This article was written by Eric A. Heddles and he has graciously allowed me to post it here. I think it is an excellent article and offers some insights in quarter mile times on a '94+ VFR750F.
This article is about drag racing my ' 97 VFR750F, and IMO this information applies to any bike. I would suggest several ideas to consider when drag racing.
- If you want to know how well a bike runs, take it to a REAL drag strip. Racing squids on the street won't tell you what it really runs. Everyone thinks they run what Sportrider or Cycle World does - WRONG!
- Most people will never match the numbers the magazines produce. They do it for a living and stick skinny folks on there with a lot of experience.
- The ET is most affected by how hard you launch the bike.
- The MPH is most affected by where you shift within the powerband.
The Launch
The VFR is a bike that can be launched very hard. I started out at 6-7000 and slide the clutch out somewhat quickly. I started out only running 1.9 seconds @ 60' times but got them down to 1.8's which is pretty good. If you are afraid of wheelies and roughly controlling them through first gear your 60' times will be around 2.1 seconds. So you can see that 0.3 seconds (an eternity at the end) can be wasted on a soft launch.
Shifting
There's a couple of ways to shift. The way I prefer to shift on a stock bike is to "blip" the throttle and shift when the tranny has no load. You can try this by running the bike up to 7000 - 8000 rpm at full throttle, roll off the throttle and at the same time toe the shifter into the next gear and then once the shifter moves into the next gear, pin the throttle again. You can get pretty quick and this isn't that hard on the clutch but this is hard on the tranny. Or you can use the clutch to varying degrees which is easier on the tranny and you probably won't miss any gears. Every once in awhile I don't roll off the throttle long enough and it won't unload the gears enough to shift it. I have an electric shifter (Dale Walker's Holeshot) but it isn't on the bike yet. My experience with the shifter is great and it helps about 0.2 seconds in the quarter mile.
Shift RPM and Results
Generally for most bikes, the shift is about 500 rpm after the peak horsepower for best results but the VFR doesn't like that. I have seen several tests that show the peak VFR horsepower is around 9800 rpm. I tried that range first and I'll list what happened.
I ran three (3) more times varying the shift points between 11,000 and 11,500. Finally I shifted into 2nd and 3rd @ 11,500 rpm and at 11,100 rpm after that and it eventually ran an 11.71 @ 115.1 mph. This may seem slow (and it is) but the humidity was around 97% and the pressure was 28.2". Temperature was around 65 degrees. I would expect 11.4s @ 118 mph with less humidity and a better barometer, which makes a big difference. My old '93 CBR900RR ran 10.9s @ 128 mph with bad air (such as when I was running the VFR) on down to 10.6s @ 133 mph with good air (no it wasn't stock).
- 1st run: 10,500 shift - 11.91 @ 114.1 mph. Not the greatest run
- 2nd run: 10,000 shift - 11.99 @ 113.6 mph. Too low, bike was struggling in the top gears
- 3rd run: 11,000 shift - 11.85 @ 114.5 mph.
- 4th run: 11,500 shift - 11.80 @ 114.7 mph. Seemed to be running out of breath on top
- 5th run: 11,200 shift - 11.82 @ 114.6 mph. Not as strong at the start, but great launch (1.82 60')
So these were the times that I ran and I'm usually the quickest on a bike with the group I ride (and weigh the least). The bike weighed 696 lbs. with me on it. I weigh around 160 lbs. and I wear full leathers like I do running CMRA races so it's closer to about 170 lbs. The VFR was totally stock with about 1200 miles on it. The clutch never slipped or gave out despite 7000 rpm dumps (this thing launches REALLY well).
An observation we have made about weight is that 15 lbs is worth roughly 0.1 seconds or 0.8 mph in the quarter mile. So losing 15 lbs would be unnoticeable unless the weight came from an exhaust system that gave you about 8 hp or some other positive gain!
Follow-up Performance NotesAfter the above post, Eric went back to the track and reported improved performance on his VFR750 after he had installed a TBR pipe and jet kit (130 mains, 3rd clip on the needles, 2.5 turns out on the pilot screws) and removed the air box snorkel on his VFR750.
The launch was stronger and the power of the bike was definitely in the mid-range since the mph gain was basically by the 1/8 mile mark.
Distance (feet) Previous Best (sec) TBR Pipe Best (sec) 60' 1.844 1.814 330' 4.951 4.730 1/8 mile 7.520 @ 95.15 mph 7.191 @ 99.73 mph 1000' 9.781 9.351 1/4 Mile 11.722 @ 115.06 11.21 @ 120.12
(personal VFR record)Summary
In my opinion, drag racing is a lot of fun and is more enjoyable at the drag strip than the street. There are not any cops, animals, idiot drivers, and there is an ambulance just in case. And you know without a doubt what the bike will run. I realize there are other bikes more suited for this, but try it. It's a blast.
In Houston, we run at Houston Raceway Park in Baytown, TX. Admission is $15 and you can run as many times as you want. An added bonus to running on Friday nights is that they only run time trials and don't post the times on the big light board at the end in case you're embarrassed easily. It's also a great place to calibrate your speedo to see how far it's off. It's also a cheaper dyno if you modify your bike and see what it does for you. It's better to feel horsepower numbers than read them.
Eric A. Heddles - '97 VFR750F
