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SRT Engineers Round Table: 05/25/2011

99K views 117 replies 35 participants last post by  chargerlover 
#1 ·
SRT Engineers Round Table Discussion

Wednesday, May 25th 5pm - 7pm ET

The ground rules:

  • First off, the SRT Engineers take time out of their busy schedule making go fast goodies to be here to answer our questions. Let's show them the proper courtesy and patience. There will be many questions and they may not be able to answer every question asked. If your question is skipped, please be patient as questions are not answered in order.
  • Please only ask one or two questions. There are lots of people who want to ask questions, so let's give everyone a chance.
  • Stay on the topic at hand. SRT Vehicles! Keep the off-topic chat to the other sections of the website. There is to be no discussion between members in this forum. Ask your question and enjoy the replies from the Engineers!
  • If your question has already been asked (by you or someone else). Don't re-post it in hopes to get it answered quicker.
  • Make sure you let the SRT Engineers know what model SRT vehicle you are driving or inquiring about. Yes, a head gasket is quite different between an SRT8 and an SRT4. :wink:
  • As much as everyone is salivating over what comes in the future, the SRT Engineers cannot answer any questions regarding future product.
 
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#3 ·
I am an owner of a 2009 SRT8 Jeep. A new transfer case was installed in my vehicle 6 months ago. After 18 months of my car being evaluated by various Jeep service managers, it was concluded by the Zone manager and Chrysler mechanic that the rear clunking noise that originated when I downshifted by gears from 4th to 3rd to 2nd gear was due to a faulty transfer case chain which also led to them installing a new input flange. After the new transfer case was installed, the rear clunking noise disappeared until 2 months ago to the present, I am now beginning to experience the same rear clunking noise when I down shift my gears. I would like to have your expert opinion and direction on this frustrating matter.

Thank you,
David Silva
Alexandria, VA
201.232.8282
 
#48 ·
I am an owner of a 2009 SRT8 Jeep. A new transfer case was installed in my vehicle 6 months ago. After 18 months of my car being evaluated by various Jeep service managers, it was concluded by the Zone manager and Chrysler mechanic that the rear clunking noise that originated when I downshifted by gears from 4th to 3rd to 2nd gear was due to a faulty transfer case chain which also led to them installing a new input flange. After the new transfer case was installed, the rear clunking noise disappeared until 2 months ago to the present, I am now beginning to experience the same rear clunking noise when I down shift my gears. I would like to have your expert opinion and direction on this frustrating matter.

Thank you,
David Silva
Alexandria, VA
201.232.8282
David- this is a new one to us. Diagnosing a noise like that over the internet is next to impossible. I can only suggest you bring it back to the dealer. Sorry, that might not be what you want to hear. Just thinking outloud, but you might want to look at the driveshaft. If the grease worked out of the slip splines it could be sticking. Removing the driveshaft to change the T-case would have move some grease around, making it slide more freely for a while. Again, just a thought.
 
#4 · (Edited)
Hey SRT engineers! I no longer have my SRT but have a question about the earlier LX models and the front brake caliper piston corrosion. Is this a closed-book issue in your opinion that a few of us made a big deal over, or is it something you still communicate with Brembo about??? Was there ever an official opinion on there even being a problem - and a diagnosis??? Jus' axin...

Keep up the great work!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
#6 ·
Do the new 6 piston calipers on the Grand Cherokee share the same measurements as the four pots as far as mounting and offset? Can you swap them to the cars?
 
#8 ·
What size pistons do the front Viper calipers use? I see that the viper calipers are serviceable unlike the SRT8 calipers. Is thier any chance the Viper service kits would work?
 
#30 ·
What size pistons do the front Viper calipers use? I see that the viper calipers are serviceable unlike the SRT8 calipers. Is thier any chance the Viper service kits would work?
Nope unfortunately even if the diameters are the same, the piston length needs to be sufficient to not push the pistons out with worn pads and not too long so new pads will fit with the piston fully retracted.
 
#9 ·
Just for fun. Out of all the lx an lc srt s which one is your favorite.
 
#10 ·
Hi guys, thanks for subjecting yourself to this torture :) Seriously, I enjoy reading your responses and appreciate the things I've learned in the past.

My question is if you guys consider aftermarket speed modifications (supercharger, etc) when you design a SRT vehicle? For example, the new VVT cams and some of the other new technology on the cars makes them harder to modify. Do you guys sit down with aftermarket speed vendors to share info or is it up to the vendors to figure things out for themselves. Just curious how the industry (specifically the SRT group) works.
 
#32 ·
Hi guys, thanks for subjecting yourself to this torture :) Seriously, I enjoy reading your responses and appreciate the things I've learned in the past.

My question is if you guys consider aftermarket speed modifications (supercharger, etc) when you design a SRT vehicle? For example, the new VVT cams and some of the other new technology on the cars makes them harder to modify. Do you guys sit down with aftermarket speed vendors to share info or is it up to the vendors to figure things out for themselves. Just curious how the industry (specifically the SRT group) works.
We are aware of what many of the aftermarket suppliers do but can't really favor any one of them other than MOPAR. We don't back off on our technology even if it makes it harder to modify in the aftermarket.
 
#11 · (Edited)
Great job on the new 392's.

Regarding the variable length runner system within the intake manifold; can you elaborate on the technology please; details like where in the rpm range it was determined the best point of transition, whether there are multiple transition points and the reasoning, and most importantly what sort of gains in HP and TQ were observed during testing. Thanks!
 
#12 ·
Techs and service personal who work with/on these fine platforms daily have confirmed there is no such thing as a "throttle recalibration" by simply slowly depressing and holding the accelerator pedal to the floor for a few seconds after key-on (no start).

However the procedure, and the purported gains still permeate the internet stating (for example) they experience better throttle response. The premise is that there is a hidden procedure that allows(!) an end-user to alter or "recalibrate" their FBW throttle system (we are aware that the throttle body performs a self-diagnostic, full open/close, prior to every key-start). Care to somehow put a stake in this rumor once and for all?
 
#35 ·
Techs and service personal who work with/on these fine platforms daily have confirmed there is no such thing as a "throttle recalibration" by simply slowly depressing and holding the accelerator pedal to the floor for a few seconds after key-on (no start).

However the procedure, and the purported gains still permeate the internet stating (for example) they experience better throttle response. The premise is that there is a hidden procedure that allows(!) an end-user to alter or "recalibrate" their FBW throttle system (we are aware that the throttle body performs a self-diagnostic, full open/close, prior to every key-start). Care to somehow put a stake in this rumor once and for all?
There is a throttle recalibration on the ETC (Electronic throttle Control) that can be run as a subroutine when in diagnostic mode (hooked up to starscan). No such means of doing this without a engineering/dealership hook up into OBD port.
 
#14 ·
Big fan of the new Chally 392!!!

In reading the auto press test reviews of this tire shredding beast I see 1/4 mile times of high twelves to low thirteens with trap speeds of 111-114. Those trap speeds indicate to me that lower ET's are being limited by traction issues. Has any thought been given to creating a formal launch control function aside from the standard ESP?
 
#37 ·
Big fan of the new Chally 392!!!

In reading the auto press test reviews of this tire shredding beast I see 1/4 mile times of high twelves to low thirteens with trap speeds of 111-114. Those trap speeds indicate to me that lower ET's are being limited by traction issues. Has any thought been given to creating a formal launch control function aside from the standard ESP?
We haven't considered putting a formal launch control into ESC system... the best launch control is your right foot.
 
#15 ·
My 2010 Challenger SRT8 has a loud & (at cruise nights) embarrassing tick, tick, tick sound upon warm start up. Lasts 5-6 seconds then fades away to silent. Never happens cold or hot...... only warm like after I have been parked for an hour. Was told by the dealer & lots of MOPAR guys this is normal.... I gotta tell ya... hope this has been addressed w/ the 2011's cause the Chevy and Ford guys are getting quite a laugh when they hear my baby sounding like a jalopy. Should I be concerned with this noise????
 
#42 ·
My 2010 Challenger SRT8 has a loud & (at cruise nights) embarrassing tick, tick, tick sound upon warm start up. Lasts 5-6 seconds then fades away to silent. Never happens cold or hot...... only warm like after I have been parked for an hour. Was told by the dealer & lots of MOPAR guys this is normal.... I gotta tell ya... hope this has been addressed w/ the 2011's cause the Chevy and Ford guys are getting quite a laugh when they hear my baby sounding like a jalopy. Should I be concerned with this noise????
Could be air being purged from the valvetrain. Not a durability or performance concern - other than some noise.
 
#16 ·
Are there any plans, or has there been talk, to start offering the SRTs forged from the factory? Even as an upgrade? im sure all us F/I guys would appreciate not having to buy pistons and all that to run more boost?
 
#17 ·
SRT Engineers Round Table Discussion

Wednesday, May 25th 5pm - 7pm ET

The ground rules:

  • First off, the SRT Engineers take time out of their busy schedule making go fast goodies to be here to answer our questions. Let's show them the proper courtesy and patience. There will be many questions and they may not be able to answer every question asked. If your question is skipped, please be patient as questions are not answered in order.
  • Please only ask one or two questions. There are lots of people who want to ask questions, so let's give everyone a chance.
  • Stay on the topic at hand. SRT Vehicles! Keep the off-topic chat to the other sections of the website. There is to be no discussion between members in this forum. Ask your question and enjoy the replies from the Engineers!
  • If your question has already been asked (by you or someone else). Don't re-post it in hopes to get it answered quicker.
  • Make sure you let the SRT Engineers know what model SRT vehicle you are driving or inquiring about. Yes, a head gasket is quite different between an SRT8 and an SRT4. :wink:
  • As much as everyone is salivating over what comes in the future, the SRT Engineers cannot answer any questions regarding future product.
Are there any plans, or has there been talk, to start offering the SRTs forged from the factory? Even as an upgrade? im sure all us F/I guys would appreciate not having to buy pistons and all that to run more boost?
Are you new??:blam: :Na_Na_Na_Na:
 
#18 · (Edited)
Thanks guys!!

I just want to thank you guys and gals for the kicka$$ vehicle you design...Now I had a question from last time that didn't get answered..Maybe you have an update for me...Please!!

Hey guys and gals..thanks for having these disscussions...I have posted this before and wondering if this is going to take place per earlier chats..
Quote:
Quote:
http://www.chargerforums.com/forums/...&postcount=173
Originally Posted by Joeyclutch
I've been having a problem with a front end noise. Its been to the dealership several times and nothing has been resolved. They have replaced the steering rack, control arms, the bushings, struts and bracketts. I only drive this car abhout 4000 miles a year so I feel that this should not ben happening. The regional service rep said that this "noise" is a characteristic of the SRT vehicles from 2006-2007. I have driven in other SRT vehicles and did not notice this noise at all. Obviously they thought there was a problem with my car or they would not have switched out all of those parts. I even went so far as to look into the Lemon Law but unfortunately I was passed the alloted time. I dont think this is fair and need advice. Thank you.

For 2008, there was a check valve change to the shocks which helps this noise. They are retuned for better ride as well, so we suggest replacing all 4 if you want to go this route. The source of the remaining noise is the front upper strut mount in rebound events. We are working on a design change to help the issue, but it will be some time before we will have something out. Thanks to these webchats, we are able to convince management we need to keep working on it.
Is there a replacement strut mount available yet? If so, is there a way to differentiate the new design vs. old to make sure I am getting the new one?

Is there a way to differentiate (visually) the revised dampers from the old ones?

Thank you

I was just wanting a time line that I could possibly get the redesigned dampers..The dealership has replaced both struts and several other parts, but when showing them the chat answer from before..they are also waiting the redesigned part.....Any thoughts on this

And thanks in advance..
Ralph
 
#40 ·
I just want to thank you guys and gals for the kicka$$ vehicle you design...Now I had a question from last time that didn't get answered..Maybe you have an update for me...Please!!
Yes. The 2008 300C, Charger, and Magnum SRT8s all got new shocks for 2008 with revised tuning. They all have new part numbers. We have since found that the noise is even more sensitive to the front upper strut mount. We revised this design for 2011 on the 392 Challenger SRT8. Put those mounts on the car, and the clunk noise (if it is coming from the shocks) pretty much goes away. This is a more effective and much cheaper solution. The part number for this front upper strut mount is 05181575aa.
 
#19 ·
Was wondering why is it that all SRT8 models besides the SRT8 Jeep come with slotted rotors ?
Ever since I purchased the Jeep I have been having issues with very loud brake squeling, unlike the normal squeaking noise from the Charger I had before. Dealership offers no fix for it, they "service the brakes" and replaced pads/rotors but the horrible noise remains the same. Is this due to the flat rotors on the Jeep ?
 
#44 ·
Was wondering why is it that all SRT8 models besides the SRT8 Jeep come with slotted rotors ?
Ever since I purchased the Jeep I have been having issues with very loud brake squeling, unlike the normal squeaking noise from the Charger I had before. Dealership offers no fix for it, they "service the brakes" and replaced pads/rotors but the horrible noise remains the same. Is this due to the flat rotors on the Jeep ?

No, the slots on the L's are there for rotor scoring/wear. The Jeep linings are different - Made for more vehicle weight & higher brake temps - Drive it harder! :wink:
 
#55 ·
Just a quick question which maybe stupid. But why can't you make an SRT/8 in AWD ? To much HP & Torque, or to expensive ? Could it be done ?
We do, it's called Grand Cherokee SRT8!

Kidding aside, the AWD L adaptation raises the body and lowers the front and rear cradle in order to package the driveline components (t-case, front axle). To achieve our ride height we would loose jounce travel and end up dragging the chassis on the ground. We actually built one but we did not get the performance improvements compared to the RWD to justify the system. It was also difficult to make it handle. An AWD SRT must offer a performance advantage. If you want an all weather LX SRT8, buy some winter tires.
 
#21 ·
Guys and Gals thanks for your time.

As you can tell several people are looking to use 6.4 parts on other builds, something that has been thrown around are the differences in the block design in the 6.4.

The 6.4 from whats been said before is a beefed up 5.7 VVT

Spec size what was changed ( wall thickness, webbing etc )

It seems Dodge is going to be doing a lot more after market for the Rams, I hope that will work into the Gem3 Hemi's and LX/LC/LY platforms as well.

-R
 
#53 ·
Guys and Gals thanks for your time.

As you can tell several people are looking to use 6.4 parts on other builds, something that has been thrown around are the differences in the block design in the 6.4.

The 6.4 from whats been said before is a beefed up 5.7 VVT

Spec size what was changed ( wall thickness, webbing etc )

It seems Dodge is going to be doing a lot more after market for the Rams, I hope that will work into the Gem3 Hemi's and LX/LC/LY platforms as well.

-R
The 6.4L block is quite a bit different from the current 5.7L. Bore is bigger, deck height is quite a bit different, stronger sections, different material, provision for piston squirters..and it's painted orange. If you plan to use it for other builds, you have to pay attention.
 
#23 ·
I have a 2007 charger srt8
tsb for 15w-50 oil
I have noticed with the mobil 1 15w-50 that it takes much longer for the oil temps to rise (I have to drive it hard or @ the track to exceed 230 degrees) hence the oil pressure @ start up is around 80psi and with part throttle will climb into the 90 psi range and takes muck longer (until the oil is hot) for idle pressure to be in the 20 psi range..
Is there any potential problems with the oil pressure being that high for extended periods? what is the oil weight you would recommend for the hot Florida months?

Thank you !
 
#39 ·
Oil for the 6.1L is 0w-40 synthetic.
We changed to 5w-40 synthetic on 2011MY.

I have a 2007 charger srt8
tsb for 15w-50 oil
I have noticed with the mobil 1 15w-50 that it takes much longer for the oil temps to rise (I have to drive it hard or @ the track to exceed 230 degrees) hence the oil pressure @ start up is around 80psi and with part throttle will climb into the 90 psi range and takes muck longer (until the oil is hot) for idle pressure to be in the 20 psi range..
Is there any potential problems with the oil pressure being that high for extended periods? what is the oil weight you would recommend for the hot Florida months?

Thank you !
 
#24 · (Edited)
Hyper-grounding has slithered its way onto our platforms with the obligatory promises of better fuel mileage, more HP/TQ, smoother/faster throttle response, etc by simply replacing various GND cables with larger AWG (understanding how voltage and/or current are controlled by-way of the PCM - specifically ignition/fuel systems means the above gains are at best questionable).

However a CSN was released (J21; NOV/09) that suggests replacing B- and possibly the battery (w/higher CCA). This CSN, along with the notion the entire existing OEM GND cabling is inadequate (with zero empirical measurements), are being held up as proof.

Can you elaborate on the reasoning behind J21's release, and why it covered a specific (production) range of vehicles. Thanks.
 
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#29 ·
I have heard of several changes to the power steering system on the 2011 Challenger. Can you share what was changed and what the results should be?

Thanks,
 
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