Exhausts manifolds on 4.6

JSF55 · Post by **JSF55** » Sat Sep 26, 2009 12:44 pm

Would a pair of 4.6 exhaust manifolds, the ones with the flexi bit, offer any increase in performance over a pair of SD1 manifolds?

RoverP6B · Post by **RoverP6B** » Sun Sep 27, 2009 9:38 am

The only way to really know would be to dyno the vehicle (or engine) with say the SD1 manifolds and then compare the result with a repeat performance except this time running the 4.6 manifolds.

What capacity engine are you using the SD1 manifolds on? Are you running an automatic or manual transmission?

Ron.

JSF55 · Post by **JSF55** » Sun Sep 27, 2009 1:22 pm

It'a only a 3.5 at the mo, but if i do the exhaust through the winter months, i need to split at the rear to be able to mount a towbar, but i thought if there was any gain, i would change the manifolds and add to that, cheers john

RoverP6B · Post by **RoverP6B** » Sun Sep 27, 2009 10:24 pm

Do your SD1 manifolds have a single outlet or are they dual outlet manifolds?

The single outlets on the P6 manifolds have an internal diameter of 39mm, and the same applies to the dual outlets on the 3.5 litre Range Rover manifolds, each is 39mm.

The 4.6 manifolds have a single outlet with a diameter of 52mm.

Ron.

SuperV8 · Post by **SuperV8** » Mon Sep 28, 2009 11:38 am

I have some 4.6 exhaust manifolds going spare.

PM me if your interested.

Tom.

JSF55 · Post by **JSF55** » Mon Sep 28, 2009 12:42 pm

There the dual outlet type, i think there good for 200 bhp ? which is where i am at the mo with the engine, i was thinkingmost 4.6 produce more than that ?

JSF55 · Post by **JSF55** » Mon Sep 28, 2009 12:43 pm

SuperV8 wrote:I have some 4.6 exhaust manifolds going spare.

PM me if your interested.

Tom.

PM sent

RoverP6B · Post by **RoverP6B** » Mon Sep 28, 2009 12:53 pm

The TWR Rover Vitesse that was so successful during the 1980s in both the British and European Touring car championships not to mention winning its class at the Bathurst 1000 in Australia was fitted with.....factory cast iron twin outlet exhaust manifolds.

They may well have been smoothed internally to improve flow, but those 3.5 litre Rover V8 engines pushed out 300 plus horsepower and those cast manifolds were good enough for that.

If I had a choice between the two, I'd go with the ones you already have.

Ron.

ChrisJC · Post by **ChrisJC** » Mon Sep 28, 2009 1:00 pm

I think the 4.6 Range Rover was 225BHP.

I suspect the tubular manifolds were intended to save weight as much as anything.

Chris.

Robrover · Post by **Robrover** » Tue Sep 29, 2009 6:14 am

The 3.9 EFI Disco cast iron manifolds are reputedly quite a good design, and easy to find.