AGP Wastegate Actuator
Work In Progress
The idea has always been to build a well balanced daily driver capable of realistic track numbers and horsepower goals with a limited budget. The car responds well to just about any modification and we've managed to keep the cost low by purchasing used parts, participating in group-buys, and working with sponsors. Keep an eye on this SRT-4 as we continue to pursue our goals.
With the failure of the first big wheel stock turbo I decided to go with a different manufacturer and what they promise is a superior product. The result was PTP's SST (Super Stock Turbo) with a custom compressor wheel, clipped turbine, ported/machined compressor housing, and ceramic coating. Well that didn't last long either, so back to Forward Motion's Enforcer 1 turbo we went!
The E1 is a big difference over the stock turbo, but without a way to pull some fuel I have yet to really see what this new turbo can do. There is a small amount of lag compared to stock, but full boost still comes in right around 3200RPM. The best way to describe it is that the car feels like it has to work harder to get out of vacuum and start building boost, but after reaching 5psi shooting up to 22lbs is a breeze.
A cold air intake is usually within the first three modifications for just about any vehicle. This wasn't the case when it came to this SRT-4. I always heard the stock airbox with an aftermarket drop-in filter was good for 300WHP without any problems, as it turns out it's more than capable since we managed 315WHP on a completely stock intake system.
However, the stock airbox is a pain in the ass to work with. Just about anything you do under the hood requires removing the entire air box and intake tube. A cold air intake would at least give some extra room to work with. So when the chance came to pick up a full 3" Mopar Cold Air Intake I didn't think twice about it. First thing I noticed was the difference in sound during light acceleration, it's big difference. It's hard to really tell if the car feels any different, only dyno and track numbers will gauge the performance benefits of this intake.
It's no secret that Mopar offers Stage Upgrade Kits for the SRT-4. These kits range from Stage 1 (Powertrain Control Module and/or Injectors) all the way through Stage 3 (PCM, more fuel, bigger turbo, etc). The kits range in price and power accordingly and offer a great foundation for just about any modification path.
Difference in Model/Year: Stage 1 Kits for 2003 SRT-4 vehicles include a new set of 577cc Injectors, already stock in 2004/05 models. Stage 1 MSRP is the same for all SRT-4 years.
A large number of SRT-4 enthusiast keep the stock PCM, sometimes incorrectly referred to as Stage 0. Many argue that Stage 1's only benefit is eliminating CEL (check engine lights) triggered by certain modifications, e.g., removing the catalytic converter. There are ways around all these CEL, most of them involve tricking the computer and costing only a few dollars.
So why Stage 1? Mopar's Stage 1 kit is not always the most effective way to eliminate CEL, but it is the most plug-n-play solution. When combined with the Mopar/Borla Exhaust it will produce one of the most aggressive and unique exhaust sound. Stage 1 also provides the very argued WOT (wide open throttle) shift feature. This last feature holds boost between gears while pressing the gas pedal via TPS (throttle position sensor) allowing for a more smooth and aggressive shift. Stage 1 is perfect when upgrading to a bigger turbo or a ported stock turbo.
Worth the money? Yes, if you can find it for a decent price. The $400 MSRP of the Stage 1 kit seems like a big price tag for getting rid of a couple of CEL & a meaner sound. However, keep in mind that it's easy to find a used Stage 1 kit for around 200 bucks and pick up a few dyno proven horses. Stage 1 is a questionable investment but one that I would suggest depending on your specific goals.
When I started working on this project I wanted to keep as many things Mopar as possible, so like many of the other parts I happened to run across an unbeatable price on a Mopar/Borla Turbo-Back exhaust. The entire system is made from 2.5" diameter mandrel bent pipes. The Mopar downpipe replaced the catalytic converter with a small resonator while the Borla CAT-Back replaces the 2 stock resonators with only 1 bigger unit. Even at 2.5" the dyno shows comparable gains to cars with similar modifications and a 3" exhaust. Partnered with Mopar's Stage 1 and PTP's 3" O2 Housing the exhaust note is incredible. The Pops! during deceleration are deep with a couple of crackles here and there, and the idle note is just louder than stock without becoming obnoxious in rush hour traffic. This is the exhaust the SRT-4 should have been equipped with from the factory.
Although I plan on running solid engine and transmission mounts in the near future, prothane inserts are an inexpensive and easy method of eliminating wheel-hop. Most vendors offer two versions of prothane, street and race. I'm currently running the race inserts for my top and bottom engine mount combined with a filled transmission mount. Ride quality and comfort has certainly been compromised, but nothing extreme. This is still a street car after all and a bit of vibration during idle and take-off isn't a big deal to me.
I ran across a good deal on a group buy on eVilcreations' FMIC (front mount intercooler) so I picked up one for each SRT-4. The core measures 24"x12"x4" and it fits the front bumper without any heavy modifications. However, it does require the removal of the crash bar. The cold-side outlet is not oval like on the stock piece, this makes it very tricky to install the stock pipe. The hot-side inlet sits very close to the PCM bracket, but doesn't rub. We were able to use stock and aftermarket pipes without any big issues. It's necessary to drill holes on the blank mounting place, some patience and an extra set of hands are required to make sure the everything is leveled.
I did not have a chance to dyno test this part individually, but the manufacturer claims over 15hp and almost 20ft/lbs of torque. I was able to notice a significant difference in almost every gear towards the top of the power band. The car no longer feels like it's hesitating or chocking after 4000RPM but instead pulls hard all the way to red line. The power gains make this FMIC a great investment and the more aggressive look up front doesn't hurt either.