106% duty cycle on 7psi. help!

[kamronman]

Ok, I've got plenty of bolt on modifications and i use mmcd datalogger. I logged a second and third gear pull and when i looked back on the graph, at 5700 rpm my injector duty cycle said 106.3%! I have stock injectors, and a rewired stock pump..wtf? It starts to cut top of third due to lack of fuel. I'm planning on getting a 255 and afpr so i can daily drive, will this lower my IDC or will i probably need injectors? If i do i'll save up for DSMlink.


thanks guys!

 

[okm12346]

whats your fuel pressure? Thats weird

 

[GooeyGus]

how much boost are you running? Still using the 14b?

 

[DJ23GSX]

Have you done a boost leak test lately?

 

[just90gs]

if your running the 14b you gotta be hitting to much boost or their is a leak. and too much boost is not like likily

 

[DJ23GSX]

if your running the 14b you gotta be hitting to much boost or their is a leak. and too much boost is not like likily

He's only running 7psi according to his title so its definatly not too much boost. I had the same issue and it ended up being a huge boost leak at the injector seals. A big enough boost leak will cause high idc's based on the amount of air the maf is seeing. The maf "thinks" its running a lot more boost than your seeing and the ecu is injecting extra fuel to compensate for it. Stock dsm's run more than 7psi so I'd assume your leaking boost somewhere hence the high idc's. Before the with the leak I was running 20psi and after fixing the leak boost went up to 23psi. Once I lowered the boost controller back down to a true 20psi with no boost leaks my idc's drop 12%.

Or your fpr isn't raising fuel pressure 1:1 while under boost. Start with a boost leak test first. Its easy and can tell you a lot.

One more thing I though of.... Sometimes the fuel pump o-ring on the sending unit goes bad and the pump leaks fuel back into the tank. That would put a real damper on fuel flow especially under boost.

Good luck

 

[DSMopar]

Previous poster is mostly right, probably a boost leak. Lack of fuel (low fuel pressure etc) wouldn't cause it though if you're running a stock ECU.

Edit: saw you're running an SAFC... what are your fuel trims at?

 

[DJ23GSX]

Do you get knock when you lean out the safc? What are your hi safc settings?

 

[kamronman]

I have the safc but i'm not using it. And yeah i did a boost leak test and there's only a SLIGHT leak. It mainly makes my car idle like crap. It's either inside the throttle body or injector seals. Where can i get injector seals!? -and for cheap Thanks guys! Once the problem is fixed, I'm going to be on dsmlink, walbro 255, aeromotive fpr, and some big injectors!!


Will new injectors come with new seals??

 

[misphit]

Uhhh before you go spend all that money, you should know that there is a known glitch with mmcd. The injector duty cycle does not compute correctly. If you're logging injector pulsewidth, you can use that to determine your CORRECT injd using this handy link:

Stealth 316 - Injector Duty Cycle Calculation

You're welcome.

 

[DJ23GSX]

Uhhh before you go spend all that money, you should know that there is a known glitch with mmcd. The injector duty cycle does not compute correctly. If you're logging injector pulsewidth, you can use that to determine your CORRECT injd using this handy link:

Stealth 316 - Injector Duty Cycle Calculation

You're welcome.

I've never heard of this with mmcd but I do know that there is a similar bug with the pocketlogger software and the idc max readings in the big number display. I've been in contact with them about it before and they do know about it. I used to see see over 100% idc's in big number display on pocketlogger software but when I would look at the same log in graph mode it would display the correct idc which were usually 10-15% less than what the big number display would show. Its definatly something to look into though.

 

[kamronman]

Yeah i'll try that. Can you guys explain what the eff is going on with my car under WOT then? ### 2nd and third gear cut out at high rpm now. And the logger shows 1 count of knock then automatic timing retard..Am i not getting enough fuel or what!?

Oh and i just double checked my duty cycle using that stealth 316 calculator, and i do have 108% duty cycle

 

[bboyalan]

You can also manually calculate your peak IDC with the equation mentioned in the link above.

(IPW x RPM)/1200

MMCd does in fact report inflated values because of its rate of sampling from the ECU. At high load, the ECU is busy firing the coilpack among other stuff.

I'm planning on getting a 255 and afpr so i can daily drive, will this lower my IDC or will i probably need injectors?

If you get those two installed, then there is a way to lower your IDC's using the stock injectors. You can moderately raise your base fuel pressure with the AFPR and tune with your AFC+logger. My 3000GT VR-4 is running 53psi as opposed to 3bar, and so my 450's are flowing ~500cc's

 

[kamronman]

Ok, I did a final 2nd and 3rd gear pull just now, with my ISC unplugged. because it's always making my idle surge. Here's my mmcd logging results.

RPM 4156 ~4375 ~4500 ~4812 ~5218 ~5687 ~6156 ~6687
INJP 18.68 ~19.96 ~22.01 ~23.55 ~24.31 ~20.73 ~19.96~14.84
TPS 99.6%~99.6%~99.6% ~99.6% ~99.6% ~99.6%~99.6%~99.6%
INJD 64.0%~72.6%~82.0% ~94.5% ~105.4%~98.4%~102.3~82.8
KNCK 0 ~ 2 ~ 2 ~ 1 ~ 1 ~ 1 ~ 0 ~ 0
TIMA 18- ~18- ~17- ~17- ~18- ~21- ~22- ~ 21-
02-R .89V ~.89V ~.89V ~.89V ~.87V ~.87V ~.85V ~.85V
AIRT 37.1F ~37.1 ~37.1 ~37.1 ~37.9 ~37.9 ~37.9 ~38.7
ISC 37.5%~37.5 ~37.5 ~37.5 ~37.5 ~37.5 ~37.5 ~37.5


(--Tires spinning--) (--3rd----)
RPM---6875 ~6781 ~7000 ~6968 ~6437 ~6031 ~5593 ~4187
INJP---16.89 ~16.63 ~13.56 ~11.26 ~1.27 ~2.04 ~8.19 ~21.50
TPS----99.6%~78.5%~99.6% ~99.6%~10.9%~11.7%~25.3%~99.6%
INJD---96.8%~93.7%~78.9% ~68.8% ~6.2% ~10.1%~37.5%~75.0%
KNCK- 1 ~ 1 ~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ 0
TIMA---18- ~18- ~20- ~23- ~24- ~45- ~45- ~27-
02-R---.83V ~.82v ~.82v ~.58V ~.74V ~.87V ~.76V ~.05V
AIRT---39.5 ~39.5 ~40.3 ~40.3 ~41.1 ~41.1 ~41.1 ~41.1
ISC----37.5 ~37.5 ~37.5 ~37.5 ~36.7 ~31.6 ~26.9 ~32.4


(Continued 3rd gear)

RPM---4375 ~4312 ~4437 ~4656 ~4750 ~4812 ~4843 ~5093
INJP---20.73 ~21.50 ~22.78 ~23.80 ~25.08 ~26.36 ~26.87 ~26.11
TPS----99.6%~99.6%~99.6% ~99.6%~99.6 ~99.6% ~99.6% ~99.6%
INJD---75.0%~77.3%~84.3% ~92.1%~99.2% ~105.4%~108.5%~110.9%
KNCK- 2 ~ 1 ~ 1 ~ 1 ~ 0 ~ 0 ~ 0 ~ 0
TIMA---17- ~17- ~17- ~17- ~17- ~19- ~19- ~19-
02-R---.89 ~.89V ~.89V ~.89V ~.89V ~.89V ~.89V ~.87V
AIRT---41.1 ~41.1 ~41.1 ~41.1 ~41.1 ~41.1 ~40.3 ~40.3
ISC----37.5 ~37.5 ~37.5 ~37.5 ~37.5 ~37.5 ~37.5 ~37.5

(-off throttle)
5187 ~5437 ~5406
26.36 ~1.27 ~1.27
99.6% ~30.8% ~10.5
114.0%~5.4% ~5.4
0 ~0 ~0
19- ~20- ~43-
.87V ~.87V ~.93V
40.3 ~40.3 ~39.5
37.5 ~37.5 ~33.5



Someone who's a master at this stuff please tell me what the eff is going on.

Keep in mind, my boost is creeping from 7psi up to 15ish area on a tial 38mm.

 

[bboyalan]

Your Injector Pulse Width numbers seem relatively high to me.

* INJECTOR PULSE WIDTH (range of 0 to 25 milliseconds "ms")

This is the actual amount of time that the injectors are open, not duty cycle. Duty cycle is roughly defined as the ratio of the amount of time a signal is "active" to the amount of time available for the signal to be active.

NOTE, once again every car seems to be different. I have personally run my 450cc's to 27+ ms and had a smooth pattern, great flow and no knock.

The one thing I will add is you want a value somewhere around 20ms at WOT. It must be a smooth, straight curve. If the value is jumpy at all your injectors are not squirting a smooth pattern and you will get detonation from this. It is more important that the signal be smooth than the actual number as on 91+ ECUs this number is what the ECU is "trying" to do, not that the injectors are actually open for that amount of time.

Basically, I believe that your injectors are currently spent and are being pushed pretty hard.

 

[DJ23GSX]

Someone who's a master at this stuff please tell me what the eff is going on.

Keep in mind, my boost is creeping from 7psi up to 15ish area on a tial 38mm.

I knew I should of asked you about boost creep a few days ago. What turbo are you running? This could explain a lot. 15psi on a stock turbo and injectors are probly getting close to maxing out the stock injectors. Are you 100% sure you have manual trans (450cc) injectors? Early automatic transmission turbo dsm's cam with smaller injectors (370cc iirc) and turbos.

 

[kamronman]

Yeah i have the manual transmission gs-t 450cc injectors. I'm on the 14b still, at least until it blows up i'll get an E316g.

I just picked up evo 560cc's last night! And i already have an safc i haven't installed yet. I have a walbro 255 and aem regulator in the mail on it's way from MAP. Sooo should i just wait and upgrade the fuel system and see how it goes? And would my duty cycle be higher than usual to compensate for a boost leak?

 

[DJ23GSX]

Yeah i have the manual transmission gs-t 450cc injectors. I'm on the 14b still, at least until it blows up i'll get an E316g.

I just picked up evo 560cc's last night! And i already have an safc i haven't installed yet. I have a walbro 255 and aem regulator in the mail on it's way from MAP. Sooo should i just wait and upgrade the fuel system and see how it goes? And would my duty cycle be higher than usual to compensate for a boost leak?

Yeah I'd throw everything in and go from there. I don't see why you shouldn't like I said before your knock and timing see pretty good. You just might be closing in on the max for the stock injectors.

You would see higher idc's because in order for your turbo to make say 15psi at the intake manifold with a boost leak its actually pulling more air than that through the maf to compensate for the leak. So the maf is seeing enough airflow to run say 18psi (huge boost leak) but since boost is leaking out before the intake manifold your only seeing 15psi on the guage. The maf don't know you have a leak and its trying to add fuel according to amount of airflow it sees coming through it. Make sense? I don't know why I'm having so much trouble explaining that clearly long day I guess.


I'm having trouble trying to figure out why your 14b is boost creeping with a tial 38mm. Any clue what color/psi spring is in it?
Well from the looks of your pics your running the wastegate off the bov line and I don't even see a boost controller. Old pics maybe? I was always told to leave the bov line alone and tap your wastegate/boost controller off the turbo outlet or j-pipe. That line helps hold the bov closed while under boost and you don't want to be bleeding pressure of it possibly making it open slightly under boost.

 

[kamronman]

Yeah i totally understand what you're saying. And i run it off the BOV line because i haven't gotten a nipple welded into the j-pipe yet. It's on my list. And the spring opens at 7-9 psi, then creeps only at high rpm. and When i hook a vacuum hand pump up to the gate, it fails to hold vacuum pressure..And when i capped off the line to the gate from manifold the car still ran the same as it always had(crap from vac leak). I idle at like -14, -15 vacuum too..

 

[kamronman]

Can anybody tell me if that's normal vacuum for a slightly modified 1g? Still have stock cams. A buddy said that's proper vacuum buy i'm not buying it.

 

[toofast82]

I idle at like -14, -15 vacuum too..

With stock cams on a warmed up car it should be more like -18-20
You need to positively fix these vacuum/boost leaks if its causing poor idle and vacuum

 

[DJ23GSX]

With stock cams on a warmed up car it should be more like -18-20
You need to positively fix these vacuum/boost leaks if its causing poor idle and vacuum

Agreed 100%. I'd say you got something going on as most stock cam'd dsm's i've dealt with pull closer to -20 vacuum at idle. When was your last boost leak test? Are you doing it the same way as this

IC Pipe Tester

How much pressure are you adding when leak testing? I've always boost leak tested to 25psi minimum and spray soapy water all around the common leak areas. Lower injector seals, tb gaskets, i/c pipe couplers etc.

 

[DSMopar]

I'm at 19-20 inches at idle... 15 sounds low...

 

[kamronman]

I boost leak tested at a chevron's free air station last week, using my boostpro tester in the intake pipe, I sprayed it till it slowed almost stopped pressurizing at 15psi, so i let off to listen and the hiss is either an injector seal or throttle body gasket..So i have new gaskets and new injectors with seals in the mail. I couldnt quite make out where the leak was coming from specifically. So i should use soapy water?

 

[DSMopar]

Soapy water + spray bottle. Also move your hand over areas and see if the noise changes (helps you zone in).