SRT-6 Upgrades
The SRT-6 has more potential than the N/A, mainly due to how the engine is more capable of handling the load, as well as the body/wing helping with keeping the car on the road. The only main issue you'll start to have is the limited slip differential (LSD), that will not be able to put the power on the ground on the back tires. There are aftermarket LSDs that should be capable of handling the torque.
Known bolt-on upgrades
NeedsWings OverDrive Crank Pulley Kit
The Overdrive Crank Pulley Kit contains the following upgrades:
- A new belt
- Smaller (175mm) ASP Crankshaft Pulley
- Pulley Saver Kit, including replacement pulleys
These upgrades are really good and I would recommend if you would go for your first tune. Your (stock) crankshaft pulley is most likely getting apart already, so it is worth the money to invest into a replacement. The Pulley Saver Kit contains new pulleys that have seen a lot of miles/km, so they are worth replacing too.
NeedsWings Oil Catch Can
The intakes of the M112K engine tend to suck in oil from the valve cover ports, which will get back into your engine. While the car can handle it, it seems to help with a nasty exhaust which proves that it helps combustion.
NeedsWings Dual Cold Air Intake (DCAI)
The (Dual) Cold Air Intake is a bolt-on replacement of the stock airboxes. They give much more air to the engine, increasing potential, and also makes you hear the whine from the supercharger.
Upgrading stock SRT-6
When you have a 2004 or 2005 SRT, it currently has been driving around for well over 15 years. Rubber and oil might get in spots where it shouldn't get, and the RCM can get in bad, but solvable, state.
We'll go through the things you can upgrade for more performance but also to fix age-related issues of the car. Note that, to have the best effect of your upgrades, you should look into ECU tunes!
Crankshaft Pulley
The crankshaft pulley is the most notable one that starts getting bad after 15 years. The rubber ring in the center will collapse, and when its gone, your engine will be shaking. You could go for a stock replacement, like the one on NeedsWings, but to be honest, it is maybe worth it to upgrade it to a smaller one so you have more power.
Supercharger Pulley
The stock supercharger pulley is the easiest to replace, but smaller ones with a clutch can fail faster. If you go for a supercharger pulley, you might want to look into the non-clutched ones because they are more solid. Needswings recommends upgrading Crankshaft over Supercharger pulley due to the high failure rate.
V-Tech Georgia ships 64 to 74mm pulleys clutched (like OEM) and 55 to 74mm without a clutch. Note that the clutch will usually engage after about 1500 RPM, and it affects how fast you get a boost. It is kinda like a turbo lag, but then its your engine RPM and not the turbo RPM. The clutch is engaged by the ECU, so an ECU mod should be able to change when it engages.