Need help with fuel

[Zerocygnal]

I'm pulling a massive knock count at any kind of acceleration over 25%. After logging I saw that my Injector Duty Cycle would never go over 40%, and the pulse width was always below 13.00 (should be 22.00 or more at WOT). I definately have a fuel issue..my question is where? Is this a faulty pressure regulator? Would that even effect the electronic readings of the injectors?

Thanks...would like to have my DSM running right.
This knock is killing my timing.

 

[brads]

If it was a fuel system hardware problem, it wouldnt change your injector pulsewidth. Your injector PW would be high, but your O2s would go really lean. What makes you think your PW should be 22 instead of 13?

If you are pretty sure that your PW is that much lower than it should be, it has to be that the ECU isnt seeing as much air in. Check your intake for leaks before the turbo. Also make sure your airflow, and intake air temp, looks good with your logger.

Brad

 

[Zerocygnal]

All of my prior runs with the logger have been 95% D/C and 22 to 24.00 P/W. That makes sense...I couldn't see that making a big difference. The air temps were a bit nasty...but the same readings above provided 0 knock with the same temps. I know for a fact that the intake tube is good. I just had it out the other day to powdercoat it. So you seem to be leaning towards the MAF....god I hope it's not that...

RPM 4000
O2 0.98 ???
TPS 100%
Timing 7
Knock 39
Air Volume 4 (used to hit 6 at WOT)
Air Temp 107 deg F
Inj D/C 41.88
Inj P/W 12.564
ISC 98 steps

 

[brads]

Sounds to me like you already have your answer. Your air volume(basically the same as the Hz, just on a different scale), used to be 6, now its 4. Lower air volume = lower injector pulsewidths. They are even the same ratio lower, 6:4 is roughly the same as 22:13. So thats why you are going lean, is you are reading less air in.

You just had the intake tube out to be powdercoated. Look for leaks at the clamps between the intake, turbo, MAF, and of course the BOV return tube. Also check that any other lines that go to the intake(PCV etc) are connected. I doubt its the MAF itself, it would be too coincidental if it failed right then.

Brad

 

[Zerocygnal]

Let me ensure I am interpreting this correctly. What you are saying is that everything is within a normal ratio "IF" I were running less air. Hence the ECU is reading less air when it is actually getting more air (air leak.) And I am getting a proportionate amount of fuel based on what is being read?

So what is with the O2 reading? Should it be reading a lean condition? Based on the O2 readings, everything's all good and it shouldn't be knocking.... I thought that if it was leaking air the O2's would lean out and the ECU would start dumping fuel...


I really appreciate all your help...probably pulling your hair by now .

 

[brads]

Originally posted by Zerocygnal
Let me ensure I am interpreting this correctly. What you are saying is that everything is within a normal ratio "IF" I were running less air. Hence the ECU is reading less air when it is actually getting more air (air leak.) And I am getting a proportionate amount of fuel based on what is being read?

Yes

Originally posted by Zerocygnal
So what is with the O2 reading? Should it be reading a lean condition? Based on the O2 readings, everything's all good and it shouldn't be knocking.... I thought that if it was leaking air the O2's would lean out and the ECU would start dumping fuel...


I really appreciate all your help...probably pulling your hair by now .

The O2 signal should read lower, it doesnt add up. The O2 sensor output should be lower just from how hot you are getting it from the timing retard. O2 sensors can go bad though. The ECU won't dump more fuel based on the O2 sensor at WOT, the O2 feedback is used for idle and cruise. Everything else points to the airflow, and its a relatively easy thing to check and fix.

Brad

 

[Zerocygnal]

That clears alot up alot about O2 readings.
If it matters I'm running 10psi of boost. Christ...have you ever seen a logger hit -1 BTDC???! I have! The prior readings were at 18psi with no knock.

I just replaced the O2 sensor a week ago, the original was giving the same readings...just wanted to ensure that it wasn't flaky.

One thing I did forget to add, the vacumm is reading about 15Inhg. Before this started this actually started happening it was at about 18Inhg. I'm not sure if the reading is a "direct result" of the misfire, or "causing" the misfire. I've looked all over the intake and induction system and can't find a thing out of place.

I'll check for air leaks in the intake pipe and pressurize the system at the turbo inlet and see what I can find. From what I've collected you feel it's an issue before the turbo inlet so I'll start there.

I'll keep you posted.
Thanks for your help,
Ty

 

[Zerocygnal]

Okay...ran a pressure test yesterday. Well the Upper IC must have clamped down on the flat side of the intercooler connection. I was losing about half of my air right there. That is taken care of, the engine runs alot better. I'm still getting knock and low air readings. I pressurized the intake to 22psi and it slowly bled off to about 10psi then almost completely stopped. The fuel is still right in it's ratio with the amount of air that's flowing. about 1107hz airflow. Used to max out at 1607hz..but that was at 16-19psi. I don't want to turn it up until I find out what is causing the knock. Any ideas on how to better test the actual intake pipe for leaks?

Today's launch log

 

[brads]

Well, the reason I was telling you to look for a leak before the turbo, is that there is always vacuum there, and unmetered air will get INTO the system at that point, and make you read less airflow than there really is. If you have a leak after the turbo, then under boost, the metered air leaks OUT, so more air is sucked in through the MAF than actually goes into the engine. This would cause higher than expected airflow readings, and/or boost dropping off.

A leak before the turbo is more likely to cause leanness, and knock, a leak after would be more likely to cause it to run rich, have bad timing, not hold boost, but knock isnt as likely. Thats why I expected you to find a leak before the turbo, plus since you said you just had the intake pipe off, that seems like a good thing to check.

To be honest, I have never pressure tested my intake. The times I suspected leaks, I just went around and checked all the couplers and hoses by hand. Scientific? no. But it seems good enough. Double check the clamps between the intake, MAF, and turbo, and then the PCV hose to the inlet, as well as the hose to the manifold.

Also, your O2 values seem to reflect that the car isnt as rich now as it was before you found the leak in the IC piping. So while that wasnt THE problem, that was a problem.

How much boost are you running now, compared to what you were running with the higher airflow? Does it seem like the airflow decreased proportionally with the boost? How quickly did this knock issue come up, and did it come up right when you did the work on the car?

Brad

Originally posted by Zerocygnal
Okay...ran a pressure test yesterday. Well the Upper IC must have clamped down on the flat side of the intercooler connection. I was losing about half of my air right there. That is taken care of, the engine runs alot better. I'm still getting knock and low air readings. I pressurized the intake to 22psi and it slowly bled off to about 10psi then almost completely stopped. The fuel is still right in it's ratio with the amount of air that's flowing. about 1107hz airflow. Used to max out at 1607hz..but that was at 16-19psi. I don't want to turn it up until I find out what is causing the knock. Any ideas on how to better test the actual intake pipe for leaks?

Today's launch log

 

[Zerocygnal]

I'll check the intake pipe again. I'll silicone seal some spots that could be a problem.

When I was running a 1607hz airflow I was at 16-18psi. In the 1000hz range I am only running 10 to 12psi. Proportionately? I would imagine so, I was under the impression the two were directly related. If 10psi=1000hz then I would say that at 18psi would be around 1620hz it just doesn't read that high. 90hz per 1psi roughly. Just an example...

The knock thing...that came up all of a sudden. The day before the car ran the best launches it has ever had. Air Volumes of 6, 1607hz, 22.00 P/W and steady, 92% duty cycle...I don't know what happened, when I parked it everything was great. The next morning it ran fine, later at a stop light I noticed my engine seemed to be missing. When I accelerated at green my logger alarm function when nuts.

When I pressurized the intake I went over the PCV area with a soapy water and 22psi in the intake...nothing. Just the rubber caps atop the throttle body kept shooting off . Got that fixed too.

 

[brads]

Ok, from your first few posts, you made it sound like the change in airflow and duty cycle was unexpected. I thought you were talking about at the same boost level initially. It sounds like everything is what you would expect for a change in boost level, except the knock.

I wouldnt stress much more on the boost leaks, you found one, that will probably help your car some. If there are other ones, they arent the cause of your car running the way it is. I also wouldnt expect it to be a fuel pressure/supply problem, you would see that in the logs as it leaned out. Check mechanical stuff. Plugs. Compression, etc. If you read the plugs, you might be able to get an idea which cylinder(s) are causing problems.

Also, just to double check, was your car running good AFTER you put the new intake back in? Did you do any other work then?

Brad

 

[Zerocygnal]

At first is was unexpected...that is..until you made me realize that it had decreased proportionally with the air. That was my own mistake....what I had done is compare the current logs with my healthy engine logs. I didn't consider boost level when I should have. For some reason I thought that the lesser airflow was causing the drop in boost, and not the other way around. Thats all said and done now. I just need to turn up the boost when I resolve the knock issue.


I'm not sure I understand your last question. To make an attempt to clairify...the engine was running fine. The last thing done to it was a month before the problems, and it was a valvecover replacement.
OR
If you are asking if the car is running "better" after the pressure test, the answer is yes. I found the boost leak, and like you said I realized it was not "the" problem, but "a" problem. At this same time I had to remove the intake to do it...so it may have very well partially sealed the intake leak when I reinstalled it. (if that's what you are getting at). No other changes were made.

Mechanical....really didn't want to go there. Kinda of strange to be all of a sudden at a stoplight..not impossible. For what it's worth the engine doesn't smoke even a little bit. Should I do a leak down test as well?

Thanks again,
Ty

On a good day...
http://www.geocities.com/zerocygnal2003/Data.htm

Check the Launch 1 Graph you'll have to manually enlarge the pic...it keeps scaling it down.

 

[Zerocygnal]

Good news... I took off the intake pipe and the upper IC. I sealed the couplers at their connecting points with silicone. I then pressurized the systemto 25psi at the turbo inlet and the it took about 2 solid minutes for it to leak down to 10psi. I went over the intake connectors, siliconed them, adjusted the clamps and reinstalled it. Went out to log and this is what I got...
The idle is a little high and base timing is off. But I adjusted them when it "Was" leaking. I'll re-adjust them and run it again. I'm sure I can get 0 knock like I did before. I need to turn up the boost now.

11-12psi run, 75deg air temps

More input?
Thanks for everything!
Ty

 

[brads]

Jeeze your cars tuning must have been really weird to compensate for all of that.

Have you been keeping an eye on your fuel trims? How far out of whack they were, and where they are now?

Boost leaks after the turbo usually make you run richer than normal. And fixing them leans you back out. But as you just fixed those the second time, it made you run a little richer. And you are reading higher intake airflow too. I am betting the leak you found then was the one at the intake. Your intake leaks have me somewhat stumped, I guess I havent seen any that were that bad in person.

I'd still pull the plugs, and check them. As far off as your mixture had to be, it couldnt hurt to see how they are.

Brad

 

[Zerocygnal]

I know...I thought it would help but I didn't think it would almost completely resolve the problem. My focus was the intake...I decided I would seal every possible place on it. I never did have the opportunity to perform a compression test.

I haven't really ever paid much attention to the low, mid, and high fuel trims...they usually always seemed to stay the same. I'll change my log program to include them. It's running way rich now, but I figure the soon added boost and increased timing should take care of that. I will also check the plugs. I would like to see what all this detonation has done to them. Even at 10psi it feels like it's making crazy amounts of power...I can't wait to see what 18 will do. I'm sure you know how misleading a seat of the pants dyno feels .

Look, I really appreciate all of the suggestions, experience, and time you've dumped into this thread. Without the suggestion I doubt I ever would have questioned the intake pipe. I really learned alot from this experience.

Thank you,
Ty

 

[brads]

Glad I could help, and good to see that you figured it out, and got the car running better again.
I still don't get why it was running the way it was, showing that it was rich, AND getting knock, as a result of the boost leaks. I have heard people talk about rich knock, but havent seen it in person, maybe that was it? The important part is that its fixed now.

Brad

 

[Zerocygnal]

I'm not sure about the whole rich thing....I think the O2's had to be misleading. I normally get about 20mpg....this last tank of gas got me 26mpg and that has NEVER happened before. I would think that it had to be running extremely lean for that to happen. Who knows..I'm just glad it runs good again.

 

[Zerocygnal]

Low Trim 131%
Mid Trim 139%
High Trim 139%

 

[Benji]

Originally posted by Zerocygnal
Low Trim 131%
Mid Trim 139%
High Trim 139%

All of them a little high I think!

Brad, wondering if you could help me out as well?

I am also seeing knock ... too much, more than anyone would want. I get around 32-35 counts of knock around 5700-6000 rpm's. My O2's are between .88v and .90v. My injector D/C is usually around 87% but I have seen up to 94% with the same knock count but higher O2's. Both ways I see a max of 1606HZ airflow around 5500 rpm's.

Now I am running 14lbs of boost with only a UICP, ported 14b and MBC!

Any advice is greatly appreciated.

Maybe I should check my intake pipe first?

 

[brads]

I agree, that those trims do seem a little high. Have you run the car for a while since fixing all of the leaks you found? It might take some time for the fuel trims to normalize. Also, if you have done anything like pull the honeycombs in the MAF, that would make them be higher than normal.

Benji, if you havent done it before, checking for boost leaks is always a good thing, especially since you have put an upper IC pipe on it. You might also want to check the base ignition timing, to see where it is.

Also, on the 1Gs, the pocketlogger seems to not be able to read airflow past 1606Hz. So you probably are flowing more air than that.

http://www.dsmtuners.com/forums/showthread.php?s=&threadid=49844


Brad

Originally posted by Benji


All of them a little high I think!

Brad, wondering if you could help me out as well?

I am also seeing knock ... too much, more than anyone would want. I get around 32-35 counts of knock around 5700-6000 rpm's. My O2's are between .88v and .90v. My injector D/C is usually around 87% but I have seen up to 94% with the same knock count but higher O2's. Both ways I see a max of 1606HZ airflow around 5500 rpm's.

Now I am running 14lbs of boost with only a UICP, ported 14b and MBC!

Any advice is greatly appreciated.

Maybe I should check my intake pipe first?

 

[Zerocygnal]

I'll check them again...that was about 2 days after the leak was fixed. I agree they are quite a bit high...it's just that my O2 readings are contradicting the fuel trims...
Still kinda knocks...I've been real busy lately..I still need to set the timing and idle again. That will probably resolve alot of those issues. Like I said before I set them when the intake pipe was leaking so it's not accurate.

 

[Zerocygnal]

Oh man...I'm going to commit myself. I friggen checked the timing and it was 15BTDC... I thought it was set to 5 but TDC was the other direction. Couldn't see it till I got the thing in direct sunlight. Runs like a top now and the air leaks are fixed. I'm pulling a consistant 18psi and it screams.
Thanks for all your help with the other stuff Brad.

 

[brads]

Good to hear you fixed all the problems. Nothing more satisfying than fixing it all yourself right? Well, except maybe embarassing some cocky V8 owners, thats pretty satisfying too

Brad

 

[Zerocygnal]

Indeed! One other question though....what's up with the Fuel Trims...?
High 139%
Mid 126%
Low 139%

And then pulling .92 @ WOT

I would ask if that's possible..but I'm doing it.