Normal Boost Pressure for 2871R Eliminator setup using Uni 630CC tune

[TheOperation]

Hello Guys

I have recently built up my B6 A4 with the following modifications;

Motor rebuilt (hone, new rings, rod bearings...etc)
Integrated engineering rods
ATP GT2871R
Kinetic Motorsports stock location turbo manifold.
Custom built 3" to 2" turbo inlet pipe adapter
Custom built 3" turbo inlet pipe
Forge 007 DV
VR6 Maf housing (stock maf)
Siemens 630CC injectors
Unitronic 630CC tune
034 motorsports drop in fuel pump
3" catless downpipe (stock exhaust)
Clutchmasters 240mm FX400
Stock SMIC
91 OCT

I have been doing some vagcom logs lately and have noticed that I am only getting 18.85 PSI of boost, the atmospheric pressure my map sensor is reading while the car is off is 1190 Mbar, peak boost is 2490 Mbar and requested peak boost is 2550 Mbar. Is it normal to be only getting 19PSI with a 630cc tune ? I would expect more than that, I clearly specified on my uni shipping form that my motor was built.

Your guys input would be greatly appreciated

The Operation

[Seerlah]

What is your elevation? And why is it you don't have a boost gauge?

[TheOperation]

I am a little picky when it comes to modifications to the interior of my car and haven't entirely found a boost gauge that I like yet. According to wikipedia the town in which I live in and have done most of my testing is -118 feet below sea level... if that even makes sense.

[John@Unitronic]

I believe we spoke on the phone earlier today regarding this. As I advised on the phone, your N75 valve should not be controlling the boost with our Big Turbo software. Rather, you should leave the N75 valve electronically plugged in, but not plumbed into the system. Route your Manual or Electronic boost controller into the system to allow that to control the boost. Our 630cc software requests 2550mbar, but allows the end user to control boost up to there. The reason for this is due to the high configurability of wastegate setups and thus the difference in WG pre-load. Feel free to email me directly at [email protected] if you have any further questions or concerns!

[Seerlah]

Going by the above, tune is set around 22psi requested. Sea level should really be 1013mbar (we normally just shave 1000mbar off the logs and go by that), and you said you are below that. Can you log to see what your mbar is at idle?

[TheOperation]

Mbar at idle is 1180 which I thought to be very high, Mbar with the key on is 1170. Ross Tech states that in order to accurately calculate boost, that you have to use the following formula;

(logged boost - atmospheric pressure) x 0.0145 which in my case comes out to be 19.14 PSI.

I may try finding someone that has a spare MAP sensor and giving theirs a try, it is very possible that mine is faulty because 1170 Mbar with the key turned on seems awfully high.

[Seerlah]

It is. So idle and with the car off is 1190mbar?

[TheOperation]

Yea key on car off 1170, car on and idling is 1180

[TheOperation]

Alright guys just a quick update;

I went to my fathers place of work today and tested both my car and his car which is also a b6 a4 1.8t. What I got for atmospheric pressure values is as follows;

My car:
Key on car off: 1170Mbar
Idling: 1180-1190 Mbar

His car:
Key on car off: 970Mbar
Idling: 980Mbar

Seems as though either my Map sensor is bad, dirty OR I have a vacuum leak, I am going to pull the sensor and clean it with MAF cleaner. If I put the sensor back in the car and I am still getting the same values I will swap sensors with my fathers car to eliminate the possibility of a vacuum leak. Funny thing is my car has always been plagued with this issue even a year ago when I had Uni Stg 2 and the stock ko3. I just never clued into why my boost has always been a tad low.

[Seerlah]

Swap MAP sensors and see if it is indeed the sensor.

[TheOperation]

Alright another update

Went and swapped the sensor from my fathers car to mine and found that the sensor in my car is fine as both snesors produce the same value (1170 Mbar) when put into my car. So either I have an ECU problem OR a wiring issue which I will test for tomorrow evening. If I dont find that I have a resistance problem in the wiring then I will swap my ecu into my fathers car and see what atmospheric pressure value I get.

[TheOperation]

Alright guys another update

I pulled the connector off of my map sensor and measured the voltages at the terminals on the connector I found the following;

Wire 1: 4.98 Volts
Wire 2: 5.61 Volts

Which indicates to me that there is a problem with my ECU, to alleviate this problem I am probably just going to buy an MBC or the Greddy Profec Spec II and keep my N75 valve plugged in but not plumbed through the system. This will eliminate the need for my Map sensor and negate the problems that I am having. I wonder how terrible the partial throttle acceleration would be with an MBC ? if anyone could chime in that has a similar setup to mine with an MBC that would be greatly appreciated.

[Seerlah]

I'm running the same turbo you have with a T3 .63 A/R configuration. OTS Eurodyne tune written for 21psi, MAFless, running it with the Turbo XS HPBC manual boost controller, n75 resistored, Brute rods, AEB pistons (AWM block), custom downpipe, custom smic, high flow fuel rail, blah blah blah. Thing is, I have a few gauges in my car so I can monitor how things are looking. The n75 is not just your boost controller, hit the device that will place you into limp mode if you are running lean. Since you don't have a WB gauge, you basically won't even know if you are running lean unless you are the type to log on occasion. And since you don't have a boost gauge and your MAP sensor is off, how do you plan on dialing in your boost controller?

But as to your inquiry of part throttle, I find it tolerable. It is part boost that can have the car act like a jerk, but this only happens really in either 1st or 2nd gear. I would take a guess that would not happen if I had a MAF and n75 parallel with my MBC. Which brings me onto the next thing. I do indeed plan on placing a MAF back into my vehicle. Maybe this summer when money permits it with a custom tune (Eurodyne Suite). Along with that, swapping out my 630cc Siemen injectors for Bosch EV14 630cc race units. People say it is like a night and day difference on just idle alone, let alone your car being happier at WOT.

And on a side note, you need to get rid of your stock SMIC asap. Have you had a chance to check your IATs? When your intercooler heat soaks (and it def does with that turbo), your ECU pulls timing, and robs you of a lot of power. Not to mention ignition timing pull is not a good thing.

[TheOperation]

Hey Seerlah

Thanks for the quick reply.

I bought a Forge unos manual boost controler off of a buddy of mine and will be getting an electronic autometer boost gauge this weekend as well so that ill be able to properly monitor boost and dial in my MBC.

As far as the logs go I have done countless logs on my AFR's, knock count, timing pull, IATs, boost...etc. All of which check out just fine in respect to the obvious limitations of my setup which mainly come from my SMIC. Also I typically have my netbook in my car which I run vagcom off of and quite frequently do logs. I definitely will be getting rid of my SMIC as soon as possible and will most likely be getting the CTS FMIC kit in about a months time and I am considering running water meth depending on how my ecu reacts to the new FMIC.