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psychoRT
Dodge Dakota
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4/13/2002
06:22:49
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 Subject: Test the new computer out !
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Message:
Well went out and finally got to test the new computer. Somthing is terrible wrong, with the old fu*ked up computer i ran a 9.687 and with the new computer i ran a 9.678 somthing is messing up and dont know what. I did forget to reset the pcm before i raced but that shouldnt make that big of a diff. 60' was badass got some 2.1's and the truck was hooking. im loosing somthing somewhere and when i manually shift the truck at around 5300 and on time at about 5500 i lost a tenth of a second it went to 9.778 but i got the 9.6 when i left it in drive.
Anyone heard of this, with the computer and the problems i was having with the old one i should have gotten atleast 3 to 4 tenths off my time.
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Aaro
Dodge Dakota
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4/13/2002
08:01:39
|  RE: Test the new computer out !
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Was the outside air temp the same for the two runs ? 30 deg. can make a big change in your times, my truck 1/4 mile time is .3 -.4 faster at 45deg than it is at 75deg. One more thing if it is a 5.2 or 5.9 with the stock cam and valve springs you should shift at about 5100 rpm or sooner, the valves start to float at about 5300 rpm.
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psychoRT
Dodge Dakota
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4/13/2002
14:03:04
| RE: Test the new computer out !
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It's a 98 r/t. outside air temp about the same if anything 15 20 degrees diff. That is one thing i was worried about also if when im manually shifting the truck is droping off. does anyone know what the intake manifold drops off at, and the exact time the vavles start to float i have heard diff. rpm ranges.
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bernd
*GenIII*
4/13/2002
14:19:12
| RE: Test the new computer out !
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If you're manually shifting (as in 1st to 2nd to Drive), you'll run slower as the reverse band in the transmission is still engaged from the 1-2 shift (manual shifts only). This is a known "feature" on the 727/904 (and derivatives - 500/518, 42/44/46 series). Turn OD off, leave it in "D", and let the transmission do the work. (If you do want to shift manually, switch from 1st to 2nd at no more than 2500rpm and/or below 15mph). It will still stay in 1st until it has to shift.
There also no need to rev the motor beyond 5000-5100 as the power drops off at 4800-4900rpm). This is cam/head dependent as different cam/head combos will move the powerband up or down.
1997 Dodge Dakota SLT - V6
Supercharged/Intercooled @ 10# w/Nitrous
14.55 @ 96.01mph
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Hersbird
Dodge Dakota
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4/13/2002
20:18:26
| RE: Test the new computer out !
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I'm not so sure about turning the OD off. My truck won't shift into overdrive in a 1/4 mile with the button in the normal posisition, but when I turn the OD off it lets the torque converter lock up in 3rd gear a little after it shifts. This lockup hurts maximum power a bit. I don't know if it kills times but I would leave the OD on, or the way it is when you start the truck, just in case. The torque converter doesn't lock up in 3rd with the OD on. To compare the difference in the computer you really need to do runs in the same way. Back to back wouldn't be that hard as the things changes out in 5 minutes, but at least run the same way. I'd say my PCM helps a lot, and the 5200 rpm shift with it in drive gives a good bark on the 1-2 where there was none before. I would never expect .3 to .4 on just the computer in the 1/8 mile. Maybe .3 in the 1/4 mile but .4 in the 1/8 would take over 50 HP.
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psychoRT
Dodge Dakota
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4/14/2002
02:57:43
| RE: Test the new computer out !
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I think it was the lasers they were messing with them all night. im going to go to another track sunday and see whats up if i have a chance. I was expecting that amount of time though because of the old computer messing up on me and the power lose. The dude that had the truck before me ran 9.3's constantly. But when i finally got it had worn out r rated tires and then added the ptm wheich messed up the tranny but i still got 9.6 out of it. so will see at another track.
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KenDawg
Dodge Dakota
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4/14/2002
10:58:32
| RE: Test the new computer out !
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Jeez's are you talking 9's in the 1/4 mile? If so what engine mods do you have?!?
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bernd
*GenIII*
4/14/2002
12:37:20
| RE: Test the new computer out !
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Here's what I mean about the 1-2 manual shifing bog:
When you shift manually from 1st to 2nd, you'll notice that it bogs a little bit but doesn't if you leave it in "D". That bog is the Low/Reverse band taking too long to release as the 2nd gear band is applying. This can be fixed with larger (More Powerful) Low Reverse Piston Spring and a piston Movement limiting shim. It's an age old "feature back to the 727/904.
Hersbird: On modified engines making more than 325-350HP, you want the lockup to engage to prevent slippage. That's the reason for leaving the OD off. (Supercharged and/or nitroused engines mainly.)
1997 Dodge Dakota SLT - V6
Supercharged/Intercooled @ 10# w/Nitrous
14.55 @ 96.01mph
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Hersbird
Dodge Dakota
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4/14/2002
18:29:37
| RE: Test the new computer out !
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No matter what the motors power, there will be a torque multiplication effect if the torque converter IS slipping and NOT locked up. If the motor is spinning at 4300 RPM and the driveline at 4000 RPM then you are actually getting a 7% increase in torque. It doesn't matter if the motor is making 500 ft-lbs or 200 ft-lbs its 7% more with the slipping. This is assuming you can finish the 1/4 mile w/o it having to shift into overdrive. The only time I could think of that you'd want the lockup in 3rd is if you need that extra 300 rpm to keep it from shifting into overdrive. The lockup feature is only to prevent heat biuldup in the transmission and extend the life of it, not give any extra power. Every serious automatic drag racers I've ever heard of don't even use a lockup torque converter, even though it would be an easy mod to make if it did improve times. Honestly I doubt it really hurts or help times much either way on the Dakota, but it sure feels more like a bog then a surge of power to me. I agree don't shift 1-2 manually, I say don't do the 2-3 manually either, as letting the PCM and valve body do it will give more consistant results.
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