Calling Gransport owners - a few questions

FIFTY

Member
Messages
1,661
The primary cats are in the headers on my facelift 4200...Both lambdas are situated here...so there is no impedimant to replacing the secondary cats with a a straight through substitute, if thats what you mean..? Emissions are tested at MOT at the tail pipe, as im sure you are aware. If the 2ndCats are deleted, emissions will go up...Im confident in that being fact. The older the cats, the less eficient they will have become too. All part of the puzzle.
Id probably be happier to "pootle" about if I could hear that lovely cross plane crank, which would be good for my licence ! Not so much my neighbours, I fear ! :D
I thought you were talking about the rear boxes effecting emissions. You have cats in your manifolds and front pipes

My view is if there is nothing wrong with your cats don't touch them. If they are shot then get Larini Front section because of the quality of the cats they use is superior to the majority of what is freely available to weld in to a custom pipe
 

hashluck

Member
Messages
511
That would be great - what do the Larini valves rear boxes add over the normal GS rear boxes? Aren’t they also valved?
Yes the standard GS boxes are valved. Most aftermarket alternatives are not, other than the Larini option as far as I know. Someone will need to educate me on why you would change the back boxes at all unless the originals are knackered.
 

D Walker

Centenary Club
Messages
7,440
Are they Larini front cats, how does the height of the bend compare to the squish pipe bend.
 

Evo Cymru

Junior Member
Messages
512
I want to do this...the 4200 is so very quieted, its a shame. Gutted back boxes aren't for me.
...but it would be such a ball ache to find it failing on MOT emissions testing as a result.
Was assured by my MOT guy that I was well within the limits before I changed them over - going to pop up again soon and get them checked but have had no codes/faults yet....
 

TimR

Member
Messages
1,013
Was assured by my MOT guy that I was well within the limits before I changed them over - going to pop up again soon and get them checked but have had no codes/faults yet....
Every car is different
USA spec ?
What are the emissions data saying ?
 

Gp79

Member
Messages
976
Different set up to mine
And they’re just more cats...! :D
Yes still one pair of cats, the primaries are gone that is just a section of pipe at the front, also less cells on the remaining one pair.

Do you run with no cats at all? Interested how do you fool the post cat o2 sensors into thinking there is a cat in the system and not giving a CEL?
 
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Evo Cymru

Junior Member
Messages
512
Every car is different
USA spec ?
What are the emissions data saying ?
US spec headers so now just running with one set of cats (second set further down removed). No data yet but will post when I get it checked again....
 

Spartacus

Member
Messages
2,703
Im after a set of US spec de-cat pipes (2 bolt flange) but £1k seems a bit steep . Has anyone found any cheaper alternatives out there ? Iv made enquires but nothing so far
 

TimR

Member
Messages
1,013
US spec headers so now just running with one set of cats (second set further down removed). No data yet but will post when I get it checked again....
You wont get codes because the lambdas are both in the primary cats in the headers....2nds are only there for idle emissions test for EU whatever it was ( EU3 at the time i shouldnt wonder?)
Im sure that if the earlier cars can delete their primary cats and get thru with 200 cell 2nds, it must be, maybe, possibly, at least plausibly in the realms of perhaps...!?!?!!
I ve read forumers claim they have no issies. ;ikewise, the next post is proof that not all cars are the same and MOT failure was the result...! Do post data. Id like to at least try and make an educated stab at it...?


Im after a set of US spec de-cat pipes (2 bolt flange) but £1k seems a bit steep . Has anyone found any cheaper alternatives out there ? Iv made enquires but nothing so far
There was a set of Larini going 2nd hand a while back for £500..
Id be looking to a decent custom pipe shop to make a set...
 

rockits

Member
Messages
5,630
Are the Larini replacement CATS metallic or ceramic?

Would I be right in saying most CATS breaking up and causing issues are ceramic?

Metallic ones don't smash if you hit something just sent/ deform then stop working as well. Also don't break down when going from silly got to silly cold maybe when hitting cold puddle of water with hot CATS.