dirrectly effects IDC. 450cc injectors with 44bfp will have lower IDC on the same setup then 450cc on 37bfp. Thats why people increase their bfp as a bandaide for smaller injectors.

Originally Posted by pneumo

You're not overrunning the FPR with that pump, but you could use an AFPR to lower the pressure and lean it out.

If you have a stock FPR, either your fuel pump is over running your regulator, or their is somthing wrong with it, wether its a return line restriction, bad spring, ex.

the only way yo test the FPR over run is to replace the fpr with a known good one, and recheck.. I was one of the very few who have over running my FPR on a rewired 2g pump. Not a big deal, AFPR are an upgrade

[PropXprt]

I had an safc a while back, but wasn't able to tune the miss out of it so I pulled it out. I guess I will put it back in and try again (hopefully I'll have some free time in the next few weeks.) I have another stock fpr I will swap and see what happens. It might be a while before I get to this but I will tell you all if and what fixes this problem.

[pneumo]

Originally Posted by scottsee

sorry, fuel pressure dirrectly effects IDC. 450cc injectors with 44bfp will have lower IDC on the same setup then 450cc on 37bfp. Thats why people increase their bfp as a bandaide for smaller injectors.

That only applies if they have some sort of fuel controller like a SAFC or MAFT. The ecu doesn't know what the fuel pressure is. If pressure is raised without compensating for it the ecu will still use the same injector duty cycle to match the airflow it's seeing. There is no feedback during WOT so the ecu doesn't know how rich or lean it's running, that's why they call it 'Open Loop'. That's why I'm thinking PropXpert is having rich misfires- 92% DC with 660 injectors and 16 psi boost is too much fuel.

Originally Posted by scottsee

The only way to test the FPR over run is to replace the fpr with a known good one, and recheck.. I was one of the very few who have over running my FPR on a rewired 2g pump. Not a big deal, AFPR are an upgrade

There's another way to check for FPR overrun. Since most DSM's have 18 vacuum at idle you should see a 9 psi drop in fuel pressure when you re-connect the hose to the FPR. I tried a stock fpr and a Walbro 255HP on my car once. The difference in fuel pressure with hose on/off was only 2 psi, plus the fuel pressure was around 50psi. That's overrun. At that point the FPR was not controlling the fuel pressure.

There's nothing wrong with 50 psi base pressure as long as it drops to 42 psi with the hose connected.

Big cams that idle at 12 vacuum should see less of a difference, around 6psi would be normal.

Since PropXpert is seeing about 6 psi difference in fuel pressure when the hose is on/off, I'd say it's a mild case of FPR overrun, nothing extreme. Overrun of this level has much less effect when at WOT than at part throttle cruising since the excess fuel volume is being used by wide open injectors.

[andymoraitis]

If you're running a basic Keydiver chip with injector compensation, the ECU is still running the 9.5:1 target A/F on the factory tune. Add in a couple of boost leaks and it'll drive IDC up. If you don't want to use the AFC, have Jeff map you the identical chip on an 11.5:1 tune and you'll see a huge difference. This is preferred to running the AFC and taking away fuel which will jack with the airflow tables and increase the timing making it harder to tune out knock.

A chip upgrade is twenty bucks. I'd certainly look into it.

Keep us posted,

Andy

[scottsee]

I appoligise pneumo. I don't know why I thought he had an safc. I should really stop skimming posts. your %100 correct. Sorry.

[pneumo]

Thanks, Scott. I didn't get butthurt by your comments, so we're cool.

[PropXprt]

I will try the easy route first by sending the chip in and getting it redone for the 11.5:1 tune. Thanks again for the help, and sorry I am slow getting back to you all, my life is hectic right now.

[95blackGsTurbo]

Get a log of 100% TPS from 2500-7k.

[PropXprt]

I can do it at ~10-13psi but no more, or I will get that stutter.