CalBoy101

I just bought a 2002 GT convertible, totally stock, and I'm having a blast with it so far.

The only bad news is I'm going broke, I didn't know there were so many add-ons available for it.

The first thing I ordered was AM's Airaid CAI/Bama tuner combo, the dyno improvement they claimed on this combo was pretty impressive.

The plan was to start out with that for a while and then do the exhaust later. But I couldn't hold out and even though the tuner/CAI hasn't even got here yet I also ordered the MagnaFlow catted 2.5" X-pipe and Flowmaster's American Thunder exhaust, both also from AM.

I wanted to ask a question about this from the Bama guys but I haven't been able to find an email address for them but I noticed that the AM/Bama tuners often respond to questions on this forum, so here goes:

When I originally ordered my tuner I wasn't planning to get the exhaust system yet so the only non-stock component I listed was the Airaid CAI.

From what I understand switching to a different cat back system doesn't effect the tune but switching to a non-catted X pipe does require a new tune.

The Magnaflow catted "Tru-X" X pipe does use "hi flow" cats and it also has only one cat per side versus the 2 cats per side that the stock system has and its also 2.5" so it appears that it flows more than the stock system. Magnaflow describes the system as for "off road" use only.

Do I need to request a new tune from Bama now that I'll be using this exhaust system?

cliffyk

The only tune change required for a "non-catted" o/r X-pipe would be to have the catalytic converter monitoring (rear O2 sensors) disabled--if you have installed the Magnaflow "Tru-X" catted pipe then no changes are needed...

CalBoy101

Cliff, thanks for that response.

Actually I've already read several of your posts, I've been reading up on the 4.6 engine in the forum and hit your explanation of why Ford switched from the 19# orange injectors to the 21# pink injectors in late 2002.

Since my GT is a 2002, after reading that I ran out and popped my hood hoping to see pink but no go on that one, I've got the 19# orange injectors.

I decided to get a set of the pinks, I like starting off with a set of cleaned and tested injectors anyway so I scored some off ebay ($80. inc shipping, not too bad) and I'm going to send them to get cleaned and flowed.

This is also making me wonder about my Bama tune, they asked what year my car was but not what injectors (other than they are stock) it has so at this point I'm not even sure which ones the tune will be for.

Based on your other posts, I'm assuming that when I pop in the 21's I should ask them for a new tune, correct?

Actually I guess before doing that I should ask them if this first tune is for the 19# or 21# injectors some cars in 2002 could come with either.

cliffyk

Ford did not change the stock tune when they switched to the 21 lb/h injectors, and used the same low and high slope values¹ as with the 19 lb/h units. This bought them a richer mix at high loads and WOT--as rich as high 10s--and less likelihood of anyone blowing up the engine running 87 octane swill.

You can safely run with the 21 lb/h injectors, but let them know you have them when you request your next tune. Also you really should have a wideband O2 system if your are serious about dialing in AFR.

As indicated in the footnote I have found low and high slope values of 24.10 and 20.50 lb/h to be much better with the 21 lb/h (pink) injectors--feel free to pass this along to them and mention my name...

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¹ - New-edge GT tunes almost all have the same low and high slope injector scalars of 23.76 and 19.15 lb/h respectively. Better values for those engines equipped with the 21 lb/h injectors are 24.10 and 20.50 lb/h. This will lean out the open loop AFR and gain 5 to 7 HP across the mid and upper rpms in open-loop mode.

CalBoy101

Cliff, thanks again for that detailed response, I really appreciate it.

As long as you are allowing me to pick your brain, a couple more questions for you-

I'm trying to hold off on the WB purchase at least for a little while but while I'm putting the exhaust in next week I'm going to weld a bung in the new pipes for a WB sensor.

What's the best location for this sensor?

Also on these motors, what WOT fuel air ratio do you aim for?

Also, I guess out of curiosity, when does the ECM go open loop in these cars, is it only when they are floored or at some MAP threshold or???

cliffyk

An easy to get at place is about 6" downstream of the passenger side front O2 sensor, at about 1:00 looking up at the pipe. I was able to drill a hole there with a right angle drill and a 3/4" step bit, and weld it up while installed in the car:



I target 12.7 to 12.8:1 at WOT, a bit richer than many recommend however it let's you be more aggressive with spark advance without risking detonation. There are no knock sensors on the 2V engine so it's up to the tuner to get it right and if needed err on the side of caution.

The PCM switches to open loop when the throttle position sensor output voltage rise beyond 2.71 V, this corresponds roughly to the throttle being open greater then 55%:



Other considerations are ECT, engine load, etc. but throttle position is the main trigger...

CalBoy101

Cliff, thanks a ton, that's some very useful info.