I have just acquired an 03' G35 sedan and love the stock performance, but of course it's making me wonder what it can REALLY do! Let me preface this thread by saying I am a 32 year old married Business Director for a Technical firm and cannot drive anything loud, lowered, or that can be in anyway frowned on by clients I transport.

That said what performance modifications would you sugggest to get maximum horses with minimum observable impact to vehicle.
I have $1000-$1200 to spend to get it done. I would love to get another 30-50 horses with that money. Is it possible?

I am new to the forum so feel free to give me any search advice. What I am most interested in is : What part? What brand? Cost? HP gains?

 

Others inevitably will say "do a search." To save you the trouble, get the MREV2 or 5/16th spacer (one or the other...they do the same thing). After that, get a ztube and popcharger. You'll have a nice growl without it being too loud. Finally, the rest of the money can go to an ECU tune...that will probably do it for your budget but you will probably gain about 20hp with a 7100 rpm redline.

 

My 03 5AT sedan has ran 6 passes at 14.3/14.4@97-98mph with nothing more than a Z-pipe that add about 0hp. I've also modified the airbox cover "Power Duct" to give the car a little more growl under part-throttle and WOT. Like yourself, I'm a 32 y/o professional, married, and have a very young son so mods that impact driveability, noise, and vibration are not my cup of tea. A few months ago, I installed the Motordyne 5/16" spacer and noted a nice improvement in power and a little more intake growl. I think the spacer should push my G into the 14.1-14.2 range at 99mph or so. I had the Borla true dual exhaust for about 7 days, but I removed it and sold it because it added too much cabin resonace and mild vibrations for me to deal with. The resonance wasn't horrible in the front seats, but for someone riding in the back seat (son, parents, friends) they'd probably get a headache and butt massage. The resonance got worse when more weight was in the back of the car. The gains weren't as good as I hoped either. The resonance issue probably would have been better if I had a 6MT and could keep the rpms outside the resonace range (1,800-2,500rpms). The vibration was caused by the lack of flex section on the y-pipe (OEM includes flex sections to reduce NVH). I considered installing flex sections on the Y-pipe (about $150), but I was still worried the resonance issue would bother me in the long term.

If you're anything like me, I'd suggest the spacer ($220, honest 10whp gain over the powerband) and Technosquare ECU ($500, 10whp gain). The Z-pipe adds a healthy growl and modifiying or removing the Power Duct cover (takes 1 minute to do) adds even better noise that you can modulate with the gas pedal. Everything else will compromise noise/resoance and vibration in the car.

Aftermarket y-pipes have proven to show no gains and possibly a reduction in low rpm throttle response

Headers can add about 5-8whp, but they're $400-1000 and are a pain to install (4-6 hours labor from a shop, 6-8 hours by a shadetree mechanic). Headers will also add a bit of exhaust rasp which gets much worse with other aftermarket exhaust components

True dual aftermarket exhausts can gain anywhere from 5-9whp, but they cost $700 and add significant resonance and noise compared to stock.

Underdrive pullies have shown very questionable gains and they remove the factory crank harmonic damper.

Aftermarket cats or tests pipes add signicifant rasp and questionable gains. Some aftermarket cats have a history of breaking the interal brick material which causes a nasty clacking. Both these parts also commonly have clearance/rattling issues and test pipes will cause a strong fuel odor.

Aftermarket piggy ECUs have shown 10-15whp gains, but they cost about $1,000 and require about $200-300 of dyno tuning.

Cams can show solid 15whp gains, but they shift the powerband from 4,200-6,500rpms up to 5,000-7,200rpms. In return for the upper rpm gain, lower end power is reduced and will often result in worse performance in the 1/4 mile, especially with an automatic. The cams also require an aftermarket ECU program to raise the rev limiter to take advantage of the new powerband. Cams are also expensive $1,100 and VERY labor intensive (~6-10 hours shop time).

Intakes $80-300 (Stillen, JWT, Injen, etc) add significant induction noise above 3,000rpms, but thier gains are again questionable and sometimes the cars show a loss of power.

The truth of the matter is if you want to add more than 15whp to this car, it's going to take a lot of money and you'll compromise noise and driveability. If you want to gains 50whp, then your only option is a supercharger or turbo and those systems cost anywhere from $4,000-6,000 plus about $2,000 in labor and gauge/safeguards and possibly a $1000 Stillen hood.

 

get the mrev 2 no spacer need with injen cai....clear conoro lights..tinited windows..rebadge her to skyline n 350gt...also checkout some aftermarket grills like the billet upper n lower grill..u might want to chnge ur bumper to the nismo front bumper n factory aero rear lip n aero side sills...so much more...i can go on for ever..u can upgrade ur interior lights to hyper white...rims...i can get the steill gen 2..its not loud unless u hit like 5-6k in the rpm band..but normal driving is fine..i dont like oud either...i have just traded my sedan in for a coupe...so...lol idk y i just said that..just figured u should know..any quiestions...ask me

 

That is one long *** run on sentence

 

Good summary Dave. I would add:

- on the UDP, although the HP gains and need for harmonic damper are debatable, throttle response is improved from my experience

- I thought test pipes had shown HP gains (but yes, they stink)?

- you did forget your favorite; aftermarket grounding wires have improved shifting on AT models as reported by many members, some reported no difference

 

The ground kit has made an incredible differance for me. I am getting around 3MPG more on the highway, around 1-2 in the city. I believe the driveability is much better as well.

 

That would be me I noted absolutely no difference in throttle response, shift response, mpgs, etc on my 03 5AT. I had the 10-wire GG kit for about 14 days then sold it.

 

You guys are an AWESOME resource! I'm going with the recommendations on the Z tube, Pop charger and spacer. I found the tube and JWT charger. Where do I find the spacer and installation instructions?

Tell me more about ECU tuning. Who does it? Is it a performance chip I can replace? Does it require any dyno work after? How much is the technosquare product? Any links appreciated.

 

I am a technical guy. Any have any idea how the grounding kits as said to "Improve MPG, drivability as well as transmission shift". Are there any side effects to these kits? I am not being sarcastic, just trying to understand how they work.

 

DaveB in the ATL nice feedback. The company I work for is based there. Great city!

I too have an 03 sedan. I installed the Jim Wolf charger, Z tube and Nismo ground kit. I like the tone it provides. The little whistle is just so cute too I also have a Crawford plenum but have not installed yet. Maybe this weekend. For exhaust I went with a coupe mid pipe ($75 from member on this site) and an HKS rear section muffler from Chad@InfinitiSpecialists ($350 picked up in person) This is an awesome muffler. This set up gives my car a slightly more aggressive tone than stock with NO annoying interior cabin resonance at all. Much better than the dual Magnaflow I had before.

Good luck, I hope that helps.