Official Baja SAE Forums Homepage
Forum Home Forum Home > General > Design Discussion
  New Posts New Posts RSS Feed - Acceleration MPH
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Acceleration MPH

 Post Reply Post Reply Page  12>
Author
Message
Unproductive View Drop Down
Milling Master
Milling Master
Avatar

Joined: Jul/11/2009
Location: Rochester NY
Status: Offline
Points: 66
Post Options Post Options   Thanks (0) Thanks(0)   Quote Unproductive Quote  Post ReplyReply Direct Link To This Post Topic: Acceleration MPH
    Posted: Jul/17/2009 at 12:54am
I was wondering what kind of mph you guys were seeing at the end of the accel test, or in the endurance for that matter.

We don't have the datalogger setup yet.


Edited by Unproductive - Jul/17/2009 at 12:56am
-Bob
Back to Top
adrive7 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Oct/19/2008
Location: Lancaster, CA
Status: Offline
Points: 711
Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2009 at 2:53pm
In CVT tuning sessions before I left, we were getting ~20mph through 100' gates, and a max around 32. Far slower than it should have been based on calcs, even with big loss factors. CVT still needs work.
-Joe
Chief Organizer, Baja California 2016, 2017, 2019
Ohio State Baja 2005-2009
Co-Host, Science... Sort Of
http://www.sciencesortof.com
Back to Top
Waffles View Drop Down
Welding Master
Welding Master
Avatar

Joined: Jun/02/2009
Status: Offline
Points: 110
Post Options Post Options   Thanks (0) Thanks(0)   Quote Waffles Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2009 at 3:44pm
Although CVT tuning is certainly the most important and most time consuming part of baja, don't forget that there are other factors which limit the top speed of a baja car.  One of our alumni once did a back of the envelope calculation analyzing the amount of drag that a flat plate of equal area to the firewall makes at speed.  You eat up that 10 HP in drag pretty quick, which is why it's important to make your firewall as small as possible and drivetrain as efficient as possible
Back to Top
adrive7 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Oct/19/2008
Location: Lancaster, CA
Status: Offline
Points: 711
Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2009 at 4:47pm
Yeah, but at 30mph you are only looking at 2HP. I just ran that calc. Thats with a big firewall. Our car should have been doing in the mid 40's, and you could see clearly the pulleys weren't spooling fully. 
-Joe
Chief Organizer, Baja California 2016, 2017, 2019
Ohio State Baja 2005-2009
Co-Host, Science... Sort Of
http://www.sciencesortof.com
Back to Top
dillon_b12 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/15/2008
Status: Offline
Points: 781
Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2009 at 4:55pm
Originally posted by adrive7 adrive7 wrote:

Yeah, but at 30mph you are only looking at 2HP. I just ran that calc. Thats with a big firewall. Our car should have been doing in the mid 40's, and you could see clearly the pulleys weren't spooling fully. 


I've never seen a Baja car run mid 40s.  ETS(or Sherbrooke) claims 43 in their design poster but who knows if it can actually do that.

Also, top speed is not what makes a car win.  We could probably change out final drive ratio and get in the 40s, but the car would ultimately suffer because it could never get fully wound out and would be short on power for hills, mud holes, and things like that.
Back to Top
adrive7 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Oct/19/2008
Location: Lancaster, CA
Status: Offline
Points: 711
Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2009 at 4:57pm
I just ran it again. Theoretical top end aerodynamically speaking is about 50 with 10hp. Obviously there won't be much torque in the high 40's, but thats why you run a CVT or shifting box. 
-Joe
Chief Organizer, Baja California 2016, 2017, 2019
Ohio State Baja 2005-2009
Co-Host, Science... Sort Of
http://www.sciencesortof.com
Back to Top
CLReedy21 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/30/2008
Location: Marysville, OH
Status: Offline
Points: 736
Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2009 at 5:53pm
What about off road tire rolling resistance or the efficiency of a belt drive and subsequent friction losses of every moving part in the system?  Fastest car that I've ever heard of was a gearbox car that could hit 38-39mph on flat ground.  We geared for 36 this year and that was really stretching it and required a huge area to get topped out.  If the pulleys aren't fully shifting, that means you're out of power and they won't shift farther.  I'm not trying to call BS on your car, but that's way past what I've always considered possible.
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."
Back to Top
rjwoods77 View Drop Down
Milling Master
Milling Master


Joined: Jul/05/2009
Status: Offline
Points: 65
Post Options Post Options   Thanks (0) Thanks(0)   Quote rjwoods77 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2009 at 6:39pm
Does anyone have any data from this year running the the accel events in each race?
Back to Top
CLReedy21 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/30/2008
Location: Marysville, OH
Status: Offline
Points: 736
Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2009 at 6:45pm
They were all 150' events, 2 on hard dirt, one on asphalt.  As far as actual run data I don't have any since dataloggers have to be included in the cost report.
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."
Back to Top
j-man View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Apr/05/2009
Status: Offline
Points: 30
Post Options Post Options   Thanks (0) Thanks(0)   Quote j-man Quote  Post ReplyReply Direct Link To This Post Posted: Jul/27/2009 at 9:32pm
Our 43.5 mph claim is reached on long downhill runs similar to what we had in Oregon (without the corners...) but on a level asphalt we can easily reach 37 mph (40 being a top speed on level road) depending on the wind, tire pressure, etc.
 
But obviously it takes a lot more than 150 ft. Air drag and tire rolling resistance are responsible for most of the losses as our biggest powertrain losses are, according to our tests, limited to the transient sequences of the CVT.  If you eliminate the 43mph because you need to be a little gravity assisted, 40mph means a difference of 10,71% to our goal.
 
I know for sure FEI and probably OSU have similar data.
Jean-Martin
Used to be Design leader and CNC abuser
ETS Baja SAE 07-10
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post Posted: Jul/27/2009 at 10:56pm
Originally posted by j-man j-man wrote:

Our 43.5 mph claim is reached on long downhill runs similar to what we had in Oregon (without the corners...) but on a level asphalt we can easily reach 37 mph (40 being a top speed on level road) depending on the wind, tire pressure, etc.
 
But obviously it takes a lot more than 150 ft. Air drag and tire rolling resistance are responsible for most of the losses as our biggest powertrain losses are, according to our tests, limited to the transient sequences of the CVT.  If you eliminate the 43mph because you need to be a little gravity assisted, 40mph means a difference of 10,71% to our goal.
 
I know for sure FEI and probably OSU have similar data.


We have similar numbers to you also:

Our theoretical was 43mph, but we ended up hitting a max of 38 mph for a brief second at Auburn on the slight downhill during the invitational last year according to the Race Tech. data system that we have
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development
Back to Top
waylon View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/05/2009
Location: Iowa State Univ
Status: Offline
Points: 2
Post Options Post Options   Thanks (0) Thanks(0)   Quote waylon Quote  Post ReplyReply Direct Link To This Post Posted: Sep/05/2009 at 9:46pm
When you guys are running your calculations are you using 10hp.  A few years ago our team dyno'ed a stock briggs and were only seeing a peak of 8hp. This is quite a large difference and could be a significant source of error.
Back to Top
CLReedy21 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/30/2008
Location: Marysville, OH
Status: Offline
Points: 736
Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/05/2009 at 10:28pm
When I say theoretical I mean the engine is at the rev limiter with the CVT shifted fully.  It's a function of engine RPM, gear ratio, and cvt shift ratio.
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."
Back to Top
johnpate01 View Drop Down
Welding Master
Welding Master
Avatar

Joined: Mar/09/2009
Location: Knoxville, TN
Status: Offline
Points: 150
Post Options Post Options   Thanks (0) Thanks(0)   Quote johnpate01 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/06/2009 at 9:27am
That's basically the same idea that we are using, but with some allowances for the CVT shift ratio never really reaching 100%.  I think we shot for 95% of max in the overdrive mode.
-John

Co-Captain, Team Tennessee 2008-2010
Back to Top
Shocker Racer View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/13/2009
Status: Offline
Points: 37
Post Options Post Options   Thanks (0) Thanks(0)   Quote Shocker Racer Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2009 at 10:44pm
Does anybody have a speed that you could gear a car to, and be certain you will reach that speed.  We have played around with the idea of gearing a car to 30,35, or 40 mph and know we can get there rather than gear higher and use gravity down hill. 
Wichita State University
Shocker Baja Racing

Back to Top
adrive7 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Oct/19/2008
Location: Lancaster, CA
Status: Offline
Points: 711
Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2009 at 12:08am
I guarantee you can hit 20.
-Joe
Chief Organizer, Baja California 2016, 2017, 2019
Ohio State Baja 2005-2009
Co-Host, Science... Sort Of
http://www.sciencesortof.com
Back to Top
Shocker Racer View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/13/2009
Status: Offline
Points: 37
Post Options Post Options   Thanks (0) Thanks(0)   Quote Shocker Racer Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2009 at 12:13am
LOL....you can get to 20 with a super high gear ratio.   we currently have an old car that will theoretically do 55mph and it will do 21mph by 150ft.  Much over that and you need miles to get the cvts to continue to shift.
Back to Top
Unproductive View Drop Down
Milling Master
Milling Master
Avatar

Joined: Jul/11/2009
Location: Rochester NY
Status: Offline
Points: 66
Post Options Post Options   Thanks (0) Thanks(0)   Quote Unproductive Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2009 at 12:25am
Last year we geared the car for 45mph, it was a bad idea but we were pretty much forced to by packaging constraints.

This year we're building a 3 speed gearbox that will have a low gear, a running gear that we'll use most of the time, and a high speed gear that is mostly there because all we had to do was add a gearset.
-Bob
Back to Top
adrive7 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Oct/19/2008
Location: Lancaster, CA
Status: Offline
Points: 711
Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2009 at 12:32am
More seriously, our car last year was geared to about 44. GPS Top end was 32. 20mph through 100'.
-Joe
Chief Organizer, Baja California 2016, 2017, 2019
Ohio State Baja 2005-2009
Co-Host, Science... Sort Of
http://www.sciencesortof.com
Back to Top
jeiB View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jul/17/2009
Location: Montreal
Status: Offline
Points: 604
Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2009 at 1:15am
We have our new car geared to 37mph with 23in tires but i think we are going to switch to 25's and therefore reach a top speed of 40mph. We hit 36mph in montreal downhill.
I ran the areodynamic calcs and i get a max speed of 40mph with the following parameters:
rpm=3600
max power=9.5hp
engine efficient=0.7
coefficient of drag=1.15
air density=1.2 kg/m^3
frontal area=1.2m^2

i think all those numbers are pretty conservative so maybe we can squeeze out a few more mph but anything above 40mph is unreasonable.



Edited by jeiB - Nov/10/2009 at 1:33am
Jeremie B.
McGill Baja Racing
2009-2011 Captain
minibaja.mcgill.ca
Back to Top
Shocker Racer View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/13/2009
Status: Offline
Points: 37
Post Options Post Options   Thanks (0) Thanks(0)   Quote Shocker Racer Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2009 at 9:26am
40 seems reasonable to me, however i wouldnt be surprised if you get less HP than what you have accounted for.  Also i dont like gearing for "downhill" as it seems you spend little time going down hill at most courses and the speed out of the corners and uphills seems more valuable to me.  However, i dont think you are far off by gearing to 40.  We geared this year for 37 as well.
Wichita State University
Shocker Baja Racing

Back to Top
mu View Drop Down
Milling Master
Milling Master


Joined: Dec/14/2008
Location: NC
Status: Offline
Points: 82
Post Options Post Options   Thanks (0) Thanks(0)   Quote mu Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2009 at 10:21am
I was orignally shooting for 38 mph but the way the gearing worked out it'll be around 37mph.  We'll see how it works out.
Andy

2009-2010 Ohio State Baja SAE Captain
www.osubaja.com
Back to Top
CLReedy21 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/30/2008
Location: Marysville, OH
Status: Offline
Points: 736
Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2009 at 1:30pm
We gear a little different than a lot of folks it seems.  Our cars will actually run what we gear them for (maybe cause it's so low) so theoretical and actual are usually the same or 1mph off.  '07 ran 27, '08 ran 28, '09 ran 33 and 35, and '10 is getting geared for 32-33.
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."
Back to Top
jhu42 View Drop Down
Welding Master
Welding Master
Avatar

Joined: Jan/27/2009
Location: Columbus, Ohio
Status: Offline
Points: 145
Post Options Post Options   Thanks (0) Thanks(0)   Quote jhu42 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2009 at 2:38pm
Originally posted by CLReedy21 CLReedy21 wrote:

'10 is getting geared for 32-33.
 
I dont know, that seems a bit slow for Rochester. 
Adam Baumgartner
Social Media Director, #BajaMaryland
Test Driver, Honda R&D Americas Inc
Hopkins Baja, '07-'10
Back to Top
CLReedy21 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/30/2008
Location: Marysville, OH
Status: Offline
Points: 736
Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2009 at 2:55pm
'07 finished 3rd overall and 3rd in the endurance on the lead lap with a Comet cvt and a 27mph top end.  Don't forget about all those hills, we like to go up them pretty quickly :)
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."
Back to Top
jhu42 View Drop Down
Welding Master
Welding Master
Avatar

Joined: Jan/27/2009
Location: Columbus, Ohio
Status: Offline
Points: 145
Post Options Post Options   Thanks (0) Thanks(0)   Quote jhu42 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2009 at 3:23pm
Originally posted by CLReedy21 CLReedy21 wrote:

  Don't forget about all those hills, we like to go up them pretty quickly :)


hmmm... good point.  I had forgotten :)


Adam Baumgartner
Social Media Director, #BajaMaryland
Test Driver, Honda R&D Americas Inc
Hopkins Baja, '07-'10
Back to Top
jeiB View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jul/17/2009
Location: Montreal
Status: Offline
Points: 604
Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2009 at 7:23pm
well, if you look at the CVTech cvt for this year (same as last year), the shift range is close to 7:1. Setting your maximum speed at 40mph and a mininum torque sufficient enought to climb a 35deg incline, ideally, you would require a shift range of 6.15:1.
Thats the reason why ETS and Sherbrooke had larger than usual top speed last year, the shift range is soo big that trying to go a little faster wont hurt your torque.
In montreal, our theoritical top speed was 38mph and we reached 36mph (albeit downhill)
Jeremie B.
McGill Baja Racing
2009-2011 Captain
minibaja.mcgill.ca
Back to Top
povajax View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Jan/01/2009
Location: Toluca
Status: Offline
Points: 17
Post Options Post Options   Thanks (0) Thanks(0)   Quote povajax Quote  Post ReplyReply Direct Link To This Post Posted: Feb/07/2011 at 2:01pm
i know this depends on many factors but i would like to know how many rpms of the engine is the real value to calculate the real final speed
for example 
if i have a reduction of 10 to 1
and the cvt .76 in high   tires= 22 inch    vehicule weight:400 pounds
 
top speed= 3800/(10x.76) x (22x.0000254x3.1416) x 60= 52.6656 km/hr

but i dont now the real loses of the engine an cvt 

whats is the rpms 3200? 3600?



Edited by povajax - Feb/07/2011 at 5:00pm
Back to Top
jeiB View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jul/17/2009
Location: Montreal
Status: Offline
Points: 604
Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Feb/07/2011 at 5:42pm
engine rpm is probably going to be around 3550-3600
Jeremie B.
McGill Baja Racing
2009-2011 Captain
minibaja.mcgill.ca
Back to Top
João Araujo View Drop Down
Milling Master
Milling Master


Joined: Feb/07/2009
Location: Brazil
Status: Offline
Points: 61
Post Options Post Options   Thanks (0) Thanks(0)   Quote João Araujo Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2011 at 10:30am
That car is not going to pass 45 km/h... 

.76 maybe it's comet, maybe polaris, both cant use the whole range.

in testing you'll see that neither it starts on the nominal reduction, or it ends...
UFPBaja Team - Brazil
Back to Top
povajax View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Jan/01/2009
Location: Toluca
Status: Offline
Points: 17
Post Options Post Options   Thanks (0) Thanks(0)   Quote povajax Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2011 at 2:02pm
This isn't true, i tested in our test track and we reached almost 58 km/hr with our car that was 13th in acceleration in South Carolina 
Pedro
2009 team captain baja sae Uaem
be wild Sara Juana Racing team
Back to Top
João Araujo View Drop Down
Milling Master
Milling Master


Joined: Feb/07/2009
Location: Brazil
Status: Offline
Points: 61
Post Options Post Options   Thanks (0) Thanks(0)   Quote João Araujo Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2011 at 2:24pm
top speed= 3800/(10x.76) x (22x.0000254x3.1416) x 60= 52.6656 km/hr

How is the top speed more then the maximum in theory?


UFPBaja Team - Brazil
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2011 at 5:52pm
Originally posted by povajax povajax wrote:

This isn't true, i tested in our test track and we reached almost 58 km/hr with our car that was 13th in acceleration in South Carolina 
 
How did you measure your top speed?
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development
Back to Top
povajax View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Jan/01/2009
Location: Toluca
Status: Offline
Points: 17
Post Options Post Options   Thanks (0) Thanks(0)   Quote povajax Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2011 at 6:49pm
Originally posted by João Araujo João Araujo wrote:

top speed= 3800/(10x.76) x (22x.0000254x3.1416) x 60= 52.6656 km/hr

How is the top speed more then the maximum in theory?



i dont know  if you read my first comment but 
the commentary said, for example mmmmmm ... I was just explaining my point not the ratio, weight  or cvt that have our car.  our car weights 370 lb
 it is unlikely that any team will tell you their exact ratio, 
and with all possible respect I do not want to fight just want some good team with experience in this area tell me what  parameters used to measure the maximum speed of his ratio  thats all Smile
Pedro
2009 team captain baja sae Uaem
be wild Sara Juana Racing team
Back to Top
João Araujo View Drop Down
Milling Master
Milling Master


Joined: Feb/07/2009
Location: Brazil
Status: Offline
Points: 61
Post Options Post Options   Thanks (0) Thanks(0)   Quote João Araujo Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2011 at 6:55pm
I said that the example car wouldn't, and you did not explain...

anyway, that depends totally on the CVT, on it's shift point...

so it depends on weights, ramps, helix, spring, reduction, belt tension....
UFPBaja Team - Brazil
Back to Top
povajax View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Jan/01/2009
Location: Toluca
Status: Offline
Points: 17
Post Options Post Options   Thanks (0) Thanks(0)   Quote povajax Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2011 at 7:22pm
Originally posted by blue2kss blue2kss wrote:

Originally posted by povajax povajax wrote:

This isn't true, i tested in our test track and we reached almost 58 km/hr with our car that was 13th in acceleration in South Carolina 
 
How did you measure your top speed?

with  a really simple method, our car was follow with a atv and the speedometer says 58 km hr
our car is light (370 lb) small ans fast maybe we has the smallest car in south carolina 2010 but our suspension sucks just i think that we are fast because we have a really good power train (gearbox 11lb) and 20x7x10 tires reducing the moments of inertia but we need work a lot with suspension Confused

this is our 2010 car in south carolina

Pedro
2009 team captain baja sae Uaem
be wild Sara Juana Racing team
Back to Top
CLReedy21 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/30/2008
Location: Marysville, OH
Status: Offline
Points: 736
Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2011 at 10:58pm
I think this has gotten waaaay off topic.  The OP wanted to know how many engine RPM teams are turning when the CVT is fully shifted.  I don't have a precise answer without digging through old datalogs, which I'm honestly too lazy to do tonight.

So, any takers?
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."
Back to Top
Pedro UFPBaja View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Mar/03/2010
Location: Brazil
Status: Offline
Points: 886
Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 12:00am
Originally posted by povajax povajax wrote:

Originally posted by João Araujo João Araujo wrote:

top speed= 3800/(10x.76) x (22x.0000254x3.1416) x 60= 52.6656 km/hr

How is the top speed more then the maximum in theory?



i dont know  if you read my first comment but 
the commentary said, for example mmmmmm ... I was just explaining my point not the ratio, weight  or cvt that have our car.  our car weights 370 lb
 it is unlikely that any team will tell you their exact ratio, 
and with all possible respect I do not want to fight just want some good team with experience in this area tell me what  parameters used to measure the maximum speed of his ratio  thats all Smile

Funny words, man.
Weight ,ratio, cvt model... mean nothing alone. 
What really makes it different is the setting of the cvt, if you curve it has adapted to the resistive forces which your car is subjected and keeping the engine running properly to each load situation.

For example:
This is our 2009 car




And this is 2010



Both use the same ratio and same CVT, the 2010 is heavier but pretty much faster.


PS
the theorical speed serves to almost nothing, unless your car is moving on vacuum on a track with almost no friction on a straigth runway of 100 miles.



Edited by Pedro UFPBaja - Feb/09/2011 at 1:53am
Former Team Captain
Back to Top
Akron 1998 to 2004 View Drop Down
Welding Master
Welding Master
Avatar
Thread Hijack Champion

Joined: Jan/20/2011
Location: WA
Status: Offline
Points: 327
Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 11:39am

The engine governor is not digital, it's an analog device that starts to affect engine power about 300 rpm before the max RPM.

 

Governed: 3800 RPM

Peak Power: 3500 - 3600 RPM

 

Special Note: If your car doesn't get to that speed in 100 to 150 feet on race day, IT DOESN"T REALLY MATTER!

 

As far as I know, the last time they recorded top speed was 2005 with engines governors set to 3800 RPM.  I believe this was in 100 feet.

 
# Team Accel Trap #1
(sec)
Speed #1
(mph)
Accel Trap #2
(sec)
Speed #2
(mph)
73 SAE Brasil - SAE Brasil #2 4.242 28.2 4.224 29.3
4 University of South Florida - noBull 4.354 27.3 4.507 24.0
7 Instituto Technolgico De Buenos Aires - ITBA Competicion 4.473 26.3 4.451 26.7
70 University of Michigan-Dearborn - UM-D Racing 2 4.462 26.5 4.486 26.1
5 Ecole De Technologie Superieure - ETS 4.484 26.2 4.613 26.1
50 Wichita State Univ - WSU Shocker Racing 4.352 25.8 4.477 26.0
117 University of Michigan-Ann Arbor - Maize 4.459 25.4 4.529 26.0
1 SAE Brasil - SAE Brasil #1 4.329 25.8 4.490 25.9
91 Penn State Univ-Shenango - Team Shenango 4.835 25.8 4.878 25.3
64 Universite De Sherbrooke - Sherbrooke Racing Team 4.640 25.7 4.609 ?
 
Back to Top
João Araujo View Drop Down
Milling Master
Milling Master


Joined: Feb/07/2009
Location: Brazil
Status: Offline
Points: 61
Post Options Post Options   Thanks (0) Thanks(0)   Quote João Araujo Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 2:20pm
Actualli, in baja brazil, we still have a max speed test.. (but thats on 300 feet)

FEI reached 58,5, Poli-USP 55

and a lot of teams above 50.

EDIT: That's in Km/h... not mph..


Edited by João Araujo - Feb/09/2011 at 2:21pm
UFPBaja Team - Brazil
Back to Top
Akron 1998 to 2004 View Drop Down
Welding Master
Welding Master
Avatar
Thread Hijack Champion

Joined: Jan/20/2011
Location: WA
Status: Offline
Points: 327
Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 3:01pm

FEI reached 58.5 km/h (36.4 mph), Poli-USP 55 km/h (34.17 mph)

 

So the fastest car is 6% faster than the 2nd fastest car.  ABSOLUTLY NOTHING SUSPISIOUS ABOUT THAT!!!  FEI’s car would only require about a 13% improvement in drive train efficiency or engine output over Poli-USP.  If you just happen to be on FEI’s team, I don’t buy the argument that FEI's car weighs so much less than Poli-USP’s car.  Someone should have demand an inspection.

 

Back to Top
João Araujo View Drop Down
Milling Master
Milling Master


Joined: Feb/07/2009
Location: Brazil
Status: Offline
Points: 61
Post Options Post Options   Thanks (0) Thanks(0)   Quote João Araujo Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 3:05pm
That's CVT tuning, they use a highly modded CVTech driver, and a Team performance modded secondary.

poli-usp weights 150 kg[330 lbs), FEI actually weights more (around 157 [345 lbs]).

I'm From UFPBaja (same team as Pedro UFPBaja that posts in this forum also).

We never could go to US, we finished 12 on baja brazil, only top 3 teams can go.. UFSC would go this year, but they were late for technical inspection, they got desqualified from the dynamic events.

in 2008 UFPE reached 56 km/h, i don't believe that 2 km/h is that much more.

Our new car is weighting 143 kg (314,6 lbs) now, it's not finished yet, when it does, it will weight around the same as Poli-USP.


Edited by João Araujo - Feb/09/2011 at 3:10pm
UFPBaja Team - Brazil
Back to Top
jeiB View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jul/17/2009
Location: Montreal
Status: Offline
Points: 604
Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 4:20pm
Careful Akron 1998 to 2004, you seemed to be accusing FEI of cheating. They are a VERY well established team and have no doubt a GREAT car every year. Top speed has nothing to do with weight.

Things that will help your top speed:
Rolling resistance
drag (they have a half firewall, thus reducing there drag coef,)
drivetrain efficiency

Jeremie B.
McGill Baja Racing
2009-2011 Captain
minibaja.mcgill.ca
Back to Top
Pedro UFPBaja View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Mar/03/2010
Location: Brazil
Status: Offline
Points: 886
Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 4:29pm
In the Baja SAE Brazil some teams have the engine confiscated for inspection against illegal modifications after the endurace and all engines are sealed in the cage during the rotation inspection.
The FEI's car was one  that had the engine seized for detailed inspection by the briggs brazilian dealer (even UFSC, POLI USP and MAUA lost the engines).
Well, the engines aren't really confiscated, they are traded for new ones.


Edited by Pedro UFPBaja - Feb/09/2011 at 4:31pm
Former Team Captain
Back to Top
Akron 1998 to 2004 View Drop Down
Welding Master
Welding Master
Avatar
Thread Hijack Champion

Joined: Jan/20/2011
Location: WA
Status: Offline
Points: 327
Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 4:39pm

CVT tuning has nothing to do with ultimate top speed if you have a long enough distance (300 feet should be plenty) the CVT completely shifts or stops shifting.  It might as well be a fixed gear ratio at that point.  Anyway, if your argument is Poli-USP didn’t have a tuned CVT; that’s silly.

 

Ultimate top speed is based on rolling resistance, air resistance, drive train efficiency, and engine power output. In a competitive competition the two fastest cars are going to have approximately the same rolling resistance, air resistance, drive train efficiency.  That only leaves engine power output.  58.5 km/h requires 13% more horsepower than 55 km/h (the equation has velocity squared).  Maybe they just got that nearly perfect motor from the factory with all the right tolerances.  It's hard to say why if no one demands an inspection.

 

But this is off topic so if you feel like disagreeing with me, I’m sure others would prefer you contact me directly.

Back to Top
Akron 1998 to 2004 View Drop Down
Welding Master
Welding Master
Avatar
Thread Hijack Champion

Joined: Jan/20/2011
Location: WA
Status: Offline
Points: 327
Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 4:47pm
Thanks Pedro UFPBaja
 
Good to know the engine was seized for detailed inspection by briggs and passed.  I'd love to know how they got their car that fast.
Back to Top
Pedro UFPBaja View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Mar/03/2010
Location: Brazil
Status: Offline
Points: 886
Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 4:49pm
One more thing: FEI and POLI USP has a gearbox with two speeds in series with the cvt.
UFSC has a fully funcional cvt and a 6 speed gerbox at same time!!!!

see FEI's sistem:



Former Team Captain
Back to Top
dillon_b12 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/15/2008
Status: Offline
Points: 781
Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 4:58pm
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

FEI reached 58.5 km/h (36.4 mph), Poli-USP 55 km/h (34.17 mph)

 

So the fastest car is 6% faster than the 2nd fastest car.  ABSOLUTLY NOTHING SUSPISIOUS ABOUT THAT!!!  FEI’s car would only require about a 13% improvement in drive train efficiency or engine output over Poli-USP.  If you just happen to be on FEI’s team, I don’t buy the argument that FEI's car weighs so much less than Poli-USP’s car.  Someone should have demand an inspection.

 



Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Reading some of this stuff is hilarious.  There is such a scary boogie man in the room.  Do the top 10 teams cheat?  From my 6 years of competing, THIS HAS TO BE THE MOST HONEST MOTORSPORT COMPETITION IN EXSITANCE.

Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

You missed my point entirely. Everyone suspects the other guy of cheating but there is almost no evidence that anyone does.

Which is it man?
Back to Top
João Araujo View Drop Down
Milling Master
Milling Master


Joined: Feb/07/2009
Location: Brazil
Status: Offline
Points: 61
Post Options Post Options   Thanks (0) Thanks(0)   Quote João Araujo Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 5:11pm
CVT tuning has nothing to do with top speed on 300 feet?

You have no idea what you are talking about. if the cvt shfts to soon, it makes it not use the engine full power.

Read the cvt tuning handbook... on 300 feet it's not the final speed yet, so that makes a difference, rolling resistance, inertia, all that makes difference, even the CG position, makes difference..

It's not our fault if you make a 60-70 lbs heavier car... or a giant firewall, or a chain misaligned reduction, or a bad tuned cvt.

Poli-USP was using a old engine, in the US they had a new model, that seems to be better.


Edited by João Araujo - Feb/09/2011 at 5:13pm
UFPBaja Team - Brazil
Back to Top
Akron 1998 to 2004 View Drop Down
Welding Master
Welding Master
Avatar
Thread Hijack Champion

Joined: Jan/20/2011
Location: WA
Status: Offline
Points: 327
Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2011 at 5:16pm

dillon_b12

 

At first glace those comments seem to contradict each other but the engines were seized and inspected by Briggs and nothing was found out of the ordinary.  Thus my comments don’t contradict.  I’m just disappointed that I didn’t have a 110% efficient gearbox.

Back to Top
 Post Reply Post Reply Page  12>
  Share Topic   

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.109 seconds.