Safe Boost levels?

I've spent a long time watching these values. I could share some actual data, but my car is modified quite a bit, so comparison would be unequal.

Specified is what the ECU expects to see for the given operating parameters. If the actual value varies from the specified value too much, then the ECU recognizes that as a problem and attempts to correct it or throws a code, depending on which monitor you're looking at. Just about every sensor has a specified value (derived from a programmed MAP in the ECU) and an actual value, which is what the sensor is telling the ECU is actually happening.

My group 11 specified value maxes out at 1836. If you apply WOT from idle, this value will increase from around 1200 at 1000 RPMS to a full 1836 (or so) at 1600 RPMS. The maximum spec value varies for elevation and intake air temperature.

Most cars' actual values exceed the specified value when boost is first applied. The ECU then reduces boost to match the specified value. 2245 peak is not an unusual value, but maybe a bit higher than I'd suspect for a stock TDI. Are you chipped? Your sustained boost at WOT should wander closely around the spec value of 1800-1900.

As far as being safe with this boost at 4300 feet - well, I'm on my second turbo. I lug my car, and I think the car should handle the lugging. If I have to worry about the load at low RPMs, I don't enjoy my car as much. So I'm an advocate for turning down the turbo boost at low RPMs via the VNT-1 adjustment. But that's a personal opinion. And I still lug my car just like I ever did - almost as bad as my wife does.

2245 mbar is approximately 18.5 psi, depending on baseline absolute pressure. Running that much boost should be OK at altitude, as long as the revs are above 2,000 rpm.

You may want to look at the revised performance FAQ to get more information. A -1 VNT adjustment may be advisable in your situation.

Currently, I am running only the 205s. I pulled the performance chip out because the turbo was working too hard. This is an A4 TDI New Jetta currently with the stock VW programming. Injectors only with the 2.0 L MAF set at 4.4 to 4.6 on the injection quantity.

I'll retry logging some data and post it tonight. I think all I need is Ch. 11? This Ch. alone should give me 3 or 4 cycles a second? Will that be enough to show what's going on? I would like a chip update, when it gets released some day.

Currently, I would like to see if these 205s are already at my maximum safe limit at this higher altitude. If this were true, the chip update would not work for here! Hopefully, this will not turn out to be true though!

I have not touched the -1 VNT adjustment screw, because I do not want to damage the threads or their appearance. If someone were familiar with this locally, I might consider this with the chip update. Pending, if the update looks safe and promising for durability.

Here are the log files of Ch. 11. I cut and pasted parts I thought would be useful in analyzing my boost levels.

Engine speed RPM,Specified MAP Mbar,Actual MAP Mbar,Duty cycle %



1st, 2nd gear acceleration run from a complete stop.
903 1000 887 24.7
1470 1153 877 27.9
1974 1275 949 25.1
2100 1234 1153 35.1
2037 1193 1285 46.6
1827 1163 1275 44.6
1554 1122 1204 35.1
1806 1153 1122 33.9
1995 1173 1122 37.5
2163 1193 1153 40.2
2352 1265 1193 45.4
2583 1520 1326 39.8
2961 1601 1673 63.4
3444 1765 1856 65.7
4032 1816 2050 74.9
4515 1591 1897 76.1
4011 1081 1499 44.6

Cruising in 5th gear at about 70 MPH.
2415 1173 1173 43
2415 1173 1173 43
2415 1173 1173 43
2415 1173 1173 43
2415 1173 1173 43
2415 1173 1173 43
2415 1173 1173 43
2415 1183 1173 43
2415 1173 1173 43
2415 1173 1173 43
2415 1173 1173 43.4
2415 1173 1173 43
2415 1173 1173 43.8
2415 1173 1173 43

Stopped and just idling.
903 1000 898 24.7
903 1000 898 24.7
903 1000 898 24.7
903 1000 898 24.7
903 1000 898 24.7
Complete stop and accelerating in 1st, 2nd, 3rd and part of 4th gear. In 4th gear I hit a peak of 2333 Mbar actual reading.
903 1000 898 24.7
966 1051 898 24.7
1911 1448 908 37.1
2205 1479 1132 28.7
2142 1561 1550 44.2
1974 1601 1693 53
2247 1703 1693 51.4
2793 1846 1867 57.4
3423 1856 2152 73.7
4032 1856 2152 77.3
4536 1652 1897 81.3
4704 1183 1540 45
3906 1081 1408 44.6
3276 1612 1326 24.7
3003 1856 1816 57
3213 1856 2071 69.3
3465 1856 2213 76.5
3696 1856 2081 73.7
3906 1856 1918 73.3
4116 1836 1795 71.7
4305 1775 1734 71.7
4452 1714 1673 74.1
4578 1622 1540 66.5
3948 1081 1377 44.6
3318 1591 1285 63
3024 1856 1754 63.8
3129 1856 2122 73.3
3213 1856 2234 76.5
3318 1856 2050 70.1
3423 1856 1877 68.5
3507 1856 1826 67.3
3591 1856 1785 65.7
3675 1856 1765 65.3
3780 1856 1785 65.7
3843 1856 1795 65.7
3927 1856 1805 66.1
4011 1856 1816 66.9
4095 1846 1816 66.9
4179 1826 1826 68.1
4242 1805 1816 68.9
4305 1785 1795 69.3
4368 1754 1765 68.5
4410 1734 1703 68.5
4473 1703 1652 66.1
4515 1683 1622 64.5
4557 1642 1612 64.9
4116 1091 1520 44.6
3423 1540 1367 45
3297 1867 1785 61
3339 1867 2224 76.5
3381 1867 2224 75.3
3423 1856 1938 66.9
3444 1867 1795 64.9
3486 1856 1775 64.9
3528 1867 1785 65.3
3570 1867 1805 64.1
3612 1867 1816 64.9
3633 1867 1826 64.5
3675 1856 1836 65.3
3717 1867 1836 64.9
3759 1867 1846 64.9
3780 1867 1836 64.5
3822 1867 1836 65.3
3843 1867 1846 65.3
3885 1867 1846 65.3
3927 1867 1846 65.7
3948 1867 1846 65.7
3969 1867 1856 66.9
4011 1867 1846 65.7
4074 1846 1846 63.8
4074 1846 1856 66.1
4095 1846 1856 67.3
4116 1836 1856 67.3
4158 1826 1846 68.1
4179 1816 1836 67.7
4200 1816 1826 68.1
4242 1805 1805 67.3
4263 1805 1795 67.3
4284 1795 1795 68.1
4305 1785 1785 68.5
4326 1520 1765 68.1
3465 1061 1530 44.6
2709 1030 1346 43.8
3339 1867 1469 47
3339 1867 2162 79.3
3360 1867 2366 82.1
3381 1867 2030 66.1
3402 1867 1795 66.1
3402 1867 1754 64.1
3444 1867 1765 64.1
3444 1867 1785 63.8
3465 1867 1805 63.8
3486 1867 1816 63.8
3486 1867 1836 63.4
3507 1867 1846 63.8
3528 1867 1846 63.8
3528 1867 1856 63.8
3549 1867 1856 63.8

For the most part that peak did not last but a fraction of a second. Normally this does not occur. Ideas?

All the peak means is that the stock boost control system isn't very good at responding quickly to changing conditions. It's basically normal. The proposed solution to peak overboosts - mechanical boost controller in parallel with the stock N75 valve - works great on the wastegate turbos, hasn't been tested on the VNT yet. See TDIFAQ troubleshooting under "Fluctuation of boost pressure".

Using my Vag-com yesterday, I noticed my boost in channel 11 showed 2245 mbar peak on the actual MAP? Is this safe at 4300 feet above sea level?

What is stock boost in third gear on WOT?

I tried the third gear at 3,000 RPM MAF test. I found my car traveled about 50 MPH at this RPM. The boost was about 1130 or 1230 mbar from memory. I logged the data, but my laptop must have went into power saver mode. I did not find the data afterwards.

I mainly want to know, which boost levels in channel 11 do I need to look at? There was a specified and actual MAP value shown. Which one is for what?

How can I compare my data to others on an equal basis?

I did a search and only a couple people have reported their channel 11 data. I would like to see more values of what others are reporting for their turbo boost.

Thanks,

I tried the VNT minus twist. I can't stand the lag of the turbo now!

I think the boost controller will be the final solution. I put my performance chips back in. WOT throttle still has a lot of smoke. The stock chips don't smoke at all compared to the chips plus 205 injectors. I may turn up the Quantity adjuster to 5.0 to see if that clears up most of the WOT smoke. The timing is already mechanically advanced to the upper Bentley timing graph.

I look forward to somone giving more details on how to set up the boost controller. An actual example with part numbers etc.

Oldman? How about those part numbers for an (A4 ALH engine) such as your set up? Thanks in advance!

[ September 04, 2002, 14:04: Message edited by: BillW ]