650cc Injectors and 120% duty cycle at WOT

[dirtbike_79]

I just recently put a 2g maf in my car and 650cc injectors.Now that I can finally do a WOT pull(becuase of boost creep to 23 psi) I am getting 120% duty cycle and I still have up to 23 counts of knock and my afc is set to +25 in high throttle. None of this is making much sense to me so any help would be greatly appriciated. Oh and I have even set my timing to 0 degree's to try and get rid of knock.

 

[JayRolla]

Have you tried to run the car with settings at zero. With those injectors you should not be adding fuel. When you ported did you make sure you researched and ported correctly. You cant just start porting and it fix the issue, you need to do it in a certain spot of the housing.

 

[gixxerdrew]

You could be not flowing enough fuel TO the injectors. Do you have a fuel pressure gauge? You can have a nice rich reading on a wideband but be lean on cylinder #1 and very rich on #4. danger danger!

first thing I would do is ensure that you are getting sufficient fuel flow. If that is good then bump your pressure to get a little more flow from the injectors and see if you can keep the AFRs decent without exceeding 90% duty. To me overboosting seems like a small problem relative to overboost + a lean cylinder. I would track down your fuel problem first. I made an ass ton of power on 720cc injectors and ran a lot more boost than that too, something is not right.

 

[dirtbike_79]

Yes I have ported it in the right spot, I know that the exhaust gasses need to be directed towards the wastegate and yes I have a fuel pressure gauge on my afpr and it is set to 43 psi(with line off). I lowered my high setttings way down and now above 4500 they are all at +1 but i still had to have 3000 at +13 and 4000 at +15 to get rid of low rpm knock.

 

[gixxerdrew]

Yes I have ported it in the right spot, I know that the exhaust gasses need to be directed towards the wastegate and yes I have a fuel pressure gauge on my afpr and it is set to 43 psi(with line off). I lowered my high setttings way down and now above 4500 they are all at +1 but i still had to have 3000 at +13 and 4000 at +15 to get rid of low rpm knock.

But what does it say the fuel pressure is during a WOT pull?

I'm worried about what your pressure is when the fuel is in high demand. If your getting plenty of fuel flow you can increase what your injectors will flow by upping your base pressure. But it doesnt make sense for you to be running out of injector at this point even at a pig rich AFR. I ran out on 720s at like 480whp....

 

[gixxerdrew]

Also when you say your O2 reading is not going above .87 even if you are "running extremely rich" how do you know your running extremely rich? O2 sensor is reporting lean mixture? Are you getting the "rich" thing from what the ECU is reporting? Or do you have a seperate wideband or something?

 

[bling5tatus]

nb o2 is not an accurate way to measure your AFR's, even during WOT.

You're probably rich knocking the crap out of your motor and washing out the cylinder bore with all that fuel. Good luck.

Oh, and yes, there is no such thing as >100% IDC.... use your brains people.

 

[gixxerdrew]

nb o2 is not an accurate way to measure your AFR's, even during WOT.

You're probably rich knocking the crap out of your motor and washing out the cylinder bore with all that fuel. Good luck.

Oh, and yes, there is no such thing as >100% IDC.... use your brains people.

It's accurate enough that unless your O2 sensor is totally broken .87 is too lean.

I tuned for years on a narrowband before widebands were available for less than $1000. When the first low dollar widebands came out I bought a ZT2, my narrowband tuning was less than 0.3AFR from where I wanted it. Narrowband is not accurate, that is correct. But its accurate enough to know that much.

 

[99gst_racer]

Any help?

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[dirtbike_79]

I know it was running extremely rich because there was a cloud of black smoke behind me and the car would barely run. What do you suggest I do about my fuel pressure? Get a line and run it up to the hood?

 

[gixxerdrew]

Did you test the fuel pressure alreday at WOT? Is it falling? Is it holding stable at base + boost? The car can blow smoke from different things and barely run from being too rich or too lean. I would actually trust your O2 sensor more unless I had some reason to think that it was broken.

Also you can blow smoke and barely run because cyldiner #4 is pig rich and blows fuel out into the exhaust while cylinder #1 is lean and detonating and barely running from fuel starvation.

 

[blownturbotsi]

I know it was running extremely rich because there was a cloud of black smoke behind me and the car would barely run. What do you suggest I do about my fuel pressure? Get a line and run it up to the hood?

Are you, by chance, venting your bov to the atmosphere?

 

[dirtbike_79]

No I am not venting my bov to the atmosphere. How do you suggest that test my fpr under boost? Start my car and pressurize the fpr line to 20psi?

 

[Rob10_99]

Ghetto way, run a line, hard/stainless AN/pushloc etc, to a fuel guage you can see while in car. Its easy on a dyno, but can be difficult in real driving.

 

[steve]

How do you suggest that test my fpr under boost? Start my car and pressurize the fpr line to 20psi?

Pretty much but if you just apply power to the fuel pump check connector you can vary the pressure at the reference port and watch your pressure change.

 

[Splitpi]

Pretty much but if you just apply power to the fuel pump check connector you can vary the pressure at the reference port and watch your pressure change.

Ahh... the simple way....

 

[gixxerdrew]

Pretty much but if you just apply power to the fuel pump check connector you can vary the pressure at the reference port and watch your pressure change.

Steve, I meant for him to check it under load like when the injectors are trying to flow a lot of fuel. What I am thinking is something like a kinked fuel line or dying fuel pump or bad O ring on the pump, etc

OP: Actually very common on DSMs and can happen without even the best tuner realizing when they install the fuel pump. The only way to see that is to test either on the dyno or on the street. Get on the gas at WOT and watch your fuel pressure. It should go from base and add rise to match boost pressure. If it doesnt, you have a fuel delivery problem. This happened to my buddy on the dyno when I was trying to tune him. He had to replace the fuel pump assembly that goes to the tank. Thank god we didnt do WOT tuning until the dyno too because his the POS AEM wideband didnt even pick up the AFR change but the dynapack/motec one did. I've tuned better on narrowband than that AEM WB. he ditched it for an innovate after that.

 

[JayRolla]

I still think he needs to just get the boost down too 18psi. Then do a log with the settings on the safc at zero. Bet his IDC's are lower. He is adding 25% fuel when he should be taking a little fuel out.

Anyways I was also having this issue with 550's. I installed a N/A FPR and it dropped my IDC's from 100+% to 85% at 6000rpms. Maybe you need some more FP behind the injectors.

 

[1gTurboTuner]

Is your 02 housing ported/polished? That may help with your boost creep problems.

Goodluck

 

[dirtbike_79]

My fuel pressure is set to 43 psi with the vaccum line off. The fuel pump and the AFPR are almost brand new, they might have 1500 miles on them.

 

[steve]

Steve, I meant for him to check it under load like when the injectors are trying to flow a lot of fuel. What I am thinking is something like a kinked fuel line or dying fuel pump or bad O ring on the pump, etc.

Makes sense if the signs are that he's going lean under boost. Still wouldn't hurt if it wasn't such a PITA to do in the car.

I've yet to see a case where a kinked fuel line or dying fuel pump or bad O ring on the pump, etc caused someone to go rich and blow black smoke even if it's only rich in one cylinder. (That would be an injector problem, the pressure difference between cylinders in the fuel rail can't be that extreme)

 

[gixxerdrew]

Makes sense if the signs are that he's going lean under boost. Still wouldn't hurt if it wasn't such a PITA to do in the car.

I've yet to see a case where a kinked fuel line or dying fuel pump or bad O ring on the pump, etc caused someone to go rich and blow black smoke even if it's only rich in one cylinder. (That would be an injector problem, the pressure difference between cylinders in the fuel rail can't be that extreme)

I have seen it from certain cylinder richness on my own car. Rich as hell fuel fouled plugs on one side of the motor and detonated lean and burned to a crisp on the other. It may be extreme but I can vouch for it happening.

Also on a friends car he moved the tune around trying to compensate for choked off fuel flow. He ended up pig rich in every part of the map except high RPM on boost. So hed blow big fuel smoke clouds on spool up, and low, mid rpms but run dangerous above 5500 with full boost. Either way I feel like we don't have a lot of data and trying to diagnose something so just trying to at least narrow it down.

I have also never seen a working O2 sensor pegged lean on a car that was actually running rich? I am not saying that I for sure think its that or anything. I am just suggesting to eliminate the potentially most damaging concerns first. There are some signs that say rich and some signs that say lean. I'd say to eliminate the possibility of being lean first. Thats just my opinion you know, YMMV. O2 sensors fail intentionally to read lean so it could be a dying O2 but it just makes me nervous some of the things hes describing.

 

[dirtbike_79]

I finally got around to checking to see if my fuel pressure is rising 1:1 and it is. I also checked for boost leaks and there are none except the bov. My o2 sensor is a bosch and it maybe has 2000 miles on it. Oh and with my upper rpm settings on my afc set to 0 the duty cycle is 101% but it is still knocking. I think I am just going to take it to a shop and get it dyno tuned.

 

[spyderturbo007]

You are running way to rich. The 2g MAS allows for about a 15% increase in airflow around the sensor over the 1g MAS. Mathematical correction for 650cc injectors is -31% to hit the factory AFR on the highest airflow map of 9.5:1. By setting the SAFC at zero on the high throttle map, you're running about 16% richer than stock at WOT. This is going to put you in the area of about 7.9:1.

Lean out the SAFC to -10%, make another 3rd gear pull and post up the log. -10% is still going to put you really rich, but we want to start rich and work our way lean. Most likely, you'll end up in the area of -20% or so when your tune is done, provided you are shooting for an AFR of 11:1.

 

[gixxerdrew]

I finally got around to checking to see if my fuel pressure is rising 1:1 and it is. I also checked for boost leaks and there are none except the bov. My o2 sensor is a bosch and it maybe has 2000 miles on it. Oh and with my upper rpm settings on my afc set to 0 the duty cycle is 101% but it is still knocking. I think I am just going to take it to a shop and get it dyno tuned.

Did you verify its rising 1:1 when your on boost? Or just in the driveway?

Other thoughts: CAS adjustment, phantom knock.

 

[dirtbike_79]

My logs with all the settings to 0 are:

RPM KNCK O2 TPS TIMA INJD
3906 0 .25 98.0 45 25.7
4125 1 .85 99.6 28 39.8
4218 0 .87 99.6 23 42.9
4406 5 .85 99.6 26 46.8
4687 4 .87 99.6 23 51.5
4718 3 .87 99.6 22 54.6
5062 3 .87 99.6 23 63.2
5250 3 .85 99.6 22 70.3
5406 3 .85 99.6 21 79.6
5562 9 .85 99.6 20 85.1
6125 20 .85 99.6 17 99.2
6375 19 .85 99.6 15 100.7