Janina993

I ordered full Mahle P/C set today. Hopefully will get them during this week.

I don't have a words how to thank you Kevin and Steve!

TB993tt

Back to the cats and mufflers - as Kevin said make sure you are getting the latest 130mm cats not the old stuff. As far as mufflers, go for the Cargraphic race mufflers NOT the sport ones - Race ones are fine for road use, not too noisy at all and they will flow the best.

Janina993

Yes I will. Cats are under construction right now and all the information I've got leads to bigger model.
Thanks for the tip. Does it sound more like marine or more like Porsche?

I found SuperFlow engine dyno where I could make proper drive-in for TS rings. Now I'm dancing between yes or no?

Rickard 993 Turbo

Hello

Can someone explain to me why the need of 130mm cats, why would not a high flow cat from randomtech for example they are like 105mm and 100cells

Kevin

Surface area... 130mm has more area.. The folk installing 100-110mm and 100 cell units trip the CEL due to O2 issues..

Janina993

apologize my english... what is CEL Kevin?

Doesn't internal cell design and material make difference in this issue?
Surface area is not the only thing what matters.

ttAmerica RoadsterAWD

I'm not Kevin, but I can help:

CEL= Check Engine Light. I'ts the big red "!" that appears on your dashboard when there's a problem with your engine.

Assuming thin honey-comb construction, I'm affraid surface area is the single most important aspect of a catalyst relative to fluid flow.

Consider this: 100 cells (tiny) in a straw vs. 100 cells in a 12 gauge shotgun barrel. Although both have 100 cells, you will be able to blow more thru the larger "tube" due to having larger surface area.

Stummel

it is 100 cells per inch and not per kat.

nevertheless you are right that bigger is better here

ttAmerica RoadsterAWD

Oh, yeah...what was I thinking at 02:30 am?? Thanks for the correction Stummel.

So, then, picture a fly screen on a straw, then the same fly screen on a larger diameter straw..... same squares per inch, but the larger diameter straw will flow more per unit time.

Jaime

Janina993

Now I got Mahle pistons. Part number is 993 103 915 58 weight group is -/-- 576-584g so max weight difference can be 8g.

Five of my pistons is weight group - and one is --.
I haven't weighed the piston yet because they are pre-assembled in cylinder.
Thing is you can't order specific weight group. You always get - or -- pistons.

What you think guys? Should I take them out from cylinder and make them equal weight? Or should I just install them like they came from factory?

I have thought I raise limiter to 7000rpm.

Kevin

You can easily take the RPM to 7200 with the engine build that you are doing.

Take your pistons to your local machine shop and ask them to balance all the pistons better than 1 gram tolerance.. Then you won't have to worry!! I'd recommend doing that anyway. While you are at it, take your entire rotating assy in and have balanced.. Pulley, crank, rods, flywheel, pressure plate.. Supply them with all the bolts.

Janina993

I have balanced crank with pulley, flywheel, pressure plate and bolts.

You are right Kevin. I have spend so much $$$$ and time for this engine.
Next summer when I'm driving along Rhein river valleys to Nurburgring, the last thing I wan't to do is worry!!

I will balance rods and pistons too.

Janina993

Quite big difference there was. Five - pistons weighted with all parts 584g and this one -- piston is 574g. 10g difference is a lot. My machine shop took 10g out from five wrist pins. Now all the rotating parts are balanced in less than 1g.
They machined cone profile inside both wrist pin end and they promissed it will be strong enough, generally used in race engines?

Now I'm back in plan to save rotating mass.
-connecting rod -76g/cylinder
-pistons -6g/cylinder
-valves -12g/cylinder
All together 564g from inside engine + 7kg from flywheel.

Janina993

I've got sport cats from Cargraphic. The small one...
3" before cat, 100mm cat, 2,5" after cat and 2,25" in muffler.
I send couple question for them and I've got following answer:
Is there any sense?

Kevin

That's false.. That statement is completely incorrect. You got wrapped up in the marketing..

Those cats are smaller than what you have taken off your car..

There have been plenty of articles and threads on Rennlist with regards to the CATS.. The Cargraphic or FVD 100 cell system is smalll and restrictive. If you want to get into more detail, look at the plenum right after the cat cartridge, there is no funnel of tapered reducing fitting. You have a flat piece of metal with a hole cut in it. This create more air-flow problems.. With all the money that they have made selling these units over the years, they need to re-evaluate the design. The minimum cat cartridge needs to be 130mm.