Re: [DML] Cat removal

[Martin Gutkowski <martin@xxxxxxxxxxxxxx>]

Hi Gus

>As you well know, there are other differences in the USA/EUR DeLoreans 
>than just the cat.  
>
Actually there aren't. There was no "european specification" written 
down as far as I know. The ones with the wierd taillights were actually 
conforming to regs imposed at the time to register them. The closest car 
to "Euro spec" that left the factory is right-hand vin 5565. It has 
several minor alterations - aerial in the centre of the roof, side 
repeaters instead of markers etc.

The engine is definitely something else. I'm not sure if it's a 2849 or 
2664 but it has the auxiliary air valve instead of the idlespeed motor 
(but the ECU and wiring's all there). No lambda system and custom 3-way 
manifolds with twin link pipes to the cats, very like the stainless 
system only a bit tighter at the manifolds. I suspect it's an early B28E 
(late ones had the same idlespeed system as us) or a Z6W Renault 30 
engine. It certainly goes well.

>I'm not versed in these differences, but I know that 
>it's seldom a simple matter to alter a single variable within a complex 
>system.
>
As far as the cat is concerned, it is. It doesn't work properly unless 
the mixture's spot on under steady state conditions. That's what the 
lambda system's for. But it doesn't follow that you have to ditch the 
lambda system if you ditch the cat - you just get a free-er flowing 
exhaust. And trust me, if you compare the outlet of a stock cat to the 
outlet of a proper bypass pipe, you'll see the difference. This is a 2.8 
litre engine, and at red-line (which mine hits with ease) that's a lot 
to force through such a small hole!

>Removing the cat on US vehicles may or may not increase performance, and I 
>would like to see a dyno test that shows the difference.  
>
Given the dyno run would cost more than a bypass pipe.....

>Removing the cat 
>will almost certainly increase emissions.  If I could get another 10 or 20 
>HP by cutting out the cat, I'd be under there with a hacksaw right now. 
>But in truth I think it's 1 or 2 HP, which hardly seems worth the effort 
>(let alone the extra emissions).
>
It's not all about HP - this gives the engine improved torque - evident 
by easier overtaking (thinking of when I fitted mine).

>Don't worry about the higher emissions in your Euro-spec cars...you'd need 
>to leave every vehicle in Europe idling 24/7 before you'd even come close 
>to catching up with the USA.  We're #1, woo hoo!
>
And if we all drove around in 20 year old cars with no emissions 
controls whatsoever, the world would be a cleaner place today. Why? 
Because the amunt of pollution created by the manufacture of a modern 
car equates roughly to that from an exhaust pipe of a 20 year old car 
over 20 years. It's a mad world.

Martin





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