De-cat pre silencer

[Guest]

Hi Folks
As my 87 model carrera was a german import it has a cat fitted.Some time ago I bought a stainless steel pre silencer to replace the cat.The proprietor who sold me this explained that the lambda probe could simply be clipped into a bracket above the box with no detrimental effect to the management system,presumably whilst it's in oxygen of some level then it's happy? Yes/No?
Anyone else carried out this swap and will I see a return to the uk output of 231brake ? As I'm about to go ahead,now time is on my side, your input will be most appreciated[]
Thanks.Ian

 

[Jacob]

Ian,

I also have a '87 German Import - although mine did not have a cat fitted. (I believe that most US cars had Cats fitted as standard).

I am almost sure that all you need to do is unscrew the hex bolt on the top of the pre silencer and simply screw in the Lambda probe and it is really as simple as that![]

As for the power gains - you car should be 231 bhp, it was only the US cars and the Japenese cars that were 217 bhp.

good luck

 

[Guest]

Thanks for that Jacob,
My presilencer unfortunately doesn't have the threaded aperture to accomodate the lambda probe so it looks like it might be a case of "suck it and see"!
Ian

 

[Jacob]

Does the Lambda probe have a thread?

 

[911sse]

When you put cars as old as ours onto the rolling road, you
find that the bhp output is closer to 220-225 according to
Wayne Schofield from Chips Wizard.

Mine came up at 221, no mods or re-builds, Going too try and catch up with
Wayne in 2005 and get him to re-map the car. He did a coiuple of guys cars at
Star Performance in Glenrothes last year with great feedback from the owners.

 

[Guest]

To quote from the Bentleys manual on refitting of the oxygen sensor:"apply some anti seize compound the threads before refitting"
.......So I think ,"yes" would be a fairly honest answer to that Jacob.[]

 

[Guest]

Quite happy to accept that due to age etc that power would be down from from a new/rebuilt engine but just wondered if everything else was the same on german market cars as uk bound models of that era?[8|]

 

[Guest]

Bit the bullet today and fitted the stainless decat presilencer.As to my question concerning the oxygen sensor :I cut the threaded boss out of the old cat,cut a 25mm hole in the new silencer and tig welded the boss in place to accomodate the O2 probe.Removal of the cat would have been impossible without my air chisel as the old bolt heads were none existant! All new gaskets and bolts fitted but haven't fired her up yet as I've got the heater flapper boxes stripped down and sent for shot blasting ready for painting and refit.Life in the pit is not good for the neck muscles.....Creak!!
Ian

 

[Jacob]

let me know what you think re power gains once you have gone out for a blast

 

[Guest]

ORIGINAL: CTJM

Quite happy to accept that due to age etc that power would be down from from a new/rebuilt engine but just wondered if everything else was the same on german market cars as uk bound models of that era?[8|]

Best way to tell what spec your engine is, is by the engine number type number. Standard Euro (non-cat 231hp) models have number 930/26 engines. The 217Hp models have lower compression pistons fitted and and a cat with serial # 930/25.

I think in the US, early Carreras had a cat and "only" something like 207hp. I think these get bad press as they were a fair bit fatter than their predecessor the SC without many extra ponies. i think, but am not sure, that they are 930/21 engines??

 

[Guest]

Went out for a blast in the sunshine today Jacob,lovely new deeper warble from the exhaust now and she's definitely breathing easier.There is certainly a more responsive "urge" feel to the drive now so as you can guess I'm very happy with the result.I've also just fitted the chin and rear spoiler which seems to have a made a noteable improvement to stability over "certain" speeds!
Ian

 

[Guest]

Srange one this Chris
Will check out numbers again but seem to recall doing this when I bought the car and it tallied up with "rest of world" spec so should be running the higher compression.Other people have said their german cars didn't have cats on so it does seem a little odd!Must do some more homework with the engine numbers.
Ian

 

[Guest]

Did some numbers homework ;930/20 rest of world spec engines have the full compression/output of231bhp(which mine is, as were uk bound motors).
930/21 engines were US and Japan units up to 1986 then became 930/25 units.
930/26 engines were swiss.
All my chassis and engine codes tally with euro/UK numbers but there (was) the CAT which apparently by late 1987 85% of all Porsche models were fitted with as standard.(my car is an 87 year model).
Still no specific output figures though for 930/20 with cat. Even US cars were remapped to give 215bhp by this time!!!!
Good excuse for a trip to a rolling road and maybe a "Stevie Wong" pick me up!Ha Ha.
Ian