Engineer/math minds HELP!!

[Alky V6]

Closest I can figure is your 1-2 shift point would be moved downtrack about 48' from where it is now.

 

[Blazer406]

I started trying to do some manual distance calculations..... based off the 1.705 sec and our calculated MPH..... but the formulas need a constant acceleration to figure it.... and we don't have anywhere close to a constant acceleration. I would imagine the acceleration goes up very quickly to some peak G force.... then begins to taper down the further you travel downtrack.

If you had a table with the slip numbers....DS RPM's .... engine RPM's..... and other stuff we know.... you could get a velocity at each datapoint assuming no tire slippage and assuming a particular tire circumference....... you could get enough datapoints to make a fairly close calculation on an "average" velocity..... then plug in the time....... (1.705 sec) and it would give you the distance traveled.

Still alot of assumptions..... but you should be able to get it fairly close....

 

[BlownV6]

Closest I can figure is your 1-2 shift point would be moved downtrack about 48' from where it is now.

That might be worth the change if it is indeed about 48' further. Mike

 

[BlownV6]

I started trying to do some manual distance calculations..... based off the 1.705 sec and our calculated MPH..... but the formulas need a constant acceleration to figure it.... and we don't have anywhere close to a constant acceleration. I would imagine the acceleration goes up very quickly to some peak G force.... then begins to taper down the further you travel downtrack.

If you had a table with the slip numbers....DS RPM's .... engine RPM's..... and other stuff we know.... you could get a velocity at each datapoint assuming no tire slippage and assuming a particular tire circumference....... you could get enough datapoints to make a fairly close calculation on an "average" velocity..... then plug in the time....... (1.705 sec) and it would give you the distance traveled.

Still alot of assumptions..... but you should be able to get it fairly close....

I can get you pics of the data at any incramentals you want!! Tell at what points(time during the run) you want and I will get them together and post it up here. thanks Mike

 

[Blazer406]

I can get you pics of the data at any incramentals you want!! Tell at what points(time during the run) you want and I will get them together and post it up here. thanks Mike

Do you have excel?

How many data points do you have per second?

I assume you know the first datapoint after the release of the trans brake?

If you have excel... I'll set up a spreadsheet..... with the different time stamps.... i.e. .005 sec, .010 sec ...etc.... and the different fields of data you know from your datalogger..... the more datapoints the more accurate we can get the distance......

I can email it to you once it is set up and you just look up the point and type it in.... then send it back to me....

I know we can analyze the current data..... we might can make some assumptions and get fairly close to what might change when you go to the higher first gear ratio....

I'll give it a whirl anyway....

 

[BlownV6]

I can lock and post the data in thousands of a second, hundreths ,tenths , or anything else. I would think that data at every .250 would be plenty enough without being a rediculous amout of pics. I dont know anything about Excell spread sheets or how they work , or how to send them!! I guess you get the picture!! Lucky I can even navagate this keyboard Mike

Let me know what you want and I will give it a shot!!

 

[Blazer406]

Alright....but .25 sec between datapoints is not going to cut it.... but you don't have to send pics..... just need the data...... lets do it like this....shouldn't take you too long.

Lets put 3 numbers per row...... each separated by a space.....

The first number is engine RPM, second is driveshaft RPM, third is time

Here is how the two points (your fastest pass) we already have would look like:

7021 1967 .500
8040 4022 1.705

See.... engine rpm space driveshaft rpm space time

The more datapoints the better.......


Once you give me all the points..... I should be able to make a fairly accutate guess to the actual speed at each datapoint.

 

[Dusty Bradford]

Holy cow that thing is coupling throughout the top end. This sim can't duplicate the coupling that's occurring as it ramps in tighter to the end of the run

:biggrin:

 

[BlownV6]

Dusty , I already gave you a plug!!

Blazer, At what incraments do you want map out?? Mike

 

[Dusty Bradford]

Dusty , I already gave you a plug!!

Blazer, At what incraments do you want map out?? Mike

I saw that, thanks. It's working much better than I expected it too. That racepak shot was awesome.

3.4 g's and 50+ psi. lol

 

[Blazer406]

Dusty , I already gave you a plug!!

Blazer, At what incraments do you want map out?? Mike

The more the better....

every .05 would be nice...... 20 points per second..... at least thru the 1.705 sec.

 

[BlownV6]

OK here ya go!! Drive shaft always takes a moment to regester.

3637 0 0
4289 2 .05
5252 2 .10
5611 458 .15
6045 420 .20
6418 725 .25
6656 1135 .30
6815 1791 .35
6930 2188 .40
7010 2141 .45
7022 1965 .50
7039 1876 .55
7050 1954 .60
7070 2100 .65
7090 2340 .70
7114 2444 .75
7136 2498 .80
7154 2495 .85
7162 2565 .90
7204 2678 .95
7251 2820 1.00
7307 2946 1.05
7356 3033 1.10
7388 3091 1.15
7424 3139 1.20
7489 3243 1.25
7548 3360 1.30
7602 3456 1.35
7677 3521 1.40
7733 3608 1.45
7755 3655 1.50
7795 3701 1.55
7842 3827 1.60
7941 4006 1.65
8042 4028 1.70

Hope that helps!! Mike

 

[Blazer406]

OK here ya go!! Drive shaft always takes a moment to regester.

3637 0 0
4289 2 .05
5252 2 .10
5611 458 .15
6045 420 .20
6418 725 .25
6656 1135 .30
6815 1791 .35
6930 2188 .40
7010 2141 .45
7022 1965 .50
7039 1876 .55
7050 1954 .60
7070 2100 .65
7090 2340 .70
7114 2444 .75
7136 2498 .80
7154 2495 .85
7162 2565 .90
7204 2678 .95
7251 2820 1.00
7307 2946 1.05
7356 3033 1.10
7388 3091 1.15
7424 3139 1.20
7489 3243 1.25
7548 3360 1.30
7602 3456 1.35
7677 3521 1.40
7733 3608 1.45
7755 3655 1.50
7795 3701 1.55
7842 3827 1.60
7941 4006 1.65
8042 4028 1.70

Hope that helps!! Mike

Interesting..... I get you traveling around 173.29 feet at the 1.700 sec mark

I also see the DS RPM's going up and down like you are going in and out of tire spin ever so slightly..... which could be throwing this off just a little....

example - @ .4 sec ....
DS RPM is 2188
Next is 2141
Next is 1965
Next is 1876
Next is 1954
Next is 2100
Next is 2340

Only way I can explain it is you had just a little tire slippage at .4 sec.... then it tapers down 3 data points later.... then builds again....

I'll keep fiddling with the data........

One eyewatering observation......... even throwing out the apparent small amount of tire spin at .4 sec....... you go from 0-60 in .6 sec.

 

[Alky V6]

I'm getting 154' at the 1.7 sec mark, but that's with a fair amount of tire slip at the hit (22%), tapering down to 8% by just before the 1 sec mark and 4% tire slip by the 1.6 sec mark.
Is there an accurate way to find out how much tire slip you're getting at the launch? I can't imagine how. I've been able to match your launch rpm and 8040 rpm by the 1.7 sec mark. That should be a pretty fair way of judging tire slip.

 

[Blazer406]

Here is a screenshot of my spreadsheet....

 

[Blazer406]

I'm getting 154' at the 1.7 sec mark, but that's with a fair amount of tire slip at the hit (22%), tapering down to 8% by just before the 1 sec mark and 4% tire slip by the 1.6 sec mark.
Is there an accurate way to find out how much tire slip you're getting at the launch? I can't imagine how. I've been able to match your launch rpm and 8040 rpm by the 1.7 sec mark. That should be a pretty fair way of judging tire slip.

The tire slip would definately make my distance traveled be on the high side with the method I am using to figure out the distance traveled.

In reality... the average speed would have been slightly less if there was no tire slip....

 

[Alky V6]

The sim is also taking into account that the engine would be working the TC harder with the higher low gear. I just can't accurately sim the top end due to the coupling.
With the proper data I could sim a particular point on the top end, but then the rest of the run would be trash.
The fix for this sim would be a setting that would allow for the TC slip factor to be varied or ramped starting and ending at particular time stamps during the run.

 

[BlownV6]

You are correct about it spinning slightly. Most cars will accelerate the fastest when the tires are spinning slightly faster than the ground they are covering. In other words a 108" rollout tire needs to spin say 10% faster than that 108". To fast and you lose to much traction and slow down , to slow and tire shake may develope because the tire is biting so hard that the sidewalls start buckling and then the tread starts bouncing!! At some point with my limited amount of power the tire does eventually hook up 1 to 1 with the ground , thats where you see the DS speed get slower. This is natural!!

See attached pics of data. Red is RPM , green is drive shaft , blue is acceleration. At .4 you can see the acceleration falling off as the DS speed increses. This is to much tire speed but the tires recovered!! At .512 you can see the acceleration go to the max as the tires are hooking up to the ground thus the DS speed is falling. A perfect launch would have the acceleration go up up in a steady rise to a point and then start back down gradually. I have never been able to accomplish that. Im not sure it even possible to without traction control!!! Mike

 

[Alky V6]

Typically, to get the sim to match a timeslip, there has to be some tire slip. Like Mike said, some degree of tire slip is natural to have in the run.

Very interesting stuff Mike. Thanks for taking the time to post the pics and explain. It sure shows the value of having a thorough datalogger system.

 

[Blazer406]

Maybe using the g-force at each datapoint is the way to do it in this case.....

It might be more accurate.....just didn't know how accurate that g-number is.... I would expect the distance traveled to drop using the g-force to calculate it....

Give me the g-force number at each of the time stamps you had in the last data you gave me....