[iaknown]

So as some of you know I have been pulling every last hair out trying to solve my overboost issue. I think I finally have a solution.....

So to get everyone up to speed, I am running open exhaust. I thought this was the cause of my overboost but it turns out it wasn't (though it definitely makes it worse). I got a hold of the stock/SCR midpipe for the car and put it on and I was still overboosting. Probably just a psi or 2 but enough to set the "Boost Sensor Range" code while running Jarek's stage 2 tune. Running the stock midpipe just like most of you are told me something else was wrong on the car. With Jarek's help as well as the help of a few of the members on the forum I ruled everything out. Even replaced my boost sensor and wastegate solenoid (pressure converter), still no dice.

So I finally ended up opening up (porting) my wastegate in the car. Stock size is 7/16" and I've enlarged it to 9/16". I recommend using reamers in increments for ultimate control and even some "steering" of the hole. To go larger on the size you will need to get the flapper out of the way. To do this you will need to use a die grinder to remove some material behind the flapper so it can open up more and swing out of the way. Do NOT nick the flapper!

See before and after below. Had to remove the downpipe and engine mount again to do so but it appears to have come out ok (no holes ). After logging boost with no exhaust (downpipe only) I am right where I should be, so it made the difference I needed.

If you plan to run open exhaust you will probably need to do this to stay in the safe zone. Also, if you are running another tuner besides JR Auto's and you don't get codes with straight exhaust, your warning codes have probably been tuned out, you are still most likely overboosting, and probably slowly hurting your turbos.

It also sounds like another member will be presenting another solution (though a bit more involved) shortly .

[stevers314]

Excellent work!

[TDIwyse]

Excellent thread topic.

iaknown encouraged me to do more investigating on what my boost numbers were actually doing (thanks again). Turns out the Bav Tech data reported by the DDE was not "actual" boost numbers (although the Android Torque #'s were pretty close through most of the rpm range). So... some background from the 335d SCR Catalytic Converter thread

http://www.e90post.com/forums/showpo...4&postcount=92

Further testing today revealed some discrepancy to my previous description of 4th gear. And I took some video of gauge vs rpm in 3rd and 4th to better evaluate the readings. 4th gear at full fueling was actually peaking at ~37 psi at the 2800 rpm area and would then come down to ~34-35 psi and stayed there up to defueling at ~3900 rpm where I let off the skinny pedal. 3rd gear was pretty much as described previously.

The 4th gear data was concerning as it's off the compressor map ... so I decided to slip the DEF "mixer" back in place (#3 here http://www.realoem.com/bmw/showparts...15&hg=18&fg=10) and see what the extra restriction would do.

Well, it actually made a significant difference. Haven't video recorded this condition yet, but visually (and comparing the Torque data logs for 4th gear pulls) peak boost at the 2800 rpm point is down ~2-3 psi and sustained boost above 3000 rpm was down ~3-4 psi. So the Autometer gauge is now reading ~30-31 psi range from about 3000up to ~4000 rpm and then below 30 psi from 4000-4200 rpm. This is better as it puts things back on the compressor map.

Would be interested in comparisons from others with open exhausts to see if they see similar results with sticking the mixer back in place (which is pretty easy actually ... just need to unbolt the downpipe from the midpipe and there was enough flex in the downpipe section to move it enough to slip the mixer back in place).

Video of boost behavior with the open exhaust for a 3rd and 4th gear pulls can be seen here:


3rd

4th

So ... I'm trying an alternate approach to iaknowns mod, which involves an external wastegate. It's weighing in about the same as the EGR cooler. Finished getting it installed late yesterday (it's tight in there and took a lot of custom shaping/welding) but haven't had time to play with setting the response yet. Won't get to that until next week due to other responsibilities and time commitments. Will report back on findings.

[Mik325tds]

Very interesting thread topic, indeed!
I thought I saw boost pressures well over 50psi on the Torque App when accellerating in 6th gear. Is that normal?
I'm still stock except for the EGR block off.

[BB_cuda]

Clever idea. External exhaust manifold pressure regulator that bypasses into ...... wait for it.... the urea injector flange at bottom of down pipe.

[iaknown]

Beautiful work tdi. Looks like you even have some kind of access to change springs out

[iaknown]

Originally Posted by Mik325tds

Very interesting thread topic, indeed!
I thought I saw boost pressures well over 50psi on the Torque App when accellerating in 6th gear. Is that normal?
I'm still stock except for the EGR block off.

I can't remember if Torque includes barometric pressure (I sure hope so for your sake), but depending on your altitude it should read about 15 psi more.

[GreekboyD]

Next step, bigger turbo.

[iaknown]

Originally Posted by GreekboyD

Next step, bigger turbo.

That's right Jess

[TDIwyse]

Originally Posted by GreekboyD

Next step, bigger turbo.

"This is the last mod" ...

[TDIwyse]

Originally Posted by BB_cuda

Clever idea. External exhaust manifold pressure regulator that bypasses into ...... wait for it.... the urea injector flange at bottom of down pipe.

Yup, that's the idea. Expecting it to take some time to figure out if it's possible to control it. Kind of a gamble at this point ... if not I'll be doing iaknown's mod approach as he has data showing improvements to the over boost issue.

[TDIwyse]

Originally Posted by Mik325tds

Very interesting thread topic, indeed!
I thought I saw boost pressures well over 50psi on the Torque App when accellerating in 6th gear. Is that normal?
I'm still stock except for the EGR block off.

Something seems out of whack with your readings. Are you using the MAF based boost approach? If so it uses the MAF readings and what you enter for the vehicles engine size, volumetric efficiency, etc. for calculating a boost number. Using the correct engine size and VE should help you get the boost numbers to line up fairly well (it's still off some, but it's within a couple psi of the gauge through most of the operating range when I compare things). To do this you need to edit the vehicle profile.

And at least on the version of Torque I'm using "boost pressure" is reporting "gauge pressure", so it's not including the normal ~14.7 psi from atmosphere.

Hope that helps. 50psi would be deeply sub optimum if it's real.

[TDIwyse]

Originally Posted by iaknown

Beautiful work tdi. Looks like you even have some kind of access to change springs out

Thanks. I had help with the welding because ... I'm a hack when it comes to that. Should really take a class sometime.

The Turbosmart unit came with 35 psi springs (35 is the "cracking" pressure) and it's what's in there now. Road tested for ~6 hrs of driving yesterday and the mounting seems secure and functional. The dump pipe is routed to atmosphere at this point so I can get an audible feedback on when the gate opens up. It appears the gate is just starting to crack open under drive pressure at peak boost numbers.

Thinking when I get to playing with it I'll try T'ing off the vacuum line for the big turbo's wastegate and route that to the top of the external wastegate (top ports under vacuum helps open the spring) and that way the external wastegate would actually be in the control loop of the DDE ...

[iaknown]

Originally Posted by TDIwyse

Thanks. I had help with the welding because ... I'm a hack when it comes to that. Should really take a class sometime.

The Turbosmart unit came with 35 psi springs (35 is the "cracking" pressure) and it's what's in there now. Road tested for ~6 hrs of driving yesterday and the mounting seems secure and functional. The dump pipe is routed to atmosphere at this point so I can get an audible feedback on when the gate opens up. It appears the gate is just starting to crack open under drive pressure at peak boost numbers.

Thinking when I get to playing with it I'll try T'ing off the vacuum line for the big turbo's wastegate and route that to the top of the external wastegate (top ports under vacuum helps open the spring) and that way the external wastegate would actually be in the control loop of the DDE ...

If the external WG is cracking at peak boost it may very well be right where you need it. I would imagine it won't take much release to keep the boost at bay....but testing will certainly tell. Very interesting!

[dzlmoose]

Originally Posted by TDIwyse

Thanks. I had help with the welding because ... I'm a hack when it comes to that. Should really take a class sometime.

The Turbosmart unit came with 35 psi springs (35 is the "cracking" pressure) and it's what's in there now. Road tested for ~6 hrs of driving yesterday and the mounting seems secure and functional. The dump pipe is routed to atmosphere at this point so I can get an audible feedback on when the gate opens up. It appears the gate is just starting to crack open under drive pressure at peak boost numbers.

Thinking when I get to playing with it I'll try T'ing off the vacuum line for the big turbo's wastegate and route that to the top of the external wastegate (top ports under vacuum helps open the spring) and that way the external wastegate would actually be in the control loop of the DDE ...

[Mik325tds]

Originally Posted by TDIwyse

Something seems out of whack with your readings. Are you using the MAF based boost approach? If so it uses the MAF readings and what you enter for the vehicles engine size, volumetric efficiency, etc. for calculating a boost number. Using the correct engine size and VE should help you get the boost numbers to line up fairly well (it's still off some, but it's within a couple psi of the gauge through most of the operating range when I compare things). To do this you need to edit the vehicle profile.

And at least on the version of Torque I'm using "boost pressure" is reporting "gauge pressure", so it's not including the normal ~14.7 psi from atmosphere.

Hope that helps. 50psi would be deeply sub optimum if it's real.

That did help. Thanks. Changing to a new phone I forgot to set the vehicle profile. Torque does use the MAF calculation method. In preparation of my next project, I did a few logs (3rd gear pull and 6th gear full fueling) this afternoon with my original vehicle profile set and now the numbers are back where they belong:

[Puerto Rican 335d]

Sorry to hear this amigo IAKNOWN but I have yet to encounter your issues on my RENNtech flash and free flow exhaust. i was curious as to IF we use a blow off valve and i guess we do now seeing the pics

Tdi told some of my buddies that your car was cracking the 11 second barrier and they were mesmerized saying NO WAY I just laughed at them.

Last evening I made a believer out of a 993 owner i SHUT HIM UP!! then came back and swaggered jajaj it was priceless moment jajajaj

[TorqueAddict]

Axel, you will not be able to find out whether you have overboost or no, without logging your car. DTC's and limp mode have been probably coded out by lenny. The best way is to use the analogue boost gauge as TDi. That thing that you see in the pictures is 'wastegate' its not a BOV.

[Puerto Rican 335d]

Torque Im curious I hv Torque pro will check it out this week and post anything that comes out. But frankly I hv beat down my car and haven't had the issues IAKNOWN provided in the video my car is running great

[TorqueAddict]

Originally Posted by Puerto Rican 335d

Torque Im curious I hv Torque pro will check it out this week and post anything that comes out. But frankly I hv beat down my car and haven't had the issues IAKNOWN provided in the video my car is running great

As i mentioned, you won't notice anything. Car will run great, you will have gobs of power, but.... you might be slowly killing your turbos by overspooling them, and of course, you will have no codes.

[Puerto Rican 335d]

umm interesting Torque I will do the Torque pro read today, I guess Im fucked on this one LOL didn't know I might of been over spooling!! and of course codes wouldn't show until apparent damage to turbos is ensued.

[glitdi]

iaknown..
Did you pull the turbo to hog out the wastegate hole? or did you do it on the car? Rag to keep the metal out?
I don't remember seeing a procedure mentioned any where?