Surging

[MrHeavyFoot]

So I've been chipped about a month and seem to be encountering some intermittient surging. Most of the threads I have read indicate that it mostly happens in the 3-4K RPM range, but mine is a little higher than that... just below 4 to around 5K. And, it's under full throttle, not half like many threads seem to say.

The other kinda strange thing is, it seems to happen more when the engine is really hot. I first noticed it autoxing. I've always let things cool down before turning off the engine, but once I started opening up the hood between runs, it seemed to happen a lot less. Then, going to Sask this past weekend, I would drop down to 4th to pass some cars and the surging would happen again.

2001 Jetta 1.8T, AWD engine code, Upsolute chip. Everything else in the engine bay/exhaust is stock.

I figure it is probably the N75 or diverter valve, but I haven't got a clue how to figure out which one. I thought the N75 valves on the old AWD's were suppose to be pretty good.

Is there any way to determine which valve is the likely culprit?

[thorin33]

Your surging sounds just like what I used to have when I first got Up'ed. I have an 2002 AWP 1.8T. From all the research I have done and with talking to Simon Lomas, I don't believe that changing the DV to a Forge or something similar will prove any better. Some tests have actually shown the stock DV to be better. I have been chipped for almost a year and am still running the stock DV.

I used to think that when the outside temperature was colder than I wouldn't surge as much. Anyway, long story short, I changed my N75 F to a C and my surging has pretty much gone away. It's pretty much impossible to get a C since it is an old part but there is the H (same as the ECS race version) and the J. I have read that the H sometime cause overboosting which results in limp mode. The J has had some good reviews. I think that you have the C version already. I have heard that switching to the F sometimes works. I have one if you want to try it. I'll be moving to Edmonton is a week and a half so let me know.

[MrHeavyFoot]

Thanx for the offer. I'd like to give the F a try, although the surging is fairly intermittent so it may be difficult to tell if it does any good. It didn't occur when I was performing vigorous test drives the first few days although it seems to be happening a little more often now.

Drop me a PM when you get into town.

[Fluidic Digital]

Hey Pat, I'm sure we can arrange some kind of testing method(s) when you drop into Calgary for your gauge install... all I know is that I've been running the "H" version N75 valve for a long time -- and well... I love it. I hold 16psi -- I think the "H" version accounts for the extra psi. :thumbsup:

Peter

[MrHeavyFoot]

Originally posted by Fluidic Digital
Hey Pat, I'm sure we can arrange some kind of testing method(s) when you drop into Calgary for your gauge install...
Peter

Cool.

Thanx Peter.

[Kor]

The N75 changes the whole boost curve, I would say that it is your best bet to combat a "surge" scenario. My J valve is very smooth. From what I have heard, everyone with a C, J or H has been fairly satisfied.

[MrHeavyFoot]

I've kinda assumed I had the C version. I'll have to go look to make sure. That's why I was kinda suprised when the surging began, because from what i heard, there wasn't a problem with the older AWD 1.8T's and the C valve.

[Kor]

I was under the impression that the "C" was exclusively from a Passat.

[thorin33]

Nope. The AWD 1.8T's all had the C I believe.

[Kor]

Are you sure its surging? Also do you have a boost gauge?

[MrHeavyFoot]

Originally posted by Kor
Are you sure its surging? Also do you have a boost gauge?

Reasonably sure. Foot to the floor and then it starts to feel like someone is pumping the brake at the same time. Boost gauge is on order (the group buy).

[Holksvagon]

I used to surge a little bitm, but now with the N75"H" No more problems. Seems to have a little more get up and go too.... Power seems really smooth

[thorin33]

Do you still want to try the N75 F? I am moving into town this weekend.

[MrHeavyFoot]

Hmmm... I've got a boost gauge coming in with the group buy. Maybe it would be a better idea to wait until that's installed before we start swapping valves.

I don't see the surging much in city driving anyway, since I don't really tromp on it all that much. More of an autox and highway thing.

So are you going to work at Matrikon?

[thorin33]

Yup...I start on Tuesday.

We can wait until you get your boost gauge.