fraggle

I'm getting the rear bits that connect to the stock system custom made. I have all the parts but they need to be welded up and installed. I've got flanges in the middle to keep serviceability intact.

Ketchmi

Surface area matters greatly in catalytic converters, the diameter of the body should be at least 4". The shorter the cat, the less efficient it is but the less restistance to flow. The fewer CPI (cells per inch), the less resistance to flow. So...larger diameter, lower CPI and less length are great for flow but bad for efficiency. Smaller diameter, higher CPI and longer length allow more complete cleaning but at the cost of exhaust restriction.

Avar928

Thanks Dave. I'll double check on the diameter but I do believe it is at least 4". I left my pipe with them to start on it with the grind but I have a ton of pictures and the clamps to compare and estimate. The stock cats are 4" in diameter (or more?) but longer I suppose.

What shop did you go to Fraggle?

ASG said they'll fabricate a system for me for the cats. Plan is to grind the weld and remove the residual cat-back (which on the inside was inserted a good way in where it made a small ledged cavity) then weld a length of pipe to the cat which will mate up and clamp to the catback system. They'll preserve "removability" of the performance piece for when I do work underneath the car if I'm required to drop it but make it so it won't leak.

Stromius

Please post when you get this done because this is what I would like to do.

Do they have 2.5 -> 2.125 clamps? 2.5 to 2.25 seems too loose.

Ketchmi

No Stefan, I don't believe anyone makes them in that size. They are meant to be impacted on and they do keep tightening up. They will seal and hold quite well if they are not already stretched out. Really, tighten then way beyond where you think tight is. They should be able to pull up until there is no gap around the center aluminum channel.

Avar928

Dave,

I'm convinced the seller made a mistake and sold me your 100 CPI. I'm now concerned about smell and passing emissions since the CPI is low. Should I be worried? What's the life on them? I've been reading up on threads about your cats specifically and it's giving me peace of mind that I'll be okay but I really don't want my car smelling up something fierce. I can't stand it personally (I have an employee who drives without cats and I make it a point to never be behind them on the road).

I may call the shop and tell them to grind the front end instead and mate the X-pipe to my stock cats. I have an appointment on the 26th so I got some time.

Ketchmi

The 100cpi cats work perfectly well with a properly running 928, if all is well with your engine tuning it will pass emissions for many years. If your engine runs like crap even the best cats out there won't clean it up enough. The 100cpi are the only cats we have sold with the system for at least 5 years.

The stock cats are old technology and need an injection pump blowing fresh air into them to fire them off quickly and properly. You can also sell your old cats currently for $150-$200 to a recycler if they are in good shape.

Avar928

Thanks Dave.

She runs strong, idles perfect, but still a bit sluggish and down on power. I've done a lot of work on her myself that's engine specific. I have a TB/WP/Gear job up in a week or two, also going to correct the timing.

O2 sensor is original I think, I'm having the shop put in a new one that I bought from Roger when we swap out pipes and cats.

I plan on keeping everything for now. Stock units are becoming rarer so who knows how much they'll be worth (or I'm just being too optimistic).

SMTCapeCod

Send up some smoke signals if you're open to some local assist with the t-belt work. I have the Porken tools for setting the cam timing. Or they are in the O/C loaner program, too.

Also, re: sluggish, have you already run through the vacuum lines-- and checked the Vac connection to the computer?
Just a WAG.

Avar928

It's the transmission. I haven't gone through it yet. Timing is off I'm sure.

Thanks for the help! Fraggle and Brett are coming to help. What weekend are you free? I was thinking next weekend but I may have to push it back. We got relatives coming over.

Ketchmi

I recall an 86.5' that we bought in Cali once that wouldn't pass emissions no matter what they did...I found that one cam was a tooth off. After we found that, it purred and easily passed emissions.

Avar928

I plan on installing Ken's latest chips as well. She should pass despite the changes to fuel mapping?

Ketchmi

You would have to confer with Ken on that one, I do not know yet. (I am getting a set myself!)

Avar928

According to previous threads asking the same question, Ken's chips make your car cleaner.

Wow. I'm looking forward to that

Avar928

Update:

Got her back from the guys at ASG in Fairfax. These guys are professionals and very knowledgeable about 928s. They actually hosted Frenzy years back twice http://www.autosportsystems.net/

I highly recommend them! Great group all around. Fair pricing and they know their stuff and appreciate the car. They're now my go to shop for any work I need done that I can't do myself.

Anyways, they installed the X-pipe and fabricated me a system so I can swap as needed and remain "stockish" for the rest of the exhaust.

They grounded away that weld and removed the previous owner's cat back, one of the cats was off center so they heated it up and bent it so it would line up. Then they welded a length of pipe to the cats so that it flare and match up with the cat-back system. Used the factory clamps and mated the system all up. If I need to swap back to the factory setup, I just unclamp and plug the stock system back on. Simple.

No leaks and she sounds AMAZING. I was astounded regarding the difference in feel, power and sound with the pipe and cats. She growls and roars off of first and all the way through. I'm falling in love, it's just...wow.

No words. Will post pics up when I can get her on stands. Thanks to Dave on making an absolutely gorgeous product and thanks to ASG for putting all together for me!

ADD ON:

I'm also now selling those new clamps and strip of fiberglass wrap. Selling it for what I paid for it. PM me if anyone wants them.