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Organized Drag Racing and Autocross Drag racing and autocross discussions and questions. Techniques, tips, suggestions, and "what will I run?" questions.

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Old 05-11-2008, 06:19 PM   #1
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Join Date: Jul 1999
Location: 51°N 114°W, 3500'
Posts: 11,673
Car: 87 IROC L98
Engine: 540 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86

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Throttle stop installed

I don't plan on using it for controlling the down track ET but I will be using it as a starting line enhancer. The throttle stop is controlled by CO2. When the CO2 is turned on, the cylinder keeps the throttle rod short. When the CO2 is released, the return springs pull the rod out of the cylinder increasing the throttle rod length. I also had to fabricate a stop on the pedal so when the linkage is at WOT, the pedal won't go down any more.

My delay box has a starting line enhancer feature. How it works is just before I stage, I push what's called a bump button (haven't installed it yet). This releases the CO2 from the cylinder and lengthens the linkage. I can now push the throttle to the floor and I'm basically at an idle or whatever RPM I adjust the linkage to. I then stage the car, push the transbrake button and my foot is to the floor at an idle. When I see the first flicker of the top bulb, I let go of the transbrake button. .8 of a second before the transbrake releases, the throttle stop fills with CO2, shortening the linkage and slams the throttle to WOT. It can either be at full stall speed or bouncing off a 2 step at this point and will only be for .8 of a second.

I can set it a couple of other ways but feel this will be the best. I can also use a 4 stage timer in the delay box to drop the throttle back for a preset time to slow the car down. If I decide to try super class racing, I can do it.

As soon as the air shifter control solenoid arrives, I can hook up my air shifter. I'll have to use an rpm switch to control the shifter. I'd need a second 4 stage timer to shift by time which my delay box doesn't have.

As an emergency backup, if I'm out of CO2, I have another throttle rod made up the same length but without the air cylinder. That way I can still operate the throttle as normal.

This is going to be a fun season!





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Old 05-12-2008, 12:20 AM   #2
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Location: North Ga.
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Car: 1987 Camaro
Engine: 406
Transmission: Powerglide
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Re: Throttle stop installed

Those work really well when bracket racing and your the faster car crossing over. Most boxes will adjust the time to come on if your crossing over that way the car gets on the 2 step the same time everytime when your side of the tree is coming down. Our track uses crosstalk and it makes it hard to get on the pedal being the last to leave because when the tree comes on, both top yellows on each side comes on, the slower cars side comes down normal, but the fasters cars top light stays on for whatever the dial in difference is, then drops on down.
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Old 05-12-2008, 01:01 AM   #3
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Join Date: Jul 1999
Location: 51°N 114°W, 3500'
Posts: 11,673
Car: 87 IROC L98
Engine: 540 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86

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Re: Throttle stop installed

That would suck if you don't use a crossover. My delay box allows 2 hits at the tree but our track shields the yellows in all classes so I can't see the other side anyway. I can also install a bypass button. If I miss the top yellow, I can hit the bypass and leave off the bottom bulb so technically I can have 3 hits at the tree.

Ahh the joys of electronics racing.
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Old 05-12-2008, 05:36 PM   #4
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Re: Throttle stop installed

I think I'll just stick with footbrakin'. But it is hard to deny the electronics guys are all over it.....most of our big $$ runs have a box-no/box showdown. So needless to say we are pretty much playing from behind in the final.
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Old 05-12-2008, 07:49 PM   #5
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Join Date: Jul 1999
Location: 51°N 114°W, 3500'
Posts: 11,673
Car: 87 IROC L98
Engine: 540 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86

Classifieds Rating: (0)
Re: Throttle stop installed

There are box and no-box racers who are hard to beat. A delay box or throttle stop won't make you a better racer but it does add a bit of consistency and a little more automation.

I like the fact that I can leave off the top bulb. Humans are terrible timing devices and watching the lights come down and trying to time that last yellow is hard especially with LED bulbs. If I red light, I can add more delay until I can't red light any more. If I miss the light and I'm late, I know I was asleep.

Using the throttle stop as a SLE, the engine isn't banging off the 2-step for 2-5 seconds as I wait for the tree to activate. Makes it easier on bearings. I can also set the throttle stop to adjust the throttle to my launch rpm. Push the bump button, pedal drops so the throttle pedal travel only gives enough rpm for a launch rpm like a 2-step but isn't bouncing off the limiter. When the transbrake releases, the throttle goes to WOT at the same time. This is one of the other setting options I could use. Doing it this way, once I'm staged, I can sit at the launch rpm for as long as I want. I could even set it to go to WOT a fraction of a second before the transbrake releases if I don't want the converter to flash when I launch.

Like any other device installed on a car, they're tuning aids.

As for the shifter, I'd love to have it shift on time. Shifting on time is more accurate than shifting on RPM. Since bracket racing is done by time anything that makes it more consistent will help.
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114w, 3500, 51n, alcohol, box, cheating, delay, drag, dragracing, hook, racing, running, stop, street, throttle, throttlestop
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