K24madness

The "learning" you speak of works like this.

There are two types of fuel trim. one is long term and the other is short term. The short term fuel trim will adjust rite away to any changes made (after warm up). The long term fuel trim makes broader adjustments that are applied like a correction factor and are displayed in percentages. You can view both with a good OBD2 scan tool. Maximum percentage of adjustment is +/-25% before you will get a fault code.

Ignition timing works a lot different. When the ECU detects knock it pulls lots of timimg to keep thing safe. It will bring the timing back very slowly in very small increments.

Ready codes are set after approx 50 miles of driving. These are required to pass smog in california. The 97 ECU seems to set ready codes within this mileage without a problem. The 96 ECU has a lot more trouble. It is known that even after 2,000 miles of driving on the 96 ECU that ready codes still may not be set. The California DMV has a provision to allow 96 cars to pass smog even if the ready codes are not set.

Hope this helps

Tom

Woodster

Tom,
sorry for the "doltish" question but here it goes:

Does the ECU in my Watercooler (996TT) work the same way as you
described ??
thanks in advance.
Marty

K24madness

Marty,

Your ECU behaves the same for fuel trim. Not 100% if you have the 25% range. It may be closer to the 15% adjustment range.

The way the timing is adjusted on your car is waaaay more advanced. It uses correction factors per cylinder and allows the timing to be adjusted rite up to the threshold of detonation.

All of this still does not get you around tuning when adding larger turbos etc.

Tom

CP

Tom, Kevin,

Thanks for the education.

My RUF is a very strange duck. It is a 1995, but has OBDII. However, it is RUF's Motronics system so not all OBDII readers can read the code.

CP

LAT

Just a point of claryfication.

Claudio @ Foreign Sport has 130mm cats that are 100 cell. I believe these are the same as what RUF uses in his conversions. There is also mention by others in this thread of 130 cell cats, I believe this is referring to the same thing.

Am I understanding this correctly?

Thanks

LAT

ACEparts_com

Well, everything is back together and I'm mighty impressed. Full boost is available from just 2900rom and whereas it used to run out of puff at aroung 5,500 it will now pull hard to over 6K and will even pull into 7!
The 130mm 100 cell cats are great!

Miles965uk

Did you get your cats from actperformance.co.uk? The website doesnt work. Just wondered if you have their contact details.

Great to hear the performance improvements!

CP

LAT,

Claudio did my 130 cell CATS. You are correct.

CP

Kevin

I use these same 130mm cells in my programming kits. Have a set on my shelf..

ACEparts_com

Sorry, www.actproducts.co.uk

130mm, 100 cell. I then had an engineering company weld them in. What they did was weld a couple of studs to a bench, bolt the cat to it and then weld some small box section to various points along the cats to ensure nothing moves when the old cells are cut out.
They then rolled a sheet of s/steel to 130mm inside diameter, weld it up, weld the cats in the new tube and then weld the tube in place of the original cats!

The overall diameter increases by 2-3mm. The alignment is critical to say the least. I've really very happy with the performance increase (using an RS tuning stage 1 ecu).

I still have some'fluttering' in different parts of the rev range but am currently putting this down to
1) only driven it 100 miles so the ecu is probably still learning
2) slightly stale fuel
3) Hot weather so timing/boost may be being pulled.

I bought a new S oil cooler and then came across another so may have a go at making it a twin S cooler.

Kevin

Ace that's incorrect. The stock cat "cell" measures 120mm in diameter.. The factory cats have a 120mm diameter insert. One end necks down to 118mm. So you actually gain 10mm of better unrestricted flow when you weld the 130mm cell to the outer stainless tube/casing.

ACEparts_com

Sorry, Kevin, I ommited that detail! The stock 993 cat is only 120mm in diameter with an outer casing of 130mm. The overall diameter only slightly increases but the cat diameter goes from 120 to 130mm. The 100 cell cats are only half the length.