I have an accurate Blitz electronic (analogue)boost guage fitted to my car and have been watching what the ECU is up to regarding how much boost it allows.
Bearing in mind I have the data from the bench dyno programming done on my engine so I know the parameters at all engine speeds on a full throttle run.
Running the car in say 3rd gear from 2000rpm to 7000rpm, the boost curve follows the data sheet curve. The car (~1500kg) does 100kph to 200kph in around 8 seconds so I am pretty confident that the full throttle dyno figures are accurate with over 500PS from 4750rpm to 6750rpm.
What the dyno figures do not explain is the "overboost" facility in the program. RS explained this to me before I had the motor built, but I didn't quite understand what they meant until now.
If say I am cruising part throttle at around 70mph (5000rpm)in 3rd gear then punch the throttle open, the boost will rise to around 1.25 bar and stay there for about 1.5 seconds before dropping back (all these numbers are not fixed as the ECU decides them on the fly presumably according to outside conditions as read by the various sensors)
This 1.25 bar for 1.5 seconds feels like a huge kick in the back which in fact it must be because it would represent at that point (ie 5000rpm)maybe (based on dyno data that I have) 780NM (570lb/ft) or 543hp if the boost held for 1.5 seconds then just before it drops there is 1.25 bar at 5500rpm which is maybe 595PS. This is the reason why RS engines feel so fast in day to day driving.
Just to explain my understanding of the overboost v a straight run from 2000rpm to 7000rpm, On the run up through the revs, the ECU is following the knock curve which is determined mainly by heat generated, so obviously by the time you have got to 5000rpm, the inlet air is getting pretty hot so the ECU will only allow a safe level of boost - this is where the "rated power" figures come from - When you punch the throttle after cruising, everything may be nice and cool hence the ECU allows the boost to climb to a much higher level and then starts to back it off as the revs climb/heat is generated/knock onset is detected.
I would think that all tt's would actually do this but at a lower level -has anyone else got an (accurate) boost guage and can concur. You Ruf guys ever seen this ?
<img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

 

your car makes ONLY this power because at the rated RM you have lower boost than what you have when you accelarate.
Because of the higher boost you have much more torque while accelaraating and that is what makes your car so much faster. you have only 522 hp at 5800 (or what ever) but you have more hp and torque when your car overboost.
Other have the same think. The car overboost for a few seconds. then teh boost goes back to normaö level.
Ther eis a trick if you want that your car always run higher boost and do not go back to the "normal" level. This will require high octane gas, cold wheather and sport or better no cats.
of course your DME should be programed for this.
Gemaballa and co also use overboost but their programing is not as good a sthe RS DME thats why your car is extremely fast.
BTW do you have the data for the 100-200 km/h test ? (like the time every 10 km/h or somethng similar)

Konstantin

 

Konstatin wrote:
your car makes ONLY this power because at the rated RM you have lower boost than what you have when you accelarate.
Because of the higher boost you have much more torque while accelaraating and that is what makes your car so much faster. you have only 522 hp at 5800 (or what ever) but you have more hp and torque when your car overboost

Er yeah I think that is what I meant

BTW do you have the data for the 100-200 km/h test ? (like the time every 10 km/h or somethng similar)

Sorry, I don't have the device which stores and prints the data.

 

Turbo Porsches using Motronic engine management all seem to do this. The 944 Turbo also does this. It's actually quite a unique way of producing really useable power. From my experience on the dyno with the 944 Turbo, the engine management system tries to hit the peak boost level, then dials it back based on knock and rpm.

If you look at this dyno chart, it shows the engine management system dialing back the boost after the initial peak, and then dialing it back up based on the output from the knock sensor and likely the rpm maps: <a href="http://www.novustelecom.net/~fkassam/dyno/paul002.jpg" target="_blank">http://www.novustelecom.net/~fkassam/dyno/paul002.jpg</a>

Here's the same car without the factory cycling valve controlling boost, notice that there is no dip in the midrange after the peak:

<a href="http://www.novustelecom.net/~fkassam/dyno/stever89paul.jpg" target="_blank">http://www.novustelecom.net/~fkassam/dyno/stever89paul.jpg</a>

The boost level was the same for both tests, however the last dyno chart had a bit better fuelling which is why the torque peak is higher.

I believe the RUF cars also use this method of boost management as I've noticed their cars tend to have a VERY strong mid-range, with a dip and then another surge towards redline.

I don't believe it is a time limited overboost, but rather based on knock activity and rpm. Perhaps the ECU experts can jump in here.

fc-racer

 

That sounds great and makes sense.
My brother has this in his 951 turbo s.

How much charges RS-Tuning for the DME and how much is your whole power-package to get the 522hp and 757NM and what does it include?

Mine is totally stock and for now i would be happy with something like the 450hp kit from porsche but with a more aggresive DME at lower revs.

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by fc-racer:
<strong>
I believe the RUF cars also use this method of boost management as I've noticed their cars tend to have a VERY strong mid-range, with a dip and then another surge towards redline.
fc-racer</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">fc, I think you are talking about the Ruf dyno plot here which is "rated" power & torque in other words with engine held at a constant 5000rpm, the inlet temp maybe 45degC, head temp X degC, air pressure XmmHG etc and the DME would allow say 0.9 bar to give 500hp this is how the power/torque plots are formed - what was a revelation to me was the higher than "rated" boost allowed when the throttle was punched in the mid range after cruising (with inlet air nice and cool) this extra boost would give higher than rated power spikes until the DME detected the onset of knock.

 

&lt;I don't believe it is a time limited overboost, but rather based on knock activity and rpm. Perhaps the ECU experts can jump in here.&gt;
it is boost VS rpm!
If the engine knocks then it is the same boost vs rpm but the engine reads from a different more conservative table.
the same for higher engine temp etc etc.

Konstantin

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Konstantin:
<strong> Ther eis a trick if you want that your car always run higher boost and do not go back to the "normal" level. This will require high octane gas, cold wheather and sport or better no cats.
of course your DME should be programed for this.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Is what your describing the 50HP software bug in the stock 993TT Motronic as shipped from Porsche?

 

I don't think this is programmed, its poor boost control. Some of the more modern boost control systems are extremely complex and can recognize the boost rising quickly and attempt to control the wastegate so that overboost does not occur. This is complex as any control of the wastegate before maximum boost is reached can slightly slow how quickly max boost can be reached.

The worst case would be you are at high revs already and slam the accelerator down - now you are going to get maximum revs+overboost and damage could easily be done to the engine.

Here is a good review that graphically shows the problem:

<a href="http://johnmonnin.netfirms.com/Boostcontrol.html" target="_blank">http://johnmonnin.netfirms.com/Boostcontrol.html</a>