Cuda340

Here are the complete questions and answers from the July 21, 2010 SRT Engineers' Chat Session:

What is the limiting factor for the 6100rpm redline on the 6.1? Valve springs? pistons? heads??

The valvetrain is the limit on the engine but the A/T trans shift speed limit is right there too.

Have you had a lot of issues with fan motors, I am on my third set and the car is only 3 years old ?

We haven't seen any issues.

Hypothetically, if you guys had a LX and wanted a stock cat back exhaust what would you do to modify it, if anything to support say 650-700hp? I know what Pauls answer is, but I wondered if there were any other opinions on increasing the flow or if it is even needed.

Sorry, I'm going to give you the same answer that Paul gave you. Your stock exhaust basically is a straight through and will support 650-700hp.

I have a old GSM kit to shut off the ESP 100%..so I thought... in listening to what you said if the esp button is not pressed is the computer still seeing delta's and compensating ? I know the predator will do the same but its just easier having the control at the touch of a switch...

Not sure how the ESP system would react with the GSM Kit. If the stock calibration is there, and still full on, it will be sending out messages to control the vehicle.

A lot of folks on the forum have had a problem with engine stalling. For me on three separate occasions the car (2009 Challenger SRT8) has stalled when slowing down and preparing to make a turn. It happened twice with my 6.1L engine and once with the 426. Given it has happened with the stock and stroker engines I don't think it is the engine. Is it a potential problem with how the fuel system/tank is designed ?
There is a software fix coming to correct this issue. Stay tuned.

Can you shed any light on the theory that line locs may be causing Getrag clucth pack failures, and why?
Still digging into that on. We've got a plan to get one of the axles back to take a look at it. I see some long smokey burnouts in my future. Darn

What recommendations do you have to improve the life of the ball joints in the upper control arms up front?

Best thing to do is keep the stock ride height and alignment settings

Why is the TCM programming still such a mystery to aftermarket companies. Seems like the PCM tuning has either been released or at least decoded allowing us to reap some good performance gains. Why not release the TCM tuning codes to allow us to keep up with the competition (which is getting very stiff). Lots of these cars with aftermarket parts are making power past 6400 rpms and my buddy with an '06 300 SRT8 (without the TCM flash) is able to paddle hold the shift at times to 7000 rpms without a problem. Some of us here are big boys and are willing risk popping a motor (on our dime).

Sorry, for right now there are no plans to open up the cals for modification. Altough we know many of you are capable ofmaking the right kinds of mods remember the trans is not rated for anything above the production performance output

Noisy bushings, struts and bracket- I only drive this car about 4000 miles a year so I feel that this should not be 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 don’t 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?
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

Best way to check the parts is the part numbers.
2008FrontFront RT04854577AC Front LT 04854576ACRearRear LT05039344ADRear RT05039344AD
The new upper strut mounts are now tooled and should be available soon.

It continues to be bandied about that the 6.1 (and to a lesser degree the 5.7) has an excessive PCV oil vapor ingestion issue that is the root-cause for pulling timing (by-way of the knock sensors - supposedly reacting to octane level degradation because of significant oil consumption/oxidation under normal operating conditions. The cure recommnded by the vendors for this ailment is purchasing/installing a catchcan.

Both the 5.7L and 6.1L engines meet all corporate requirements for PCV performance. However, as we have mentioned in previous chats, installing a catch can shouldn't harm anything.

During (factory) engine assembly, are the knock sensors raw voltage O/P tested, or even monitored from engine-to-engine? It appears the amount of timing being pulled due to knock sensor activation (real or perceived) varies from platform to platform. Is this normal (it's understood that fuel quality, engine load, atmospheric conditions, etc play a part)?

During end of line testing, output from the knock sensor is verified to be present. Comparing the amount of knock retard between vehicles can be deceiving. As you mentioned there are many factors that affect knock limit. Unless the conditions of your test subjects are identical (highly unlikely), the amount of knock retard can vary.

Given the popularity of the Drag Pack cars, Why is there not a way to order a factory racer like the ARC Neons ? That are street legal and would make a nice weekend racer for someone. Off a SRT that got all the fun go fast bits, but none of the extra weight ?

Nothing like that right now but there is a Challenger BIW coing very shortly. That with all the bits and pieces out there might make a great road racing project .....


Is there a recommended mileage for changing plugs in our vehicles for day to day, spirited driving?

Your SRT8 spark plugs are Platinum tipped and are good to well past 100K miles. If you are driving "spirited" they should be cleaning themselves continuously. For injectors (and valves for that matter) using good quality premium fuel will give you the detergents and additives necessary to keep those components clean. Your recommended maintenance schedule for combustion cleaning and as well as fuel injectors with again day to day spirited driving habits.


Does the TC lockup in all gears except 1st? I get a bog under light throttle in 2 and 3rd gears and I'm assuming its the TC locking up. Is there something else I may be missing that is causing this bog? Under WOT, it pulls as it should.

Yes the torque converter locks up in multiple gears. Hard to diagnose a bog over this keyboard, but that could be part of it. More likely it's in a higher gear and leaning into the throttle a bit further forces a kickdown and the resulting grin on your face. You could try using the autostick feature to stay higher in the rpm band. That way the grins are readily more available when you get the urge.

When the porfessionals took us around the track they turned the ESP off what are the gains from having it off? 2009 srt8 6.1 challenger

The owners manual has a good explanation of each of the different modes, but in a nut shell...
On : All systems on
Partical Off: Engine Torque Management Off, Brake Traction Control Off, Stability Control On.
Full Off: same as above with Stability Control Off...

Is there any way to totally turn off the traction control? I only drag race this car with limited cruising lots of car shows also. Thanks in advance for your time!!I have a SRT8 CHallenger 2010? Also what is the HP rating of the axles on the 2010 SRT8 Challenger?

Check your owners manual. Press and hold the ECP Off button for 5-10 seconds and the ESP full off will come on.

The 6 speed cars can get a 3.73 or a 3.91 ratio in the diff. On the auto cars there is no option for a 'performance gear'. The magic ratio to gain a little bit of an edge with the auto cars is the 3.23, I'd love to see the Getrag available with this gear set.

Actually, the SRT only has 1 ratio for each transmission. That would be the performance ratio

Please forgive the reference to a non-SRT part in this comparison; it has been suggested that the new 2009 composite intake manifold is very similar to the 6.1 aluminum intake in rate-of-flow, runner length, and therefore power band. Flow results have the 2009 composite unit within a few CFM of the existing SRT intake manifold. Can you kindly confirm or deny please they are pretty close in actual configuration. The idea being the composite version offers less mass and a lot less heatsoak..

OK, you must be talking about the Eagle composite intake manifold as a comparison to the 6.1L manifold. There are several Eagle intakes (for different applications) with different features. Generally we would not recommend swapping the intakes. If you were really intent on improving the intake flow on the 6.1L a port and polish of the aluminum runners on the 6.1L would be a better way to go.