RS2 boost vs. temperature

[EspenW]

Unlike the S2/S4, the RS2 ECU does not decrease boost with decreasing ambient temps. This means that the ADU engine will produce way above 315hp/410nm in very low temps. I have used this very fact to show that the stock rods (when used in a separate coil engine like the ADU/ABY/AAN) will take a lot more hp/torque than what most people seem to realize. Porsche would not pick rods that would bend under conditions that the car would be bound to see in northern climates.

I had the chance to measure the boost in a bone stock RS2 the other day. Boost peaked at 1.4 bar for a second, then dropped to 1.3 bar and tapered off towards redline. Temperature was approx. 0 degrees celsius, so the engine developed approx. 340hp/450nm under these relatively mild conditions.
That was my first ride in a stock RS2. Felt slow. Compared to my own, Noggy blue wagon :mischeif:

[S2central.net]

Those Porsche ECU programmers are sneaky huh !

Totally backs up the factory info I have for max boost between 1.3 and 1.4bar - regardless of air temp. 1.4bar at 0 celsius makes more power than 1.4bar at 20 celsius - no argument here

The only compensation in RS2 factory program is that at altitudes higher than 2300m it drops max boost to 1.2-1.3bar to prevent overspinning the turbo.

Paul

[EspenW]

Yup, interesting to verify that the ECU doesn't compensate for temperature.
Also interesting to experience how you get used to power... When a 4.8 sec car feels like a turd, you realize that you are seriously spoiled I no longer blame the previous owner of my RS2 for somewhat deviating from the stock condition of the power plant
Will make some 2nd gear power runs runs with the Mr. Dyno acelerometer in that car and compare it to the curves generated by mine.

[Billman]

Mine had a chip and i think it had sometimes 0.2 bar lower OB when outside temp was under 4-5 Celcius. Can it be?

Also does someone has info of how a safe for the turbo boost curve in an RS2 chip would look like?

[Samppa]

At least the RS2 workshop manual says that even in ADU the boost is temperature related. During colder season boost gauge showed 1.1 - 1.2 bar and now when it's a bit warmer 1.3 - 1.4 bar.

[HPmuirt]

It is interesting that Porsche did not follow Audi’s decision to ignore the power increase at lower temps. I have read that Audi felt that the engine was comfortably within spec even at very low air temperatures.

Audi also did this with atmospheric pressure. Whilst other car companies lower boost to stop the turbo over-spinning, Audi reckon that the engine can take it and therefore stated in the marketing blurb that full power would always be available

So, the question is why is the RS2 ECU programmed differently to the S2? Possible answers include: -
- Porsche did not have the same sized go**** as Audi.
- Porsche knew something that Audi didn't about the engine or about turbos in general.
- Porsche thought that the extra 85BHP they had given the engine was pushing it to the limit already.

Cheers n

Si

[S2central.net]

Not quite right Si... ABY & AAN make accomodations for altitude and temperature adjustment so that it plays safe in thin air and reduces boost in cold air so as to give consistent ooomffffffff whatever the weather. COunter intuitive I know...

[mcandmar]

Prob a silly question, but where does it measure the ambient temp from?

[EspenW]

At least the RS2 workshop manual says that even in ADU the boost is temperature related. During colder season boost gauge showed 1.1 - 1.2 bar and now when it's a bit warmer 1.3 - 1.4 bar.

Hmm, at what page in the manual is this mentioned? This is the opposite of the info that Paul has, and does not rhyme with the fact that I just measured 1.4 bar at 0 deg C.
On page 36 of the manual, there is a description of how to test the turbocharger. According to the spec sheet, the turbo should boost 1.3-1.4 bar (at elevations below 1600m) at all charge temps listed (10-55deg C). Not sure if this is ambient or IAT, but regardless, it shows us that boost is not temperature dependent, like in the S4/S2. Knowing that the ADU will produce close to 400hp/500nm in extremely cold conditions (according to SAE dyno conversion factors), it shows us that Porsche were not worried about the engine blowing up, ie, it would take these power levels with a safety factor to spare. If this had not been the case, they would have modified the engine internals, just like they changed the intake, cam, airbox, intercooler, turbo, ECU, brakes, suspension, etc. for RS2 duty. People running 2.2bar and 620nm on a remapped but otherwise stock engine tells us the very same thing.

[UrS4boy]

Prob a silly question, but where does it measure the ambient temp from?

Do you have an outside temperature display? (I think YES).

I would think the sensor for that is the ambient temp source.

[UrS4boy]

Audi also did this with atmospheric pressure. Whilst other car companies lower boost to stop the turbo over-spinning, Audi reckon that the engine can take it and therefore stated in the marketing blurb that full power would always be available Si

Er, I think your information on the altitude sensor, is, well, WRONG:

http://forums.audiworld.com/s4s6/msgs/150037.phtml

The altitude sensor is called "switch - altitude correction". Its PN is 853 919 562 and shows up in the ATP section of ETKA as covering every turbo model from the early 1980`s to 2002 (and maybe beyond) including the RS2 (Refer to illustration 906-10 for the S2, UrS4, UrS6 and RS2).

Dave F.

[HPmuirt]

Not quite right Si... ABY & AAN make accomodations for altitude and temperature adjustment so that it plays safe in thin air and reduces boost in cold air so as to give consistent ooomffffffff whatever the weather. COunter intuitive I know...

Hi Paul,

I think I may have confused a few things here from the dim and distand past

I am sure that Audi tried to make sure that the S2 always performed at the same level irrespective of external conditions. I thought it was both temperature and pressure but I now read that it was only for temperature, as pressure is indeed used as a ECU boost control parameter.

I read some marketing blurb once which stated that the S2 will always generate max power in all conditions, probably meaning external temperatures. Is it not true that the S2 actually INCREASES max boost at higher intake temps, which other turbo cars don't do? This was the point about Audi believing in the engine spec etc.

Cheers n

Si

[S2central.net]

Yes Si - boost is INCREASED on ABY and AAN at high air temps to give the feeling of same performance regardless of the weather. I captured the boost profile for ABY onto S2central.net for all to see a long time ago.

There is ALTITUDE compensation made on ALL the 20VT engines so that boost is reduced at high altitude to prevent overspinning in thin air.

Samppa's post is plain wrong in comparison to factory info I have here - RS2 OFRM - and all the others.

UrS4boy is confusing things further too. The ECU has its own intake air temp sensor on the IM... This is wholly different to the ambient temp sensor used on the dashboard (indirectly in the case of climate-control equipped cars).

[UrS4boy]

UrS4boy is confusing things further too. The ECU has its own intake air temp sensor on the IM... This is wholly different to the ambient temp sensor used on the dashboard (indirectly in the case of climate-control equipped cars).

The question that was asked was about ambient temperature, which I answered correctly. If the question was about the intake air temp (IAT), then I would have answered as you have done, the G42 IAT sensor, P/N 034 905 379B. And I would have linked to:

http://forums.audiworld.com/s4s6/msgs/150047.phtml

which circles back to your website, I believe.

[Billman]

Yes Si - boost is INCREASED on ABY and AAN at high air temps to give the feeling of same performance regardless of the weather. I captured the boost profile for ABY onto S2central.net for all to see a long time ago.

There is ALTITUDE compensation made on ALL the 20VT engines so that boost is reduced at high altitude to prevent overspinning in thin air.

Samppa's post is plain wrong in comparison to factory info I have here - RS2 OFRM - and all the others.

UrS4boy is confusing things further too. The ECU has its own intake air temp sensor on the IM... This is wholly different to the ambient temp sensor used on the dashboard (indirectly in the case of climate-control equipped cars).

Paul, what is the lowest temp the IAT-Sensor is measuring?