2002 Testing and Peru Pro
The drag race at the Shootout provided some an opportunity to get some data that we had never really gotten before. Unlike our chassis logger, which is a part of the car and so always available, logging data from the ECU requires that a laptop computer be sitting in the passenger seat.
We can't really do that in our normal races, as the car moves around too violently to make using the laptop practical - it's just too difficult to secure in place. But in a drag race, it's a different story. Unless something is very wrong, the car never moves laterally, and so the laptop can be used as a logging aid without worry of it flying around the cockpit.
Furthermore, after much fruitless frustration and teeth-gnashing trying to get an OEM-style oxygen sensor to work as a tuning aide, we bit the bullet and bought a Motec Professional Lambda Meter. This sensor reads air/fuel ratio to two decimal places from 9:1 to 22:1, and provides a temperature-corrected, 0-5V linear output that the GEMS ECU can read - and log.
We got it installed shortly before the Shootout, and so it was in place for our three passes. We lost the first log due to operator error, but the next two showed that we were running between 9.5:1 to 10.5:1 air/fuel pretty well across the rev range. This is more than just a little rich; in fact, I'm amazed we weren't laying a smokescreen all the way down the track.
Given that reducing the amount of fuel injected is just a few keystrokes away, and given too that there is some power to be found by getting the air/fuel to the proper 12.5:1, it behooved us to spend a day tuning. And thanks to our open exhaust, sneaking out onto a back road for a little full-throttle data gathering is not really an option anymore. So that meant we had to go to the dragstrip.
So out to the dragstrip we went, on a Saturday morning test and tune session. To spare the driveline, I'd ease the car out of the hole, and then lay into the throttle for the rest of the pass. After we crossed the finish line, I'd examine the log, and pull out a little more fuel and add a little more timing. Lather, rinse, repeat.
By the end of the day, we were starting to get into the ballpark, and the power was definitely coming up. But because of the soft launches, the times weren't getting any better. For the last pass of the day, I decided to throw caution to the wind and make a full pass.
St. Thomas Dragway has an incredible start line. I think the rubber on it has been continuously laid down since the 60's, and it is very, very grippy. So grippy, in fact, that we often don't get any wheelspin even when using our testing street tires. We lined up next to a warmed-over C5 Corvette, and staged.
Despite this being a test and tune, Mr Corvette was playing some staging games, and the frustrated starter dropped the lights as soon as he got staged. her rip. No wheelspin. Instead, the car launched so hard that it snapped the windshield wipers on, and then I ran down Mr C5, running a record 12.4 to his 12.8. Not bad. Mr C5 was not impressed, but the crowd sure was.
Once back at home, further analysis of the logs revealed something was leaking boost, and a pressure test indicated that the CBV was partially opening and bleeding down the manifold pressure to 18 PSI. This costs on the order of 80 HP, so it really needs to get fixed. MachV provided a TurboXS CBV, and I intended to install it after the Peru Pro. While I was at it, I also further smoothed out the ignition maps and tweaked the fuel maps a little too.
Then off to the Peru Pro.
We pulled the car off the trailer, and I was going to make a quick full-throttle pass through the (empty) paddock to verify that my map tweaking hadn't hurt anything. The car warmed up, I snuck down to the end of the paddock, went to full throttle, and BANG! CLANKCLANKCLANKCLANK.
Suddenly, I had a box full of neutrals, and the wheels would "ratchet" - roll forward a few feet, then lock, roll it backwards a little and it would unlock and roll a few more feet forward before it locked again. Clearly our day was done, and clearly something in the transmission let go.
So we pushed it onto the trailer (which with the wheels locking, was a bit of an adventure) and called TRE. Jon no longer has a trans removal facility, but he recommended Curless Auto Repair in Grand Rapids, just up the road from him. So we dragged the car up to Grand Rapids, and left the car in Chris's hands.
As it turned out, the gear on the OEM intermediate shaft failed, stripping all the teeth off the Quaife centre diff. This almost certainly happened on that big launch back in St. Thomas - that's what I get for trying to set records I guess. But between TRE, Curlis, Quaife, and ClutchMasters (who covered the bill on the Quaife rebuild) we got it all back together again in time for Nationals. Sadly though, there was no time to get the better CBV on, so we'd be running 18 PSI for the rest of the season. Hopefully that'll be enough for Nationals.