My first post will be about something I know about-Dynos. Like damn near all of the other sites I visit (primarily motorcycle related), I see on this one a lot of posts using data from dynos. As as dynomometer owner-operator, I want ot give my opinion on how this information should be used/translated.
Quick background... I joined this site yesterday, as I'm in the market for either a Cayman or an Exige, and to see some informative posts on this site, I needed to join. I own a Kawasaki dealership in SoCal, and have road raced motorcycles for 12 years. I actually did a stint in a 911 GT2 for a year, and won the POC's TTL with my bro once.
Anyway, I own a dyno (Dynojet 250i), and use it extensively tuning bikes (ours and customers)
OK
Dynomometers are only relative if you're using the same dyno to measure progress. The same dyno in different locations can read differently. Two different dynos (ie Factory Pro vs. Dynojet) will read power differently, and give totally different numbers. Factory Pro tends to read less than DJ's. Comparing #'s from two different dynos is unreliable. With the internet, I always see two dudes in different locations comparing their peak #'s. Invariably, the dude with the lower number always thinks he got a vehicle made on a Friday at 4:30pm. The proper way to use a dyno is to do a baseline, and then always use the exact same dyno to chart progress with mods. The peak # is irrelevant. The gain is the only relevant #. My dyno (DJ 250i) has a weather station on-board. I can do "back-to-backs" weeks apart, as the dyno will always correct. I can do a run today, get a number, and pull this run up two weeks from now, and get a different number as the dyno is showing me what the number would be in the current conditions. My trainer didn't tell me this, and I went a long time pulling my hair out over this, trying to figure out why the dyno was F-ing with me.
It's sometimes debated but IMO the smoothing number should always be at "5" (smoothest). The lower the number the more "spikey" the plot on the graph will be, and will give a more bogus reading. I've seen a difference of 10hp from the lowest smoothing number to the highest on a 170hp motorcycle. Here in the US, we use "SAE" correction. You want to make sure here, the dyno is set to "SAE". "DIN" and "PS" will give different numbers. It's common knowledge, but I've seen dyno charts with the incorrect correction factor being used, and also too low of a smoothing number.
One thing I can't figure out is the difference in the way you "Map" a car vs a bike. With a car, it seems you always overwrite the ECU (PCM, ECM, whatever you want to call it). Typically on a bike, you map a piece of hardware (Dynojet Power Commander for example) that goes inline and alters the signal coming from the ECU. There's a couple of exceptions as with certain bikes the factory makes "kit" ECU's and you program them directly. With cars, I've never seen an inline piece, and it seems like you need an act of congress to "map" your computer. With a bike, I can knock out a map in 20 minutes. I never do, as I map for 5 or 6 different throttle positions, and usually it takes me a couple of hours to get it as close to perfect as I can, but DJ has software that all the operator needs to do is plug in a target A/F (Air-Fuel ratio), follow direction from it, and it'll map the bike itself. Mind you, not every bike is the same, and you need to play with the AF to get the number that particular bike likes, and I like to map the bike myself anyway.
A major advantage an inline piece has over writing to the ECU directly is, with an inline piece, the ECU has no knowledge of what you're doing, and therefore neither does the over-zealous "warranty-canceling" factory. I'm told on my '07 Chev diesel, the factory can see if you've ever installed a programmer, regardless if you return the thing to stock before you bring it in for service. I would imagine everybody else, including Porsche, can see the same thing. Writing to the ECU directly (at least with kit ECU's), you have more parameters for adjustment (ignition advance, injector trim, secondary TB operation, rev-limit increase, pit lane speed limiter, etc...), but on a street-legal, warrantied vehicle, I'd rather lose these other options, and keep my warranty.
Thoughts, comments...?