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Change gears or change shift points?

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Old Jul 18, 2010 | 05:46 PM
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Default Change gears or change shift points?

I have been running my car through the 1/8mile to work on the launch and save the nitrous for more runs and tuning. Well I finally took my car through the 1/4 and I ran out of gear before the traps. My nitrous cuts off at 6400rpm, the car shifts at 6600rpm. So at the top of the track my nitrous was off and I hit the limiter at 6800. Should I change my gears or move my shift points up to 6800rpm and have my nitrous shut off at 66-6700rpm? Mods are in my sig. 3:90 gear with a 28"tall Drag Radial in the back, 150 shot, 3600 stall. Thanks for the help!
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Old Jul 18, 2010 | 06:20 PM
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Need more info.
Did your car hit the limiter around the 1000', or right at the very end.
Are you on a stock a-4? Could it be slipping up top?
What cam/spring set up do you have?
You may be very close to the rpm limit already.
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Old Jul 18, 2010 | 06:52 PM
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Originally Posted by dannyz
Need more info.
Did your car hit the limiter around the 1000', or right at the very end.
Are you on a stock a-4? Could it be slipping up top?
What cam/spring set up do you have?
You may be very close to the rpm limit already.
Honestly not sure, probably in between the two, the nitrous cut off a ways back, but the limiter hit a little before the end.
No its a built 4l60e. Its not slipping any.
I have a TSP MS4(239/242@.50, 649 lift) cam with PRC dual springs.
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Old Jul 18, 2010 | 10:44 PM
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In that case I would say gears.
If you are running a decent stall, and I believe you are, you won't be giving up anything on your launch, and you will be able to stay on the pedal till the end.
You probably will be able to stay on the nitrous threw the traps as well, which means you will still be accelerating and thus an even better et.
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Old Jul 18, 2010 | 11:39 PM
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How much is the converter slipping? Seems like if you are cutting the nitrous off early, you are leaving something on the table.
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Old Jul 19, 2010 | 06:26 PM
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I dont know what the slippage is on the converter, or how to find out. The nitrous cuts off at 6400rpm no matter what gear, its what the window switch is set for, in third gear I'm just going way past that rpm because I have to short of a gear. I just figured since its pretty close to the end of the track, maybe I could just stretch out the shift points a little more and save some money. But I wont do it if its unsafe, I will just get some different gears if need be.
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Old Jul 19, 2010 | 07:04 PM
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put a set of rod bolts in it and spin the engine 7K if it will still make some power there. set the limiter to 72-73 and cut the N2O at 69-6950. got a shift light? consistency is gonna be important with your rpm tolerances here.
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Old Jul 19, 2010 | 07:28 PM
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Originally Posted by ssvert99
put a set of rod bolts in it and spin the engine 7K if it will still make some power there. set the limiter to 72-73 and cut the N2O at 69-6950. got a shift light? consistency is gonna be important with your rpm tolerances here.
Yeah I hear ya, I've just REALLY been dreading those rod bolts. Thats a huge pain to do, I may let RPM handle that one lol. But I do think with the size cam I have it will continue to make power at that rpm. So you dont think a set of 3:73's would be a better choice?
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Old Jul 19, 2010 | 10:22 PM
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Originally Posted by second_2_none
Yeah I hear ya, I've just REALLY been dreading those rod bolts. Thats a huge pain to do, I may let RPM handle that one lol. But I do think with the size cam I have it will continue to make power at that rpm. So you dont think a set of 3:73's would be a better choice?
I myself would do the gears.
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