March 2, 2012 - Dyno time!
Before the Targa, our dyno was down for an extended period so all of my tuning was done on the road. And in a car with this sort of power/weight ratio, that's pretty difficult to do. It doesn't spend much time in a particular rev range before leaping on to the next. The car was running really rich which is safer than running lean, but definitely not ideal. So this visit was overdue.
My goal wasn't to determine the maximum power, it was to get the fuel delivery calibrated a bit more intelligently. So I set the dyno up to hold the car at a given RPM. By working the throttle, I could then move the car through all of the load ranges at that engine RPM with lots of time to let the computer zero in on a good mixture. Then I moved on to the next RPM band 400 rpm higher, and do it again. From 2800 to 6000 rpm, it was a long and noisy procedure. By the end, however, I had a tuning map that was a pretty big step up from the hacked-up one I'd started with.
Heat was a bit of a problem. Obviously, holding an engine at 5000 rpm at full throttle against its will does make a bit of heat. The coolant and intake temps would rise over the course of one of my runs, making the numbers a bit less accurate. But still, it helped.
Of course, I did a power run at the end, just to find out. With a very hot engine, the car pulled over 350 hp at the wheels. Not quite the 400 we'd been quoted for the engine, but still pretty darn healthy. There might be a bit more in it when tuned by someone with more experience with these engines.
Thanks to the inopportune arrival of a bunch of snow, I haven't had the chance to feel what it's like on the road. With the leaner mixture, it should have better throttle response. I'm really looking forward to getting the car back down to sea level again.
tags: dyno, tuning |
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