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 Post subject: High Gear Only?
 Post Posted: Thu Sep 03, 2009 9:02 am 
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This thread is a continuation of the hijack of the oobob win thread in the "General Topics" section where we started talking about the high gear only trend in bracket racing.

Mark what I'll probably do is like Barry's buddy and just make the shift just after the hit and see how it goes. My driveshaft graph is showing tire spin all the way thru low gear and part way into high gear depending on how many passes have been made on the race track. Track conditions have a lot to do with it though as it does get better when more cars are running.

I've got 8 clutches in my high gear drum and also I have a commercial heat exchanger that uses the radiator to cool the tranny. I'm also logging trans fluid temp so I can see how hot it really gets while it's "on the verter". I can see that if this works then that 5.43 gear I ran last year might be benificial. Might could even use a 5.57? I got a 5.14 in it now with a 100" roll out tire.

One other note here, I'd be willing to bet that you could run a stock 1.82 planetary with the high gear only deal as there wouldn't be that much of a problem with the shock load at the gear change. Most of the planetaries I've broken have been at the gear change. Hummmmm...........................

We're testing tomorrow night and I'll use my last pass to see how this shakes out. Data to follow! ;-)

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 Post subject: Re: High Gear Only?
 Post Posted: Thu Sep 03, 2009 9:15 am 
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B&M did that years back with a blown BBC dragster. They built a custom glide valve body that allowed for the trans brake to apply in high gear, which is not too hard to route in a valve body. You would want to rig a safety circuit, possibly using two switches to apply to keep from hitting it down track.


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 Post subject: Re: High Gear Only?
 Post Posted: Thu Sep 03, 2009 10:04 am 
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If memory serves, I think my K&R box has a feature built into it for that? I'd have to go back and read the instructions again but I seem to remember that being a feature they put in it.

And yeah, this isn't the first time I ever heard of this either. Just wasn't sure how well it works for a bracket car.

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 Post subject: Re: High Gear Only?
 Post Posted: Thu Sep 03, 2009 1:07 pm 
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Most delay boxes have an adjustable lockout feature that can be programmed for a set amount of time so there's no chance of locking the car up down track. This would be a must have with a H/G transbrake.

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 Post subject: Re: High Gear Only?
 Post Posted: Fri Sep 04, 2009 10:31 pm 
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I did make one pass tonight with the gear change happening within like .5 seconds after the Transbrake release. Interestingly enough the transmission temperature DID NOT GO ANY HIGHER THAN USUAL???? That damn thing was "on the converter" the better part of what seemed like half the run and it still didn't over heat the fluid??? Only ran a 6.05 @ 121 and change on that pass and was a REAL funny feeling too? I'll post a graph image of this engine and driveshaft RPM sometime in the next day or two.

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 Post subject: Re: High Gear Only?
 Post Posted: Sat Sep 05, 2009 7:44 am 
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What is you normal ET?

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 Post subject: Re: High Gear Only?
 Post Posted: Sat Sep 05, 2009 8:47 am 
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want-a-be wrote:
What is you normal ET?


We ran two 5.69s @ 123.7x before that short shift high gear pass.

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 Post subject: Re: High Gear Only?
 Post Posted: Sat Sep 05, 2009 4:42 pm 
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The yellow line is the transbrake release. The upper blue line is engine RPM. The Brown line is driveshaft RPM. The blue line with the downward spike at the hit is transmission pressure and shows when the low/high shift was made and the other blue line that runs parallel to it is transmission fluid temperature in the pan.

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 Post subject: Re: High Gear Only?
 Post Posted: Mon Sep 07, 2009 10:55 am 
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I just spoke to my trans guy about doing this today, most shift at 2 tenths out and go from there. He has one of his car setup to shift right away but delay is way different there. I plan to try it this year sometime, I like the idea of 8.50@175 =;

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 Post subject: Re: High Gear Only?
 Post Posted: Mon Sep 07, 2009 11:04 am 
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Looking at that log again I noticed that the shift actually occured quicker than I had stated in my original post. Looks like it was about .3 or so judging from the times listed at the bottom of the graph, which are seconds into the log.

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 Post subject: Re: High Gear Only?
 Post Posted: Mon Sep 07, 2009 12:12 pm 
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A little off topic but could someone in plain English, no puter talk, how to post a graph from a logger.....PIA to try to take a picture and then load it and post it...Thanks

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 Post subject: Re: High Gear Only?
 Post Posted: Mon Sep 07, 2009 12:57 pm 
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Beretta wrote:
A little off topic but could someone in plain English, no puter talk, how to post a graph from a logger.....PIA to try to take a picture and then load it and post it...Thanks


Get the graph where you want it Barry and then take a screenshot. George posted a link to screenshot software some time back and I have been using it. http://www.snapfiles.com/get/mwsnap.html There are other ways but MW snap is a neat tool. If you need help using it let me know.

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 Post subject: Re: High Gear Only?
 Post Posted: Mon Sep 07, 2009 9:17 pm 
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Beretta wrote:
A little off topic but could someone in plain English, no puter talk, how to post a graph from a logger.....PIA to try to take a picture and then load it and post it...Thanks


Barry,
To do a screenshot in Windows, just hold down the <ALT> key and press the <Print Scrn> key and the currently active window will get "screenshot" into the copy buffer. Open MS Paint and paste it into a blank canvas, then you can save the screenshot from Paint as a .jpg file.

If you want the entire screen (all windows just as desktop appears) use <CTRL> then <Print Scrn>.

Really easy once you know how.

Rick


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 Post subject: Re: High Gear Only?
 Post Posted: Mon Sep 07, 2009 9:23 pm 
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One thing about the high-gear only thing is the time spent on the converter increases a lot, as Ken's graph shows. Stall speed becomes more important than ever if you are going to do this. If its under-convertered it will be less consistent with the high gear only or short-shifting high. For consistency, over-converter (ie more stall than best ET).

Rick


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