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Wife's mad I spend $$$$$$
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Discussion Starter #1
I've got the latest 150HP tune and I'm loving it a lot.

Going to Sacramento Raceway with my HTC (Hemi Truck Club) friends and family.

I've raced my Hemi with mods at [email protected] real consistant.

I'm hoping to hit into a 13 with the new truck. I know I need to launch in 4 wheel drive. My question is what RPM should I stall the truck up to make for the best launch out of the hole?
 

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I've got the latest 150HP tune and I'm loving it a lot.

Going to Sacramento Raceway with my HTC (Hemi Truck Club) friends and family.

I've raced my Hemi with mods at [email protected] real consistant.

I'm hoping to hit into a 13 with the new truck. I know I need to launch in 4 wheel drive. My question is what RPM should I stall the truck up to make for the best launch out of the hole?
I haven't looked at RPM. I usually look at boost. It's probably not the right thing to do, but it's all I look at. I have launched with anywhere between 15 psi to 25 psi. The problem with launching with 25 is that it is too violent and I get too much weight transferred off the front wheels. They spin slightly and cause drivetrain twisting. This results in a lot of jerking for a bit. With 20 psi, it is still a hard launch, but smooth. I'm not a diesel drag racer, but I think the goal would be to launch with as much boost as you can and still have it be smooth. It will really depend on your suspension/tire setup and how hard you want to thrash your transmission.
 

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Wife's mad I spend $$$$$$
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Discussion Starter #3
I'm not going to be drag racing it all the time. It's my do everything truck. So I won't be wanting to thrash the transmission. I understand what you're saying. I want to say I read some where someone was suggesting to launch at 1500 rpm. Not sure though.
 

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With the stock tranny you should look at no more than 10 to 12 psi boost. RPM's are irrelevant for drag racing a turbo diesel. Regardless you will degrade your drive train just doing one run.
 

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i had 40000 on my last truck, and it seen daily launches, sometimes multiple times. the tranny never gave me any signs of failing.... 4wd high, stall to 20psi, and let it fly. i selected 4th manually, and with 4.10's it got there fairly quick , then hit 5, and 6 right at 1100 feet. stock truck / smarty tuned, went 13.2 at 104
 

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Wife's mad I spend $$$$$$
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Discussion Starter #7
Awesome guys, I appreciate the advice.
 

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Wife's mad I spend $$$$$$
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1,626 Posts
Discussion Starter #8
I tried no boost first, not on purpose, and was pleased.
1.943 60ft
[email protected] 1/8
[email protected] 1/4

2nd run with 15psi (a bit of wheel hop)
1.983 60ft
[email protected] 1/8
[email protected]

3rd run wit 20psi (lots of wheel hop) also shed 218lbs(took the wife out)
2.032 60ft
[email protected] 1/8
[email protected] 1/4

4th run 13psi (wife out again) launched a lot better with no wheel hop
1.932 60ft
[email protected] 1/6
[email protected]


Fastest ever in my heavily modded track prepped Hemi was 14.170 with slicks and all. The Cummins I drove up off the street and went. So in my eyes street for street my new Cummins is faster all around then the Hemi ever was.

Now to try and get into 13's. The truck pulled wicked hard all the way town. I'm still on the stock tires with 4.10 gears. I think once I put my 35's on it might give me a little taller over all gear and get me into a 13.

What do you all think?
 

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Southern Idaho VP
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Ran 07 is the one to talk to since he is the fastest
 

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Wife's mad I spend $$$$$$
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Discussion Starter #10
I've seen his posted times.

He's got a different transmission if memory serves.

Man I was out of 1st,2nd,3rd so darn fast. I was in 6th through the trap at about 2600rpms.
 

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Southern Idaho VP
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If your going to keep racing, you might consider a built tranny to help put the power to the ground, then start feeding it some fuel and air.
 

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Wife's mad I spend $$$$$$
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Discussion Starter #12
I'm only going to run it once or twice a year. It's not going to be an all the time thing.

I'm hoping a little overall taller gear with 35's will help since I'm going to 35's and I won't be swapping tires at the track. Swapping tires all around and taking seats, tailgate and spare tire out to shed weight got real old with my hemi. I like being able to just pull up and go with the new truck!

I'm surely open to suggestions though. What would anyone do to have a built transmission?
 

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i would nt be doing this with a 35" tire on a stock tranny.
 

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Wife's mad I spend $$$$$$
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Discussion Starter #15

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I'm still on the stock tires with 4.10 gears. I think once I put my 35's on it might give me a little taller over all gear and get me into a 13.

What do you all think?
Absolutely not, IF you think you need less gear, then swap gears; don't add tires. 35's probably weight twice as much and adds all that weight to your rotational mass. She'll drive like a pig. I had 315/70-17's on my truck when I bought it. Best thing I have done to date is get rid of that crap and go back with a stock sized tire. Plus, larger tires add more stress to the driveline.
 

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Mopar has some good points. I just went from 305/50/20's(32" tire) with 3.73's, to a 325/40/18(28" tire) with 3.42's. 18's are drag radials are a third of the weight, and really soft. Notice my speed on the 11.08. I only had 10mph left on the back half of the track:doh:
 

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Wife's mad I spend $$$$$$
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Discussion Starter #18
I don't disagree one bit about going to taller gears and shorter tires. I know all about rotational mass trying to get my Hemi faster. Not to argue at all, but I guess I'll prove myself hypothesis wrong. To me it feels like weight wasn't an issue when, I took my wife out and it only made a .026 difference on the 1/4. If I shed 200lbs from my Hemi I would have been .2 or more faster.

I'm not sure the actual weight difference on the stock vs. 35, and I know rotational mass weight is more to deal with then just weight on the vehicle. My Hemi had 20" wheels with 32's, swapped out for 17" wheels and D/R's and I dropped about 50lbs per corner in rotational mass. Big difference at the the track!

If I were to race it all the time going taller gears and smaller tires is exactly what I would do, but I'm not and I've been wanting 35's since I got my lift on. I ordered the truck with 4.10's knowing I was going to put 35's on and the effective gear ration would be the same as 3.73's with stock tires.

If I'm slower then I'm slower with them. It's not critical to see a 13, but it would be nice since I wasn't able to do it in my Hemi. I do know that most of my friends at the track are in the 13.8 - 14.5 category and that's usually with drag radials and lightened trucks. So for me to pull up and go right off the street tells me I'm faster light to light then they are.

Ram '07, can you tell me your list of mods? Maybe I can tweak the truck a little more. I've been considering keeping my stock wheels and putting different tires on them just for the track. But I'm not going to be swapping gears at all, drag racing it wasn't why I got. But it is nice to show up some of my friends with V8's.
 

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Wife's mad I spend $$$$$$
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Discussion Starter #19

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700hp Club
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The bigger the tires you put on, the more power they rob, and the slower you go. if you want to creep into the 13's, then put a little more power to the truck, and then start saving for the trans, trust me i've been through a few. When i had my truck "mostly stock" with just an MP8,edge j/a, fass, intake and exhaust on 32" tires, i ran 14.2 all day on a stock trans, got about 35 passes out of it. Then i went with the bigger turbo, injectors and an xrt, boom, by by stock trans. I am running low 13's now in 5th gear, but nadp is working on a better trans and by this summer if all goes well, my 3500 megga cab should be in the 12's if i can get a trans to hold. So, to sum up my long winded story, stay where you are and be happy with the track times, or start saving for LOTS of new parts, and have fun chasing the next bracket like i'm doing......
 
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