Originally Posted by exdos
That's rather a roundabout way of doing something which you can do easily in a more direct way. Also, unless you are using a perfectly level and smooth road on a perfectly windless day then your calculations for power output will contain errors, whereas, the figure for VE gives you the efficiency of engine breathing in all conditions, and that's where your engine power comes from.
I've always been a huge fan of the OEM air-intake system on my MC, because I can see that it harnesses ram-effect. BUT, I could always see ways to improve the system and I've already identified at least 7 ways that the MC's OEM air-intake could be improved, and I've performed those mods and obtained very significant gains (circa 15% power increase). Not all of my ideas have been successful but I've only been able to determine which work and which don't from the data-logging. Clearly, BMW engineers have also thought that ram air-intake systems have merit and they have used this design on all it's M cars that have come along since the S50 MC was built in 1998, and each successive M car has a more improved and refined ram air-intake system, and your M3's intake is an improvement on what I have in my MC. It's the details in the system which makes all the difference to performance. I've owned my MC for more than 5 years now and I participate on a MC internet forum, and it never ceases to amaze me the number of owners who want to ditch the MC's OEM air-intake system and replace it with what they call a "Cold Air Intake" (CAI) - I'm sure that you know all about these things. Someone has recently produced such a CAI for the S54 MC and here is a photograph of it:
They have also gone to the trouble of getting the car dynoed with the CAI fitted and they use the graph below to prove that this CAI is producing gains:
In an earlier posting in this thread, I wrote: " Air starvation on many dynos, particularly with BMW's with ram-effect air intakes, occurs because the fans placed in front of the car on the static dyno, do NOT replicate the flow (pressure) of air passing in front of the car in "real world" on-the-road conditions, therefore, an engine with a ram-air intake system cannot replicate its true performance."
And YOU seem to agree with me on this because you have written: "A dyno fan will never replicate air flow at real world speeds, certainly not at 85 mph and up as who other than a Formula 1 team has access to that kind of wind tunnel?
The CAI in the photo above with "proven" gains claimed, as demonstrated by the dyno plot, will NOT
show an improvement over the OEM air intake in real world conditions. Static dynos produce artefacts when used with ram air-intakes. A datalogger can be bought for less than they are selling the CAI in the photo above. Static Dynos without suitable fans are useless for testing cars equipped with genuine ram air-intakes. I wonder why your M3 hasn't been fitted with a CAI like the one being sold for my MC?
As I think you have indicated there are many variables. There are ways to cheat the dyno, we all know that. Whether you lower tire pressure, reset the ecu, move the fan, don't give a cool down, these all affect it.
The reason I give credit to someone like RPI is because of the way they dyno and test. The same reason I believe Active Autowerke and Evosport when they post numbers. They simply have too much at stake to inflate numbers to where they can't be reproduced. These companies have spent decades in some cases building their reputation.
I believe items like the RPI scoops make far greater gains in the real world than they do on the dyno.
As for your comment regarding the GPS and incline, the newer boxes give you the % of incline or of the decline. You will know exactly where you stand. I believe the GPS is the easiest and quickest way to see the acceleration difference. No, I won't have volumetric efficiency and exact air flow numbers, but I don't have those now, and what I am primarily concerned with is the acceleration numbers (differs for each person and their goal with the car.)
Like I said, combine all sources ideally. I'm sure even dataloggers have variables that influence them.
I would like to see where you believe you increased efficiency, some things could potentially carry over to the E92. It would at least be valuable to see.