Cuda340

The following were the responses of the SRT Engineers to the questions raised during last night's LXforum SRT Chat session:

Please give us as much info as possible on the new 6.4 L motors.

All we can say is it exists!


When converting from the stock air intake to a aftermarket CAI, how long does it take for difference between the two to take effect?


Any performance increase from reduced intake system pressure loss will be immediate. There are some adaptives that will require a short drive under the right conditions to update.





why not have the "ram air" ducting go to airbox instead of over exhaust? I see slight benefit to current design but would like to know why y'all went that route instead of traditional to intake route?





It would have been a big tear up to the induction system which is rather expensive to tool. Also and probably the bigger reason is there is so little room to route between the hood scoop, throttle and where a airbox would have to be place the higher restriction would overcome any gains in ram air.





Do 6.1L Hemis have a small vacuum tap anywhere? I need a vacuum source to operate my headlight doors.


Yes, you can t-splice off the brake booster, purge harness, or map sensor.



I heard that they made a change in the Tremec 6060 trans for 2010, shouldn't that be a warranty problem and they should fix the 09's.

The changes that we made to the transmission were improvements for customers. They were not warranty issues...the 09 cars are not broken!!



I want to install a Dual Shift Light on 2009 Challenger SRT8 6 speed.





The only shift lights Mopar offers are included with Mopar branded tachometers. We are still investigating fresh air options for the T/A hood but are not ready to release any details at this point.





In our efforts to improve upon what are already two great powerplants (5.7 & 6.1), folks are putting the 6.1 intake manifold on 5.7's.



The plastic intake on the 09 5.7L cars was derived after the 6.1L, by the same person in fact....so yes, they are pretty similar in design and function. They do however have some differences since the 09 5.7L has Variable Cam Timing and the 6.1L doesn't, so there were additional tweaks done to the 09 5.7L Plastic Intake for optimization with the cam. I'm not 100% sure, but the intake tracks should be similar to the old 5.7L vs. 6.1L. As far as performance goes, the plastic will certainly have less heat soaking issues, but again the systems are different. So, play at your own risk when it comes to spark knock due to airflow mixture motion. Let me know what you guys find.....I'd expect performance to be similar.





If you had to build a Challenger roadcourse racecar which is still used as some kind of daily driver which parts would bring the biggest efficiency regarding space savings?





Obviously an aluminum block engine would save almost 100 lbs. The rest of the weight comes from unnecessary options (radio, sunroof, seats, etc...) and the body structure. When you start hacking out body structure, you are taking street risk and should substitute with cage structure which is very dangerous on the street without harnesses and a lid. The front and rear cradles are steel and heavy, too, but we have yet to see someone do one out of AL.





1) does the bore size of a CAI make a difference?

[mopar offered cai is not the largest, nor the smallest]

2) is there a measureable difference in using a CAI vs not using one?



The bore size of the CAI kit does affect the intake system tuning. In our development vehicles CAI kits have shown improved performance under most conditions.



The only shift lights Mopar offers are included with Mopar branded tachometers. We are still investigating fresh air options for the T/A hood but are not ready to release any details at this point.



As an addition to the previous answer, there will be a Mopar branded stand alone shift light available in the first quarter of 2010.







how far into an engines life can we see some oil consumption due to piston ring set-in?



It all depends on the duty cycle your car see's....I can seat (break-in) a set of rings really fast if you'd like me top In all honesty, the first 500-1000 is the most critical at getting enough heat cycles through the engine. After 2000 miles, your rings should certainly be fully seated. With that said, depending on how hard you drive your car and where you drive it in the rpm range (you do have a 6spd), you could still consume a small amount of oil. 1/4qt over 1000 miles doesn't really concern me, but keep an eye on it and let us know at next month’s chat.







Do you have any numbers of how much downforce the front and rear spoilers on the SRT Challenger generate?



The SRT8 at 130 mph generates about 60 lbs of downforce at the rear and about 150 lbs of lift at the front. That is MUCH better than most manufacturers in the industry who make much more lift. The R/T is less aggressive on both ends. The SRT airdam is better than the R/T one. You want aero understeer in the car to compensate for the natural instability as speed increases. This is why racecars have more wing in the back than splitter in the front. More down always feels better, but we have to balance aero downforce with drag.



The fastest I have gotten the '09 Challenger SRT8 up to is 181 mph (rev limiter in 5th, manual trans) with a tailwind on our test oval. Our full scale wind tunnel goes up to 140 mph. There is not much reynolds effect on the Challenger, so the aero numbers stay proportional with speed.





Before production started, I had read that the stick-shift Challengers would get stiffer motor mounts. Do they have stiffer motor mounts and if so is it a different design or just stiffer rubber?



The stick shift Challengers have totally different mounts than the autos. The autos have hydro mounts and the manuals have constrained rubber mounts. The reason for the change is to keep them alive with the larger spike loads that come with a stick shift. The SRT manuals are slightly different that the R/T. They have less travel before they snub to the housing for lower less enigne movement.



We haven't used the 75W-140 gear oil in the Getrag diff. The higher viscosity certainly couldn't hurt with gear noise, but I wouldn't expect much of a change. The risks are seal life and clutch chatter. No way to tell without testing it. The clutch pack will still need friction modifier added to it. Good luck if you want to try, but I can't say I'd recommend it.





notice MOPAR is making an aluminum block available now. Was cost the only consideration in making the 5.7 and 6.1 blocks out of iron?



This may have been addressed before but it has been noticed that some factory x-pipes are closed off and only appear to cross gases from each pipe.



Cost is the major issue behind the iron vs. alum.

The X-pipe closed vs. open was actually done for sound quality. We wanted a more aggressive exhaust note on the Charger vs. the 300C so the Chargers got the closed x-pipe.





Is a 2009 ChargerSRT8 suspension different, how do we Challenger owners "dial in" a better handling ride and what can be done about numb steering feel?



All the L series SRT's have the same steering systems, with unique suspension tunes to give them unique personalities. The 2009's do have a caster change and a slight retune to the suspension.



Are there any plans to offer offer Mopar lowering or higher performance springs for the Challenger SRT8?



2) Are there any plans to offer Mopar supercharger kits for the 5.7 or 6.1 Hemi?



3) The 6.1 L Hemi has been built to be considerably stronger, with forged crank and strengthened block, etc. Can you tell us what "limit testing" has been done to see how much horsepower this configuration will support without the use of more forged internals?





1)PN P5155436 lowering springs are available at your dealer today.



2) Well, we never say never but soon.



3) As engineers we work hard to optimize all of the components. So the answer to your question would be there's risk inherent in any increase in boost for your engine. How much your willing to except would be up to you.



I am trying to stagger the wheel/tire diameter difference between front and rear.

What is the largest percent difference I can achieve before the ABS or other electronic control device will be affected.



Can these controls be modified or eliminated?



5% diameter difference.



They can't be modified. If you eliminate it, you eliminate ABS. Unless you built tonewheels with more teeth on the front than rear...



Have a 2010 Challenger SRT8 6spd and I despise the skip shift. I know you can`t recommend disabling the skip shift, but there is a kit out there that emulates the resistance of the solenoid to avoid tripping the MIL due to that, but can you confirm the `10 models will trip the MIL because the ecm knows the transmission is not in 4th?





The functionality of skipshift is the same in '09 and '10.





We build a lot of supercharged SRT-8's and they all seem have the same issue. When you apply part throttle, as soon as MAP goes to 0, the throttle fully opens.



Good to hear you're a serious enthusiast but we didn't engineer the car with forced induction. It's really hard to say what the engine and sensors are doing. Kinda like telling a mechanic "it goes clacker clacker when I turn left".



Why did the Superbee get axed from production ?





It was intended to be a short production run vehicle.



Is there a way to reset the ECU / PCM to the original factory settings, pre April 2006? It appears that the many times that Chrysler has flashed the ECU on the SRT8 the software has dumbed down the performance, taken away the slap-stick functionality and removed the slippage quotient of the rear end and added an adapttive mode.



The ECU/PCM updates you speak of are typically regulatory in nature, so it is a one-way update. As far as the "dumbing down" of performance, etc... sometimes that is a temporary thing until the engine adaptives are relearned.



Did you come up with any options for the rear supension for drag raceing to help the cars launch like on the 60's cars where u had the pinion snuber and the ss springs with the extra leaves on the front half of the springs and maby som more room in the fender wells for som bigger slicks also the ability to use 15 inch wheels so we can use the big slicks.



Currently some rear axle options are being investigated, both for street and strip. At the moment, nothing to announce, but stay tuned in early 2010.



What made you choose the 3.06 gear opposed to a 3.73 or 3.92 for the automatic?



Testing showed this to be the sweet spot between fuel economy and performance. The rear tires still spin at launch so you've still got more torque than the traction available.



I live in an area of the country where summer time temps hit 110 to 120 on a daily basis. I've noticed my EVIC temp hit as high as 230 during normal driving. Is this acceptable?



I see you must be using the engineering pages. 230 degrees is not a problem.



A caster change and a slight retune to the suspension for softer/more body roll or firmer? Could my dealer change that, would they know what I am talking about?



The '09 front shocks are just incrementally firmer. I doubt anyone but a vehicle dynamicist could notice. The caster change was made by changing the front upper control arm to relocate the upper ball joint. It is not adjustable by the dealer. Moving the cradle around won't do very much. You could put '08 or earlier upper control arms on. Then you'll have to put on '08 or earlier SRT knuckles to correct the bump steer to match.



Can we inprove the wheel hop situation using the MP coilovers to further tune the suspension. Any additional recommendations?



Stiffer motor mounts might get you a small improvement.



I have 2 sets of wheels/tires (winter/summer) for my '08 Charger SRT, all the wheels are OEM, stamped "SRT" and "ALCOA FORGED". I bought 4 additional TPM sensors from a dealer, (68001698AB for '08) and they seem to communicate with the receivers, except that at any given time, I will typically see 2, 3 or often all 4 tires showing the same pressure. This happens with both the summer and winter set. The actual pressures do vary a bit by a manual gauge, so apparently 1 sensor is displaying on all 4 fields of the readout. The dealer service people want to put their scanner on it for $100 each spring and fall, when I change wheels, but it strikes me as a warranty issue. I've asked friends at Brampton Assembly about it, all they can say is, "it shouldn't do that"

Any thoughts? Thanks.





The sensors transmit a unique ID number along with the pressure information. Once the module learns the new set of sensors (you need to drive it over 20mph to make sure it transmits) and the location it will update only the one location. The module won't accept the same ID number for two locations.



The sensors are +/- 1.0 psi 1.5 psi at extreme temps and the guage in your hand is +/- 1 psi at best so it is very possible that all the sensors will read the same while the guage says they are slightly different.



Was the skip shift implemented for gas mileage reasons? Is it okay to eliminate the skip shift with the aftermarket CAGS Solenoid eliminator?





Yes, fuel economy. Can't recommend eliminating the skip shift - the EPA/CARB will come after us.