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Question for those who launch in 4-hi

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Old 04-16-2018, 05:12 PM
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Originally Posted by DurantECOBOAST16 View Post
Why 4H instead of 4A?
Not all trucks have 4A...

Originally Posted by DurantECOBOAST16 View Post
I couldnt launch any harder than 2750RPM in 4A. I wonder if 4H would make a difference in that regard.
Are you still using the stock converter? If so that is most likely the reason, mine only does around 2700 (in 4H though, mine doesn't have 4A)...

Originally Posted by DeeMiniioon View Post
I've done 3500 launches in 4hi and she doesnt like them that much especially at the track computer cuts power, but from testing i've had my best 60' and times launching at 1k and just letting converter flash then actually loading her up. If there was anyway to remove watever is limiting or cutting power on hard launches it would be a big difference since it was a pretty violent launch i'm guessing thats why computer killed it.
Interesting, (sorry to ask, but everyone forgets occasionally, I know I have) are you turning off traction control? I've definitely gotten my best 60's by brake torquing to ~2700. If you have any way of logging see what your torque source is doing when you get limited.
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Old 04-16-2018, 05:24 PM
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My launches at 3500+ were with traction control off. Power cut was just like letting off the throttle.
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Old 04-16-2018, 05:32 PM
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Originally Posted by Scott91370 View Post
My launches at 3500+ were with traction control off. Power cut was just like letting off the throttle.
What mods do you have?
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Old 04-16-2018, 05:34 PM
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Just a Tune and Full Race inter-cooler.
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Old 04-16-2018, 07:02 PM
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Originally Posted by yonson View Post

Interesting, (sorry to ask, but everyone forgets occasionally, I know I have) are you turning off traction control? I've definitely gotten my best 60's by brake torquing to ~2700. If you have any way of logging see what your torque source is doing when you get limited.
I always turn it off completely, and I'm sure it reaching a tq limit somewhere due to it hooking at the track since the same launch in the street doesn't get shut down but then again in the street it does spin a little so i'm pretty sure its tuning related.
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Old 04-17-2018, 02:29 AM
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Originally Posted by Scott91370 View Post
I wouldn't try 4A because the IWE aren't engaged and trying to get them to engage them under stress might not be a good idea.
I made a few runs a couple weeks ago and anything over 3500rpm and the truck would nosedive after about 10 feet. Not sure if it is traction control or what but my 60' times were 2.5X. Found the sweet spot on mine is 2500-2700 and that gets me 1.9 in the 60'.
Is your truck stock if so what does it run in the 1/4 mile I assume 3.5L Eco Boost?Never mind I read further and seen it's not stock!!!
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Old 04-17-2018, 09:12 AM
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Stock in the 1/8 mile it was running 9.33 @ 72. After the turn it is doing 8.98 @ 77 and 14.1 in the quarter (forgot the mph).
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Old 04-17-2018, 09:30 AM
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Originally Posted by Scott91370 View Post
I wouldn't try 4A because the IWE aren't engaged and trying to get them to engage them under stress might not be a good idea.
In 4A, the IWEs "are" engaged, and the TC transfers power back and forth as required. Likely be better off in 4H anyway, since the power will be split 50/50, instead of whatever the TC electronics want to do.
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Old 04-17-2018, 07:09 PM
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Originally Posted by swampvol View Post
Do you keep it in 4-hi the entire run, or shift into 2wd shortly after the launch?
Leave it in 4WD the whole way. I don't even want it trying to shift or disengage anything at WOT with nitrous flowing. Probably less strain on the axles anyhow as torque is split over twice as many parts....

Originally Posted by Scott91370 View Post
I wouldn't try 4A because the IWE aren't engaged and trying to get them to engage them under stress might not be a good idea.
I made a few runs a couple weeks ago and anything over 3500rpm and the truck would nosedive after about 10 feet. Not sure if it is traction control or what but my 60' times were 2.5X. Found the sweet spot on mine is 2500-2700 and that gets me 1.9 in the 60'.
My best runs are brake torqued to about 1800, and then let the converter flash on the nitrous hit. Previously nitrous engaged at 1900 / 70%,

Originally Posted by DeeMiniioon View Post
I've done 3500 launches in 4hi and she doesnt like them that much especially at the track computer cuts power, but from testing i've had my best 60' and times launching at 1k and just letting converter flash then actually loading her up. If there was anyway to remove watever is limiting or cutting power on hard launches it would be a big difference since it was a pretty violent launch i'm guessing thats why computer killed it.
I find that sometimes it launches great with a full brake torqued (2500rpm) start, but usually the rpm dips a little (No Nos), fastest NN launch is about 2000rpm, then floor it as I let off the brake, if it flashes to 2600, it launches mint. On Nos, well, it really just doesn't matter lol. I just torque it up to around 2K, and as soon as the pedal is floored, 600ft/lbs hits and it gets out!

Originally Posted by johnday View Post
In 4A, the IWEs "are" engaged, and the TC transfers power back and forth as required. Likely be better off in 4H anyway, since the power will be split 50/50, instead of whatever the TC electronics want to do.
Yep - Take the TC clutch out of the equation completely, for any number of reasons.
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Old 04-17-2018, 10:22 PM
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Originally Posted by isthatahemi View Post
I find that sometimes it launches great with a full brake torqued (2500rpm) start, but usually the rpm dips a little (No Nos), fastest NN launch is about 2000rpm, then floor it as I let off the brake, if it flashes to 2600, it launches mint. On Nos, well, it really just doesn't matter lol. I just torque it up to around 2K, and as soon as the pedal is floored, 600ft/lbs hits and it gets out!.
Mine was the same on stock tq converter it loved to be fully loaded up, but after the stall it launches way differently my best times are at 1k and let it flash on it own close to 4k.
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