This how to is for all the stock srt-4 or new srt-4 owners out there.
There is always a right way and a wrong way to do things, and I’m going to show you the rights way to upgrade a stock or close to stock srt-4 to get the most for your money.
First things first you need to understand how things work. air and gas goes in and blows up, more air = more gas that can burn, More gas that can burn = more power, so lets get started.
The first mod you need to do is a good intake whether you make it yourself or get a pre-made one. now this will get you a few hp on its own but will help make more power with the next mod, Next get a good exhaust again you can make one yourself to save some money, or get a aftermarket one but make sure you get a 3" downpipe and a full 3" exhaust, also a 3" 02 housing will help but not worth the money unless you have a ported turbo.
ok now you have a lot of air going in and a lot coming out, now we need to get some boost up to take advantage of it. so get yourself a aftermarket wastegate and get your boost up to 17.5-18psi, this is safe on the srt-4, you may also want to do the tip mod (unhook and plug off the red line coming off the cold side boost pipe.) this will remove any over boost code on the 03-04 srt-4's.
ok now we have pushed the stock srt-4 fuel system to its limits and we need more fuel to get more power but we want to make sure its safe power so GET A WIDEBAND A/F MONITER, after that a return fuel line and adjustable fuel pressure regulator, and also a map clamp (now with a bit of searching you can find out how to make a map clamp for less then $10 and if you can solder I suggest you do because there overpriced for people that can DIY, if you can’t solder then just buy one from dasmopar or ptp I think sells one, you can also just get a safcII or some type of piggyback fuel computer. but the map clamp also know as a over boost defender is the cheapest but will only work to 300hp. now remember the red line you blocked off, use that port on the cold side pipe to control your fpr (fuel pressure regulator) and set it to 45-50psi with the line off, hook the line back up after setting the base psi, next you want to turn your boost up, you can set it as high as 22psi on a stock turbo without hurting it. now go for a spin and watch your Air/Fuel monitor and don’t let it go leaner then 12.5, more then likely it will be super rich, which gets us to are next step. start to pull some fuel with the map clamp, now the car is going to hit fuel cut until your map clamp is set below 5.0v but don’t go lower then 4.2v now your car should be at 300hp or very close to it if you have you’re a/f ratio at 12.5 and no richer then 11 and the moding path can go in many directions. a big fmic would be your best bet and some water/meth injection would be good also and then you have things like say a big turbo
ok to sum things up this how to was made so you can get the most hp from each mod, you could get the parts in a different order but you wont get as much hp from each part at that time. like say you get the return fuel setup and clamp you wont get much if any hp from it but spent $300+ but you could get the intake for $150 and see 15-20hp, also you may have noticed I never mentioned things like a bov this part sounds cool but has no performance benefit at this point but after all that I have mentioned you could get some hard boost pipes and a bov and even those the bov doesn't get you any power the less restrictive piping will.
I hope this how to help some novice srt-4 owners and if you follow what I have said you will save yourself some money and frustration (nothings worse then spending money and not getting anything from it till you get another part. Happy Moding.
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MOD LIST: agpWG, MBC, custom return fuel setup, bottle neck mod, map clamp, hard boost pipes, TiAL 50mm bov, 3" turboback dump, CF trunk,
COMING SOON: AGP S200 turbo kit check out my ride and mods here
Mopar STG3 w/t, 3inch TBE,HKS turbo timer,QWFMIC,mopar blue plate special,soon to be swapped for an HKS,AGP W/G,and 30PSI guage.Mopar CAI,and AEROSPEED Catch can.FBM ported race combo, Fidenza flywheel,and a 6puck clutch
Soon to come..cams and ported S3 turbo and mani
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first off, he's got a fpr listed but no info on blocking the stock regulator. or a return line, and if your going to set the base pressure as low as 45 psi your going to need at least s2 injectors. with stock injectors at that low of a base the closed loop fuel trims will be way in the + zone.
no need to waste money on an intake, stock air box will work fine for all the mods listed.
a map clamp only works at one set voltage, fine for hiding max boost from the pcm, but worthless for tuning after you've upped the boost, you'll be way rich after the spike.
first off, he's got a fpr listed but no info on blocking the stock regulator. or a return line, and if your going to set the base pressure as low as 45 psi your going to need at least s2 injectors. with stock injectors at that low of a base the closed loop fuel trims will be way in the + zone.
no need to waste money on an intake, stock air box will work fine for all the mods listed.
a map clamp only works at one set voltage, fine for hiding max boost from the pcm, but worthless for tuning after you've upped the boost, you'll be way rich after the spike.
what you have mentioned is funny. i have been running this setup for close to a year now and have put down 288hp and over 300ftlb of tq. also the car runs great and is on stock injectors never going leaner then 12 A/f also if you payed attention to the fact that im using a fpr then you would know that 45psi is a base pressure that raise 1:1 so you get 50psi at 5lb of boost and 66psi of fuel at 22 psi of boost. im also clamping 4.7v. also i didnt say how to block of the factory regulator because i was trying to keep the post as short as i could i didn't say how to install anything out threw my post i just said what to get and in what order. as far as the factory air box yes it could probley flow anof power for these mods but the turbo wont have to work as hard with a good 3" intake wich gets you some hp and it let's the turbo spool faster.
Last edited by finfast srt4 : 08-01-2007 at 03:59 PM.
also if you payed attention to the fact that im using a fpr then you would know that 45psi is a base pressure
yes i payed attention, your on stock injectors, with fpr, your also running 45 psi base with stock injectosr on a pcm thats tuned to run at 58 psi, so all the time that your not in boost your fp is to low for stock injectors and the pcm is jacking up your fuel trims to make up for the low pressure. sure the wot afr may be ok, but the closed loop trims are way off. and unless you just like the look or need the extra room the stock air box makes 355hp with s3 so it's not over working your turbo,
if your going to bring up rrr's then the people who might follow your advice need to know that, to use them, you also need a return line and a modified fuel filter.
with a base of 45 psi and a rr of 1-1, your fuel pressure is below the stock 58 psi untill you reach 13 psi of boost. so, to correct that and give proper fuel trims, you either need to raise the base to 58 and use a safc to tune. or use larger injectors for the 45 psi base, with your set up ptb is even more lean than normal for an srt-4.
Last edited by camlifter : 08-03-2007 at 06:41 AM.
did you forget how super rich the srt-4 runs from the factory, not to mention the computer does not moniter fuel pressure. also as far as the intake goes an aftermarket one will always help yes you can squez 355 out of a stocker but i know you could get anothere 10hp on top of the 355 by adding the intake. just likeyou can gain 10hp out of a stock srt. its cheep power and helps make it easier to sqeez all the power out that you can.
this is the same setup that im doing. i have everything besides the return line, im running a good 17 to 15 psi, on stock 03 fuel system. af gauge is showing that i could crank it up more, but id rather play it safe. car is running steady strong and healthy.
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