Thread: 3.9l Extractors...gains worth it?

Originally Posted by Traco

Aus market Discos1 got no cats or lambdas, and low compression engines unlike their UK counterpart.

The OE exhaust manifolds are quite efficient and help make torque. I recommend you keep them and concentrate on the rest of the exhaust system from the Y back - 2.5 inch pipe + freeflow muffler (e.g. Supercat) + freeflow resonator.

totally agree, we did this and the 3.5 now revs it t###s off:}

Originally Posted by mike 90 RR

I have been quite surprised about the "No Cats" fitted on the early unleaded models ... As I am use to seeing them on "other brands" that use this fuel (example ... Ford EA 1988)

My understanding on the concept of the cats, is to super-heat the exhaust and burn off excess fuel & gases ... so they get rid of the rotten egg smell & to also help meet the emission's standards /// and for such thirsty engines, They met the standards without cats?? ..... ....


and Yep ... I know of a couple of folks, in the past, that have had restrictions of the exhaust system due to the baffle coming loose and blocking the exhaust passage

Mike

I have a 4 legged cat converter, called an American Staff. Havent seen a neighbours cat for ages, starting to wonder if they have too....

But seriously, a cat converter doesn't super heat anything. It cant get it hotter than the exhaust passing thru it. The "burn" is a reaction between the exhaust and the catalyst on the substrate effected by the excess oxygen present in the exhaust.
It reduces emissions such as nitrogen oxides to nitrogen & water, oxidises carbon monoxide to carbon dioxide and converts hydrocarbons to carbon dioxide and water.
To do this effectively the temperature of the exhaust needs to be a certain temp to allow the converter to effect a chemical reaction from the exhaust gases passing thru.

The early 3.9 didn't have it as all of them released here ran an 8.13:1 CR, effecting a lower emission outputs from lower combustion temps. One problem is that carbon deposits are more prevalent hence all have sooty exhaust pipes
Not sure why they wouldn't just blanket manufacture the same thing for all worldwide. Imagine, we all would be running around with 9.35 engines....

As for the rotten egg smell, this was the side effect of the cat converter in the early days as they produced hydrogen sulfide as a by product after converting other gases. Although unpleasant, they are not particlarly toxic compared to everything else coming out of your exhaust.
This is a bit different now as washcoat materials contain various additives to react and control this although you cant totally remove it.
All converters now are a 3way as the early 2way couldnt control NOx.

And then we get into diesel cat converters, same principle but have a different avenue to attack.
Isuzu have a method of reducing particulate emisions to 1/6 of their previous engines and in my line being Mercedes Benz, we have an additive called NONOX which is basically urea which is added to control NOx from the exhaust.
Cheers

Andrew.

Originally Posted by LOVEMYRANGIE

The "burn" is a reaction between the exhaust and the catalyst on the substrate effected by the excess oxygen present in the exhaust.

..... Ta for that ...

I bought my 98 model with genie extractors already installed, so i cant say whether or not they made a difference, but i did get a 2.5" system from the Y back..... Awesome difference!!!!! And a wicked note to boot!! lol
I was extremely suprised with the results. Next step will be a chip i think lol..... fundage depending.....

Cheers,

Brenton

Originally Posted by BigJon

I think you will find that Discovery Series Is were imported and complied as something other than passenger vehicles, therefore didn't have to meet such strict emission standards as normal sedans did.

I believe the same thing applies to Classic Range Rovers.

SPOT ON

Only Tuesday this week, I picked up my RRC with a newly installed set of extractors and full exhaust system.
Contrary to many comments, a lot more torque and a lot more 'up and go' is very noticeable, not to mention a bit more noise from the rear
Also, must say that I have noticed the under bonnet temperature is less than it used to be, and it runs a lot smoother and quieter.
Love the way it drives now.

Evo

Had plenty of V8 Rangies and the odd D1 with and without extractors and to me it's made **** all difference, save your money for other gear you want to fit to your Disco

Still you can't beat a good exhaust system on a V8, you going to spend the money on therunning it you be able to enjoy the sound that it produces

Trav

ok so not much differance with a 3.9, what about if a 4.6, balanced and cam have been put under the 3.9 heads and injection

still running the standard exhaust and it feels as though the engine is suffercating when it has to work hard, it just dosn't have the go that it should