GrahamC230K
MB Enthusiast
- Joined
- Jul 14, 2002
- Messages
- 9,755
- Car
- Audi A3 & S4 quattro
It's along one, make sure you have a drink.
He he. Been at it again. Haven't done any mods yet and I'm on my 2nd Dyno session!
Wanted to clear up some of the bugging questions I had after my 1st experience -
www.mbclub.co.uk/forums/showthread....d.php?s=&threadid=500&perpage=15&pagenumber=1
So, today I wasted another 50 notes here:
www.g-force-motorsport.co.uk/rolling.html
This has to be the most hi-tech rolling road I have ever seen. The whole thing is housed in a air temperature controlled "cell". I was allowed in behind a viewing screen and the whole experience was amazing.
The car was strapped down, wired up and off we went. The size of the fan was rediculous - almost blew me over. With the bonnet down but not latched, it made it flap about like a weak piece of plastic!!
We did 4 power runs in total after calibration. All were the same apart from tenths of a HP. The runs were done in 3rd gear as the dyno was configured to read peak BHP at about 80mph.
With my ASR OFF (but this still brakes the wheels just does not cut engine power) it still flashed on the whole way through the runs however - relevance comes later. I'm sure I was not actually wheel spinning as the dyno is designed and has had 1000+ BHP cars on it, but the ASR certainly was kicking in.
So, to the charts.
1 - Showing the 166.8 BHP @ the wheels plotted against Supercharger Boost Pressure.
Now the Flywheel BHP is estimated to be 203.4 BHP. YES, this is estimated not measured. We have assumed a 18% transmission loss which is what the technician said is expected for a Front engine rear wheel drive car, such as a Mercedes or any German make. He said jap cars would be less as they just dont make the transmission drivetrain as heavy duty as the Germans! He advised after my prompting Autos would have about 7% more losses - about 25% in total. We used this assumption as my transmission losses measured rediculously high - giving a total 226BHP if you were to believe them. We think they were inflated as the ASR was kicking in giving an additional resistance which was not real. This possibly also explains the 218BHP figure from my previous session.
Note how BHP peaks and tails off, whilst boost pressure is still rising nicely? Can only be explained by a valve of some sort releasing pressure - perhaps controlled by ECU - that would be a nice one to tweak!
2. - BHP against air/fuel (Lammda sensor)
Apparently as you can see the fuel is relatively lean near peak BHP - this is where chips can exploit a few extra BHP.
3. - BHP against torque.
Now on the actual graph the curve is meaured in lb, not lb/ft but the torque curve shape is correct.
I have the equation if you want it, but this converts to 207 lb/ft torque.
I am happy with these results as even taking the worst case scenario with transmission losses I am still up on power without any mods. I have a much better understanding and am content.
As for now I am all dyno'd out as if nothing else its a bit costly, so hopefully I wont see my car on another one unless it gets really sick.
One thing I did learn: If you want to compare cars - Real wheel BHP is the only measure to concern with and you really need to use the same dyno too!
Any one still awake?
He he. Been at it again. Haven't done any mods yet and I'm on my 2nd Dyno session!
Wanted to clear up some of the bugging questions I had after my 1st experience -
www.mbclub.co.uk/forums/showthread....d.php?s=&threadid=500&perpage=15&pagenumber=1
So, today I wasted another 50 notes here:
www.g-force-motorsport.co.uk/rolling.html
This has to be the most hi-tech rolling road I have ever seen. The whole thing is housed in a air temperature controlled "cell". I was allowed in behind a viewing screen and the whole experience was amazing.
The car was strapped down, wired up and off we went. The size of the fan was rediculous - almost blew me over. With the bonnet down but not latched, it made it flap about like a weak piece of plastic!!
We did 4 power runs in total after calibration. All were the same apart from tenths of a HP. The runs were done in 3rd gear as the dyno was configured to read peak BHP at about 80mph.
With my ASR OFF (but this still brakes the wheels just does not cut engine power) it still flashed on the whole way through the runs however - relevance comes later. I'm sure I was not actually wheel spinning as the dyno is designed and has had 1000+ BHP cars on it, but the ASR certainly was kicking in.
So, to the charts.
1 - Showing the 166.8 BHP @ the wheels plotted against Supercharger Boost Pressure.
Now the Flywheel BHP is estimated to be 203.4 BHP. YES, this is estimated not measured. We have assumed a 18% transmission loss which is what the technician said is expected for a Front engine rear wheel drive car, such as a Mercedes or any German make. He said jap cars would be less as they just dont make the transmission drivetrain as heavy duty as the Germans! He advised after my prompting Autos would have about 7% more losses - about 25% in total. We used this assumption as my transmission losses measured rediculously high - giving a total 226BHP if you were to believe them. We think they were inflated as the ASR was kicking in giving an additional resistance which was not real. This possibly also explains the 218BHP figure from my previous session.
Note how BHP peaks and tails off, whilst boost pressure is still rising nicely? Can only be explained by a valve of some sort releasing pressure - perhaps controlled by ECU - that would be a nice one to tweak!
2. - BHP against air/fuel (Lammda sensor)
Apparently as you can see the fuel is relatively lean near peak BHP - this is where chips can exploit a few extra BHP.
3. - BHP against torque.
Now on the actual graph the curve is meaured in lb, not lb/ft but the torque curve shape is correct.
I have the equation if you want it, but this converts to 207 lb/ft torque.
I am happy with these results as even taking the worst case scenario with transmission losses I am still up on power without any mods. I have a much better understanding and am content.
As for now I am all dyno'd out as if nothing else its a bit costly, so hopefully I wont see my car on another one unless it gets really sick.
One thing I did learn: If you want to compare cars - Real wheel BHP is the only measure to concern with and you really need to use the same dyno too!
Any one still awake?
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