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Dang when you switched avatars I lost track of your progress.
Every post for the past 1+ years has been reviewed. I recall your statement, when "go fund me" was started. You planned to document the details here.
You are a man of your word...thanks for that.
BTW the effort is not lost to me. I S/C a Dodge Viper, later added W/M. Initially dyno tuned then street tuned. Got very familiar with tweaking timing and fuel while driving and logging.
While doing so encountered a few crotch rockets who wanted to play. When I think back that was the dumbest thing ever...on the street.
Anxiously waiting for more and please be safe during the process.
Wondered what happened to ya Rick.....
The GoFundme.....still sitting there. Haven't touched it. Particularly I am waiting for a personal/project benchmark that I am very close to and then going to offer refunds to the contributors and change the scope.
I am out in the country, my biggest worry is deer right now. There are two spots within 3 min of my house I can make hits, so that's nice. The Cayenne is getting louder and more beasty as we progress so I don't know how much longer until those spots get burnt.
The turbo's and sounds are loud, everyone want's to play lol.
I only race in Mexico.
Still tuning....it's the project that never ends so yeah, still here!
We are @ about 16lbs right now and I am fully impressed. It's quick. Spool and power delivery is damn near instant. I need to get some new video up.
Right now we are having an issue with boost osccillations or readings if you will. I am having trouble finding the cause or if it is even real. The Cayenne runs amazing. Just like factory but better. I don't get anything in the seat while driving that would lead me to believe everything is less than perfect.
Tial MVR44 wg's
.8 bar spring combo in the gates. (10.2psi)
With reference from both compressors going to the bottom of the gates the min boost I can run is 13.5psi.
With all reference disconnected from the gates running on spring only it will spike to 26psi no prob. Overboost protection kicks in and closes the throttle so I do not know the true limit on springs only.
With 40% DC on the gates thru the n75 I'm running around 15-16.
What this tells me is that my ex. manifold pressure is likely less than a 1:1, which is great. Am I wrong?
Right now we r debating whether this is a boost control(wg) issue or not. I am avoiding changing springs until I am sure because its an all day job.
I do need to get the upgraded spring in the Compressor bypass valves because there is a slight overlap between vacuum and boost when there isn't enough spring pressure to keep them closed during the switchover from vacuum to boost. Irregardless they get full manifold reference when in boost.
I am doing a lot of theorizing about what is happening and why but haven't figured it out yet. Tuning has stopped for now by my choice. Doesn't seem to be a boost control issue to me, we have control.
I still need to monitor fuel pressure on a run and see what that looks like though the tuner says fuel delivery looks good.
One of my other theory's is that because the compressor scroll is higher in pressure than the manifold by probably at least 2psi, maybe my CBV's are blowing open or fluttering @ full throttle? The CBV's get intake mani reference. If I have 15 in the mani, I probably have 17 @ the compressor (still need to verify). That would be 15 plus spring trying to hold the CBV shut and 17 trying to push it open. Maybe it reaches a point where its leaking at full throttle and allowing the compressors to surge a little? The stock CBV spring is not very stiff. I am waiting on the stiff springs now.
This is a 3rd gear pull. This is the problem. Notice how the red line(boost) gets jagged. Purple and green are maf values. Those lines seem to correlate with boost fluctuations, understandably.
This a pull with the n75 unplugged. Go's into overboost protection and closes the throttle to 50%. Seems to smooth the boost curve out.
Have you tried disconnecting your N75 with your reference pressure connected to the bottom of your Tials only? You should be almost exactly at 0.8 bar if that is what your springs combo is set to. That's how I run my 996TT, no N75, reference in the bottom of my Tials with 0.9 bar springs, runs exactly 0.9 bars on the gauge. There should be no oscillation with this set up, and no overboost.
If that's not happening in your case it's likely the wastegates.
Last edited by jeanmarcboilard; 11-18-2018 at 06:55 PM.
Have you tried disconnecting your N75 with your reference pressure connected to the bottom of your Tials only? You should be almost exactly at 0.8 bar if that is what your springs combo is set to. That's how I run my 996TT, no N75, reference in the bottom of my Tials with 0.9 bar springs, runs exactly 0.9 bars on the gauge. There should be no oscillation with this set up, and no overboost.
If that's not happening in your case it's likely the wastegates.
I get ~13.5'ish with the reference going to the bottom of the gates on a 10.2psi spring.
You might have a sticky or torn diaphragm in 1 of the wastegates. Notice how your purple MAF line drops off while the green line keeps going up. To me that seems to indicate that the wastegate on the purple side opened up more than the other side. Are they old? I had sticking wastegates on my 996 when I bought it, it was causing overboost.
Too bad removing the wastegates is such a long job on the Cayenne. It takes 2 minutes on a 911.
Have you tried disconnecting your N75 with your reference pressure connected to the bottom of your Tials only? You should be almost exactly at 0.8 bar if that is what your springs combo is set to. That's how I run my 996TT, no N75, reference in the bottom of my Tials with 0.9 bar springs, runs exactly 0.9 bars on the gauge. There should be no oscillation with this set up, and no overboost.
If that's not happening in your case it's likely the wastegates.
Yes sir, I have. With a .8 bar combo the min boost I can run is ~13.5 with the compressor reference going directly to the wastegates. With the reference unplugged running only on spring boost will hit 25~ before overboost kicks in and shuts the throttle, only tried that once, and real gentle. 0% duty cycle nets 13.5 and 40% was around 16. One thing I am going to be trying is playing with the spring in the CBV's or putting in some Forge or TS units. Like everything with Borg Warner the stuff is never released on time and right now the stiff spring is slated for backorder delivery the end of Dec. I have some more testing to do and I want to eliminate all the variables before I start swapping WG springs as it is a job. Even for me, and I engineered it all. Right now I know we are able to control the gates fine its just the resolution that is a problem.
I did shorten the signal lines as much as possible and now am running two N75's, one for each bank and very close to the back of the valve cover/firewall. They are wired in parallel. Graphs look a bit better but with 40% duty cycle I am now boosting ~19psi and throttle cut kicks in so I rolled back to the 20%DC file and am hitting ~15psi. That mod definitly made a difference in control and signal strength. 40%DC with one n75 for each bank. Back down to 20%DC and two n75's.
Great info in this thread - a question for jeanmarcboilard and J'sWorld. You guys mention disconnecting your N75 valve, or running two of them, and it got me messing around with mine, and I am blown away with the results. When I disconnect the top line to the valve (so the reference pressure line I believe) the car runs amazingly well, all the turbo grief I have had with it is gone! After doing some part replacement it now goes to 0.7 - 0.8 bar max on average with the N75 connected, and sometimes get a soft overboost (so no codes) which limits it to 0.4 bar. That goes away with time (10 minutes) or by resetting the adaptations with the VAGCOM.
With the top line disconnected it starts building boost even before 2K rpm, and the build curve is much faster, and it goes right to 0.9 - 1.0 and holds there! This has seriously made for +40 hp (just using Torque to measure) and like a second off the 0-60 time because the hp curve is much broader now.
I have been running it like this for about a month now, and I do get the 0.4 bar soft overboost once in a while still when I really wind it out, and logging the data shows some really high boost spikes (like 30 psi), but overall it just runs so much better, pulls so much stronger, I'd like to figure out why. The wastegates seem to open on there own perfectly at about 1.1 bar during acceleration, and everything vents fast (and loud) if I let up fast on the throttle.
So my question is, is this what people refer to as venting to atmosphere? Does the fact that I get so much increase from changing the reference pressure indicate some other problem? I supposedly have an ECU tune in there, which I am assuming is what lets me run at times +1.0 bar without throwing a code. Thanks.
Venting to atmosphere is done with aftermarket equipment. You can configure your intake to use aftermarket Blow Off Valves that vent to atmosphere instead of recycling the air back into the intake. You're likely hearing your BOV recycling more air now because of your higher boost pressure. Another type of atmospheric venting you can do is with aftermarket external wastegates, like Jworld has. Instead of routing exhaust gases around the turbine and into the exhaust system like regular turbos, external wastegates vent the excess exhaust out to atmosphere.
Be careful running with your N75 completely disconnected. When I said try disconnecting your N75 (also called timing valve or cycling valve), I meant by either disconnecting the wiring harness, which allows all your reference pressure to go to your wastegates through the N75, or disconnecting your reference line and connecting it directly to the wastegate line, bypassing the N75 altogether to help with troubleshooting the N75.
If you completely disconnect your reference line from your wastegates line, you have no boost control whatsoever ever. I doubt that your wastegates are opening at all because the exhaust pressure isn't high enough to open them. You're likely overboosting and your ECU is cutting your throttle to 50% or you're slightly letting off the throttle just enough to slow your turbos down to keep the boost around 1.1 without the ECU detecting overboost and cutting the throttle. You can log your throttle position when doing a wide open throttle pull to see what's happening. I'm curious if you still get full boost or that's when you get 0.4bar. I've seen my car still get full boost with the computer cutting the throttle back to 50% when my wastegates wouldn't open.
Last edited by jeanmarcboilard; 12-09-2018 at 12:14 PM.
Venting to atmosphere is done with aftermarket equipment. You can configure your intake to use aftermarket Blow Off Valves that vent to atmosphere instead of recycling the air back into the intake. You're likely hearing your BOV recycling more air now because of your higher boost pressure. Another type of atmospheric venting you can do is with aftermarket external wastegates, like Jworld has. Instead of routing exhaust gases around the turbine and into the exhaust system like regular turbos, external wastegates vent the excess exhaust out to atmosphere.
Be careful running with your N75 completely disconnected. When I said try disconnecting your N75 (also called timing valve or cycling valve), I meant by either disconnecting the wiring harness, which allows all your reference pressure to go to your wastegates through the N75, or disconnecting your reference line and connecting it directly to the wastegate line, bypassing the N75 altogether to help with troubleshooting the N75.
If you completely disconnect your reference line from your wastegates line, you have no boost control whatsoever ever. I doubt that your wastegates are opening at all because the exhaust pressure isn't high enough to open them. You're likely overboosting and your ECU is cutting your throttle to 50% or you're slightly letting off the throttle just enough to slow your turbos down to keep the boost around 1.1 without the ECU detecting overboost and cutting the throttle. You can log your throttle position when doing a wide open throttle pull to see what's happening. I'm curious if you still get full boost or that's when you get 0.4bar. I've seen my car still get full boost with the computer cutting the throttle back to 50% when my wastegates wouldn't open.
Thanks for the explanation - I did actually figure you meant electrically disconnect the N75; when I disconnected the connector boost immediately was limited to 0.4 bar and it threw the appropriate error code. I just wanted to keep trying things to figure out how this all worked!
Your comment on the throttle cut back sounds like something that also happened to me. 99% of the time I get the same safety mode kick in - boost is restricted to 0.4 bar, and that is both with and without the reference pressure line disconnected from the N75. Which implies that the N75 must still be able to cut the boost back even with the reference line disconnected. I also usually have Torque running, which shows my throttle position, and I have never seen it not give me %100 when I ask for it, even when it is holding me at 0.4 bar. But once when I was just cruising on the highway at a normal speed like 120 kph, maybe using a bit of the turbos to pass now and then, all of a sudden I had really weak throttle response, but still could get 1.0 bar boost. Since I just did my fuel pump a few weeks ago I had an oh %^&* moment, figuring I was loosing a pump and would be shut down again. I didn't even think to check the throttle position, I'd bet now that was what was going on. It keep going, weakly, and was fine 10 minutes later. So it sounds like I do get the throttle limiter, but not when winding it out.
So I do think that with the line off, the wastegates must be opening, not only because it can still hold at 0.4 bar at times, but also I have a cold air intake and I can clearly hear them, especially when I cut the throttle fast at peak boost. I have a busy couple of days but I will make some recordings of this when I get the chance. It really does seem to keep the max boost to a reasonable level still, but more important for my engine seems to be the improvement in the spool up time, which is really fast and strong.
So would the right way to do this be to get a manual boost controller and replace the N75 valve with that? This would bypass the ECU map which normally controls how fast the boost builds through the N75, and then just set the max on the controller to 1.1 for safety?
Thanks for the explanation - I did actually figure you meant electrically disconnect the N75; when I disconnected the connector boost immediately was limited to 0.4 bar and it threw the appropriate error code. I just wanted to keep trying things to figure out how this all worked!
Your comment on the throttle cut back sounds like something that also happened to me. 99% of the time I get the same safety mode kick in - boost is restricted to 0.4 bar, and that is both with and without the reference pressure line disconnected from the N75. Which implies that the N75 must still be able to cut the boost back even with the reference line disconnected. I also usually have Torque running, which shows my throttle position, and I have never seen it not give me %100 when I ask for it, even when it is holding me at 0.4 bar. But once when I was just cruising on the highway at a normal speed like 120 kph, maybe using a bit of the turbos to pass now and then, all of a sudden I had really weak throttle response, but still could get 1.0 bar boost. Since I just did my fuel pump a few weeks ago I had an oh %^&* moment, figuring I was loosing a pump and would be shut down again. I didn't even think to check the throttle position, I'd bet now that was what was going on. It keep going, weakly, and was fine 10 minutes later. So it sounds like I do get the throttle limiter, but not when winding it out.
So I do think that with the line off, the wastegates must be opening, not only because it can still hold at 0.4 bar at times, but also I have a cold air intake and I can clearly hear them, especially when I cut the throttle fast at peak boost. I have a busy couple of days but I will make some recordings of this when I get the chance. It really does seem to keep the max boost to a reasonable level still, but more important for my engine seems to be the improvement in the spool up time, which is really fast and strong.
So would the right way to do this be to get a manual boost controller and replace the N75 valve with that? This would bypass the ECU map which normally controls how fast the boost builds through the N75, and then just set the max on the controller to 1.1 for safety?
Check out https://s4wiki.com/wiki/Tuning for some info on how your Cayenne ECU works. Scroll down to the boost section first.
You need to be running the n75 hooked up and plugged in. Even on my build when I was running the stock file the throttle plate is what regulated the boost. In my case it was because my gates were sprung in such a fashion that even full reference wasn't able open the gates. The reason you get an increase in spool with your n75 unhooked is because it will no longer get boost reference to assist in opening the gate which in turn raises the cracking pressure. This is something that can be done with the boost PID's in the tuning and the correct way to do it. Who did your tune? Throttle position is overboost control, not the n75. Take a look @ the log I posted with my n75 unplugged. Still makes full boost with 1/2 throttle. The pressure inside the intake manifold is calculated by the ECU, only the pre throttle body boost is measured by the map/ecu.
This is how your n75 should be hooked up.
Boost control routing
When the wastegate opens is dictated by a combination of spring pressure, E-MAP, and boost reference. When you spool up you have spring pressure trying to hold the gates shut and boost reference combined with E-MAP trying to open them. In the de-energized state the n75 allows full boost reference to be applied to the actuators to help open the gates. To command more boost the ecu adds duty cycle to the n75 which in turn diverts a given amount of that boost reference from assisting the E-MAP to open the gates.
If you unplug the n75 the throttle should be closing to limit boost as you WILL go into limp mode. If you unhook the n75 the ECU doesn't know and will attempt to control boost by not regulating boost reference with the n75. When that doesn't work because you have the lines unhooked it go's into limp and uses the throttle. I would start by going over all of your vacuum/reference lines and testing the actuators. It is likely you have a mechanical problem but it could be in the tune as well.
Thanks - that wiki is pretty clear to not use a MBC and stick with the N75 and maps! I really wish I had the hardware to tinker with the ECU myself.
For my connections, everything is as in the pictures (thanks); and it is the top hose (when mounted in the car) that I disconnected, so the one that is labeled "vent to intake pre-turbo". My waste gates and boost reference are still connected. So the one disconnected is the ambient pressure reference line. From what I can find in wikis, I think this name is a bit of a misnomer, in that the boost pressure goes in the bottom and if the N75 is off, pressure goes directly to the waste gates, opening them (as you know, of course). But when the ECU pulls up the plunger, boost pressure is diverted into the top, atmospheric vent line (which I disconnected), thus bleeding of pressure and keeping the waste gates closed.
So disconnecting the top, atmospheric vent hose from the N75 shouldn't really do anything, unless it was restricted in some way, which would cause more pressure to be directed to the waste gates and they would open sooner. So it would seem that either by design or malfunction my pre-turbo vent line is too constricted, and when I disconnect it the N75 is bleeding pressure off "better". So that actually all makes sense, and explains the increased performance in my case. What I need to do now is see if the line to the pre-turbo intake (which isn't totally blocked) doesn't really flow as fast I would expect it to. I suppose this could also be a back pressure issue...
As you both emphasized, the ECU will use the throttle to control boost, and I think I have finally logged this happening. Just with Torque and not VCDS so lousy resolution, but I can see the throttle cutting back a fraction before the boost drops, and it is nothing I commanded. So now it becomes complicated, and could well be something to do with my ECU map. Which starts another mystery, because supposedly the Porsche dealership did my tune - mine is the 2004 CTT"S", which I know doesn't exist, but I was told that the original owner paid to have the CTT converted into an S, but since it doesn't have the E81 option I think all they did was load a ECU tune so it was like an S. Which would now maybe ring truer, because I don't get a real overboost code until I get spikes to like 2.8 bar.
Anyway thanks for all the info; if the boost is I really this sensitive to the vent line, this could also just be a problem in the N75 valve itself. Worth trying a new one.
After a lot of testing, elimination, and validation I think I may have found my problem. While changing my wastegate springs I noticed one of my turbine to manifold connections had little bit of soot on it. Before this I had never heard or smelled any kind of leaks. I moved on to changing the springs, tightened the vbands for the turbine housings and put it back together. After a trip to Austin and some driving for the holidays I got the dreaded ticking pft-pft-pft. Came home and hooked up a shop vac in reverse to the tailpipes to pressurize the system. With the small amount of pressure that a medium shop vac will make, what I found floored me! I have a huge leak! This will cause an imbalance in the E-MAP and drive pressure from side to side. When both wastegate's have the same spring pressure but the turbines see a different drive pressure that's a problem on a parallel setup like the Cayenne uses.
In the spirit of being transparent I am not surprised by this. On the EFR turbos the turbine inlet flange has a receiver groove to accept the manifold outlet flange's step/ fire ring....like this:
Matter of fact these are the exact manifold side flanges that I used.
When I welded them to the manifold's I had some warping which is not uncommon. Even though I clamped the flanges to the turbine housings while welding, the power of heat and stainless' affinity to warping overpowered the clamp. Normally one would just throw the flanges on a belt sander to square them back up. You can't do that with these because of the fire ring sticking out. My solution was a lot of hand filing and using a .5mm/ 2000 degree Topograph-Graffoil type gasket material to try and make them seal. Chances are they never were really sealed and I didn't notice because of the lack of soot and the loud volume of the turbo's and engine when running.
Either way my solution is going to be to weld the turbine housings directly to the manifold flanges. Taking them to a machinist to try and square them up I run the risk of changing the angles/geometry of the turbine outlet and wastegate connections as these are all v-band and sealing perfectly. My down-pipes are already built and they have to line up with both the turbine and wastegate. So the turbo position cannot change even a small amount at this point. I would have welded them together back when I put it together but I didn't have the down-pipes built or a bunch of other ancilliary stuff done so I needed to be able to position them in situ.
What is surprising to me is that I am fairly inclined and never would have imagined an exhaust leak could be so large without more evidence. The other side I think is leaking too but not nearly as much. The gasket wont last forever and as I start turning it up and E-MAP rises it will only get worse.
I worked about 5 hours today and got the engine 75% pulled. I need to address a few other things while the engine is out like valve cover gaskets. They are already seeping after only 12k miles. It's a **** poor design like most VW AG vehicles and I plan to use sealant on them this time.
I am going to install a Radium Fuel Pressure Damper as well because it is cheap insurance to hammering in the injector rails and can only help if anything. I have the big ID 1050x injectors and run a base pressure of 58 with a 1:1 rising rate. That's almost 90 lbs of fp with 30psi of boost that I plan to be running. Fuel rail pulsations are a real thing and can cause all sorts of strange problems. Most vehicles from the factory have FPD's and all my fuel system is comprised of rigid teflon lines that would only lend to this problem. For $100 I can eliminate this possibility of hammering and inexplicable tuning problems. A stock Cayenne has some sections of rubber fuel hose that would serve the same purpose as a FPD, expanding and contracting to absorb pulsations.
Since I have missed a bunch of documentation through this build I plan to show a few things I missed while the engine was out and I am open to request for pics!
11-18-2018, 10:21 AM
