alexs307
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« on: January 06, 2013, 03:17:48 PM »
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Hello, everyone. I have been searching this forum but found different opinions about my problem, and I couldn't take a final decision what to do best.
I am currently running a Z20LET engine on an Opel Speedster, the setup involving 630cc inj and GT3071 turbo, on standard ME1.5.5 Bosch electronics.
Engine is pulling a nice 425hp figure at 1.5bar boost, but I am having terrible problems when letting the engine idle after a full boost dyno run. Initially the engine seems to die, if I press a little bit the accelerator pedal while revs go down, I manage to make it idle, but the idle is lumpy. If I unplug the MAF connector, the idle goes back to normal. Stopping the engine, plugging the MAF back and starting the engine solves the problem, but this only lasts till next full boost run. I suspect the engine stopping is caused by the fact that I am running an SSQV BOV, but why is the idle still lumpy once I get the engine running at idle after a full boost run?
My suppose is that the turbo pressure is maxing out the 80mm Z20LEH MAF which I fitted ( of course linearising the new sensor by copying the map from original Z20LEH Astra VXR file, as original one was 70mm ) and this causes the MAF to go crazy after the huge airflow caused by boost. Unfortunately on last dyno I kept my eyes on AFR and boost gauges, so did not have the chance to see the actual MAF voltage, and the sensor failed. Tomorrow will replace the new sensor, but I am afraid that one single run at 1.5bar boost will break it again.
Fortunately, I have a 90mm MAF housing from EVOMS. Initially this came with a different sensor than the one I use in my 80mm MAF, so I have no clue about how linearisation map should look like and the info from the European providers of this intake is kept "inhouse".
Question is: what does fitting the 80mm sensor into the 90mm housing involve regarding linearisation? Will I have to multiply the values inside the map with the ratio between the squares of both sections, or just with the ratio of both diameters? Or this approach is far from being precise and I need testing and testing?
Can someone confirm that 2.7T has 90mm MAF housing? Because this way I can get a sensor and fit it, so I know the exact linearisation map for it. Maybe someone can tell me Bosch code of inner sensor from this MAF...
More than this, actual measurements I made show that inner diameter is 72mm for the 80mm MAF and 85mm for the 90mm MAF, so does the 2.7T S4 have same size regarding the MAF - 85mm?
Any other opinions about my lumpy idle after high boost runs?
Sorry for asking so many questions but I have reached a dead end and I need help from others more experienced than me.
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prj
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« Reply #1 on: January 06, 2013, 03:38:56 PM »
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Get rid of the BOV, it's just sticking open.
Fit a bypass valve.
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alexs307
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« Reply #2 on: January 07, 2013, 04:11:03 AM »
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I took the BOV apart today, cleaned it and greased it, it looks ok. It's not causing lumpy idle problems, I am almost sure.
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prj
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« Reply #3 on: January 07, 2013, 05:35:05 AM »
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I told you what your problem is.
Get rid of the BOV and fit a recirculating valve, it's not rocket science.
I don't even see the point of these things, besides making noise.
They don't open properly on lower-transients causing compressor surge, and cause the airflow to play pinball in your pipes, and if the spring is weak enough for them to open, then they just open in normal vacuum/idle, which is what is happening to you.
Unless the MAF is on the pressure side post-bov it is not going to work right.
And even then you are just masking the problem, which is sucking unfiltered air through the BOV into your engine.
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catbed
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« Reply #4 on: January 07, 2013, 06:40:14 AM »
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I told you what your problem is.
Get rid of the BOV and fit a recirculating valve, it's not rocket science.
I don't even see the point of these things, besides making noise.
They don't open properly on lower-transients causing compressor surge, and cause the airflow to play pinball in your pipes, and if the spring is weak enough for them to open, then they just open in normal vacuum/idle, which is what is happening to you.
Unless the MAF is on the pressure side post-bov it is not going to work right.
And even then you are just masking the problem, which is sucking unfiltered air through the BOV into your engine.
I have a tial 50mm BOV on my car and it is closed at idle. I do get minimal amounts of compressor surge while the valve is opening, but as soon as it opens there is no surge. The surge is present for maybe half a second. I am quite happy with it and have noticed no adverse effects, although I have ME7.5 with wideband primary o2. I have no interest in recirculating since I am MAFless, and I wanted to relocate the DV/BOV to the cold side piping right before the TB. |
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alexs307
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« Reply #5 on: January 07, 2013, 07:03:52 AM »
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Mine is also closed at idle. I got your point, still don't think this is the cause but will leave it there as I am going MAFLESS because I cannot get rid of the MAF issues, can't calibrate the sensor in the new housing and anyway I use this car for drag race only. Thanks for answering.
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prj
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« Reply #6 on: January 07, 2013, 07:33:07 AM »
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I have a tial 50mm BOV on my car and it is closed at idle. I do get minimal amounts of compressor surge while the valve is opening Which is 99% of the operating conditions on a street driven car. That's why recirculating valves are used. So you can use a soft spring, and have them open on idle with no adverse effects. |
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sweegie
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« Reply #7 on: January 07, 2013, 07:55:10 AM »
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I told you what your problem is.
Get rid of the BOV and fit a recirculating valve, it's not rocket science.
This man knows what he's talking about - might be worth trying the solution and have a car with a chance of running correctly, no? |
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mcgas001
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« Reply #8 on: January 07, 2013, 10:12:24 AM »
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Mine is also closed at idle. I got your point, still don't think this is the cause but will leave it there as I am going MAFLESS because I cannot get rid of the MAF issues, can't calibrate the sensor in the new housing and anyway I use this car for drag race only. Thanks for answering.
Why oh why do you think its a good idea to go mafless on ME ECU's and think that it will be a good idea? You are removing the ECU's primary load input... |
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alexs307
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« Reply #9 on: January 08, 2013, 02:46:07 AM »
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I know it's foolish to cancel ecu's primary load input because of many reasons exposed here on the forum, I read about it, it's not ok to fool the ecu, BUT:
1. I don't have a suitable MAF, in fact I have, but I am unable to linearise it and the method of increasing in percentage by ratio of new housing/old housing diameters squares does not work, so it is equal to not have a suitable MAF.
2. A solution will be to fit a larger MAF from VAG, but this means that I have to also find a connector for it, as Opel connector will not work, cut the original loom, etc
3. Last night I measured the car with no MAF, with the same file that pulled 425hp and 535Nm, new figures being 462hp and 590Nm. In fact I had to lower the values inside the file as torque is too much for my sachs clutch.
4. Car is only used for drag racing and weekend round-the-city trips, so it's not a daily use car.
5. I am tired of buying MAF's.
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SVSPORT
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« Reply #10 on: January 08, 2013, 05:43:14 AM »
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Do you have any maps (damos) for Z30LET ecu?
I can help you for the new linearization but for the beggining, you can use RS4 map.
Have you change the TEMIN (minimales TE),TEMINVA (minimales TE bei VA)maps?
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overspeed
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« Reply #11 on: January 08, 2013, 06:23:03 AM »
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Isn´t your idle too rich ? (see LTFT e LTFT)
when you make a pull on dyno and release the gas pedal the engine will decay revolutions with lambda system disable (no correction).
It happens very often with me when calibrating on 100% Ethanol with very big injectors... put a little more advance (torque reserve in idle) and play with TEMIN TEMINVA TUVB to see what happens
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prj
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« Reply #12 on: January 08, 2013, 06:58:39 AM »
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The problem is he has a post-maf BOV as I understand.
So of course it goes to crap after a WOT pull, since measured air is vented to atmosphere and it goes rich.
Also, with the BOV, I wonder if someone ever logged rlroh_w or raw MAF signal during low transients, when the valve does not open.
It is quite erratic ... huge zigzag.
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overspeed
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« Reply #13 on: January 08, 2013, 07:05:31 AM »
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I´m considering he veryfied BOV and it didn´t gone open after the pull.
As I said, when I beggin calibrating with big injectors and Ethanol there is a plenty of modifications to make idle well, and allways involve TUVB and TEMIN... sometimes because I use Ethanol there must be some "torque reserve" map modification
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Rabbid
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« Reply #14 on: January 08, 2013, 07:13:26 AM »
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Have you logged your duty cycle on that also?
What pressure are you running 3 bar or 3.3 bar? 3.3 bar only gives you 660cc from what I've seen duty is very high on 60lb's.
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