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Old 08-26-2015, 01:09 PM
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Drag racing tips and tricks 2010 Hemi

So I finally have an opportunity to hit the drag strip this year and I wanted to reach out and see if anyone has any ideas on how to shave off my last few tenths. My best time last year was 14.14 @ 97 MPH. The goal is 13.XX (Lebanon valley dragway in upstate NY for those calculating for altitude density) Here's what I've got, what I've done so far, and what I've been thinking about.

What I've got:
2010 Limited with the 5.7, diablosport catch can, K&N intake, 2013 charger IAT sensor, modern muscle "85" mm ported throttle body, SRT take off exhaust manifolds mated to a modified set of stock mid pipes, Gibson cat back exhaust, CMR tune adjusted for bolt ons and 93 octane from Sean at hemifever.

There are a handful of variables/methods I can think of.

Methods:

Loading the torque converter: Mash the brake and gas, let off the brake at the last yellow light. This kind of scares me as I feel like she doesn't like it, and it almost seems like the CPU knows something is wrong. This launch method seems to lag when compared to holding the brake lightly and snapping the gas pedal down at the last second.

Traction settings: The CMR tune raises the trans pressure and dials back on the traction control significantly. I'm not sure HOW the tune accomplishes the TC difference, it may just force the traction control off regardless of whether or not I've pushed the TC off button. Then there's the whole push and hold the TC off button for 5 seconds to turn off ESP (electronic stability programming?). I run it with ESP off.

Auto vs manual shift: the CMR tune has the WOT shift points set to 5800 and the redline at 6200. In auto it shifts promptly at 5800. In manual I try to time the shift so it occurs just before 6200 but sometimes there is a slight lag in the shift and sometimes I'm late and waste time sitting at 6200. Also, when in manual during the shift from 2nd to 3rd, the rpm only drops by about 500 vice the 1000 or so drop I see when in auto (almost like an overdrive gear or something). I got my best time using manual shift despite the weird shifting from 2nd to 3rd. Since then I've figured out how to manually set the shift points with the intune and I'm considering raising the shift points, but how high do I go? I've pushed it to 6200 in manual numerous times and it didn't blow up, so 6200 should be fine... Right?

Variables:

Spark plugs only have 2.5k on them. Air filter has about 8k on it but I keep a drycharger wrap on it that I take off at the track.

Engine oil: I'm running royal purple 5W20 with a royal purple oil filter. There's about 2500 miles on the oil now. I normally change it around 4K so I'd hate to change early, but would it help engine performance if it were fresh oil?

Tire pressure: I have no trouble with traction, so my thought process is that with a higher pressure I'll have less rolling resistance. They are oem tires with 8k of wear (hated to buy stock but I needed tires and got a great deal). The manual calls for about 34 psi, but I've run them all the way up to 39. How much higher could I push it, would it help?

Octane: the highest NON ethanol around here is 91 and that's what I've been using for the past month. (Used 93 w/ ethanol on my last run) I feel like 91 pure would give better performance than 93 with 10% ethanol. Am I mistaken? Would there be any benefit to using an octane booster to get the overall up to 93 or would that be just as bad as the 93 w/ ethanol?

Weight: I removed the spare tire and jack (which is really rolling the dice with running over inflated tires for an hour long drive to the track), and had the gas tank down to about 2/5th. I'm thinking about removing the armor undercarriage plates this time but it would be a real pita to do (only have on street parking).

That's all I can really think of. If anyone has any other suggestions or thoughts on what I've come up with please let me know. Thanks for reading!

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2010 Jeep Grand Cherokee Limited 5.7, Gibson cat back, SRT exhaust manifolds w/ modified mid pipes, K&N CAI, Modern Muscle "85"mm throttle body, Diablosport catch can with custom Home Depot bracket, Diablosport Intune with Hemifever CMR
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  #2  
Old 08-27-2015, 04:21 PM
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Re: Drag racing tips and tricks 2010 Hemi

After much tapping on the intune I've re loaded the CMR tune with 1-2 and 2-3 shift points set at 6100, turned off MDS too. Checked the sidewall markings and they said 44psi max, set them all to 42 psi by the hand held press gage (the evic is telling me they're all at 44, I wonder which is more accurate?) Decided that the skid plates weren't worth the trouble. Gas tank is at 3/4 with 91 non ethanol, should be at 1/2 by the time I get to the track. I'll take the spare and jack out in the morning. Just oiled my spare clean air filter and that will go on in the morning as well. Checked the oil and it still looks clean so I'm sticking with what's in there.
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Old 08-28-2015, 11:10 AM
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Re: Drag racing tips and tricks 2010 Hemi

I am on the road and can't respond right now, but good luck at the track. I'll be back home late next week and, when I get some time I'll put my 2 cents worth in. Again, good luck.
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05 LX/RT & 06 WK/GCO, modded similarly, MDS "ON" Light, Vortex Gens, Debadged, DashHawk, BT Catch Can, SRT CAI W/Add Air Inlet, K&N Filter, Sonnax Trans Press Booster, SC Tuner W/Adv Trans Tuning App, DS Tuner, Cust tube headers w/3 in. catback, Bilsteins, SRT frt/rear bumpers, Eibach SRT Lwr Sprgs & Sways, FRI Sidewinder Cam Adv 2*, 6.1 valvetrain, SLP 25% UD Pulley, BBK 90mm TB, SOS Coils/.060 plug gaps. 20 in. SRT Reps.
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Old 09-03-2015, 10:23 PM
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Re: Drag racing tips and tricks 2010 Hemi

Did you get to the track, Luke? Everything you said above is about as good as you're going to get. You're right though, loading the engine (stall speed) reduces the launch effectiveness. What would help here is a 3000 RPM stall converter. Years ago I used to run one and it was a hoot to drive, but not too good on a daily driver. I understand the newer converters work better though so I don't know if the same is true today. When you manually upshift from 2-3 you're going into 2 Prime, not 3rd. That is why you're getting only a 500 RPM difference compared to approximately 1000 RPM. You can see the transmission gear ratios make the difference. Here they are in case you don't have them: 1st: 3.0, 2nd: 1.67, 2 (P)rime 1.50, 3rd: 1.0, 4th: .75, and 5th: .67. IMO, a 4.10 differential set would also help move the mass a little better....and also improve the fuel economy a little, especially on the highway. With the cam I have in mine I run in 4th gear on the highway (~60-70 mph) at ~2000-2300 RPM, and the RPM could be a little higher to get it more into the power range. When I run mine, I always take the air filter out completely....for racing only. Mopar Muscle did an article last year on power loss created by the various engine components. Compared to running NO air filter, at performance peaks, the stock paper filter robbed the engine of 10.4 lb. ft. of torque and 14.4 hp. An Airaid high flow filter robbed only 5.5 lb. ft. of torque and 5.9 hp. Every little bit helps. With the stock cam, I'd probably run the shift points at about 6000 RPM, as I am sure peak power is achieved at a slightly lower RPM. I run my aftermarket cam to 6200 RPM, with the rev limiter set at 6400 RPM. Yours may be a litle different because of the VVT setup. I also run the cam in my WK with a 2* advance on it. On my Hemi LX, I advanced the same cam by 6*, and it works even better in the lower RPM range.

With a good DA, you should be able to get into the 13's, especially since you have the CMR tune. I still run the canned SC 91 tune in mine and am happy with it. Everyone said I needed a custom tune with the cam, and I don't feel that is necessarily true. I guess the CMR's help somewhat, but I like my fuel economy (main reason for most of my mods) and am not sure that a custom tune would help that much in that regard.

Good luck and let us know how it went at the track.
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05 LX/RT & 06 WK/GCO, modded similarly, MDS "ON" Light, Vortex Gens, Debadged, DashHawk, BT Catch Can, SRT CAI W/Add Air Inlet, K&N Filter, Sonnax Trans Press Booster, SC Tuner W/Adv Trans Tuning App, DS Tuner, Cust tube headers w/3 in. catback, Bilsteins, SRT frt/rear bumpers, Eibach SRT Lwr Sprgs & Sways, FRI Sidewinder Cam Adv 2*, 6.1 valvetrain, SLP 25% UD Pulley, BBK 90mm TB, SOS Coils/.060 plug gaps. 20 in. SRT Reps.
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Old 10-01-2015, 08:29 PM
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Re: Drag racing tips and tricks 2010 Hemi

What kind of times are you running?
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Old 10-01-2015, 08:52 PM
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Re: Drag racing tips and tricks 2010 Hemi

We haven't heard from Lucas lately, but I just went back and looked at my times and the various stages of mods. These are the times with a 5000 lb. race weight and running 1st, 2nd and 3rd, without using 2P:

Stock except for 3 in. cat. back: 60 ft..............2.185 sec.
1/8 mile.........9.412 sec. @ 75.654 mph
1/4 mile.........14.64 sec. @ 93.118 mph

Custom Headers w/3 in. cat. back: 60 ft..............2.144 sec.
1/8 mi. 9.211 sec. @ 82.521 mph
1/4 mi. 14.502 sec. @ 94.236 mph

Custom Headers w/3 in. cat. back/Cam w/ 2* advance: 60 ft............2.106 sec.
1/8 mi..........9.042 sec. @ 79.072 mph
1/4 mi..........14.067 sec. @ 97.340 mph

Note: Last modded times were before I added the SLP 25% UD Pulley, BBK 90mm TB, SOS Coils and a Transgo Valve Body Shift Kit. I haven't run it since adding these mods.
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05 LX/RT & 06 WK/GCO, modded similarly, MDS "ON" Light, Vortex Gens, Debadged, DashHawk, BT Catch Can, SRT CAI W/Add Air Inlet, K&N Filter, Sonnax Trans Press Booster, SC Tuner W/Adv Trans Tuning App, DS Tuner, Cust tube headers w/3 in. catback, Bilsteins, SRT frt/rear bumpers, Eibach SRT Lwr Sprgs & Sways, FRI Sidewinder Cam Adv 2*, 6.1 valvetrain, SLP 25% UD Pulley, BBK 90mm TB, SOS Coils/.060 plug gaps. 20 in. SRT Reps.
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