I'm sure you already know this but this won't be an issue once you get your boost gauge installed since you'll be able to switch between modes at will. That being said, I usually drive a little and turn the car off at least once before I feel that I really am truly in the mode I selected w/ all the proper parameters. I have no true basis for this, but I believe the ECU still needs time to adapt after selecting a particular mode.

 

Yeah, #3 will no doubt not be a problem with the APR selectable setup, but still would like to know beforehand what the baseline is. Next time you're in the stock program (as I'm sure you just can't stand those performance tune options), let me know what you're running.

 

Ok -- Finally got a chance to do some data logging - see the plot below.
The stock values are from my car, the other is from a car running the APR 93 octane program. These were 3rd gear pulls starting from about 1300 rpm and 20mph (6MT). I did a bit of interpolating to make the 2 data sets correspond in RPM. Looks like boost built slightly differently at the beginning with my car (stock) spooling just a bit quicker vs. RPM.

These are from VAG-COM logging charge air pressure. This is in hPa, so I converted it to psi then subtracted 14.7 to get boost (this may be a little off since I didn't check if today's pressure was actually 14.7 psi, but we are here south of Houston at about 30 ft elevation, so ...)

 

^Very nice! Thx for posting this info.

 

Little more info:

For the APR 93 car, we also logged some WOT runs from low RPM up to the speed limit in each gear on the way back. On my old B5 I did some acceleration measurement long ago and it looked like the 1.8T didn't produce full torque in 1st or 2nd gears.

I kind of wondered if the quick increase in engine RPM - which meant a quick increase in airflow required - outpaced the turbo's ability to spool. So, these measurements were done to perhaps answer the same question on the B8.

The plot below shows, not so surprisingly, much quicker ramp-up in boost pressure in the higher gears, kind of lending credibility to my theory. The B8 likely isn't producing it's claimed 258 ft-lbs at 1500 RPM in anything but 6th gear driving up hill :-)

- 1st gear never gets to full boost (of course my car (stock) likely would have - 13 ish psi - I'll have to log that sometime...)
- 2nd gear reaches full boost at about 3800 rpm - just before starting down
- 3rd gear - full boost at about 2500 rpm

Of course this all kind of depends on what you call "full" boost for the APR 93. The 6th gear pull kind of makes me wonder if the target isn't 21.26 as in the 3rd gear pull data from above and the bumps to 22.5 are overshoots? I didn't log "specified" for this set to try to get the sample rate up - 1st gear was sparse even logging only boost and RPM - got about 4 samples/sec, or 2 RPM and 2 boost readings per sec.

If that's the case "full" APR boost is reached :
- 1st Gear = never
- 2nd Gear = 3500 rpm
- 3rd Gear = 2500 rpm
- 4th Gear = 2350 rpm
- 5th Gear = 2230 rpm
- 6th Gear = 2000 rpm

If I assume that stock is something like 13.5 psi (see above, the specified value for stock is kind of all over vs. APR which has a nice plateau at 21.26) and the ramp-up is similar (it seemed to be above) full stock boost would be reached :

- 1st Gear = 3300 rpm
- 2nd Gear = 2650 rpm
- 3rd Gear = 2075 rpm
- 4th Gear = 1950 rpm
- 5th Gear = 1850 rpm
- 6th Gear = 1750 rpm

Torque will be directly related to boost pressure right? So any 0-60 run suffers from a loss of torque relative to the published "max" in first gear? For a stock car would revving to 3300 RPM before dropping the clutch allow the engine to produce full boost or do you need 3300 RPM and the extra exhaust gas WOT would create vs 3300 with no load (low relative throttle setting) ?

 

Wow, you went all out on this. Really appreciate the data, well presented. No doubt, these plots will come in handy in the future.

I agree the data shows the stock ECU programming to be yielding 12-13 psi, while the APR93 tune produces somewhere around 21-22 psi. That's an impressive 8-10 psi increase in pressure from the same turbo. I can see now these new 2.0T engines are a whole new beast. Can't wait to take delivery in another month. That truly is an impressive performance increase from that size of turbo. Heck, the fact that Audi is now producing engines with 12-13 psi stock boost is quite an improvement, especially when compared to the previous 1.8T that came with 7-8 psi stock.

As for your questions at the end of your post... remember that compressor output (boost) is directly related to exhaust gas energy (both flow and load). This "energy" is what spins the exhaust turbine. So, no load = no boost. However, you also need sufficient exhaust gas flow (i.e. rpm under load, as an internal combustion engine is really just a variant of an air-compressor) to spin the turbine linked to the compressor. If you think of it from an exhaust gas energy standpoint, then you quickly realize there's no way to produce boost in neutral, regardless of rpm. However, for those running a tip (auto) tranny, one can produce pre-charge in the system for much improved launches by simply doing a break stand or using a tranny brake to create load. Or, for manual setups a tranny brake and launch controller setup would allow the same thing, right? Anyhow, before someone jumps in here and thinks they need to re-educate an old racer about launching a turbo powertrain, let's not forget you need to have a modified ECU program installed to build pre-charge in the first place. Can't do it with the stock programming and safety measures in place.

 

Just did a small amount of logging on my Stasis tuned car. I didn't have a chance to do a run as per the APR log above but did measure the max boost at about 21.2psi.

More to come in the next few days.

John.

 

from 13psi to 22psi? That's almost 2x.. isn't that a sure plan to blow something because it's now working too hard??

(I guess that's the chicken part of me that is afraid of getting the APR tune.. while my other part badly wants it)

 

Easy there, Trigger. If the tuning is developed carefully, using the correct approach, there is little chance for failure. A given turbo size can only produce so much boost. There's a limit. If the unit wasn't designed to make that much pressure, it wouldn't. Now having said that, you also need to know how to drive a car that's been modified to produce more engine output, or yes, you'll eventually fail something.

Do some research on the various tunes offered and how each produces increased hp and torque. You'll learn a lot about turbo-charged engines in the process. Once you have this knowledge, it'll be fairly easy to pick out the idiots from the reputable tuners.

 

I'm totally confident in the APR tune.. but you have to admit that a ~80% gain on boost is quite a bit.

Out of curiosity, how do you drive a car that's been modified? Are we talking about avoiding the basic stuff like dropping the clutch from 3k rpm and flooring it when the engine is cold? Or is there more to it?