How many times do you shift?

[Buick_58]

I am currently investigating the feasibility of electro-pneumatic shifting for our car and i was wondering how many times different teams shift per lap during the US enduro event?

Here in Aus, we have pretty tight slow tracks so our team found we only changed twice per lap which was on the straight.

However we are planing to head to Detroit in the future and from what ive read your tracks are much quicker allowing for more gear shifting.

Any info would be appreciated.

Dave C
Monash Uni

[Argus Tuft]

Maybe you should talk with the more experienced team members or your tech adviser
Argus

[Argus Tuft]

Hi David,
I would be very careful about making statements like "here in Aus we have tight slow tracks"
That is not the case. Sure we were constrained by Carrum Downs, but in the previous events, the tracks were faster and more open, and I suspect that will be the case again at Tailem Bend in December.
We all remember Kenny Hassler getting into it in top gear at Geelong in 2000 http://fsae.com/groupee_common/emoticons/icon_smile.gif
Argus

I'd rather have a bottle in front of me than a frontal lobotomy !

[Frank]

Thing is Argus, BOTH 2000 (too fast) and 2002 (WAY to slow) tracks WERE outside the specification of the rules.

2003 rules (5.7.4):
Average speeds should be 48 to 57 km/h
Top Speed should be 105 km/h

I've got data from Lang Lang (2001).
The 2001 track was close to the specs in the rules (just a touch slow with average speed 45 km/h, and top speed 95 km/h).

I only have a motec RPM graph (as opposed to the ideal.. a log of gearbox position), but i remember the track well, and with the graph i can "re-drive the lap" without any trouble. I especially remember my last 8 laps, cos we were running out of fuel. http://fsae.com/groupee_common/emoticons/icon_frown.gif "scaring the roos away"..Micheal Royce

I'd say most teams were between 15 and 20 changes per minute.

At Carrum in 2002 I think most teams were up around 20 changes per minute.

I think 500 changes per enduro (30 mins including driver change and warm-up time) would be conservative.(or have the stick shift available also)

We got plans to try an auto-shifter too, will have someone else check this data, and shall repost my thoughts later.

My knee-jerk reaction to an electro system is to measure just how much charge you have "up your sleeve" on the dyno, we did a very limited amount of this type of testing last year.. from memory we had about 5 amps available at 6000 rpm

Frank

"These cars feel great...SIDEWAYS"

[This message was edited by Frank on March 09, 2003 at 05:50 PM.]

[terc04]

to answer the original question: It depends.

On what???
your gearing
your power curve
your drivers preference

The FSAE endurance course is fairly open because the corner workers would have a hard time picking up the same cones all day in an ultra tight section of the course. They have it bad enough already. This means that if you have a wide powerband and well placed gearing you may not need to shift but a time or two per lap. Last year we had a great powerband and I just put it in third gear and ran the whole race that way, with some very competitive lap times also (didn't finish though, bad battery!). Other teams seem like they are shifting all the time. Your shifting requirements will depend on too many things for us to give you a square answer. If you have an old car then use it to give yourself an idea, assuming they are powered and geared similarly.

Tim
University of Missouri - Columbia

[Frank]

i'd stand rooting if you could put ANY of these cars through a "few" gearchanges per lap and be competitive

Frank

"These cars feel great...SIDEWAYS"

[Akos]

Frank,

You don't need to shift all the time to be competitive. Upshifts cost you time (even with an ignition cut), and subsequent downshifts upset the car under braking.

If your eninge tuned with a wide power band, you won't need to shift. We did the entire endurance in 2002 in Formula Student in one gear, and if I remember correctly in the US competition shifting 2 gears up in each straight. I don't think you could say that the car was not competitive though.

Cheers,

Akos Toth
U of Toronto FSAE 97..02

[Charlie]

So how competitive was it? What kind of lap times are you talking about?

For the amatuer driver you likely have a point. But it's tough to argue that no shifts make the car faster. It's a pretty proven fact that the torque multiplication from lower gearing (which also means more shifts) is very beneficial to acceleration. We shifted a lot in endurance. I would like to shift less, but I know to have the same acceleration and shift less we need more power, not less gear.

-Charlie Ping
Auburn University FSAE 1999-present

[Buick_58]

Firstly thanks for giving me extra things to concentrate on, most of which i had thought of.

Argus as for researching with other team members, i had already done that but seeing im new to SAE and this list i thought id ask everyone just to spark some new debate/questions. I'll also watch what i repeat on the list in future to keep everyone happy.

Hopefully my design wont add too much weight to our car for the benefit we will gain from it, that is another issue which will be found during alot of testing.

Cya
Dave

Monash Uni

[terc04]

Trust me, if our car had more power, and wasn't so touchy with the throttle in the low gears we would have shifted more. The fact is that the car felt better to me through most of the track in third gear. Only in the slowest section did I wish that our throttle wasn't like a switch. I do not have the actual lap times in front of me but my team members said that the car was among the ten fastest up to that time.

Tim

[terc04]

While sitting in class I was thinking about this subject. Our 2001 car, which finished 2nd in auto-x, 2nd in endurance, and 2nd overall, was very fast. It had good gearing and gobs of power. That car saw shifts about 8 times per lap.
When we are testing our 2001 car along side our 2002 car, despite the vast power differences, our 2002 car is consistantly over one second faster on a tight 50 second course. The difference is that the 2002 car is hooked up. The 2002 car does not need to shift nearly as much to be as fast, regardless of the torque multiplication by using the ideal gear for each corner.

Back to the original point. Your shifting needs will entirely depend on the car's engine, drive and handling.

Tim

[Dan B]

go to www.csupomona.edu/~fsae (http://www.csupomona.edu/~fsae) and watch the in car video of our 2000 car. See if you can count fast enough to count the shifts...

[Jason Hickman]

it is very much dependent on your powerband, car weight, and driver skill. All our cars were from 450 to 500 lbs, with 13" wheels, and cbr powerplants.

My feeling is that if you have enough power to induce wheelspin out of the corner and on the straight, that adding more shifts is only going to hurt your performance. That said, the most I have ever shifted on the straights, is twice (2,3,4). Most of my time is spent in 3rd, with second used for very tight corners (such as near the flagman), 4th being used in the back of the track. 2nd and 3rd gears were traction limited. I only touched 4th on the back because I ran out of revs (rev limiter set at 12,500).

But, I tend to use the high rpm capability of these motors. This does you no good if you are looking for fuel savings. So, there is an argument for more shifts, and a rev limiter set at say.... 10 grand.

I also think the longer gearing is easier to drive, in that you aren't tricking your somewhat inexperienced drivers into thinking they are accellerating like bats out of hell, when in fact they are just spinning the tires down the straight.

[jack]

that inboard camera video is badass, did you use a lipstick cam, or just duct tape on the old camcorder? that was a sweet video.

JACK
www.etec.wwu.edu (http://www.etec.wwu.edu)

[Dave Cook]

Jack

That was just a camcorder with zipties and velcro. Just a word of caution, during the driver change they noticed it and questioned wether it went through tech that way. It didn't make it back out on the track and I was thankful they didn't hit us for the time it took to find the wire cutters and remove it..

Back to the original question, I looked in the data file, and our first driver was shifting 14 or 16 times each lap, that includes up and down shifts. Mostly 2 and 3rd gear, just getting into 4th gear on the long straight. fastest speed was 50 mph and lowest was 21.

In the video you will notice how non-eventful the shifts are for the driver. In the first right hand corner he shifts right in the middle, that is how a good paddle system looks when its working right.

Dave Cook
Cal Poly Pomona
1996-2000

[Sam Jowa]

Man that shifting does seem pretty smooth. If you don't mind, how does that paddle shifter work?
Sam

[MoTeC]

Frank, if you have wheel speed going into the ECU then you can do the gear calculation to get your "ideal".

Donna