01-00 "On The Road" with Luke Bogacki
Shifting on RPM...It’s About Time!
Let me begin by emphasizing how exciting an opportunity it is to be involved with Dragraceresults.com, Texas Raceway, and a handful of manufacturers with this ongoing testing project. As a method of quick introduction, my name is Luke Bogacki. I am a nineteen-year-old college student from Arlington, Texas. I have been involved in drag racing for as long as I can remember. From helping my father at the track, to racing Junior Dragsters, and eventually my involvement in Bogacki Motorsports, drag racing has been a huge part of my life. Currently, Bogacki Motorsports is a successful, professional racing entity. We enjoy a two-car team consisting of a 2000 model Cameron 4-link Dragster and a ‘76 Chevrolet Nova. We compete within the IHRA, B&M, and Southern Super Tens Series, racing over 40 weeks per year. We’ve enjoyed a good deal of success in recent seasons, including the 2000 IHRA Division 4 Quick Rod Championship, the 2000 American Drag News Super Pro Points Championship, the award of NHRA Division 4 E.T. Driver of the year, and numerous big money bracket racing triumphs. In addition to school and racing, I operate our family’s business, Texas Supercars. We’re mainly a mail-order parts house, although lately we’ve begun to do quite a bit of assembly, wiring, plumbing, and various jobs on several bracket and class cars locally.
But enough about me. This column will focus on one reason I believe our racing program has and will continue to be successful--Extensive on-track testing. Throughout the season, we rent out our local facility, Texas Raceway as often as three days each month. We’ll test everything from tire compounds to converter applications, from throttle stop setups to various temperature readings and their effect on performance. As the season goes on, we will be involved in testing several new products and experiment with combinations that we wouldn’t necessarily try on race day. Right now, however, everything is out of commission. Cars are at the paint shop. Motors are at Huntsville Engine and Performance for freshen-ups. Trannies are at Mr. Wendell’s Torque Delivery Systems warehouse for rebuilds, and converters are up at Bill Taylor Engineering for their yearly overhaul. So, for these first few columns, I’ll try to elaborate on a few things we’ve learned through this program last season.
The powerglide two speed transmission has long been accepted as the norm and at times the only competitive tranny in bracket racing. It makes sense: One gear change keeps things simple, and a tall low-gear set keeps from putting too much power to the tires off the line. For as long as we’ve had these two-speed automatics (or any transmission for that matter) we’ve shifted them by RPM. In pre-electronic days, this was done by hand in accordance to tachometer readout. For the past several years, this has been done electronically with either an air or electric operated shifter in classes where allowed. For the purposes of the remainder of this column, we will be speaking in terms of only classes in which these devices are allowed.
Recently, several index class racers (Super and Rod Classes) have gone to timer activated shifting. This is done with any standard timer-found within most modern delay boxes. Those who do not have a multi-timer output delay box can utilize a separate two-stage timer to activate the shift. Index racers have set this up to shift into high gear while the car is on the throttle stop-for two main reasons: 1.) The car kicks to wide-open throttle in high gear, controlling traction on most vehicles. 2.) The practice kills some ET (the amount varies greatly depending upon the combination), which allows higher powered cars to run less time in the throttle stop. This keeps the throttle stop timer ratio from getting too out-of-whack.
The drawbacks to this setup are heavily outweighed by the advantages in most situations, given an index-racing atmosphere. For one, throwing full power to a slow moving vehicle in high gear tends to try and lug down the motor. A big torque motor will overcome this, even with a 9” or 10” converter (contrary to popular belief), but a smaller motor will have problems. Our Nova, for example, is powered by a 377 sbc, and does not respond consistently to coming off the throttle stop in high gear. It all depends on the torque output vs. the weight of the vehicle. Torque converter stall and size has a lot less to do with it than we like to believe. Running this type of setup will, however, build a significant amount of transmission temperature, in comparison to a standard low to high shift at high RPM. We’ve heard a lot of stories about this act being hard on high gear clutches, but after a season of utilizing a similar setup in our Quick Rod combination, our ‘glides have shown very minimal wear.
I hope that bracket racers have not completely tuned out of this column to this point, because this is the audience I’m trying to reach. I just haven’t gotten their in a very timely manner. Contrary to popular belief, I think that shifting by time has its place in bracket racing (yes-even at wide-open throttle). For one, there are the obvious reasons of converter flash, tire spin, or RF interference triggering a rpm activated switch. This really can’t happen when shifting on a timer (except rf-but it’s more easily diagnosed). Plus, a timer gives added flexibility. On a slick track, or with a slightly overpowered car, you can set up a timer to shift the car very early in the run, kill some ET, and still run strong mph. We’ve utilized this tactic in both cars at certain events (usually in extreme conditions-either the dead of summer or the dead of winter). It’s amazing how much ET you can kill by shifting .8-1.00 in the run, and how much drivability and dialability can be gained.
Finally, and hear me out on this concept because I can’t necessarily prove it, is this. My thought is that even shifting at a standard rpm is more consistent when done on a timer. As an example, I can print out several runs from Autometer’s playback tachometer, and measure shift points. Let’s say I’m in the dragster, and I’m shifting on rpm at 7000. At the “peak” of the shift point over 5 runs, the time (from release of the transbrake) will very from 1.90 to 2.05 seconds. I may not even be able to see the change on my time slip necessarily, but I can track a slight loss of traction or converter slip that attributed to the variation. Now, if I make the same 5 runs, but shift on a timer at 2.00 seconds, the result is slightly different. Obviously, my peak rpm comes at the same time in each run. Now, however, my rpm will very from roughly 6975 to 7025. What’s the difference? Maybe there isn’t one. My thought, however, is that if the car is shifting at precisely the same point in time on each run, the gear change will make up for a minimal rpm variance, and my starting “high gear” rpm will be identical. So, in essence, I’ve made everything in my run to that point identical to the last run, assuming I’m at the same point on the track. Like I said, I can’t prove that it’s hands down better, but our testing has shown a slight advantage in shifting on the timer, even at times that are comparable to standard rpm activated shifts. This may seem trivial, but in a profession decided by ten-thousandths of a second, we need all the help we can get.
So, I know what you’re asking-how do I get started on timer activated shifting (at least, I’m guessing that’s what you’re thinking--if you’re still reading!). The biggest advantage you can have is a playback tachometer, preferably Autometer’s peak-valley shift catcher. This tach can be wired into the transbrake release (for testing purposes only--this is illegal at some sanctioned events, consult your rulebook), which will give an accurate time of shift. Once you have this number, it can be plugged into a shift timer and will be a great starting point. If you don’t have a playback tach, it can still be done, but it will take a day or two of trial and error to get the timer set up just right.
Now, here’s the trick part. You want to wire your car so that it will shift either on RPM or via TIMER, without having to rewire it each time you want to switch. This sounds simple, but the MSD rpm activated switch throws a ground signal to your shifter solenoid, while a timer output will throw a positive 12V power signal. So, a double-pole, double-throw switch is necessary to be able to enable either RPM or timer activated shifting at the flip of a switch. Wire the switch as shown below, be willing to experiment with your settings, and you’ll be one up on the competition this season!
Thanks for reading. Be sure to visit our links, and feel free to e-mail me with any questions, comments, or suggestions for future articles. Bogacki Motorsports is online at www.BogackiMotorsports.com, and you can e-mail me at Luke@BogackiMotorsports.com. Thanks for reading, and we hope to see you at a racetrack soon!
1490 Henry Brennan Drive
El Paso, TX 79936-6805
K&R Performance Engineering
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Titusville, FL 32796
Bill Taylor Engineering
2 Memphis Avenue
Mt. Pleasant, MS 38649
Mr. Wendell’s Torque Delivery Systems
7512 Bogart Drive
North Richland Hills, TX 76180
Cameron Race Cars
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Ft. Worth, TX 76117
Dedenbear Products Inc.
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Pleasant Hill, CA 94523-4601