October 12, 2007 - Dyno time!
Now this was a frustrating day. Driving the car in to Flyin' Miata, I found I had a big vacuum leak. I'd folded the steel gasket between the two halves of the intake manifold while installing the VICS actuator. Thanks, Mazda, for making that one bolt so hard to access that I had to disassemble the intake! It's a good thing that FM keeps them in stock.
Once that was done, Jeremy at FM did a couple of pulls. He reported some pinging as the dyno was holding the car at 2000 rpm - a load situation that will never be seen in the real world, but still - and sorted that out, then blew coolant all over the shop. Turns out one of the fans had decided to stop working so the car got a bit hot and the radiator cap opened up. So, I spent some time fixing a remarkably recalcitrant wiring problem and also tracking down why the O2 sensor wasn't heating up properly.
It doesn't sound like much, but every time we had to stop it meant a couple of hours of delay before Jeremy was able to get back at the car. On top of that, it was obvious that the car needed a lot of dyno tuning, as the output was unspectacular. There's a big dip in the torque curve between 3000 and 4000 rpm, and the power tapers off dramatically just about 6000. Looking at a dyno chart of a similar engine, the bottom end is pretty good if you ignore a dip - but the top end prevents the big headline number from being very interesting. Because I needed the car to drive home, all the goofing around with other miscellaneous problems meant that we ran out of time. We established a baseline, that's all.
So what's wrong? Most likely the cam timing. This is an untested set of cams, and I'm not sure where they should be yet. The car will go back on the dyno shortly, and I'll do a lot of experimenting. I expect to pick up a fair bit of top end, hopefully without losing that nice spread of torque. I might also try another set of cams, the Webcam 505s that I'm running in my little 1.6 are quite impressive. Then it'll be time for a new, bigger header.
So, not the best day. But it's a start. I took the car for a spirited drive home last night, and it sure is fun to drive and seems awfully quick without any other cars around. Is it effective enough to keep up with some of the other cars at at the Targa? I don't know, that's why I need more from the engine, to give me a better tool to use!
tags: tuning, engine |
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