[Mr. 5]

Sacramento Raceway is a great place to run because the conditions are so nice, but I really wish the people that are in charge of the timing would get their heads out of their rear ends.

The first time I went to Sacramento, I ran the best trap I have ever run and it was on the GIAC daily driving map. I ran a 118.6 MPH.
This trap speed was about 1.5 MPH higher than the VBOX MPH.

For those who don't know, the trap speed on a slip is the average speed between the time at the 1/4 (1320') and 60' before the 1/4 (1260).
The trap speed from the VBOX is the actual speed right at the 1/4 mark, so if you are accelerating then how can an average of the last 60 ft be higher than the instantaneous speed? It can't.
Below is my time slip from the first time i went.



I went back last week and was curious if anything has changed because I haven't heard anything new from that track.
It looks like someone tried to fix the issue and made it wrong again.
Here's the thing that I noticed...

The first time I went there, I looked at the timing boxes.
There was a dark spot just before the 1260 box so it looked like the box was moved up a foot. It made me wonder if they were dividing by 60 when they should have been dividing by 59.

Anyways, when I went there this time, the 1260 box was 2 ft before the dark spot by the 1260 mark. This would mean that if they are still dividing by 60 then they should be dividing by 62.

Why do I think that the traps are under inflated now?
Because I was able to run an 11.88 at 113 MPH.
113?? You've got to be kidding me!

I did a VBOX log of each run (except run 4) and you can see how different each trap is.
Now, the trap speed of the slip is about 2.6 MPH slower than the VBOX.
Look at run 5. The VBOX read 3.6 mph higher than the trap.

You would think that somebody over there would get this straightened out!

[roninsoldier83]

That's a hell of a variation!

On a somewhat unrelated note, I had a quick question for you. I'm assuming at that power level, with the numerous drag strip passes you've made, that you're no longer running the stock clutch, correct? If so, at what point did the stock clutch start to give out? I'm just curious about how much abuse, and at what power/torque level the stocker can hold up to.

I'm assuming based on your 60 ft times that you're running drag radials, and launching fairly aggressively... any drivetrain issues to speak of?

[Jeff@TopGearSolutions]

Well its one thing that its wrong, its another if anyone is actually telling them?

They get paid when you show up, not what you run and not how accurate it is

[hotrod182]

Can't believe they would let something like this go for more than a day without someone complaining.

I was analyzing your data from the track and noticed once you figured out what the difference was between the track and the vbox was, the deviation from the difference was amazingly little.

Once you establish that the right lane was about about 2.8 mph slower than the Vbox, the variance from the difference was only about .035mph/.048 seconds. That is incredible consistency!

However, the left lane seemed to vary more. Which is what I discovered when I was up there too. Variance rose to about .972 mph, and .159 sec, unless you took out the one outliner, then the results would be very consistent. I believe there may be something in the equipment up there between the lanes even. The Vbox is accurate enough to make the lane to lane variance apparent at times.

And for all the doubters on Vbox qtr mile times....not one of these runs on the Vbox read QUICKER than the track slip..which is something I usually notice when running my Vbox also. So the Vbox is hardly ever optimistic on ET or 60' times.

Hopefully the next time someone runs at Sacramento, they will bring and post their Vbox times for confirmation, and to let us know how their equipment calibration stands.

FYI: Around this time last year, Sac was reading 2.7mph faster than the vbox instead of 2.8mph slower than the Vbox. So compared to last week, the traps then were a whopping 5mph faster! Which makes sense of why Mr. 5 ran 118mph before, and only 113mph now with a likely faster car!

Until they get it figured out, I think I will stick with my Vbox runs for now. At least it is consistent, even though the track may not be.

[skinrock]

Originally Posted by Mr. 5

For those who don't know, the trap speed on a slip is the average speed between the time at the 1/4 (1320') and 60' before the 1/4 (1260).
The trap speed from the VBOX is the actual speed right at the 1/4 mark, so if you are accelerating then how can an average of the last 60 ft be less than the instantaneous speed? It can't.

I'm probably missing something, but if the trap speed is an average of the remaining 60 feet, why wouldn't it be slower than the speed at the actual 1/4 mile?

If you hit 115 at 1260 and trap (VBOX) at 117, the average would be 116, no?

[Clap135]

I still vote for all the records to me be removed if they ran at SAC, track is complete bullshit.

[hotrod182]

Originally Posted by Clap135

I still vote for all the records to me be removed if they ran at SAC, track is complete bullshit.

Well the ET is correct, so the rankings would still be correct anyways. But I ran 123mph on my Vbox last week. If it had been run this time last year, I would be running right at the record trap speeds for a 335i. And it makes sense, I am running 11.7s with a lousy 1.9 60 foot time. But seriously, some of these tracks where the highest trap speeds are coming from, I wish people would take a Vbox with them and post the screen shot. I have a feeling some track might vary more than you would think.

[Clap135]

Originally Posted by hotrod182

Well the ET is correct, so the rankings would still be correct anyways. But I ran 123mph on my Vbox last week. If it had been run this time last year, I would run running right at the record trap speeds for a 335i. And it makes sense, I am running 11.7s with a lousy 1.9 60 foot time. But seriously, some of these tracks where the highest trap speeds are coming from, I wish people would take a Vbox with them and post the screen shot. I have a feeling some track might vary more than you would think.

Well I am not arguing the ETs, just the trap speeds. They are simply unrealistic. All the trap speed records come from the same track which has a screwed up timing system as vertified by many people from many different forums. I think the top 13-14 335i times are all from the same track. Ironic much?

Hell a bone stock 2011 automatic mustang 5.0 hit 115mph there....give me a break.

[Mr. 5]

Originally Posted by skinrock

I'm probably missing something, but if the trap speed is an average of the remaining 60 feet, why wouldn't it be slower than the speed at the actual 1/4 mile?

If you hit 115 at 1260 and trap (VBOX) at 117, the average would be 116, no?

That's exactly what I am saying.
This is the reason why my 118.6 trap that i had on the first slip is wrong.
There's no way that I was able to run an average of 118 during the last 60 ft when my Vbox said that my speed right at the 1/4 was 116.

Sac finally realized or maybe I should say...They finally tried to fix the over inflated traps, but it's like someone said, "Well, let's see what the times would be if we move this box over here."

The way that these traps read now are completely oposite.
Now, the traps read incredibly low.

[Mr. 5]

Hey, I just figured out that I have the quickest 335 with the lowest trap!
It's all about the driver.

[Syndicategt]

I'll be heading there this Wed for some fun. Let me know if you are down to make the drive again. Weather is going to be great!

[skinrock]

Originally Posted by Mr. 5

That's exactly what I am saying.
This is the reason why my 118.6 trap that i had on the first slip is wrong.
There's no way that I was able to run an average of 118 during the last 60 ft when my Vbox said that my speed right at the 1/4 was 116.

Sac finally realized or maybe I should say...They finally tried to fix the over inflated traps, but it's like someone said, "Well, let's see what the times would be if we move this box over here."

The way that these traps read now are completely oposite.
Now, the traps read incredibly low.

Well you said there was no way for the average to be less than the instantaneous. I assume now you meant "higher".

Is there anyway to get VBOX to record the speed at the last 60 feet? The best acceleration I could figure is 0.034 mph/feet for the last ~220 feet on runs 1 and 2, which equates to roughly 2 mph slower at the 60 feet, which means your slip trap aka average should be about 1 mph slower than your VBOX trap.

That's not assuming any increase in acceleration, though, and I assume there would be an increase from -220 feet to -60 feet. Although it only increased from 0.031 from the ~780 foot marker so the acceleration is probably minimal.

Anyways, my point is, it would be nice to have VBOX record exactly what it should be and show the guys at the track.

[Mr. 5]

Originally Posted by skinrock

Well you said there was no way for the average to be less than the instantaneous. I assume now you meant "higher".

Is there anyway to get VBOX to record the speed at the last 60 feet? The best acceleration I could figure is 0.034 mph/feet for the last ~220 feet on runs 1 and 2, which equates to roughly 2 mph slower at the 60 feet, which means your slip trap aka average should be about 1 mph slower than your VBOX trap.

That's not assuming any increase in acceleration, though, and I assume there would be an increase from -220 feet to -60 feet. Although it only increased from 0.031 from the ~780 foot marker so the acceleration is probably minimal.

Anyways, my point is, it would be nice to have VBOX record exactly what it should be and show the guys at the track.

Oh, you're right. I edited the first post.

Yes, you can do the average.
All you need to do is graph it out using the VBOX software and take the time from the 1260 mark and the 1/4 mile time and then divide by 60.
This will give you ft/sec and then you need to convert to MPH.

The VBOX records everything you want. You as a user just need to play with it.

[tmo335tt]

Originally Posted by Syndicategt

I'll be heading there this Wed for some fun. Let me know if you are down to make the drive again. Weather is going to be great!

I'll be there again

[hotrod182]

Originally Posted by skinrock

Well you said there was no way for the average to be less than the instantaneous. I assume now you meant "higher".

Is there anyway to get VBOX to record the speed at the last 60 feet? The best acceleration I could figure is 0.034 mph/feet for the last ~220 feet on runs 1 and 2, which equates to roughly 2 mph slower at the 60 feet, which means your slip trap aka average should be about 1 mph slower than your VBOX trap.

That's not assuming any increase in acceleration, though, and I assume there would be an increase from -220 feet to -60 feet. Although it only increased from 0.031 from the ~780 foot marker so the acceleration is probably minimal.

Anyways, my point is, it would be nice to have VBOX record exactly what it should be and show the guys at the track.

You are right, the trap should be approx 1mph slower than the Vbox reading from my experience. (For cars in our trap speed range). Famoso is 1mph slower. Sacramento used to be .5mph slower about 2yrs ago, but was 2.7mph faster earlier last year. A huge difference. And now suddenly its 2.8mph slower!

Really, a better way of checking out a cars acceleration potential is the popular 60-130mph test. This takes traction, surface prep, tires, LSD, etc out of the equation. Hopefully we can get some more 60-130 results from other E90 post member's BMWs with various stages of modifications. With our cars, I have found to run around 9 flat, your car would probably be trapping well over 120mph. If you are in the sixes, you have a car that is capable of over 130mph traps.

Guys...post your results. Its a sticky located at the top of this forum section:

http://www.e90post.com/forums/showthread.php?t=477054