We're Going Racing....!

[Don]

He's got lower gearing that the stock bike Dave ran the 11.50's with - That's why he has to shift into 5th

Don

[alimey4u2]

He's got lower gearing that the stock bike Dave ran the 11.50's with - That's why he has to shift into 5th

Don

Good job I put the caveat of not being an expert Don...

[EMS]

You would have to shift into fifth with stock gearing too. I never did a 1/4 mile run, but the contemporary tests of the 1979 CBX show a 1/4 mile best of 11.64 sec @117.94mph. 4th gear at 9,500 rpm is 116 mph and for best acceleration, you need to shift before that, at max hp, which is rated at 9,000 rpm.

[Ringnalda]

The gearing is still the same as set up for mid-ohio, so a top speed of about 125 I am guessing, so I do have to shift into 5th. I'm on a diet, as the CBX has lost more weight than I have at this point, running a total-loss ignition, no starter motor or alternator. It's a pretty light CBX. So we'll see how much weight we can shave off the rider/bike combo by next time. I agree with the launch comment, I just hate to hurt anything on the bike, a drawback of being an engineer. The front wheel did lift on this run, which had me going through the lights at 110mph and yes, this time I only used the clutch for the launch...! Being able to see the track was also a plus.

[daves79x]

With stock gearing, a good 1/4 mile run will have you in the mid-to-high 11s and just topping out in 4th gear. 4th will do 120mph just past redline. You're doing high 1-teens at the end of the 1/4. I always shifted into 5th just past the traps and coasted down from there.

More rpms are needed to launch. The bogging you hear in the video is costing 1/2 second. Run the rpms up to about 7500 and drop the hammer. Do not let off for any reason (unless you lose control). The CBX tends to walk sideways a bit, but get your feet on the pegs and use body english to correct and hammer second gear at redline. Run each gear to just past redline for the best times. That bike should do mid-11s pretty easily.

Dave

[Don]

You would have to shift into fifth with stock gearing too. I never did a 1/4 mile run, but the contemporary tests of the 1979 CBX show a 1/4 mile best of 11.64 sec @117.94mph. 4th gear at 9,500 rpm is 116 mph and for best acceleration, you need to shift before that, at max hp, which is rated at 9,000 rpm.

That's interesting - One would think that the factory rider (or whoever was doing the 'contemporary tests') would know how to get the best out of the bike . . . . yet Dave got 11.53 @ 118 on a box stock bike by not shifting into 5th and taking every gear a little past redline . . . .

My own experience (admittedly with cars and not bikes) has always been that the most effective shift points have much more to do with where in the RPM band you wind up in the next gear . . . . as opposed to where the max HP is achieved in the gear you're shifting out of - Frequently, running a little past redline puts you in a much 'sweeter spot' in the next gear than you would get if you shifted before redline - That probably accounts for Dave's better times

I'm sure most of Jan's problems are with trying to read the 1/2 inch long needle on his tacho ;)

I would think that with Sweeping's lower weight, her more free flowing exhaust and more modern tire coupled with the improved gear ratio that very low 11's would be possible . . . . something approaching redline in 5th gear. It would sure be EXCITING to see a 10.99 . . . . wouldn't it? - You'd have to have a very experienced rider no doubt

Don

[EMS]

You are correct, Don, you want to end up at max torque point in the next gear, when you shift up. But the problem is, with running past max hp, you are actually losing time. You are not accelerating anymore. You are gaining speed, beacuse you are increasing rpm, but at a lower rate than before.

I would think that the testers in 1979 who ran the bikes for the magazines were pretty skilled AND the bikes were in top shape.

[alimey4u2]

I would think that the testers in 1979 who ran the bikes for the magazines were pretty skilled AND the bikes were in top shape.

Light weight Pee Wee Gleason was the rider of choice, ( Jan you'll have to go on a strict diet of crack to come close... ) it was common practice to removed the mirrors & also pry the disc pads away from th discs. A few other tricks included beneficial atmospheric runs which later magazines adjusted for...

[Ringnalda]

Moving of calipers away from the discs will give a couple of interesting seconds at the end of the strip...! I think the wheels move nicely, no binding. This, I don't think is the main culprit for my 1/2 second astray. I think this is mostly still in the rider, and experience. I have only been down this track 4 times in total now; so I need more experience for sure.
The tacho has been replaced, so I can see the needle clearly in the red zone. I could not go for a second run last Friday because Robby took his first run just after me. I will not post his time just yet... Main thing was that he was smooth and concentrated on the right things. Then they told me I needed a rear light, so that was that. I have stuck a helmet safety light on the back so that is taken care of. This week it's wet here, so I'll be checking the bike oil, probably change it, also want to pull all the plugs to make sure the mixture is OK on all 6.

Oh yeah, MIRRORS??? There is no extra weight on this bike, only functional items. The ignition light doubles as the oil warning light. All is wired through the kill switch, which is the only switch in the loom. The oil light gets its ground from the oil pressure switch, so as soon as the engine starts all lights go out and the battery just feeds the OKI's. I will try some MarkTronics as soon as I get them. No headlight, no general wiring loom, no signals, no horn, no brake light, lightweight swing arm, Worx rear shocks, stock front shocks with racetech inserts, K&N air filters, even the Denco's don't weigh that much... Wheels are lighter than stock, I'll be drilling the footrest plates this winter.

Then there is about 20ft of locking wire; what does that weigh?

My diet is working but I'll never get down to the lightweight stature perhaps needed for 10.99; however I'll have fun trying. I want to be able to at least do better than a stock CBX so 11.63 is the next goal. May have to review the gearing to get there.

[daves79x]

Don is correct in his analysis of the real world of drag racing. For whatever reason, running into redline then shifting produced better times for me on a stock CBX. I ran a string of 11.50s one night. Apparently everything was perfect - weather, traction, my launches. Other nights I could run 11.70s easily. Back then I weighed 140 lbs - it makes a difference.

Cycle World tested the '79 CBX twice - once as a prototype in April of '78. That bike ran 11.64. They tested a production version again in January of '79 and that one ran an 11.36 at over 118mph. That bike made some serious horsepower.

All I'm saying is that about any stock '79 you picked back then would run 11.50s or 11.60s in the right hands. And for me, the described procedure is how I did it back then.

Dave

[EMS]

I know it is absolutely ridiculous to debate 3 to 5/10 of a second when this falls well into he differences produced by ambient conditions and rider behavior at the very time of the run.

But I am sure that professionals take all these little things into consideration, like shifting EXACTLY at the right time to not lose 1/100th of a second and I am also sure that the gearing is being changed so that the shifting points produce the optimum rpm drop.
And this is what I was wondering: If you shift a hair earlier and reach exactly top torque point to obtain maximum acceleration, you may have an advantage over revving it over redline.
I have one bike where this is extremely pronounced. I rev the bike up through the gears and actually well before red-line it feels like it almost stops accelerating, I shift up and drop the rpm and the thing virtually shoots foward. And it does that when shifting both into 4th and 5th gear. There is so much more torque available at the lower rpm point, it becomes almost mind-boggling.

[Mike Barone #123]

If weight was the only factor Jan............Robbie and you would be in the same lapsed time range on your CBX. The main reason you had a lower ET (my guess is alot lower) on the same X is because you have alot more experience on motorcycles than Robbie..... and CBXs in particular. Seat time/passes/experiences and along the way figure out the best setup for the bike will result in great progress in lowering your ETs at this early stage in my view....after which....weight and maybe attending a drag racing school considerations could into play....plus factors others have noted.

Sooooooooooooo the big Q issssss....what could Jans best time be on a stock CBX? One approach.....Dave....... tell us what you think your time would have been on your stock CBX when you raced if your weight was the same as Jans....say 40lbs more. With this we now benchmark with a rider combining Daves experience and Jans weight for the best stock CBX ET. From here on for a lower ET, Jan has to up his experience/skill beyond Daves...and/or...start getting away from stock to more cubic money/inches with his bike being non stock.

In saying all this I am more than willing to admit I never drag raced a motorcycle and I think I must be the only CBXer ever to lose every single rollon with another CBX over the last 30 years. However, I also know that on the same bike....a heavier guy with lots of seat time/experience can keep up or even pass thin guys with far less seat time/experience at track days or in the twisties....and my guess is this applies to drag racing also which takes alot more skill than rollons.

For those that were compelled to use carbon fiber or other means on a CBX as a means to save weight..... my thought on saving 5-10 pounds was to simply skip supper and the next days breakfast to prepare for the upcoming sport ride at rallies........it all worked out.......and truthfully I can say it now....I never skipped one meal.

Andddddddddd.....one final thought might be to have Dave come out of retirement and give your X a go....this way you reallly have a benchmark on close to or the best time your X will do.

No matter what Jan......keep going for it .....and giving us reports.

Mike

[daves79x]

Mike S.
All I know is that seat-of-the-pants feel of when to shift doesn't always result in the best ET. The clock doesn't lie. My best times (by up to .2 seconds) were gained by running into redline before shifting. You actually have no choice going from 1st to 2nd gear anyway - if you launched right you were into redline before you could shift. You do not want the rpms to drop below 7500 after any shift, and to do that you need to be close to 10 grand before the shift.

The difference between someone weighing 150 vs 200 (I'm not accusing anyone of weighing 200 - just theoretical) is pronounced at the dragstrip. If both were of equal ability (a very subjective thing) I'd say an 11.50 for the light guy would translate into at least 11.75 for the 200 lb guy. Weight is horsepower lost, as we all know. It'd be fun to get back to the strip again to play around.

Dave

[Don]

You are correct, Don, you want to end up at max torque point in the next gear, when you shift up. But the problem is, with running past max hp, you are actually losing time. You are not accelerating anymore. You are gaining speed, beacuse you are increasing rpm, but at a lower rate than before

Actually . . . . not

Max torque is at 8K and max horsepower is at 9K, but the difference between 3rd gear and 4th gear for example is 1300 RPM - So if you shift at max HP then you come in at 7700 RPM in the next gear, which costs you time. Counting the revs lost during the shift, it's going to be even lower than 7700 in actual practice

But - All theory aside, nothing speaks the truth like actual trap times. Dave's 11.53 is remarkable. If he had shifted to come in at exactly 8K in the next gear (using about 9400 for a shift point) he would find himself needing another gear about 50 to 75 feet from the traps. Any experienced drag racer will tell you you're losing time that you cannot make up shifting just before you go through the traps, so to avoid that and gain time, you either alter your gear ratio slightly . . . . or add another hundred or two to your shift points. Actual practice will prove to you that it's faster doing it that way . . . . a shift 50 feet before the traps is the kiss of death

My 'math' says that 9600 or 9700 would probably be optimal . . . . but if Dave says 10K works best, I sure wouldn't argue - At least not until I had an 11.52 slip in my back pocket ;)

Don

[EMS]

Actually . . . . not

Max torque is at 8K and max horsepower is at 9K, but the difference between 3rd gear and 4th gear for example is 1300 RPM - So if you shift at max HP then you come in at 7700 RPM in the next gear, which costs you time. Counting the revs lost during the shift, it's going to be even lower than 7700 in actual practice


Don

Well, then..the optimum shift point from 3rd to 4th would be 9,300 rpm, a hair before red-line, for maximum acceleration in 4th.
There is no doubt, that other factors than drag strip performance influenced the engineers' decision on how to select the gear ratios.
After all, we are talking a street bike here. Not a competition piece.