Modding the LX Hemi

[Meister]

I have enjoyed enabling the engine, transmission, and suspension of my sweet Hemi to realize more fully their performance potential and to perform as I, the driver, choose. Every performance mod has removed yet another item from the list of observed driveability flaws and performance shortcomings with my '05 LX Hemi.

The K&N Typhoon intake and Jet Performance throttle body spacer eliminated nearly all throttle lag, with the Typhoon adding a throaty accent to accelerations. Adding the stage II Jetchip removed all remnants of throttle lag, firmed up the tranny, reduced shift lag, and moved my shift point further up the rpm scale. This mod alone, by bumping up both tranny & engine performance, gave me the new-found ability to hang the rear end out at will when cornering. Many months and 6000 miles later, that ability continues undiminished. Mileage increased by 2 to 3 mpg, city & highway, respectively, which more than compensates, cost wise, for the need to run 91 octane fuel (or higher - performance increase is proportional to octane rating).

I added the Magnaflow cat-back exhaust in early September and picked up high-end performance and a beautiful exhaust note. Mileage increased by 1 mpg.

The GSM torque modulation & fan mod has removed any remaining complaints with the transmission, and immediately moved my shift points back up to where the jetchip initially had them. Every shift at WOT now occurs at a totally predictable 5500 rpm, precisely, each & every time. Partial-throttle shifts appear to hold each gear a bit longer. Lag in any given gear is gone completely, and kick-down to a lower gear has been speeded up appreciably. The fan mod, in conjuction with a cooler thermostat (both are essential), has killed heat soak.

At the track in early September (Phoenix Firebird: 1,243’ MSL, approx 4250' PA, 95 degrees F.) I repeatedly hit the rev limiter doing pre-run burnouts. Full torque launches at 30 psi rear tire pressure resulted in excessive wheel spin throughout first gear and part-way through second gear, resulting in ETs in the 15s, but decent speeds. Lowering the stock rears to 22 psi helped control wheel spin. Best overall run of the evening, however,13.85 at 101.98 (adjusted), with a .065 R/T, occurred prior to lowering my tire pressure, but with a very mild torque launch. By midnight air at the track had cooled down to 90 degrees F. I’d hung around waiting for this relatively cooler air to give me the outright 14.5 ET I'd set as my personal goal for that hot desert night, but my heat-soaked motor simply couldn’t produce it.

Unhappy with heat soak, which, due to the hot 203-degree stock thermostat, even the GSM fan mod couldn't prevent, I installed a nominal 180-degree thermostat, which actually cooled to an indicated 174 degrees on EVIC. The combination of the GSM fan mod and a colder tstat is - as the current slogan says - priceless. At my most recent track event, with multiple runs - several of which were back to back with less than 10 minutes between runs - coolant temp as I prepared to stage was always in the 160s.

This provides very consistent runs, with times varying only with changes in ambient air temp. Heat soak is now essentially non-existent.

My Hemi was tested on the dyno and the track at GIFO3 in Sacramento. Rear wheel horsepower was just shy of 290 hp, and rear wheel torque was just over 300 ft/lbs. Best run on a warmish evening was 14.0 at 98 mph, unadjusted for a density altitude of around 800 feet if memory serves.

I have continued to test cooler thermostats. The 160 degree tstat is the ideal tstat for the track. I've had no issues running it on the street - if I avoid using the fan mod, temps will run as hot as with a 203 around town. But if on the highway for any significant time in cool ambient temperatures it runs cooler than I am comfortable with. Long-term the 170 is the best overall choice for me - it is my year-round daily driver. The 160 will be installed each track day.

My most recent mod, KW V2 coilovers and Hotchkis Sport anti-sway bars, has brought my Hemi to near perfection in concert with my prior mods. I'm using the factory suggested initial rebound damping setting of 2 turns out, front, and one turn out, rear. Performance at this suggested initial setting is so flawless that I'm in no hurry to change anything anytime soon - I have absolutely flogged these KWs and the Hotchkis bars and had not the slightest complaint with or from them.

On tight, twisty, mountain roads the total combination of a jet chip, cooler thermostat, GSM torque & fan mod, and KWs and Hotchkis sways was unbeatable. The superb driveability that I've always pointed out that the jet chip provides by removing virtually all throttle & tranny lag, coupled with total disabling of ESP, the fan mod keeping coolant temperatures at or near my cooler thermostat's temp for sustained maximum horsepower delivery even when I was flogging the motor, and a superior suspension was an unbeatable combination. In these extreme conditions, where one is going from wide open throttle (WOT) to ABS chatter to WOT, etc., faster than you can read about it, my car was fully a match for the stock SRT8.

The additional power generated by the Jet chip is certainly a factor as well, but its most appreciated benefit in these tight conditions was the instant response the chip enabled from both engine & tranny.

Words cannot describe the exhilaration I experience seeing all systems, placed, at my command, to optimum performance parameters, working in a flawless, overpowering, synergy...

What I meant to say is that my total performance package really kicks some serious butt.

Summary:

1. The LX-based Hemi's in stock form are very capable vehicles and get the job done well. Most of the noticeable driveability flaws and performance shortcomings which frequently irked me about my stock LX, and which have essentially disappeared because of my mods, are absent at WOT and thus are masked while on the dyno and at the strip. Day to day driveability improves tremendously with mods, the Stage II Jet Chip in particular.

2. If you enjoy being able to truly set your hair on fire--hang the rear end *way out* at will on corners, enjoy hearing a Hemi's inimitable howl from *both* ends, and don't mind occasionally seeing some rubber converted to good old-fashioned tire smoke--the mods are the only way to go. The fun factor goes way up.

3. I'd to it all again—in a heartbeat.

[chasb]

I'm getting there Jim. (as you know)
MOPAR CAI
Magnaflows coming next week
GSM "thermostat" coming next week or so

BTW, I danced last night and now I'm paying the fiddler. (I'm 57)

Originally Posted by Meister

I've truly enjoyed modding my sweet C. Every mod, whether performance or appearance / function, removed another item from the very short list of complaints I've had with my '05 LX Hemi. I'll only address the performance mods here:

The K&N Typhoon intake and Jet Performance throttle body spacer (both were installed at the same time, so I can't address the contribution of the TB spacer alone) eliminated nearly all throttle lag, with the Typhoon adding a throaty accent to accelerations. Adding the stage II Jetchip removed all remnants of throttle lag, moved my shift point further up the rpm scale, and gave me the new-found ability to hang the rear end out at will when cornering. One month, and nearly 2000 miles later, that ability continued undiminished. The WOT shift point, however, did get reeled in slightly by the MDS, with shifts typically occurring at 5400 rpm, occasionally as low as 5300 rpm. Mileage increased by 2 to 3 mpg, city & highway, respectively.

I added the Magnaflow cat-back exhaust last week and picked up high-end performance (don't ask) and a beautiful, to my tin ears, exhaust note, with no discernable change in mileage. I may need to add another set of resonators, though, as my wife is less taken with the “noise” factor than I, and they do get appreciably louder with time & use. And tonight, for the first time, I experienced MDS “blubber” with the Magnaflows which other owners running aftermarket exhaust systems have commented on. Tapping the AutoStick and moving the tranny out of Drive “cures” it, but out on the open road I’ll want MDS active, and without the blubbering. Thus the MFs are an open item. Richard, are you out there?

Another mod I've only recently made (again, don't ask) has removed any remaining complaints with the transmission, and has moved my shift points back up close to where the jetchip initially had them. Every shift at WOT now occurs at a totally predictable 5500 rpm, precisely, each & every time. Partial-throttle shifts appear to hold each gear a bit longer. Lag in any given gear is gone completely, and kick-down to a lower gear has been speeded up appreciably.

At the track recently (Phoenix Firebird: 1,243’ MSL, approx 1500' PA, 95 degrees F.) I repeatedly hit the rev limiter doing pre-run burnouts. Full torque launches at 30 psi rear tire pressure resulted in excessive wheel spin throughout first gear and part-way through second gear, resulting in ETs in the 15s, but decent speeds. Lowering the stock rears to 22 psi helped control wheel spin. Best overall run of the evening, however,14.608 at 96.67 (.065 R/T), occurred prior to lowering my tire pressure, but with a very mild torque launch.

By midnight air at the track had cooled down to 90 degrees F (YGBSM). I’d hung around waiting for this relatively cooler air to give me the magic 14.5 ET I'd set as my personal goal for that hot desert night, but my oft-worked & heat-soaked motor simply couldn’t produce it. Next time I'll probably show much later in the evening.

Lesson learned the following day (I'm 62, BTW, and hadn't been to the drags in four decades): It's much harder to soar with the Eagles the next day when you've been out hooting with the Owls the night before.

Note: Special thanks go to BMWDON for the great price on the stage II chip, Typhoon & throttle body spacer package, to TByrne for the great GB price on the Magnaflows, and to GSM for the uh, errrr, ummm, oh yeah!...for the *thermostat* . Thanks mucho, guys, for helping me have this much fun, period, and especially for enabling it to be done for around half of MSRP.

Summary:

1. The LX-based Hemi's in stock form are amazingly capable vehicles and really get the job done well--I bested the time of a near-stock 300C last night by only the narrowest of margins (his only mod, TMK, was to remove the stock CAI's baffle).

However, comma, if you enjoy being able to truly set your hair on fire--hang the rear end *way out* at will on corners, enjoy hearing a Hemi's inimitable howl from *both* ends, and don't mind occasionally seeing some rubber converted to good old-fashioned tire smoke--the mods are the only way to go. The fun factor goes way up.

2. You can't realistically compare your Hemi to another's--each is created different. Mine was no slouch (it would probably take a true lemon for one to be considered such, realistically), but it probably fell in the mid-range of performance, at best, among 300Cs as delivered. In its stock form it fell short of a number of performance marks other C owners had posted over the past year for their stock Hemis.

3. I'd to it all again—in a heartbeat!!

[Lik2race]

Meister...
I went to Flowmaster on my exhaust,loved the sound.
However, Fiance' had a little difficulty with it - just a bit loud.
I added a 12" glasspack old "cherry Bomb" style muffler,welded on my 4" Chrome exhaust tips.
Still have the rumble at idle,throaty grumble upon acceleration,and
"Turn the Beast Loose" sound at WOT.
Labor, welding = $60
2 "cherry bomb" glass packs = $40
a big "Thank you Darlin' " = Priceless........

[Meister]

Originally Posted by Lik2race

Meister...
I went to Flowmaster on my exhaust,loved the sound.
However, Fiance' had a little difficulty with it - just a bit loud.
I added a 12" glasspack old "cherry Bomb" style muffler,welded on my 4" Chrome exhaust tips.
Still have the rumble at idle,throaty grumble upon acceleration,and
"Turn the Beast Loose" sound at WOT.
Labor, welding = $60
2 "cherry bomb" glass packs = $40
a big "Thank you Darlin' " = Priceless........

Thanks, Lik2race. Looks like the perfect solution with your flowmasters. My magnaflows already use the space you mentioned with resonators (see http://www.magnaflow.com/02product/s...d=236&cat=300C).

Magnaflow (Richard) has suggested an internal modification to the main muffler if a tone down is required.

[chasb]

with the Magnaflows??

I've heard that it pings or something?

Originally Posted by Meister

Thanks, Lik2race. Looks like the perfect solution with your flowmasters. My magnaflows already use the space you mentioned with resonators (see http://www.magnaflow.com/02product/s...d=236&cat=300C).

Looks like it's time to contact Richard, as I don't see any obvious solution as I look at the car & the diagram.

[Meister]

Originally Posted by chasb

It the MDS noise really that bad with the Magnaflows??

I've heard that it pings or something?

No pinging noted, Chas, but the sound certainly isn't pleasant. I suppose it's that with a louder, aftermarket, exhaust we're literally *hearing* a four banger when she's in MDS mode.

At present we're keeping the MFs as installed.

[FOAMAVEN]

That's why I love the Borla 3.5 inch system, just enough noise to know it's not stock but not enough to drive you nuts.

[JP300c]

you guys would hate my exhaust then two 14 inch long borla mufflers and 2.5" pipes ...no resonators

[Meister]

Magnaflow's ace Mopar designer, Richard, is, indeed, looking at a way to tone the MFs down a bit for me. I'll continue to update this thread with any particulars.

[chasb]

They are sitting here in the box and giving me no pleasure at all at the moment.

I would be interested in hearing more on the DB issue, though. I don't want the blubber either.

Chas


ps Thanks Meister for another informative write up, if I didn't already say it.