Surging Again

[syth]

OK. Here's the story.

Went with the APR Stage 2 ECU upgrade. About a week after I installed the ECS N75 valve to help smooth out the power curve. It was awesome, smooth, fast, torque came on great and held well.

Then after about a day.....maybe less I started to get some surging around 5 PSI. It would fluctuate between 5 and 8 PSI. It would stop if I gave it more gass or if I let off. IT ONLY SURGED AT 5 PSI.

So i though..... leak ..... Replaced all three clamps, and tightened them good. Checked the TIP for leaks and found nothing. So, I removed the N75 and now I've got surging at 5 PSI, but it's much smaller. Only between 5-6 PSI. It stops if I give it some more and if I let off.

I've also noticed that it feels like the torque goes out around that time as well. But, more or less gas and it feels fine.

Wierdst thing is it dosen't do it all the time. Sometimes it runs just fine. No problems at all.

WTF? Any ideas?

[boostedJTi]

Does it do it when the car is cool or hot?

[syth]

Ahhhh. Great question. I'll try it tomorrow, but now that I think about it. It happens when the car is hot.

You think it might be heat soaked?

Pre / post detonation. Something like that?

[boostedJTi]

It could have something to do with the stage 2 reflash, still debating that issue, but seeing as how it only occurs when it's hot, may be the MAF sensor sending mixed signals to the N75 which causes the N75 to wig out, or the N75 is just shot and wigging out all on its own... I'm still mulling this one over in the head...

[syth]

Ok i see. But keep in mind it happens with out the N75. Just not as bad. I can still tell that there's a problem right around 5 PSI.

I'm going to talk to the guy at the APR dealer today. Just to see if he's seen this before. Being an APR dealer and all.

[pawcio]

it could be that your MAF sensor is just breaking or on its way out especially if you are losing torque. same thing happened to my friend's passat tdi and then it crapped out completely.

[prpltrck]

Does the MKV require the N75 valve, and what does it do?

[gtwombly]

well im pritty sure the MKV needs one too. The N75 valve controls the wastegate which controls the amount of exhaust going through the turbo ultimately controlling the amount of boost your running.

[boostedJTi]

Originally Posted by gtwombly

well im pritty sure the MKV needs one too. The N75 valve controls the wastegate which controls the amount of exhaust going through the turbo ultimately controlling the amount of boost your running.

hate to burst the bubble but you're wrong...

The n75 gets a signal from another n2xx. The n2xx gets it's signal from the maf. So the n2xx sends the boost levels to the ecu, which returns the signals to the n2xx, which forwards that info to the N75 which then regulates boost leaving the wastegate...

[gtwombly]

well i was kinda right.. just without all the n2xx bs. Thats some confusing **** boosted. What do you mean boost leaving the wastegate? I think I misunderstand what the wastegate actually does. Is it like an oversized bov?

[boostedJTi]

The wastegate is what regulates the boost, not a BOV or DV.

Time for turbo school kids, break out the notepads and start taking the notes, test on wed.

The job of a BOV is to release the built up pressure inside the intake chamber between shifts. If the pressure wasn't released then the turbo would be overwhelmed and continue to spool while you were shifting, leading to over boosting and eventually, severe internal engine damge.

The job of a DV or a recirculating BOV (both have the same job) is to take that extra pressure and instead of releasing it into the atmosphere, it releases it into intake side of things. This is where it gets confusing... Hey wait, didn't I just say the BOV did that? I did. But here's the catch, you have the intake manifold, and you have your intake. Your intake is what pulls the air into the turbo, and the manifold receives the cold air that is run through the intercooler. Back to the main topic. The DV puts the extra pressure that is en route to the intake manifold, into the intake that pulls air into the turbo... Consider this more of a pre spool. That extra air goes straight into the intake pipe and gets pushed right back into the turbo, sounds pretty cool right? Well it is, it has its advantages.

And now on to the wastegate. A wastegate is what regulates how much boost pressure the turbo actually produces. Throw out the electronics, all the ecu jazz, the n75 business, the n2xx and the MAF relay. Let's simplify everything. You have a turbo. You have a wastegate and you have a manual boost controller. Without the boost controller, your wastegate would still regulate boost pressure, but it would only regulate pressure based on the spring inside. The average wastegate spring allows for 12 psi of boost. So when a turbo hits 12 psi of boost, and continues to spool, that excess pressure is then regulated by the wastegate. The wastegate keeps the turbo from spooling passed the set spring rate to ensure turbo life and engine life. without a good spring or boost controller, a turbo can spool and spool and spool, not being regulated. Meaning the turbo can boost whatever it's efficiency range will support... Now let's throw a boost controller into the mix. The boost controller will sub in as what would be the N75 on a vw. The boost controller sets a different boost level, let's say 10 psi and the wastegate spring bleads off at 12 psi. When the turbo hits 10 psi, which happens to be our boost controllers set level, the wastegate then holds that boost level, and will not allow the turbo to spool past that. But what good is that? The boost controller (N75) is helping to control the wastegate.

Now let's get technical... The MAF sensor reads the boost level inside the intercooler, at the top right as it enters the intake piping to the manifold. If the MAF only reads 9psi at full throttle (in this case the motor is a stock AWP) it sends that reading to the ecu/n2xx. The n2xx then tells the N75 that the wastegate is not allowing the proper boost level so it tells the wastegate to allow the turbo to spool 12 psi and send that through the MAF. When it hits the MAF, it then relays that info to the ecu/n2xx which then relays to the N75. Once the N75 gets the proper reading it then tells the wastegate to hold at that pressure until the next shift where our DV or BOV does it's job. Then the process starts over...


Now let's say you have the ECS N75. It allows for more boost than the factory N75. Which means if the ecu/n2xx arnt reading the proper boost pressure from the MAF, it tells the wastegate to allow for more boost pressure which then corrects the problem...

[gtwombly]

thanks for that rediculous explination. Makes me want to go to tech school. Anyways i have a few questions. Im kinda confused on the DV still. The DV relieves excess pressure after the turbo. So its located RIGHT after the turbo or post intercooler? and when that pressure is relocated does it go back into the intake before the turbo? And im understanding the N75 stuff now but i have 2 more questions about it. Since the turbo can be boosting at 12psi and the MAF reads 9 psi after the air is pressed through the intercooler, does the car know that there is a pressure loss that great a. and b. why doesn't someone make a n75 that cranks it up more instead of buying a knew ecu? (I know that sounds noobish because i know you need more fuel too but can you explain that?)

[D.Light]

Many people get a dv relocator kit, to put the dv on the "cold" side of the intercooler so that colder air is routed back into the intake tract, and the new ecu changes something like 20+ aspects of the ecu (fueling, timing, boost, etc.)

[syth]

Problem solved. Turns out it had nothing to do with my N75, DV, or anything like that.

Bad ignition coil. #4 went out today. Car started missing and running like CRAP.

Replaced all the coils (just to be safe). Problem Solved. I had noticed a little idle bump here are there and though to myself once or twice,"My car should be faster than this."

Well, guess the coil was going south. Car runs AWESOME now. Crazy difference from before. Of course it could just be relative to what I was feeling today when the coil went out.

You guys are great; boosted, dlight. Thanks for the help all.

[D.Light]

Glad you got it fixed, was there any CEL on? And good thinking picking up 4 coil packs

[syth]

The CEL didn't come on until yesterday when then coil pack finally went. Threw a P0300 (Random Misfire), P0303 (Cylinder 3 Misfire), and a P0304 (Cylinder 4 Misfire) And it was blinking at me. I knew that wasn't good. Bad thing is I had to limp home through traffic.

Pulled the spark plug for #4 cylinder and it looked like poop. Cleaned it off good re-gapped all the plugs and she runs great now.

I'm in Houston, hurricane and all. So few people on the road this morning. Good time to test it out.

It's freakin' sweet.

I just wish I had the insight to know it was the packs before my car took a crap.

[syth]

Oh yeah. And now the surging makes sense. It was going into limp mode when the ECU started to notice a misfire. Just barely though. I'm guessing that's why it went away when I let off or gave it more gas. At around 5 PSI the Fuel/Air mix was just right to make it misfire. Less fuel - good spark. More fuel - good spark.

When I eased into it is when it started to misfire. Which is why it "surged" between 5 - 6/10 PSI. It was going into limp mode for s split second.

I think.

[D.Light]

Well now you know, just an FYI a flashing cel usually meaans misfire, which is gen. plugs or coil packs

[syth]

Oh.......... well damn.

[boostedJTi]

The limp mode makes sense, and the last thing I would have expected... I've honestly never seen a case like this occur, I guess it was because the coilpacks were never fully misfiring... Unique case, same conclusion... Just glad things are back to normal for ya

[05 GTi]

i wonder if thats what my car is doing. it hasnt thrown a code yet but surges every once in a while. syth, did your car do it the most in 2nd gear?

[boostedJTi]

thread revival haha

Coilpacks are strange... If you feel that is the issue just take the car to VW. There is a TSB on the coilpacks and they will have to replace them per the recall. If it doesn't fix it then you know it wasn't the issue...

[05 GTi]

Originally Posted by boostedJTi

thread revival haha

Coilpacks are strange... If you feel that is the issue just take the car to VW. There is a TSB on the coilpacks and they will have to replace them per the recall. If it doesn't fix it then you know it wasn't the issue...

i called them to see if my car has the recall and they said no. i sent you a pm boosted. check that out when you can.

[syth]

Update:

I'm still surging periodically. If I clear the ECU by disconnecting the batter for a while, it will run GREAT and not surge. Bu then after a while when it starts to settle in an learn from the sensors. It will tend to run a little less than awesome and surge. Always around 5 PSI or so. Give it more or less gas and it goes away.

I'm thinking it's a sensor or something. But I just don't have the cash to go around replacing sensors.

[boostedJTi]

n249 maybe... It relays info to the n75

[syth]

From what I've been reading that's the next place I'm going to go.

Has anyone had an experience with a faulty N249? Are there other signs I may be able to look for?

[boostedJTi]

There was a guy on the tex that bypassed his n249 as he had some issues with it, pretty sure he did a write up too.

As for signs... not really sure. I mean at this point you could try a throttle body alignment but I don't think it would help