I had posted this on another forum that was having a flood of "I want more HP for cheap?" posts--thought I'd post it here as well.
A very common post on nearly all automotive and powersports related forums is "How can I add HP to my [fill in the blank] without spending a lot of money?".
The real answer to this question is "You can't.", however with the New-Edge Mustang GT it is possible to spend your money wisely and wake up a stock engine incrementally, without devastating your bank account.
So FWIW here are my complete best-bang-for-the-buck
"bolt-onš" recommendations for livening up a dead stock New-Edge GT (excluding active power adders)--in this order:
- Open up the exhaust;
2-1/2" from the manifolds back, H- or X-pipe as you prefer (the H-pipe will favour the lower end at the expense of HP above 5300 rpm or so). "Soundwise" think H-pipe = Musclecar, X-pipe = NASCAR. Some say that H-pipes sound better with chambered mufflers, and X-pipes best with straight-through mufflers--I am one of those.
Catted or non-catted ("off-road") take your pick, it doesn't matter. There is no power advantage to the o/r pipe as compared to one with so-called "high-flow" cats; just more noise, stink from the tail-pipe and potential emissions testing problems if you live someplace that does that sort of thing.
The stock tune sucks. The ignition timing is quite uninspiring and it runs very rich in open loop mode (high loads and WOT)--pig-rich on the late-'02 through '04 MY engines with the pink 21 lb/h injectors.
I have never tuned even a dead stock New-Edge where the owner did not come back from their first ride with a big grin. The tuner will also let you correct the speedometer when you get to mod #3. Run a tune optimised for the highest octane fuel available in your area. The increased cost will only be $3.00 to $5.00 per tankful so just have one or two fewer beers and/or lattes in between fill-ups and enjoy the added power.
- Final drive gears;
I will not get into what ratio as that is for you to decide, though I will say that for daily drivers I recommend 3.73s. Here is a link to my How fast can I Go in Each Gear? calculator that can provide some useful numbers to help you decided.
- TB/upper plenum;
The stock upper plenum is the weak link in the intake tract, this appears in dyno charts where you can see engine output drop off sharply after 5500 rpm--installing an aftermarket plenum and TB will let the engine pull strongly right up to the rev-limiter.
Any aftermarket plenum, with the stock 65 mm TB, will outflow the stock plenum with any size TB--here are Accufab's flow bench numbers, annotated by your truly, that show this. There is no need for a TB larger then 70 mm, which is optimal, however larger units will not have significant negative effect.
- Fuel injectors;
If you have the orange 19 lb/h injectors upgrading to the pink 21 lb/h units is worth the cost and effort. The 19 lb injectors are running near 90% duty cycle at the stock 260 fwHP output (flywheel HP). Ford realised this and changed to the 21 lb injectors in the late 2002, 2003 and 2004 MY production. Unfortunately they did not change the tune, which is why those models run pig-rich at WOT.
The 21 lb/h injectors run just under 80% duty cycle at the stock 260 fwHP.
At the top end of what can be expected from bolt-ons you may wish to consider 24 lb/h injectors as they will be operating at 80% duty cycle at 305 fwHP, or 260 rwHP--which is about the limit for the modest bolt-on modifications presented here. Operating at 80% duty cycle means they will be consistent and well-controlled, and provides reasonable headroom.
There is no power gain worth the $$ to be had with any aftermarket CAI. The stock intake is a CAI and a very good one to boot. The same holds true for drop-in air filters. I made 262/305 rwHP/lbft with the modest bolt-ons listed here, a finely honed tune, UDPs and the stock intake with a Purolator paper filter--that's all you need.
Other mods such as underdrive pulleys, lightweight wheels (all else being equal 18" wheels/tires weigh more than 17"), flywheels and driveshafts can improve acceleration by reducing parasitic load and rotating mass. However if you are the sort that never "floors it" and always shifts at 3k rpm then don't bother; you will never know they are installed. Their benefit is only realised under hard acceleration and mostly in the lower gears. I consistently hit the rev-limiter in 1st if not paying close attention.
Weight reduction will always improve performance, even if you are sort referred to above. Note that adding a super boombox audio system is NOT weight reduction.
That's it, just about everything else you can bolt-onš is cosmetic, things that if they make you happy are great, but don't expect any WOW in-your-face performance gains.
This is all my opinion so comments are welcome, however I do not care to argue about any of it or be told I am wrong--it really is my opinion...
š - Technically superchargers/turbos and NOS are "bolt-ons" in that one does not have to disassemble the engine to add them. But for the purposes of this discussion I have excluded them.