Three simple questions - pls point me

[smitty2]

I love computer models, sims, and graphs! Just remember that the most precise computer simulation has at best an 80% chance of being right on... You cannot factor every "Variable" into a sim.. real life does not go by the Book of Logic, and even though you have planned everything down to the most ridiculous variable there will always be that "Once in a lifetime" situation where a Ring Tailed Lemur jumps out of the fairing just as you pass the 2 mile marker.

 Smitty     

[Interested Observer]

Lsrengineer:

Your curves came out very nicely.  Looks like Suzuki did a pretty good job with their ratio splits.

From your earlier posts, it would seem that you are embarking on making up a performance prediction worksheet.   I have done this previously for a drag racing application, even involving a torque converter in order to explore ratios, shift rpm and other parameters.  With a little tuning it would duplicate the Racepak data collected on the car and give good ET’s and speeds, as well as trends due to changes.  (Traction limitations were not an issue in this case, but that can be fairly easily handled).

I only mention this because the analysis was based on short time increments, while you had mentioned using distance increments.  I hadn’t tried to use distance increments, but know using time produced a pretty straight forward (non-iterative) set of calculations.  You might want to consider it before you get too deep into it.  Naturally, speed and distance are then easily derived from the acceleration/time results.  Also, if run data is taken on the vehicle, it will most likely be as a function of time as well, making comparison easier.

Including any corrections for lemurs is up to you.

[lsrengineer]

Lsrengineer:

Your curves came out very nicely.  Looks like Suzuki did a pretty good job with their ratio splits.

From your earlier posts, it would seem that you are embarking on making up a performance prediction worksheet.   I have done this previously for a drag racing application, even involving a torque converter in order to explore ratios, shift rpm and other parameters.  With a little tuning it would duplicate the Racepak data collected on the car and give good ET’s and speeds, as well as trends due to changes.  (Traction limitations were not an issue in this case, but that can be fairly easily handled).

I only mention this because the analysis was based on short time increments, while you had mentioned using distance increments.  I hadn’t tried to use distance increments, but know using time produced a pretty straight forward (non-iterative) set of calculations.  You might want to consider it before you get too deep into it.  Naturally, speed and distance are then easily derived from the acceleration/time results.  Also, if run data is taken on the vehicle, it will most likely be as a function of time as well, making comparison easier.

Including any corrections for lemurs is up to you.

I need to think more, you might be right that time increments will be easier, I know distance needs iteration.   I'm going to try time increments, I'm guessing if the increment is small enough the results should be the same.  Thanks.

[wobblywalrus]

Shift points in LSR do not need to be rocket science accurate based on my experience.  The lines on the tachometer are little strips of electrical tape.  One is at the 6300 rpm minimum shift point calculated an a previous post.  The other is at the 8,000 rpm red line.  Any shift between the two is a good'un.  Simply shift into top gear when the tach needle is between the two black lines.

[lsrengineer]

Shift points in LSR do not need to be rocket science accurate based on my experience.  The lines on the tachometer are little strips of electrical tape.  One is at the 6300 rpm minimum shift point calculated an a previous post.  The other is at the 8,000 rpm red line.  Any shift between the two is a good'un.  Simply shift into top gear when the tach needle is between the two black lines.

100% agree, you have space to get the car up to speed, therefore shifting at a "perfect" rpm for the next gear in an attempt at maximum acceleration is really not needed in most cases.  I don't know, probably many cars are very close to max. speed when going through all three timed miles.  The hope is by simulation I/we can see trends that align with experience and therefore reduce the number of trials needed to reach a goal.  BTW - what cars or who has data logging?  Maybe I need to use the search button a bit more and see if someone has posted data logging data.

[55chevr]

The shift that really matters is the shift into high gear. Short shift that one and it could take you all the way to floating mountain to peak RPM.

[SPARKY]

 

[jl222]

  We posted data logging for the 222 Camaro [ build diarys.. getting ready for bonneville] last post.

  Might not help you much because we short shift every gear, and we posted the data to show traction
difference between this year and last at Bville. Data is from our f.A.S.T. EFI system.

  I have the Bonneville Pro computer program [ by racing secrets .com] that you could input all the data
your trying to figure out and it brings it up. Different gearing? input data, click on TS [time slip] there it is.
 more hp? less CD... whatever. A few keystrokes and there it is.


              JL222


                     

[Interested Observer]

JL222:

Yeah, but Bonneville Pro’s website example shows a 2350 lb car with 0.8 lift coefficient accelerating at 1.4 g’s and going 353 mph at the 2-1/4 !!!    Do you believe that?  Do you believe any of that except perhaps the lift coefficient?   Makes you wonder just what the calculation methodology is.

[lsrengineer]

  We posted data logging for the 222 Camaro [ build diarys.. getting ready for bonneville] last post.

  Might not help you much because we short shift every gear, and we posted the data to show traction
difference between this year and last at Bville. Data is from our f.A.S.T. EFI system.

  I have the Bonneville Pro computer program [ by racing secrets .com] that you could input all the data
your trying to figure out and it brings it up. Different gearing? input data, click on TS [time slip] there it is.
 more hp? less CD... whatever. A few keystrokes and there it is.


              JL222


                     

Thanks, I'll look it up. I would be curious re. if my results compare in some way to the Bonneville Pro results.  I assume Bonneville Pro is not free.  When I get my spread sheet working, I'll post it - anyone can use if they like, probably will not be as user friendly as BP.

[saltwheels262]

from what I've been reading and the info that I've gathered--
the bonneville pro is pretty much the state of the art.

franey

[saltwheels262]

from what I've been reading and the info that I've gathered--
the bonneville pro is pretty much the state of the art.

franey

glitch in the tablet. double post.

[jl222]

JL222:

Yeah, but Bonneville Pro’s website example shows a 2350 lb car with 0.8 lift coefficient accelerating at 1.4 g’s and going 353 mph at the 2-1/4 !!!    Do you believe that?  Do you believe any of that except perhaps the lift coefficient?   Makes you wonder just what the calculation methodology is.

 Yea some of his examples are way off on acceleration, their main program is for 1/4 drag. and in the bville program the smallest tire width you can enter is 7.5'' but we have accelerated faster than the program says we can at EL Mirage. Which means I could input more hp.
 
 I don't know what hp that 2350 lb car has or tire width, but I believe the fastest 21/4 time at bville is around 330mph and probably not full throttle in every gear.
  I'm pretty sure Fast Freddy has gone 320 in his [3200 lb I believe] lakester,with 2 wheel drive, and most lakester didn't go
really fast untill adding wings. Joe Law was the fastest lakester  with a 349 mph time [pretty sure on gas in fuel class] for awhile and with wing.
  So if these cars weighed 2300 and [BIG IF] they could hook up yea, I believe it.
  There are some on here that could tell us about their times and throttle positions and problems hooking up.
   Thats why we posted the data in our build diary.

 Whats hard to believe is 320+ mph in 3.76 sec in 1000ft

  I remember when all the engineers said the fastest speed one could go in the 1/4 mile was 140 mph, now there at 280
in the 1/8 .

  The Bville Pro can shown when your over geared before you buy gears if you know hp weigh Cd frontal area ect.
  We can bring up Bville Pro and see what speed at shift points or at any rpm and time during run recorded by FAST
data logger.

  Its also possible to work backward to estimate hp-cd-ect by matching data to speed.

                JL222



               

 

[lsrengineer]

JL222:

Yeah, but Bonneville Pro’s website example shows a 2350 lb car with 0.8 lift coefficient accelerating at 1.4 g’s and going 353 mph at the 2-1/4 !!!    Do you believe that?  Do you believe any of that except perhaps the lift coefficient?   Makes you wonder just what the calculation methodology is.

 Yea some of his examples are way off on acceleration, their main program is for 1/4 drag. and in the bville program the smallest tire width you can enter is 7.5'' but we have accelerated faster than the program says we can at EL Mirage. Which means I could input more hp.
 
 I don't know what hp that 2350 lb car has or tire width, but I believe the fastest 21/4 time at bville is around 330mph and probably not full throttle in every gear.
  I'm pretty sure Fast Freddy has gone 320 in his [3200 lb I believe] lakester,with 2 wheel drive, and most lakester didn't go
really fast untill adding wings. Joe Law was the fastest lakester  with a 349 mph time [pretty sure on gas in fuel class] for awhile and with wing.
  So if these cars weighed 2300 and [BIG IF] they could hook up yea, I believe it.
  There are some on here that could tell us about their times and throttle positions and problems hooking up.
   Thats why we posted the data in our build diary.

 Whats hard to believe is 320+ mph in 3.76 sec in 1000ft

  I remember when all the engineers said the fastest speed one could go in the 1/4 mile was 140 mph, now there at 280
in the 1/8 .

  The Bville Pro can shown when your over geared before you buy gears if you know hp weigh Cd frontal area ect.
  We can bring up Bville Pro and see what speed at shift points or at any rpm and time during run recorded by FAST
data logger.

  Its also possible to work backward to estimate hp-cd-ect by matching data to speed.

                JL222

My first pass is to see if available tractive effort - drag = ma can be matched to our time slip.  That's the car I have the most info. on.  Cd adjusted for top speed on time slip assuming accel = 0, driver said very little rpm change, no logger so don't really know.  The slip will be assumed zero or equal to the tire growth, someone mentioned this.  I read somewhere that the aero drag overwhelms other items and some of the other items are in the chassis dyno data used.  Don't know it could be all for not.


               

 

[Interested Observer]

The question was not whether Freddy, with a wing (downforce) and 2/3 of his weight could possibly approach 350 mph.  It was whether Bonneville Pro produced a realistic result for the vehicle modeled.  Clearly it did not.  Not even close.  So one has to question whether a warmed-over drag race program is a good tool for making Bonneville predictions.  It may give reasonable results for terminal speed, where everything reduces to drag, final ratios, and horsepower, but you don’t need a whole spreadsheet to do that.  For anything else it seems pretty shaky.

(A better way to estimate Cd is to do a coast-down test and analyze your FAST data).