Several months ago I started a few threads asking about doing a 4v swap on a 98 GT. I completed the swap last May and have been driving the car ever since. The car starts, idles, and runs just fine. The only problem is that it just doesn't seem to make much more power than it did with the old non-pi 2v engine. The new set-up is as follows:

4v engine
C.A.I
Ford Motorsport Shorty Headers
BBK X pipe, no cats, 2.5" all the way back to excelerator mufflers

I know it's a short list, but should've been a big improvement over the original set-up. I am still running the stock GT ecu, and original 2.73 gearing. I plan to change the gearing before too long, but stock Cobra's of this vintage only came with 3.08's, and they fealt pretty strong compared to what I've got. Would the GT ecu be keeping the engine from making power?

 

Did you delete the IMRC controls? If not there's a huge problem, your stock GT won't know how to control them. But even beyond that... I would definitely get that thing tuned and you will probably see a big difference.

 

Forgot to include that, yes, IMRC deleted. I tend to think the ecu is an issue, but several of my techs (I'm a service advisor at a new car dealership) have told me that the ecu should be able to compensate for the new set-up. Having said that, I wonder if that ecu can provide the proper timing/ignition curve for that motor, espcially at higher revs. Manufacturers are recommending various reflashes all the time for certain issues, so there must be something to it.

 

Well that would be my guess... from what I have heard from other members that have done the swap the car will start and run but you're going to have a turd until you get that thing retuned. Think about it...right now that car's fuel and timing tables are set to redline at 6000rpms now you can pull to 6800rpms big difference.

 

When i first did my 4v swap in my 97 gt it only put down 180 horse on the dyno, you have to delete the IMRC and NEED to get a dyno tune otherwise it will never run to full potential.

 

You only made 180 rwhp? I just cannot get over how much that ecu can limit the power production. Okay, well this helps. I've not done any dyno tuning before, what can you all tell me about that? Like cost, what's needed in preperation, what to ask for, etc?

 

Well it will vary from shop to shop. Personally my shop tunes using diablo software, so the chip, the tune and the dyno time cost me $550. Some shops will charge you for the chip and then an hourly rate.

You'll just need to know the size or you MAF and injectors and a basic idea of what your modifications are.

 

you deffinately need a tune. the spark curve is different and all the ecu can compensate enough for it to run but my tuner (lidio at alternative auto) stressed not to get on it at all until it was tuned. it is also going to run lean especially at higher rpms. what injectors are installed in there? you should have the stock GT ones 19# in and then once it is on the dyno swap in the larger 24# or larger injectors. the cobra engine loves rpms and the power band doesnt really start until about 3,000rpms so put some 4.30s or 4.56s in the rear end. 4.10s if you plan to go with FI.

 

If you hammer on it before the tune it will not lean out it will do the absolute opposite, rich out. I hammer on my car for about 500 miles before the tune and when i pulled my plugs they were pitch black.

 

I made 185 stock with a CAI and flowmasters. Uber fail on that dyno day... Track time was 15.7 at 84mph. I was beat by a V6 Grand am that day.


NPI sucks old man *****...