Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing difference between 400cell cat and 200cell

I know im stating the obvious, but the first one is fitted to the librands manifold and the other to the aero manifold.I understand that the 400 cat is more restrictive than the 200 and will pass the MOT easier especially when older,but is the 400 too restrictive that you would notice the power drop with normal driving and is this why the factory will only give a clubsport flash to an ECU fitted with an aero manifold ,whilst the new enhancemet flash is only for the ECU with a librands manifold,any one have any ideas,duncan

Duncan,
this is only a guess but when I fitted the Librands exhaust & manifold to my 97 +4 they told me their 200 cell would fail the MOT & was only for racing, That was a while ago, I would guess 8 years or so.
Since then I have met people who have had the 200 cell & it passes the MOT now so it must be improved.
I have no idea on the extra power delivered but a more open catalyst implies lower bhp loss due to lower pressure drop.

I can't answer your question directly , but the performance of a catalyst degrades over time, especially in a car that is only used occasionally. Therefore a 200 cell cat that will pass the MoT now , may not achieve the same performance win the future.

My +8 OEM cats lasted about 10 years before replacement (and mine is a high mileage car at 3000/5000+ pa by comparison to many) . My second set lasted a similar time. They are becoming rare and very expensive.

IF I could be sure of no roadside emissions checks (and in London they are becoming more common) I would be very tempted to only fit the cats for each MoT and replace them with cat delete pipes for the majority of the time.

So do you think I would be better going for the 400 cat in order to get through future MOTs my p4 does in the region of 5000miles and is used all year,I am to old to be a boy racer ,but the existing manifold is dire,so I suppose any purpose made manifold is going to be better. I did not really wont to change all of the system just the manifold

duncan

Duncan, Unfortunately unlike the TR and Series one cars like you I have a cat on our Plus 4, when I get round to it I swap it for my cat link pipe which is a straight swap. I have had no problems with getting the car through the mot but there again its a 400 cell, if you have the software (like I do for my car) there is a setting to lean or richen the mixture which may be of use, but do store old factory default settings first!

I had the standard cat on my +4 from 97 and did roughly 5k miles. I never had an issue over 7 years and when sold the car had done 55k miles.

My Plus 8 is at around 45,000 miles, some 26 years old. Last week I spent a few days working on the base idle, and setting up the air flowmeter. At the MOT the CO at idle and fast idle was 0% (yes he did check that the engine was running), and the HC was 11 ppm (limit 200 ppm). I have heard of Plus 8s getting through with bypass pipes, but I have a friend whose GEMs Plus 8 only just scrapes through using the 'in service' limits, so I don't think it is easy to predict if a 200 cell would be good enough, on my 4/4 I ran a 200 cell during the year but needed a 400 cell for the MOT.