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mechanic237 06-12-2013 02:16 PM

Nitrous and a new torque convertor on the 5.7
Hey im looking for input on how to do nitrous on my jeep and the low end seems pretty bad on take off (because of the airaid intake and bbk 85mm throttlebody im guessing??) so im looking into getting a different torque/stall converter. I was wondering if anyone has any used or new aftermarket converters i could possible buy?? I already have NOS nitrous bought and i hope to run around 75hp shot so nothing to outrageous.

jeepgcoman 06-13-2013 11:52 AM

Re: Nitrous and a new torque convertor on the 5.7
Both of these mods. have been done for years on the Hemi LX vehicles, and are fairly reliable as long as you don't go overboard. I've never run NOS myself, but I've had several buddies with Hemi LX's run it. It is, by far, the best bang for the buck, but can also be very dangerous. So you know what it can be worth, on a good, heads, headers, stock rotating assembly, a 100 shot of NOS, and a stock torque converter, took a full second off the quarter mile time.

First, what mods. do you have already? To get maximum benefit out of the NOS, you'll first need a good complete header back exhaust system. The stock WK logs won't cut it by any means. Either LX logs (good), SRT-8 headers (better), or aftermarket/custom 4-2-1 or 4-1 tubular headers (best) are pretty much your choices. IMO, with stock WK exhaust logs, I'd be surprised if you get ~30-35 hp. out of a 75 shot of NOS.

On a stock rotating assembly the pistons (top ring land) are the weak spot in the engine, followed by the exhaust and cam timing. Running a 75 shot seems to be a good, conservative choice, and a 100 shot being slightly more risky. The other thing that MUST be done, for the engine's sake (and your pocketbook), is to insure your fuel mixture compensates for the NOS shot by getting a Diablosport tuner WITH a CMR tune. Anything else, and you're taking big chances. Also, most don't have it kick in until you're "off the line".

On the TC, again, if you don't go overboard (above ~2500-2800 RPM) on the stall speed, you should be OK. It'll generate more heat, so you may need an additional trans. cooler. Certainly have a way to monitor the trans. temp. Years ago, with the old fluid coupling Hydramatics, we'd run stalls as high as 4000-4500 RPM, but that was strictly for blown drag race vehicles. Talk about heat generation.

Before you go doing the converter, you should also, boost the line pressure in the 545RFE. I use a Sonnax Line Pressure Booster (increases clutch clamping pressure and reduces clutch slippage), and it works for me, along with the Advanced Transmission Tuning Application for the Superchips Tuner. If you get a Diablosport Tuner with a CMR tune, they can properly adjust the pressure, torque management to improve the shift quality and help prolong the tranny's life.

Good luck and let us know how it goes. Don't think many folks have done these particular mods. on our super heavy WK's.

mechanic237 06-15-2013 10:39 AM

What will i need to do to put 6.1 headers on?? Cuz the exhaust ports are different right?? And what's a good quality header that won't drain my bank account? And i got a sharadon stage 3 valvebody and i ordered a line pressure booster and i also have a diablosport predator that has advanced trans tuning so i should be good there....and will a stall converter hurt my driveability?? Cuz i still wanta be able to drive it normally.

jeepgcoman 06-15-2013 03:12 PM

Re: Nitrous and a new torque convertor on the 5.7
You don't need anything to install the 6.1 long tube (the only kind they make) headers, using the 6.1 gaskets. You'll need fairly extensive head (Y) pipe mods. and a wiring extension for the rear O2 Sensors, behind the cats. Some folks have had DTC light problems with this setup, but I really don't know why.

As far as draining your pocketbook, the 6.1's will take a pretty big hit on it. I believe they're upwards of $1000, just for the headers. Add all the other exhaust work and you'll probably be up near $1800-2000 by the time you're done. My complete custom ceramic coated headers and 3 in. cat. back cost me ~$1400 and, IMO it's worth every penny of it. They've been on there for two and a half years now, and only one blown header flange fault for not retorquing.

The DS Predator does not give you full control over all up/downshifts, and normal/WOT torque management. It will only allow you to set the up shift schedules for 1st, 2nd, and 3rd, nothing else. Don't know if they can do all that with a CMR tune, either. That's the only reason I am still running the Superchips tuner on my WK, so I can get this full control.

Did you talk to the Sheradon folks about your valve body? Specifically, do you need the Line Pressure Booster with the Stage III Valve Body? I know the pressure (and everything else) is electronically controlled, but they may have changed something (probably valve spring pressures) that will fool the pressure regulating system. One thing you don't want to do is go too high on the pressure.

At the drags a stall converter, in combination with everything else being well set up, will allow your start (off the line) RPM to be up closer to the engine's maximum torque range. A stall converter won't affect normal driveability too much, unless you go too high on the stall speed. It'll just take more throttle (RPM) to start the vehicle moving. Kind of like reving a manual trans. up to 2500-3000 RPM before you start releasing the clutch, everytime you started out from a stop. IMO, stall converters are good for the drags, but not too good on a daily driver. Years ago, on one of my racers, I had a 2800 RPM stall, and it was great for the drags, and cruising the boulevard and local drive-in, but not worth a crap for everyday use. Fortunately it was not my daily driver, but it was a lot of fun when I did drive it. I hear what you're saying about the off the line performance though. Both my Hemi vehicles are modded exactly the same and neither one sets the world on fire off the line.....~2.00 sec. 60 ft. times. And, if I shut the traction control off, they'll light the tires up something terrible. Some big, gummy slicks would help, as would some better gearing and a stall converter. As little as I go to the drags (3-4 times a year), it's just not worth going wild anymore on all this stuff. I've done all that in my past life and, fortunately a lot of it is out of my system....I think......and my wife hopes. Now I am just after somewhat better performance and a little better fuel economy. I am pretty happy where I am at now, without doing any major engine/transmission work. In addition to the mods. listed in my signature, I have also added an SLP 25% underdirve pulley and the BBK 85mm TB. If your ride is pretty much stock I think the 85mm TB is definitely hurting you a little. A better choice would probably be a ported 80mm one, or just leave it alone. Chrysler runs an 80mm on all their Hemi's....5.7, 6.1 and 6.4, so you know it is more than adequate. On mine, I knew that going in, and was just hoping it might help, even a little. Haven't had it to the drags yet, so I can't tell for sure, but my first impressions after the install are that the throttle response isn't quite as good, and neither is the WOT power.....and the volumetric efficiency of my engine is a fair amount better than when it was stock, because of the headers and aftermarket camshaft. Only other thing I am going to try is either the MSD or SOS ignition coils and open up the spark plug gap to about .060 in. Then I am done, unless I have to get into the engine innards for some reason.

dmsfun 06-21-2013 02:24 PM

Re: Nitrous and a new torque convertor on the 5.7
Low end on a bone stock 5.7 is pretty bad but can be dramatically improved with the right upgrades, making it a whole lot more fun on the street. Likewise, with the wrong mods you will lose low end, making it less fun to drive.
Your low end torque is affected both from the aftermarket intake and the TB, and depending on mileage and maintenance history, could also be from other areas, like sticking lifters, fuel system clogging, MAP sensor, EGR, etc.. Assuming the bbk 85 is straight and not a taper bore you need to dial in the A/F or it will run lean at WOT so do this either on a dyno or using wideband O2, or bolt on the stock TB. With my MM taper bore 85, low end increased over stock with no other mod's and no tune or A/F changes needed. Returning to the stock intake with a new panel filter will also help restore low end, and is what I now run after thorough testing of both ported and stock TB, and with and without CAI on each. The best combo tested is the taper ported TB and stock intake.

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