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Graphical representation of Surging (ECS N75 with K04)

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Gambit

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Discussion starter · #1 ·
this is what surging looks like:
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this is full 3rd gear and partial 4th.
I'm not blaming the ECS valve for the surging but it is definetly more pronounced with it on there. Boost is also .2bar higher than with the F or C valves as promised. It is very interesting that if I do 1st -2nd -3rd -4th gear pulls without letting off the gas the surging is minimal and only in 4th gear, while if I set my car up for 3rd gear pull (get it up to ~3k in 3rd then slow it down to 2700 then floor it) it surges invariably. As if letting off the gas before flooring it causes the car to surge more. Anyone else have a log like this they would like to share?
 
#2 ·
Re: Graphical representation of Surging (Gambit)

hey man, I had these same symptoms with the stock F valve and putting that C mostly resolved it. I think flooring it from a low RPM in these cars is a bad idea because it does cause surging to be more pronounced. If you roll on boost progressively, the car runs smoother, accelerates harder and doesn't come on with such a punch as it does when you just floor it. My guess is that when you dump that much throttle with so low of an RPM, the wastegate slams shut and it spools so fast that overboost occurs because the ECU>N75>Wastegate communication is not fast enough to maintain control of the situation. It basically puts the whole system in a reactive mode "whoa that's too much, whoa not its not enough......" up until you shift and give it a break. If you roll on power smoothly though, the ECU>N75>Wastegate have time to deal with the spool trend and keep requesting more boost, applying fuel up until its peaked.
this is my *wild* guess
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[Modified by QkShift, 9:00 AM 8-23-2002]
 
Discussion starter · #3 ·
Re: Graphical representation of Surging (QkShift)

Wow - there for a second I thought that people were just ignoring me
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Thanks for the opinion man. I think that there's something else at play here because when I said earlier launching from 0 and going through the gears - I didn't mean gradually taking off (that also gives me surging) but rather punching it in 1st - then quick shift (no pun intended
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) to 2nd and so on - the surging is at a minimum in such situations. But if I'm cruising at 45 in 5th lets say and I just punch it - surging galore! Gradually increasing throttle can result in surge-free acceleration but it's very tricky.
Come on folks - more opinions please? Share your boost logs that show surging... 80 views and 1 response
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#5 ·
Re: Graphical representation of Surging (Gambit)

Yeah, but the difference is this: when you go from 0 and go through the gears, you don't get surging because the turbo is spooled the whole time. When you go from 1st to 2nd gear, you drop from 7k RPM to about 5500RPM, so you never get a chance to see surging because you are spooled to full boost the whole time. The only way you see surging is starting in 2nd or 3rd at just below spoolup RPM (2700) and then just floor it. Any scenario of going through the gears in a maximum acceleration run will not see RPM below 5k so you don't have time for the ECU>N75>Wastegate to get into that reactive mode at low RPM. And we know surging isn't really pronounced at high RPM so you won't see it.
 
#6 ·
Re: Graphical representation of Surging (smd3)

quote:[HR][/HR]looks a little funny, I thought during surging the N75 was making a wavy request. In your graph the request is stable, but the supply is wavy.
http://forums.vwvortex.com/zerothread?id=262994
check out about halfway down the first page. UKAUSSI posted a graph.[HR][/HR]​
Great point, but you are a little off, I know what you are getting at, but the requested boost doesn't change, it's still what is requested, but the N75 just can't regulateto acheive that request. The real pisser would be to see the N75 duty cycle during this situation, now that will tell us something...
 
#7 ·
Re: Graphical representation of Surging (Gambit)

This is exactly what I've been saying since day one! In a drag-race situation, sure, there is no surging because the engine is not really under load... but if you are going 50 mph in 4th, and punch it....BAM! the engine is under extreme load, therefore more boost is needed to bring it up to speed.....
A theory that I had is that the wastegate actuator on some cars may be too sensitive, like you pointed out, it "slams" shut, goes into a cycle of "Whoa! I got too much boost!", then pulls out on the wastegate, only to have too little boost, and the whole cycle starts over again, hence..SURGING!!
I like this thread
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people are finally starting to see what I see, I was beginning to think I was crazy or just got f'd up system
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#9 ·
Re: Graphical representation of Surging (gintaras)

Here is surging with an 'F' and then switching to a 'C' and increasing boost by switching UPsolute versions. 'C' still has a little surging but not noticable in the car.
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Here is a couple of charts showing N75 duty cycle. Note how the ECS w/UP has a similar curve up to 5000rpm as 'F' no chip does
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[Modified by UKAUSSI, 11:09 PM 8-23-2002]
 
Discussion starter · #10 ·
Re: Graphical representation of Surging (UKAUSSI)

Thank you very much for the responses!!! For a while there I felt rather ignored
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. Anyways - I have my OBD2 adapter and will do some logs tomorrow - if all goes well I'll be logging the Audi TT 225 turbo
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