Topic: Help! Running rich after New GT 2871 and DDM tune

[miller11386]

Can that be saved into a running log file with display on a scale?

Here are some quick charts from the data... sorry they are crude, but its the best I can do with the tools I have!

http://www.skyroadster.com/forums/attachments/f5/40502d1305767944-car-running-rich-has-code-p2195-sky-log-charts.bmp

[shabby]

ST FTRM1(%)      29.7

You need some maf adjustments assuming you have no boost leaks, that's why you're throwing that lean code. The short term fuel trim peaks at +/- 30, after that it throws a rich/lean code.

[miller11386]

The new theory is that the MAF is seeing chop from the turbine blades. Dave mentioned that he has had issues with other turbo kits on the stock airbox. Dave is sending me a new intake to try to get the MAF farther away from the turbine and the surging.

I saw that the short term fuel trims were high, however the long term were normal or at 0.

I was also curious what the abbreviation LT SEC FT1 & LT SEC FT3 meant. It did not show in my logs, but when i had "instant" data from the interface, these were reading -7% and -100% respectively.

I was also curious if it was normal for the front O2 sensor to be reading both + and - mA readings. If you look at the chart that I posted, you can see them hopping along. I also dont understand why it reads in mA rather than a voltage. o2 #2 reads the voltage that I would expect.

Unfortunately I don't have the experience to know what normal looks like, and with so few of these 2871 kits installed, it is hard to compare. I would be curious to see how many of the 2871 kits that are installed, how many of them use the stock airbox.

[Arabas]

Miller do you hear surge when you WOT?

[shabby]

The new theory is that the MAF is seeing chop from the turbine blades. Dave mentioned that he has had issues with other turbo kits on the stock airbox. Dave is sending me a new intake to try to get the MAF farther away from the turbine and the surging.

I saw that the short term fuel trims were high, however the long term were normal or at 0.

You don't need a new intake, all you need are maf adjustments in the low rpm/load section, the new intake will need maf adjustments too. The new turbo is ingesting more air at idle and the ecm can't compensate enough. If you had hptuners you can get this fixed in a jiffy.
The reason the long term fuel trim is at -7 is because its an average reading, if you'd reset the ecm and idle the car for an hour it would just to 30 just like the short term fuel trim.

Not sure about the other pids as i dont monitor them.

[miller11386]

I never hear compressor surge at WOT. I hear some slight compressor surge, but that is only when i let off the gas slowly enough to not get the BOV to actuate. It did the same with the stock turbo on the car. I let off enough to cause a surge, but not enough to open the BOV. Its only slight and doesnt last more than a half of a sec.

The surge dave is alluding to (if I understand correctly) is due to is the pulsation of the blades chopping the air up as it is coming in. Therefore it would not be a smooth flow by the MAF. This could cause the MAF to get the improper readings. I was getting only .34 lb/min at idle and that seems low. He thinks that moving the MAF farther away would help smooth this condition out.

I am curious what the LT SEC FT3 means..... - 100% I assume is the max. Everything else jumped around and moved some at least, however that value remained pinnned at -100%


And Shabby, I am not sure if I do or do not need the intake. Dave asked me to try it, so that is what I will be doing.

[Arabas]

miller, surge occurs when stepping on the gas not when you let it off. maybe you talk about bypass valve flutter?
i believe you should try whatever Dave suggests.

[miller11386]

Not sure what surge you are referring to Arabas...

Compressor surge occurs when you take your foot off the gas and the pressure is not discharged from the charge tubes. It tries to find its way out via the compressor, causing a surge (the way I understand it).

I dont have a bypass flutter because I dont have a bypass valve on my GT 2871 Turbocharger

[Arabas]

AFAIK, compressor surge is when the turbo pushes more air into the engine than what the engine can use (inhale). so the flow of air gets reversed (as if hitting a wall) and goes back to the compressor. sorry for the poor explanation, i could explain it better in Greek...



anyways, it's a good thing that Dave has some ideas that u can try and eliminate the problem!!

[miller11386]

Yeah, Definitely NONE of that kind of surge.

You are talking about the more catostrophic type of surge... on boost.

I am referring to when a BOV does not actuate properly.

Both cause the same thing to happen. Air tries to evacuate the tubes through the turbo.

[shabby]

That's not surge, your hearing bov flutter, even the stock bpv does that.

[miller11386]

Ok, I pretty much eliminated the chance for a leak in any of the charge tubes or head gasket. I soaked the head gasket and every charge tube connection individually with starting fluid and did not see a change in the AFR. I verified that the test was valid by spraying some starting fluid in the stock airbox opening. The AFR went from 13.2 to the low 12's.

So I can pretty much assure that there is no leak in any of the charge tubes/ intercooler connections.

I still have not heard a definite if the mA readings on my O2 sensor is correct or not... does anyone have a log from a good car with the readings of the front o2 sensor? (bank 1 sensor 1)

[shabby]

Don't worry about any mA readings on the o2 sensor, if it wouldn't be correct the ecm would flash a code, and that .34 lbs/min maf reading at idle is normal.
You really need hptuners here, this could be fixed soooooo easily.

[miller11386]

Explain to me how it would be fixed so easily shabby? I have nothing to go on other than daves word at thos point. I have already had dave look at my Ecu and he was happy with it.

If you can explain to me how to I will go get it tomorrow. I am willing to do anythig just to be able to drive the car at this point. I have already spent too many hours working and letting the car sit

[miller11386]

And it has thrown o2 codes the whole time.  P2195

[shabby]

If your short term fuel trim is maxed out at a certain rpm/load cell you simply add that amount to the maf correction table, you can read all about it here on fuel trim tuning http://www.hptuners.com/forum/showthread.php?t=26756
Im sure Dave is familiar with this, its just that every car is different and the fuel trims could shift either way even if you have a similar mod. When baldturbofreak did my maf relocation pipe i had to add 30% to my maf correction table at the idle section of the table, on his car he added much less.

Here's a histogram from one of my recent logs, it shows the stft added to the ltft in each load/rpm cells, i simply copy the whole table and paste it into the maf correction table, flash and log again until it gets as close to zero as possible, that's all.

[miller11386]

Interesting.

So why would Dave want to swap intakes? Why wouldn't he just ask to bring my car back to him?

I would think if it was a quick fix he would do it at the mod meet that I have been toying with attending.....

[shabby]

Did you tell him that your stft is pegged at 30%? If not then he probably thinks its some kind of hardware issue rather than a tune issue.

[miller11386]

I read that to him and we did discuss it. I also have forwarded every log I've posted to him.
I had the logged hooked up at work and wee went through most of the pids on the logger. That's when he decided to send me an intake to try.... now im completely lost

[shabby]

Well lets see what the intake does first before going bonkers.

[miller11386]

I would assume Dave has good reason to try the intake first. He mentioned that it cleaned up another setup he did that was having issues similar to mine.

I am not saying you aren't correct shabby, and I am not saying Dave is not correct either. I just have no real experience with all of this, so I am going to rely on the people who know more than I do. (which is pretty much any tuner )

[Sol Asylum]

And it has thrown o2 codes the whole time.  P2195

was it throwing codes before the turbo swap or only after?

[miller11386]

Only after. My car has thrown one code in 35k miles and that was due to a fails evap purge solenoid. I think that was a p0435?

But no, I had no issues pre turbo swap.

[kennysabarese]

Any update? I know swapping your two O2 sensors worked and then you had more problems and came back to the meet.

What ended up happening?

[miller11386]

Ok,

So finally think we chased out the rest gremlins this time... there were several.

The CAI seemed to help the MAF read better and line up the fuel trims properly. Not exactly sure about the why part, other than the sensor cant keep up with the pulsations in the air going by (with the bigger turbos). So it tends to read improperly causing my short term fuel trims to be pegged at +29.7%

At the meet, Dave took the O2 sensors and swapped positions with my gauge's wide band. That helped the running rich issue that as being commanded from the primary O2 sensor. I have been watching my gauge (which is now behind the ecu's wideband) and I see that it can be a bit erratic at times. but it was mostly correct. Not really sure if this was an issue or not, but we decided to leave it in that orientation.


I think larger cause to the issue may have been the leak in the secondary O2 sensor. Many of you who were there know I almost had a heart attack in DC when I lost ALL boost pressure. Ihawk called up Ivy and we brought it back.

After a bit of time looking at the secondary o2 sensor, Dave noticed it was not cycling as it should, but was pegged to the lean position (around 20mV.. stoich is 500mv). He checked it against another car and his thought was either the sensor was bad or had a leak.

Sure enough when Dave put the car up, the O2 extender was cross-threaded and had got hot enough to melt the aluminum extender. We pulled the piece of exhaust and DBG was kind enough to weld a new bung in the pipe and fill the old torn up bung with weld. He was even artistic about it.

I drove all the way back to Ohio with a giant grin on my face car is running as it should... I even got 30.5 mpg with the AC on!

Thank you Kenny for helping me log the issue and thanks to Dave and the Rookie Mr. Burns to getting these issues solved.