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View Full Version : whats going on in these datalogs?



ModifiedA4
01-08-2007, 05:10 PM
during 3rd gear runs is always feel some good power at first then it seems to tail off around 4000 rpm...then i get a surge above 5000 rpm.

at first i thought it was in my head, but some old logs of boost from september show this. i happened to log block 115 (boost) and block 020 (timing correction factors) that day.

note on the boost log the ECU starts dialing back the requested...while it does this the CFs go down...then the ecu slowly dials the boost back up at high RPM and consequently the CFs rise.

whats making the ECU pull boost initially? any ideas?

(BTW this was a 6.44 sec CAPS run...not too shabby, but could be better)

http://www.modifieda4.com/images/ecu-logs/091906_block_115_6_44_caps.png
http://www.modifieda4.com/images/ecu-logs/091906_block_020_6_44_caps.png

SeanF
01-08-2007, 05:15 PM
i dont ever seem to get that much CF prior to 5000 where yours dips... and when i say that much i mean my #s are usually 0 until then...

but this is k03 experience....

your not really looking at a huge drop in requested boost...
are you sure thats not a normal requested boost curve? either way your not dropping in actual boost until it runs out of breath anyways...

i was under the impression that the ecu wouldnt pull boost, unless it would go into limp or cut the throttle possibly in your case...

beejohn
01-08-2007, 05:16 PM
a log of n75 duty cycle will really help you determine how much the less boost the ecu is requesting and where. can you get that?

maybe a 115/119 log together if the sample rate is high enough.

bassed
01-08-2007, 05:22 PM
a log of n75 duty cycle will really help you determine how much the less boost the ecu is requesting and where. can you get that?

maybe a 115/119 log together if the sample rate is high enough.

2nd I think a log of 115 and 119 together would help, but it seems like typical n75 issues to me. How long has that one been in and what n75 is it?

ModifiedA4
01-08-2007, 06:53 PM
thanks for the suggestions...i definately will log 115 and 119.

fyi, this is the stock N75 with 96K miles on it. so its old.

im planning on installing a new "J" this week :)

ModifiedA4
01-09-2007, 04:25 PM
ok here are the 117 and 119 logs:
http://www.modifieda4.com/images/ecu-logs/010907_block_115117_6_58_caps.png

Daft
01-10-2007, 10:09 AM
Yeah that seems very tyipcal of the N75C that many of us have in our cars from the factory. I had this same issue when I first got chipped and immediately swapped mine out for a "J" valve. That was in 2003, still running that same valve today.[up]

The N75 revisions that you can find essentially vary by the speed at which the duty cycle values are acted upon. The N75F and N75C tend to react extremely quickly to duty cycle. The N75J, N75H and N75K respond slower and in result provide a much smoother boost curve when the ECU is in control.

The only item to watch out for is boost spikes. Since this recation time is reduced, you often end up with a boost spike that is beyond the peak boost rating of the software. I found that the N75H was the worst in this case where you would go as much as 5psi beyond the chip spec for a very brief period and this usually caused timing to retard to compensate. The N75J was a happy medium for me as the spikes were about 1-2Psi at most. I have yet to own a N75K but, I've read in some posts and articles that the K valve is very similar to the J in characteristics.

EuroA4
01-10-2007, 11:13 AM
For those of us taking notes...which log is for dc? 117 or 119...I don't have the VAG with me right now.

Daft
01-10-2007, 11:27 AM
Column #3 of 119 is the Duty Cycle.

Here's a nice map of all the measuring blocks: http://www.ross-tech.com/vag-com/m_blocks/index.html

SeanF
01-10-2007, 12:59 PM
where can you get the J?

pn?

Daft
01-10-2007, 01:18 PM
Bought mine from here: http://www.worldimpex.com/parts/genuine-part-j-valve_117476.html

It was about $65 when I bought it so it has gone up a bit in price.

OEM P/N: 058 906 283J

Simply replace the J with the other letters to arrive at the other versions.

(ie. 058 906 283C is the stock unit)

Just for the records, the N75 J is from the 1991 Audi 200 Quattro.

dualaudi
01-10-2007, 10:15 PM
The only item to watch out for is boost spikes. Since this recation time is reduced, you often end up with a boost spike that is beyond the peak boost rating of the software. I found that the N75H was the worst in this case where you would go as much as 5psi beyond the chip spec for a very brief period and this usually caused timing to retard to compensate.

it's funny that you should say watch out for boost spikes.. from everything that i have read and (drove) the h valve is the one to get if you want more power (provided it doesnt throw you into limp mode in doing so...)

And the J valve is the one you want for your +2 psi of stable boost/power. is it wrong / harmful to run with the H-valve?

Daft
01-11-2007, 08:17 AM
is it wrong / harmful to run with the H-valve?

In a nutshell, there is no answer that will work for everyone. Some of the different N75 revisions are better with some chips than others. The H valve will infact cause a much greater boost spike than a J valve. Because of this, the people with chips in the 1.2-1.3bar range will end up hitting limp mode quite often.

Honestly, you would have to try the H valve to see if it is suitable for your chip. The J valve is a tad smoother and tends to be a happy medium between the stock C valve and the H valve. This is why more people can get away with it.

I currently run a 1.1bar chip with my J valve. I have also run my 1.2bar chip with it too but, I start to see lean conditions at the onset of boost due to the spike. If I had an adjustable FPR, I could balance that out a bit. So for me, I live with the 1.1bar chip and the J valve.

EuroA4
01-11-2007, 08:41 AM
Where's the cheapest place you've found the J valve for sale...I think I want to try this when my new injectors and software go in for the "hammer" file.

Daft
01-11-2007, 09:09 AM
Where's the cheapest place you've found the J valve for sale...I think I want to try this when my new injectors and software go in for the "hammer" file.


Scroll 3 posts up. That's where I found the cheapest price when I bought mine. It's $75 now so, I don't know whether that's still the "cheapest". You can try your local VW dealer or other places like www.germanautoparts.com or www.1stvwparts.com