jepostang

Hey guys this is my first posting.
I just installed JBA shorty headers and a bassani o/r x-pipe.
Since the install, my car seems like it doesn't have as much power as it previously did.

Before the headers I was running 13.9 @ 98.65.
After the headers & x-pipe I only ran 14.1 @ 96.4

I have a 1999 Mustang GT with the following mods:

K&N cold air intake FIPK
Superchips programmer on the "performance tune" 91 octane +
Professional Products upper intake plenum
75 mm Professional products throttle body
Ford racing 3.73 gears
JBA Shorty headers
2.5 in Bassani offroad x-pipe
2.5 Borla cat-back
GMS boots and wires on the stock coil packs

My first thought was now its breathing a lot better and might be running too lean. Should I have to change out the fuel injectors?
I just replaced the spark plugs, I had Autolite double platinum and now I have the stock Motorcraft plugs.




Thanks for the help!
-Jeph

Poobs

How many runs at 13 are you comparing to the 14 sec run ?

Did they screw up the O2 sensors during the intall ?

If you were comparing dyno runs before and after the header install I would say you have a definite problem but ETs change depending on many things....

hotrod7687

I havent made a run at the track yet, but I could definately notice a change in the powerband when I installed my mid pipe and cat back. I lost some torque on the low end, but gained a noticeable amount on the top end. Thats due to the larger more free flowing pipes reduce your exhaust velocity at lower rpm's which affects low end torque, but helps flow in the upper rpm's. You might trylaunching off the line with the rpm's a little higher. If you have an auto, the loss of torque could have an effect on your times if you dont have a stall converter.With amanual I would suggest launching from different rpm's and see if that helps.

Like poobs said make sure the O2 sensors are working correctly. Did you install mil eleminators or turn the rear O2 sensors off with the tune? If not that could be your problem.

eventer289

You are only running a 13.9 with all those mods and 3.73 gears? Something is wrong because stock stangs can run a 13.9.

My bet is that your A/F could be too lean. Headers gain HP but lose torque because of a loss of back pressure. You might "feel" that you have lost power only because you lost a little bit of torque. What you arent feeling is the extra HP on the top end you have gained by allowing the exhaust to flow more freely.

I'd get a tune, especially since you have a 75mm TB and headers. You probably are running pretty lean.

mvr

shorties dont ad that much power... IMO go longtubes or stay stock

also from what ive heard x-pipes loose a bit low end tourqe but gain mid-high range hp/tq

code3GT

99 GT with coil packs? Something doesn't sound right.

jepostang

coil on plug, sorry for the confussion. I just replaced the boot and replaced the stock spring type wire for a solid core wire from GMS.

As for installing mil eliminators or shutting off the o2 sensors I have not. Would the car run poorly if the rear o2 sensors aren't turned off?

Yeah, that 13.9 was with BFG drag radials. It's a 5 speed and the car has about 89K.

I would have assumed with the mods I have, this should be in the mid 13's.

I am hoping it is just running lean, should I change to 24 lb injectors?

Thanks guys.

code3GT

If you are running lean, you would be making more power. And "yes" the O2 sensors can have a major influence on power.

hotrod7687

You need to do something with the rear O2 sensors. The computer is sensing that the cats arent working right (true cause they arent there). You shouldnt need larger injectors at this point. Is your check engine light on?

There are 2 ways to cure the O2 sensor problem.
1. Buy a set of mil eliminators. They plug inline with the rear O2 sensors and trick the computer into thinking that the rear sensore are getting the right reading. They cost roughly $60 Heres a link:
http://www.ninosport.com/Dallas-Must...mp;category=86

2. Get a tune that turns off your rear O2 sensors. A SCT X-Cal2 or a Diablo tuner can take care of that for you. This would be the best way, but definately more expensive.

jepostang

Thanks for the responses!

If my air fuel ratio isn't good, then either it would run too lean or too rich, which in both cases would make the car run poorly.

I will buy some mil eliminators and hopefully that should help fix this issue. I have the old school Superchips Programmer, which only gives me 2 tuning options, 87 octane or 91 "performance tune". Has anyone heard of a way to download or add tunes to this Superchips programmer? or would it better to just buy a diablochip tuner or SCT tuner?

I talked to my mechanic and he told me that the Stang is breathing a lot better and that it is probably not getting enough fuel. Anyone else think I might need larger injectors? or maybe a hi po fuel pump? Maybe have the injectors flushed?

Thanks for all your help!
-Jeph