Quote:
Originally posted by Unit 5302:
Again weight has absolutely NOTHING to do with engine performance. Aerodynamic drag has absolutely NOTHING to do with engine performance.
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Not to start a flame war here, but please don't throw out misinformation like this. We use chassis dynos to tune the whole car, not just the engine. (that's what engine dynos are for!) The primary purpose of any chassis dyno is to try to accurately simulate what's happening on the road or at the drag strip, which should include wind drag, especially with trap speeds in the 1/4 over 100mph.
Please do a quick search on the terms "Proving Ground Equation" and "Tractive Effort" and you will quickly see how the same exact engine in a Corvette sees a different load than it does in a truck. This change in loading to the motor dictates how much spark lead the engine will tolerate for a given a/f ratio.
I have seen the difference first hand many times. I did my homework as an engineer before buying any dyno and am confident in my choice. Unscrupulous dyno operators aside, the MD tends to read lower than a Dynojet because the engine is actually seeing the correct load for the street. I have seen the difference where changing the load (NOT the roller weight parameter in the software) allows the car to pull quicker on the dyne and tends to mask some tuning issues such as detonation. An unknowing tuner could easily call this a "safe" tune and let the car go to the track where it can potentially gaskets or worse.
As for the numbers, I will
gladly put a car that makes 400rwhp on my MD1750 up against any car that makes 400rwhp Dynojet in a race. I think my customers' trap speeds speak for themselves, and have yet to see anyone blow gaskets at the track after being "OK on the dyno" here.
Bottom line: Dynos are
tuning tools just like the wideband and the timing light. You want to know who's really faster, go to the track!
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Greg Banish
President,
Detroit Speedworks, Inc.
'93 LX Turbocharged Road Racer
'00 Bad-Ass F150