smitty

I've been reading all these posts about purchasing various parts for the new mustang that require a reflash of the computer. I just finished reading a post in which some folks were recommending reflashing after adding a K&N drop in filter because they had done this and seen an immediate drop in mpg, etc.

My question is this: Is the new computer in these cars really smarter? I know it has megabytes and megabytes more processing power, but does that really make it better?

In the past, when I made a minor modification(like a K&N filter) to my car, the computer "recognized" the slight increase in airflow, made the air/fuel ratio good, and I received a small reward in the form of a little increase in power. I forgot about within 2 days of driving the car because 2-3hp gains are felt mostly in your mind, but still, the car didn't throw a cel!

Sorry, but if you have to reflash for a K&N filter, that is sort of ridiculous.

Seems to me that if this cpu was so smart, it should be able to compensate for a certain percentage of air flow change...just like the less advanced stupid computer in my '89 lx. Somebody please tell me why I'm wrong. :scratch:

Jeffs05GT

It doesn't make sense to me either the fact that you would have to recorrect for a K&N air filter. Seriously, think about how different the air is at sealeve and 6,000 feet, if the computer can compensate for that why not a K&N?

RRRoamer

I have a feeling that the reason it is so sensitive can be answered with one acronym: EPA. Given how tight new car emissions are (and how tight they will be in the near future), I bet the manufactures can't allow the computer to properly auto tune because the changes COULD be caused by a faulty sensor or an air leak or something else that could cause the car not to meet it's 5 year or 10 year emissions requirements. So when it identifies these changes, instead of tweaking on the fuel/ignition curves to make everyone happy, it lights up the old "check engine" light so you will have it taken to the dealer and they can plug in and check baby out.

Given that 70% or more of the folks out there will NEVER modify their car, assuming a large (large is definitely subjective) change is a problem and not a GOOD THING probably makes sense. Which means that those of us who want to play get to spend a bit more money up front and buy a programmer so we can fix things for ourselves without upsetting the computer.

And I don't know about you, but I LIKE being able to fine tune things and perfect my A/F and ignition curves (among other things!) instead of just having a computer "learn" a "good enough" setting.

SixtySix

I'm glad you brought this up Smitty. I was one of those that had stated that even a K&N filter swap would require a tune. There is one thing that did get lost in some of my posts on this matter, although it was in there, and in my signature.

Removal of the Hydrocarbon Trap.

So after my own experiments here's my results.

combined MPG before K&N filter and H-trap removal - 18.5
combined MPG after K&N filter and H-trap removal - 16.5
combined MPG after H-trap re-insertion - 19.5

The K&N filter alone does not cause a decrease in milage or performance.
The K&N filter along with H-trap removal does cause a decrease in mileage and performance.

Now that I've experienced the difference, I'll elaborate on the loss of performance I'm talking about, as I've previously stated that it was hard to tell if anything really happened performance wise.

With the H-trap out, after I got over the intial "wow" factor with the growl it had, something didn't quite seem right, and I've narrowed it down to this:

Removing the H-trap caused a big enough difference in airflow to have the computer compensate for the difference. This difference manifested itself in a number of ways:

1. loss of gas milage
2. decreased throttle response
3. less than optimal shift points (automatic)

Putting the trap back in, the car runs smoother, shifts when I expect it (less surprises) and my gas milage increased to 1.5 gallons more than I was getting previously with the paper filter and H-trap in.

So if you are just going to replace the filter, you're going to be OK.
If you want to remove the trap as well....get it tuned!

I think the H-Trap removal is a good low-buck way to see some small gains, but can only be realized by getting it tuned.

The only thing I miss now is the "growl" my car had with the trap out

Blk05GT

SixtySix-

Did you notice a drop in performance and MPG immediately after removing the trap? The reason I ask is that I removed my trap today during my dyno session and it improved both HP and torque a bit. Did the computer eventually compensate and kill the peformance or did you notice right away?

smitty

That makes a little more sense, I guess. But my point is that the older less sophisticated comupter would have also compensated for both the hydrocarbon trap removal and K&N filter, and would have rewarded you with more power and better fuel economy. These are not large changes we're talking about...not like changing a cam or something. I'm also not talking about gutting my cats and spewing unnecessary pollution. These are just simple bolt-on changes. One of the appealing things about the Mustang in the past has been its receptiveness to modification. This new cpu just seems unnecessarily persnickety. :angry: People have even reported cels from adding underdrive pulleys. That's just silly.

It won't prevent me from buying and eventually modifying the car, but it's just one more "big brother" kind of hoop to jump through if I want to enjoy my car my way and I'm just trying to ascertain why it has to be that way. :notnice:

SixtySix

I immediately saw a .5 mpg decrease in mileage, by the end of my second tank it dropped by a full 2 gallons.

The performance thing was very subjective...I didn't notice anything different until about the same time I noticed my milage went in the toilet.

Blk05GT

Thanks for the info. I will definitely keep an eye on my mileage.

Zodiac

There's something I dont get about this.. the H-trap basically converts unburned gas to something more economically safe.. Typically when its removed the car will see slightly increased mileage. If the computer isnt smart enough to correct for its removal, how is it then losing such drastic mpg?