So I hit the dragstrip today with Mistro. First excuse right up front: it was hot out. Not 100 degrees waterfest style hot…but it was about 80 degrees and humidity was reasonably high according to dragtimes. Density altitude was up around 1000 feet by the time we got there (when temps were down around 70 degrees), and around 2000 when we left. So conditions sorta sucked for the dragstrip (for NA cars anyway) but Mistro is getting carbon cleaned and wanted to try a before after so I went with him to support him in his battle with the many 7 second @ 180 MPH domestics who were in town for proper race series tomorrow. While these weren’t awful conditions, we knew going in we were using today as a benchmark and that we wouldn’t be setting any records. Or would we? (No, we wouldn’t.)
One of the things I wanted to do was test the timing pull on 93 octane vs. 100 octane. So I did a bunch of passes on pump gas, then when there was a bracket event on, I logged the car on a flat road just outside the motorsports park, then threw in 10 litres of 100 octane, drove for 10 minutes, then logged again on that same road.
Two things stood out from the log:
1. my car was not restricting the throttle below 5250 RPM. This confirms that it’s temperature dependant (or maybe ‘engine torque’ dependant). I had logged in the cold and saw 52.5% throttle until 5250 RPM where it went to 100%. I logged in mild temperatures and saw 72% throttle until 5250 RPM when it went 100%. Now I have logged in 80+ degree temperatures with high humidity and with 110 celsius oil temperatures, and have seen 100% throttle right through the RPM range. I wish I could delete that frigging restriction in the cold weather (without needing a tune that is).
2. Race gas helped reduce timing pull…a lot. on 93 octane (a mix of 91 and 94 from two gas stations this week) my car logged timing pull of anywhere from 2-3 degrees early on to 5-6 in the mid-high RPMs and peaking at 9 degrees up near redline in one cylinder. On 100 octane (15 litres of 93 + 10 litres of 110) I found that the timing being pulled was greatly reduced…only pulling around 1-3 degrees even at redline. So race gas sure helps fight the heat a little bit for us…or whatever else is causing timing to be pulled at this point. It should be noted that 1-3 degrees pulled is what I found when I would log in the winter. My 4000-8000 RPM range was about 20 RPM/second faster on 100 octane vs. 93. For those who log a lot, you’ll know that’s a nice little pickup. Not groundbreaking, but enough to notice.
Jnaut wanted me to log that, so I did it for him.
The dragstrip results showed what we expected out of our cars, and Mistro’s car in particular. He dyno’d recently and put down a very solid 330 WHP or thereabouts. At the same dyno day a JHM tuned B7 S4 put down around 290 WHP and 295 WTQ. So his RS4 is doing well. Second of all, he and I did a 3rd gear pull with equal weight in the cars about 6 months ago, and we were near identical…and my car had just run 12.9 @ 107 so we know it was strong. My car later set the stock RS4 record with a run of 12.75 @ 108.3 in the spring, still bone stock (as it is now). Bottom line? His car is a good one with no weird performance problems. It has about 55,000 miles and has NEVER been carbon cleaned. Interesting huh?
So, we lined up a few times and produced some decent timeslips. My best of the day was a 12.92 @ 108.0 MPH with a 1.83 60 foot. That was my 1st run of the day…so that helps show the effect of heat etc. I really need JHM intake spacers. I went in my B7 S4 a few times and when it was warm, it didn’t see performance degradation as easily as my RS4 does on warm days. Anyway, I had a few good launches but as the day wore on, the car just couldn’t cool down and it got to the point where it would run 13.05-13.10 @ 106.5-107.5 over and over…just no faster. Unfortunately I didn’t get to run on race gas other than one pass immediately after logging the car and it was hot as shit. It was a 13.10 @ 106.something. I didn’t care, since I knew we were in the meat of the shitty DA by this time with the temp up around 80 or so.
Mistro’s car is a very nice black RS4 (not sure if Phantom or Brilliant). It is bone stock other than the ECS tuning H-pipe which does nothing for power but makes the car sound a little nicer. We did a video comparo as well, so I will get that added to the thread eventually. Mistro’s driving is solid and his RS4 driving has improved dramatically since we made a film of us all launching a few months back. he had just bought the car and had never launched it at that point. Today, he was ripping through gears and launching like a champ, cutting multiple 1.8 second sixty foot times despite the less than stellar conditions. It was his first time EVER at the dragstrip…so this was an impressive showing. Mistro’s best of the day was a 13.06 @ 107.6 MPH. That’s strong for a stock car on a hot day, and again I think this drives a stake through the heart of the carbon being a massive detriment to these cars. He was within 0.14 seconds of my car, and my car has the stock RS4 record. He was within 0.4 MPH as well. While he may have a bit more carbon than me, I don’t think it’s too bad. If carbon is really costing he and I about 20-40 whp as everyone claims, that would mean we’d both be good to go a couple of tenths quicker with a clean. We’ll see about that after he gets a clean done.
I also ran the pbox all day. Found out that the dragstrip at Cayuga is pretty flat. It’s downhill 9 feet from start to finish, so 0.6% downhill. Not bad. The pbox is also really accurate, reflecting the 1/4 times quite close to the timing equipment at the strip. Only off by maybe a tenth (usually less than a tenth) although MPH was off by 0.2-0.3 mph usually. Pretty cool to know.
I have some video that I will add. For now here is a pic we snapped while having a picnic together on a blanket in that field. Just kidding. We didn’t have a blanket.
http://audirevolution.net/addons/albums/images/712631221.jpg
